Combined Training Outperforms Single-form in Improving Lower Extremity Reactive Strength Index: A Network Meta-Analysis

Abstract

Background

The Reactive Strength Index (RSI) is an important indicator of explosive strength. Various training methods, such as plyometric training (PJT), resistance training (RT), velocity-based training (VBT), and sprint training (SP), are widely employed to enhance RSI. While the evidence is not yet definitive, combined training methods appear to be more effective than single-form training in improving RSI.

Objectives

To examine the effects of different training modalities on lower-extremity reactive-strength indices and to determine whether age, sex, or training level moderates these effects.

Methods

A comprehensive search across five databases (Web of Science, PubMed, Scopus, Elsevier, and Springer) was performed without time constraints, targeting studies published in English. Relevant literature was identified using established inclusion and exclusion criteria, and study quality was assessed with the Cochrane Risk of Bias Tool (RoB 2.0). Fixed-effects or random-effects models were selected to combine effect sizes depending on the degree of heterogeneity, using standardized mean differences (SMD) for analysis. Subgroup and sensitivity analyses particularly emphasized plyometric training. Additionally, a Bayesian network meta-analysis compared direct and indirect results, utilizing the Deviance Information Criterion (DIC) for model consistency and node-splitting methods to assess discrepancies in comparisons. Publication bias was evaluated through Egger’s regression test and funnel plots.

Results

This review included 39 studies (1540 participants). Nine studies were assessed as having a high risk of overall bias, which likely included biases in the randomization process and the selection of reported results. Meta-analysis indicated that all interventions improved the RSI, with significant effects from balance + plyometric training (SMD = 0.25, P < 0.01) and French contrast method (FCM) training (SMD = 0.20, P < 0.01). Subgroup analyses indicated that training level (athletes vs. non-athletes) and age group (children, adolescents, adults) significantly moderated effect sizes only under the fixed-effects model (P < 0.01); these differences became non-significant in the random-effects model (P = 0.11–0.19), suggesting that between-study heterogeneity obscures subgroup distinctions. Sex did not explain heterogeneity in any model (all P > 0.05). In a network meta-analysis of 51 studies, the consistency model yielded a DIC value of 260.3, with no significant differences between direct and indirect comparisons. The intervention with the highest surface under the cumulative ranking was FCM (SUCRA = 0.95). Egger’s test showed no publication bias (P = 0.66).

Conclusion

Combined plyometric-based methods improve reactive strength irrespective of sex; any age- or training-related effects are model-dependent and of minor practical relevance. These findings may help people improve lower extremity reactive strength more efficiently.

PROSPERO registration number: CRD420250635723.

Keywords

Plyometric training / Reactive strength index / Resistance training

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Funding

2020 Humanities and Social Science Fund of Ministry of Education of China(20YJA8900 29)

RIGHTS & PERMISSIONS

The Author(s)