Muscular endurance in long-term IDDM patients.

OBJECTIVE: To determine the short-term muscular endurance and working capacity of leg muscles in long-term IDDM patients in relation to neuropathic complications, muscle strength, and metabolic control. RESEARCH DESIGN AND METHODS: The muscular endurance of extensors and flexors at the ankle and knee was assessed in 44 IDDM patients and in 44 matched control subjects during 30 maximal isokinetic movements. The endurance index was the work performance of the last 5 movements relative to the first 5 movements. Total work was the summated work of all movements. All patients underwent a neurological evaluation, nerve conduction studies, and quantitative sensory tests.
RESULTS: The combined endurance index of the ankle extensors and flexors was 70% (51-88) (median [range]) in the diabetic group and 65% (55-82) in the control group (P < 0.01). For knee extensors and flexors the combined endurance index was 65% (55-103) for the diabetic patients and 63% (48-75) in the control subjects (P < 0.01). The endurance index related neither to the severity of neuropathy nor to the metabolic control (blood glucose and HbA1c) for any of the muscle groups. Diabetic patients had reduced strength of all muscle groups (14-24%, P < 0.02) and impaired total work performance (15-20%, P < 0.01) for ankle movements.
CONCLUSIONS: Long-term IDDM patients have increased endurance but reduced strength and work performance of leg muscles. The combined effect of the motor abnormalities is suggested to give rise to functional impairment, including an increased risk of falls and injuries.