Force Production in Each Leg During The Block Phase of The Sprint Start


At university in the UK, students have to do a final year project as part of their course. The title of this blog post was the title of my study, and so I thought I would share what I found with the members of this site.

Background- I predicted that peak rear foot force production was very important during the block phase – or at least more important than considered by the mainstream. During my literature review, I came across an interesting study by Van Coppenolle et al. (1990), in which three top-level sprinters (PBs of 10.02, 10.22, and 10.39) had their starts analysed. It was found that the quicker two sprinters produced significantly greater peak force on the rear block than the slower sprinter. This increased force production lead to an increase in horizontal start velocity. Interestingly, all three sprinters produced similar front block peak force values

.Methods- I collected data from 12 male athletes. Two athletes were sub-10.20 runners, and the mean 100m best time was 10.87 seconds. I managed to get a force plate under each block plate in order to measure force production.

Results- As you would expect, the athletes that produced the most force had a better horizontal start velocity. I found that 70% of my subjects produced a greater peak force in their rear foot compared to their front foot- with a general trend of the faster athletes producing a higher peak rear foot force relative to front foot peak force. I found a significant correlation between peak rear foot force production and horizontal impulse, which in turn had a significant correlation with horizontal block velocity. There was no significant correlation between front foot peak force and horizontal impulse.

Conclusions- The main finding of my study was that rear foot peak force has a greater effect on horizontal impulse than front foot peak force. However, it is worth pointing out that as the front foot is in contact with the block for longer, the front foot produces greater total force, and so is still important. Practically, it may be useful for athletes and coaches to know this information, and attempt to utilise the rear block more than they might currently.
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