| 1. |
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| 2. |
- Alvehus, Malin, et al.
(författare)
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Metabolic adaptations in skeletal muscle, adipose tissue, and whole-body oxidative capacity in response to resistance training
- 2014
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Ingår i: European Journal of Applied Physiology. - : Springer Science and Business Media LLC. - 1439-6319 .- 1439-6327. ; 114:7, s. 1463-1471
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Tidskriftsartikel (refereegranskat)abstract
- The effects of resistance training on mitochondrial biogenesis and oxidative capacity in skeletal muscle are not fully characterized, and even less is known about alterations in adipose tissue. We aimed to investigate adaptations in oxidative metabolism in skeletal muscle and adipose tissue after 8 weeks of heavy resistance training in apparently healthy young men. Expression of genes linked to oxidative metabolism in the skeletal muscle and adipose tissue was assessed before and after the training program. Body composition, peak oxygen uptake (VO2 peak), fat oxidation, activity of mitochondrial enzyme in muscle, and serum adiponectin levels were also determined before and after resistance training. In muscle, the expression of the genes AdipoR1 and COX4 increased after resistance training (9 and 13 %, respectively), whereas the expression levels of the genes PGC-1 alpha, SIRT1, TFAM, CPT1b, and FNDC5 did not change. In adipose tissue, the expression of the genes SIRT1 and CPT1b decreased after training (20 and 23 %, respectively). There was an increase in lean mass (from 59.7 +/- A 6.1 to 61.9 +/- A 6.2 kg), VO2 peak (from 49.7 +/- A 5.5 to 56.3 +/- A 5.0 ml/kg/min), and fat oxidation (from 6.8 +/- A 2.1 to 9.1 +/- A 2.7 mg/kg fat-free mass/min) after training, whereas serum adiponectin levels decreased significantly and enzyme activity of citrate synthase and 3-hydroxyacyl-CoA dehydrogenase did not change. Despite significant increases in VO2 peak, fat oxidation, and lean mass following resistance training, the total effect on gene expression and enzyme activity linked to oxidative metabolism was moderate.
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| 3. |
- Andersson, Erik, et al.
(författare)
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Analysis of sprint cross-country skiing using a differential global navigation satellite system
- 2010
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Ingår i: European Journal of Applied Physiology. - : Springer Science and Business Media LLC. - 1439-6319 .- 1439-6327. ; 110:3, s. 585-595
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Tidskriftsartikel (refereegranskat)abstract
- The purpose was to examine skiing velocities, gear choice (G2-7) and cycle rates during a skating sprint time trial (STT) and their relationships to performance, as well as to examine relationships between aerobic power, body composition and maximal skiing velocity versus STT performance. Nine male elite cross-country skiers performed three tests on snow: (1) Maximum velocity test (Vmax) performed using G3 skating, (2) Vmax test performed using double poling (DP) technique and (3) a STT over 1,425 m. Additional measurements of VO2max during roller skiing and body composition using iDXA were made. Differential global navigation satellite system data were used for position and velocity and synchronized with video during STT. The STT encompassed a large velocity range (2.9-12.9 m s-1) and multiple transitions (21-34) between skiing gears. Skiing velocity in the uphill sections was related to gear selection between G2 and G3. STT performance was most strongly correlated to uphill time (r = 0.92, P < 0.05), the percentage use of G2 (r = -0.72, P < 0.05), and DP Vmax (r = -0.71, P < 0.05). The velocity decrease in the uphills from lap 1 to lap 2 was correlated with VO2max (r = -0.78, P < 0.05). Vmax in DP and G3 were related to percent of racing time using G3. In conclusion, the sprint skiing performance was mainly related to uphill performance, greater use of the G3 technique, and higher DP and G3 maximum velocities. Additionally, VO2max was related to the ability to maintain racing velocity in the uphills and lean body mass was related to starting velocity and DP maximal speed.
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| 4. |
- Beaven, Christopher, 1977-
(författare)
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Ultradian rhythmicity and induced changes in salivary testosterone
- 2010
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Ingår i: European Journal of Applied Physiology. - 1439-6319 .- 1439-6327. ; 10:2, s. 405-413
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Tidskriftsartikel (refereegranskat)abstract
- Testosterone and cortisol respond to exercise stimuli and modulate adaptation.Episodic basal secretion of these hormones may modify the responsiveness of these hormones.We sought to identify episodic steroid secretion via frequent salivary sampling and investigate any interaction between ultradian rhythmicity and induced changes in testosterone.Salivary testosterone and cortisol concentrations of seven males (age 20-40 y) were measured every 10 min between 0800-1600 h on three consecutive days.On either the second or third day, three interventions designed to elicit a hormonal response were randomly assigned: sprint exercise (two 30-s maximal efforts on a cycle ergometer); boxing (two 30-s maximal punching efforts); and a violent video game (10 min of player-versus-player combat).On the other days subjects were inactive.Testosterone data on non-intervention days suggested pulsatile secretion with a pulse interval of 47 ± 9 min (mean ± SD).The sprint intervention substantially affected hormones: it elicited a small transient elevation in testosterone (by a factor of 1.21; factor 90% confidence limits x/1.21) 10 min after exercise, and a moderate elevation in cortisol peaking 50 min post-exercise (factor 2.3; x/2.6).The testosterone response correlated with the change in testosterone concentration in the 10 min prior to the sprint (r=0.78; 90%CL 0.22 to 0.95) and with a measure of randomness in testosterone fluctuations (r=0.83; 0.35 to 0.96).Thus, the salivary testosterone response to exercise may be dependent on the underlying ultradian rhythm and aspects of its regulation.This interaction may have important implications for adaptation to exercise.
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| 5. |
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| 6. |
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| 7. |
- Borgenvik, Marcus, et al.
(författare)
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Alterations in amino acid concentrations in the plasma and muscle in human subjects during 24 h of simulated adventure racing
- 2012
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Ingår i: European Journal of Applied Physiology. - : Springer Science and Business Media LLC. - 1439-6319 .- 1439-6327. ; 112, s. 3679-3688
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Tidskriftsartikel (refereegranskat)abstract
- This investigation was designed to evaluate changes in plasma and muscle levels of free amino acids during an ultra-endurance exercise and following recovery. Nine male ultra-endurance trained athletes participated in a 24-h standardized endurance trial with controlled energy intake. The participants performed 12 sessions of running, kayaking and cycling (4 x each discipline). Blood samples were collected before, during and after exercise, as well as after 28 h of recovery. Muscle biopsies were taken 1 week before the test and after exercise, as well as after 28 h of recovery. During the 24-h exercise, plasma levels of branched-chain (BCAA), essential amino acids (EAA) and glutamine fell 13%, 14% and 19% (P<0.05) respectively, whereas their concentrations in muscle were unaltered. Simultaneously, tyrosine and phenylalanine levels rose 38% and 50% (P<0.05) in the plasma and 66% and 46% (P<0.05) in muscle, respectively. After the 24-h exercise, plasma levels of BCAA were positively correlated with muscle levels of glycogen (r2=0.73, P<0.05), as was the combined concentrations of muscle tyrosine and phenylalanine with plasma creatine kinase (r2=0.55, P<0.05). Following 28-h of recovery, plasma and muscle levels of amino acids had either returned to their initial levels or were elevated. In conclusion, ultra-endurance exercise caused significant changes elevations in plasma and muscle levels of tyrosine and phenylalanine, which suggest an increase in net muscle protein breakdown during exercise. There was a reduction in plasma concentrations of EAA and glutamine during exercise, whereas no changes were detected in their muscle concentration after exercise.
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| 8. |
- Carlsson, Lars, et al.
(författare)
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Enhanced systolic myocardial function in elite endurance athletes during combined arm-and-leg exercise
- 2011
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Ingår i: European Journal of Applied Physiology. - : Springer Science and Business Media LLC. - 1439-6319 .- 1439-6327. ; 111:6, s. 905-913
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Tidskriftsartikel (refereegranskat)abstract
- The aim here was to employ color tissue velocity imaging (TVI), to test the hypothesis that highly trained endurance athletes exhibit enhanced systolic function of the left ventricular (LV) myocardium both at rest and during combined arm-and-leg exercise in comparison with untrained subjects. For each of the ten elite male (EG) and ten matched control participants (CG), LV dimensions and systolic function were assessed at rest using echocardiography. Subsequently, these subjects exercised continuously on a combined arm-and-leg cycle ergometer for 3 min each at 50, 60, 70, 80, 90 and 100% of VO2max. Oxygen uptake, heart rate, systolic blood pressure (SBP) and peak contraction systolic velocities of the LV myocardium (PSV) were recorded in the end of each level. At rest, the trained and untrained groups differed with respect to LV dimensions, but not systolic function. At 60–100% VO2max, the EG group demonstrated both higher PSV and SBP. The observation that the EG athletes had higher PSV than CG during exercise at 60–100% VO2max, but not at rest or at 50% of VO2max, suggested an enhanced systolic capacity. This improvement is likely to be due to an enhanced inotropic contractility, which only becomes apparent during exercise.
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| 9. |
- Carlsson, Magnus, et al.
(författare)
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Oxygen uptake at different intensities and sub-techniques predicts sprint performance in elite male cross-country skiers
- 2014
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Ingår i: European Journal of Applied Physiology. - : Springer. - 1439-6319 .- 1439-6327. ; 114:12, s. 2587-2595
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Tidskriftsartikel (refereegranskat)abstract
- PURPOSE: To investigate the relationship between sprint-prologue performance (using the classical technique) and the oxygen uptake at the lactate threshold (V̇O2obla), maximal oxygen uptake (V̇O2max), and mean oxygen uptake during double poling (V̇O2dp).METHODS: Eight elite male cross-country skiers [age 24.8 ± 4.8 years, (mean ± SD)] completed two treadmill roller-skiing tests using the diagonal-stride technique and a 60 s double-poling test on a ski-ergometer to determine their V̇O2obla, V̇O2max, and V̇O2dp. Performance data were generated from a 1.25 km sprint prologue. Power-function modelling was used to predict the skiers' race speeds based on the oxygen-uptake variables and body mass.RESULTS: There were correlations between the race speed and the absolute expression of the V̇O2obla (r = 0.79, P = 0.021), V̇O2max (r = 0.86, P = 0.0069), and V̇O2dp (r = 0.94, P = 0.00062). The following power-function models were established for race-speed prediction: 1.09 · V̇O2obla(0.21), 1.05 · V̇O2max(0.21), and 1.19 · V̇O2dp(0.20); these models explained 60 % (P = 0.024), 73 % (P = 0.0073), and 87 % (P = 0.00073), respectively, of the variance in the race speed. However, body mass did not contribute to any of the models (P = 0.97, 0.88, and 0.21, respectively).CONCLUSIONS: Oxygen uptake at different intensities and sub-techniques is an indicator of elite male sprint-prologue performance. The absolute expression of the investigated oxygen-uptake variables should be used when evaluating elite male sprint-prologue performances; if skiers oxygen uptake differs by 1 %, their performances will likely differ by 0.2 % in favour of the skier with higher oxygen uptake.
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| 10. |
- Crenshaw, Albert G., et al.
(författare)
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Reliability of near-infrared spectroscopy for measuring forearm and shoulder oxygenation in healthy males and females
- 2012
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Ingår i: European Journal of Applied Physiology. - : Springer. - 1439-6319 .- 1439-6327. ; 112:7, s. 2703-2715
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Tidskriftsartikel (refereegranskat)abstract
- This study determined the day-to-day reliability of NIRS-derived oxygenation responses (a dagger StO(2)%) for isometric contractions and for cuff occlusion. Twenty-four subjects (12 males and 12 females) were tested for 2 days (4-6 days interval). Variables generated were: (1) a dagger StO(2)% for isometric contractions (10, 30, 50 and 70% MVC) for descending trapezius (TD) and extensor carpi radialis (ECR) muscles; (2) slope changes in total haemoglobin (HbTslope) and deoxyhaemoglobin (HHbslope) for the ECR using upper arm venous (VO, 50 mmHg) and arterial occlusion (AO, 250 mmHg); (3) recovery slopes (Rslope) for oxygen saturation (StO(2)) following isometric contractions and AO. For each variable, an intraclass correlation (ICC) was calculated to assess the ability to differentiate between subjects, and limits of agreement (LOA) were computed to assess day-to-day consistency of the measurement. ICCs for Delta StO(2)% were lowest at 10% MVC for both ECR (0.58) and TD (0.55), and highest at 30% MVC for ECR (0.95) and at 70% MVC for TD (0.79). For both muscles, LOA for Delta StO(2)% was lowest at 10% and highest at 50 and 70% MVC. ICC for HbTslope was 0.17. For HHbslope ICC was higher for AO (0.83) than for VO (0.73), and LOA was lower for AO. For the ECR Rslope ICCs ranged from 0.88 to 0.90 for contraction, but was lower for AO (0.33); LOA was lowest at 70% MVC. For trapezius Rslope ICCs ranged from 0.63 to 0.73 and LOA was lowest at 30% MVC. For this study, establishing reliability data for the ECR and TD and including variables commonly reported are expected to have meaning for future NIRS studies of work-related upper-extremity pain as well as for other NIRS research and clinical applications.
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| 11. |
- Debevec, Tadej, et al.
(författare)
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Acute short-term hyperoxia followed by mild hypoxia does not increase EPO production : resolving the "normobaric oxygen paradox''
- 2012
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Ingår i: European Journal of Applied Physiology. - : Springer Science and Business Media LLC. - 1439-6319 .- 1439-6327. ; 112:3, s. 1059-1065
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Tidskriftsartikel (refereegranskat)abstract
- Recent findings suggest that besides renal tissue hypoxia, relative decrements in tissue oxygenation, using a transition of the breathing mixture from hyperoxic to normoxic, can also stimulate erythropoietin (EPO) production. To further clarify the importance of the relative change in tissue oxygenation on plasma EPO concentration [EPO], we investigated the effect of a consecutive hyperoxic and hypoxic breathing intervention. Eighteen healthy male subjects were assigned to either IHH (N = 10) or CON (N = 8) group. The IHH group breathed pure oxygen (F(i)O(2) ~ 1.0) for 1 h, followed by a 1-h period of breathing a hypoxic gas mixture (F(i)O(2) ~ 0.15). The CON group breathed a normoxic gas mixture (F(i)O(2) ~ 0.21) for the same duration (2 h). Blood samples were taken just before, after 60 min, and immediately after the 2-h exposure period. Thereafter, samples were taken at 3, 5, 8, 24, 32, and 48 h after the exposure. During the breathing interventions, subjects remained in supine position. There were significant increases in absolute [EPO] within groups at 8 and 32 h in the CON and at 32 h only in the IHH group. No significant differences in absolute [EPO] were observed between groups following the intervention. Relative (∆[EPO]) levels were significantly lower in the IHH than in the CON group, 5 and 8 h following exposure. The tested protocol of consecutive hyperoxic-hypoxic gas mixture breathing did not induce [EPO] synthesis stimulation. Moreover, the transient attenuation in ∆[EPO] in the IHH group was most likely due to a hyperoxic suppression. Hence, our findings provide further evidence against the "normobaric O(2) paradox" theory.
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| 12. |
- Debevec, Tadej, et al.
(författare)
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Separate and combined effects of 21-day bed rest and hypoxic confinement on body composition
- 2014
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Ingår i: European Journal of Applied Physiology. - : Springer Science and Business Media LLC. - 1439-6319 .- 1439-6327. ; 114:11, s. 2411-2425
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Tidskriftsartikel (refereegranskat)abstract
- This study tested the hypothesis that hypoxia exacerbates reductions in body mass observed during unloading. To discern the separate and combined effects of simulated microgravity and hypoxia, 11 healthy males underwent three 21-day campaigns in a counterbalanced fashion: (1) normoxic bed rest (NBR; FiO2 = 0.209; PiO2 = 133.1 +/- A 0.3); (2) hypoxic ambulatory confinement (HAMB; FiO2 = 0.141 +/- A 0.004; PiO2 = 90.0 +/- A 0.4; similar to 4,000 m); and (3) hypoxic bed rest (HBR; FiO2 = 0.141 +/- A 0.004; PiO2 = 90.0 +/- A 0.4). The same dietary menu was applied in all campaigns. Targeted energy intakes were estimated individually using the Harris-Benedict equation taking into account whether the subjects were bedridden or ambulatory. Body mass and water balance were assessed throughout the campaigns. Whole body and regional body composition was determined before and after the campaigns using dual-energy X-ray absorptiometry. Before and during the campaigns, indirect calorimetry and visual analogue scores were employed to assess the resting energy expenditure (REE) and perceived appetite sensations, respectively. Energy intakes were lower than targeted in all campaigns (NBR: -5 %; HAMB: -14 %; HBR: -6 %; P < 0.01). Body mass significantly decreased following all campaigns (NBR: -3 %; HAMB: -4 %; HBR: -5 %; P < 0.01). While fat mass was not significantly altered, the whole body fat free mass was reduced (NBR: -4 %; HAMB: -5 %; HBR: -5 %; P < 0.01), secondary to lower limb fat-free mass reduction. Water balance was comparable between the campaigns. No changes were observed in REE and perceived appetite. Exposure to simulated altitude of similar to 4,000 m does not seem to worsen the whole body mass and fat-free mass reductions or alter resting energy expenditure and appetite during a 21-day simulated microgravity.
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| 13. |
- Eiken, Ola, et al.
(författare)
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Blood pressure regulation V : in vivo mechanical properties of precapillary vessels as affected by long-term pressure loading and unloading
- 2014
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Ingår i: European Journal of Applied Physiology. - : Springer Science and Business Media LLC. - 1439-6319 .- 1439-6327. ; 114:3, s. 499-509
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Forskningsöversikt (refereegranskat)abstract
- Recent studies are reviewed, concerning the in vivo wall stiffness of arteries and arterioles in healthy humans, and how these properties adapt to iterative increments or sustained reductions in local intravascular pressure. A novel technique was used, by which arterial and arteriolar stiffness were determined as changes in arterial diameter and flow, respectively, during graded increments in distending pressure in the blood vessels of an arm or a leg. Pressure-induced increases in diameter and flow were smaller in the lower leg than in the arm, indicating greater stiffness in the arteries/arterioles of the leg. A 5-wk period of intermittent intravascular pressure elevations in one arm reduced pressure distension and pressure-induced flow in the brachial artery by about 50%. Conversely, prolonged reduction of arterial/arteriolar pressure in the lower body by 5 wks of sustained horizontal bedrest, induced three-fold increases of the pressure-distension and pressure-flow responses in a tibial artery. Thus, the wall stiffness of arteries and arterioles are plastic properties that readily adapt to changes in the prevailing local intravascular pressure. The discussion concerns mechanisms underlying changes in local arterial/arteriolar stiffness as well as whether stiffness is altered by changes in myogenic tone and/or wall structure. As regards implications, regulation of local arterial/arteriolar stiffness may facilitate control of arterial pressure in erect posture and conditions of exaggerated intravascular pressure gradients. That increased intravascular pressure leads to increased arteriolar wall stiffness also supports the notion that local pressure loading may constitute a prime mover in the development of vascular changes in hypertension.
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| 14. |
- Eiken, Ola, et al.
(författare)
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G tolerance vis-à-vis pressure-distension and pressure-flow relationships of leg arteries
- 2012
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Ingår i: European Journal of Applied Physiology. - : Springer Science and Business Media LLC. - 1439-6319 .- 1439-6327. ; 112:10, s. 3619-3627
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Tidskriftsartikel (refereegranskat)abstract
- During increased gravitoinertial (G) load in the head-to-foot direction, pressures in dependent vascular beds are commonly raised to levels capable of distending precapillary vessels, which, in turn, may reduce arterial pressure, and hence compromise the capacity to withstand G load (G tolerance). We hypothesized that distensibility in precapillary leg vessels would be lower in a group of subjects possessing high G tolerance (H; n = 7; relaxed G tolerance = 6.6 ± 0.8 G) than in a group with low G tolerance (L; n = 8; G tolerance = 3.9 ± 0.3 G). The groups were matched with regard to gender, age, weight, height, and resting arterial pressure. Arterial pressure-distension and pressure-flow experiments were performed with the subject supine in a pressure chamber with a lower leg protruding to the outside. Increased intravascular pressure in the blood vessels of the outside leg was accomplished by stepwise increasing chamber pressure to 240 mmHg. Diameter and flow in the posterior tibial artery were measured by ultrasonographic/Doppler techniques. Pressure-induced increments in arterial diameter and flow were more pronounced (p < 0.03) in the L (14.1 ± 4.2% and 32 ± 21 ml/min respectively) than in the H (1.7 ± 5.0% and 1.6 ± 25 ml/min) group, and the pressure thresholds at which these increments commenced were lower (by 52 and 48 mmHg, respectively) in the L than in the H group (p < 0.04). Negative correlations were observed between G tolerance and the increments in diameter and flow (p < 0.02). Thus, the wall stiffness of precapillary leg vessels is greater in individuals with high relaxed G tolerance; whether a causal relationship exists remains to be established.
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| 15. |
- Elcadi, Guilherme H., 1966-, et al.
(författare)
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Shoulder and forearm oxygenation and myoelectric activity in patients with work related muscle pain and healthy subjects
- 2013
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Ingår i: European Journal of Applied Physiology. - New York : Springer. - 1439-6319 .- 1439-6327. ; 113:5, s. 1103-1115
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Tidskriftsartikel (refereegranskat)abstract
- We tested hypotheses of (i) reduced oxygen usage, oxygen recovery, blood flow and oxygen consumption; and (ii) increased muscle activity for patients diagnosed with work related muscle pain in comparison to healthy controls. Oxygenation was measured with near infrared spectroscopy (NIRS), and muscle activity with EMG for the extensor carpi radialis (ECR) and trapezius descendens (TD) muscles. Eighteen patients with diffuse neck-shoulder-arm pain and seventeen controls (matched in age and sex) were equipped with NIRS and EMG probes. After determining an individual’s maximum voluntary contraction (MVC) force, short term (20 sec) isometric contractions for the ECR and TD of 10%, 30%, 50% and 70% MVC generated ∆StO2% and StO2% recovery (Rslope) from NIRS, and RMS%max from EMG signals. In addition, upper arm venous (VO) and arterial (AO) occlusions generated slopes of total hemoglobin (HbTslope) and deoxyhemoglobin (HHbslope) for the resting ECR as surrogates of blood flow and oxygen consumption, respectively. Mixed Model analyses, t-tests, and Mann-Whitney test were used to assess differences between groups. There was no significant difference in MVC between groups for either muscle. Also, ∆StO2%, Rslope for either muscle, and ECR-HbTslope were not different between groups, thus our hypotheses of reduced oxygen use, recovery, and blood flow for patients were not confirmed. However, patients had a significantly lower ECR-HHbslope confirming our hypothesis of reduced consumption. Further, there was no difference in RMS%max during contractions meaning that the hypothesis of increased activity for patients was not confirmed. When taking into account the number of NIRS variables studied, differences we found between our patient group and healthy controls (i.e. in forearm oxygen consumption and shoulder oxygen saturation level) may be considered modest. Overall our findings may have been impacted by the fact that our patients and controls were similar in muscle strength, which is in contrast to previous studies.
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| 16. |
- Elcadi, Guilherme H., 1966-, et al.
(författare)
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The relationship between oxygenation and myoelectric activity in the forearm and shoulder muscles of males and females
- 2011
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Ingår i: European Journal of Applied Physiology. - : Springer. - 1439-6319 .- 1439-6327. ; 111, s. 647-658
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Tidskriftsartikel (refereegranskat)abstract
- The aim was to investigate the relationship between oxygen saturation (StO(2)%) measured with near-infrared spectroscopy (NIRS) and myoelectric activity (root mean square, RMS) for the extensor carpi radialis (ECR) and trapezius muscles. In addition, gender differences were examined for submaximal (10-70% MVC) and sustained (10% MVC for 5 min) isometric contractions. Thirteen males and 15 females participated. Changes in StO(2)% (a dagger StO(2)%) and RMS, expressed as percentages of maximum, were calculated for each submaximal contraction. A good correlation between a dagger StO(2)% and RMS was seen for the ECR (r = -0.53) and a moderate correlation seen for the trapezius muscle (r = -0.44). The ANOVA showed a significant decrease in ECR-a dagger StO(2)% over force with females demonstrating a tendency for larger changes than males. ECR-RMS increased over force with no impact of gender. For the trapezius, a dagger StO(2)% decreased over force but was not gender dependent. Trapezius-RMS increased over force with females demonstrating a tendency for greater change than males. For the sustained contraction, ECR-StO(2)% changed over time but was not gender dependent. ECR-RMS increased over time with females showing a greater response than males. Trapezius-StO(2)% changed over time and differed between genders, i.e., males increased while females decreased. RMS increased over time similarly for both genders. In conclusion, our data show that the ECR and trapezius aerobic demands during isometric contractions are negatively correlated to electromyography (EMG) RMS. The present study also suggests some gender specificity for forearm and shoulder myoelectric activity and oxygenation for submaximal and sustained contractions.
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| 17. |
- Elmer, Steven
(författare)
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Eccentric arm cycling: physiological responses and potential applications for clinical andathletic populations
- 2013
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Ingår i: Journal of applied physiology. - : Springer Science and Business Media LLC. - 8750-7587 .- 1522-1601 .- 1439-6319 .- 1439-6327. ; 113:10, s. 2541-2552
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Tidskriftsartikel (refereegranskat)abstract
- INTRODUCTION:Eccentric leg cycling has served as an important research model for investigating multi-joint eccentric actions and as an effective rehabilitation and training modality for improving locomotor muscle function (e.g., quadriceps size, strength, mobility). While there are more than 30 reports documenting physiological responses to eccentric leg cycling, physiological responses to eccentric arm cycling (ECarm) have not been clearly established.PURPOSE:We tested the hypothesis that ECarm could be performed with lower levels of metabolic and cardiorespiratory demand and perceived exertion compared to traditional concentric arm cycling (CCarm).METHODS:Eight individuals performed ECarm and CCarm at 40, 80, and 120 W (~9 min, 60 rpm) while expired gases and muscle activation patterns were recorded.RESULTS:Oxygen consumption, cardiac output, heart rate, and ventilation were 25-50 % lower during ECarm compared to CCarm (all P < 0.05). Further, only low-to-moderate levels of whole-body and arm-specific perceived exertion were required to perform ECarm which was not the case for CCarm (8-12 vs. 9-16 Borg values, both P < 0.05). Differences in oxygen consumption and total upper body muscle activity between ECarm and CCarm were strongly related (r (2) = 0.75, P < 0.01). Coordination of ECarm involved triceps brachii, deltoideus anterior, and external oblique muscles, whereas CCarm involved all of these muscles along with contributions from biceps brachii, deltoideus posterior, and trapezius transversalis.CONCLUSIONS:These results highlight the high-force, low-cost nature of multi-joint eccentric actions and extend the application of eccentric cycling to the upper body. ECarm may be useful for exercising elbow, trunk, and shoulder musculature while minimizing metabolic and cardiorespiratory strain and perceived exertion.
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| 18. |
- Elmer, Steven J, et al.
(författare)
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Fatigue is specific to working muscles : no cross-over during single-leg cycling in trained cyclists
- 2013
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Ingår i: European Journal of Applied Physiology. - : Springer Science and Business Media LLC. - 1439-6319 .- 1439-6327. ; 113:2, s. 479-488
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Tidskriftsartikel (refereegranskat)abstract
- Fatigue induced via a maximal isometric contraction of a single limb muscle group can evoke a "cross-over" of fatigue that reduces voluntary muscle activation and maximum isometric force in the rested contralateral homologous muscle group. We asked whether a cross-over of fatigue also occurs when fatigue is induced via high-intensity endurance exercise involving a substantial muscle mass. Specifically, we used high-intensity single-leg cycling to induce fatigue and evaluated associated effects on maximum cycling power (P max) in the fatigued ipsilateral leg (FATleg) as well as the rested contralateral leg (RESTleg). On separate days, 12 trained cyclists performed right leg P max trials before and again 30 s, 3, 5, and 10 min after a cycling time trial (TT, 10 min) performed either with their right or left leg. Fatigue was estimated by comparing exercise-induced changes in P max and maximum handgrip isometric force (F max). Mean power produced during the right and left leg TTs did not differ (203 ± 8 vs. 199 ± 8 W). Compared to pre-TT, FATleg P max was reduced by 22 ± 3 % at 30 s post-TT and remained reduced by 9 ± 2 % at 5 min post-TT (both P < 0.05). Despite considerable power loss in the FATleg, post-TT RESTleg P max (596–603 W) did not differ from pre-TT values (596 ± 35 W). There were no alterations in handgrip F max (529–547 N). Our data suggest that any potential cross-over of fatigue, if present at all, was not sufficient to measurably compromise RESTleg P max in trained cyclists. These results along with the lack of changes in handgrip F max indicate that impairments in maximal voluntary neuromuscular function were specific to working muscles.
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| 19. |
- Fernandez-Gonzalo, R., et al.
(författare)
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Muscle damage responses and adaptations to eccentric-overload resistance exercise in men and women
- 2014
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Ingår i: European Journal of Applied Physiology. - : Springer Science and Business Media LLC. - 1439-6319 .- 1439-6327. ; 114:5, s. 1075-1084
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Tidskriftsartikel (refereegranskat)abstract
- Purpose: This study assessed markers of muscle damage and training adaptations to eccentric-overload flywheel resistance exercise (RE) in men and women. Methods: Dynamic strength (1 RM), jump performance, maximal power at different percentages of 1 RM, and muscle mass in three different portions of the thigh were assessed in 16 men and 16 women before and after 6 weeks (15 sessions) of flywheel supine squat RE training. Plasma creatine kinase (CK) and lactate dehydrogenase (LDH) concentrations were measured before, 24, 48 and 72 h after the first and the last training session. Results: After training, increases in 1 RM were somewhat greater (interaction P < 0.001) in men (25 %) than in women (20 %). Squat and drop jump height and power performance at 50, 60, 70 and 80 % of 1 RM increased after training in both sexes (P < 0.05). Power improvement at 80 % of 1 RM was greater (interaction P < 0.02) in men than women. Muscle mass increased ~5 % in both groups (P < 0.05). CK increased in men after the first training session (P < 0.001), whereas the response in women was unaltered. In both sexes, LDH concentration was greater after the first training session compared with basal values (P < 0.05). After the last session, CK and LDH remained at baseline in both groups. Conclusions: These results suggest that although improvements in maximal strength and power at high loads may be slightly greater for men, eccentric-overload RE training induces comparable and favorable gains in strength, power, and muscle mass in both men and women. Equally important, it appears muscle damage does not interfere with the adaptations triggered by this training paradigm. © 2014 Springer-Verlag Berlin Heidelberg.
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| 20. |
- Flueck, M, et al.
(författare)
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Linking genes with exercise: where is the cut-off?
- 2010
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Ingår i: European journal of applied physiology. - : Springer Science and Business Media LLC. - 1439-6327 .- 1439-6319. ; 110:6, s. 1095-1098
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
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| 21. |
- Gago, Paulo, et al.
(författare)
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Post activation potentiation can be induced without impairing tendon stiffness.
- 2014
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Ingår i: European Journal of Applied Physiology. - : Springer Science and Business Media LLC. - 1439-6319 .- 1439-6327. ; 114:11, s. 2299-2308
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Tidskriftsartikel (refereegranskat)abstract
- PURPOSE: This study aimed to investigate conditioning effects from a single 6-s plantar flexion maximal voluntary isometric contraction (MVIC) on Achilles tendon stiffness (ATS) and twitch properties of the triceps surae in athletes.METHODS: Peak twitch (PT), rate of torque development (RTD), rising time (RT10-90%) and half relaxation time (HRT) were measured from supramaximal twitches evoked in the plantar flexors of 10 highly trained athletes. Twitches were evoked before and at seven occasions during 10 min of recovery after a 6-s MVIC. In a second session, but at identical post-conditioning time points, ATS was measured at 30 and 50 % of MVIC (ATS30% and ATS50%) using an ultrasonography-based method.RESULTS: The magnitude and duration of the conditioning MVIC on muscle contractile properties were in accordance with previous literature on post activation potentiation (PAP), i.e., high potentiation immediately after MVIC, with significant PAP for up to 3 min after the MVIC. While PT and RTD were significantly enhanced (by 60.6 ± 19.3 and 90.1 ± 22.5 %, respectively) and RT10-90% and HRT were reduced (by 10.1 ± 7.7 and 18.7 ± 5.6 %, respectively) after conditioning, ATS remained unaffected.CONCLUSIONS: Previous studies have suggested that changes in stiffness after conditioning may interfere with the enhancements in twitch contractile properties. The present study, however, provided some evidence that twitch enhancements after a standard PAP can be induced without changes in ATS. This result may suggest that athletes can use this protocol to enhance muscle contractile properties without performance deficits due to changes in ATS.
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| 22. |
- Gao, Chuansi, et al.
(författare)
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Cooling vests with phase change materials: the effects of melting temperature on heat strain alleviation in an extremely hot environment
- 2011
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Ingår i: European Journal of Applied Physiology. - : Springer Science and Business Media LLC. - 1439-6327 .- 1439-6319. ; 111:6, s. 1207-1216
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Tidskriftsartikel (refereegranskat)abstract
- A previous study by the authors using a heated thermal manikin showed that the cooling rates of phase change material (PCM) are dependent on temperature gradient, mass, and covering area. The objective of this study was to investigate if the cooling effects of the temperature gradient observed on a thermal manikin could be validated on human subjects in extreme heat. The subjects wore cooling vests with PCMs at two melting temperatures (24 and 28°C) and fire-fighting clothing and equipment, thus forming three test groups (vest24, vest28 and control group without the vest). They walked on a treadmill at a speed of 5 km/h in a climatic chamber (air temperature = 55°C, relative humidity = 30%, vapour pressure = 4,725 Pa, and air velocity = 0.4 m/s). The results showed that the PCM vest with a lower melting temperature (24°C) has a stronger cooling effect on the torso and mean skin temperatures than that with a higher melting temperature (28°C). Both PCM vests mitigate peak core temperature increase during the resting recovery period. The two PCM vests tested, however, had no significant effect on the alleviation of core temperature increase during exercise in the heat. To study the possibility of effective cooling of core temperature, cooling garments with PCMs at even lower melting temperatures (e.g. 15°C) and a larger covering area should be investigated.
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| 23. |
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| 24. |
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| 25. |
- Hadrévi, Jenny, 1977-, et al.
(författare)
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Comparative metabolomics of muscle interstitium fluid in human trapezius myalgia: an in vivo microdialysis study
- 2013
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Ingår i: European Journal of Applied Physiology. - : Springer Verlag (Germany). - 1439-6319 .- 1439-6327. ; 113:12, s. 2977-2989
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Tidskriftsartikel (refereegranskat)abstract
- The mechanisms behind trapezius myalgia are unclear. Many hypotheses have been presented suggesting an altered metabolism in the muscle. Here, muscle microdialysate from healthy and myalgic muscle is analysed using metabolomics. Metabolomics analyse a vast number of metabolites, enabling a comprehensive explorative screening of the cellular processes in the muscle. less thanbrgreater than less thanbrgreater thanMicrodialysate samples were obtained from the shoulder muscle of healthy and myalgic subjects that performed a work and stress test. Samples from the baseline period and from the recovery period were analysed using gas chromatography-mass spectrometry (GC-MS) together with multivariate analysis to detect differences in extracellular content of metabolites between groups. Systematic differences in metabolites between groups were identified using multivariate analysis and orthogonal partial least square discriminate analysis (OPLS-DA). A complementary Mann-Whitney U test of group difference in individual metabolites was also performed. less thanbrgreater than less thanbrgreater thanA large number of metabolites were detected and identified in this screening study. At baseline, no systematic differences between groups were observed according to the OPLS-DA. However, two metabolites, l-leucine and pyroglutamic acid, were significantly more abundant in the myalgic muscle compared to the healthy muscle. In the recovery period, systematic difference in metabolites between the groups was observed according to the OPLS-DA. The groups differed in amino acids, fatty acids and carbohydrates. Myristic acid and putrescine were significantly more abundant and beta-d-glucopyranose was significantly less abundant in the myalgic muscle. less thanbrgreater than less thanbrgreater thanThis study provides important information regarding the metabolite content, thereby presenting new clues regarding the pathophysiology of the myalgic muscle.
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| 26. |
- Hallman, David, 1979-, et al.
(författare)
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Effects of static contraction and cold stimulation on cardiovascular autonomic indices, trapezius blood flow and muscle activity in chronic neck-shoulder pain
- 2011
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Ingår i: European Journal of Applied Physiology. - : Springer Science and Business Media LLC. - 1439-6319 .- 1439-6327. ; 111:8, s. 1725-1735
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Tidskriftsartikel (refereegranskat)abstract
- The aim of the present study was to investigate reactions in trapezius muscle blood flow (MBF), muscle activity, heart rate variability (HRV) and systemic blood pressure (BP) to autonomic tests in subjects with chronic neck-shoulder pain and healthy controls. Changes in muscle activity and blood flow due to stress and unfavourable muscle loads are known underlying factors of work-related muscle pain. Aberration of the autonomic nervous system (ANS) is considered a possible mechanism. In the present study, participants (n = 23 Pain, n = 22 Control) performed autonomic tests which included a resting condition, static hand grip test (HGT) at 30% of maximal voluntary contraction, a cold pressor test (CPT) and a deep breathing test (DBT). HRV was analysed in time and frequency domains. MBF and muscle activity were recorded from the upper trapezius muscles using photoplethysmography and electromyography (EMG). The pain group showed reduced low frequency-HRV (LF) and SDNN during rest, as well as a blunted BP response and increased LF-HRV during HGT (a dagger systolic 22 mm Hg; a dagger LF(nu) 27%) compared with controls (a dagger systolic 27; a dagger LF(nu) 6%). Locally, the pain group had attenuated trapezius MBF in response to HGT (Pain 122% Control 140%) with elevated trapezius EMG following HGT and during CPT. In conclusion, only HGT showed differences between groups in systemic BP and HRV and alterations in local trapezius MBF and EMG in the pain group. Findings support the hypothesis of ANS involvement at systemic and local levels in chronic neck-shoulder pain.
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| 27. |
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| 28. |
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| 29. |
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| 30. |
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| 31. |
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| 32. |
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| 33. |
- Keramidas, Michail E., et al.
(författare)
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Enhancement of the finger cold-induced vasodilation response with exercise training
- 2010
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Ingår i: European Journal of Applied Physiology. - : Springer Science and Business Media LLC. - 1439-6319 .- 1439-6327. ; 109:1, s. 133-140
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Tidskriftsartikel (refereegranskat)abstract
- Cold-induced vasodilatation (CIVD) is a cyclical increase in finger temperature that has been suggested to provide cryoprotective function during cold exposures. Physical fitness has been suggested as a potential factor that could affect CIVD response, possibly via central (increased cardiac output, decreased sympathetic nerve activity) and/or peripheral (increased microcirculation) cardiovascular and neural adaptations to exercise training. Therefore, the purpose of this study was to investigate the effect of endurance exercise training on the CIVD response. Eighteen healthy males trained 1 h d(-1) on a cycle ergometer at 50% of peak power output, 5 days week(-1) for 4-weeks. Pre, Mid, Post, and 10 days after the cessation of training and on separate days, subjects performed an incremental exercise test to exhaustion ((V) over dotO(2peak)); and a 30-min hand immersion in 8 degrees C water to examine their CIVD response. The exercise-training regimen significantly increased (V) over dotO(2peak) (Pre: 46.0 +/- 5.9, Mid: 52.5 +/- 5.7, Post: 52.1 +/- 6.2, After: 52.6 +/- 7.6 ml kg(-1) min-1; P < 0.001). There was a significant increase in average finger skin temperature (Pre: 11.9 +/- 2.4, After: 13.5 +/- 2.5 degrees C; P < 0.05), the number of waves (Pre: 1.1 +/- 1.0, After: 1.7 +/- 1.1; P < 0.001) and the thermal sensation (Pre: 1.7 +/- 0.9, After: 2.5 +/- 1.4; P < 0.001), after training. In conclusion, the aforementioned endurance exercise training significantly improved the finger CIVD response during cold-water hand immersion.
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| 34. |
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| 35. |
- Keramidas, Michail E., et al.
(författare)
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Respiratory muscle endurance training : Effect on normoxic and hypoxic exercise performance
- 2010
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Ingår i: European Journal of Applied Physiology. - : Springer Science and Business Media LLC. - 1439-6319 .- 1439-6327. ; 108:4, s. 759-769
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Tidskriftsartikel (refereegranskat)abstract
- The aim of this study was to investigate the effect of respiratory muscle endurance training on endurance exercise performance in normoxic and hypoxic conditions. Eighteen healthy males were stratified for age and aerobic capacity; and randomly assigned either to the respiratory muscle endurance training (RMT = 9) or to the control training group (CON = 9). Both groups trained on a cycle-ergometer 1 h day(-1), 5 days per week for a period of 4 weeks at an intensity corresponding to 50% of peak power output. Additionally, the RMT group performed a 30-min specific endurance training of respiratory muscles (isocapnic hyperpnea) prior to the cycle ergometry. Pre, Mid, Post and 10 days after the end of training period, subjects conducted pulmonary function tests (PFTs), maximal aerobic tests in normoxia ((V) over dotO(2max)NOR), and in hypoxia ((V) over dotO(2max)HYPO; F(I)O(2) = 0.12); and constant-load tests at 80% of (V) over dotO(2max)NOR in normoxia (CLT(NOR)), and in hypoxia (CLT(HYPO)). Both groups enhanced (V) over dotO(2max)NOR (CON: +13.5%; RMT: +13.4%), but only the RMT group improved (V) over dotO(2max)HYPO Post training (CON: -6.5%; RMT: +14.2%). Post training, the CON group increased peak power output, whereas the RMT group had higher values of maximum ventilation. Both groups increased CLT(NOR) duration (CON: +79.9%; RMT: +116.6%), but only the RMT group maintained a significantly higher CLT(NOR) 10 days after training (CON: +56.7%; RMT: +91.3%). CLT(HYPO) remained unchanged in both groups. Therefore, the respiratory muscle endurance training combined with cycle ergometer training enhanced aerobic capacity in hypoxia above the control values, but did not in normoxia. Moreover, no additional effect was obtained during constant-load exercise.
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| 36. |
- Kounalakis, S., et al.
(författare)
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Exercise thermoregulatory responses following a 28-day sleep-high train-low regimen
- 2012
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Ingår i: European Journal of Applied Physiology. - : Springer Science and Business Media LLC. - 1439-6319 .- 1439-6327. ; 112:11, s. 3881-3891
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Tidskriftsartikel (refereegranskat)abstract
- The potentiated exercise-sweating rate observed during acute hypoxia is diminished after a sleep-high train-low (SH-TL) regimen. We tested the hypothesis that this attenuation of the sweating response after SH-TL is compensated for by an increase in heat loss via vasodilatation. Nine male subjects participated in a 28-day SH-TL regimen. Before (pre-), and after (post-) the SH-TL protocol, they performed an test under normoxia and hypoxia. Additionally, pre- and post-SH-TL they completed three 30-min constant-work rate trials on a cycle ergometer. In one trial, the subjects inspired room air while exercising at 50 % of normoxic (CT). In the remaining trials, subjects exercised in hypoxia (FIO2 12.5 %), either at the same absolute (HAT) or relative (50 % of hypoxic ) work rate (HRT) as in CT. Despite similar exercise core temperature responses between pre- and post-SH-TL trials, sweating rate was potentiated in HAT pre-SH-TL [CT: 1.97 (0.42); HRT: 1.86 (0.31); HAT: 2.55 (0.53) mg cm(-2) min(-1); p < 0.05]. Post-SH-TL exercise sweating rate was increased for CT, and remained unchanged in HRT and HAT [CT: 2.42 (0.76); HRT: 2.01 (0.33); HAT: 2.59 (0.30) mg cm(-2) min(-1)]. Pre-SH-TL, the forearm-fingertip skin temperature difference (Tsk(f-f)) was higher in HAT than in CT and HRT by similar to 3.5A degrees C (p < 0.05). The inter-condition differences in Tsk(f-f) were diminished post-SH-TL. In conclusion, the decrease in sweating rate during hypoxic exercise, following a SH-TL regimen, was countered by an increase in vasodilatation (reduced Tsk(f-f)), whereas SH-TL enhanced the sweating response during normoxic exercise. The mechanisms underlying these SH-TL-induced alterations in thermoregulatory responses remain to be settled.
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| 37. |
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| 38. |
- Kölegard, Roger, et al.
(författare)
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Effects of physical fitness on relaxed G-tolerance and the exercise pressor response
- 2013
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Ingår i: European Journal of Applied Physiology. - : Springer Science and Business Media LLC. - 1439-6319 .- 1439-6327. ; 113:11, s. 2749-2759
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Tidskriftsartikel (refereegranskat)abstract
- Fighter pilots are commonly recommended strength training as a means of improving the tolerance to withstand high gravitoinertial (G) loads. Previous studies on the effect of short-term strength-training regimens on G-endurance show equivocal results, with a majority of the studies suggesting improved G-endurance. The mechanisms underlying such improvement are unknown. Presumably, any change in G-tolerance induced by physical training habits should be manifest following long-term training. We also reasoned that during repeated straining maneuvers-as during certain G-endurance protocols-the relaxed G-tolerance and the exercise pressure response may play a significant role in maintaining adequate arterial pressure, and hence that different training modalities might alter G-endurance, by altering the exercise pressor response. Three groups of males were studied, long-term (>6 months) endurance-trained (E; n = 17), strength-trained (S; n = 16) and untrained (U; n = 17) individuals. The pressor response was studied during sustained (40 s) isometric knee extensions at 50 % of the maximal contraction level. Relaxed gradual onset-rate G-tolerance was determined. G-tolerance was similar in the E (4.6 +/- 0.5 G), S (4.9 +/- 0.8 G) and U (4.6 +/- 0.8 G) groups. The mean arterial pressure increase during isometric exercise was higher in the S (36 +/- 7 mmHg = mean +/- SD) and U (35 +/- 16 mmHg) groups than in the E group (28 +/- 8 mmHg). The results suggest that relaxed G-tolerance is unaffected by physical training habits, and that the training modality affects the magnitude of the exercise pressor response. However, it seems that the response is blunted by endurance training rather than enhanced by strength training.
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| 39. |
- Kölegård, Roger, et al.
(författare)
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Distensibility in human veins as affected by 5 weeks of repeated elevations of local transmural pressure
- 2011
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Ingår i: European Journal of Applied Physiology. - : Springer Science and Business Media LLC. - 1439-6319 .- 1439-6327. ; 111:12, s. 3119-3125
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Tidskriftsartikel (refereegranskat)abstract
- The objectives were to investigate the effects of repeated increments in local intravascular pressure (pressure training; PT) on (1) distensibility in two arm veins, and (2) pain in the arm induced by markedly increased intravascular pressure. Elevation of venous distending pressure (DP) in an arm was induced by placing the subject (n = 8) in a pressure chamber with one arm protruding to the outside via a port in the chamber door, and increasing chamber pressure. During 5 weeks, venous DP in one arm was repeatedly (3 × 40 min/week) increased (65-105 mmHg). Pressure-distension relationships were determined in the brachial and cephalic veins by measuring diameter changes by ultrasonography during stepwise increments in DP to 180 mmHg. In the brachial vein, the diameter change in response to an increase in DP from 30 to 180 mmHg (distensibility) was reduced (P < 0.05) in the pressure-trained arm (11%) compared to that in the control arm before (23%) and after (21%) PT. The cephalic vein showed a similar response with a reduced (P < 0.05) distensibility in the pressure-trained arm (20%) compared to that in the control arm before (29%) and after (25%) PT. At any given DP, arm pain was less (P < 0.05) in the pressure-trained arm than in the control arm before and after PT, presumably reflecting the reduced venous distensibility in the pressure-trained arm. The results support the concept that the distensibility of venous walls adapts to meet the demands imposed by the prevailing local transmural pressures.
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| 40. |
- Laaksonen, Marko, et al.
(författare)
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Regional differences in blood flow, glucose uptake and fatty acid uptake within quadriceps femoris muscle during dynamic knee-extension exercise
- 2013
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Ingår i: European Journal of Applied Physiology. - : Springer Science and Business Media LLC. - 1439-6319 .- 1439-6327. ; 113:7, s. 1775-1782
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Tidskriftsartikel (refereegranskat)abstract
- The purpose of the present study was to investigate the regional differences in glucose and fatty acid uptake within skeletal muscle during exercise. Blood flow (BF), glucose uptake (GU) and free fatty acid uptake (FFAU) were measured in four different regions (vastus lateralis, VL; rectus femoris, RF; vastus intermedius, VI; and vastus medialis, VM) of the quadriceps femoris (QF) muscle during low-intensity, knee-extension exercise using positron emission tomography. BF was higher in VI than in VL, RF and VM (P < 0.05). FFAU was higher in VI (P < 0.001) but also in VM (P < 0.05) compared with VL and RF. In contrast, GU was higher in RF compared with VL (P < 0.05) but was not significantly different to VM or VI (both P = NS). FFAU within these four muscle regions correlated significantly with BF (r = 0.951, P < 0.05), whereas no significant relationship was observed between GU and BF (r = 0.352, P = NS). Therefore, skeletal muscle FFAU, but not GU, appears to be associated with BF during low-intensity exercise. The present results also indicate considerable regional differences in substrate use within working QF muscle. As such, an important methodological outcome from these results is that one sample from a specific part of the QF muscle does not represent the response in the entire QF muscle group.
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| 41. |
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| 42. |
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| 43. |
- Lindinger, Stefan, et al.
(författare)
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How do elite cross-country skiers adapt to different double poling frequencies at low to high speeds?
- 2011
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Ingår i: European Journal of Applied Physiology. - : Springer Science and Business Media LLC. - 1439-6319 .- 1439-6327. ; 111:6, s. 1103-1119
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Tidskriftsartikel (refereegranskat)abstract
- The purpose of the study was to examine the biomechanical-physiological effects of different frequencies using the double poling technique in cross-country skiing. Nine elite skiers roller-skied using poling frequencies of 40, 60 and 80 cycles·min-1 (Pf40, Pf60, Pf80) at submaximal treadmill speeds (12, 18, 24 km·h-1). Cycle characteristics, pole forces, joint angles and physiological responses were measured. Comparing Pf40 versus Pf60 versus Pf80 (all variables different at P < 0.05), absolute poling time decreased by up to 46%, as did absolute and relative (% cycle time) recovery times, at almost all speeds. Peak force, impulse of force and time to peak force decreased, whereas impact force increased with frequency at almost all speeds. Elbow ranges of motion and angular velocities, hip and knee angle maxima and flexion/extension ranges of motion per cycle decreased, whereas hip and knee angle minima, ranges of motion per minute and angular extension velocities during recovery phase all increased with frequency at nearly all speeds. Oxygen uptake and heart rate increased up to 13% (Pf40-60 versus Pf80) at all speeds. Pulmonary ventilation increased most distinctly at the highest speed. Blood lactate was lowest at Pf60 and highest at Pf80 (J-shape curve) at 24 km·h-1. Gross efficiency decreased with higher frequency at all speeds. These results demonstrate different biomechanical and physiological demands at different frequencies with the beneficial effects of lower poling frequencies at submaximal speeds. For training purposes, we suggest that cross-country skiers would benefit by training with different poling frequencies to vary their training load.
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| 44. |
- Lindqvist, Per, et al.
(författare)
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Cardiac mechanisms underlying normal exercise tolerance : gender impact
- 2012
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Ingår i: European Journal of Applied Physiology. - New York : Springer. - 1439-6319 .- 1439-6327. ; 112:2, s. 451-459
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Tidskriftsartikel (refereegranskat)abstract
- The aim of this study is to test our hypothesis that normal exercise tolerance differs according to gender and to identify potential functional cardiac relationships, which could explain those differences. A total of 44 healthy individuals with mean age of 49 ± 12 years (28-74 years, 22 males) constituted the study cohort. All individuals underwent resting and exercise Doppler echocardiogram simultaneously with peak oxygen uptake analysis (pVO(2)). At equal pVO(2), males achieved higher peak exercise workload (p < 0.001) and females higher heart rate (p < 0.001) but the two groups maintained similar indexed left ventricular (LV) stroke volume (SV) and cardiac output. Indexed LV end-diastolic (LVDVI) and end-systolic volumes (LVSVI) were smaller in females (p < 0.001 and p < 0.01, respectively), but filling time (FT) was shorter (p < 0.001) and they had higher early diastolic (E) velocity (p = 0.004), E/E (m) (myocardial E velocity) (p < 0.001) and global longitudinal strain rate atrial velocity (GLSRa') (p = 0.02), compared to males. In males, workload (p < 0.01), LVDVI (p < 0.01), LVSVI (p < 0.05), SVI (p < 0.001) directly but LV myocardial isovolumic relaxation time (IVRTm) (p < 0.01) inversely correlated with pVO(2). In females, mitral E velocity (p < 0.01), GLSRs' (p < 0.05) positively and LVFT negatively (p < 0.05) correlated with pVO(2). In a multivariable analysis SVI in males (p < 0.01) and GLSRs' in females (p < 0.01) were the strongest predictors for pVO(2). Thus, normal exercise capacity as determined by pVO(2) is related to the indexed stroke volume in males and left atrial pressure in females. These native normal differences between genders may explain the known vulnerability of women to endurance exercise compared to men.
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| 45. |
- Lundby, A. K. M., et al.
(författare)
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Kidney-synthesized erythropoietin is the main source for the hypoxia-induced increase in plasma erythropoietin in adult humans
- 2014
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Ingår i: European Journal of Applied Physiology. - : Springer Science and Business Media LLC. - 1439-6319 .- 1439-6327. ; 114:6, s. 1107-1111
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Tidskriftsartikel (refereegranskat)abstract
- Erythropoietin (EPO) is mainly synthesized within renal peritubular fibroblasts, and also other tissues such as the liver possess the ability. However, to what extent non-kidney produced EPO contributes to the hypoxia-induced increase in circulating EPO in adult humans remains unclear. We aimed to quantify this by assessing the distribution of EPO glycoforms which are characterized by posttranslational glycosylation patterns specific to the synthesizing cell. The analysis was performed on samples obtained in seven healthy volunteers before, during and after 1 month of sojourn at 3,454 m altitude. Umbilical cord (UC) plasma served as control. As expected a peak (p < 0.05) in urine (2.3 +/- A 0.5-fold) and plasma (3.3 +/- A 0.5-fold) EPO was observed on day 1 of high-altitude exposure, and thereafter the concentration decreased for the urine sample obtained after 26 days at altitude, but remained elevated (p < 0.05) by 1.5 +/- A 0.2-fold above the initial sea level value for the plasma sample. The EPO glycoform heterogeneity, in the urine samples collected at altitude, did not differ from values at sea level, but were markedly lower (p < 0.05) than the mean percent migrated isoform (PMI) for the umbilical cord samples. Our studies demonstrate (1) UC samples express a different glycoform distribution as compared to adult humans and hence illustrates the ability to synthesis EPO in non-kidney cells during fetal development (2) as expected hypoxia augments circulating EPO in adults and the predominant source here for remains being kidney derived.
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| 46. |
- Malmström, Eva-Maj, et al.
(författare)
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Experimentally induced deep cervical muscle pain distorts head on trunk orientation.
- 2013
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Ingår i: European Journal of Applied Physiology. - : Springer Science and Business Media LLC. - 1439-6327 .- 1439-6319. ; 113:10, s. 2487-2499
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Tidskriftsartikel (refereegranskat)abstract
- We wanted to explore the specific proprioceptive effect of cervical pain on sensorimotor control. Sensorimotor control comprises proprioceptive feedback, central integration and subsequent muscular response. Pain might be one cause of previously reported disturbances in joint kinematics, head on trunk orientation and postural control. However, the causal relationship between the impact of cervical pain on proprioception and thus on sensorimotor control has to be established.
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| 47. |
- McDonnell, A.C., et al.
(författare)
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Circadian rhythm of peripheral perfusion during 10-day hypoxic confinement and bed rest
- 2014
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Ingår i: European Journal of Applied Physiology. - : Springer Science and Business Media LLC. - 1439-6319 .- 1439-6327. ; 114:10, s. 2093-2104
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Tidskriftsartikel (refereegranskat)abstract
- Future planetary habitats will be hypobaric and hypoxic to reduce the risk of decompression sickness during preparation for extra-vehicular activities. This study was part of a research programme investigating the combined effects of hypoxia and microgravity on physiological systems. We tested the hypothesis that hypoxia-induced peripheral vasoconstriction persists at night and is aggravated by bed rest. Since sleep onset has been causally linked to nocturnal vasodilatation, we reasoned that hypoxia-induced vasoconstriction at night may explain sleep disturbances at altitude. Peripheral perfusion alterations as a consequence of bed rest may explain poor sleep quality reported during sojourns on the International Space Station. Eleven males underwent three 10-day interventions in a randomised order: (1) hypoxic ambulatory confinement; (2) hypoxic bed rest; (3) normoxic bed rest. During each intervention we conducted 22-h monitoring of peripheral perfusion, as reflected by the skin temperature gradient. Measurements were conducted on the first (D 1) and last day (D 10) of each intervention. All interventions resulted in a decrease in daytime toe perfusion from D 1 to D 10. There was no difference in the magnitude of the daytime reduction in toe perfusion between the three interventions. There was a significant vasodilatation of the toes in all interventions by 11 pm. The fingertips remained well perfused throughout. Daytime vasoconstriction induced by hypoxia and/or bed rest is abolished at night, lending further support to the theory that changes in peripheral skin temperature may be functionally linked to sleep onset.
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| 48. |
- Meyland, Jacob, et al.
(författare)
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Sex differences in muscular load among house painters performing identical work tasks
- 2014
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Ingår i: European Journal of Applied Physiology. - : Springer Science and Business Media LLC. - 1439-6327 .- 1439-6319. ; 114:9, s. 1901-1911
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Tidskriftsartikel (refereegranskat)abstract
- The present study aimed to estimate possible differences in upper body muscular load between male and female house painters performing identical work tasks. Sex-related differences in muscular load may help explain why women, in general, have more musculoskeletal complaints than men. In a laboratory setting, 16 male and 16 female house painters performed nine standardised work tasks common to house painters. Unilateral electromyography (EMG) recordings were obtained from the supraspinatus muscle by intramuscular electrodes and from the trapezius, extensor and flexor carpi radialis muscles by surface electrodes. Relative muscular loads in %EMG(max) as well as exerted force in Newton, based on ramp calibrations, were assessed. Sex differences were tested using a mixed model approach. Women worked at about 50 % higher relative muscular loads than men in the supraspinatus and forearm muscles at all percentiles and in all tasks. Women exerted about 30 % less force in the trapezius muscle at the 50th percentile. Female house painters had a higher relative muscular load than their male colleagues without exerting more force. The effects of a higher relative muscular load accumulated over years of work may in part explain why musculoskeletal complaints in the upper body occur more frequently among women than men.
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- Michels, Nathalie, et al.
(författare)
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Determinants and reference values of short-term heart rate variability in children.
- 2013
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Ingår i: European journal of applied physiology. - : Springer Science and Business Media LLC. - 1439-6327 .- 1439-6319. ; 113:6, s. 1477-1488
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Tidskriftsartikel (refereegranskat)abstract
- This paper provides age- and sex-specific reference values for short-term heart rate variability (HRV) data in children by time domain and frequency domain methods. Furthermore, HRV determinants will be determined. In 460 children (5-10years), 5-minute HRV measurements in supine position were undertaken with Polar chest belts. The data were manually edited and processed with time and frequency domain methods. Age, time point, physical activity (accelerometry), physical fitness (cardiopulmonary fitness, upper and lower limb muscular fitness) and body composition (body mass index, fat%, fat and fat-free mass) were analysed as determinants using multiple regression analysis stratified by sex. Sex- and age-specific reference values were produced. Overall, girls had lower HRV. Age-related parasympathetic increases and sympathetic decreases were seen with sometimes age-related year-to-year wave-like changes in boys. The time point of recording had limited influence on HRV. Of the lifestyle related factors, fatness (only 7% overweight) was not associated with HRV but fat-free mass, physical activity and in particular physical fitness (over and above activity) had a favourable association by increased parasympathetic activity. Future HRV studies in children should consider age, sex and physical fitness.
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