Introduction: Mental training, as physical training, enhances muscle strength. While the repetition of maximal voluntary contractions (MVCs) induces neuromuscular fatigue, the effect of maximal imagined contractions (MICs) on neuromuscular fatigue remains still unknown. Here, we investigated neuromuscular alterations following a mental-training session including MICs, a physical-training session including MVCs, and a combined-training session including both MICs and MVCs of the elbow flexor muscles.
Methods: Ten participants performed 80 MICs (duty cycle: 5-s MIC and 10-s rest), 80 MVCs (identical duty cycle), or 80 MVCs and 80 MICs (5-s MVCs, 2-s rest, 5-s MICs and 3-s rest) in three separate sessions. MVC torque was assessed 5 times over the course of the training, as well as 10 min after the end of the training in the three protocols. Central activation ratio (CARc), reflecting central fatigue, and corticospinal excitability, at rest and during MICs, were estimated using transcranial magnetic stimulation.
Results: Both the physical training and the combined training induced a ~40 % drop of MVC torque, accompanied with a ~10 % decrease of CARc, without significant difference between the two sessions. On the contrary, the repetition of MICs did not reduce maximal force production capacity and did not alter CARc. Corticospinal excitability was always facilitated during MIC compared to rest, ensuring that the participants imagined the desired movement.
Conclusion: These results suggested that one session of mental training alone or combined with physical training do not induce (additional) neuromuscular fatigue despite the repetitive activation of the corticospinal track. Motor imagery may be added to physical practice to increase the total workload without exacerbating neuromuscular fatigue.
(C) 2014 American College of Sports Medicine