# Intra-Individual Variation in the Jump Smash for Elite Malaysian Male Badminton Players
## 4 Discussion  
The intra-individual variation in shuttlecock smash speed across the 25 trials for each participant varied from 3.3 to 13.4 m\(\cdot\)s\({}^{-1}\), with significant differences between the FAST and SLOW groups for both post-impact shuttlecock speed and racket head speed. A maximum difference of 3.3 m\(\cdot\)s\({}^{-1}\) (3%) across 25 trials could be considered a small difference and perhaps what might be expected for elite players, but 13.4 m\(\cdot\)s\({}^{-1}\) (13%) is over three times greater than this value and for an elite player is perhaps surprising. This drop of 13% would bring an 'elite' player in line with'regional'-level players based on data from [3], where elite players achieved similar shuttlecock speeds of 94.6 m\(\cdot\)s\({}^{-1}\) whilst regional players achieved 84.6 m\(\cdot\)s\({}^{-1}\). A comparison of technique and racket/shuttlecock variables revealed several important differences between the FAST and SLOW conditions. Unsurprisingly, significant differences existed between the FAST and SLOW conditions for post-impact shuttlecock speed and racket head speed, respectively, given the high correlation between the two variables (\(r\) = 0.90; [3]). Overall the participants performed smashes with greater longitudinal impact locations (11 mm closer to the racket tip) in the FAST group compared to the SLOW group. It is not obvious why this difference in impact location occurred across a group of elite players, but it could indicate that coordinating the timing of the racket shuttle impact was challenging even for elite players. Having an impact location closer to the tip of the racket does result in a faster racket speed at the point of impact on the racket, and therefore, it makes sense that the fastest shuttlecock speeds came from impacts slightly closer to the tip of the racket. There becomes a point at which an increase in longitudinal impact location would cause a reduction in shuttlecock speed due to the impact efficiency between the stringbed and shuttlecock. The mean longitudinal and mediolateral impact locations during the FAST condition were similar to the 'optimal' impact location reported by another study [12], namely 8.5 vs. 11.6 mm and \(-\)15.3 vs. \(-\)5.7 mm, respectively. The 'impact quality' may also be related to the significant difference in swing duration, where players performed, on average, 3.6 ms shorter swing durations during the FAST condition. The small amount of extra time taken during the SLOW condition swings perhaps allowed the shuttlecock more time to drop and thus produce impact locations lower on the racket head and further away from the optimal position [12]. The technique of the participants did not vary substantially between the FAST and SLOW conditions, with only one upper-body joint angle differing between the FAST and SLOW conditions, namely the shoulder elevation angle between 75 and 95% of the swing phase. The players held their arm in a less elevated position during the FAST trials compared to the SLOW trials, and this is supported by [4], where the arm is placed in a more favourable position to generate greater angular velocities of shoulder internal rotation. A lower shoulder elevation angle reduces the distance between the racket and the body, effectively shortening the moment arm of the racket-hand system. This potentially reduces the rotational inertia of the arm-racket complex, allowing for faster angular acceleration