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Light Weights vs. Heavy Weights—Which Should You Use?

You've always heard that when it comes to building muscle mass, heavy weights are preferred over lighter weights. But a new study published in the Journal of Applied Physiology has found that isn't always the case. In fact, you can build just as much muscle by lifting lighter weights. If you do it right...

The key is working the muscle to total failure or exhaustion, says Michele S. Olson, professor of exercise science at the Human Performance Laboratory of Auburn University Montgomery and the star of the workout DVD Perfect Legs, Glutes and Abs

"Failure, in this sense, is a success," Olson says. "If you work your muscles, on each set, until you cannot execute another repetition with appropriate form, the heaviness of the weight becomes less important." 

While the research is new, the concept of working to total failure — regardless of how much weight you're lifting — is not, she says. The American College of Sports Medicine has been recommending this strategy since the 80s and has been advising that people lift a weight that will cause exhaustion within 12 to 15 repetitions. 

While lifting lighter weights can be less intimidating, more convenient (you don't need a spotter) and a better option for those who are older, strength training with lighter weights does mean that it takes more reps and more time to get to that sweet spot of total exhaustion. So people who are in a hurry? Heavy is still probably best. 

Additionally, most women probably need to reconsider what they consider "light," Olson says. In the study, woman lifted at minimum 30 percent of their max. For the average 145-pound woman, a maximal squat is about 130 to 135 pounds. Therefore, lifting a "light" amount in this study would equate to doing about 25 to 30 reps holding 15- to 20-pound dumbbells.

"Most women consider a dumbbell of about 10 pounds to be heavy," she says. "So, very, very often, women are not lifting what would approximate the lightest weight level (30 percent of max) that was employed in this research study."

Again, the key to building muscle mass is going to exhaustion, no matter how heavy the weight you're lifting is.

"And that going to failure/muscle exhaustion means that you cannot execute another repetition with good form because your muscle is toast," Olson says. "Both are very important components to keep in mind whether using heavy, medium or light weights — man or woman." 

How heavy or light of weights do you lift? Do you truly go to muscle fatigue? Will you change anything about your strength-training workouts? Tell us about it in the comments below!


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