723 MEP159 – Acceleration profile of high-impact movements during a junior football game: focusing on the leg dominance

AbstractBackground In youth football, knee overuse injuries significantly burden participation and performance; particularly, Osgood-Schlatter disease is the common diagnosis of knee apophyseal injury in youth footballers, which often occurs in the support leg (non-dominant leg) rather than in the kick-preferred leg (dominant leg).Objective To clarify which leg (dominant or non-dominant leg) has the more frequent high (>6G) acceleration during football games by using a tri-axil accelerometer and video device.Design Observational study.Setting Youth athletes, local-tournament levels.Participants Seven junior male football players [mean (SD); 13.8 (0.6) yrs, 166.5 (4.9) cm, 50.5 (4.9) kg].Assessment of Risk Factors Movements that generated >6 G resultant accelerations were assessed as high-impact actions that would lead to microtrauma stress.Main Outcome Measurements Frequency and characteristics of the movements that generated >6G acceleration in each leg (dominant vs non-dominant leg).Results A total of 2,342 movements were confirmed as >6G accelerations during a 326-min game duration (7.19 cases/min; 95% confidence interval (CI), 6.90–7.48 cases/min). Compared with the dominant leg (3.24 cases/min; 95% CI, 3.04–3.43 cases/min), the non-dominant leg (3.80 cases/min; 95% CI, 3.59–4.01 cases/min) had a higher incidence of >6G accelerations. Deceleration actions, such as slow-down (1.66 case/min) and braking (1.18 case/min), were more frequent movements that generated high acceleration during youth football games. However, the >6G frequency of these deceleration movements did not differ between legs. In contrast, the frequency of running action in the non-dominant leg (0.86 case/min) was almost 1.6 times higher than in the dominant leg (0.54 case/min).Conclusions Frequency asymmetry in >6G accelerations appeared during youth football games. Repetitive running action, which creates a high impact in the non-dominant leg, will cause an accumulation of external load unilaterally. Coaches should check youth players' running behaviour during games to prevent knee overuse injury, often occurring in the non-dominant leg.