EXERCISE PERFORMANCE IN 6-TO-11-YEAR-OLD BOYS WITH DUCHENNE MUSCULAR-DYSTROPHY

Google Scholar
  • 1 January 1977
    • journal article
    • research article
    • Vol. 58  (5) , 195-201
Abstract
To determine effects of severe muscular dystrophy on the performance of dynamic exercise, cardiorespiratory responses to incremental work on a bicycle ergometer and isokinetic limb strength measurements were compared for 13 dystrophic 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 O2 uptake (.ovrhdot.VO2), calculated cardiac output (.ovrhdot.Q), pulmonary ventilation (.ovrhdot.VE) or respiratory exchange ratio (R). During submaximal work, .ovrhdot.VO2, SV, .ovrhdot.Q and .ovrhdot.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), .ovrhdot.VO2 (D = 0.37; N = 1.35 l/min), HR (D = 136; N = 189 beats/min), SV (D = 41; N = 60 ml), .ovrhdot.Q (D = 5.2; N = 11.0 l/min), .ovrhdot.VE (D = 8.2; N = 36.9 l/min) and R (D = 0.84; N = 0.99). Arm and leg strengths (4 flexion and 4 extension motions) were lower in D, but muscle girths were not necessarily smaller. Exercise performance in D was below normal and limited by low cardiorespiratory capacities, diminished leg strength and perhaps reduced peripheral O2 utilization. Duchenne muscular dystrophy, even in its early stages, apparently affected the work capacity of cardiac and pulmonary muscles and limb muscles.