TY - JOUR

T1 - Human muscle net K+ release during exercise is unaffected by elevated anaerobic metabolism, but reduced after prolonged acclimatization to 4100 m

AU - Nordsborg, Nikolai Baastrup

AU - Calbet, Jose A. L.

AU - Sander, Mikael

AU - van Hall, Gerrit

AU - Juel, Carsten

AU - Saltin, Bengt

AU - Lundby, Carsten

N1 - CURIS 2010 5200 059

PY - 2010

Y1 - 2010

N2 - It was investigated if skeletal muscle K(+) release is linked to the degree of anaerobic energy production. Six subjects performed an incremental bicycle exercise test in normoxic and hypoxic conditions prior to and after 2 and 8 weeks of acclimatization to 4100 m. The highest workload completed by all subjects in all trials was 260 W. With acute hypoxic exposure prior to acclimatization, venous plasma [K(+)] was lower (P<0.05) in normoxia (4.9+/-0.1 mM) than hypoxia (5.2+/-0.2 mM) at 260 W, but similar at exhaustion which occurred at 400+/-9 W and 307+/-7 W (P<0.05), respectively. At the same absolute exercise intensity, leg net K(+) release was unaffected by hypoxic exposure independent of acclimatization. After 8 weeks of acclimatization no difference existed in venous plasma [K(+)] between the normoxic and hypoxic trial, neither at submaximal intensities nor at exhaustion (360+/-14 W vs. 313+/-8 W; P<0.05). At the same absolute exercise intensity, leg net K(+) release was less (P<0.001) than prior to acclimatization and reached negative values in both hypoxic and normoxic conditions after acclimatization. Moreover, the reduction in plasma volume during exercise relative to rest was higher (P<0.01) in normoxic than hypoxic conditions, irrespective of the degree of acclimatization (at 260 W prior to acclimatization: -10.0+/-0.4 % in normoxia and -4.9+/-0.8 % in hypoxia). It is concluded that leg net K(+) release is unrelated to anaerobic energy production and that acclimatization reduces leg net K(+) release during exercise.

AB - It was investigated if skeletal muscle K(+) release is linked to the degree of anaerobic energy production. Six subjects performed an incremental bicycle exercise test in normoxic and hypoxic conditions prior to and after 2 and 8 weeks of acclimatization to 4100 m. The highest workload completed by all subjects in all trials was 260 W. With acute hypoxic exposure prior to acclimatization, venous plasma [K(+)] was lower (P<0.05) in normoxia (4.9+/-0.1 mM) than hypoxia (5.2+/-0.2 mM) at 260 W, but similar at exhaustion which occurred at 400+/-9 W and 307+/-7 W (P<0.05), respectively. At the same absolute exercise intensity, leg net K(+) release was unaffected by hypoxic exposure independent of acclimatization. After 8 weeks of acclimatization no difference existed in venous plasma [K(+)] between the normoxic and hypoxic trial, neither at submaximal intensities nor at exhaustion (360+/-14 W vs. 313+/-8 W; P<0.05). At the same absolute exercise intensity, leg net K(+) release was less (P<0.001) than prior to acclimatization and reached negative values in both hypoxic and normoxic conditions after acclimatization. Moreover, the reduction in plasma volume during exercise relative to rest was higher (P<0.01) in normoxic than hypoxic conditions, irrespective of the degree of acclimatization (at 260 W prior to acclimatization: -10.0+/-0.4 % in normoxia and -4.9+/-0.8 % in hypoxia). It is concluded that leg net K(+) release is unrelated to anaerobic energy production and that acclimatization reduces leg net K(+) release during exercise.

U2 - 10.1152/ajpregu.00062.2010

DO - 10.1152/ajpregu.00062.2010

M3 - Journal article

C2 - 20410475

VL - 299

SP - R306-R313

JO - American Journal of Physiology

JF - American Journal of Physiology

SN - 0363-6119

IS - 1

ER -