European Journal of Applied Physiology

, Volume 117, Issue 11, pp 2335–2354 | Cite as

Cross-education of muscular strength following unilateral resistance training: a meta-analysis

Original Article

Abstract

Purpose

Cross-education (CE) of strength is a well-known phenomenon whereby exercise of one limb can induce strength gains in the contralateral untrained limb. The only available meta-analyses on CE, which date back to a decade ago, estimated a modest 7.8% increase in contralateral strength following unilateral training. However, in recent years new evidences have outlined larger contralateral gains, which deserve to be systematically evaluated. Therefore, the aim of this meta-analysis was to appraise current data on CE and determine its overall magnitude of effect.

Methods

Five databases were searched from inception to December 2016. All randomized controlled trials focusing on unilateral resistance training were carefully checked by two reviewers who also assessed the eligibility of the identified trials and extracted data independently. The risk of bias was assessed using the Cochrane Risk-of-Bias tool.

Results

Thirty-one studies entered the meta-analysis. Data from 785 subjects were pooled and subgroup analyses by body region (upper/lower limb) and type of training (isometric/concentric/eccentric/isotonic–dynamic) were performed. The pooled estimate of CE was a significant 11.9% contralateral increase (95% CI 9.1–14.8; p < 0.00001; upper limb: + 9.4%, p < 0.00001; lower limb: + 16.4%, p < 0.00001). Significant CE effects were induced by isometric (8.2%; p = 0.0003), concentric (11.3%; p < 0.00001), eccentric (17.7%; p = 0.003) and isotonic–dynamic training (15.9%; p < 0.00001), although a high risk of bias was detected across the studies.

Conclusions

Unilateral resistance training induces significant contraction type-dependent gains in the contralateral untrained limb. Methodological issues in the included studies are outlined to provide guidance for a reliable quantification of CE in future studies.

Keywords

Contralateral training Strength Resistance training Meta-analysis 

Abbreviations

CE

Cross-education

CI

Confidence interval

I2

Inconsistency statistic

RCT

Randomized controlled trial

RM

Repetition maximum

SD

Standard deviation

SMD

Standardized mean difference

Notes

Compliance with ethical standards

Conflict of interest

The authors declare that they have no conflict of interest.

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Copyright information

© Springer-Verlag GmbH Germany 2017

Authors and Affiliations

  1. 1.Department of Biomedical SciencesUniversity of SassariSassariItaly
  2. 2.Department of Physical Therapy, Sackler Faculty of MedicineTel Aviv UniversityTel AvivIsrael

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