I can't add much to what's already been said here (I'm 67). I've been training and competing in Olympic lifting for almost 50 years and I can tell you that recovery from your workouts (and injuries!) definitely takes longer than it used to.
The previous posts that mentioned adequate nutritional intake, i.e., enough minerals, enough vitamins, all make worthwhile points. I'll add that as you age, the careless eating habits that you could get away with when you were younger can definitely harm you at your age, and what might have been a bearable slight vitamin or mineral deficiency when you were, say, 40, can cause majors problems when you're 75.
Here's an example:
The newsletters of both Drs. West and Rowan have recently had articles on iodine deficiency. It's very common here in the U.S., and one way you can test for it is to take some regular tincture of iodine from the drug store and paint a 2" square patch on your inner arm near your elbow, or, if you're very dark-skinned and have a hard time seeing the patch at that location, on the heel of your less dominant hand up into the web between your thumb and forefinger.
If the patch disappears in less than 24 hours, it's likely you're iodine deficient.
When I did that test twice, one week apart, the patch disappeared in less than six hours.
I'm using the product called Iodoral in my treatment. If you google "iodoral," you'll get several places where you can get the product. I get it from a gal who's using some of the profits to fight the Codex Alimentarius, which you should also find out about.
Do all the research you can on this topic and then ask your doctor about trying the "iodine sufficiency" (to use Dr. West's term) protocol.
One other thing: Don't worry about trying to compete with the young tigers.
There are so few of us who maintain the strength levels that we had years ago into our old age that (one exception I think of is the American Olympic lifter Norb Shemansky) it's virtually certain that you can't do it, and that's OK. The young guys (and gals, too) will get old and wweak soon enough.
Back to the iodine deficiency -- there are places on the Web where you can find posts from people who've undergone this iodine therapy, and have seen improvements in their sleep patterns, their energy during the day, weight loss, sex (oh, yeah!!), skin condition, hair condition, finger and toe nail condition - and I certainly can't say whether you even have it, but best to get all the information you can before you start talking to your doctor, because he or she may be conventionally minded and want to put you on a precription drug. I try to avoid those things whenever there's an effective, natural substance or food, or supplement, that will work as well as the drug with fewer or no side effects.
Good luck. And check out this site regularly and fequently. It is one of the most literate and clear sites that I know of anywhere on the Web.