Impact of heat therapy on skeletal muscle structure and function

Abstract

Skeletal muscle occupies approximately 40 to 50 percent of body mass and is responsible\nfor respiration, postural control, and locomotion and plays a pivotal role in regulating glucose,\nlipid, and protein metabolism. Acute muscle trauma and chronic disease conditions such as\nmuscular dystrophies are associated with structural abnormalities, enhanced fatigability and\nimpaired metabolism and consequently lead to exercise intolerance and poor quality of life.\nDespite the clinical importance and a number of studies on the treatment of muscle damage, few\nmodalities have shown to elicit beneficial effects. Heat treatment has been used for a long time to\ntreat soft tissue injuries in the field of physical therapy and sports medicine. However, the\nunderlying mechanisms by which heat treatment accelerates muscle recovery following injury are\nnot clear.\n\n The primary aim of my dissertation studies was to determine the impact of heat therapy on\nskeletal muscle structure and function in humans and animals. In Chapter 2, we report that a single\nsession of local heat treatment promotes the expression of angiogenic and myogeneic mediators\nincluding vascular endothelial growth factor (VEGF) and angiopoietin 1(ANGPT1) in healthy\nhuman skeletal muscle. In Chapter 3, we report repeated exposure to heat therapy stimulates factors\ninvolved in muscle repair process and accelerates functional recovery from exercise-induced\nmuscle damage. In Chapter 4, we show that 8 weeks of local heat therapy improves muscle strength\nof knee extensor and increases skeletal muscle capillarization in type II muscle fibers. In Chapter\n5, we describe the effects of heat therapy in a mouse model of ischemia induced-muscle damage.\nAnimals that were exposed to heat therapy at 39°C had improved maximal absolute force and\nrelative muscle mass in the soleus muscle. These observations reveal that the beneficial effects of\nheat therapy are muscle fiber type specific and dependent on the treatment temperature. In Chapter\n6, we review and summarize the outcomes described in Chapters 2-5 and provide a general\nconclusion as well the clinical implications of our findings.