Nymark, B. S., Ronnestad, B., & Raastad, T. (2009). Pre-season correlations between sprint, 1 RM and running economy in professional soccer players. A paper presented at the 14th Annual Congress of the European College of Sport Science, Oslo, Norway, June 24-27.

This study investigated the relationship between strength in leg extensors, measured as one repetition maximum (1 RM) in squat, and sprint abilities as well as running economy in Norwegian professional soccer players (N = 15). Ss were tested for 1 RM in half-squat, sprinting performance (0-40 m), and running economy (measured while running on 5.5% incline at 10 km/h).

Relative strength in half-squat (1 RM/body weight) was correlated with 10 m acceleration (r = 0.70) and total time on the 40 m sprint (r = 0.75), but not correlated with running economy (r = 0.16). The failure of strength measures to be associated with running economy might indicate that maximal strength is unimportant for that running phenomenon. It may be that the rate of force development and muscle-tendon stiffness are more important for running economy than maximum strength. A tight musculo-tendinous system, and consequently a higher degree of stiffness, may be advantageous for running economy. Strength training has been reported to increase muscle-tendon stiffness.

Implication. In soccer players, leg strength is related to sprinting but not running economy. The relationship accounts for about half the variance associated between the entities. Because this study is correlational, it would be erroneous to conclude that increasing an individual's relative strength in the half-squat will increase sprinting performance. It is possible that other factors are more important than a simple measure of strength.

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