51. |
- Nielsen, Joachim, et al.
(author)
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Skeletal muscle glycogen content and particle size of distinct subcellular localizations in the recovery period after a high-level soccer match
- 2012
-
In: European Journal of Applied Physiology. - : Springer Science and Business Media LLC. - 1439-6319 .- 1439-6327. ; 112:10, s. 3559-3567
-
Journal article (peer-reviewed)abstract
- Whole muscle glycogen levels remain low for a prolonged period following a soccer match. The present study was conducted to investigate how this relates to glycogen content and particle size in distinct subcellular localizations. Seven high-level male soccer players had a vastus lateralis muscle biopsy collected immediately after and 24, 48, 72 and 120 h after a competitive soccer match. Transmission electron microscopy was used to estimate the subcellular distribution of glycogen and individual particle size. During the first day of recovery, glycogen content increased by ~60% in all subcellular localizations, but during the subsequent second day of recovery glycogen content located within the myofibrils (Intramyofibrillar glycogen, a minor deposition constituting 10–15% of total glycogen) did not increase further compared with an increase in subsarcolemmal glycogen (−7 vs. +25%, respectively, P = 0.047). Conversely, from the second to the fifth day of recovery, glycogen content increased (53%) within the myofibrils compared to no change in subsarcolemmal or intermyofibrillar glycogen (P < 0.005). Independent of location, increment in particle size preceded increment in number of particles. Intriguingly, average particle size decreased; however, in the period from 3 to 5 days after the match. These findings suggest that glycogen storage in skeletal muscle is influenced by subcellular localization-specific mechanisms, which account for an increase in number of glycogen particles located within the myofibrils in the period from 2 to 5 days after the soccer match.
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52. |
- Nilsson, Johnny, et al.
(author)
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Kinematic, kinetic and electromyographic adaptation to speed and resistance in double poling cross country skiing
- 2013
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In: European Journal of Applied Physiology. - : Springer Science and Business Media LLC. - 1439-6319 .- 1439-6327. ; 113:6, s. 1385-1394
-
Journal article (peer-reviewed)abstract
- This study incorporated variations in speed and the horizontal resistance acting upon elite female skiers during double poling (DP) on a treadmill and specifically analyzed biomechanical adaptations to these variations. Whole body kinematics and pole force data were recorded and used to calculate the moment of force acting on the shoulder and elbow joints. Data were obtained with a 3D optoelectronic system using reflective markers at given anatomical landmarks. Forces along the long axis of the right pole were measured with a piezoelectric force transducer. Surface electrodes were used to record EMG activity in the rectus femoris, rectus abdominis, latissimus dorsi and triceps brachii muscles. In a first set of recordings, the participants double poled with zero elevation at five different speeds from 8 to 17 km h(-1). In a second set of recordings, horizontal resistance was added by weights (0.4-1.9 kg) attached to a pulley system pulling the skier posteriorly during DP at 14 km h(-1). Results showed increasing relative duration of the thrust phase with increasing resistance, but not with speed. Significant kinematic differences occurred with increase in both speed and resistance. The mean (+/- SD) horizontal force components ranged between 1.7 (+/- 1.3) and 2.8 (+/- 1.1) percent (%) bodyweight (BW) in the speed adaptation and 3.1 (+/- 0.6) and 4.0 (+/- 1.3) % BW in the adaptation to horizontal resistance. Peak muscle activity showed a central to peripheral (proximo-distal) activation sequence. The temporal cycle phase pattern in the adaptation to speed and horizontal resistance differed.
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53. |
- Nobel, Gerard, et al.
(author)
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Effects of motion sickness on thermoregulatory responses in a thermoneutral air environment
- 2012
-
In: European Journal of Applied Physiology. - : Springer Science and Business Media LLC. - 1439-6319 .- 1439-6327. ; 112:5, s. 1717-1723
-
Journal article (peer-reviewed)abstract
- Motion sickness (MS) has been identified as a non-thermal factor that can moderate autonomic thermoregulatory responses. It has been shown that MS exaggerates core cooling during immersion in cold (15A degrees C) and luke-warm (28A degrees C) water by attenuating cold-induced vasoconstriction. The aim of the present study was to investigate whether MS affects thermal balance in a thermoneutral air environment. Eleven subjects were exposed to rotation in two conditions, control (CN) and MS. In the CN condition subjects refrained from head movements, whereas in the MS condition they performed a sequence of maximal head movements (left, right, up, down) at 15-s intervals until they were very nauseous. Sweating rate, rectal temperature (T (re)), the difference in temperature between the right forearm and tip of the second finger (T (ff)) as an index of cutaneous vasomotor tone, perceived MS, thermal comfort and temperature perception were recorded before and during rotation, and during 90-min post-rotation. During the post-rotation period, T (re) dropped and sweating rate increased in the MS but not in the CN condition. The T (ff) response suggests that MS-induced peripheral vasodilatation which, together with the sweating resulted in increased heat loss. During rotation, subjects perceived temperature to be uncomfortably high, suggesting that MS may also affect thermoregulatory behaviour. It thus appears that also in a thermoneutral air environment MS may substantially affect thermal balance.
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54. |
- Nordlund Ekblom, Maria M, et al.
(author)
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Concurrent EMG feedback acutely improves strength and muscle activation
- 2012
-
In: European Journal of Applied Physiology. - : Springer Science and Business Media LLC. - 1439-6319 .- 1439-6327. ; 112:5, s. 1899-1905
-
Journal article (peer-reviewed)abstract
- The purpose of this study was to investigate the acute effects of electromyographic (EMG) feedback on muscle activation and strength during maximal voluntary concentric and eccentric muscle actions. 15 females performed two sets of three lengthening and three shortening maximal voluntary isokinetic knee extensions at 20A degrees A s(-1) over 60A degrees range of motion. After the first set, subjects were randomized to either a control group (n = 8) or a feedback group (n = 7). In the second set, the control group performed tasks identical to those in the first set, whereas the feedback group additionally received concurrent visual feedback of the EMGrms from Vastus Medialis (VM). Knee extensor strength and EMG activation of VM, Vastus lateralis (VL) and hamstrings (HAM) were measured during the MVCs. Analyses were performed separately in a 1 s preactivation phase, a 1 s initial movement phase and a 1 s late movement phase. EMG feedback was associated with significantly higher knee extensor strength in all phases (20.5% p < 0.05, 18.2% p < 0.001 and 19% p < 0.001, respectively) for the eccentric MVCs and in the preactivation phase (16.3%, p < 0.001) and initial movement phases (7.2%, p < 0.05) for concentric MVCs. EMG feedback from VM further improved activation in VM and HAM but not VL. These findings suggested that concurrent visual EMG feedback from VM could acutely enhance muscle strength and activation. Before recommending implementation of EMG feedback in resistance training paradigms, the feedback parameters needs to be optimized and its long-term effects needs to be scrutinized.
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55. |
- Norrbrand, Lena, et al.
(author)
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Flywheel resistance training calls for greater eccentric muscle activation than weight training
- 2010
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In: European Journal of Applied Physiology. - : Springer Science and Business Media LLC. - 1439-6319 .- 1439-6327. ; 110:5, s. 997-1005
-
Journal article (peer-reviewed)abstract
- Changes in muscle activation and performance were studied in healthy men in response to 5 weeks of resistance training with or without "eccentric overload". Subjects, assigned to either weight stack (grp WS; n = 8) or iso-inertial "eccentric overload" flywheel (grp FW; n = 9) knee extensor resistance training, completed 12 sessions of four sets of seven concentric-eccentric actions. Pre- and post-measurements comprised maximal voluntary contraction (MVC), rate of force development (RFD) and training mode-specific force. Root mean square electromyographic (EMG(RMS)) activity of mm. vastus lateralis and medialis was assessed during MVC and used to normalize EMG(RMS) for training mode-specific concentric (EMG(CON)) and eccentric (EMG(ECC)) actions at 90°, 120° and 150° knee joint angles. Grp FW showed greater (p < 0.05) overall normalized angle-specific EMG(ECC) of vastii muscles compared with grp WS. Grp FW showed near maximal normalized EMG(CON) both pre- and post-training. EMG(CON) for Grp WS was near maximal only post-training. While RFD was unchanged following training (p > 0.05), MVC and training-specific strength increased (p < 0.05) in both groups. We believe the higher EMG(ECC) activity noted with FW exercise compared to standard weight lifting could be attributed to its unique iso-inertial loading features. Hence, the resulting greater mechanical stress may explain the robust muscle hypertrophy reported earlier in response to flywheel resistance training.
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56. |
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57. |
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58. |
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59. |
- Paulsen, G., et al.
(author)
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Strength training elevates HSP27, HSP70 and alpha B-crystallin levels in musculi vastus lateralis and trapezius
- 2012
-
In: European Journal of Applied Physiology. - Heidelberg, Germany : Springer. - 1439-6319 .- 1439-6327. ; 112:5, s. 1773-1782
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Journal article (peer-reviewed)abstract
- A single bout of high-force exercise has been shown to increase the muscle levels of heat shock proteins (HSPs). Here, changes in the levels of HSPs after 2 and 11 weeks of strength training with either one or three sets per exercise were examined. Fifteen young men (27 +/- A 6 years, 182 +/- A 8 cm and 82 +/- A 13 kg) were randomized to train either one set in lower-body exercises and three sets in upper-body exercises (1L-3UB), or three sets in lower-body exercises and one set in upper-body exercises (3L-1UB). Biopsies from vastus lateralis and trapezius were obtained before, during (2 weeks) and after 11 weeks of strength training (3 bouts per week). The biopsies were analysed for HSP27 (cytosolic and cytoskeletal fractions) and HSP70 and alpha B-crystallin (cytosolic fraction). No evidence for an effect of training volume (1 vs. 3 sets) on the HSP response was found. For all subjects combined, HSP27 [186 +/- A 69% (mean +/- A SD)], HSP70 (146 +/- A 51%) and alpha B-crystallin (184 +/- A 82%) increased in the cytosolic fraction of vastus lateralis after 11 weeks of training. In the trapezius, the only observed increase was for HSP27 in the cytosolic fraction after 2 weeks of training (149 +/- A 59%). However, the trapezius contained somewhat higher levels of HSP70 and alpha B-crystallin than vastus lateralis at baseline. The HSP27 levels in the cytoskeletal compartment did not increase significantly in either muscle. In conclusion, strength training resulted-independent of training volume-in elevated levels of HSP27, HSP70 and alpha B-crystallin in the cytosolic compartment of the vastus lateralis. In the trapezius, only the cytosolic HSP27 levels were increased with training.
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60. |
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61. |
- Peolsson, Michael, et al.
(author)
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Tissue motion pattern of ventral neck muscles investigated by tissue velocity ultrasonography imaging
- 2010
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In: European Journal of Applied Physiology. - : Springer Science and Business Media LLC. - 1439-6319 .- 1439-6327. ; 109:5, s. 899-908
-
Journal article (peer-reviewed)abstract
- We designed this experimental study to investigate tissue motions and thus infer the recruitment pattern of the ventral neck muscles [sternocleidomastoid (SCM), longus capitis (Lca), and longus colli (Lco)] at the C4-C5 level in healthy volunteers during isometric manual resistance of the head in flexion in a seated position. This exercise is used in the physiotherapeutic treatment of neck pain and is assumed to activate the deep ventral muscles, but the assumption has not been clearly evaluated. Neck flexors of 16 healthy volunteers (mean age 24 years, SD 3.7) were measured using ultrasonography with strain and strain rate (SR) tissue velocity imaging (TVI) during isometric contraction of flexor muscles. TVI involves using Doppler imaging to study tissue dynamics. All three muscles showed a deformation compared to rest. Except for the initial contraction phase, Lco exhibited a lower strain than Lca and SCM but was the only muscle with a significant change in SR between the phases. When the beginning of the contraction phase was analysed, Lco was the first to be deformed among most volunteers, followed by Lca and then SCM. The exercise investigated seems to be useful as a "stabilizing" exercise for Lco. Our suggestion is that in further research, Lco and Lca should be investigated as separate muscles. TVI could be used to study tissue motions and thus serve as an indicator of muscle patterning between the neck flexors, with the possibility of separating Lco and Lca.
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62. |
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63. |
- Psilander, Niklas, et al.
(author)
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Exercise with low glycogen increases PGC-1α gene expression in human skeletal muscle.
- 2013
-
In: European Journal of Applied Physiology. - : Springer Science and Business Media LLC. - 1439-6319 .- 1439-6327. ; 113:4, s. 951-963
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Journal article (peer-reviewed)abstract
- Recent studies suggest that carbohydrate restriction can improve the training-induced adaptation of muscle oxidative capacity. However, the importance of low muscle glycogen on the molecular signaling of mitochondrial biogenesis remains unclear. Here, we compare the effects of exercise with low (LG) and normal (NG) glycogen on different molecular factors involved in the regulation of mitochondrial biogenesis. Ten highly trained cyclists (VO(2max) 65 ± 1 ml/kg/min, W (max) 387 ± 8 W) exercised for 60 min at approximately 64 % VO(2max) with either low [166 ± 21 mmol/kg dry weight (dw)] or normal (478 ± 33 mmol/kg dw) muscle glycogen levels achieved by prior exercise/diet intervention. Muscle biopsies were taken before, and 3 h after, exercise. The mRNA of peroxisome proliferator-activated receptor-γ coactivator-1 was enhanced to a greater extent when exercise was performed with low compared with normal glycogen levels (8.1-fold vs. 2.5-fold increase). Cytochrome c oxidase subunit I and pyruvate dehydrogenase kinase isozyme 4 mRNA were increased after LG (1.3- and 114-fold increase, respectively), but not after NG. Phosphorylation of AMP-activated protein kinase, p38 mitogen-activated protein kinases and acetyl-CoA carboxylase was not changed 3 h post-exercise. Mitochondrial reactive oxygen species production and glutathione oxidative status tended to be reduced 3 h post-exercise. We conclude that exercise with low glycogen levels amplifies the expression of the major genetic marker for mitochondrial biogenesis in highly trained cyclists. The results suggest that low glycogen exercise may be beneficial for improving muscle oxidative capacity.
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64. |
- Psilander, Niklas, et al.
(author)
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Mitochondrial gene expression in elite cyclists : effects of high-intensity interval exercise.
- 2010
-
In: European Journal of Applied Physiology. - : Springer Science and Business Media LLC. - 1439-6319 .- 1439-6327. ; 110:3, s. 597-606
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Journal article (peer-reviewed)abstract
- Little is known about the effect of training on genetic markers for mitochondrial biogenesis in elite athletes. We tested the hypothesis that low-volume sprint interval exercise (SIE) would be as effective as high-volume interval exercise (IE). Ten male cyclists competing on national elite level (W (max) 403 ± 13 W, VO(2peak) 68 ± 1 mL kg(-1) min(-1)) performed two interval exercise protocols: 7 × 30-s "all-out" bouts (SIE) and 3 × 20-min bouts at ~87% of VO(2peak) (IE). During IE, the work was eightfold larger (1,095 ± 43 vs. 135 ± 5 kJ) and the exercise duration 17 times longer (60 vs. 3.5 min) than during SIE. Muscle samples were taken before and 3 h after exercise. The mRNA of upstream markers of mitochondrial biogenesis [peroxisome proliferator-activated receptor-γ coactivator-1 (PGC-1α), PGC-1α-related coactivator (PRC) and peroxisome proliferator-activated receptor δ (PPARδ)] increased to the same extent after SIE and IE (6-, 1.5- and 1.5-fold increase, respectively). Of the downstream targets of PGC-1α, mitochondrial transcription factor A (Tfam) increased only after SIE and was significantly different from that after IE (P < 0.05), whereas others increased to the same extent (pyruvate dehydrogenase kinase, PDK4) or was unchanged (nuclear respiratory factor 2, NRF2). We conclude that upstream genetic markers of mitochondrial biogenesis increase in a similar way in elite athletes after one exercise session of SIE and IE. However, since the volume and duration of work was considerably lower during SIE and since Tfam, the downstream target of PGC-1α, increased only after SIE, we conclude that SIE might be a time-efficient training strategy for highly trained individuals.
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65. |
- Rae, Dale E, et al.
(author)
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Skeletal muscle telomere length in healthy, experienced, endurance runners.
- 2010
-
In: European journal of applied physiology. - : Springer Science and Business Media LLC. - 1439-6327 .- 1439-6319. ; 109:2, s. 323-330
-
Journal article (peer-reviewed)abstract
- Measuring the DNA telomere length of skeletal muscle in experienced endurance runners may contribute to our understanding of the effects of chronic exposure to endurance exercise on skeletal muscle. This study compared the minimum terminal restriction fragment (TRF) length in the vastus lateralis muscle of 18 experienced endurance runners (mean age: 42 +/- 7 years) to those of 19 sedentary individuals (mean age: 39 +/- 10 years). The runners had covered almost 50,000 km in training and racing over 15 years. Minimum TRF lengths measured in the muscle of both groups were similar (P = 0.805) and within the normal range. Minimum TRF length in the runners, however, was inversely related to their years spent running (r = -0.63, P = 0.007) and hours spent training (r = -0.52, P = 0.035). Therefore, since exposure to endurance running may influence minimum TRF length, and by implication, the proliferative potential of the satellite cells, chronic endurance running may be seen as a stressor to skeletal muscle.
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66. |
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67. |
- Richter, Hans O., et al.
(author)
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Eye-lens accommodation load and static trapezius muscle activity
- 2011
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In: European Journal of Applied Physiology. - : Springer Science and Business Media LLC. - 1439-6319 .- 1439-6327. ; 111:1, s. 29-36
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Journal article (peer-reviewed)abstract
- The purpose of this experimental study was to investigate if sustained periods of oculomotor load impacts on neck/scapular area muscle activity. The static trapezius muscle activity was assessed from bipolar surface electromyography, normalized to a submaximal contraction. Twenty-eight subjects with a mean age of 29 (range 19–42, SD 8) viewed a high-contrast fixation target for two 5-min periods through: (1) -3.5 dioptre (D) lenses; and (2) 0 D lenses. The target was placed 5 D away from the individual’s near point of accommodation. Each subject’s ability to compensate for the added blur was extracted via infrared photorefraction measurements. Subjects whose accommodative response was higher in the -D blur condition (1) showed relatively more static bilateral trapezius muscle activity level. During no blur (2) there were no signs of relationships. The results indicate that sustained eye-lens accommodation at near, during ergonomically unfavourable viewing conditions, could possibly represent a risk factor for trapezius muscle myalgia.
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68. |
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69. |
- Rojc, Bojan, et al.
(author)
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The separate and combined effects of hypoxia and sustained recumbency/inactivity on sleep architecture
- 2014
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In: European Journal of Applied Physiology. - : Springer Science and Business Media LLC. - 1439-6319 .- 1439-6327. ; 114:9, s. 1973-1981
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Journal article (peer-reviewed)abstract
- The objective was to determine the separate and combined effects of hypoxia and inactivity/unloading on sleep architecture during a 10-day period of confinement. Ten subjects participated in three 10-day trials in random order: hypoxic ambulatory (HAMB), hypoxic bedrest (HBR), and normoxic bedrest (NBR). During the HAMB and HBR trials, subjects were confined to a hypoxic facility. The hypoxia profile was: simulated altitude of 2,990 m on day 1, 3,380 m on day 2, and 3,881 m on day 3. In the NBR and HBR trials, subjects maintained a horizontal position throughout the confinement period. During each trial, sleep polysomnography was conducted one night prior to (baseline; altitude of facility is 940 m) and on the first (NT1, altitude 2,990 m) and tenth (NT10, altitude 3,881 m) night of the 10-day intervention. Average time in sleep stage 1 decreased from NT1 to NT10 irrespective of trial. Overall incidence and time spent in periodic breathing increased from NT1 to NT10 in both HAMB and HBR. During NT1, both HAMB and HBR reduced slow-wave sleep and increased light sleep, whereas NBR and HBR increased the number of awakenings/night. There were fewer awakenings during HAMB than NBR. Acute exposure to both hypoxia and bedrest (HBR) results in greater sleep fragmentation due to more awakenings attributed to bedrest, and lighter sleep as a result of reduced slow wave sleep caused by the hypoxic environment.
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70. |
- Rosdahl, Hans, et al.
(author)
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Evaluation of the Oxycon Mobile metabolic system against the Douglas bag method
- 2010
-
In: European Journal of Applied Physiology. - : Springer Science and Business Media LLC. - 1439-6319 .- 1439-6327. ; 109:2, s. 159-171
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Journal article (peer-reviewed)abstract
- The aim of this study was to evaluate two versions of the Oxycon Mobile portable metabolic system, (OMPS1 and OMPS2) in a wide range of oxygen uptake, using the Douglas bag method (DBM) as criterion method. The metabolic variables VO2, VCO2, respiratory exchange ratio and VE were measured during submaximal and maximal cycle ergometer exercise with sedentary, moderately trained individuals and athletes as participants. Test-retest reliability was investigated using the OMPS1. The coefficients of variation varied between 2% and 7% for the metabolic parameters measured at different work rates, and resembled those obtained with the DBM. With the OMPS1, systematic errors were found in the determination of VO2 and VCO2. At submaximal work rates VO2 was 6-14% and VCO2 5-9% higher than with the DBM. At VO2max both VO2 and VCO2 were slightly lower as compared to DBM (-4.1% and -2.8% respectively). With OMPS2, VO2 was determined accurately within a wide measurement range (about 1-5.5 L*min-1), while VCO2 was overestimated (3-7%). VE was accurate at submaximal work rates with both OMPS1 and OMPS2, whereas underestimations (4-8%) were noted at VO2max. The present study is the first to demonstrate that a wide range of VO2 can be measured accurately with the Oxycon Mobile portable metabolic system (second generation). Future investigations are suggested to clarify reasons for the small errors noted for VE and VCO2 versus the Douglas bag measurements, and also to gain knowledge of the performance of the device under applied and non-laboratory conditions.
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71. |
- Rosdahl, Hans, et al.
(author)
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The Moxus Modular metabolic sustem evaluated with two sensors for ventilation against the Douglas bag method
- 2013
-
In: European Journal of Applied Physiology. - : Springer Science and Business Media LLC. - 1439-6319 .- 1439-6327. ; 113:5, s. 1353-1367
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Journal article (peer-reviewed)abstract
- This study evaluated the Moxus metabolic system with the Douglas bag method (DBM) as criterion. Reliability and validity were investigated in a wide range of ventilation and oxygen uptake and two sensors for determining ventilation were included. Thirteen well-trained athletes participated in one pre-test and four tests for data collection, exercising on a cycle ergometer at five submaximal powers (50-263 W) and at [Formula: see text]. Gas exchange variables were measured simultaneously using a serial setup with data collected on different days in an order randomized between Moxus with pneumotachometer (MP) and turbine flowmeter (MT) sensors for ventilation. Reliability with both sensors was comparable to the DBM. Average CV (%) of all exercise intensities were with MP: 3.0 ± 1.3 for VO(2), 3.8 ± 1.5 for VCO(2), 3.1 ± 1.2 for the respiratory exchange ratio (RER) and 4.2 ± 0.8 for V (E). The corresponding values with MT were: 2.7 ± 0.3 for VO(2), 4.7 ± 0.4 for VCO(2), 3.3 ± 0.9 for RER and 4.8 ± 1.4 for V (E). Validity was acceptable except for small differences related to the determination of ventilation. The relative differences in relation to DBM at the powers including [Formula: see text] were similar for both sensors with the ranges being: +4 to -2 % for V (E), +5 to -3 % for VO(2) and +5 to -4 % for VCO(2) while RER did not differ at any power. The Moxus metabolic system shows high and adequate reliability and reasonable validity over a wide measurement range. At a few exercise levels, V (E) differed slightly from DBM, resulting in concomitant changes in VO(2) and VCO(2).
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72. |
- Rullman, E, et al.
(author)
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Circulating MMP-9 during exercise in humans
- 2013
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In: European Journal of Applied Physiology. - : Springer Verlag (Germany). - 1439-6319 .- 1439-6327. ; 113:5, s. 1249-1255
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Journal article (peer-reviewed)abstract
- Matrix metalloproteinase 9 (MMP-9) is a member of a family of zinc-dependent endopeptidases capable of degrading extracellular matrix (ECM) proteins. A single bout of exercise increases levels of activated MMP-9 in skeletal muscle and in the circulation. However, whether the exercise-induced activation of MMP-9 is associated with ECM remodeling and the cellular source behind MMP-9 in the circulation is not known. In the present study ten healthy male subjects performed a single cycle exercise bout and arterial and venous femoral blood was collected. To test if exercise induces basal lamina degradation and if circulating levels of MMP-9 is related to a release from the exercising muscle, arteriovenous differences of collagen IV and MMP-9 were measured by ELISA and zymography, respectively. Furthermore, markers of neutrophil degranulation elastase and neutrophil gelatinase-associated lipocalin (NGAL) were measured by ELISA. Plasma levels of collagen IV increased during the exercise bout and an increased arteriovenous difference of collagen IV was noted at 27 min of exercise. Plasma levels of MMP-9 were increased at both 27 and 57 min of exercise but no arteriovenous difference was noted. No changes over time were detected for elastase and NGAL. The observed release of collagen IV from the exercising muscle indicate basal lamina turnover following a single bout of exercise. No detectable release of MMP-9 was observed, suggesting that the increase in plasma MMP-9 could come from a source other than the skeletal muscle.
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73. |
- Sahlén, Anders, et al.
(author)
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Altered ventriculo-arterial coupling during exercise in athletes releasing biomarkers after endurance running
- 2012
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In: European Journal of Applied Physiology. - : Springer Science and Business Media LLC. - 1439-6319 .- 1439-6327. ; 112:12, s. 4069-4079
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Journal article (peer-reviewed)abstract
- Exercise can lead to release of biomarkers such as cardiac troponin T (cTnT) and N-terminal pro-brain natriuretic peptide (NT-proBNP), a poorly understood phenomenon proposed to especially occur with highintensity exercise in less trained subjects. We hypothesised that haemodynamic perturbations during exercise are larger in athletes with cTnT release, and studied athletes with detectable cTnT levels after an endurance event (HIGH; n = 16; 46 ± 9 years) against matched controls whose levels were undetectable (LOW; n = 11; 44 ± 7 years). Echocardiography was performed at rest and at peak supine bicycle exercise stress. Left ventricular (LV) end-systolic elastance (ELV a load-independent measure of LV contractility), effective arterial elastance (EA a lumped index of arterial load) and end-systolic meridional wall stress were calculated from cardiac dimensions and brachial blood pressure. Efficiency of cardiac work was judged from the ventriculo-arterial coupling ratio (EA/ELV: optimal range 0.5-1.0). While subgroups had similar values at rest, we found ventriculo-arterial mismatch during exercise in HIGH subjects (0.47 (0.39-0.58) vs. LOW: 0.73 (0.62-0.83); p<0.01] due to unopposed increase in ELV (p<0.05). In LOW subjects, a greater increase occurred in EA during exercise (+81 ± 67 % vs. HIGH: +39 ± 32 %; p = 0.02) which contributed to a maintained coupling ratio. Subjects with higher baseline NT-proBNP had greater systolic wall stress during exercise (R2 = 0.39; p<0.01) despite no correlation at rest (p = ns). In conclusion, athletes with exercise-induced biomarker release exhibit ventriculo-arterial mismatch during exercise, suggesting non-optimal cardiac work may contribute to this phenomenon.
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74. |
- Salier Eriksson, Jane, et al.
(author)
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Validity of the Oxycon Mobile metabolic system under field measuring conditions
- 2012
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In: European Journal of Applied Physiology. - : Springer. - 1439-6319 .- 1439-6327. ; 112:1, s. 345-355
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Journal article (peer-reviewed)abstract
- Abstract Purpose: It is essential to validate portable metabolic systems, not only in laboratory settings, but also in field measuring conditions, such as prolonged moderate exercise at low temperatures, high humidity and with external wind. Methods: VO2, VCO2, RER and VE were measured using the Oxycon Mobile (OM), with a windshield, during cycle ergometer exercise: (I) indoors at three submaximal workloads with no wind or with external wind (13–20 m·s-1) from front, side and back; (II) at two submaximal workloads outdoors (12 ± 2oC; 86 ± 7% RH), with and without a system for drying the ambient air around the air sampling tube; and (III) at one workload outdoors for 45 min (5 ± 4oC; 69 ± 16.5% RH). Any physiological drift was checked for with pre- and postmeasurements by the Douglas bag method (DBM). Results: A minor effect of external wind from behind was noted in RER and VE (-2 and -3%).. The system for drying the ambient air around the gas sampling tube had no effect on the measured levels. A small difference in VCO2 drift between the OM and DBM (1.5 mL·min-2) was noted in the stability test. Conclusion: Heavy external wind applied from different directions generally does not affect the measurements of the OM. Furthermore, when using a unit for drying the ambient air around the gas sampling tube, the OM can accurately measure VO2, RER and VE at submaximal workloads for at least45 min under challenging conditions with regard to humidity and temperature.
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75. |
- Sandbakk, O., et al.
(author)
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Gender differences in the physiological responses and kinematic behaviour of elite sprint cross-country skiers
- 2012
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In: European Journal of Applied Physiology. - : Springer Science and Business Media LLC. - 1439-6319 .- 1439-6327. ; 112:3, s. 1087-1094
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Journal article (peer-reviewed)abstract
- Gender differences in performance by elite endurance athletes, including runners, track cyclists and speed skaters, have been shown to be approximately 12%. The present study was designed to examine gender differences in physiological responses and kinematics associated with sprint cross-country skiing. Eight male and eight female elite sprint cross-country skiers, matched for performance, carried out a submaximal test, a test of maximal aerobic capacity (VO2max) and a shorter test of maximal treadmill speed (Vmax) during treadmill roller skiing utilizing the G3 skating technique. The men attained 17% higher speeds during both the VO2max and the Vmax tests (PÂ <Â 0.05 in both cases), differences that were reduced to 9% upon normalization for fat-free body mass. Furthermore, the men exhibited 14 and 7% higher VO2max relative to total and fat-free body mass, respectively (PÂ <Â 0.05 in both cases). The gross efficiency was similar for both gender groups. At the same absolute speed, men employed 11% longer cycles at lower rates, and at peak speed, 21% longer cycle lengths (PÂ <Â 0.05 in all cases). The current study documents approximately 5% larger gender differences in performance and VO2max than those reported for comparable endurance sports. These differences reflect primarily the higher VO2max and lower percentage of body fat in men, since no gender differences in the ability to convert metabolic rate into work rate and speed were observed. With regards to kinematics, the gender difference in performance was explained by cycle length, not by cycle rate.
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76. |
- Sandbakk, O., et al.
(author)
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The influence of incline and speed on work rate, gross efficiency and kinematics of roller ski skating
- 2012
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In: European Journal of Applied Physiology. - : Springer Science and Business Media LLC. - 1439-6319 .- 1439-6327. ; 112:8, s. 2829-2838
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Journal article (peer-reviewed)abstract
- During competitions, elite cross-country skiers produce higher external work rates on uphill than on flat terrain. However, it is not presently known whether this reflects solely higher energy expenditure. Furthermore, the kinematic factors associated with these higher rates of uphill work have not yet been examined. Therefore, in the present investigation the work rate and associated kinematic parameters at similar metabolic rates during roller ski skating on flat and uphill terrains have been compared. Seven elite male skiers performed six 5-min sub-maximal exercise bouts at the same low, moderate and high metabolic rates on 2 and 8% inclines, while roller skiing on a treadmill employing the G3 skating technique. The work rate was calculated as work against gravity and friction, whereas the energetic equivalent of VO2 was taken as the metabolic rate. Gross efficiency was defined as work rate divided by metabolic rate. Kinematic parameters were analyzed in three dimensions. At the same metabolic rate, the work rate, cycle rate, work per cycle and relative duration of propulsive phases during a cycle of movement were all higher on the 8% than on the 2% incline at all speeds (all P < 0.05). At similar work rates, gross efficiency was greater on the 8% incline (P < 0.05). In conclusion, these elite skiers consistently demonstrated higher work rates on the 8% incline. To achieve the higher work rates on the steeper incline, these elite skiers employed higher cycle rates and performed more work per cycle, in association with a longer relative propulsive phase. © 2011 Springer-Verlag.
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77. |
- Sandbakk, Oyvind, et al.
(author)
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The physiological and biomechanical contributions of poling to roller ski skating
- 2013
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In: European Journal of Applied Physiology. - : Springer Science and Business Media LLC. - 1439-6319 .- 1439-6327. ; 113:8, s. 1979-1987
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Journal article (peer-reviewed)abstract
- Poling is considered to make a significant contribution to cross-country skiing with the skating technique. To better understand this contribution, the current investigation compared roller ski skating on a treadmill with the so-called G3 skating technique with (G3-P) and without poling (G3-NP). Seven male elite skiers performed 5-min submaximal tests at 8, 12, and 15 km h(-1), as well as an incremental test to exhaustion with both techniques on a 5 % incline. Ventilatory variables were assessed by open-circuit indirect calorimetry and three-dimensional kinematics analyzed using the Qualisys Pro Reflex system. G3-P was associated with approximately 15 % higher peak velocity and 10 % higher peak oxygen uptake than G3-NP in the incremental test (both P < 0.01). All ventilatory variables, as well as heart rate and blood lactate concentration were lower with G3-P as compared to G3-NP at 12 and 15 km h(-1) (all P < 0.01). Gross efficiency (i.e., the ratio of work rate to metabolic rate) at 12 km h(-1) was higher in G3-P (14.9 %) than G3-NP (13.5 %) (P < 0.01). Moreover, with G3-P cycle time and length were both 30 % longer, with correspondingly reduced cycle rates (all P < 0.01). In addition, the ski gliding and swing phases were longer and the angle between the skis smaller with G3-P (both P < 0.01), whereas the push-off time was independent of technique and velocity. Taken together, these results indicate that poling makes an important contribution to propulsion and velocity during ski skating, specifically by enhancing peak oxygen uptake, skiing efficiency and associated biomechanical variables.
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78. |
- Sandbakk, Øyvind, et al.
(author)
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Analysis of a sprint ski race and associated laboratory determinants of world-class performance
- 2011
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In: European Journal of Applied Physiology. - : Springer Science and Business Media LLC. - 1439-6319 .- 1439-6327. ; 111:6, s. 947-957
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Journal article (peer-reviewed)abstract
- This investigation was designed to analyze the time-trial (STT) in an international cross-country skiing sprint skating competition for (1) overall STT performance and relative contributions of time spent in different sections of terrain, (2) work rate and kinematics on uphill terrain, and (3) relationships to physiological and kinematic parameters while treadmill roller ski skating. Total time and times in nine different sections of terrain by 12 world-class male sprint skiers were determined, along with work rate and kinematics for one specific uphill section. In addition, peak oxygen uptake (VO2peak), gross efficiency (GE), peak speed (Vpeak), and kinematics in skating were measured. Times on the last two uphill and two final flat sections were correlated to overall STT performance (r = ~-0.80, P < 0.001). For the selected uphill section, speed was correlated to cycle length (r = -0.75, P < 0.01) and the estimated work rate was approximately 160% of peak aerobic power. VO2peak, GE, Vpeak, and peak cycle length were all correlated to STT performance (r = ~-0.85, P < 0.001). More specifically, VO2peak and GE were correlated to the last two uphill and two final flat section times, whereas Vpeak and peak cycle length were correlated to times in all uphill, flat, and curved sections except for the initial section (r = ~-0.80, P < 0.01). Performances on uphill and flat terrain in the latter part were the most significant determinants of overall STT performance. Peak oxygen uptake, efficiency, peak speed, and peak cycle length were strongly correlated to overall STT performance, as well as to performance in different sections of the race.
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79. |
- Sandbakk, Øyvind, et al.
(author)
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Metabolic Rate and Gross Efficiency at High Work Rates in World Class and National Level Sprint Skiers
- 2010
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In: European Journal of Applied Physiology. - : Springer. - 1439-6319 .- 1439-6327. ; 109:3, s. 473-481
-
Journal article (peer-reviewed)abstract
- The present study investigated metabolic rate (MR) and gross efficiency (GE) at moderate and high work rates, and the relationships to gross kinematics and physical characteristics in elite cross-country skiers. Eight world class (WC) and eight national level (NL) male sprint cross-country skiers performed three 5-min stages using the skating G3 technique, whilst roller skiing on a treadmill. GE was calculated by dividing work rate by MR. Work rate was calculated as the sum of power against gravity and frictional rolling forces. Metabolic rate was calculated using gas exchange and blood lactate values. Gross kinematics, i.e. cycle length (CL) and cycle rate (CR), were measured by video analysis. Furthermore, the skiers were tested for time to exhaustion (TTE), peak oxygen uptake (VO2peak), and maximal speed (Vmax) on the treadmill, and maximal strength in the laboratory. Individual performance level in sprint skating was determined by FIS points. WC skiers did not differ in aerobic MR, but showed lower anaerobic MR and higher GE than NL skiers at a given speed (all P < 0.05). Moreover, WC skiers skated with longer CL and had higher Vmax and TTE (all P < 0.05). In conclusion, the present study shows that WC skiers are more efficient than NL skiers, and it is proposed that this might be due to a better technique and to technique-specific power.
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80. |
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81. |
- Sjogaard, Gisela, et al.
(author)
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Muscle oxygenation and glycolysis in females with trapezius myalgia during stress and repetitive work using microdialysis and NIRS
- 2010
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In: EUROPEAN JOURNAL OF APPLIED PHYSIOLOGY. - : Springer Science and Business Media LLC. - 1439-6319 .- 1439-6327. ; 108:4, s. 657-669
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Journal article (peer-reviewed)abstract
- The aim of this investigation was to study female workers active in the labour market for differences between those with trapezius myalgia (MYA) and without (CON) during repetitive pegboard (PEG) and stress (STR) tasks regarding (1) relative muscle load, (2) trapezius muscle blood flow, (3) metabolite accumulation, (4) oxygenation, and (5) pain development. Among 812 female employees (age 30-60 years) at 7 companies with high prevalence of neck/shoulder complaints, clinical examination identified 43 MYA and 19 CON. At rest, during PEG, and STR the trapezius muscle was measured using (1) EMG and MMG, (2) microdialysis, and (3) NIRS. Further, subjective pain ratings were scored (VAS). EMGrms in %MVE (Maximal Voluntary EMG-activity), was significantly higher among MYA than CON during PEG (11.74 +/- A 9.09 vs. 7.42 +/- A 5.56%MVE) and STR (5.47 +/- A 5.00 vs. 3.28 +/- A 1.94%MVE). MANOVA showed a group and time effect regarding data from the microdialysis: for MYA versus CON group differences demonstrated lower muscle blood flow and higher lactate and pyruvate concentrations. Potassium and glucose only showed time effects. NIRS showed similar initial decreases in oxygenation with PEG in both groups, but only in CON a significant increase back to baseline during PEG. VAS score at rest was highest among MYA and increased during PEG, but not for CON. The results showed significant differences between CON and MYA regarding muscle metabolism at rest and with PEG and STR. Higher relative muscle load during PEG and STR, insufficient muscle blood flow and oxygenation may account for the higher lactate, pyruvate and pain responses among MYA versus CON.
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82. |
- Sperlich, Billy, et al.
(author)
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Biomechanical, cardiorespiratory, metabolic and perceived responses to electrically assisted cycling.
- 2012
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In: European Journal of Applied Physiology. - : Springer. - 1439-6319 .- 1439-6327. ; 112:12, s. 4015-4025
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Journal article (peer-reviewed)abstract
- The aims of the present study were to characterize the effects of cycling in varying terrain with the assistance of an electric motor with respect to (1) power output, velocity, and electromyography (EMG) signals; (2) cardiorespiratory parameters; (3) energy expenditure (EE); (4) rate of perceived exertion (RPE) and enjoyment and to compare these effects with those of non-assisted cycling. Eight sedentary women (age: 38 ± 15 years, BMI: 25.3 ± 2.1 kg m(-2)) cycled 9.5 km on varying terrain (change in elevation: 102 m, maximum incline: 5.8 %) at their own pace, once with and once without motorized assistance, in randomized order. With electrical assistance, the mean power output (-29 %); EMG patterns of the m. biceps femoris (-49 %), m. vastus lateralis (-33 %), m. vastus medialis (-37 %), and m. gastrocnemius medialis (-29 %); heart rate (-29.1 %); oxygen uptake (-33.0 %); respiratory exchange ratio (-9.0 %); and EE (-36.5 %) were all lower, whereas the mean cycling speed was higher (P < 0.05) than that without such assistance. In addition, following assisted exercise the mean blood lactate concentration and RPE were lower (P < 0.05) and ratings of enjoyment higher (P < 0.05). Moreover, motorized cycling was associated with (1) lower EMG with higher power output and speed; (2) less cardiorespiratory and metabolic effort; (3) lower respiratory exchange ratio; (4) lower RPE with more enjoyment; and (5) sufficient EE, according to present standards, to provide health benefits. Thus, electrically assisted cycling may represent an innovative approach to persuading reluctant sedentary women to exercise.
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83. |
- Sperlich, Billy, et al.
(author)
-
High-intensity interval training improves VO2peak, maximal lactate accumulation, time trial and competition performance in 9–11-year-old swimmers
- 2010
-
In: European Journal of Applied Physiology. - : Springer Science and Business Media LLC. - 1439-6319 .- 1439-6327. ; 110:5, s. 1029-1036
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Journal article (peer-reviewed)abstract
- Training volume in swimming is usually very high when compared to the relatively short competition time. High-intensity interval training (HIIT) has been demonstrated to improve performance in a relatively short training period. The main purpose of the present study was to examine the effects of a 5-week HIIT versus high-volume training (HVT) in 9-11-year-old swimmers on competition performance, 100 and 2,000 m time (T100 m and T2,000 m), VO2peak and rate of maximal lactate accumulation (Lacmax). In a 5-week crossover study, 26 competitive swimmers with a mean (SD) age of 11.5 ± 1.4 years performed a training period of HIIT and HVT. Competition (P < 0.01; effect size = 0.48) and T2,000 m (P = 0.04; effect size = 0.21) performance increased following HIIT. No changes were found in T100 m (P = 0.20). Lacmax increased following HIIT (P < 0.01; effect size = 0.43) and decreased after HVT (P < 0.01; effect size = 0.51). VO2peak increased following both interventions (P < 0.05; effect sizes = 0.46-0.57). The increases in competition performance, T2,000 m, Lacmax and VO2peak following HIIT were achieved in significantly less training time (~2 h/week).
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84. |
- Sperlich, Billy, et al.
(author)
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Pre-exposure to hyperoxic air does not enhance power output during subsequent sprint cycling
- 2010
-
In: European Journal of Applied Physiology. - : Springer Science and Business Media LLC. - 1439-6319 .- 1439-6327. ; 110:2, s. 301-305
-
Journal article (peer-reviewed)abstract
- Previous studies have indicated that aerobic pathways contribute to 13-27% of the energy consumed during short-term (10-20-second) sprinting exercise. Accordingly, the present investigation was designed to test the hypothesis that prior breathing of oxygen-enriched air (FinO2=60%) would enhance power output and reduce fatigue during subsequent sprint cycling. Ten well-trained male cyclists (mean ± SD, age: 25±3 years, height: 186.1±6.9 cm, body mass: 79.1±8.2 kg, maximal oxygen uptake [VO2max]: 63.2±5.2 ml·kg-1·min-1) took 25 breaths of either hyperoxic (HE) or normoxic (NO) air before performing 15 sec of cycling at maximal exertion. During this performance, the maximal and mean power outputs were recorded. The concentration of lactate, pH, partial pressure of and saturation by oxygen, [H+] and base excess in arterial blood were assessed before and after the sprint. The maximal (1053±141 W for HE versus 1052±165 W for NO; P = 0.77) and mean power outputs (873±123 versus 876±147 W; P = 0.68) did not differ between the two conditions. The partial pressure of oxygen was approximately 2.3-fold higher after inhaling HE in comparison to NO, while lactate concentration, pH, [H+] and base excess (best P = 0.32) after sprinting were not influenced by exposure to HE. These findings suggest that the peak and mean power outputs of athletes performing short-term intense exercise cannot be improved by pre-exposure to oxygen-enriched air.
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85. |
- Sundblad, Patrik, et al.
(author)
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G tolerance and the vasoconstrictor reserve
- 2014
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In: European Journal of Applied Physiology. - : Springer Berlin/Heidelberg. - 1439-6319 .- 1439-6327. ; 114:12, s. 2521-2528
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Journal article (peer-reviewed)abstract
- Because leg arterial stiffness is higher in subjects with high G tolerance, we hypothesized that subjects with high G tolerance would have larger capacity for vasoconstriction. Sixteen subjects, eight with high and eight with low G tolerance (H and L group, respectively), were exposed to a cold pressor test (CPT) in supine and upright posture. Heart rate (HR), mean arterial pressure (MAP) and cardiac output (CO) were measured, and total peripheral resistance (TPR) and stroke volume (SV) were calculated. In the supine position, CPT increased TPR more in the H group; 31 +/- A 18 % than in the L group; 11 +/- A 7 % (p < 0.05). The L group had larger increases in CO than the H group; 17 +/- A 16 vs. 3.4 +/- A 7 % (p = 0.06). In the upright position, the H group had a larger MAP response to CPT than the L group; 26 +/- A 14 vs. 14 +/- A 7 % (p = 0.06). The H group, but not the L group, had significant increases in TPR whereas the L group had significant increases in CO and SV. In response to CPT, the high G tolerance group elevated MAP by increasing TPR, whereas the low G tolerance group showed a dependency on increased CO. The H group seemed to have a larger vasoconstrictor reserve. The results further suggest that vasoconstrictor reserve capacity could constitute the link between the recent finding that indicates a relationship between G tolerance and arterial distensibility in the legs.
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86. |
- Terzis, Gerasimos, et al.
(author)
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The degree of p70(S6k) and S6 phosphorylation in human skeletal muscle in response to resistance exercise depends on the training volume.
- 2010
-
In: European Journal of Applied Physiology. - : Springer Science and Business Media LLC. - 1439-6319 .- 1439-6327. ; 110:4, s. 835-43
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Journal article (peer-reviewed)abstract
- Regular performance of resistance exercise induces an increase in skeletal muscle mass, however, the molecular mechanisms underlying this effect are not yet fully understood. The purpose of the present investigation was to examine acute changes in molecular signalling in response to resistance exercise involving different training volumes. Eight untrained male subjects carried out one, three and five sets of 6 repetition maximum (RM) in leg press exercise in a random order. Muscle biopsies were taken from the vastus lateralis both prior to and 30 min after each training session and the effect on protein signalling was studied. Phosphorylation of Akt was not altered significantly after any of the training protocols, whereas that of the mammalian target of rapamycin was enhanced to a similar extent by training at all three volumes. The phosphorylation of p70S6 kinase (p70(S6k)) was elevated threefold after 3 × 6 RM and sixfold after 5 × 6 RM, while the phosphorylation of S6 was increased 30- and 55-fold following the 3 × 6 RM and 5 × 6 RM exercises, respectively. Moreover, the level of the phosphorylated form of the gamma isoform of p38 MAPK was enhanced three to fourfold following each of the three protocols, whereas phosphorylation of ERK1/2 was unchanged 30 min following exercise. These findings indicate that when exercise is performed in a fasted state, the increase in phosphorylation of signalling molecules such as p70(S6k) and the S6 ribosomal protein in human muscle depends on the exercise volume.
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87. |
- Wallberg, Linnea, et al.
(author)
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Plasma IL-6 concentration during ultra-endurance exercise
- 2011
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In: European Journal of Applied Physiology. - : Springer Science and Business Media LLC. - 1439-6319 .- 1439-6327. ; 111:6, s. 1081-1088
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Journal article (peer-reviewed)abstract
- Interleukin 6 (IL-6) response was studied during two ultra endurance events – one laboratory 24 h protocol (9 men) with exercise intensity set to 60 % of VO2max and one Adventure Race over 6 days (12 men/6 women) with a self-selected race pace, including rests, of about 38 % of VO2max. In the 24 h protocol IL-6 level was elevated from 0.76 ± 0.48 pg mL-1 at rest to 7.16 ± 2.70 pg mL-1 at 6 h, and increased further to 10.58 ± 1.04 pg mL-1 at 12 h, but remained thereafter unchanged at 24 h, (10.89±0.36 pg mL-1). All participants had nearly identical values at 12 and 24 h, supporting intensity as main determinant in the IL-6 response since exercise duration did not increase IL-6 level after 12 h. Possible confounding factors do not seem to influence the IL-6 concentration during the longer races (>12h), but might very well do so during shorter exercise bouts. In the 6-day race IL-6 increased from rest to 24 h, but thereafter there was no change in plasma IL-6 value until the end of the race (140 h). There was no elevation of TNF-α in any of the protocols, suggesting that the competitors were free from systemic inflammation. During endurance exercise lasting >12 h intensity and not duration is the main determinant of the IL-6 response, while during shorter exercise bouts both intensity and duration contribute to the accumulation of IL-6 in plasma.
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88. |
- Wallén, Martin Benka, et al.
(author)
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Possibilities and limitations of the polar RS800 in measuring heart rate variability at rest
- 2012
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In: European Journal of Applied Physiology. - : Springer Science and Business Media LLC. - 1439-6319 .- 1439-6327. ; 112:3, s. 1153-1165
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Journal article (peer-reviewed)abstract
- A growing trend among clinical studies is the use of heart rate monitors (HRMs) for assessment of heart rate variability (HRV). These instruments offer a convenient alternative to traditional electrocardiographs (ECGs) for recording and processing of R-R data. Reports on the validity of such systems are, however, conflicting. This study aimed to assess the validity of a commercial HRM on a large study sample, with emphasis on gender and age. Simultaneous recordings of R-R intervals were conducted with the Polar RS800 HRM and a 3-lead ECG on 341 individuals. Data editing was performed with individually designated software for each instrument. Agreement on SDNN, RMSSD, and HF- and LF power was assessed with intraclass correlations (ICCs), standard errors of measurement (SEMs) and Bland and Altman plots. The HRM was not able to identify 18 observations with non-sinus beats. For men, agreement between instruments ranged from good to excellent (ICC >= 0.8) on all HRV measures, and SEMs were generally small. For women the results were weaker, with unacceptable agreement between instruments on SDNN. Women over 60 years did not reach a critical ICC value of 0.75 on any of the HRV measures. Bland and Altman plots demonstrated that the RS800 generally overestimated HRV, and that uncertainty increased with higher values. Since the Polar system did not identify errors satisfactorily, or return valid values of HRV for certain groups, it is concluded that, whenever possible, traditional ECGs should be used for both gathering and editing of HRV data.
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89. |
- Wernbom, Mathias, 1968, et al.
(author)
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Acute low-load resistance exercise with and without blood flow restriction increased protein signalling and number of satellite cells in human skeletal muscle.
- 2013
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In: European journal of applied physiology. - : Springer Science and Business Media LLC. - 1439-6327 .- 1439-6319. ; 113:12, s. 2953-2965
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Journal article (peer-reviewed)abstract
- Purpose To investigate hypertrophic signalling after a single bout of low-load resistance exercise with and without blood flow restriction (BFR). Methods Seven subjects performed unilateral knee extensions at 30 % of their one repetition maximum. The subjects performed five sets to failure with BFR on one leg, and then repeated the same amount of work with the other leg without BFR. Biopsies were obtained from m. vastus lateralis before and 1, 24 and 48 h after exercise. Results At 1-h post-exercise, phosphorylation of p70S6KThr389 and p38MAPKThr180/Tyr182 was elevated in the BFR leg, but not in the free-flow leg. Phospho-p70S6KThr389 was elevated three- to fourfold in both legs at 24-h post-exercise, but back to baseline at 48 h. The number of visible satellite cells (SCs) per muscle fibre was increased for all post-exercise time points and in both legs (33–53 %). The proportion of SCs with cytoplasmic extensions was elevated at 1-h post in the BFR leg and the number of SCs positive for myogenin and/or MyoD was increased at 1- and 24-h post-exercise for both legs combined. Conclusion Acute low-load resistance exercise with BFR resulted in early (1 h) and late (24 h) enhancement of phospho-p70S6KThr389, an early response of p38MAPK, and an increased number of SCs per muscle fibre. Enhanced phospho-p70S6KThr389 at 24-h post-exercise and increases in SC numbers were seen also in the free-flow leg. Implications of these findings for the hypertrophic effects of fatiguing low-load resistance exercise with and without BFR are discussed.
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90. |
- Wernbom, Mathias, 1968, et al.
(author)
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Contractile function and sarcolemmal permeability after acute low-load resistance exercise with blood flow restriction
- 2012
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In: European Journal of Applied Physiology. - : Springer Science and Business Media LLC. - 1439-6319 .- 1439-6327. ; 112:6, s. 2051-2063
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Journal article (peer-reviewed)abstract
- Conflicting findings have been reported regarding muscle damage with low-intensity resistance exercise with blood flow restriction (BFR) by pressure cuffs. This study investigated muscle function and muscle fibre morphology after a single bout of low-intensity resistance exercise with and without BFR. Twelve physically active subjects performed unilateral knee extensions at 30% of their one repetition maximum (1RM), with partial BFR on one leg and the other leg without occlusion. With the BFR leg, five sets were performed to concentric torque failure, and the free-flow leg repeated the exact same number of repetitions and sets. Biopsies were obtained from vastus lateralis before and 1, 24 and 48 h after exercise. Maximum isometric torque (MVC) and resting tension were measured before and after exercise and at 4, 24, 48, 72, 96 and 168 h post-exercise. The results demonstrated significant decrements in MVC (lasting a parts per thousand yen48 h) and delayed onset muscle soreness in both legs, and increased resting tension for the occluded leg both acutely and at 24 h post-exercise. The percentage of muscle fibres showing elevated intracellular staining of the plasma protein tetranectin, a marker for sarcolemmal permeability, was significantly increased from 9% before exercise to 27-38% at 1, 24 and 48 h post-exercise for the BFR leg. The changes in the free-flow leg were significant only at 24 h (19%). We conclude that an acute bout of low-load resistance exercise with BFR resulted in changes suggesting muscle damage, which may have implications both for safety aspects and for the training stimulus with BFR exercise.
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91. |
- Westerterp, KR, et al.
(author)
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New editors take over
- 2013
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In: European journal of applied physiology. - : Springer Science and Business Media LLC. - 1439-6327 .- 1439-6319. ; 113:4, s. 823-823
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Journal article (other academic/artistic)
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92. |
- Wichardt, Emma, et al.
(author)
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Rhabdomyolysis/myoglobinemia and NSAID during 48-hours ultra-endurance exercise (adventure racing)
- 2011
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In: European Journal of Applied Physiology. - : Springer Science and Business Media LLC. - 1439-6319 .- 1439-6327. ; 111:7, s. 1541-1544
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Journal article (peer-reviewed)abstract
- Purpose: To determine if rhabdomyolysis with myoglobinemia exists during a 48+ hour adventure race and if there is a correlation with NSAID use, race time and perceived pain or exertion. Method: Blood samples for analyses of myoglobin (Mb) were collected, and perception of exertion and pain registered on the Borg-RPE and CR scales, from 20 subjects (3 female, 17 male) Pre, Mid and Post race. Subjects were asked about NSAID use at each sampling and within 12 hours pre race. Result: A significant rise in Mb was observed throughout the race, with the NSAID group (n=6) having significantly lower Mb-Post than the no-NSAID group (n=14). High Mb-Pre and Post correlated to shorter race time and high Mb-Pre to lower Pain-Post. Race time also correlated to NSAID use, with the NSAID group having significantly longer race time than the no-NSAID group. Conclusion: Rhabdomyolysis with myoglobinemia, which might be reduced with NSAID use, exists during a 48+ hour adventure race. Indications that high Mb-levels correlate with shorter race time and less pain, and the reasons for the NSAID groups longer race time, need further investigation.
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93. |
- Yogev, Daniel, et al.
(author)
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Effect of 21 days of horizontal bed rest on behavioural thermoregulation
- 2010
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In: European Journal of Applied Physiology. - : Springer Science and Business Media LLC. - 1439-6319 .- 1439-6327. ; 108:2, s. 281-288
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Journal article (peer-reviewed)abstract
- The present study investigated the effect of 21 days of horizontal bed rest on cutaneous cold and warm sensitivity, and on behavioural temperature regulation. Healthy male subjects (N = 10) were accommodated in a hospital ward for the duration of the study and were under 24-h medical care. All activities (eating, drinking, hygiene, etc.) were conducted in the horizontal position. On the 1st and 22nd day of bed rest, cutaneous temperature sensitivity was tested by applying cold and warm stimuli of different magnitudes to the volar region of the forearm via a Peltier element thermode. Behavioural thermoregulation was assessed by having the subjects regulate the temperature of the water within a water-perfused suit (T (wps)) they were wearing. A control unit established a sinusoidal change in T (wps), such that it varied from 27 to 42A degrees C. The subjects could alter the direction of the change of T (wps), when they perceived it as thermally uncomfortable. The magnitude of the oscillations towards the end of the trial was assumed to represent the upper and lower boundaries of the thermal comfort zone. The cutaneous threshold for detecting cold stimulus decreased (P < 0.05) from 1.6 (1.0)A degrees C on day 1 to 1.0 (0.3)A degrees C on day 22. No effect was observed on the ability to detect warm stimuli or on the regulated T (wps). We conclude that although cold sensitivity increased after bed rest, it was not of sufficient magnitude to cause any alteration in behavioural thermoregulatory responses.
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94. |
- Yung, Marcus, et al.
(author)
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Variation of Force Amplitude and its Effects on Local Fatigue
- 2012
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In: European Journal of Applied Physiology. - : Springer Science and Business Media LLC. - 1439-6319 .- 1439-6327. ; 112:11, s. 3865-3879
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Journal article (peer-reviewed)abstract
- Trends in industry are leaning towards stereotyped jobs with low workloads. Physical variation is an intervention to reduce fatigue and potentially musculoskeletal disorders in such jobs. Controlled laboratory studies have provided insight into the effectiveness of physical variation but very few have been devoted to intermittent activity without muscular rest as a component. This study was undertaken to determine whether the inclusion of muscular rest would result in physiological responses beyond those composed of varying non-zero forces. Five isometric contraction patterns with the same mean amplitude (15% maximum voluntary contraction, MVC), cycle time (6 seconds), and duty cycle (50%) were compared using multiple biophysical approaches. In exercise, sustained (15%Sust) and intermittent contractions including zero force (0%-30%Int) differed significantly in 19 of 27 response variables. Contractions varying by half the mean force (7.5%-22.5%Int) led to 8 and 7 measured responses that were significantly different from 0%-30%Int and 15%Sus, respectively. A sinusoidal condition (0%-30%Sine) resulted in 2 variables that were significantly different from 0%-30%Int and 16 different from 15%Sus. Finally, 10 response variables suggested that varying forces with 1% as the lower contraction level was significantly less fatiguing than 15%Sus while no responses were significantly different from 0%-30%Int. Sustained contractions led to decreased twitch force 24 hours post-exercise whereas intermittent contractions recovered within 60 minutes. This suggests that time varying force may be a useful intervention to reduce local fatigue in workers performing low-load tasks and that rest per se did not seem to cause any extraordinary effects.
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