If an athlete enters with his or her thumb, the whole hand can enter through a smaller hole, decreasing drag. However, many athletes achieve a thumbs-first entry through shoulder internal rotation. This orientation can stress the anterior structures of the shoulder and increase the risk for shoulder impingement. Luckily, the thumb first entry can be achieved with no movement at the shoulder. Instead, instruct your athletes to use forearm pronation (rotating the forearm inwards) instead of shoulder internal rotation to get their thumbs to enter first, decreasing the amount of drag on the entry.
Solution: Either instruct your swimmers to enter finger tips first or thumb first with only forearm pronation, a difficult but beneficial difference. Consider performing finger tip drag drills or hesitation drills just prior to entry to perfect the entry.