The effect of exercise time and frequency on the development of cam morphology.

objectiveFemoroacetabular impingement syndrome (FAIS) with cam morphology is a prevalent cause of intra-articular hip pain in young adults and is widely associated with sporting activity during skeletal immaturity. The exact association between activity levels and cam morphology is not fully understood. This scoping reviews aims to (1) systematically map the available evidence regarding the association between physical activity levels and cam morphology and (2) elucidate the nature of this association, examining whether a threshold effect exists at specific training intensities or durations that could inform preventative guidelines.

methodsA systematic literature search of Embase, MEDLINE and the Cochrane Library was conducted following the PRISMA-ScR guidelines. Studies investigating the association between activity levels and cam were included. Data was charted and summarised narratively with illustrative figures displaying the odds ratio for cam prevalence and the mean difference in α-angle values between high and low activity groups. Data on training time and cam prevalence were plotted to visualise potential dose-response relationships and threshold effects. Study quality was assessed using the Downs and Black criteria.

resultsThe search identified nine studies involving 890 participants (684 males, 206 females). The methodological quality of the included studies ranged from 44 to 95%, with higher percentages indicating better quality. High activity groups showed greater prevalence of cam morphology per individual and per hip compared to low activity groups. α-angle values were also greater in high activity groups. Evidence was heterogeneous in cam prevalence measurement methods, definitions of activity groups and study populations. Inconsistent reporting of exercise time and frequency precluded meaningful characterisation of their association with cam morphology.

conclusionThis review maps evidence suggesting that cohorts reporting high sporting activity levels (approximately 3-8 training sessions per week or 3.5-12.5 h of weekly training) have greater prevalence of cam morphology and larger α-angle values compared to less active cohorts. Significant knowledge gaps exist in the understanding of the relationship between exercise time and frequency and cam development. Prospective cohort studies with standardised reporting of activity levels and clear stratification of adolescent sporting activity are needed to better characterise this relationship and inform evidence-based guidelines for youth sports participation. CLINICAL TRIAL NUMBER: Not applicable.