The Relationship between Hamstring Strength and Performance following ACL Reconstruction.
The anterior cruciate ligament (ACL) injury of the knee is one of the most common injuries an athlete may experience throughout his or her athletic career. Following an ACL Reconstruction (ACLR), 81% of patients return to sport, 65% return to their pre-operative sports participation level and only 55% return to competitive sports. The priority of an ACLR is to restore stability of the knee joint as well as the capacity of its dynamic stabilizers to perform their prospective functions. The hamstring muscle group resists anterior tibial translation and is therefore protective of the ACL. Literature consisting of cross-sectional studies demonstrated a 20-28% hamstring strength deficit in the surgical limb of ACLR participants compared to the non-surgical limb, 10 years post-operation. Strength deficits can be addressed during strength training. During a 4-week hamstring strength training program, researchers noticed a 19.4% increase in knee flexion angle towards full extension during the post-training tests. Researchers also noticed as the knee flexion angle of peak torque changed to a more extended knee, the vertical jump heights from the participants increased by 6.6% between pre- and post-training sessions. With the literature in mind, neglecting the importance of hamstring strength deficits after an ACLR, potentially puts the athlete at risk for re-injury and suboptimal performance. The purpose of this study was to determine if hamstring muscle strength and the knee angle of peak hamstring torque following ACL reconstruction affect performance. This project utilized data from a previously approved IRB study in order to address the purpose of this study. Ten participants who had undergone an ACL reconstruction within the past 5 years as well as ten healthy participants completed the study. All participants performed maximal efforts on a dynamometer, and knee angle at peak hamstring torque and peak hamstring torque were measured under isometric and isokinetic conditions. The performance measures were single leg hop distance, triple leg hop distance and timed 6-meter hop distance. The strength measurements were normalized to participant mass. Correlations of the strength and performance variables on the injured limbs were conducted in each group. For the ACLR group, single leg hop distance had a significant correlation (.644, p<.05) with isokinetic hamstring strength; Triple leg hop distance had a significant correlation (.669, p<.05) with isometric hamstring strength. Lastly, the timed 6-meter hop distance had a significant negative correlation (-.710, p<.01) with isokinetic hamstring strength. In the healthy group, only the triple hop distance had a significant correlation (.773, p<.01) with isokinetic hamstring strength. The importance of this thesis was to establish the functional effects of hamstring strength deficits following an ACLR because the importance of hamstring strength tends to be overlooked. Due to the limitation of sample size, further research should be conducted with larger sample sizes to establish stronger correlations between hamstring strength and performance.
Mitchell, Dasia. (May 2021). The Relationship between Hamstring Strength and Performance following ACL Reconstruction. (Honors Thesis, East Carolina University). Retrieved from the Scholarship. (http://hdl.handle.net/10342/9217.)
Mitchell, Dasia. The Relationship between Hamstring Strength and Performance following ACL Reconstruction.. Honors Thesis. East Carolina University, May 2021. The Scholarship. http://hdl.handle.net/10342/9217. October 06, 2022.
Mitchell, Dasia, “The Relationship between Hamstring Strength and Performance following ACL Reconstruction.” (Honors Thesis., East Carolina University, May 2021).
Mitchell, Dasia. The Relationship between Hamstring Strength and Performance following ACL Reconstruction. [Honors Thesis]. Greenville, NC: East Carolina University; May 2021.
East Carolina University