Professional soccer players with functional asymmetries possess a higher risk of sustaining hamstring strains. Previous injury seems not to constitute a risk factor. The systematic isokinetic evaluation of the lower extremities during the preseason period can provide therapists and trainers with valuable data regarding the predictive elements of non-contact hamstring strains in professional soccer players.

Eighteen elite Greek soccer players (age, 27.8 +/- 3.4 years; height, 176.6 +/- 5.2 cm; weight, 75.5 +/- 5.2 kg) were tested on the Cybex(R) II apparatus in order to determine 1) the maximal muscle power for the lower extremity dominant side at angular velocities of 30 degrees /sec, 90 degrees /sec, and 180 degrees /sec; 2) the total muscular output and the relative power at 30 degrees /sec; 3) the relationship between the muscle power of the agonist and antagonist musculature. The absolute maximal muscle power (Nm) at 30 degrees /sec for the different joint movements was as follows: Hip Ext = 269 +/- 39; Hip Flex = 179 +/- 29; Hip Add = 160 +/- 17; Hip Abd = 119 +/- 24; Knee Ext = 247 +/- 29; Knee Flex = 146 +/- 12; PI. Flex = 120 +/- 22; and Do. Flex = 32 +/- 6. The muscle agonist-antagonist percent relationship at 30 degrees /sec was found to be: (hip flex)/(hip ext) = 66%(hip abd)/(hip add) = 74%(knee flex)/(knee ext) = 60%(dor. fle)/(pl. fle) = 28%These findings have significant implications for preseason conditioning programs as well as for minimizing the rate of muscle injuries by restoring the correct relationship between agonist-antagonist musculature.J Orthop Sports Phys Ther 1985;6(5):293-295.

Soccer is one of the most popular, widely played sports in our societies with millions of participants all over the ~o r l d . '~,~~ Furthermore, soccer is a dynamic game featuring fastpaced activities and covering substantial distances over the course of the game. It is a physically demanding game which requires a high degree of technical skill, stamina, strength, and speed. In spite of this it is surprising that there are few scientific studies concerning the physiological profiles of soccer players. The powerful kick of a soccer ball should be considered an important factor affecting athletic ~erformance and, in addition to skillful exemetric contraction^,^^^^ as well as training at slow and fast isokinetic velo~ities;'~'~ while others have studied the effect of torque-velocity relationships and muscle fiber composition (fast and slow twitch) in elite athletes5 and strength training motoneuron excitability in human leg mus~ulature.~~'~ The aim of this study was to determine if the initial soccer ball velocity during a powerful soccer kick is related to isokinetic muscle strength of the lower extremity measured at various angular velocities: 30, 90, and 1 80°/sec. MATERIALS AND METHODScution, is the result of strength and speed.23 The Eleven Greek soccer players of the national Of strength and speed for improving team (four defenders, four midfielders, and three athletic performance is wellInforwards) were studied after their written consent vestigators have compared various strength trainhad been obtained. All athletes were tested on ing methods; concentric and eccentric versus isothe Cybex IIm isokinetic apparatus (Cybex 11, Division of Lumex, Ronkokoma, NY) at angular ve-