Galley Proof 22/12/2017; 8:52 File: ies–1-ies171159.tex; BOKCTP/xjm p. 1 Isokinetics and Exercise Science -1 (2017) 1–6 1 DOI 10.3233/IES-171159 IOS Press The effects of kicking leg preference on the bilateral leg strength asymmetries of amateur football players Mehmet Yıldız a,∗ and Mehmet Kale b a School of Physical Education and Sports, Afyon Kocatepe University, Afyon, Turkey b Department of Coaching Education, Faculty of Sports Science, Anadolu University, Eskisehir, Turkey Received 17 June 2017 Accepted 26 November 2017 Abstract. OBJECTIVE: To determine the effects of kicking leg preference on the bilateral leg strength asymmetries of college football players. METHODS: Thirty-four right-dominant (RD) and twenty-three left-dominant (LD) college football players volunteered to par- ticipate in the study. Squat and countermovement jump, standing long jump, and isokinetic knee strength (at 60, 180 and 300 ◦ /s) were tested with respect to inter-limb asymmetry index (ASI). RESULTS: There were significant differences in horizontal jump and H/Q ratio at 60 ◦ /s between DL and NDL in all football players. There were also significant differences in standing long jump, hamstring peak torque at 180 ◦ /s and H/Q ratio at 60 ◦ /s in the LD football players (p< 0.05). Moreover, the LD group had greater percentage of subjects with ASI > 15% for standing long jump, hamstring peak torque at 180 ◦ /s. Furthermore the percentage of subjects with H/Q Ratio < 0.60 for 60 ◦ /s was greater in the LD players’ DL. CONCLUSION: Bilateral leg strength asymmetries may be affected by a single leg predominantly in the mobilization workouts. Having higher inter-limb asymmetry index, LD players may be screened and trained to minimize leg strength asymmetries. Keywords: Bilateral, strength, asymmetry, dominant leg, leg preference 1. Introduction 1 In football, mobility workouts (force and direction 2 control in juggling and dribbling, movement timing to 3 trap an approaching ball, and power and accuracy to 4 kick a static or a moving ball) are considered as mas- 5 tering the tasks [1]. Most of the players predominantly 6 use their dominant leg performing these kinds of mo- 7 bilization skills (specially kicking to goal) during the 8 matches [2]. A few elite football players use each leg 9 with a similar frequency [2,3] and this lateral pref- 10 ∗ Corresponding author: Mehmet Yıldız, School of Physical Edu- cation and Sports, Afyon Kocatepe University, Afyon, Turkey. Tel.: +90 272 2181363; E-mail: mehmetyildiz@aku.edu.tr. erence in football players is based on the functional 11 advantage of the preferred leg over the non-preferred 12 leg [4]. However, often preferring the dominant leg 13 may cause bilateral asymmetrical strength develop- 14 ment [5–7] because the quadriceps muscles are primar- 15 ily used concentrically in kicks, jumps, and passes in 16 football [8]. On the other hand, the hamstrings are pri- 17 marily used eccentrically to stabilize, decelerate, and 18 control the knee, but they are also used concentrically 19 to turn, tackle, and sprint [8–10]. Therefore, bilateral 20 leg and agonist/antagonist (H/Q) asymmetry may be 21 developed in players who kick and pass the ball using 22 mostly the dominant leg [11,12]. 23 Several studies [13–17] investigated both lower 24 limb isokinetic strength and asymmetries in foot- 25 ISSN 0959-3020/17/$35.00 c  2017 – IOS Press and the authors. All rights reserved uncorrected proof version