My Husband Had Been Helping The Master Gardeners Do Some

My husband had been helping the master gardeners do some fruit tree pruning. When he returned home he seemed fine, but after bending over to wipe some moisture from the garage floor and then came inside and bent over to change his shoes, he got a cramp across his back and through his chest which made it difficult to take a deep breath for about the last 10 minutes. It is now subsiding, but I also gave him two ibuprofen tablets. What could cause this?