Handgrip dynamometry, Cybex measurements and lean mass as markers of the ageing of muscle function.

Isometric handgrip force, isokinetic knee flexion and extension torque, and anthropometric data were obtained on 67 older men and women (ranging in age from 45 to 75 years, mean 59.7 years). Hydrostatic and skinfold estimates of lean body mass were quite closely correlated with each other in this sample (r = 0.93). Handgrip force, isokinetic knee flexion and extension torque, and lean mass all decreased by 6-8% per decade over the age span examined, although in the men the loss was most marked in terms of handgrip and lean mass, whereas in the women the loss of torque in the knee muscles was dominant. Because of these differences, the handgrip data were only weakly correlated with the isokinetic strength measurements (r = 0.22), and the isokinetic data were more strongly related to lean body mass and body mass. The optimum equation for a field prediction of isokinetic strength in this age group (a combination of age, sex, age-sex interaction and lean body mass) has an error approaching 25%, with a multiple r2 of 0.37, and a standard error of the estimate (s.e.e.) of 24.5%. It is concluded that handgrip data and slow isokinetic torque measurements evaluate relatively independent aspects of the ageing of muscular function.