I tried it for a while. Didn't notice anything when it comes to muscle repair but it sure as hell improves sleep. I was using a product called Z-Mass PM. No matter how long I slept, I would always wake up refreshed and not tired at all. Then when I stopped using it it felt like I was in a train wreck waking up (which is how it always is for me, except when I was using ZMA). Not quite sure why I stopped taking it. If sleep is important to you and/or you have trouble sleeping, then definately try some zma. But as for muscle repair/growth, I don't believe it to be worth it... even though it's fairly inexpensive. But those are just my experiences, everyone is different, could work better or worse for you.