Biomechanics of seated throwing : Kinematic contributions of upper limb

Background. Decisions made by seated athletes and their coaches regarding throwing frame design and technique are currently based using a combination of anecdotal evidence (e.g. comfort, trial and error (Frossard et al.2005). A better understanding of the interaction between the seated athlete and their throwing frame is needed (Keogh & Burkett 2016). This will enable evidenced based decisions regarding throwing technique and frame design by the coach and athlete, to influence performance. Throwing frame design is critical as it has the potential to influence the organism-led constraints (functional level) which would lead to changes in the co-ordination strategy, and hopefully, maximum performance (Keogh 2011). The purpose of this case study was to describe movement pattern variability occurring at key events during the throwing movement (i.e. power and release positions) for 4 throwing configurations.Methods. One Female elite level Class F34 athlete (Age 39 years, Height 1.69m, Mass 90.3kg) participated in this study. The participant conducted her usual warm-up prior to throwing, and used her own throwing frame. A 3kg shot put was thrown 6 times from 4 throwing configurations (Figure 1). Distance thrown was measured and recorded after each trial. A 21 camera Qualisys (250Hz) set-up was placed around the thrower, and three dimensional (3D) kinematic data was collected using (56) reflective markers placed on the participant joints including the put. Data was processed in Qualisys before being exported to Visual 3D where joint angular velocities (trunk, shoulder, elbow and wrist) were extracted. Trials were analysed from the power position (determined as the point just prior to the final forward movement into the release) to the point of release, for 4 throwing configurations (Figures 2). The mean of the six trials was used for analysis, joint angular velocities were time normalised and graphed (Figures 3 and 4). Shot put kinematics were extracted and graphed in the same way (Figure 5).Outcomes. The joint angular velocity graphs (Figures 3 and 4) show variations in the movement characteristics between the 4 throwing configurations. Peak trunk angular velocity is greater for the No Pole throwing configurations. Similarly, there appears to be more “trunk whip” enabling greater transfer of angular velocity from trunk to elbow, without a holding pole. Trunk whip is thought to positively influence trunk muscle stretch, producing greater force and promoting muscle contraction (Judge et al. 2011). It should be as large as possible when the athlete is just exiting the power position (Bartoniez & Borgstöm 1995, Young & Li 2005). This is further demonstrated when the velocity of the shot put is tracked (Figure 5).Practical Applications. The data from this case study is suggesting that performance may be positively influenced by the athlete not utilising a holding pole. This is different to the findings of Burkett et al (2012) who found no differences between with or without holding pole in a non-disabled population. Lesser variations were shown between the front on and diagonal sitting positions.This may be useful to the athlete and coach when deciding on throwing frame design and technique