Biomechanics Analysis of Sports Footware

In this exercise we are going to measure the contribution of studs to rugby boots in relation to their functions in optimising play.

Method – this part of the exercise will be done at home, in between week 2 and week 3 classes.

There are three boots available – each student will do his own analysis on ONE boot only, then pass it around to other students. It would be good to arrange a schedule between students around class times.

• A sheet of squared paper is supplied.

• Using the specimen boots supplied, draw the outline of the boot, and mark out on your outline where the studs are, as precisely as possible.

• Measure the size and depth of the heel and sole studs, and write down your results on the sheet of paper, it will be useful for further calculations. Note that we will ignore the blades on the sole (the two horizontal bars in between the sole studs).

Results (50% of overall coursework grade)

• Do your initial calculations on the back of the squared paper so I can see how you derived the results. Then report the results in the results sheet provided. Give results to two decimal places.

• Q1. Calculate the area of the plantar surface of the boot, by counting squares. Briefly explain on the squared paper sheet how you proceeded.

• Q2 and Q3. Calculate the stud surface areas (ignore the blades). Assume the sole studs are cylinders and the heel studs are rectangular solids.

• Q4. What percentage of the total boot plantar surface area does the total stud (heel and sole) represent?

• These boots belonged to a 100kg rugby full back. Calculate the pressure exerted by the studs of one boot with the subject standing on:

o Q5. A concrete floor

o Q6 and Q7. Soft turf (assume the studs penetrate the ground fully and they alone provide the interaction with the substrate). Express this value in Pascals.

Pressure is force per unit area: assume G = 10m.sec-2 and give your answers in N (Newtons) per square cm (cm-2).

Overleaf is the distribution of standing body weight on the foot. In our example, 50kg of body weight is transmitted down the tibia, through the talus and then posteriorly to the heel and anteriorly to the tarsals/metatarsals. Given the force distribution in the diagram below, calculate the following force transmissions in Newtons per cm-2 (you can choose if your athlete is standing on a soft or concrete floor):

• Q8. Force transmission in Newtons per cm-2 through the lateral sole studs.

• Q9. Force transmission in Newtons per cm-2 through the medial sole studs.

• Q10. Force transmission in Newtons per cm-2 through the lateral heel studs.

• Q11. Force transmission in Newtons per cm-2 through the medial heel studs.

• Q12. How well does this match the pressure distribution diagram?

OK, we know that the extra area provided by the studs is not the whole reason for having them. So why have studs? The answer, of course, is that they penetrate the ground and give anchorage: playing with non-stuIDed boots would be much more difficult, as the player would have to rely solely on friction between wet grass and the boot. Let’s assume that the heel strikes the ground at 2.5G, so the force delivered to the studs is 2.5 times that when standing; the force of impact drives the studs into the ground and they provide essential force transmission into the substrate.

Discussion (50% of overall coursework grade)

Answer the following questions. Just use bullet points/notes (maximum 200 words per answer). Cite any references used.

• How do studs in sports boots improve performance?

• Why not have more studs?

• Howe could studs cause foot problems?

• Why do some boots have blades instead of studs?

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