I used Voyagers gym (treadmill) and some free weights during my cruise and had no problem. I had to still stay in shape for track/field season and just to stay in shape. I even used the sauna/steam room with no problem. I was 16 at the time (but in person I look alot older) and was never asked me age or anything. Usually I met my dad there who was already working out, but I saw a couple of kids my age there too so I wouldent worry.