| 1. |
- Beaven, C. Martyn, 1977-, et al.
(author)
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Effects of caffeine and carbohydrate mouth rinses on repeated sprint performance
- 2013
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In: Applied Physiology, Nutrition and Metabolism. - : Canadian Science Publishing. - 1715-5312 .- 1715-5320. ; 38:6, s. 633-637
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Journal article (peer-reviewed)abstract
- Introduction: Our purpose was to examine the effectiveness of carbohydrate and caffeine mouth rinses on enhancing repeated sprint ability. Previously, beneficial effects of a carbohydrate mouth rinse (without ingestion) on endurance performance have been related to changes in brain activity. Caffeine ingestion has also demonstrated positive effects on sprint performance. However, the effects of carbohydrate or caffeine mouth rinses on intermittent sprints have not previously been examined. Methods: Twelve males performed 5 x 6 s sprints interspersed by 24 s of active recovery on a cycle ergometer. Twenty-five ml of either a non-caloric placebo, 6% glucose, or 1.2% caffeine solution was rinsed in the mouth for 5 s prior to each sprint in a double-blinded and balanced, cross-over design. Post-exercise maximal heart rate and perceived exertion were recorded along with power measures. A second experiment compared a combined caffeine-carbohydrate rinse with carbohydrate-only. Results: Compared to the placebo mouth rinse, carbohydrate substantially increased Sprint 1 peak power (22.1 ±19.5 W; ES: 0.81), and both caffeine (26.9 ±26.9 W; ES: 0.71) and carbohydrate (39.1 ±25.8 W; ES: 1.08) improved mean power in Sprint 1. Experiment 2 demonstrated that a combination of caffeine and carbohydrate improved Sprint 1 power production compared to carbohydrate alone (36.0 ±37.3 W; ES: 0.81). Conclusions: Carbohydrate and/or caffeine mouth rinses may rapidly enhance power production which could have benefits for specific short sprint exercise performance. The ability of a mouth rinse intervention to rapidly improve maximal exercise performance in the absence of fatigue suggests a central mechanism.
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| 2. |
- Beaven, Christopher Martyn, 1977-
(author)
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Intermittent lower-limb occlusion enhances recovery after strenuous exercise
- 2012
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In: Applied Physiology, Nutrition and Metabolism. - : Canadian Science Publishing. - 1715-5312 .- 1715-5320. ; 37:6, s. 1132-1139
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Journal article (peer-reviewed)abstract
- Repeated cycles of vascular occlusion followed by reperfusion initiate a protective mechanism that acts to mitigate future cell injury. Such ischemic episodes are known to improve vasodilation, oxygen utilization, muscle function, and have been demonstrated to enhance exercise performance. Thus, the use of occlusion cuffs represents a novel intervention that may improve subsequent exercise performance. Fourteen participants performed an exercise protocol that involved lower-body strength and power tests followed by repeated sprints. Occlusion cuffs were then applied unilaterally (2 x 3-min per leg) with a pressure of either 220 (intervention) or 15 mm Hg (control). Participants immediately repeated the exercise protocol, and then again 24 h later. The intervention elicited delayed beneficial effects (24 h post-intervention) in the countermovement jump test with concentric (effect size (ES) = 0.36) and eccentric (ES = 0.26) velocity recovering more rapidly compared with the c! ontrol. There were also small beneficial effects on 10- and 40-m sprint times. In the squat jump test there were delayed beneficial effects of occlusion on eccentric power (ES = 1.38), acceleration (ES = 1.24), and an immediate positive effect on jump height (ES = 0.61). Thus, specific beneficial effects on recovery of power production and sprint performance were observed both immediately and 24 h after intermittent unilateral occlusion was applied to each leg.
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| 3. |
- Buckley, John P., et al.
(author)
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Borg's scales in strength training; from theory to practice in young and older adults
- 2011
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In: Applied Physiology, Nutrition and Metabolism. - 1715-5312 .- 1715-5320. ; 36:5, s. 682-692
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Journal article (peer-reviewed)abstract
- This study is the first to apply Borg's psychophysical equation to measuring responses to strength training with weights machines. Theoretical constructs of Borg's scales were assessed in younger and older adults to estimate the appropriate load and number of repetitions required to meet recommended practice guidelines. A younger group (YG; 20 males, 20 females; aged 19-38 years) and older group (OG; 13 males, 13 females; aged 50-75 years) participated in 3 experiments. Experiment 1: YG performed 2-repetitions of incremented loads during triceps-elbow extensions and knee extensions to level 7 on Borg's CR10 Scale. Experiment 2: YG (n = 16) then performed 12-repetitions at the loads from experiement 1 that elicited CR10 ratings 1.5, 3.0, and 5.0. Experiment 3: OG performed 15-repetitions of lat-pull and leg press at 15-repetition maximum (RM) load. In experiments 2 and 3, CR10 or Borg RPE were measured every 2 repetitions. Experiment 1 revealed classic psychophysical response growth exponents between 1.1 and 1.8, which were greater in arms than legs (p < 0.001) and in females (p < 0.001). Theoretical estimates of 1RM were derived from the growth curves for the weights eliciting CR10 ratings of 1.5, 3, and 5. CR10 ratings of 3 to 6 fell within estimates of 40%-70% 1RM. Experiments 2 and 3 revealed, for constant load exercise over time (12 and 15 repetitions) from an initial CR10 rating of 4 to 6, a linear increase of 1 scale point for every 3 to 4 repetitions. In conclusion, Borg's equation has been used to set theoretical estimates of a %1RM. Relevant to current practice guidelines was the ability to set appropriate loads in relation to performing recommended numbers of repetitions (e. g., if the CR10 rating is >6 after 2 repetitions, the weight is likely be too heavy to complete 12 to 15 repetitions).
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| 4. |
- Debevec, Tadej, et al.
(author)
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Whole body and regional body composition changes following 10-day hypoxic confinement and unloading-inactivity
- 2014
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In: Applied Physiology, Nutrition and Metabolism. - : Canadian Science Publishing. - 1715-5312 .- 1715-5320. ; 39:3, s. 386-395
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Journal article (peer-reviewed)abstract
- Future planetary habitats will expose inhabitants to both reduced gravity and hypoxia. This study investigated the effects of short-term unloading and normobaric hypoxia on whole body and regional body composition (BC). Eleven healthy, recreationally active, male participants with a mean (SD) age of 24 (2) years and body mass index of 22.4 (3.2) kg.m(-2) completed the following 3 10-day campaigns in a randomised, cross-over designed protocol: (i) hypoxic ambulatory confinement (HAMB; FIO2 = 0.147 (0.008); PIO2 = 93.8 (0.9) mm Hg), (ii) hypoxic bed rest (HBR; FIO2 = 0.147 (0.008); PIO2 = 93.8 (0.9) mm Hg), and (iii) normoxic bed rest (NBR; FIO2 = 0.209; PIO2 = 133.5 (0.7) mmHg). Nutritional requirements were individually precalculated and the actual intake was monitored throughout the study protocol. Body mass, whole body, and regional BC were assessed before and after the campaigns using dual-energy X-ray absorptiometry. The calculated daily targeted energy intake values were 2071 (170) kcal for HBR and NBR and 2417 (200) kcal for HAMB. In both HBR and NBR campaigns the actual energy intake was within the targeted level, whereas in the HAMB the intake was lower than targeted (-8%, p < 0.05). Body mass significantly decreased in all 3 campaigns (-2.1%, -2.8%, and -2.0% for HAMB, HBR, and NBR, respectively; p < 0.05), secondary to a significant decrease in lean mass (-3.8%, -3.8%, -4.3% for HAMB, HBR, and NBR, respectively; p < 0.05) along with a slight, albeit not significant, increase in fat mass. The same trend was observed in the regional BC regardless of the region and the campaign. These results demonstrate that, hypoxia per se, does not seem to alter whole body and regional BC during short-term bed rest.
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| 5. |
- Keramidas, Michail E., et al.
(author)
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Prolonged physical inactivity leads to a drop in toe skin temperature during local cold stress
- 2014
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In: Applied Physiology, Nutrition and Metabolism. - : Canadian Science Publishing. - 1715-5312 .- 1715-5320. ; 39:3, s. 369-374
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Journal article (peer-reviewed)abstract
- The purpose was to examine the effects of a prolonged period of recumbency on the toe temperature responses during cold-water foot immersion. Ten healthy males underwent 35 days of horizontal bed rest. The right foot of the subjects was assigned as the experimental (EXP) foot. To prevent bed rest-induced vascular deconditioning in the left control foot (CON), a sub-atmospheric vascular pressure countermeasure regimen was applied on the left lower leg for 4 x 10 min every second day. On the first (BR-1) and the last (BR-35) day of the bed rest, subjects performed two 30 min foot immersion tests in 8 degrees C water, one with the EXP foot and the other with the CON foot. The tests were conducted in counter-balanced order and separated by at least a 15 min interval. At BR-35, the average skin temperature of the EXP foot was lower than at BR-1 (-0.8 degrees C; P = 0.05), a drop that was especially pronounced in the big toe (-1.6 degrees C; P = 0.05). In the CON foot, the average skin temperature decreased by 0.6 degrees C in BR-35, albeit the reduction was not statistically significant (P = 0.16). Moreover, the pressure countermeasure regimen ameliorated immersion-induced thermal discomfort for the CON foot (P = 0.05). Present findings suggest that severe physical inactivity exaggerates the drop in toe skin temperature during local cold stress, and thus might constitute a potential risk factor for local cold injury.
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| 6. |
- Krite Svanberg, Emilie, et al.
(author)
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Physiological influence of basic perturbations assessed by non-invasive optical techniques in humans
- 2011
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In: Applied Physiology, Nutrition and Metabolism. - : Canadian Science Publishing. - 1715-5320 .- 1715-5312. ; 36:6, s. 946-957
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Journal article (peer-reviewed)abstract
- New non-invasive techniques enabling frequent or continuous assessments of various pathophysiological conditions might be used to improve in-hospital outcome by enabling earlier and more reliable bedside detection of medical deterioration. In this preclinical study, three modern non-invasive optical techniques, laser Doppler imaging (LDI), near-infrared spectroscopy (NIRS), and tissue viability imaging (TVI), were all evaluated with respect to the influence of basic physiological perturbations (including local changes in arm positioning, skin temperature, and regional blood flow conditions) on quasi simultaneously obtained values of skin perfusion, muscle tissue oxygenation (StO2), and skin blood volume, recorded in eighteen healthy volunteers. Skin perfusion measured by LDI responded prominently to changes in positioning of the arm, whereas muscle StO2 measured by NIRS did not change significantly. Total haemoglobin count (HbT) measured by NIRS and blood volume estimated by TVI both increased significantly on lowering of the limb. On local cooling, the perfusion and blood volume were both found to increase considerably, while StO2 and HbT did not change. Local heating induced a more than 10-fold increase in skin perfusion and a small increase in blood volume. On progressive venoarterial occlusion, the perfusion, StO2, HbT, and blood volume values decreased, after transient increases in HbT and blood volume before full arterial occlusion occurred, and all values approached the baseline level on release of the occlusion with a slight overshoot of the StO2. The results obtained have potential bearing on future utilization of these non-invasive techniques in the management of severely injured and (or) critically ill patients.
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| 7. |
- McGawley, Kerry, 1978-, et al.
(author)
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Ingesting a high-dose carbohydrate solution during the cycle section of a simulated Olympic-distance triathlon improves subsequent run performance
- 2012
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In: Applied Physiology, Nutrition and Metabolism. - : Canadian Science Publishing. - 1715-5312 .- 1715-5320. ; 37:4, s. 664-671
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Journal article (peer-reviewed)abstract
- The well-established ergogenic benefit of ingesting carbohydrates during single-discipline endurance sports has only been tested once within an Olympic-distance (OD) triathlon. The aim of the present study was to compare the effect of ingesting a 2:1 maltodextrin/fructose solution with a placebo on simulated OD triathlon performance. Six male and 4 female amateur triathletes (age, 25 ± 7 years; body mass, 66.8 ± 9.2 kg; peak oxygen uptake, 4.2 ± 0.6 L·min–1) completed a 1500-m swim time-trial and an incremental cycle test to determine peak oxygen uptake before performing 2 simulated OD triathlons. The swim and cycle sections of the main trials were of fixed intensities, while the run section was completed as a time-trial. Two minutes prior to completing every quarter of the cycle participants consumed 202 ± 20 mL of either a solution containing 1.2 g·min–1 of maltodextrin plus 0.6 g·min–1 of fructose at 14.4% concentration (CHO) or a sugar-free, fruit-flavored drink (PLA). The time-trial was 4.0% ± 1.3% faster during the CHO versus PLA trial, with run times of 38:43 ± 1:10 min:s and 40:22 ± 1:18 min:s, respectively (p = 0.010). Blood glucose concentrations were higher in the CHO versus PLA trial (p < 0.001), while perceived stomach upset did not differ between trials (p = 0.555). The current findings show that a 2:1 maltodextrin/fructose solution (1.8 g·min–1 at 14.4%) ingested throughout the cycle section of a simulated OD triathlon enhances subsequent 10-km run performance in triathletes.
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| 8. |
- Moberg, Marcus, et al.
(author)
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Absence of leucine in an essential amino acid supplement reduces activation of mTORC1 signalling following resistance exercise in young females.
- 2014
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In: Applied Physiology, Nutrition and Metabolism. - : Canadian Science Publishing. - 1715-5312 .- 1715-5320. ; 39:2, s. 183-94
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Journal article (peer-reviewed)abstract
- The purpose of the study was to investigate the specific effect of leucine on mTORC1 signalling and amino acid metabolism in connection with resistance exercise. Comparisons were made between ingestion of supplements with and without leucine. Eight young women performed leg press exercise on 2 occasions. In randomized order they received either an aqueous solution of essential amino acids with leucine (EAA) or without leucine (EAA-Leu), given as small boluses throughout the experiment. Muscle biopsies were taken after an overnight fast before exercise and 1 and 3 h postexercise and samples of blood were taken repeatedly during the experiment. Plasma and muscle concentrations of leucine rose 60%-140% (p < 0.05) with EAA and fell 35%-45% (p < 0.05) with the EAA-Leu supplement. In the EAA-trial, plasma and muscle levels of tyrosine (not present in the supplement) and the sum of the EAA were 15%-25% (p < 0.05) lower during recovery. Phosphorylation of mTOR and p70S6k was elevated to a larger extent following 1 h of recovery with leucine in the supplement (120% vs. 49% (p < 0.05) and 59- vs. 8-fold (p < 0.05) for EAA and EAA-Leu, respectively). The levels of MAFbx and MuRF-1 mRNA and of the corresponding proteins were not significantly altered after 3 h recovery from exercise. In conclusion, the presence of leucine in the supplement enhances the stimulatory effect on mTORC1 signalling and reduces the level of tyrosine and the sum of the EAA in muscle and plasma, suggesting a stimulation of protein synthesis and (or) inhibition of breakdown, leading to improvement in net protein balance.
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| 9. |
- Mourot, L., et al.
(author)
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Impact of the initial classic section during a simulated cross-country skiing skiathlon on the cardiopulmonary responses during the subsequent period of skate skiing
- 2014
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In: Applied Physiology, Nutrition and Metabolism. - : Canadian Science Publishing. - 1715-5320 .- 1715-5312. ; 39:8, s. 911-919
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Journal article (peer-reviewed)abstract
- The aim of this study was to assess potential changes in the performance and cardiorespiratory responses of elite cross-country skiers following transition from the classic (CL) to the skating (SK) technique during a simulated skiathlon. Eight elite male skiers performed two 6 km (2 × 3 km) roller-skiing time trials on a treadmill at racing speed: one starting with the classic and switching to the skating technique (CL1-SK2) and another employing the skating technique throughout (SK1-SK2), with continuous monitoring of gas exchanges, heart rates, and kinematics (video). The overall performance times in the CL1-SK2 (21:12 ± 1:24) and SK1-SK2 (20:48 ± 2:00) trials were similar, and during the second section of each performance times and overall cardiopulmonary responses were also comparable. However, in comparison with SK1-SK2, the CL1-SK2 trial involved significantly higher increases in minute ventilation (VE, 89.8 ± 26.8 vs. 106.8 ± 17.6 L·min-1) and oxygen uptake (VO2; 3.1 ± 0.8 vs 3.5 ±0.5 L·min-1) 2 min after the transition as well as longer time constants for VE, VO2, and heart rate during the first 3 min after the transition. This higher cardiopulmonary exertion was associated with ~3% faster cycle rates. In conclusion, overall performance during the 2 time trials did not differ. The similar performance times during the second sections were achieved with comparable mean cardiopulmonary responses. However, the observation that during the initial 3-min post-transition following classic skiing cardiopulmonary responses and cycle rates were slightly higher supports the conclusion that an initial section of classic skiing exerts an impact on performance during a subsequent section of skate skiing.
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| 10. |
- Nielsen, Joachim, et al.
(author)
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Physiological aspects of the subcellular localization of glycogen in skeletal muscle
- 2013
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In: Applied Physiology, Nutrition and Metabolism. - : Canadian Science Publishing. - 1715-5312 .- 1715-5320. ; 38:2, s. 91-99
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Research review (peer-reviewed)abstract
- Glucose is stored in skeletal muscle fibers as glycogen, a branched-chain polymer observed in electron microscopy images as roughly spherical particles (known asβ-particles of 10-45 nm in diameter),which are distributed in distinct localizations within the myofibers and are physically associated with metabolic and scaffolding proteins. Although the subcellular localization of glycogen has been recognized for more than 40 years, the physiological role of the distinct localizations has received sparse attention. Recently, however, studies involving stereological, unbiased, quantitative methods have investigated the role and regulation of these distinct deposits of glycogen. In this report, we review the available literature regarding the subcellular localization of glycogen in skeletal muscle as investigated by electron microscopy studies and put this into perspective in terms of the architectural, topological, and dynamic organization of skeletal muscle fibers. In summary, the distribution of glycogen within skeletal muscle fibers has been shown to depend on the fiber phenotype, individual training status, short-term immobilization, and exercise and to influence both muscle contractility and fatigability. Based on all these data, the available literature strongly indicates that the subcellular localization of glycogen has to be taken into consideration to fully understand and appreciate the role and regulation of glycogen metabolism and signaling in skeletal muscle. A full understanding of these phenomena may prove vital in elucidating the mechanisms that integrate basic cellular events with changing glycogen content.
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