[BoomerSooner]

My money is on salt.

The activation time of non-narcotic, oral, pain medications (that is medication taken by mouth, not medication for oral pain) isn't going to be quick enough to alleviate pain that is significant enough to degrade performance.

So if we agree on these premises: 1. You don't give pain medication if the pain isn't resulting in degraded performance, 2. You don't give pain medication if isn't going to work quickly enough, and 3. You aren't going to give medication (a narcotic) that will degrade performance, we can probably rule out pain medication.

There are plenty of other possibilities, but in all likelihood, the training staff was working to prevent cramping by giving the player salt.