The Neuromuscular Response to Eccentric Exercise-Induced Muscle Damage in Younger and Older Females: A Preliminary Study

The aging process is associated with many functional decrements. It is important to consider the additive acute functional decreases that may occur following eccentric exercise-induced muscle damage (EIMD). This study aimed to examine the effect of age on muscle damage metrics following EIMD. Ten younger (age=20±2 years, BMI=22.49±3.97 kg/m2) and six older (age=68±2 years, BMI=24.45±2.82 kg/m2) females participated in this study. Participants performed a maximal knee extensor EIMD protocol. Additionally, participants completed various assessments before, immediately after, 24-, 48-, and 72-hours after the EIMD protocol to evaluate the presence of and recovery from muscle damage. Assessments included B-mode ultrasound imaging of the rectus femoris (RF) and vastus lateralis (VL) to assess cross sectional area (CSA) and echo intensity (EI), soreness measures, and neuromuscular assessments (i.e., peak torque [PT] and rapid torque [RT]). A 2×5 ANOVA was used to compare age groups by time for all variables. Significant age × time interactions were found for RT at 200ms and 250ms (p<0.001) indicating a slower rate of recovery for the older group. Significant main effects for age were found for PT (p<0.001), maximal eccentric torque (p<0.001), VL CSA (p<0.001), RF CSA (p=0.03), RF EI (p=0.03), and all soreness measures (p<0.05). Overall, there were significant differences in performance, muscle morphology, and soreness between the younger and older females as well as significant differences in the late-phase RT recovery timeline. Practitioners should remain aware of the decreased functional abilities of female clients as they age and prescribe exercises appropriately.