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

Abstract

Substantial increases in joint range of motion (ROM) have been reported after 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 standardized difference (Hedge's g) with 95% confidence intervals. Results: Meta-analysis of 22 ROM outcomes (17 studies, 376 participants) revealed a large increase in lower-limb passive joint ROM (g = 0.86 (95% confidence intervals, 0.65-1.08)). Subgroup analyses revealed a moderate increase after 4-5 wk (g = 0.63 (0.27-0.98)), large increase after 6-8 wk (g = 0.98 (0.73-1.24)), and moderate increase after 9-14 wk (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.

Cross-Education Effects of Isokinetic Eccentric Plantarflexor Training on Flexibility, Strength, and Muscle–Tendon Mechanics

“…Simultaneous large increases in stretch tolerance (~96%), elastic energy storage (~161%), muscle fascicle length (~8%), and passive MTU stiffness (30%) were also detected. These findings are consistent with similar studies (31,32) and recent meta-analyses (26,29) highlighting the potential for eccentric training to simultaneously influence a broad range of neurological, mechanical, and architectural characteristics associated with ROM. These wide-ranging adaptations likely explain the substantially greater increases in ROM following eccentric training than those reported following muscle stretching programs (53), which are usually associated with a narrower neurological (i.e., stretch tolerance) adaptative profile (2,54).…”

“…One exercise mode that imposes substantial tissue loads and thus provides a large adaptive stimulus is eccentric-only exercise (23,24), which promotes greater gains in strength and muscle size (25) than concentric exercise and yet substantially and simultaneously improves ROM (26)(27)(28)(29). Indeed, a recent meta-analysis (29) reported a large effect (g = 0.86) of eccentric exercise on passive ROM across joints in the lower limb that was substantially greater than the effects previously reported (g = 0.29-0.49) after traditional resistance training or muscle stretching programs (30).…”

“…One exercise mode that imposes substantial tissue loads and thus provides a large adaptive stimulus is eccentric-only exercise (23,24), which promotes greater gains in strength and muscle size (25) than concentric exercise and yet substantially and simultaneously improves ROM (26)(27)(28)(29). Indeed, a recent meta-analysis (29) reported a large effect (g = 0.86) of eccentric exercise on passive ROM across joints in the lower limb that was substantially greater than the effects previously reported (g = 0.29-0.49) after traditional resistance training or muscle stretching programs (30). Furthermore, isokinetic forms of eccentric training showed particular promise with an even greater effect being observed (g = 1.09) despite the training dose being only half of that imposed in other studies, indicating it to be a more efficient yet more potent driver of ROM adaptation (29).…”

“…Indeed, a recent meta-analysis (29) reported a large effect (g = 0.86) of eccentric exercise on passive ROM across joints in the lower limb that was substantially greater than the effects previously reported (g = 0.29-0.49) after traditional resistance training or muscle stretching programs (30). Furthermore, isokinetic forms of eccentric training showed particular promise with an even greater effect being observed (g = 1.09) despite the training dose being only half of that imposed in other studies, indicating it to be a more efficient yet more potent driver of ROM adaptation (29). Like muscle stretching training, eccentric training can also result in increased stretch tolerance (31,32); however, additional adaptations are also commonly observed after eccentric training including increased fascicle length (26), a rightward shift in the force-length curve indicative of sarcomerogenesis (33), and the remodeling of both collagenous and noncollagenous extracellular matrix components (34).…”

“…These adaptations may have clinical relevance for populations (e.g., cerebral palsy, stroke, spinal cord injury) in which neurological impairment (e.g., spasticity) and abnormal extracellular matrix deposition (35,36) can result in the formation of contractures that result in high tissue stiffness, pain, and permanent muscle shortening that compromise ROM and muscle function. Although promising, the potential mechanisms underpinning the large increases in ROM after eccentric training remain unclear, with the relationships between changes in ROM and many mechanical or physiological variables rarely explored (29). This lack of mechanistic understanding is problematic as it limits our ability to intelligently modify these interventions to potentially improve efficacy or determine their suitability for clinical populations where these characteristics are often compromised.…”