Head-neck heating and fatigue: Effects on peripheral and central function and motor accuracy in healthy men and those with multiple sclerosis

Abstract

Objective

This study aimed to evaluate whether localized heating of the head and neck, combined with prolonged submaximal exercise at a thermoneutral temperature, would elicit peripheral and central changes in healthy men and those with multiple sclerosis (MS).

Methods

We studied the effects of head-neck heating (at 44 °C ± 0.5 °C adjacent to the skin) in men with relapsing-remitting MS (n = 16; age: 31.8 ± 7.6 years) and healthy men (n = 18; age: 27.6 ± 4.3 years). Both groups completed local heating and control trials (1-week apart) comprising 100 intermittent isometric knee extensions (5-s contraction, 20-s rest). We assessed electrically induced torque, maximal voluntary contraction (MVC), central activation ratio, muscle temperature (Tmu), perceived effort, blood stress markers, electromyography (EMG), and motor variability and accuracy. Measurements were taken at baseline, after 50 and 100 repetitions, and after 1-h recovery.

Results

Local heating inhibits central activation and reduces exercise-induced peripheral fatigue compared with non-heating conditions (p < 0.05) in men with MS. Head-neck heating led to a greater increase in Tmu during exercise in both groups. During high-intensity exercise (75 % MVC), local heating increased perceived effort in men with MS, impaired accuracy in healthy men, but did not affect EMG amplitude in either group (p < 0.05). Local heating during submaximal exercise induced greater changes in central and peripheral fatigability in men with MS than in healthy men (p < 0.05).

Conclusion

Head-neck heating during exercise suppressed central muscle activation and reduced peripheral fatigue in men with MS more than exercise performed under non-heating conditions.