No abstract

Although NIRS instrumentation is promising in evaluating oxidative skeletal muscle performance when used in sport settings, there is still the need for further instrumental development and randomized/longitudinal trials to support the detailed advantages of muscle oximetry utilization in sports science.

In this experimental design, our findings suggest that the ability to repeat short-duration (6 s) sprints was associated with the occurrence of both peripheral and central fatigue.

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.

O2 uptake (VO2) kinetics and electromyographic (EMG) activity from the vastus medialis, rectus femoris, biceps femoris, and medial gastrocnemius muscles were studied during constant-load concentric and eccentric cycling. Six healthy men performed transitions from baseline to high-intensity eccentric (HE) exercise and to high-intensity (HC), moderate-intensity (MC), and low-intensity (LC) concentric exercise. For HE and HC exercise, absolute work rate was equivalent. For HE and LC exercise, VO2 was equivalent. VO2 data were fit by a two- or three-component exponential model. Surface EMG was recorded during the last 12 s of each minute of exercise to obtain integrated EMG and mean power frequency. Only in the HC exercise did VO2 increase progressively with evidence of a slow component (phase 3), and only in HC exercise was there evidence of a coincident increase with time in integrated EMG of the vastus medialis and rectus femoris muscles (P < 0.05) with no change in mean power frequency. The phase 2 time constant was slower in HC [24.0 +/- 1.7 (SE) s] than in HE (14.7 +/- 2.8 s) and LC (16.7 +/- 2.2 s) exercise, while it was not different from MC exercise (20.6 +/- 2.1 s). These results show that the rate of increase in VO2 at the onset of exercise was not different between HE and LC exercise, where the metabolic demand was similar, but both had significantly faster kinetics for VO2 than HC exercise. The VO2 slow component might be related to increased muscle activation, which is a function of metabolic demand and not absolute work rate.