October 24, 2017
J Pethick et al, 2017. Caffeine ingestion attenuates fatigue-induced loss of muscle torque complexity, Med Sci Sports Exercise, published online.
The temporal structure, or complexity, of muscle torque output decreases with neuromuscular fatigue. The role of central fatigue in this process is unclear.
PURPOSE: We tested the hypothesis that caffeine administration would attenuate the fatigue-induced loss of torque complexity.
METHODS: Eleven healthy participants performed intermittent isometric contractions of the knee extensors to task failure at a target torque of 50% maximal voluntary contraction (MVC), with a 60% duty factor (6 s contraction, 4 s rest), 60 min after ingesting 6 mg·kg caffeine or a placebo. Torque and surface EMG signals were sampled continuously. Complexity and fractal scaling of torque were quantified using approximate entropy (ApEn) and the detrended fluctuation analysis (DFA) α scaling exponent. Global, central and peripheral fatigue were quantified using MVCs with femoral nerve stimulation.
RESULTS: Caffeine ingestion increased endurance by 30 ± 16% (mean ± SD, P = 0.019). Complexity decreased in both trials (decreased ApEn, increased DFA α; both P < 0.01), as global, central and peripheral fatigue developed (all P < 0.01). Complexity decreased significantly more slowly following caffeine ingestion (ApEn, -0.04 ± 0.02 vs. -0.06 ± 0.01, P = 0.004; DFA α, 0.03 ± 0.02 vs. 0.04 ± 0.03, P = 0.024), as did the rates of global (-18.2 ± 14.1 vs. -23.0 ± 17.4 N.m.min, P = 0.004) and central (-3.5 ± 3.4 vs. -5.7 ± 3.9 %·min, P = 0.02) but not peripheral (-6.1 ± 4.1 vs. -7.9 ± 6.3 N.m.min, P = 0.06) fatigue.
CONCLUSION: Caffeine ingestion slowed the fatigue-induced loss of torque complexity and increased the time to task failure during intermittent isometric contractions, most likely through central mechanisms.
Ja tak, jeg vil gerne modtage nyhedsbrev, når der er noget nyt om kaffe og helbred.