Effect of prior heavy exercise on muscle deoxygenation kinetics at the onset of subsequent heavy exercise

Abstract

This study examines the effect of prior heavy exercise on muscle deoxygenation kinetics at the onset of heavy-intensity cycling exercise. Ten young male adults (20 +/- 2 years) performed two repetitions of step transitions (6 min) from 35 W to heavy-intensity exercise preceded by either no warm-up or by a heavy-intensity exercise. VO2 was measured breath-by-breath, and muscle deoxygenation (HHb) and total hemoglobin (Hb(tot)) were monitored continuously by near-infrared spectroscopy. We used a two-exponential model to describe the VO2 kinetics and a mono-exponential model for the HHb kinetic. The parameters of the phase II VO2 kinetics (TD1 VO2, tau1 VO2 and A1 VO2) were unaffected by prior heavy exercise, while some parameters of local muscle deoxygenation kinetics were significantly faster (TD HHb: 7 +/- 2 vs. 5 +/- 2 s; P < 0.001, MRT HHb: 20 +/- 3 vs. 15+/- 4 s; P < 0.05). Blood lactate, heart rate and Hb(tot) values were significantly higher before the second bout of heavy exercise. These results collectively suggest that the prior heavy exercise probably increased muscle O2 availability and improved O2 utilization at the onset of a subsequent bout of heavy exercise.

Effects of prior heavy exercise on heterogeneity of muscle deoxygenation kinetics during subsequent heavy exercise

“…average NIRS; Refs. 15,16,33,44). However, the present finding of a slower of the primary component during subsequent heavy exercise is not consistent with previous studies that found a similar for bout 1 vs. bout 2 (16,32,33,44).…”

“…On the other hand, a rapid appearance of phase II of mQ would occur in regions where the early increase in mQ closely matches the dynamics of mV O 2 (i.e., constant deoxy-[HbϩMb]), and thereby a short TD would be followed by a slower (20). The results in the present study support the latter scenario, thus suggesting that the performance of prior heavy exercise would promote the convective delivery of O 2 (phase II mQ ) to multiple sites of the muscles, improving the adequacy of mV O 2 /mQ O 2 matching at the onset of the subsequent bout of exercise (7,9,15,16,22,23,44).…”

“…In the upright (16,32) or prone (33) position, there are no significant differences in muscle deoxygenation kinetics [mean response time (MRT) of the primary phase] between the first and second bouts of heavy exercise. In contrast, Marles et al (44) found that the MRT of muscle deoxygenation was faster in the second bout than in the first heavy-exercise bout. These studies assumed a homogeneous response of muscle deoxygenation within muscle regions and among different portions of the exercising muscle based on either single channel near-infrared spectroscopy (NIRS) (16,32,33) or an average of eight channels (44).…”

“…In contrast, Marles et al (44) found that the MRT of muscle deoxygenation was faster in the second bout than in the first heavy-exercise bout. These studies assumed a homogeneous response of muscle deoxygenation within muscle regions and among different portions of the exercising muscle based on either single channel near-infrared spectroscopy (NIRS) (16,32,33) or an average of eight channels (44). However, we have recently shown appreciable heterogeneity in the kinetics of muscle deoxygenation across 10 sites of the working quadriceps during heavy exercise (38).…”

“…Collectively, previous studies reported that prior exercise in the upright position does not alter the phase II time constant of pulmonary O 2 uptake (pV O 2 ) response in the subsequent bout of heavy exercise (3, 7-11, 22, 30, 32, 44, 47, 52), with a few exceptions (16,46,53). The net amplitude of phase II is unaltered in some studies using 6-to 8-min recovery between heavy exercise bouts (7,10,44,52) and increased in other studies in which the recovery duration is 10 min or longer (up to ϳ45 min) (3,8,9,11,47). In contrast, the amplitude of the slow component (SC) is routinely diminished (3, 7-11, 17, 22, 24, 30, 32, 39, 42-44, 47, 52).…”