Abstract
Background: The purpose of this study was to investigate the acute effects of a single oral administration of an essential amino acids enriched mixture (EAA) on myoelectric descriptors of fatigue and maximal force production after a resistance exercise protocol (REP).Methods: Twenty adult males (age: 27 ± 6 years; body mass: 72.7 ± 7.50 kg; height: 1.76 ± 0.06 m) were enrolled in a double-blind crossover placebo-controlled study. Subjects were randomized to receive EAA mix (0.15 g/kg BM) or a placebo (PLA) in two successive trials 7 days apart. In both trials subjects completed a REP 2 h after the ingestion of the EAA mix or PLA. Before ingestion and after REP subjects performed isometric contractions of the dominant upper limb with the elbow joint at 120 degrees: (1) two maximal voluntary contractions (MVCs) for 2–3 s; (2) at 20% MVC for 90 s; (3) at 60% MVC until exhaustion. Mean values of MVC, conduction velocity initial values (CV), fractal dimension initial values (FD), their rates of change (CV slopes, FD slopes) and the Time to perform the Task (TtT) were obtained from a multichannel surface electromyography (sEMG) recording technique. Basal blood lactate (BL) and BL after REP were measured.Results: Following REP a significant decrease of MVC was observed in PLA (P < 0.05), while no statistical differences were found in EAA between pre-REP and post-REP. After REP, although a significant increase in BL was found in both groups (P < 0.0001) a higher BL Δ% was observed in PLA compared to EAA (P < 0.05). After REP, at 60% MVC a significant increase of CV rate of change (P < 0.05) was observed in PLA but not in EAA. At the same force level TtT was longer in EAA compared to PLA, with a significant TtT Δ% between groups (P < 0.001).Conclusion: Acute EAA enriched mix administration may prevent the loss of force-generating capacity during MVC following a REP. During isometric contraction at 60% MVC after REP the EAA mix may maintain CV rate of change values with a delay in the TtT failure.
Highlights
The possibility that a nutritional supply could have an acute effect on resistance exercise (RE) performance has attracted a great deal of interest in recent decades, and several studies on this topic have been published (Kreider et al, 2010; Smith et al, 2010; Martinez et al, 2016)
After resistance exercise protocol (REP) a significant decrease of maximal voluntary contraction (MVC) value was observed in PLA (P < 0.05; effect size = 0.69), while no statistical differences were found in essential amino acids (EAAs) (Table 3)
REP outcomes showed no statistical differences for biceps curls repetitions (BCRs) and Wingate round per minute (WRPM) between EAA and PLA, while statistical differences were found between BL1 and BL2 in both groups (P < 0.0001; EAA effect size = 3.38; PLA effect size = 4.12)
Summary
The possibility that a nutritional supply could have an acute effect on resistance exercise (RE) performance has attracted a great deal of interest in recent decades, and several studies on this topic have been published (Kreider et al, 2010; Smith et al, 2010; Martinez et al, 2016). The market largely claims that amino acids (AA) consumption before RE may delay the appearance of fatigue and improve physical performance This interesting hypothesis is not adequately supported in literature which primarily deals with supplements containing rapid ATP replacement aids to increase strength and power (e.g., creatine) (Butts et al, 2018), stimulants able to increase muscle activation (e.g., caffeine) (Goldstein et al, 2010), or physiological buffers known to reduce lactate production (e.g., beta-alanine) (Hoffman et al, 2018). The purpose of this study was to investigate the acute effects of a single oral administration of an essential amino acids enriched mixture (EAA) on myoelectric descriptors of fatigue and maximal force production after a resistance exercise protocol (REP)
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