Heterogeneity of muscle deoxygenation kinetics during two bouts of repeated heavy exercises

Abstract

This study examines the effect of prior heavy exercise on the spatial distribution of muscle deoxygenation kinetics at the onset of heavy-intensity cycling exercise. Young untrained male adults (n = 16) performed two consecutive bouts of 6 min of high intensity cycle exercise separated by 6 min at 35 W. Muscle deoxygenation (HHb) was monitored continuously by near-infrared spectroscopy at eight sites in the quadriceps. Prior heavy exercise reduced the delay before the increase in HHb (9 +/- 2 vs. 5 +/- 2 s; P < 0.001). The standard deviation of TD HHb of the eight sites was decreased by the performance of prior exercise (1.1 +/- 0.5 vs. 0.8 +/- 0.4 s; P < 0.05). The transient decrease in HHb during the first 10 s of exercise was less during the second bout than during the first bout (0.6 +/- 0.6 vs. 0.3 +/- 0.3 A.U.; P < 0.01). The standard deviation of this decrease was also reduced by prior exercise (0.5 +/- 0.3 vs. 0.3 +/- 0.2 A.U.; P < 0.01). Lastly, prior exercise decreased significantly the standard deviation of the HHb rise during the time period corresponding to the pulmonary VO(2) slow component. These results indicate that prior heavy exercise reduced the spatial heterogeneity of muscle deoxygenation kinetics at the early onset of heavy exercise and during the development of the pulmonary VO(2) slow component. It indicates that the distribution of the VO(2)/O(2) delivery ratio within muscle was improved by the performance of a prior exercise.

Changes of direction during high-intensity intermittent runs: neuromuscular and metabolic responses

“…With the limitation of NIRS to monitor the actual muscle O 2 demands, present results suggest that HIE with two 90°-COD and a ~25% lower average running speed, elicits, in comparison with straight-line runs, an equivalent modification of the local O 2 uptake/delivery ratio, which is in agreement with the systemic V O 2 measures. The extrapolation of this findings to the overall lower musculature should however be viewed with caution given the large heterogeneity of muscle (de)oxygenation within the same muscle [46]. …”

Performance and physiological responses to repeated-sprint and jump sequences

“…2, with the exception of transient increases in muscle blood flow during the 3-s resting periods before each start, probably due to muscle relaxation), so that muscle oxygenation levels could have been interpreted accordingly. It should, however, be acknowledged that the perfusion and O 2 uptake within a muscle are heterogeneous during exercise (Prieur et al 2010), so that it is unclear whether present NIRS data collected on a unique site of measurement illustrate accurately the O 2 uptake/delivery ratio of the entire vastus lateralis (being itself only a part of the quadriceps muscle).…”

“…The use of multiple NIRS measurements sites (Prieur et al 2010), as well as the assessment of other lower limb muscles involved during jumps and acceleration phases (e.g., gastrocnemius, hamstring muscles, gluteus; Jacobs et al 1993), would have also assisted in clarifying present conclusions. The lack of data on neural and muscular adjustments of lower limb muscles (Billaut et al 2005;Perrey et al 2010) is another limitation to the present study.…”

Methodological validation of the dynamic heterogeneity of muscle deoxygenation within the quadriceps during cycle exercise

“…The CW-NIRS used in previous studies enabled identification of regional differences in blood volume and deoxygenation in muscle during exercise (22,25,30,39,43). However, assumptions of constant path length, absorption, and scattering coefficients used to convert the CW-NIRS signal to the relative concentration values limit the accuracy of measurement and may overestimate the changes in NIRS variables during exercise (15).…”