"No matter how the maxim or principle is characterized, volenti non fit injuria .... constituted an absolute bar to recovery.... Yet it has, in recent years, been severely restricted in its application.
"In order for the doctrine of volenti to apply, there must be either an express or implied assumption of the risk of the activity which caused the damage... (B)oth parties to the activity must have agreed that they would participate in it regardless of the risk of injury and give up their right to sue should injury occur as a result of the agreed upon activity.