Medicine Cabinet: Lighten up and flex muscles

The next time we hear grunting in the weight room as some sweaty Jack or Jill bench-presses 160 pounds, we might break gym etiquette and ask, "What, exactly, are you doing?" Because that is just too much for most people to bear. The latest words: Lighten up.

New research shows you'll get as good or better results repeatedly lifting a light weight until you can't do any more as you will straining to do eight reps with a weight you can barely budge. So unless you're planning to pose for Flex, go for what trainers call "low-load, high-volume resistance exercise." Even though this is only one study, it's important.

How light is "low load"? Pretty light. About 30 percent of the heaviest weight you can lift. So, if 10-pound dumbbells are your max, drop to three-pounders. Alternatively, light means a weight that lets you do at least 24 reps before your muscles yell uncle. Researchers figured this out by somehow persuading a group of very nice men to let them remove tissue samples from their muscles after working out.

Turns out, the light lifters had gained as many or more muscle proteins as the heavy lifters - muscle proteins, not grunting, being how you measure the effects of resistance work. Conclusion, said the researchers: It's not how heavy the weight is, it's how tired you make your muscles. That's especially good news for people who risk injury using heavy weights - newbies, older exercisers, folks doing rehab.