ISOKINETIC MUSCLE STRENGTH IN LONG-TERM IDDM PATIENTS IN RELATION TO DIABETIC COMPLICATIONS

The isokinetic muscle strength in 56 IDDM patients with > 20 years of diabetes duration and in their individually sex-, age-, weight-, and h eight-matched control subjects was assessed. Peak torque of foot dorsa l and plantar flexion and knee and wrist extension and flexion was mea sured. The neuropathic condition was assessed by a neurological disabi lity score, a neuropathy symptom score, nerve conduction studies, and quantitative sensory examination. All results were summed to obtain a neuropathy rank-sum score for each patient. According to their renal a lbumin excretion, the patients were classified to have normo-, micro-, or macroalbuminuria. In addition, according to their retinal status, patients were classified as having no, simple, or proliferative retino pathy. The IDDM patients had a 21% reduction of muscle strength of bot h ankle dorsal (P < 1 x 10(-4)) and plantar flexors (P < 0.01), compar ed with control subjects. A 16% reduction of knee extensors (P < 0.005 ) and a 17% reduction of knee flexors (P < 0.01) was found. In contras t, muscle strength in wrist flexors and extensors was not significantl y reduced (10 and 11%, respectively [NS]). In patients with the most s evere weakness, muscle strength of the calf muscles was only 50% of th e expected performance. Correlations were found between the neuropathy rank-sum score and the muscle strength of ankle dorsal (r = -0.66, P < 1 x 10(-7)) and plantar flexors (r = -0.51, P < 0.0005)), knee exten sors (r = -0.51, P < 0.0005) and flexors (r = -0.44, P < 0.005), and w rist flexors (r = -0.41, P < 0.005). No correlation was found for wris t extensors (r = 0). Neither were there any relationships between musc le strength at the ankle and knee and the degree of albuminuria or ret inopathy. In conclusion, motor performance is substantially impaired i n long-term IDDM patients, and the weakness is related to the presence of neuropathy but not to albuminuria or retinopathy per se.