Sometimes it could be as simple as finding better shoes. Another option you could suggest to your client is to start incorporating surfaces such as sand for his training as well. Sand can help with the strengthening of all those stabilizing muscles and ligaments supporting the feet, ankles and calf muscles. He could start running barefooted or get some Vibram Five Fingers shoes, so he could take advantage of the sand surface. It’s a great way to increase the stamina, strength and flexibility of his lower body that could also help with the cramping (either prolonging or eliminating the clamping all together).
Also lower body foam rolling should be part of his recovering (if he is not doing it already). It’s difficult to give you any other suggestions without knowing and evaluating your client. Maybe someone else can give you a better solution/suggestion to your question. I hope this helps.