Purpose: Sub-clinical muscle involvement, including myopathic changes and mitochondrial dysfunction of skeletal muscle, has been reported in people with Huntington's disease (HD). Muscle strength was evaluated using a hand-held dynamometer. Reliability and validity in people with HD were determined.
Method: Isometric muscle strength of 6 lower limb muscle groups was measured in 20 people with HD and matched healthy controls. People with HD were evaluated with the Unified Huntington's Disease Rating Scales (UHDRS). Within session reliability using intra-class correlation coefficients (ICC) was calculated. Discriminant and convergent validity was also evaluated.
Results: UHDRS motor scores of people with HD ranged from 28 to 80. Reliability of strength testing was excellent (ICC 0.86 to 0.98). People with HD had on average about half the strength of healthy matched controls. UHDRS motor scores and strength scores were significantly correlated (convergent) providing a further indication of validity of strength testing.
Conclusions: The hand-held dynamometer is a reliable and valid measurement tool to detect strength differences between people with HD and a matched control group. There is significant reduction in lower limb muscle strength in HD which does not appear to have been described previously.