European journal of applied physiology
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Eur. J. Appl. Physiol. · Oct 2012
Randomized Controlled TrialExperimental muscle pain increases normalized variability of multidirectional forces during isometric contractions.
Pain elicits complex adaptations of motor strategy, leading to impairments in the generation and control of steady forces, which depend on muscle architecture. The present study used a cross-over design to assess the effects of muscle pain on the stability of multidirectional (task-related and tangential) forces during sustained dorsiflexions, elbow flexions, knee extensions, and plantarflexions. Fifteen healthy subjects performed series of isometric contractions (13-s duration, 2.5, 20, 50, 70% of maximal voluntary force) before, during, and after experimental muscle pain. ⋯ Experimental muscle pain elicited larger ranges of force angle during knee extensions and plantarflexions (P < 0.03) and higher normalized fluctuations of task-related (P < 0.02) and tangential forces (P < 0.03) compared with control assessments across force levels, while the mean force magnitudes, mean force angle and the level of muscle activity were non-significantly affected by pain. Increased multidirectional force fluctuations probably resulted from multiple mechanisms that, acting together, balanced the mean surface electromyography. Although pain adaptations are believed to aim at the protection of the painful site, the current results show that they result in impairments in steadiness of force.
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Eur. J. Appl. Physiol. · Sep 2012
Randomized Controlled TrialEffects of 29-h total sleep deprivation on local cold tolerance in humans.
To study the effects of a 29-h total sleep deprivation (TSD) on local cold tolerance, 10 healthy men immersed their right hand for 30 min in a 5°C water bath (CWI) after a 30-min rest period in a thermoneutral environment (Control), after a normal night (NN) and after a 29-h TSD. CWI was followed by a 30-min passive rewarming (Recovery). Finger 2 and 4 skin temperatures (Tfi2, Tfi4) and finger 2 cutaneous vascular conductance (CVC) were monitored to study cold-induced vasodilation (CIVD). ⋯ After TSD at Control and CWI, plasma endothelin levels were higher and negatively correlated with Tfi2, Tfi4 and CVC. However, no effect of TSD was found on the number and amplitude of CIVD and in Tre, HR, BP and catecholamines, for all periods. We concluded that TSD induced thermal and vascular changes in the hand which impair the local cold tolerance, suggesting that TSD increases the risk of local cold injuries.
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Eur. J. Appl. Physiol. · Sep 2012
Clinical TrialCharacterizing the profile of muscle deoxygenation during ramp incremental exercise in young men.
This study characterized the profile of near-infrared spectroscopy (NIRS)-derived muscle deoxygenation (Δ[HHb]) and the tissue oxygenation index (TOI) as a function of absolute (PO(ABS)) and normalized power output (%PO) or oxygen consumption (%VO(2)) during incremental cycling exercise. Eight men (24 ± 5 year) each performed two fatigue-limited ramp incremental cycling tests (20 W min(-1)), during which pulmonary VO(2), Δ[HHb] and TOI were measured continuously. Responses from the two tests were averaged and the TOI (%) and normalized Δ[HHb] (%Δ[HHb]) were plotted against %VO(2), %PO and PO(ABS). ⋯ In ~85% of cases, the corrected Akaike Information Criterion (AIC(C)) was smaller (suggesting one model favoured) for the 'double-linear' compared with the sigmoid regression for both %Δ[HHb] and TOI. Furthermore, the f ( 0 ) and A estimates from the sigmoid regressions of %Δ[HHb] yielded unrealistically large projected peak (f ( 0 ) + A) values (%VO(2p) 114.3 ± 17.5; %PO 113.3 ± 9.5; PO(ABS) 113.5 ± 9.8), suggesting that the sigmoid model does not accurately describe the underlying physiological responses in all subjects and thus may not be appropriate for comparative purposes. Alternatively, the present study proposes that the profile of %Δ[HHb] and TOI during ramp incremental exercise may be more accurately described as consisting of three distinct phases in which there is little adjustment early in the ramp, the predominant increase in %Δ[HHb] (decrease in TOI) is approximately linear and an approximately linear 'plateau' follows.
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Eur. J. Appl. Physiol. · Aug 2012
Randomized Controlled TrialVitamin D supplementation during exercise training does not alter inflammatory biomarkers in overweight and obese subjects.
The purpose of this study was to examine the effects of vitamin D supplementation on inflammatory biomarkers in overweight and obese adults participating in a progressive resistance exercise training program. Twenty-three (26.1 ± 4.7 years) overweight and obese (BMI 31.3 ± 3.2 kg/m2) adults were randomized into a double-blind vitamin D supplementation (Vit D 4,000 IU/day; female 5, male 5) or placebo (PL, female 7; male 6) intervention trial. Both groups performed 12 weeks (3 days/week) of progressive resistance exercise training (three sets of eight exercises) at 70-80% of one repetition maximum. ⋯ As expected, when PL and Vit D groups were combined, there was a significant correlation between percent body fat and CRP at baseline (r = 0.45, P = 0.04), and between serum 25OHD and CRP at 12 weeks (r = 0.49, P = 0.03). The PL group had a significant increase in 25 μg/ml LPS + polymixin B-stimulated TNFα production (P = 0.04), and both groups had a significant reduction in unstimulated TNFα production (P < 0.05) after the 12-week intervention. Vitamin D supplementation in healthy, overweight, and obese adults participating in a resistance training intervention did not augment exercise-induced changes in inflammatory biomarkers.
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Eur. J. Appl. Physiol. · Aug 2012
Warm-up effects on muscle oxygenation, metabolism and sprint cycling performance.
To investigate the effects of warm-up intensity on all-out sprint cycling performance, muscle oxygenation and metabolism, 8 trained male cyclists/triathletes undertook a 30-s sprint cycling test preceded by moderate, heavy or severe warm up and 10-min recovery. Muscle oxygenation was measured by near-infrared spectroscopy, with deoxyhaemoglobin ([HHb]) during the sprint analysed with monoexponential models with time delay. Aerobic, anaerobic-glycolytic and phosphocreatine energy provision to the sprint were estimated from oxygen uptake and lactate production. ⋯ The [HHb] kinetics during the sprint were not different among conditions, although the time delay before [HHb] increased was shorter for severe versus moderate warm up (mod. 5.8 ± 0.6, heavy 5.6 ± 0.9, severe 5.2 ± 0.7 s, P < 0.05). The severe warm up was without effect on estimated aerobic metabolism, but increased estimated phosphocreatine hydrolysis, the latter unable to compensate for the reduction in estimated anaerobic-glycolytic metabolism. It appears that despite all warm ups equally increasing muscle oxygenation, and indicators of marginally faster oxygen utilisation at the start of exercise following a severe-intensity warm up, other energy sources may not be able to fully compensate for a reduced glycolytic rate in sprint exercise with potential detrimental effects on performance.