Effects of hamstring-emphasized neuromuscular training on strength and sprinting mechanics in football players

The objective of this study was to examine the effects of a neuromuscular training program combining eccentric hamstring muscle strength, plyometrics, and free/resisted sprinting exercises on knee extensor/flexor muscle strength, sprinting performance, and horizontal mechanical properties of sprint running in football (soccer) players. Sixty footballers were randomly assigned to an experimental group (EG) or a control group (CG). Twenty-seven players completed the EG and 24 players the CG. Both groups performed regular football training while the EG performed also a neuromuscular training during a 7-week period. The EG showed a small increases in concentric quadriceps strength (ES=0.38/0.58), a moderate to large increase in concentric (ES=0.70/0.74) and eccentric (ES=0.66/0.87) hamstring strength, and a small improvement in 5-m sprint performance (ES=0.32). By contrast, the CG presented lower magnitude changes in quadriceps (ES=0.04/0.29) and hamstring (ES=0.27/0.34) concentric muscle strength and no changes in hamstring eccentric muscle strength (ES=-0.02/0.11). Thus, in contrast to the CG (ES=-0.27/0.14), the EG showed an almost certain increase in the hamstring/quadriceps strength functional ratio (ES=0.32/0.75). Moreover, the CG showed small magnitude impairments in sprinting performance (ES=-0.35/-0.11). Horizontal mechanical properties of sprint running remained typically unchanged in both groups. These results indicate that a neuromuscular training program can induce positive hamstring strength and maintain sprinting performance, which might help in preventing hamstring strains in football players.