Recently Hasegawa et al (2007) investigated foot strike patterns and ground contact times during a half marathon. They found foot strike patterns were related to running speed with forefoot and midfoot strikers exhibiting shorter ground contact times and faster running speeds. The purpose of this study was to conduct a similar analysis in female 800m runners. Five seeded sub-elite races were filmed on one evening at a British Milers Club meeting. The runners (N = 34) were filmed by a 100-Hz video camera at a height of 15 cm placed 15 m from the start / finish line. All runners completed their race and were captured on both laps of the race. Average race time showed a range of 15.85 s with a mean 132.84 +/- 4.43 and CV of 3.3%. Mean contact time for lap 1 and lap 2 were 163 +/- 14 ms and 179 +/- 16 ms. On lap 1 27%, 44% and 29% of runners made initial ground contact with the forefoot, midfoot and heel respectively. These values were essentially unchanged at 27%, 41% and 32 % on lap 2. An ANOVA comparing ground contact time across the different races for both laps revealed significant main effects for lap (F1,29 = 35.445; P < 0.000) and race (F4,29 = 6.112; P = 0.001). Runners displaying the same foot strike pattern on both laps (N = 27) were entered in to a 2x3 ANOVA comparing ground contact time by lap and foot strike position. This showed significant main effects for lap (F1,24 = 28.707; P < 0.000) and foot strike position (F2,24 = 4.299; P < 0.025). Post-hoc analysis revealed significant differences between heel and forefoot strikers. The shortest ground contact times were for the forefoot (167 ms) followed by midfoot (172 ms) and heel (181 ms). Both forefoot and midfoot strikers exhibited a significant increase (forefoot - t6 = 5.435, P = 0.002; midfoot - t10 = 4.038, P = 0.002) in ground contact time between laps. Heel strikers showed no significant increase in ground contact times across the two laps (heel - t8 = 1.692, P = 0.129). Linear regression revealed a significant relationship between average running speed and ground contact time for lap 1, lap 2 and average contact time. Only a moderate portion of variation in average running speed was explained (29.9 %, 25.6 % and 36.9% for lap 1, lap 2 and average contact time respectively). This study found that foot strike patterns were related to running speed. The relationship between ground contact time and running speed supports the notion of a spring-mass model of locomotion. Over the course of an 800m race ground contact time increased. This implies an element of fatigue, with runners presumably requiring longer to generate the same impulse. Alternatively, this may be a reflection of the pacing strategy during the races, with all races adopting a first lap that was quicker than average race speed.
© Copyright 2009 14th annual Congress of the European College of Sport Science, Oslo/Norway, June 24-27, 2009, Book of Abstracts. Veröffentlicht von The Norwegian School of Sport Sciences. Alle Rechte vorbehalten.