Qualitative and quantitative situational characteristics of muscle strains in sports: a systematic review and meta-analysis

OBJECTIVES: To explore the injury-inciting situational characteristics of indirect and non-contact muscle injuries in sports, commonly referred to as muscle strains; and to investigate differences and similarities of injury patterns across muscle groups. DATA SOURCES: PubMed, Web of Science, SPORTDiscus and Google Scholar. ELIGIBILITY CRITERIA FOR SELECTING STUDIES: Studies investigating injury-inciting situational characteristics (among others, injury contact mechanisms, joint positions, movement directions) of indirect and non-contact muscle injuries in sports through video recordings. RESULTS: Twenty-one studies reporting the injury-inciting situational characteristics of 728 indirect and non-contact muscle injuries were included. Non-contact mechanisms were more common (74%) than indirect contact mechanisms (26%). Most injuries were either running-related or occurred during sport-specific manoeuvres involving muscle-tendon unit length changes under active muscle contraction. For hamstring injuries, the most frequently reported injury kinematics comprised a knee joint position close to extension (underlying movement direction: flexion to extension) and a flexed hip joint position (underlying movement direction: variable). For adductor injuries, injury kinematics were characterised by rapid muscle lengthening due to hip extension, abduction and external rotation. For rectus femoris injuries, the observed injury kinematic comprised a flexing hip joint movement and extending knee joint movement. For calf injuries, the typical injury pattern comprised an ankle dorsiflexion movement with the knee being close to extension and the ankle in >10° dorsiflexion at the assumed injury time. CONCLUSION: This systematic review found distinct, identifiable injury patterns for indirect and non-contact muscle injuries. While similar situational characteristics were identified across injuries, some patterns were more specific to particular injury locations and sports. PROSPERO REGISTRATION NUMBER: PROSPERO registration number CRD42023472252.