Ah cool thanks for the responses. So lets use 80kg to account for friction and counter force of opponent.
Therefore:
0.5*80*2.5^2 = 250j (using a slightly faster 2.5m/s)
250/0.5 = 124W
125/0.75 = 166.67N (btw where'd you get 0.75from? Half 1.5m/s)
166.67 / 3 = 55.56N
Torque = 55.56 * 0.15 = 8.34Nm per leg

Sound about right?