According to a study, looks like lifting light weights can actually build up muscle size. I’m a certified personal trainer, and find it difficult to believe that lifting any ol’ light weight to complete muscle failure can truly build up size, even though that’s what the study (conducted at McMaster University) claims.
I can understand if the weight is just a little lighter, so that you’re reaching muscle failure at 12-15 reps. But here is what Stuart Phillips, associate professor of kinesiology at McMaster University, says: “Rather than grunting and straining to lift heavy weights, you can grab something much lighter but you have to lift it until you can’t lift it anymore.”
So how light a weight are we talking? Can you build up huge biceps by curling a 10-pound dumbbell until you can’t lift it anymore? If this were true, tons of women would be walking around with gigantic muscles, because often, women will lift light weights to failure. I’m talking 8-15 pound dumbbells, or a very light setting on a machine, or a 65-pound barbell for a bench press. Yet these women don’t exactly have huge pecs.
Phillips continues, “We’re convinced that growing muscle means stimulating your muscle to make new muscle proteins, a process in the body that over time accumulates into bigger muscles.”
Lifting any amount of weight, to failure, will change muscle structure and make muscles poke out just a little bit more, at a minimum. But this isn’t the same as building big slabs of meat that you see on men who lift heavy.
The study involved subjects lifting weights that were 90 percent of their best lift, which translated to repping 5-10 times before failure; and the other protocol was lifting weights that were 30 percent of what the subjects could exercise with, which converted to repping at least 24 times before fatigue kicked in.
The study was not conclusive as far as how much mass was actually gained, or how much bigger muscles got, not to mention the actual measurements of muscles such as biceps or quads. More studies are warranted for exploring this interesting premise.
In the meantime, what should you do? You can test this idea by switching your normally-heavy-weight workouts to 30 percent, and see if you begin losing mass. Measure your biceps at the beginning of the experiment, then after, say, two months of lifting 30 percent of what you normally use (to complete failure), measure the biceps again.
Are they smaller? Same size? Are you even willing to try this experiment, fearing that your prized bulging biceps will shrink and get weak? Will this study discourage women from repping out to failure with light weights, out of fear of building too much muscle size?
My message to women is this: Lifting light weights to muscle failure will not bulk you up. But if you’re convinced of this, ask a competitive female bodybuilder if she thinks this is true.