Wakeboarding Prisoner's Dilemma

     For Fall Break I went to Lake Anna to practice wakeboarding for the last time this year. When I went out Saturday morning, it was different than most wakeboard runs. Not because it was 48 degrees outside, but because my brother wasn't able to come. My brother and I both wakeboard a lot and whenever we practice we are always trying to one-up each other in the tricks we can perform. However, he snapped his ACL in half while wakeboarding a few weeks ago so he cannot practice until April. I was thinking about this as behind the boat and I realized I wasn't being as risky as usual because my brother was not there and because of a Prisoner's Dilemma.
     While practicing, you can wakeboard aggressively or more smoothly and relaxed. When I am with my brother, I want to make sure I look better than him, so I wakeboard aggressively. He attempts to be as good as me (though rarely does) so he also practices aggressively. However in practicing that way, falls often hurt more and injuries can sometimes happen (hence his ACL). So, the ideal situation would be if we both took it easily to reduce the risk of injury. However, the potential respect and admiration from our peers in the boat is so great, we are each incentivized to practice aggressively. As we do not usually wakeboard at the same time and wakeboarding aggressively is a dominant strategy, the result is that we both wakeboard aggressively which is an inefficient dominant strategy equilibrium. Mueller contends that in small groups this can be overcome through social pressure or deals, but to reason with my brother has high transaction costs and would likely not provide high marginal benefits. It is possible that the impact of the water knocked some sense into him, so hopefully after he is recovered next Spring he would be more willing to come to an agreement about how we will practice.