Tuesday, April 2, 2013

Leg Strength, Sprint Speed and Jump Performance

Soccer players typically perform around a dozen sprints during the course of a 90 minute match. In the 2010 World Cup Finals, Mexican forward Javier Hernandez reached a top speed of more than 32 km/hr (close to 20 miles per hour). There is no doubt that sprint speed is an important player characteristic that can have an important impact on performance. For example, during a breakaway, it is the faster player who either outruns his or her defender or closes down the open forward. What factors make an athlete fast? Is sprint speed something that can be improved with training or just a natural gift? Researchers at the University of Salford and several English football clubs found that on key component of sprinting is leg strength with stronger players being among those who are fastest. Their findings also have important implications for how young players can be trained in order to develop their sprint speed.

The study was conducted in conjunction with the youth programs at three professional clubs: Manchester City, Charlton and Southend United. The subjects for the study were 34 male players with an average age of 17 years. They were tested on maximal back squat strength, jump performance and sprint performance (5m and 20m). For the back squat, the subjects’ 1-repitition maximum (1RM) was determined using a “repetitions to failure” protocol (this was done to minimize injury risk associated with performing a true 1RM). Vertical jump heights were measured using both counter movement and a squat jumps. Finally spring speed was determined using photocell timers placed at 5m and 20m beyond the starting gate.

The researchers found that performance on all three tasks were closely correlated. Greater squat strength was associated with higher jump height as well as faster 5m and 20m sprint times. Interestingly, absolute squat strength was more closely linked to 5m and jump performances whereas relative strength (1RM divided by body mass) was more closely linked to 20m sprint time.

It should be pointed out that the correlations indicated good relationships among the performance variables. However, they were not considered overly strong. For example, the relative strength explained about 45% of the variability in 20m sprint time. This suggests that strength is an important contributor to sprinting ability. But, it also means that other factors, those not measured in the study accounted for the remaining 55%. So, the conclusion is that strength plays an important role in sprint speed but other factors contribute as well.

The investigators conclude that leg strength is closely associated with both sprint and jump performance in well trained players. Stronger athletes tend to jump higher and spring faster. They also mention earlier studies that show positive effects of strength training on performance. That is, increasing squat strength in young soccer players improves their performances in both sprinting and jumping. Given all of this, the team stresses the importance of developing lower body strength in order to improve sprint and vertical jump performance. They suggest that strength training using squat exercises should be considered as part of a periodized training program, one that emphasizes and ensures technical proficiency in all performances. By improving strength, sprint sped and jumping ability should be improved as well.

Reference

Comfort P, Stewart A, Bloom L, Clarkson B (2013) Relationships between strength, sprint and jump performance in well trained youth soccer players. Journal of Strength and Conditioning Research, DOI: 10.1519/JSC.0b.13e318291b8c7