Stride Mechanics and Strength Analysis of Lower Limbs in Runners with Medial Tibial Stress Syndrome vs. Asymptomatic Runners

Background: Street running has seen rapid growth due to its health benefits and accessibility, leading to a simultaneous rise in running-related injuries, particularly among recreational and professional street runners. Medial Tibial Stress Syndrome (MTSS) is a common injury affecting up to 15% of athletes and posing significant risks to runners of all levels of participation. Objective: This study aimed to investigate the strength and kinematic differences in the lower limbs of runners diagnosed with MTSS compared to asymptomatic runners. Methods: A total of 56 participants were divided into an MTSS group (27 runners) and a healthy control group (29 runners). Participants were evaluated for demographics, physical activity level, pain threshold using algometry, and running kinematics obtained through high-resolution 2D video analysis with Kinovea software. Lower-limb muscle strength was measured using an isometric Lafayette® digital dynamometer. Results: Although there were no significant differences in age or anthropometric measures, MTSS runners exhibited lower initial (∆% = 10.6%, p = 0.002) and intermediate (∆% = 8.7%, p = 0.026) running speeds. Pain assessment revealed significant lower pain thresholds in the MTSS group. Kinematic analysis identified greater foot-strike angles (left foot: ∆% = 31.9%, p = 0.004; right foot: ∆% = 25.9%, p = 0.0049) at initial speeds in MTSS runners, while other parameters like medial calcaneus rotation, push-off angles, and support time did not differ significantly. Additionally, MTSS runners demonstrated reduced strength in the quadriceps femoris (QF—Left QF: ∆% = −28.5%, p = 0.0049; Right QF: ∆% = −28.2%, p = 0.003). Conclusions: MTSS appears to affect female and male runners. MTSS may be attributed to a weaker quadriceps strength, higher heel contact angles during foot strike, or both, suggesting that interventions focusing on the improvement of these factors may be beneficial in preventing and treating MTSS.