Changes in contact and flight times with increased speed during overground and treadmill race walking

Introduction Race walking is an Olympic event dictated by a rule that states that no visible loss of contact with the ground should occur and that the leg must be straightened from first contact with the ground until the ‘vertical upright position’ (IAAF Rule 230.2). The measurement of contact and flight times during race walking is therefore of great interest to coaches and athletes. The aim of the study was to compare the effects of changes in speed on temporal variables in elite race walking during treadmill and overground race walking. Methods Eleven male race walkers (stature: 1.77 m (± 0.06), mass: 64.4 kg (± 4.7)) and eight female race walkers (stature: 1.67 m (± 0.09), mass: 56.1 kg (± 10.3)) participated. Fifteen of the athletes had competed at the 2016 Olympic Games or 2017 World Championships. For the overground condition, the men race walked multiple times down a 45-m indoor track at 11, 12, 13, 14 and 15 km/h in a randomised order, whereas the women’s trials were at 10, 11, 12, 13 and 14 km/h. Contact and flight times were measured for each trial using five connected 1 m strips of an OptoJump Next system (1000 Hz). For the treadmill condition (conducted on a separate day), each athlete race walked on a treadmill at five speeds for 3 min each. The speeds chosen were the same as during the overground condition and were conducted in a randomised order after a 10-min warm-up and familiarisation period. Results from the OptoJump Next system were extracted using specific settings based on the number of LEDs found optimal during a reliability study; for the overground tests, this setting was 2_2, whereas for the treadmill tests it was 0_0. Results For the overground condition, the values changed as follows (contact time / flight time): men – 11 km/h: 0.327 s / 0.015 s; 12 km/h: 0.304 s / 0.025 s; 13 km/h: 0.281 s / 0.035 s; 14 km/h: 0.267 s / 0.040 s; 15 km/h: 0.251 s / 0.044 s. For women, the values changed as follows – 10 km/h: 0.331 s / 0.012 s; 11 km/h: 0.307 s / 0.022 s; 12 km/h: 0.286 s / 0.033 s; 13 km/h: 0.269 s / 0.040 s; 14 km/h: 0.248 s / 0.049 s. For the treadmill condition, the values changed as follows: men – 11 km/h: 0.313 s / 0.021 s; 12 km/h: 0.296 s / 0.029 s; 13 km/h: 0.279 s / 0.038 s; 14 km/h: 0.261 s / 0.047 s; 15 km/h: 0.247 s / 0.053 s. For women, the values changed as follows – 10 km/h: 0.319 s / 0.023 s; 11 km/h: 0.293 s / 0.036 s; 12 km/h: 0.276 s / 0.045 s; 13 km/h: 0.258 s / 0.054 s; 14 km/h: 0.245 s / 0.059 s. Discussion Although it was unsurprising that contact time decreased with increased walking speed, and that there was a concurrent increase in flight time, what was interesting was that women had higher flight times when their speeds were matched with the men’s. Women therefore need to be more careful about displaying visible loss of contact. In addition, flight times tended to be higher during treadmill race walking at the same speed as overground (and contact times lower), suggesting that treadmill training could induce non-legal technique.