Evaluating Isometric Mid Thigh Pull As A Predictor Of Non Contact Acl Injury Risk In Athletes

Non-contact anterior cruciate ligament (ACL) injuries are common in athletes, especially during high-impact sports involving rapid directional changes and landing. Assessing injury risk factors is crucial, as these injuries can have long-term impacts. PURPOSE: This study investigates the role of the isometric mid-thigh pull (IMTP) in evaluating non-contact ACL injury risk, focusing on key strength metrics like peak force (PF) and rate of force development (RFD). Previous research indicates that sufficient muscle strength, particularly in the lower limbs, is essential for reducing ACL stress during landing, with knee valgus and reduced force production linked to greater injury risk. METHODS: In this study, seven female competitive university-level athletes (age 19.5 ± 0.7 y, height 164.2 ± 8.1 m, weight 60.4 ± 5.9 kg), with ≥2 years of training performed IMTP tests under bilateral (IMTPBi) and unilateral (IMTPUni) stances, with data captured via dual force plates and Vicon cameras. Testing included three trunk positions: leaning forward (LFL), self-selected (SSL), and upright landing (URL). Standardized IMTP trials were conducted with knee angles maintained at 120–130° and trunk position kept steady to simulate athletic stances. Data was sampled at 1000 Hz, capturing PF and RFD to represent maximal isometric strength and quick force-generation capabilities. RESULTS: Correlation analyses were used to evaluate the relationship between joint kinematics and maximum knee strength. The findings revealed a strong correlation (Bilateral r = 0.93, p < 0.05; Unilateral r = 0.83, p < 0.05) between IMTP variables and safe landing mechanics. Athletes with higher PF in IMTP (mean ± SD PF: 1900 ± 100 N for bilateral and 1050 ± 100 N for unilateral) displayed reduced knee valgus angles and minimized shear forces, both factors significantly associated with lower ACL strain. In particular, the LFL position showed a marked reduction in ACL stress, correlating with increased knee flexion (p < 0.05). Conversely, the URL position heightened ACL load due to limited knee flexion and increased quadriceps demand. DISCUSSION: These results indicate that IMTP testing offers valuable insights into ACL injury risk, with higher isometric strength supporting safer biomechanics during landing.