(03) SIX-WEEKS OF POST-REHABILIATION RESISTANCE TRAINING ENHANCES QUADRICEPS AND HAMSTRINGS ISOMETRIC STRENGTH FOLLOWING KNEE SURGERY

The prevalence of orthopedic knee surgeries such as anterior cruciate ligament reconstruction (ACLR) continue to rise in the United States. Even after successful rehabilitation, there can still be between-limb asymmetries in function, potentially increasing the risk of a second injury.

Purpose: This investigation evaluated the changes in isometric strength of the quadriceps and hamstrings of both operative (OP) and non-operative (NOP) legs prior to (PRE) and after (POST) a 6-week training program completed after knee surgery rehabilitation.

Methods: Thirty (18 women, 12 men, mean±SD: 17.5±3.1 years, 204.6±56.3 days post-surgery) athlete’s training data were retrospectively documented from a secured online athlete management system. All participants had undergone knee surgery and a course of post-surgery rehabilitation. Participants trained twice weekly for 6-weeks following a periodized resistance training program designed to increase strength of both limbs. Peak force was measured via isometric handheld dynamometry for the quadriceps (QUADS) and hamstrings (HAMS) of both limbs at PRE and POST. Data were analyzed using separate 2x2x2 ANOVAs [leg (OP vs. NOP) x gender (men vs. women) x time (PRE vs. POST)] at p<u><0.05.

Results: Fifteen of the women participants and 8 of the men underwent ACLR with other surgeries including meniscectomy (n=3 men), matrix induced autologous chondrocyte implantation (n=2 women), and medial patellofemoral ligament reconstruction (n=2, 1 man and 1 woman). For QUADS peak force, there was no leg x gender x time interaction nor any two-way interactions (p-range = 0.14-0.92). However, there was a main effect for gender, leg, and time (all p<u><0.001). Follow-up analyses indicated that men had stronger QUADS than women by 14.5 kg [95% confidence interval (CI): 7.9-21.0 kg]. The NOP leg’s QUADS peak force was greater than OP by 2.7 kg (1.3-4.2 kg). From PRE to POST, the QUADS increased by 4.2 kg (95% CI: 2.8-5.7 kg) collapsed across legs and gender. For the HAMS, there was a 3-way interaction (p=0.033). Decomposition of this interaction revealed that men and women both increased HAMS by 6.1 kg (95% CI: 2.8-9.3 kg) and 2.4 kg (95% CI: 0.5-4.3 kg), respectively, over time and collapsed across legs as there was no leg x time interaction or leg main effect. Further, men were significantly stronger than women for HAMS peak force at both timepoints- PRE: 7.2kg (95% CI: 1.1-13.4 kg) and POST: 10.9 kg (95% CI: 4.0-17.8 kg). Lastly, the decomposed models indicated that there were no between-limb differences for HAMS peak force in either men or women or collapsed across gender.

Conclusion: Six-weeks of post-rehabilitation resistance training following knee surgery increased QUADS and HAMS peak force of both legs in both men and women. Despite the changes over time, QUADS peak force was still lowered in OP than NOP. PRACTICAL APPLICATION: Despite a structured rehabilitation program and a remedial 6-week training program after knee surgery, there were still significant differences between legs for peak force of the knee extensors. With the large role that knee extensor strength can play in secondary knee injuries, physical therapists, strength and conditioning coaches, sport scientists, and sports medicine professionals should all work concurrently to learn how best to attentuate the between-limb differences in strength continually observed after knee surgeries.

Acknowledgements: None.