Analysis of the effects of self-selected warm-up on isometric contraction performance and on surface electromyogram of vastus lateralis

Background/objective: Self-selected warm-up also called reference warmup (RWU) was reported improving the performance endurance dynamic exercise. This study aimed to assess the effects of RWU on isometric endurance contraction.

Methods: Ten university level athletes performed two endurance isometric exercises on a dynamometer, with no warm-up (I-NWU) and with a self-selected warm-up (I-RWU). Skin temperature (T_sk), heart rate (HR), oxygen consumption (VO₂), blood lactate [La^-], root mean square (RMS), mean frequency (MF) and time limit (Tlim) were measured to assess the effects of RWU.

Results: T_sk, HR, (VO₂) and [La^-] were significantly raised (p < 0.01) after RWU compare to resting values, and remained significantly higher (p < 0.01) at the onset of I-RWU compare to I-NWU. Tlim significantly decreased after RWU (01:19 ± 00:25 for I-RWU vs. 01:49 ± 00:27 mm:ss for I-NWU) (p < 0.0005). RMS and MF showed no significant differences between I-NWU and I-RWU (p > 0.05).

Conclusion: Self-selected warm-up impairs the performance of consecutive isometric exercise. Athletes appear less able to self-perceive an optimal warm-up for endurance isometric. Metabolic and electromyogram parameters changes did not thoroughly explained the decline of performance; this gives room for a possible anticipation of central fatigue regulation, which need further investigation.