Ten-year longitudinal changes in muscle power, force, and velocity in young, middle-aged, and older adults

BackgroundMaximum muscle power (P-max) is a biomarker of physical performance in all ages. No longitudinal studies have assessed the effects of aging on P-max obtained from the torque-velocity (T-V) relationship, which should be considered the 'gold standard'. This study evaluated the longitudinal changes in the T-V relationship and P-max of the knee-extensor muscles in young, middle-aged, and older adults after 10 years of follow-up. MethodsFour hundred eighty-nine subjects (311 men and 178 women; aged 19-68 years) were tested at baseline and after a 10-year follow-up. Anthropometric data, daily protein intake, physical activity level (PAL), and knee-extension muscle function (isometric, isokinetic, and isotonic) were evaluated. A novel hybrid equation combining a linear and a hyperbolic (Hill-type) region was used to obtain the T-V relationship and P-max of the participants, who were grouped by sex and age (young: 20-40 years; middle-aged: 40-60 years; and old: >= 60 years). Linear mixed-effect models were used to assess effects of time, sex, and age on T-V parameters, P-max, and body mass index (BMI). Additional analyses were performed to adjust for changes in daily protein intake and PAL. ResultsP(max) decreased in young men (-0.6% per year; P < 0.001), middle-aged men and women (-1.1% to -1.4% per year; P < 0.001), and older men and women (-2.2% to -2.4% per year; P <= 0.053). These changes were mainly related to decrements in torque at P-max at early age and to decrements in both torque and velocity at P-max at older age. BMI increased among young and middle-aged adults (0.2% to 0.5% per year; P < 0.001), which led to greater declines in relative P-max in those groups. S/T-0, that is, the linear slope of the T-V relationship relative to maximal torque, exhibited a significant decline over time (-0.10%T-0 center dot rad center dot s(-1) per year; P < 0.001), which was significant among middle-aged men and old men and women (all P < 0.05). Annual changes in PAL index were significantly associated to annual changes in P-max (P = 0.017), so the overall decline in P-max was slightly attenuated in the adjusted model (-5.26 vs. -5.05 W per year; both P < 0.001). ConclusionsP(max) decreased in young, middle-aged, and older adults after a 10-year follow-up. The early declines in P-max seemed to coincide with declines in force, whereas the progressive decline at later age was associated with declines in both force and velocity. A progressively blunted ability to produce force, especially at moderate to high movement velocities, should be considered a specific hallmark of aging.

Automated summary

This study evaluated the longitudinal changes in the torque-velocity relationship and maximum muscle power (P-max) of knee extensor muscles in young, middle-aged, and older adults after a 10-year follow-up. The results showed that P-max decreased with age, with early declines in force and later declines in both force and velocity.