What consumer is trying to point out to you Max is that you may be over training. It generally takes at least 48-72 hours(depending on the intensity of your workout) for your muscles to fully recover. And, you do most of recovery while sleeping/resting. With high intensity workouts, you also need to increase your protein intake to aide in recovery. Many supplement their diet with powdered whey protein to help.
Also, a good way to keep from over training when you workout in the gym frequently is to do a "push"/"pull" routine. Ex. push exercise one day(chest, shoulders, and triceps), pull exercises the next day (back, traps, biceps), and legs on the third day. That way, you are not re-working the same muscles each day.
Lastly, don't overlook ice therapy. Most serious athletes nowadays soak in an ice bath after a high intensity workout. I would suggest you ice your ailments with a bag of ice/frozen peas right when you finish training or kiting. Good luck Max and its very cool that you kite with your son.