Is resistance training intensity adequately prescribed to meet the demands of returning to sport following anterior cruciate ligament repair? A systematic review

Objective: To identify, critique and synthesise the research findings that evaluate the use of resistance training (RT) programmes on return to sport outcome measures for people following ACL repair (ACLR).

Design and data sources: This systematic review included a comprehensive search of electronic databases (EBSCO health databases (CINAHL, MEDLINE, SPORTDiscus), Scopus and Pedro) performed in June 2020 and was guided by the Preferred Reporting Items for Systematic Reviews and Meta-Analyses checklist. Studies were appraised using the Downs and Black checklist.

Eligibility criteria: Randomised and non-randomised controlled trials, longitudinal cohort studies and case series were considered for inclusion where an adequate description of the RT intervention was provided as a part of the study's ACLR rehabilitation protocol. Articles that did not include outcome measures related to return to sport criteria were excluded.

Results: Eleven articles met the inclusion criteria and were subjected to appraisal and data extraction. Study quality ranged from poor to excellent. RT intensity varied considerably among studies (between 5% and >80% of one repetition maximum). Only one identified study specifically investigated the effect of a low-intensity versus high-intensity RT protocol. The majority of studies reported participant outcomes that would not meet commonly used return to sport criteria.

Conclusion: There appears to be considerable variation in the intensity of RT prescribed in research for people following ACLR. Furthermore, in most of the identified studies, RT protocols promoted muscle endurance and hypertrophy without progressing to strength or power-based RT. The findings of this review provide insight into potential factors limiting returning to sport and contributing to reinjury for people following ACLR.