Background: For persons with multiple sclerosis (pwMS), exercise is known to be safe and effective at treating several symptoms and it may even be disease-modifying. However, exercise can trigger heat intolerance, exercise-induced heat sensitivity (EIHS), which may cause some pwMS to refrain from exercise. No review has yet summarized the existing knowledge on EIHS in pwMS. Therefore, the purpose of the present review was to clarify the terminology, summarize both the prevalence of EIHS and the current knowledge of underlying mechanisms, and provide an overview of existing treatment options and clinical management of EIHS in pwMS.
Methods: A scoping review was performed.
Results: As no clear definition could be identified in the literature, we propose a definition of EIHS. Aspects related to EIHS are reported in 29-80 % of all pwMS. The mechanisms underlying EIHS are not well understood but seem to include axon demyelination, CNS lesions, abnormal sudomotor function and sweating, abnormal afferent thermosensory function, disease stability, and abnormal neuropsychological responses. The severity of EIHS depends on the applied exercise modality, intensity, and format, and can be further reduced when applying different cooling interventions or garments before and/or during exercise.
Conclusion: EIHS appears frequently in pwMS, but the underlying mechanisms are still only sparsely understood. EIHS severity depends on exercise-related factors and can be reduced by cooling interventions.
Keywords: Cooling strategies; Exercise; Heat intolerance; Heat sensitivity; Multiple sclerosis; Physical activity.
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