This is no longer on the BMAT.
In the picture, you can see that the person is straightening their leg. To straighten your leg, you need to contract your quadriceps (upper front thigh = R) and relax your hamstrings (upper back thigh = P).
The glutes (Q) must also contract to provide maximum force to get a good start to the race.
You can see that at the ankle, the person is pointing their toes out more in position 2. The gastrocnemius (T) must contract and the anterior tibialis (S) must relax.
Muscles that contract = R, Q, T
Muscles that relax = P, S