The effect of body position and mass centre velocity at toe off on the start performance of elite swimmers and how this differs between gender

Figures & data

Table 1. Summary of male and females results and the difference between genders.

variable	Male	Female	Difference in mean	ρ	Effect size
Time to 5 m (s)	1.27 ± 0.05	1.44 ± 0.07	−0.17	<0.0005*^†	2.79
Time to 10 m (s)	3.51 ± 0.24	3.96 ± 0.21	−0.45	< 0.0005*	2.00
Time to 15 m (s)	6.41 ± 0.67	6.96 ± 0.55	−0.55	0.039*	0.90
Flight time (s)	0.34 ± 0.05	0.30 ± 0.06	0.04	0.050	0.72
Entry distance (m)	3.17 ± 0.22	2.81 ± 0.22	0.36	0.001*	1.64
Arm angle^a (°)	−86.3 ± 105.2	−60.8 ± 63.4	−25.5	0.143^†	0.29
Trunk angle^a(°)	−2.7 ± 9.3	−4.5 ± 8.5	1.8	0.631	0.20
Back leg angle^a (°)	10.8 ± 10.3	10.0 ± 5.5	0.8	0.819	0.10
Front leg angle^a (°)	−26.8 ± 4.8	−24.5 ± 5.2	−2.3	0.287	0.46
Mass centre y position^a (m)	1.03 ± 0.08	1.03 ± 0.06	0.00	0.849	0.00
Mass centre z position^a (m)	1.28 ± 0.06	1.17 ± 0.10	0.11	0.006*	1.33
Horizontal velocity^a (m/s)	4.58 ± 0.15	4.19 ± 0.18	0.39	< 0.0005*	2.35
Vertical velocity^a (m/s)	−0.61 ± 0.37	−0.91 ± 0.43	−0.30	0.086	0.75
Resultant velocity^a (m/s)	4.63 ± 0.15	4.31 ± 0.20	0.32	0.005*	1.81

*Significant at 0.05 level, ^† Mann Whitney-U test due to non-normality of data

^aat toe off.

Table 2. Correlation analysis of variables to the performance outcome, time to 5 m.

determining factor	Males		Females
	r/rho^†	ρ	r/rho^†	ρ
Entry distance	−0.702*	0.024	−0.552*^†	0.041
Flight time	−0.535	0.111	−0.260^†	0.370
Horizontal velocity^a	−0.754*	0.012	−0.663*^†	0.010
Vertical velocity^a	−0.510	0.132	−0.454^†	0.103
Resultant velocity^a	−0.652*	0.041	−0.347^†	0.224
Trunk angle^a	−0.694*	0.026	−0.420^†	0.134
Arm angle^a	0.571^†	0.084	0.051^†	0.862
Back leg angle^a	0.207	0.565	−0.378^†	0.182
Front leg angle^a	−0.099	0.785	0.078^†	0.791
Mass centre z position^a	−0.530	0.115	−0.227^†	0.435
Mass centre y position^a	0.174	0.631	−0.076^†	0.797

*Significant at 0.05 level, ^† Spearman’s rank test due to non-normality of data.

^aat toe off.

Figure 1. Typical arm positions at toe off: (a) arms stretched out in front (b) arms pointing down towards the water (c) arms back by the hips. x denotes mass centre position, • denotes head position.