Risk Factor Identification and Precision Exercise Intervention for Common Injuries in Recreational Runners Based on Machine Learning

1. Participants This prospective study recruited recreational runners from East China Normal University between November and December 2024 through poster advertisements and WeChat-based recruitment. Eligible participants were male recreational runners aged 18 to 30 years with a weekly running distance greater than 10 km and no history of lower-limb injury within the past three months. Exclusion criteria included: (1) the presence of other musculoskeletal or tissue injuries, such as arthritis, muscle injuries, or meniscal injuries; (2) a history of lower-limb surgery; and (3) regular participation in contact or high-impact sports, in order to minimize potential confounding effects from non-running-related musculoskeletal injuries.

A priori sample size estimation was performed using GPower software (GPower V3.1, Heinrich-Heine-Universität Düsseldorf, Germany). With a significance level of α = 0.05, statistical power of 0.80, and an effect size of 1.7, the minimum required sample size was estimated to be 170 participants. Considering an anticipated attrition rate of 20%, a total of 204 participants were ultimately recruited.

All participants were subsequently followed prospectively for 6 months and classified into four groups based on injury status: injury-free, chronic Achilles tendinopathy, MTSS, and PFP. Diagnostic criteria for chronic Achilles tendinopathy included: (1) insidious Achilles tendon pain aggravated by weight-bearing activities and worse in the morning and/or at the onset of activity; (2) pain and swelling located 2-6 cm proximal to the Achilles tendon insertion; (3) ultrasonographic evidence of tendon thickening >7 mm or >20% compared with the contralateral side; and (4) symptoms persisting for more than 3 months.

MTSS was defined as: (1) diffuse medial tibial pain during exercise with a palpation tenderness area of at least 5 cm; (2) symptom duration of at least 3 weeks; and (3) absence of stress fracture or other fractures on radiographic examination.

PFP was defined as: (1) pain around or behind the patella during at least two activities such as running, squatting, stair ascent/descent, prolonged sitting, jumping, or resisted knee extension; (2) pain not attributable to direct trauma and persisting for at least 3 months; and (3) a minimum pain intensity of ≥3 on a 10-cm Visual Analog Scale (VAS), where 0 indicates no pain and 10 indicates maximal pain.