Effect of speed change on the kinematic parameters of women’s 20 km racewalking: A case study

This study aims at exploring the effect of speed change (i.e., 13.2 km/h moderate-speed and 15.12 km/h highspeed) on kinematic parameters of women's 20 km race walking. C.N, Tunisian elite women's champion (i.e., Arabic, African and U23 Mediterranean champion) qualified for the Rio 2016 and Tokyo 2020 Olympic Games (age 22.15 years; height 1.68 m; mass 50.2 kg; average training 140 km/week) who participated in this study. A 3D kinematic analysis of multi-speed race walking (i.e., over a distance of 20 m) was recorded using two mutually synchronized digital cameras (i.e., AEE PNJ Cam, 120 Hz). Body markers (i.e., Hanavan model) were digitized using SkillSpector® software. Delta percentage between moderate and high-speed parameters were calculated. The results showed that when changing speed (i.e., from moderate-speed to high-speed), stride length (i.e., 1.33 m and 1.45 m respectively) and stride frequency (i.e., 3.5 Hz and 4 Hz respectively) change as well as contact time (i.e., 0.23 s and 0.20 s respectively). However, center of mass vertical displacement (i.e., 0.064 m and 0.063 m respectively), knee angle in flexion (i.e., 84.09° and 85.01° respectively) and in extension (i.e., 180.02° and 180.01° respectively) remain almost constant, which shows that the athlete has an excellent technical stability. In conclusion, the athlete has retained the same technique, even during speed increase, there is no perceptible change in either vertical displacement or knee angle, but an increase in the frequency and length of the stride, thanks to the high technical requirements and to avoid disqualification risk due to the strict race rules.