Lifting heavy weights vs. light weights: Why one isn't better than the other

Choosing a weight to work out with isn't black or white -- here's what you should know.

Mercey Livingston CNET Contributor
Mercey Livingston is a health and wellness writer and certified Integrative Nutrition Health Coach. She's written about fitness and wellness for Well+Good, Women's Health, Business Insider, and Prevention.com among others. When not writing, she enjoys reading and trying out workout classes all over New York City.
Mercey Livingston
4 min read

Choosing a weight to workout with isn't always black or white.

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When it comes to working out, there's a lot of information out there about if you should lift heavy weights or not -- and it can get pretty confusing, fast. Some people opt for heavy weights when they want to achieve more visible muscles or "bulk" up, and some people are afraid to lift heavy weights for that exact reason. 

Unfortunately, many women still believe the myth that lifting heavy weights will give them bulky muscles, so they choose light or no weights and go to classes that promise "long, lean muscles" instead. 

But is any of this information even true? (Spoiler alert: not really). Choosing the right weight for you to lift is all about how you're working out, not the number on the dumbbells.

Read more: Don't skip these warmup exercises before your next workout

It all comes down to reps

People lift weights with the goal of making their muscles stronger (and, for some, to get those bulky biceps or lean-looking arms). For those looking to develop large muscles, they will likely opt for a heavier weight, while people who want to get lean will stick to something smaller.

The truth is, there's no correct strategy -- both are valid choices. Lifting heavy dumbbells, kettlebells and barbells will certainly make you stronger. But lighter weights can help you get stronger too -- it just may take you a bit longer. 

It all comes down to one important factor: muscle fatigue. This means that the goal of your workouts should be to work your muscles to the point of fatigue (i.e., when you can no longer do another rep) no matter how much weight you are using. So whether you are doing five dumbbell curls with a 20-pound weight, or 20 reps with a 5-pound weight, as long as you are getting to the point of muscle fatigue, you'll get stronger.

Read more: How to recover from a tough workout 

And science backs this up. A 2010 study found that a group of men who lifted heavy weights to the point of "failure" or muscle fatigue gained the same amount of muscle and improved their strength as much as the other group that lifted lighter weights for more reps. This study in 2016 found those same results.

Some workouts that you might do that use light weights include a barre class, yoga sculpt, Pilates, or "sculpting" classes. Or a light-weight workout may look like doing bicep curls with a lighter weight (like say 8-10 pounds) until you can't lift any more with good form. On the other end of the spectrum is doing squats with an Olympic barbell, which will fatigue your muscles after only a few reps.

The benefits of lifting light weights


Using lighter weights can help you build muscle -- it just may take longer to get results.

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What are some reasons you may choose to lift light weights over heavy? If you're new to working out or starting a new fitness program, light weights may be a good choice. "Someone may choose to train with less resistance when they are learning the form on new exercises. Then once they get the form down and feel comfortable, they can increase the resistance," says fitness trainer Heather Marr. Other things you can consider are that light weights are a good option for reducing the risk of injury --  you're just less likely to hurt yourself using a 5-pound weight over say, a 50-pound weight. 

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You can also bring light weights into other types of workouts to add more resistance and keep your heart rate up. For example, in some of my dance cardio classes we do dance routines while also holding a 2- or 3-pound weight, which adds resistance (my arms are always burning by the end) and makes the cardio workout harder. By the time I finish the song my arms feel like they can't hold the 3 pounds weights -- let alone anything heavier. 

That said, lifting heavy has its own set of benefits, and can definitely increase the challenge if that's what you're looking for in your workout routine.

What are the benefits of working out with heavier weights?

If you're looking to gain muscle, and increase your strength in the most efficient way possible, then lifting heavy weights is a good option for you. Gaining strength all comes down to fatiguing your muscles, and heavy weights will get you there faster. It just takes longer to get tired when you're curling a 5-pound weight versus a 25-pound dumbbell. "Heavy compound exercises offer the most bang for your buck. You are able to use the heaviest load possible and work more muscles in less time making them efficient and also advantageous for weight loss," Marr said. 

And if you're looking for more cardio in your routine, you can do that with heavy weights if you're strategic about your weight-training workouts. "You can even perform the exercises circuit style in a row and get the added benefit of conditioning work all in one," Marr said.

Read more: 7 best creatine supplements to build strength

How do you know when you should lift heavier?

When to lift heavy or light weights

It's a smart idea to start lifting heavier weights slowly and at your own pace.

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So say you've been working out for a while and the 5-pound weights don't really feel like they're doing anything. What should you do? Go heavier, of course; just make sure you move at your own pace.

According to Marr, you should work your way up slowly over time and always try to challenge yourself. "No matter what rep range you're lifting in for your working sets, the last rep to two should be a serious challenge and struggle. If it is not, then you know you need to increase the resistance," Marr said. 

All science and trainer advice aside -- the most important thing about your fitness and workout routine is that you're doing something consistently. And chances are that's the workout that is the most fun and engaging for you, no matter what kinds of weights you use. 

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The information contained in this article is for educational and informational purposes only and is not intended as health or medical advice. Always consult a physician or other qualified health provider regarding any questions you may have about a medical condition or health objectives.