Hamstring Function After ACL Reconstruction

A recent study aimed to outline evidence-based recommendations for the recovery of hamstring muscle function after ACL reconstruction.

The summary of this paper you’ll read below is actually a snippet of our Research Review service, where we have industry experts break down the most recent and clinically relevant research for you. Learn more about this service here.

STUDY: Recommendations for Hamstring Function Recovery After ACL Reconstruction – Buckthorpe et al (2020)

This study was reviewed by Dr Teddy Willsey in the February 2021 issue of the Research Reviews.

Key points from the study:

• Early emphasis on quadriceps strengthening in ACL rehabilitation has potential to overshadow the need for hamstring strengthening.
• Deficits in knee flexion strength can play a large role in ACL re-injury and should be more carefully measured during the return to sport decision-making process.

Okay, let’s dive into the rest!

Background and Objective:

Considerable deficits have been reported in hamstring function in the early post-operative period following anterior cruciate ligament (ACL) repair, as well as in the return to sport (RTS) period.

The aim of this paper was to discuss important alterations of the hamstring muscles after ACL reconstruction (ACLR), consider their implications for program design, and guide clinicians on how to apply this information.

Methods:

The authors wrote a review article utilizing 217 papers on a variety of topics on ACLR, hamstring injury, and the lower extremity. The paper provided a sample template for ACLR rehab, an example of periodized progression through exercise prescription, and extensive citations from a range of papers with varying levels of evidence.

Results:

The use of hamstring tendon graft in ACLR can result in chronic neuromuscular inhibition and persistent hamstring strength deficits more pronounced during eccentric than concentric activation. At 6 months post-op, 67% of patients with patellar tendon graft had an average knee flexor limb symmetry index (LSI) >90%, while only 46% of patients with hamstring tendon graft achieved this symmetry.

Evidence suggests training at longer muscle lengths can produce similar strength gains and muscle architecture changes to eccentric training, indicating potential utility for longer muscle length hamstring training during ACLR rehabilitation. Hamstring exercises performed with the hip flexed are thought to have greater dynamic correspondence to the functional requirements of the hamstring in locomotion.

Limitations:

This paper serves as a generalized review. Although informative, it lacks a systematic approach to article selection and does not carry statistical power.

Clinical Implications:

Hamstring strengthening during ACL rehabilitation should be periodized and carefully planned, exposing patients to increasing muscle lengths, intensities and velocities over time. It should include both short and long muscle length exercises, a mixed approach of hip extension and knee flexion, a specific focus on eccentric strength at long muscle lengths, and high-speed running.

Shorter muscle length exercises might be preferable during the early post-operative period, such as the prone leg curl, standing leg curl, and bridge. During later stages, the Nordic hamstring exercise represents a short muscle length hamstring exercise focused on maximal eccentric strength. Longer muscle length exercises that incorporate hip hinge patterns train the proximal hamstring fibers to a greater degree, such as the Romanian deadlift, 45-degree back extension, and kettlebell swing.

Sprinting is arguably the most effective hamstring exercise there is, as it incorporates rapid angular velocities and high demands of both hip extension and knee flexion and has the greatest carryover to sport performance for field athletes.

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Here’s the 11 other studies from our February issue just published here:

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• Physical Activity Promotion Among Physiotherapists