Aging Reduces The Maximal Level Of Peripheral Fatigue Tolerable And Impairs Exercise Capacity
AMERICAN JOURNAL OF PHYSIOLOGY-REGULATORY INTEGRATIVE AND COMPARATIVE PHYSIOLOGY(2020)
摘要
The aim of the present study was to determine the magnitude of the maximal level of peripheral fatigue attainable (fatigue threshold) during an all-out intermittent isometric knee-extensor protocol in both younger (24 +/- 1 yr, n = 12) and older (60 +/- 2 yr, n = 12) participants to provide new insights into the effects of aging on neuromuscular function. Participants performed two experimental sessions, in which they performed 60 maximal voluntary contractions (MVCs; 3 s of contraction, 2 s of relaxation). One trial was performed in the unfatigued state (CTRL) and one other following fatiguing neuromuscular electrical stimulation of the quadriceps (F-NMES). Peripheral fatigue was quantified via pre/postexercise decrease in quadriceps twitch force (Delta P-tw). Critical force (CF) was determined as the mean force output of the last 12 contractions, whereas W' was calculated as the area above CF. Although FNMES led to a significant decrease in P-tw before performing the 60-MVCs protocol (P = 0.024), Delta P-tw was not different between CTRL and F-NMES for both the young group (P = 0.491) and the old group (P = 0.523). However, this peripheral fatigue threshold was significantly greater in young versus old participants (Delta P-tw = -48 +/- 10% vs. -29 +/- 13%, respectively, P = 0.028). In CTRL, W' was 55 +/- 13% lower in the old group than in the young group (P < 0.001), but CF was similar (326 +/- 10 N vs. 322 +/- 12 N, respectively, P = 0.941). Delta P-tw was correlated with W', independently of age (r(2) = 0.84, P < 0.001). Exercise performance decreases with aging consequent to a lower tolerance to peripheral fatigue. However, the peripheral fatigue threshold mechanism persists with healthy aging and continues to play a protective role in preserving locomotor muscle function during exercise.
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关键词
aging, critical torque, exercise performance, group III, IV muscle afferents, neuromuscular fatigue
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