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

Abstract

Objectives: To compare the effects of explosive and strength resistance training on neuromuscular and functional parameters in older adults and to analyze the relationship between changes in walking speed and improvements in plantar flexor (PF) neuromuscular parameters following interventions.

Methods: In total, 40 participants were randomly assigned to either an explosive resistance training group (EXG, n = 18; age = 80.41 ± 10.12 years; body mass index = 22.89 ± 2.77 kg/m²) or a strength resistance training group (STG, n = 22; age = 82.89 ± 5.32 years; body mass index = 23.81 ± 3.45 kg/m²). Both groups participated in the same PF resistance training regimen (three sessions per week for 12 weeks), engaging in identical exercises. However, EXG performed three to five sets of 12 to 14 repetitions at 40% to 45% of one-maximal repetition with a rapid concentric phase and a 3 s eccentric phase, while the STG performed three to four sets of 6 to 7 repetitions at 80% to 85% of one-maximal repetition, with both phases lasting approximately 3 s. Before and after the interventions, gait speed (m/s) was assessed using a 10 m walking test, and relative maximal force (Relative Fmax, 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 resistance training appears particularly effective in improving the ability to rapidly generate force, which is essential for many daily activities requiring explosive movements and quick responses.

Keywords: elderly; gait speed; maximum strength; rate of force development; strength training.

Figure 2

Setup for the maximal voluntary contraction test of the plantar flexors and parameter extraction.

Figure 1

Study design.

Figure 3

Comparative analysis of training metrics over the specialized training phase (10 weeks). (a) Predicted and realized volume load in explosive (EXG) and strength (STG) Groups. (b) Weekly progression of training load in explosive (EXG) and strength (STG) Groups. (c) Weekly training monotony in explosive (EXG) and strength (STG) Groups. (d) Weekly training strain in explosive (EXG) and strength (STG) Groups.

Figure 4

Comparison of walking speed between the two groups before and after the intervention. *: significant difference between before and after the intervention (p < 0.05); +: significant difference between groups (p < 0.05).

Figure 5

Relationships between walking speed and neuromuscular parameters of plantar flexors at baseline. (a) Relationship between gait speed and relative maximal force. (b) Relationship between gait speed and RFD 0–50. (c) Relationship between gait speed and RFD 100–200.

Figure 6

Relationships between ameliorations in gait speed and improvements in neuromuscular parameters of plantar flexors. (a) Relationship between Δ gait speed and Δ relative maximal force. (b) Relationship between Δ gait speed and Δ RFD 0–50. (c) Relationship between Δ gait speed and Δ RFD 100–200.