Head-and-neck cooling has a greater effect on motor performance in unpredictable tasks than in constant and...

To determine the effects of different motor tasks (constant vs. predictable vs. unpredictable), as well as head-and-neck cooling, on central and peripheral fatigability, physiological-thermal stress, and motor system function in men with multiple sclerosis (MS).

Eighteen male MS volunteers (aged 34.9 ± 8.1 years) were allocated to one of two groups: the head-and-neck cooling group (COLD) or the control group (CON), which received no thermal intervention. Each group participated in three exercise trials, each structured with variations in simulated contraction intensity (constant, predictable, and unpredictable), with at least one week between trials. The trials involved 100 intermittent isometric contraction tasks, targeting knee extensions at a 60° flexion angle. Fatiguing motor tasks involved 5-second contractions followed by 20-second rest periods. Key variables were assessed before, during, and after a 1-hour recovery period.

Head-and-neck cooling reduced central fatigability, improved perceived exertion, and elevated electromyography amplitude across all motor task strategies (p < 0.05). When combined with head-and-neck cooling, the unpredictable motor task induced greater modulation of central and peripheral motor performance variables than the constant and predictable ones. Additionally, predictable and unpredictable motor tasks caused greater peripheral fatigability than constant tasks in both the COLD and CON groups (p < 0.05).

An unpredictable motor task combined with head-and-neck cooling enhances central activation of exercising muscles, leading to lower central fatigability and improved perceived exertion, while also inducing greater peripheral fatigability, as evidenced by reduced force generation and greater motor errors compared to constant and predictable ones in men with MS.