Effects of Eccentric Resistance Training on Lower-limb Passive Joint Range of Motion: A Systematic Review and Meta-analysis

Introduction: Substantial increases in joint range of motion (ROM) have been reported following eccentric resistance training, however between-study variability and sample size issues complicate the interpretation of the magnitude of effect.

Methods: PubMed, Medline and SPORTDiscus databases were searched for studies examining the effects of eccentric training on lower-limb passive joint ROM in healthy human participants. Meta-analysis used an inverse-variance random-effects model to calculate the pooled standardised difference (Hedge's g) with 95% confidence intervals (CI).

Results: Meta-analysis of 22 ROM outcomes (17 studies; 376 participants) revealed a large increase in lower-limb passive joint ROM (g = 0.86 [CI = 0.65, 1.08]). Subgroup analyses revealed a moderate increase after 4-5 weeks (g = 0.63 [0.27, 0.98]), large increase after 6-8 weeks (g = 0.98 [0.73,1.24]), and moderate increase after 9-14 weeks (g = 0.75 [0.03, 1.46]) of training. Large increases were found in dorsiflexion (g = 1.12 [0.78, 1.47]) and knee extension (g = 0.82 [0.48, 1.17]), but a small increase in knee flexion was observed (g = 0.41 [0.05, 0.77]). A large increase was found after isokinetic (g = 1.07 [0.59, 1.54]) and moderate increase after isotonic (g = 0.77 [0.56, 0.99] training.

Conclusions: These findings demonstrate the potential of eccentric training as an effective flexibility training intervention and provide evidence for 'best practice' guidelines. The larger effect after isokinetic training despite <50% training sessions being performed is suggestive of a more effective exercise mode, although further research is needed to determine the influence of contraction intensity and to confirm the efficacy of eccentric training in clinical populations.