Cross-education of muscular strength following unilateral resistance training: a meta-analysis
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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.
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.
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.
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.
KeywordsContralateral training Strength Resistance training Meta-analysis
Randomized controlled trial
Standardized mean difference
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest.
- Beyer KS, Fukuda DH, Boone CH, Wells AJ, Townsend JR, Jajtner AR, Gonzalez AM, Fragala MS, Hoffman JR, Stout JR (2016) Short-term unilateral resistance training results in cross education of strength without changes in muscle size, activation, or endocrine response. J Strength Cond Res 30:1213–1223CrossRefPubMedGoogle Scholar
- Cohen J (1988) Statistical power analysis for the behavioral sciences, 2nd edn. Lawrence Earlbaum Associates, HillsdaleGoogle Scholar
- Dvir Z (2004) Isokinetics: muscle testing, interpretation, and clinical applications. 2nd edn, Elsevier Health Sciences, AmsterdamGoogle Scholar
- Goodwill AM, Kidgell DJ (2012) The effects of whole-body vibration on the cross-transfer of strength. Sci World J 2012:504837. doi: 10.1100/2012/504837
- Kannus P, Alosa D, Cook L, Johnson RJ, Renström P, Pope M, Beynnon B, Yasuda K, Nichols C, Kaplan M (1992) Effect of one-legged exercise on the strength, power and endurance of the contralateral leg. A randomized, controlled study using isometric and concentric isokinetic training. Eur J Appl Physiol Occup Physiol 64:117–126CrossRefPubMedGoogle Scholar
- Kraemer WJ (1994) General adaptations to resistance and endurance training programs. In: Baechle T (ed) Essentials of strength training and conditioning. Human Kinetics, Champaign, pp 127–150Google Scholar
- Manca A, Ginatempo F, Cabboi MP, Mercante B, Ortu E, Dragone D, De Natale ER, Dvir Z, Rothwell JC, Deriu F (2016b) No evidence of neural adaptations following chronic unilateral isometric training of the intrinsic muscles of the hand: a randomized controlled study. Eur J Appl Physiol 116:1993–2005CrossRefPubMedGoogle Scholar
- Manca A, Cabboi MP, Dragone D, Ginatempo F, Ortu E, De Natale ER, Mercante B, Mureddu G, Bua G, Deriu F (2017) Resistance training for muscle weakness in multiple sclerosis: direct versus contralateral approach in individuals with ankle dorsiflexors’ disparity in strength. Arch Phys Med Rehabil. doi: 10.1016/j.apmr.2017.02.019 (Epub ahead of print) Google Scholar
- Scripture EW, Smith TL, Brown EM (1894) On the education of muscular control and power. Stud Yale Psycol Lab 2:114–119Google Scholar