Author(s): DEBOUTTE, J., DELECLUSE, C., THOMIS, M., VAN ROIE, E., Institution: KU LEUVEN, Country: BELGIUM, Abstract-ID: 234

INTRODUCTION:
Muscle power is essential for preserving functional capacity in older adults. It can be enhanced through power-focused resistance training, but optimal training loads remain unclear. Because force and velocity capacities differ between individuals, and power training adaptations are load- and velocity-specific, this study examined whether individualizing loads based on an older individual’s force-velocity profile improves power training outcomes compared with non-individualized training.
METHODS:
Force–velocity profiles were assessed in older adults (n = 80; ≥65 years) using a pneumatic leg press (Keiser A400). Each participant’s maximal force and maximal movement velocity were compared with the mean values of a younger reference group (n = 60; 20–35 years). Differences from the young reference values were converted to Z-scores. Older participants were classified as having a force–velocity imbalance when the absolute difference between their force and velocity Z-scores was ≥1. The type of deficit (force or velocity) was determined by the lower Z-score. Participants with a Z-score difference <1 were classified as neutral and excluded from the intervention. Fifty-nine participants exhibited velocity deficits, whereas only five showed force deficits. Due to the small number of participants with force deficits, statistical analyses were limited to those with velocity deficits, who completed a 12-week intervention and were assigned to either an individualized (IND) or non-individualized (NON-IND) program. Training was performed twice weekly: IND completed leg press progressive resistance training with low loads (40% one-repetition maximum [1-RM]) to target velocity deficits, while NON-IND trained with high loads (80% 1-RM). Force-velocity characteristics, muscle power and functional performance were assessed at baseline, 6 weeks and 12 weeks.
RESULTS:
IND demonstrated greater increases in maximal velocity compared with NON-IND (p = 0.003, d = 0.53 vs. p = 1.000, d = 0.01). In contrast, NON-IND showed greater increases in maximal force than IND (p < 0.001, d = 0.36 vs. p = 0.497, d = 0.17). Significant main effects of time were observed for maximal power (p < 0.001,) and all functional performance outcomes (p < 0.001 - 0.004), except stair climbing power (p = 0.135). No significant time × group interactions were detected for maximal power or functional performance outcomes (p > 0.05).
CONCLUSION:
Individualized power-focused resistance training led to force- and velocity-specific changes but did not produce greater improvements in muscle power or functional performance than non-individualized training. Tailoring loads based on F-v profiles may induce distinct adaptations but is not required to optimize power training outcomes in older adults.