"If its not dehydration or lack of vitamins, it is probably just tight muscles or a muscle development issue.
I would try stretching regularly especially after a workout and before bed. If this doesn't improve the issue then you could have…"
"I would try a KOA on a weekend where you know the weather will be ideal. There is a store on-site, with good bathrooms and showers. Basically a place to set up a tent and start a fire. If he doesn't like that then it may be a hopeless…"