In basketball, a running single leg jump (RSJ) is frequently used in various competitive activities such as rebounding, blocked shots and lay-up shots at a higher position. Hence, the ability of the RSJ is a determinant for achieving high competitive performances in this sport. It is known that basketball players have a dominant takeoff leg (DL), which is preferably used to perform the RSJ (Schiltz et al., 2009). For basketball players, however, it is critical to perform the RSJ at the same level regardless of the DL and non-dominant legs (NDL), because they must offend and defend from various directions and situations relative to the goal. In addition, Brumitt et al. (2013) and Schiltz et al. (2009) argued that limb asymmetry in performance over 10% increases the occurrence of sportrelated injuries. For basketball players, lower extremities are the most frequently injured body area (Borowski et al., 2008; Decker et al., 2003; Ellapen et al., 2012; Messina et al., 1999; Nelson et al., 2007) because they frequently use each leg to jump, pivot or change directions, and are likely to overuse the takeoff leg as it enables them to jump higher. Thus, to reduce any asymmetry in the performance of the RSJ is essential, not only to achieve high performance, but also to prevent injury to the lower limbs.
Many studies have already investigated asymmetry between limbs in performance during different single leg jumps, which are started from a standing position (Hewit et al., 2012; Maulder and Cronin, 2005; Meylan ets al., 2010; Miyaguchi and Demura, 2010; de Ruiter et al., 2010; Schiltz et al., 2009; de Swearingen et al., 2011). Some studies (Meylan ets al., 2010; Miyaguchi and Demura, 2010; Swearingen et al., 2011) showed that the performance of a single leg vertical jump from standing was significantly higher in the DL than in the NDL. Meylan et al. (2010) also observed a similar phenomenon in the horizontal and lateral counter movement jumps. In addition, Schiltz et al. (2009) showed that professional basketball players jumped significantly higher with the DL than the NDL (12%) in drop jump. These studies focused on jumps from a standing position, and to our knowledge, no studies have tried to examine the asymmetry of performance in the RSJ.
Many studies have already investigated the kinematics during RSJ through comparing high jumping players with low or correlating the jump height with jump variables in basketball and jump events of track and field (Greig and Yeadon, 2000; Ritzdorf, 2009; Stefanyshyn and Nigg, 1998). Stefanyshyn and Nigg (1998) have reported that to exert a greater force by ankle angle compared with knee and hip joints is important to jump high in RSJ. Moreover, it has been shown that high jumpers kept knee joint to more extended position to jump high at takeoff phase (Greig and Yeadon, 2000). Considering these findings, it may be assumed that the asymmetry of performance in RSJ is attributable to that of the kinematics of takeoff leg.
The present study aimed to clarify the differences between the DL and NDL in the behavior of the lower extremity during RSJ in collegiate basketball players. To this end, we compared the kinematics of the lower limbs in the takeoff leg during the RSJ between the DL and NDL and examined how the asymmetry of the jump height can be associated to that in the kinematics of the takeoff legs. We hypothesized that the asymmetries of jump height in the RSJ can be associated to that in the kinematics of the takeoff leg, notably in the ankle joint.
Twenty-seven healthy male collegiate basketball players voluntarily participated in this study. Their means and standard deviations (SDs) of age, body height, and body mass were 21.1 [+ or -] 2.4 yr, 1.76 [+ or -] 0.05 m, and 71.4 [+ or -] 7.7 kg, respectively. Fifteen of the subjects were guard players, nine forward players and three center forward players except pure center playing near the rim. The subjects had experienced organized competitive basketball training for at least eight years and participated in domestic or intercollege competitive meetings. They were in good physical condition and without any history of injury to the lower limbs within the last year. On the basis of questionnaires, the DL was defined as the one used preferably for jumping with a single leg, as described in prior studies (Schiltz et al., 2009). In this study, all subjects could jump higher with the DL than the NDL during RSJ. The DL for 18 of the subjects was the left; therefor, for the remaining subjects was the right. This study was approved by the Ethics Committee of the National Institute of Fitness and Sports in Kanoya and was consistent with institutional ethical requirements for human experimentation in accordance with the Declaration of Helsinki. Prior to the measurement session, all subjects were fully informed about the procedures and possible risks involved as well as the purpose of the study. Written informed consent was obtained from all subjects.
The participants were asked to perform a maximal RSJ that was similar to a condition in which basketball players rebound a ball close to the rim. The subjects approached for 6 m in which the distance was similar 3-point line when outside players started playing in the area at their own speed and jumped maximally in order to touch by hand a target set to the end of a ceiling 3.05 m in height. The experimental test was carried out without the ball to eliminate various constraint...