Respiratory And Locomotor Muscle Oxygenation And Blood Volume Responses During Intermittent Exercise

Purpose: This study examined the time course of changes in the oxygenation and blood volume of respiratory (RM) and locomotor (LM) muscles, and the interrelationships of changes in these paramters ,and provide evidence for respiratory steal phenomenon during intense intermittent exercise.Methods: Oxygenation (RMO₂) and blood volume (RMBV) of serratus anterior (an accessory RM) and of vastus lateralis (LMO₂ and LMBV) were measured simultaneously by near-infrared spectroscopy in 15 healthy young men performing maximal incremental intermittent exercise. The respiratory compensation point (RCP), and the breakpoints where abrupt changes were apparent in RMO₂ (BP_RMO2), RMBV (BPRMBV), LMO₂ (BP_LMO2) and LMBV (BPLMBV) versus time were identified.Results: Falls in RMO₂ and LMO₂ accelerated in the vicinity of the RCP and were concomitant with reduction in LMBV, which had increased progressively from its pre-exercise level below the RCP. The time at which the RCP, BPRMO₂, BPLMO₂ and BPLMBV were detected (70.2-73.4% of exercise time) did not differ (P>0.05), and were inter-correlated (P<0.05). The rate of the accelerated fall of LMO₂ was correlated to that of the LMBV reduction (r =0.73) and of the accelerated RMO₂ decline (r =0.71).Conclusion: During the intense intermittent exercise, both RM and LM muscles were working heavily 1)The data suggest that the heavy RM work commencing at the RCP, precipitates a fall in the RMO₂, and exacerbates LM deoxygenation, secondary to fatigue was happened. 2) It is reasonable to suggest that these responses are secondary to vasoconstriction elicited by RM metaboreflex activation. This is the first study to provide evidence for respiratory steal phenomenon during intense intermittent exercise.