Skeletal muscle water T as a biomarker of disease status and exercise effects in patients with Duchenne muscular dystrophy.

The purpose of this study was to examine exercise effects on muscle water T in patients with Duchenne muscular dystrophy (DMD). In 12 DMD subjects and 19 controls, lower leg muscle fat (%) was measured by Dixon and muscle water T and R (1/T) by the tri-exponential model. Muscle water R was measured again at 3 hours after an ankle dorsiflexion exercise. The muscle fat fraction was higher in DMD participants than in controls (p < .001) except in the tibialis posterior muscle. Muscle water T was measured independent of the degree of fatty degeneration in DMD muscle. At baseline, muscle water T was higher in all but the extensor digitorum longus muscles of DMD participants than controls (p < .001). DMD participants had a lower muscle torque (p < .001) and exerted less power (p < .01) during exercise than controls. Nevertheless, muscle water R decreased (T increased) after exercise from baseline in DMD subjects and controls with greater changes in the target muscles of the exercise than in ankle plantarflexor muscles. Skeletal muscle water T is a sensitive biomarker of the disease status in DMD and of the exercise response in DMD patients and controls.