TY - JOUR
T1 - Slow component of VO2 kinetics: Mechanistic bases and practical applications
AU - Jones, Andrew M
AU - Grassi, Bruno
AU - Christensen, Peter Møller
AU - Krustrup, Peter
AU - Bangsbo, Jens
AU - Poole, David C
N1 - CURIS 2011 5200 050
PY - 2011/11
Y1 - 2011/11
N2 - The V̇o2 slow component, a slowly developing increase in V̇o2 during constant-work-rate exercise performed above the lactate threshold, represents a progressive loss of skeletal muscle contractile efficiency and is associated with the fatigue process. This brief review outlines the current state of knowledge concerning the mechanistic bases of the V̇o2 slow component and describes practical interventions that can attenuate the slow component and thus enhance exercise tolerance. There is strong evidence that, during constant-work-rate exercise, the development of the V̇o2 slow component is associated with the progressive recruitment of additional (type II) muscle fibers that are presumed to have lower efficiency. Recent studies, however, indicate that muscle efficiency is also lowered (resulting in a "mirror-image" V̇o2 slow component) during fatiguing, high-intensity exercise in which additional fiber recruitment is unlikely or impossible. Therefore, it seems that muscle fatigue underpins the V̇o2 slow component, although the greater fatigue sensitivity of recruited type II fibers might still play a crucial role in the loss of muscle efficiency in both situations. Several interventions can reduce the magnitude of the V̇o2 slow component, and these are typically associated with an enhanced exercise tolerance. These include endurance training, inspiratory muscle training, priming exercise, dietary nitrate supplementation, and the inspiration of hyperoxic gas. All of these interventions reduce muscle fatigue development either by improving muscle oxidative capacity and thus metabolic stability or by enhancing bulk muscle O2 delivery or local Q̇O2-to-V̇o2 matching. Future honing of these interventions to maximize their impact on the V̇o2 slow component might improve sports performance in athletes and exercise tolerance in the elderly or in patient populations.
AB - The V̇o2 slow component, a slowly developing increase in V̇o2 during constant-work-rate exercise performed above the lactate threshold, represents a progressive loss of skeletal muscle contractile efficiency and is associated with the fatigue process. This brief review outlines the current state of knowledge concerning the mechanistic bases of the V̇o2 slow component and describes practical interventions that can attenuate the slow component and thus enhance exercise tolerance. There is strong evidence that, during constant-work-rate exercise, the development of the V̇o2 slow component is associated with the progressive recruitment of additional (type II) muscle fibers that are presumed to have lower efficiency. Recent studies, however, indicate that muscle efficiency is also lowered (resulting in a "mirror-image" V̇o2 slow component) during fatiguing, high-intensity exercise in which additional fiber recruitment is unlikely or impossible. Therefore, it seems that muscle fatigue underpins the V̇o2 slow component, although the greater fatigue sensitivity of recruited type II fibers might still play a crucial role in the loss of muscle efficiency in both situations. Several interventions can reduce the magnitude of the V̇o2 slow component, and these are typically associated with an enhanced exercise tolerance. These include endurance training, inspiratory muscle training, priming exercise, dietary nitrate supplementation, and the inspiration of hyperoxic gas. All of these interventions reduce muscle fatigue development either by improving muscle oxidative capacity and thus metabolic stability or by enhancing bulk muscle O2 delivery or local Q̇O2-to-V̇o2 matching. Future honing of these interventions to maximize their impact on the V̇o2 slow component might improve sports performance in athletes and exercise tolerance in the elderly or in patient populations.
U2 - 10.1249/MSS.0b013e31821fcfc1
DO - 10.1249/MSS.0b013e31821fcfc1
M3 - Journal article
C2 - 21552162
SN - 0195-9131
VL - 43
SP - 2046
EP - 2062
JO - Medicine and Science in Sports and Exercise
JF - Medicine and Science in Sports and Exercise
IS - 11
ER -