Author(s): SESHADRI, D., AMITRANO, J., ZARRINFAR, M., GIULIANI, M., CAHILL, K., Institution: LEHIGH UNIVERSITY, Country: UNITED STATES, Abstract-ID: 2167

INTRODUCTION:
Return to play (RTP) metrics post ACL-R are measured through six different external parameters. Four of these parameters compare the ACL-R limb to the contralateral limb, attempting to approach symmetry in the limbs. While external symmetry aids in the ability to understand where in the recovery process the athlete is, an internal parameter could increase the accuracy of the assessment by providing insights into the underlying biomechanical and physiological factors influencing the athletes performance. Muscle oxygen saturation (SmO2) has emerged as a biomarker of interest to quantify changes in muscle function during workouts. We hypothesize that differences in SmO2 could be attributed to less efficient O2 use in the ACL-R limb compared to the contralateral limb. The ultimate objective is to mitigate reinjury risks by tailoring rehabilitation strategies based on a comprehensive understanding of the athletes physiological responses and promoting symmetrical recovery patterns. This study seeks to utilize SmO2 as an objective internal variable to guide return to sport following ACL-R.
METHODS:
In this study, approved by the Lehigh University Institutional Review Board at Lehigh University, we utilized near-infrared spectroscopy (NIRS) to assess SmO2 differences in the vastus medialis muscle. Additionally, we utilized a heart rate monitor to assess alterations in cardiac function among four Division 1 football athletes, aged 18-22, at various stages after ACL-R surgery. Measurements were taken during distinct rehabilitation time points. The athletes performed two sets of 20 repetitions of quad sets and single-leg raises.
RESULTS:
Our ongoing study has yielded promising initial evidence regarding SmO2 convergence between the collateral and surgical legs during rehabilitation exercises for athletes within 4 months post ACL-R surgery. The data collected showed an average SmO2 of 70% for surgical and 50% for contralateral within one month of surgery. At around 4 months, on average, SmO2 for surgical was 58% and contralateral was 62%. Notably, we observed a convergence in SmO2% after this relatively short period, which deviates from the expected 6-month timeline. To further validate these findings, our future work will focus on expanding the sample size to ensure robustness and generalizability. By doing so, we aim to provide valuable insights that can inform rehabilitation strategies and enhance return-to-play protocols for Division 1 football athletes recovering from ACL-R surgery.
CONCLUSION:
Our investigation into SmO2 variations in the vastus medialis following ACL-R surgery has found asymmetries between the surgical and contralateral legs. This highlights the critical importance of continuous monitoring of SmO2 during rehabilitation to tailor recovery strategies effectively. The findings not only contribute valuable insights for optimizing physiological responses and refining return-to-play protocols in athletes but also to other areas in medicine where atrophy occurs.