The Effects of Eccentric Strength Training on Flexibility and Strength in Healthy Samples and Laboratory Settings: A Systematic Review

Abstract

Background: The risk of future injury appears to be influenced by agonist fascicle length (FL), joint range of motion (ROM) and eccentric strength. Biomechanical observations of the torque-angle-relationship further reveal a strong dependence on these factors. In practice, a longer FL improves sprinting performance and lowers injury risk. Classical stretching is a popular and evidenced-based training for enhancing ROM but does not have any effects on FL and injury risk. However, recent studies show that eccentric-only training (ECC) improves both flexibility and strength, and effectively lowers risk of injury.Objectives: To review the evidence on benefits of ECC for flexibility and strength.Methods: COCHRANE, PUBMED, SCOPUS, SPOLIT, and SPONET were searched for laboratory trials that compare ECC to at least one comparison group. Studies were eligible if they examined both strength and flexibility metrics in a healthy sample (<65 years) and met criteria for controlled or randomized clinical trials (CCT, RCT). 18 studies have been included and successfully rated using the PEDro scale.Results: 16 of 18 studies show strong evidence of strength and flexibility enhancements for the lower limb. While improvements between ECC and concentric training (CONC) were similar for eccentric (+19 ± 10% vs. +19 ± 11%) and isometric strength (+16 ± 10% vs. +13 ± 6%), CONC showed larger improvements for concentric strength (+9 ± 6% vs. +16 ± 7%). While for ROM ECC showed improvements (+9 ± 7%), no results could be found for CONC. The overall effectiveness of ECC seems to be higher than of CONC.Conclusion: There is clear evidence that ECC is an effective method for changes in muscle architecture, leading to both flexibility and strength improvements for the lower limb. Due to limited data no shoulder study could be included. Further research is needed for the upper body joints with a focus on functional and structural adaptions.Systematic Review Registration:https://www.crd.york.ac.uk/prospero/display_record.php?ID=CRD42021283248, identifier CRD42021283248

A 6-week randomized-controlled field study: Effect of isokinetic eccentric resistance training on strength, flexibility and muscle structure for the shoulder external rotator in male junior handball players

“…The sample consisted of 29 male junior handball players (German male handball division A and U23) from a local elite handball club (18.0 ± 1.6 years; 186.8 ± 6.3 cm; 84.8 ± 11.3 kg). Sample size was based on a preliminary study 30 and on comparable studies that calculated or suggested 13 to 16 participants per group. 23,31 The participants were randomly assigned to one of the two groups according to their playing position.…”

“…For these trials, a three-parametric e-function was fitted. 30 This enabled analyses for submaximal ROM and maximal ROM. SPM1d was also used to analyze the passive torque-angle curves.…”

“…22 Especially in the last decade, an increasing number of highly standardized eccentric training studies have been published for the lower limbs, but not for the shoulder. 19 Therefore, a research gap exists for eccentric strength training on the shoulder rotator cuff muscles 23 and for healthy junior handball players as a sample with high shoulder muscle demands and complaints. 24 Further, a fundamental research gap exists for the investigation of three-dimensional changes in muscle architecture.…”

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

“…To our knowledge, three reviews (29)(30)(31) have examined the effects of eccentric resistance training on ROM. However, in the first review (30), only three studies were included that directly measured joint ROM, whereas the remaining three studies measured fascicle length, which is not a valid indicator of ROM or its temporal change (32,33).…”

“…Nonetheless, in the updated review, only five studies included passive lower-limb ROM tests in healthy participants as an outcome measure, with the remainder examining fascicle length, imposing upper body interventions, or including clinical populations (tendinopathy). A similar recently published review (29) included 18 studies; however, many included studies examined fascicle length as an outcome measure, with only four studies measuring passive joint ROM and no meta-analysis performed. The inclusion of active ROM data, clinical populations, data from both the upper and lower body concurrently, and (importantly) fascicle length data as a proxy for ROM outcomes is problematic.…”