The relationships between pelvic range of motion, step width and performance during an athletic sprint start

Figures & data

Figure 1. The pelvic and thigh coordinate systems. The pelvic coordinate system was used for calculating the pelvis segment angles relative to the laboratory coordinate system. The thigh coordinate system was used to calculate the orientation of the rear thigh with respect to the pelvis.

Figure 2. Pelvic segment angles from start to 1^st stance toe-off (normalised to 100 points) in the sagittal (a), frontal (b) and transverse (c) and planes for all participants. The black line represents the group mean. The vertical lines represent (from left to right) the key events of rear foot-off, block exit and toe-on. The position of the vertical lines is approximately drawn for the group of athletes; 1^st, 2^nd, 3^rd, 4^th and 5^th refer to the top five athletes ranked according to their P_NAHB (Table 1). Ensemble group average rear leg hip angles with respect to the pelvis segment, Figure 2 (d). Positive hip angles represent hip flexion, abduction and internal rotation.

Figure 4. Relationships between pelvic list (a), rotation (b) and tilt (c) RoM and normalised 1^st step width. A high positive correlation was found for the relationship between pelvic list RoM and 1^st step width (graph a); 1^st, 2^nd, 3^rd, 4^th and 5^th refer to the top five athletes ranked according to their P_NAHB.

Figure 5. Relationships between pelvic list (a), rotation (b) and tilt (c) RoM and block phase performance; 1^st, 2^nd, 3^rd, 4^th and 5^th refer to the top five athletes ranked according to their P_NAHB.

Figure 6. Relationships between normalised 1^st step width and: block performance (a), and 1^st stance performance (b). No linear correlations were found between these variables; 1^st, 2^nd, 3^rd, 4^th and 5^th refer to the top five athletes ranked according to their P_NAHB. NB as opposed to Figure 6(a), Figure 6(b) shows external power on the y-axis because during the 1^st stance, step width was defined as the independent variable.

Figure 3. Typical example of an athlete in the position of maximum pelvic list. Notice how the rear side pelvis is more upwards than the front side (a), and how medial orientation of the thigh accompanies pelvic orientation (b).

Table 1. A comparison of each participant’s normalised block power (P_NAHB), pelvic RoM, normalised 1^st step width and normalised 1^st stance power (P_NAH). Their respective group ranking for P_NAHB is also given.

	Block Phase		RoM (°) Block and Flight Phase			Corresponding 1st Stance Phase
	PNAHB	Ranking	Tilt	List	Rotation	Step width (norm)	PNAH
Sprinter
a	0.62	1	41	16	19	0.31	0.94
b	0.54	2	46	9	8	0.28	0.76
c*	0.51	3	41	15	22	0.35	0.85
d	0.50	4	29	20	13	0.38	0.78
e	0.48	5	42	15	26	0.26	0.65
f	0.46	6	30	7	17	0.19	0.83
g	0.45	7	23	16	14	0.37	0.79
h	0.43	8	23	18	14	0.33	0.91
i*	0.42	9	41	20	15	0.37	0.87
j	0.42	10	21	15	14	0.35	0.65
k	0.41	11	45	13	8	0.21	0.57
Mean	0.48		35	15	15	0.31	0.78
SD	0.06		10	4	5	0.07	0.12

* denotes the female athletes.