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RESEARCH PRODUCT

Training the Vertical Jump to Head the Ball in Soccer

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R esearchers involved in the training methodology to improve jump ability proposed a variety of techniques and exercise modalities (22,15,4). Nevertheless, the question on what percentage of training should be dedicated to strength and what to power seems unresolved. First of all, to better understand the matter, we have to stress the difference between strength and power. Generally speaking, in athletics, the rate of force development (RFD) is much more important than strength alone; the average RFD (mRFD) can be estimated as the ratio Fmax/Tmax, where Tmax is the time to reach the peak force, whereas Fmax is the maximum force. This ratio is also named explosive strength, commonly computed, for applicative purposes per 1 kilogram of body weight (26). Explosive strength is a fundamental conditional capacity for a soccer player, and more specifically, vertical jump height is primal to successfully impact the ball. Explosive strength is fundamental for a soccer player to obtain the jump height necessary to head the ball or, in other words, the maximal ability of a muscle to exert force or torque at a specific velocity (16). This kind of neuromuscular quality is often assessed by the 1 repetition maximum (RM) test, but 1RM strength maybe useful only for a few athletic events like weightlifting because during the 1RM test, low acceleration values are usually obtained. Referring to concentric movements, the difference among strength and power generation is due to the velocity of the muscle contraction. In fact, power is given by the product of force and velocity: the higher the force, the lower the velocity of concentric muscle action (14). This is explained in Figure 1.