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

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 - 2010/7

Y1 - 2010/7

N2 - It was investigated whether 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 wk of acclimatization to 4,100 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 wk of acclimatization, no difference existed in venous plasma [K+] between the normoxic and hypoxic trial, either at submaximal intensities or 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 less (P < 0.01) in normoxic than hypoxic conditions, irrespective of the degree of acclimatization (at 260 W prior to acclimatization: -4.9 ± 0.8% in normoxia and -10.0 ± 0.4% 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 whether 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 wk of acclimatization to 4,100 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 wk of acclimatization, no difference existed in venous plasma [K+] between the normoxic and hypoxic trial, either at submaximal intensities or 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 less (P < 0.01) in normoxic than hypoxic conditions, irrespective of the degree of acclimatization (at 260 W prior to acclimatization: -4.9 ± 0.8% in normoxia and -10.0 ± 0.4% 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

SN - 0363-6119

VL - 299

SP - R306-R313

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

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

IS - 1

ER -