Alteration in neuromuscular function of the plantar flexors following caffeine ingestion

Abstract

The aim of this study was to compare the neuromuscular function of the plantar flexors following caffeine or placebo administration. Thirteen subjects (25 ± 3 years) ingested caffeine or placebo in a randomized, controlled, counterbalanced, double-blind crossover design. Neuromuscular tests were performed before and 1 h after caffeine or placebo intake. During neuromuscular testing, rate of torque development, isometric maximum voluntary torque, and neural drive to the muscles were measured. Triceps surae muscle activation was assessed by normalized root mean square of the EMG signal during the initial phase of contraction (0-100 ms, 100-200 ms) and maximal voluntary contraction (MVC). Furthermore, evoked spinal reflex responses of the soleus muscle (H-reflex evoked at rest and during MVC, V-wave) and peak twitch torques were evaluated. The isometric maximum voluntary torque and evoked potentials were not different. However, we found a significant difference between groups for rate of torque development in the time intervals 0-100 ms [41.1 N · m/s (95% CI: 8.3-73.9 N · m/s, P = 0.016)] and 100-200 ms [32.8 N · m/s (95% CI: 2.8-62.8 N · m/s, P = 0.034)]. These changes were accompanied by enhanced neural drive to the plantar flexors. Data suggest that caffeine solely increased explosive voluntary strength of the triceps surae because of enhanced neural activation at the onset of contraction whereas MVC strength was not affected.

Effect of balance training on neuromuscular function at rest and during isometric maximum voluntary contraction

“…The H-reflex during MVC (H sup ) was elicited 2 s after torque onset during the plateau of the torque-time curve at H max intensity to record the small M-wave preceding H sup (M H sup ) and H sup (Duclay et al 2008;Behrens et al 2014). It is possible that H sup did not represent the maximal H-reflex during MVC.…”

“…The individual positioning for each participant was equal before and after 8 weeks of training. The subjects were seated with their knees straight and their foot firmly attached to the adapter of the dynamometer (Ekblom 2010;Behrens et al 2014). Velcro straps and a snowboard binding were used to fasten the subjects' feet on the metal plate of the dynamometer.…”

Effects of caffeine on neuromuscular function in a non‐fatigued state and during fatiguing exercise

“…(2006) and by Behrens et al. (2015a, b), but contrary to other studies where an enhancement of the peak‐to‐peak maximal normalized H‐reflex (Kalmar & Cafarelli, 1999) and of the normalized slope of the H‐reflex recruitment curve (Walton et al., 2003) were observed. Walton et al.…”

“…Effects of caffeine on the excitability of spinal motoneurons are likely but far from unequivocal. Some authors have shown a positive effect in a non‐fatigued state (Kalmar & Cafarelli, 1999; Walton, Kalmar, & Cafarelli, 2002, 2003) and during fatigue (Kalmar et al., 2006), whereas others did not observe a significant effect in a non‐fatigued state (Behrens et al., 2015a, b; Kalmar et al., 2006). Some studies have attributed the ergogenic effects of caffeine to a decreased inhibition at the cortical or spinal level (Cerqueira, de Mendonça, Minez, Dias, & de Carvalho, 2006; de Carvalho, Marcelino, & de Mendonça, 2010) and an increased corticospinal excitability (Kalmar & Cafarelli, 2004, 2006), both of which may contribute to enhancement of descending neural drive.…”

Relationship between strength qualities and short track speed skating performance in young athletes

“…The axis of the dynamometer was aligned with the anatomical flexion‐extension axis. The athletes were fixed to the dynamometer as described previously (Behrens et al., , , ). The isometric maximum voluntary torque (iMVT) was measured during the following isometric MVC tasks: eversion, plantar flexion, dorsal flexion, knee flexion, and knee extension.…”