Abstract

To determine effects of severe muscular dystrophy on the performance of dynamic exercise, cardio-respiratory responses to incremental work on a bicycle ergometer and isokinetic limb strength measurements were compared for 13 distrophic boys and 13 normal, untrained boys. The dystrophic boys (D) were matched to the normal boys (N) on the basis of age (8.4 yr), height (125 cm) and weight (25,7 kg). At rest, the dystrophic group had higher heart rates (HR) (D=102; N= 89 beats/min), and lower stroke volume (SV) (D = 31; N = 39 ml), with no difference in oxygen uptake (VO2), calculated cardiac output (Q),pulmonary ventilation (VE), or respiratory exchange ratio (R). During submaximal work, Vo2, SV, Q and VE were lower in D. During maximal work, D had lower peak values for work rate (D=400; N = 600 kg/min), endurance (D = 7.2; N = 12.5 min), Vo2 (D = 037; N = 1,35 liters/ min), HR (D = 136; N = 189 beats/ min), SV (D = 41; N = 60 ml), Q (D = 5.2; N = 11.0 liters/min), VE (D = 8.2; N = 36.9 liters/min), and R (D = 0.84; N = 0.99). Arm and leg strengths (four flexion and four extension motious) were lowerin D, but muscle girthswere not necessarily smaller. The findings indicate exercise performance in D was belownormal and limited by low cardiorespiratory capacities, diminished leg strength, and perhaps reduced peripheral oxygen utilization. Duchenne musculardystrophy, even in its early stages, apparently affects the work capacity of cardiac and pulmonary muscles as well as limb muscles. Verf.-referat