Age and gender differences in hip extension and flexion torque steadiness.

BACKGROUND: Lower extremity torque steadiness has been shown to be an independent predictor of functional performance in older women. Hip muscle function is crucial for many types of activities of daily living, yet existing studies investigating torque steadiness for lower extremities are limited to assessing steadiness at the knee and ankle.
OBJECTIVE: The purpose of this study was to compare age and gender differences in hip extension (HE) and flexion (HF) strength, torque steadiness, and torque accuracy (TA).
METHODS: Twenty young adults (10 men, 10 women; age 24.0 ± 2.2 years) and 21 older adults (11 men, 10 women; age 65.4 ± 4.5 years) matched across age for height and body mass participated. Dominant leg HE and HF isometric strength was assessed by maximal voluntary contractions (MVC); relative (5, 25 and 50% MVC) and absolute (25 Nm) torque steadiness were assessed as standard deviation and coefficient of variation of torque fluctuations, and TA was determined as the mean deviation from target torque levels.
RESULTS: MVC was lower for HF than HE (p = 0.007), but HE had greater torque fluctuations (p < 0.05). For HE, the coefficient of variation of 5% MVC was greater for older than young adults (p < 0.05) and greater for women than men (p < 0.05). For HF torque steadiness there were no age or gender differences (p > 0.05). For both HE and HF, older adults were less accurate (higher TA) than their young counterparts at 25 Nm (p < 0.022).
CONCLUSIONS: Our results indicate older as compared to young adults, and women as compared to men are less steady (greater torque fluctuations) in HE at 5% MVC target torque levels, but not at higher torque levels. For HF, torque steadiness is similar across low to high target torque levels in both genders and across younger and older adults. For both HE and HF, TA is impaired in older compared to young adults at absolute target torque levels, but not at relative torque levels.