Leg oxygen uptake in the initial phase of intense exercise is slowed by a marked reduction in oxygen delivery

TY - JOUR

T1 - Leg oxygen uptake in the initial phase of intense exercise is slowed by a marked reduction in oxygen delivery

AU - Christensen, Peter Møller

AU - Nyberg, Michael Permin

AU - Mortensen, Stefan Peter

AU - Nielsen, Jens Jung

AU - Secher, Niels H.

AU - Damsgaard, Rasmus

AU - Hellsten, Ylva

AU - Bangsbo, Jens

N1 - CURIS 2013 NEXS 124

PY - 2013/8/1

Y1 - 2013/8/1

N2 - The present study examined whether a marked reduction in oxygen delivery, unlike findings in moderate-intensity exercise, would slow leg oxygen uptake (V̇o2) kinetics during intense exercise (86 ± 3% of incremental test peak power). Seven healthy males (26 ± 1 years, means ± SE) performed one-legged knee-extensor exercise (60 ± 3 W) for 4 min in a control setting (CON) and with arterial infusion of NG -monomethyl-L-arginine and indomethacin in the working leg to reduce blood flow by inhibiting formation of nitric oxide and prostanoids (double blockade; DB). In DB leg blood flow (LBF) and oxygen delivery during the first minute of exercise were 25-50% lower (P < 0.01) compared with CON (LBF after 10 s: 1.1 ± 0.2 vs. 2.5 ± 0.3 l/min and 45 s: 2.7 ± 0.2 vs. 3.8 ± 0.4 l/min) and 15% lower (P < 0.05) after 2 min of exercise. Leg V̇o2 in DB was attenuated (P < 0.05) during the first 2 min of exercise (10 s: 161 ±26 vs. 288 ±34 ml/min and 45 s: 459 ± 48 vs. 566 ± 81 ml/min) despite a higher (P < 0.01) oxygen extraction in DB. Net leg lactate release was the same in DB and CON. The present study shows that a marked reduction in oxygen delivery can limit the rise in V̇o2 during the initial part of intense exercise. This is in contrast to previous observations during moderate-intensity exercise using the same DB procedure, which suggests that fast-twitch muscle fibers are more sensitive to a reduction in oxygen delivery than slow-twitch fibers.

AB - The present study examined whether a marked reduction in oxygen delivery, unlike findings in moderate-intensity exercise, would slow leg oxygen uptake (V̇o2) kinetics during intense exercise (86 ± 3% of incremental test peak power). Seven healthy males (26 ± 1 years, means ± SE) performed one-legged knee-extensor exercise (60 ± 3 W) for 4 min in a control setting (CON) and with arterial infusion of NG -monomethyl-L-arginine and indomethacin in the working leg to reduce blood flow by inhibiting formation of nitric oxide and prostanoids (double blockade; DB). In DB leg blood flow (LBF) and oxygen delivery during the first minute of exercise were 25-50% lower (P < 0.01) compared with CON (LBF after 10 s: 1.1 ± 0.2 vs. 2.5 ± 0.3 l/min and 45 s: 2.7 ± 0.2 vs. 3.8 ± 0.4 l/min) and 15% lower (P < 0.05) after 2 min of exercise. Leg V̇o2 in DB was attenuated (P < 0.05) during the first 2 min of exercise (10 s: 161 ±26 vs. 288 ±34 ml/min and 45 s: 459 ± 48 vs. 566 ± 81 ml/min) despite a higher (P < 0.01) oxygen extraction in DB. Net leg lactate release was the same in DB and CON. The present study shows that a marked reduction in oxygen delivery can limit the rise in V̇o2 during the initial part of intense exercise. This is in contrast to previous observations during moderate-intensity exercise using the same DB procedure, which suggests that fast-twitch muscle fibers are more sensitive to a reduction in oxygen delivery than slow-twitch fibers.

U2 - 10.1152/ajpregu.00048.2013

DO - 10.1152/ajpregu.00048.2013

M3 - Journal article

C2 - 23720134

SN - 0363-6119

VL - 305

SP - R313-R321

JO - American Journal of Physiology: Regulatory, Integrative and Comparative Physiology

JF - American Journal of Physiology: Regulatory, Integrative and Comparative Physiology

IS - 3

ER -