 And it's important to help maintain strength and muscle contractions when you're using them over and over again. For instance, if you're working out at the gym, if you're playing sports, golf, tennis, anything like that, it keeps your muscles powered up in their high-energy state so they're strong and ready for action. Now, here's the key. This is so important for those of us, say, in our 50s, 60s, 70s.