# The effect of post-activation potentiation on neuromuscular activation of smashing technique during the recovery period of meniscal injuries in elite badminton players: non-negative matrix factorization-based muscle and time-frequency coherence

## TL;DR

This study examines how different post-activation potentiation methods affect muscle coordination in elite badminton players recovering from meniscus injuries.

## Contribution

The study introduces a novel approach using non-negative matrix factorization and time-frequency coherence to analyze neuromuscular activation during a specific badminton technique.

## Key findings

- Neuromuscular electrical stimulation significantly increased muscle activation weights in key lower limb muscles.
- The resistance band group showed a higher number of synergies compared to other groups.
- Electrical stimulation improved intermuscular coherence across multiple frequency bands in trunk-limb muscle pairs.

## Abstract

To investigate the effects of three distinct post-activation potentiation (PAP) interventions—neuromuscular electrical stimulation (NMES), elastic band resistance, and squats—on neuromuscular activation during the smashing technique in high-level badminton athletes recovering from meniscus injuries. Furthermore, to elucidate the underlying mechanisms at the neuromotor control level through analyses of muscle synergy and intermuscular coherence.

Eighteen high-level male badminton athletes in the recovery phase of meniscus injuries were recruited. Surface electromyographic signals were recorded during forehand smash execution following respective interventions: squats, elastic band resistance, and NMES. Non-negative matrix factorization (NMF) analyzed muscle synergies, extracting synergistic module counts, muscle weights, and activation duration parameters. Time-frequency coherence (TFC) was calculated for specific muscle pairs.

The resistance band group (RBG) exhibited a significantly higher number of synergies (5.0 ± 0.63) compared to the squat group (SG) (3.33 ± 0.52, p = 0.005) and the electrical stimulation group (ESG) (2.33 ± 0.82, p < 0.001). In terms of muscle activation weights, the ESG showed markedly increased contributions from key lower limb muscles across multiple synergy modules. E.g., in SYN4, activation weights for gastrocnemius medialis (GM) and lateralis (GL) in the ESG (GM: 0.25 ± 0.31; GL: 0.28 ± 0.28) were significantly higher than in the SG (GM: 0.08 ± 0.20; GL: 0.06 ± 0.09) (p < 0.05), representing an increase exceeding 200%. Intermuscular coherence analysis revealed that the ESG demonstrated superior coherence across α, β, and γ bands for several trunk–limb muscle pairs. E.g., within the α band, the biceps BB–LD pair in the ESG was significantly higher than in both the SG (p = 0.002) and the EBG (p = 0.007).

Neuromuscular electrical stimulation effectively optimizes muscle coordination patterns during smash execution in athletes recovering from meniscal injuries. It enhances activation of key muscle groups and multi-band neural coordination, representing an efficient rehabilitation strategy for neuromuscular control function optimization.