Two different Variants of Leg Repositioning at maximal Sprint Speed of high Performance Junior Sprinters

ABSTRACT

Two variants of leg repositioning are described biomechanically and examined for differences in step kinematics. Based on leg angle (two-point angle between radius of leg centre of gravity and a horizontal line) during air phase, 30 juniors were divided into two groups (n = 15), large leg angle (LLA, leg angle = 80 ± 4°) and small leg angle (SLA, leg angle = 69 ± 5°). Maximal flying 30-m sprints were recorded (200 fps) and group differences were analysed using a 5-point leg model. With comparable leg length, both groups differed in leg moment of inertia and leg angular velocity. Group SLA reduced knee angle under the body, the thigh of swing leg passed the support leg early, and reached a higher position during knee lift, followed by a higher vertical foot velocity during pre-support. At take-on, both groups achieved a comparable hip, knee and foot angle. Due to higher mass of thigh (66%) compared to lower leg, foot and spikes (34%), thigh movement is essential for repositioning. Despite SLA advantages, three of the six fastest sprinters (v > 10.4 m/s) were evenly divided into both groups. An influence on step length, step frequency, ground contact and flight time was not found.

KEYWORDS:

• Swing-pull technique
• kinematic step characteristics
• leg moment of inertia
• leg angular velocity
• leg angular momentum

Disclosure

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was supported by the German Federal Institute of Sport Science (BISp) under Grant number ZMVI4-071602/19. Finally, we thank the coaches and athletes of the German junior national team and the German Athletics Association (DLV) for their cooperation.