ENERGY-EXPENDITURE, PHYSICAL-ACTIVITY, AND BODY-COMPOSITION OF AMBULATORY ADULTS WITH HEREDITARY NEUROMUSCULAR DISEASE

Persons with neuromuscular disease (NMD) have progressive weakness and wasting of skeletal muscle, reduced fat-free mass, and increased fat mass relative to healthy control subjects. To test the hypothesis that resting energy expenditure (REE), estimated total daily energy expend iture (TEE), and physical activity patterns are altered in ambulatory adults with NMD, 26 adult men and women with slowly progressive NMD an d 19 able-bodied control subjects similar in age and weight were evalu ated. REE was measured after an overnight fast by indirect calorimetry , TEE by heart rate monitoring, and body composition by air-displaceme nt plethysmography. REE was not significantly different between NMD an d control subjects; however, TEE was significantly reduced in NMD subj ects compared with control subjects, respectively (women: 7.8 +/- 1.5 compared with 10.5 +/- 2.8; men: 10.2 +/- 3.6 compared with 12.7 +/- 2 .6 MJ/d; P less than or equal to 0.01), indicating that NMD subjects e xpended less energy in physical activity than did control subjects. NM D subjects also tended toward an increased energy cost of physical act ivity, particularly at higher activity levels (P = 0.06). Multiple reg ression analysis indicated that for all subjects combined, adiposity w as positively associated with age and TEE and negatively associated wi th time spent in the active heart rate range and fat-free mass (P less than or equal to 0.0001). This relation did not differ between NMD an d control subjects, nor did it differ between men and women. We hypoth esize that because of their reduced physical activity and increased ad iposity, persons with NMD may be at risk for developing secondary cond itions such as cardiovascular disease, hypertension, and diabetes.