Acute Effects of a Multi-Ingredient Preworkout Supplement on Peak Torque and Muscle Activation During an Isokinetic Fatigue Protocol

This study examined the acute effects of a multi-ingredient preworkout supplement (MIPS) on peak torque of the leg extensors during a fatiguing isokinetic protocol in-volving isometric, concentric, and eccentric muscle actions. Thirteen recreational-ly-trained male subjects (mean age ± SD = 22.9 ± 2.2 years) were randomly assigned in crossover fashion to ingest a MIPS or placebo before an isokinetic protocol that con-sisted of 60 maximal, concentric and eccentric muscle actions with electromyographic signals recorded from the quadriceps. Immediately before (PRE) and after (POST) the protocol, subjects were assessed for isometric peak torque. The MIPS condition resulted in greater isometric (205 ± 48 vs. 185 ± 44 N·m, p = 0.04) and concentric (121 ± 34 vs. 103 ± 27 N·m, p = 0.015) torque values versus placebo (collapsed across time). For ec-centric peak torque, there was no significant (p > 0.05) interaction or main effect for condition. In addition, there were significant main effects for time (PRE vs. POST) for all muscle actions (p < 0.001). These findings indicated ingestion of the MIPS signifi-cantly attenuated the decline in both isometric and concentric, but not eccentric, peak torque during an isokinetic fatigue protocol of the leg extensors.