“Should I stretch before or after a lift?” - Sam D., Carmel, CA
Research shows that dynamic stretching, where you actively take a joint through its full range of motion (e.g., stretching while moving—think of a leg swing), is A-OK for improving flexibility before a lifting session. But static stretching—where you get into the stretched position and hold it—may not be.
A study in the Journal of Strength & Conditioning Research found that subjects who static-stretched before lifting still made strength gains, but not as dramatically as those who did no stretching at all. Since stretching relaxes and elongates muscles, it seems to temporarily reduce their ability to produce force; so to maximize your lifting, you should do it after training or at another time entirely.
However, in my opinion, there’s one notable exception: If your muscles are too tight to let you perform certain exercises properly, you’ll need to stretch beforehand—both dynamically and statically—to improve your mobility. Yes, you may compromise strength, but you’ll increase safety, which is far more important.