Effects of Explosive vs. Strength Resistance Training on Plantar Flexor Neuromuscular and Functional Capacities in Institutionalized Older Adults: A Randomized Controlled Trial.

Objectives: To compare the effects of explosive resistance training (RT) to strength RT on neu-romuscular and functional parameters and to analyze the relationship between changes in walking speed and improvements in plantar flexor (PF) neuromuscular parameters following interven-tions. Methods: 40 participants were randomly assigned to either an explosive RT group (EXG, n = 18; age = 80.41 ± 10.12 years; BMI = 22.89 ± 2.77 kg/m²) or a strength RT group (STG, n = 22; age = 82.89 ± 5.32 years; BMI = 23.81 ± 3.45 kg/m²). Both groups participated in the same PF RT regimen (3 sessions per week for 12 weeks), engaging in identical exercises. However, the EXG performed 3 to 5 sets of 12 to 14 repetitions at 40% to 45% of 1RM with a rapid concentric phase and a 3-second eccentric phase, while the STG performed 3 to 4 sets of 6 to 7 repetitions at 80% to 85% of 1RM, with both phases lasting approximately 3 seconds. Before and after the interventions, gait speed (m/s) was assessed using a 10-meter walking test, and relative maximal force (Relative F max, N/kg) was evaluated during maximal voluntary isometric contraction of PF. From the force-time curve, early (0 – 50 ms) and late (100 – 200 ms) rates of force development (RFD) were extracted from the linear slopes (Δ force / Δ time). Results: Gait speed significantly improved in both groups (p < 0.05). However, the improvement was more pronounced in the EXG compared to the STG (p < 0.05). Relative Fmax showed a more significant increase in the STG than in the EXG (p < 0.05). Moreover, a significant 10% increase in early RFD in the STG and a 20.1% increase in the EXG were observed (p < 0.05). The improvement in early RFD was greater in the EXG (p < 0.05). Additionally, late RFD improved significantly only in the EXG (+20.4%, p < 0.05). Conclusion: Explosive RT appears particularly effective in improving the ability to rapidly gen-erate force, which is essential for many daily activities requiring explosive movements and quick responses.