This study aimed to examine the effects of wearing compression compared to classic elastic tights and conventional shorts (control trial) on oxygen cost and sensation responses during submaximal running exercise. In part I, aerobic energy cost was evaluated in six trained runners at 10, 12, 14, and 16 km x h(-1). In part II, the increase in energy cost over time (i. e., slow component expressed as difference in VO2 values between min 2 and end-exercise) was determined in six trained runners at a constant running pace corresponding to 80% of maximal VO2 for 15 min duration. All tests were performed on a 200-m indoor track with equivalent thermal stress conditions. VO2 was determined with a portable metabolic system (Cosmed K4b2, Rome, Italy) during all testing sessions. Runners were asked their ratings of perceived exertion (RPE) and perceptions for clothing sweating, comfort, and whole thermal sensations following each trial. Results showed in part I a significant lower energy cost only at 12 km x h(-1) by wearing compression and elastic tights compared to conventional shorts. During part II, wearing compression tights decreased significantly VO2 slow component by 26 and 36% compared to elastic tights and conventional shorts, respectively. There were no differences in sweating and comfort sensations, RPE, and for whole thermal sensation between clothing conditions in parts I and II. Wearing compression tights during running exercise may enhance overall circulation and decrease muscle oscillation to promote a lower energy expenditure at a given prolonged submaximal speed.

The purpose of the present study was to assess the reliability of metabolic parameters measured using 31 P magnetic resonance spectroscopy ( 31 P MRS) during two standardized rest-exerciserecovery protocols. Twelve healthy subjects performed the standardized protocols at two different intensities; i.e., a moderate intensity (MOD) repeated over a two-month period and heavy intensity (HEAVY) repeated over a year's time. Test-retest reliability was analyzed using coefficient of variation ( Key words: magnetic resonance spectroscopy; reliability; oxidative capacity; PCr kinetics; exercise Phosphorus-31 nuclear magnetic resonance spectroscopy ( 31 P-MRS) is now widely accepted as the "gold standard" method for noninvasive measurements of energy metabolism in exercising muscle. The analysis of changes in phosphorylated compounds concentrations and intracellular pH during rest-exercise-recovery protocols has provided significant advance in the understanding of underlying mechanisms of muscle energy production (1-4). Given the noninvasiveness of the method, 31 P-MRS enables repeated measurements and has been successfully used in a wide range of situations such as the assessment of therapeutic interventions in patients with metabolic disorders (5-7) and the characterization of training-induced metabolic changes (8 -11). More recently, the dynamics of phosphocreatine (PCr) has been used to evaluate the control of mitochondrial respiration in skeletal muscle (12) or the mechanism underlying the V O 2p slow component (13) typically observed during a high-intensity exercise; i.e., above the lactate threshold. In addition, the rate constant of postexercise recovery kinetics of [PCr] has been used as an index of mitochondrial function (14 -17). In addition to these traditional variables, more sophisticated analyses have been put forth in order to quantify the contribution of oxidative and anaerobic pathways to energy production in exercising muscle (2,18,19).Despite the widespread use of 31 P MRS for muscle energetics investigation, the reproducibility of the corresponding variables has been scarcely investigated. It has actually been investigated through repeated measurements performed 1 week (5) and 4 weeks apart (20). Bendahan et al. (5) reported a good reliability in metabolic parameters when investigated using analysis of variance (ANOVA). However, detection of systematic bias might have been affected by large random error between tests as suggested previously (21). observed large test-retest variability in metabolic parameters measured during steady state phases of moderate isometric plantar flexion exercise. However, kinetics parameters of recovery exhibited a small coefficient of variation (CV Ͻ 9%). In this line, van den Broek et al. (22) reported a low variability (CV Ͻ 11.5%) for the parameters describing the recovery kinetics of PCr and adenosine diphosphate (ADP) in a single subject who repeated the same exercise protocol 10 times. Based on a visual inspection of the kinetics of phosphorylated compounds and pH i...

The aim of this study was to investigate whether (1) spinal modulation would change after nonexhausting eccentric exercise of the plantar Xexor muscles that produced muscle soreness and (2) central modulation of the motor command would be linked to the development of muscle soreness. Ten healthy subjects volunteered to perform a single bout of backward downhill walking exercise (duration 30 min, velocity 1 ms ¡1 , negative grade ¡25%, load 12% of body weight). Neuromuscular test sessions [H-reXex, M-wave, maximal voluntary torque (MVT)] were performed before, immediately after, as well as 1-3 days after the exercise bout. Immediately after exercise there was a ¡15% decrease in MVT of the plantar Xexors partly attributable to an alteration in contractile properties (¡23% in electrically evoked mechanical twitch). However, MVT failed to recover before the third day whereas the contractile properties had signiWcantly recovered within the Wrst day. This delayed recovery of MVT was likely related to a decrement in voluntary muscle drive. The decrease in voluntary activation occurred in the absence of any variation in spinal modulation estimated from the H-reXex. Our Wndings suggest the development of a supraspinal modulation perhaps linked to the presence of muscle soreness.

Abstract. Regular physical exercise has been shown to benefit neurocognitive functions, especially enhancing neurogenesis in the hippocampus. However, the effects of a single exercise session on cognitive functions are controversial. To address this issue, we measured hemodynamic changes in the brain during physical exercise using near-infrared spectroscopy (NIRS) and investigated related effects on memory consolidation processes. Healthy young participants underwent two experimental visits. During each visit, they performed an associative memory task in which they first encoded a series of pictures, then spent 30-min exercising or resting, and finally were asked to recall the picture associations. We used NIRS to track changes in oxygenated hemoglobin concentration over the prefrontal cortex during exercise and rest. To characterize local tissue oxygenation and perfusion, we focused on low frequency oscillations in NIRS, also called vasomotion. We report a significant increase in associative memory consolidation after exercise, as compared to after rest, along with an overall increase in vasomotion. Additionally, performance improvement after exercise correlated positively with power in the neurogenic component (0.02 to 0.04 Hz) and negatively with power in the endothelial component (0.003 to 0.02 Hz). Overall, these results suggest that changes in vasomotion over the prefrontal cortex during exercise may promote memory consolidation processes. © The Authors. Published by SPIE under a Creative Commons Attribution 3.0 Unported License. Distribution or reproduction of this work in whole or in part requires full attribution of the original publication, including its DOI.

The effects of a priming exercise bout on both muscle energy production and the pattern of muscle fibre recruitment during a subsequent exercise bout are poorly understood. The purpose of the present study was to determine whether a prior exercise bout which is known to increase O 2 supply and to induce a residual acidosis could alter energy cost and muscle fibre recruitment during a subsequent heavy-intensity knee-extension exercise. Fifteen healthy subjects performed two 6 min bouts of heavy exercise separated by a 6 min resting period. Rates of oxidative and anaerobic ATP production, determined with 31 P-magnetic resonance spectroscopy, and breath-by-breath measurements of pulmonary oxygen uptake were obtained simultaneously. Changes in muscle oxygenation and muscle fibre recruitment occurring within the quadriceps were measured using near-infrared spectroscopy and surface electromyography. The priming heavy-intensity exercise increased motor unit recruitment (P < 0.05) in the early part of the subsequent exercise bout but did not alter muscle energy cost. We also observed a reduced deoxygenation time delay, whereas the deoxygenation amplitude was increased (P < 0.01). These changes were associated with an increased oxidative ATP cost after ∼50 s (P < 0.05) and a slight reduction in the overall anaerobic rate of ATP production (0.11 ± 0.04 mm minfor bout 1 and 0.06 ± 0.11 mm min −1 W −1 for bout 2; P < 0.05). We showed that a priming bout of heavy exercise led to an increased recruitment of motor units in the early part of the second bout of heavy exercise. Considering the increased oxidative cost and the unaltered energy cost, one could suggest that our results illustrate a reduced metabolic strain per fibre.

Muscle energetics has been largely and quantitatively investigated using (31)P MRS. Various methods have been used to estimate the corresponding rate of oxidative ATP synthesis (ATP(ox)); however, potential differences among methods have not been investigated. In this study, we aimed to compare the rates of ATP production and energy cost in two groups of subjects with different training status using four different methods: indirect method (method 1), ADP control model (method 2) and phosphate potential control model (method 3). Method 4 was a modified version of method 3 with the introduction of a correction factor allowing for similar values to be obtained for the end-exercise oxidative ATP synthesis rate inferred from exercise measurements and the initial recovery phosphocreatine resynthesis rate. Seven sedentary and seven endurance-trained subjects performed a dynamic standardised rest-exercise-recovery protocol. We quantified the rates of ATP(ox) and anaerobic ATP synthesis (ATP(ana)) using (31)P MRS data recorded at 1.5 T. The rates of ATP(ox) over the entire exercise session were independent of the method used, except for method 4 which provided significantly higher values in both groups (p < 0.01). In addition, methods 1-3 were cross-correlated, thereby confirming their statistical agreement. The rate of ATP(ana) was significantly higher with method 1 (p < 0.01) and lower with method 4 (p < 0.01). As a result of the higher rate of ATP(ox), EC (method 4) calculated over the entire exercise session was higher and initial EC (method 1) was lower in both groups compared with the other methods. We showed in this study that the rate of ATP(ox) was independent of the calculation method, as long as no corrections (method 4) were performed. In contrast, results related to the rates of ATP(ana) were strongly affected by the calculation method and, more exactly, by the estimation of protons generated by ATP(ox). Although the absolute EC values differed between the methods, within- or between-subject comparisons are still valid given the tight relationships between them.

The lack of steady phase during exercise apnoeas suggests that the conditions determining R3 were already attained at the end of E1. This being so, E2 would correspond to R3.

We tested the hypothesis that, after bed rest, maximal oxygen consumption ( VO₂max ) decreases more upright than supine, because of adequate cardiovascular response supine, but not upright. On 9 subjects, we determined VO₂max and maximal cardiac output (Q ) upright and supine, before and after (reambulation day upright, the following day supine) 35-day bed rest, by classical steady state protocol. Oxygen consumption, heart rate (f(H)) and stroke volume (Q(st)) were measured by a metabolic cart, electrocardiography and Modelflow from pulse pressure profiles, respectively. We computed Q as f(H) times Q(st), and systemic oxygen flow ( QaO₂) as Q. times arterial oxygen concentration, obtained after haemoglobin and arterial oxygen saturation measurements. Before bed rest, all parameters at maximal exercise were similar upright and supine. After bed rest, VO₂max was lower (p<0.05) than before, both upright (-38.6%) and supine (-17.0%), being 30.8% higher supine than upright. Maximal Q(st) decreased upright (-44.3%), but not supine (+3.7%), being 98.9% higher supine than upright. Maximal Q decreased upright (-45.1%), but not supine (+9.0%), being higher supine than upright (+98.4%). Maximal QaO₂ decreased upright (-37.8%), but not supine (+14.8%), being higher (+74.8%) upright than supine. After bed rest, the cardiovascular response (i) did not affect VO₂max supine, (ii) partially explained the VO₂max decrease upright, and (iii) caused the VO₂max differences between postures. We speculate that impaired peripheral oxygen transfer and/or utilisation may explain the VO₂max decrease supine and the fraction of VO₂max decrease upright unexplained by cardiovascular responses.