Standards for judgments of unilateral impairments in muscle strength.

A secondary analysis of a data base of isometric strength measures from 136 asymptomatic adults (50-79 years) was conducted to estimate the normal difference between dominant and nondominant side strengths. Measures of strength obtained by hand-held dynamometry from 13 muscle actions were expressed as a ratio, dominant side strength:nondominant side strength. The ratios indicated that the dominant side was stronger on average but that the normal range of differences between sides could reach 23.2 to 40.2%, depending on the action. The findings do not provide much support for the convention of using a 10% difference in strength between sides to designate impairment.