Muscle fatigue and exhaustion during dynamic leg exercise in normoxia and hypobaric hypoxia
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Muscle fatigue and exhaustion during dynamic leg exercise in normoxia and hypobaric hypoxia. / Fulco, C S; Lewis, S F; Frykman, Peter; Boushel, Robert Christopher; Smith, Susanne; Harman, E A; Cymerman, A; Pandolf, K B.
In: Journal of Applied Physiology, Vol. 81, No. 5, 01.11.1996, p. 1891-900.Research output: Contribution to journal › Journal article › Research › peer-review
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TY - JOUR
T1 - Muscle fatigue and exhaustion during dynamic leg exercise in normoxia and hypobaric hypoxia
AU - Fulco, C S
AU - Lewis, S F
AU - Frykman, Peter
AU - Boushel, Robert Christopher
AU - Smith, Susanne
AU - Harman, E A
AU - Cymerman, A
AU - Pandolf, K B
PY - 1996/11/1
Y1 - 1996/11/1
N2 - Using an exercise device that integrates maximal voluntary static contraction (MVC) of knee extensor muscles with dynamic knee extension, we compared progressive muscle fatigue, i.e., rate of decline in force-generating capacity, in normoxia (758 Torr) and hypobaric hypoxia (464 Torr). Eight healthy men performed exhaustive constant work rate knee extension (21 +/- 3 W, 79 +/- 2 and 87 +/- 2% of 1-leg knee extension O2 peak uptake for normoxia and hypobaria, respectively) from knee angles of 90-150 degrees at a rate of 1 Hz. MVC (90 degrees knee angle) was performed before dynamic exercise and during 0.05) that were higher (P <0.01) than peak force of constant work rate knee extension (98 +/- 10 N, 18 +/- 3% of MVC). Time to exhaustion was 56% shorter for hypobaria than for normoxia (19 +/- 5 vs. 43 +/- 7 min, respectively; P <0.01), and rate of right leg MVC fall was nearly twofold greater for hypobaria than for normoxia (mean slope = -22.3 vs. -11.9 N/min, respectively; P <0.05). With increasing duration of dynamic exercise for normoxia and hypobaria, integrated electromyographic activity during MVC fell progressively with MVC force, implying attenuated maximal muscle excitation. Exhaustion, per se, was postulated to related more closely to impaired shortening velocity than to failure of force-generating capacity.
AB - Using an exercise device that integrates maximal voluntary static contraction (MVC) of knee extensor muscles with dynamic knee extension, we compared progressive muscle fatigue, i.e., rate of decline in force-generating capacity, in normoxia (758 Torr) and hypobaric hypoxia (464 Torr). Eight healthy men performed exhaustive constant work rate knee extension (21 +/- 3 W, 79 +/- 2 and 87 +/- 2% of 1-leg knee extension O2 peak uptake for normoxia and hypobaria, respectively) from knee angles of 90-150 degrees at a rate of 1 Hz. MVC (90 degrees knee angle) was performed before dynamic exercise and during 0.05) that were higher (P <0.01) than peak force of constant work rate knee extension (98 +/- 10 N, 18 +/- 3% of MVC). Time to exhaustion was 56% shorter for hypobaria than for normoxia (19 +/- 5 vs. 43 +/- 7 min, respectively; P <0.01), and rate of right leg MVC fall was nearly twofold greater for hypobaria than for normoxia (mean slope = -22.3 vs. -11.9 N/min, respectively; P <0.05). With increasing duration of dynamic exercise for normoxia and hypobaria, integrated electromyographic activity during MVC fell progressively with MVC force, implying attenuated maximal muscle excitation. Exhaustion, per se, was postulated to related more closely to impaired shortening velocity than to failure of force-generating capacity.
KW - Adult
KW - Anoxia
KW - Atmospheric Pressure
KW - Electromyography
KW - Energy Metabolism
KW - Exercise
KW - Humans
KW - Leg
KW - Male
KW - Muscle Contraction
KW - Muscle Fatigue
KW - Oxygen
KW - Oxygen Consumption
KW - Physical Endurance
M3 - Journal article
C2 - 8941506
VL - 81
SP - 1891
EP - 1900
JO - Journal of Applied Physiology
JF - Journal of Applied Physiology
SN - 8750-7587
IS - 5
ER -
ID: 33851157