When to Train With Light Weights (and When to Use Heavy Weights)
The world of exercise is full of variety. You can lift light weights, heavy weights, or nothing at all. If you’re new to strength training, it doesn’t matter where you start. But that doesn’t mean all these options are equal. Light weights can promote muscle growth, but they don’t provide the same benefits as heavier weights.
Getting the most out of training with light and heavy weights requires different approaches. Heavy weights can do things that light weights can’t. I’ll go into more detail below, but for now, the most important thing I want you to understand is that it’s wrong to say that light weights are “as good as” heavy weights, or that “it doesn’t matter” which one you use.
Friends, this really matters. You may decide that lighter weights are better for you, or you may prefer the benefits of heavier weights. But you deserve to know the difference. Because there definitely is a difference. Even studies showing the benefits of lighter weights for muscle gain still show that heavier weights have their advantages.
For example, this meta-analysis, which pooled the results of 178 different studies, found that “heavier loads (>80% of one-repetition maximum) maximize strength gains, and all load types promote muscle hypertrophy [growth] equally.” In short: light weights can help you build muscle mass (with caveats we’ll discuss later), but they’re not a good way to develop strength in terms of your actual ability to lift heavy objects.
When to lift light weights
You can do a lot with light weights, and I’m not downplaying their importance. They’re especially great for beginners because they’re easy to use and not too intimidating. If you’ve never lifted weights before, it might be worth picking up some 5- or 10-pound dumbbells rather than jumping straight to the squat rack. I even have a list of exercises that work best with light weights , such as wrist curls and weighted deadlifts.
If you want to continue training with light weights after the beginner level, that’s also possible—depending on your goals. Indeed, you don’t need to lift heavy weights to build muscle. By light weights, I mean any weights you can lift 12 or more times before you feel the burn or fatigue. These can signal your body to build muscle if you continue training until you literally can’t lift those weights anymore . This is called training “to failure.”
The problem is that lifting light weights to failure is incredibly boring. It’s also easy to stop before you reach failure because you’re tired, bored, and want to quit. If you can lift 20 reps with a certain weight but stop after 12, you’ll miss out on most of the muscle-building benefits.
We also know that most people sell themselves short by doing fewer reps or choosing too light a weight for the exercise they’re trying to do . If you’re not constantly asking yourself, “Can I do more?” you may be missing out on the muscle building (or ” strengthening “) you’re hoping for.
When to lift heavy weights
Muscle size and strength are two different but interrelated concepts. A larger muscle is generally stronger, and vice versa. But if you want to lift something heavy in real life—say, a 22-kilogram bag of cement from the hardware store—it will be easier for someone who trains with 22-kilogram dumbbells than someone who has never lifted dumbbells heavier than 4.5 kg.
Remember how you have to lift light weights to failure to stimulate muscle growth? That’s because our bodies can only recruit a few muscle fibers at a time to perform a given task. If you pick up a 2-pound dumbbell, your nervous system says, “Well, we only need a few motor units to do this,” and doesn’t bother activating the rest. But as you complete the 18th, 19th, and 20th rep, it has to recruit more and more of these fibers, as the ones you used initially begin to fatigue. With heavy weights, however, you recruit a large number of muscle fibers from the very beginning.
Increasing weight signals your body to grow muscle and teaches your muscle fibers and brain to work together. The first time you try a new exercise, it will seem challenging. After a few weeks, or maybe even a few days, you’ll be able to lift much heavier weights more smoothly—even if you haven’t built any additional muscle tissue by then.
To learn how to lift heavy weights, you need to work with them. Many also prefer heavy weights because each set of an exercise requires only a few repetitions—maybe eight or ten, or in some cases, just one repetition. What constitutes “heavy” varies from person to person —I wrote about how to determine what weight is considered heavy for you .
Additionally, when training with heavy weights, you don’t have to push yourself to failure, which is something weightlifters often appreciate. If I have 200 pounds on the bar for squats, I can technically do seven reps. But my daily workout might only include four or five. I find this much more enjoyable than doing 20+ dumbbell squats. The dumbbell is lighter, but using a heavy barbell allows me to stop before I get completely exhausted.
How to combine the benefits of working with heavy and light weights
As with many other aspects of life, the “why not mix it up?” approach is best for most people. Strength athletes (including powerlifters, Olympic lifters, and CrossFitters, to name a few) typically build their training around a few heavy lifts and then add in lighter or moderate “assistance” exercises. This is still a good approach for the average person who simply wants to strength train for fun or for health reasons.
It’s also important to remember that “light” weights should increase over time as you get stronger. Even Jane Fonda, famous for her exercises with small dumbbells, told viewers at the beginning of her famous video that they should move up to heavier weights as they gain experience. This, in a nutshell, is the concept of progressive overload .
Meanwhile, “heavy” refers to any weight that doesn’t require dozens of repetitions . If you can only do about 10 push-ups, then push-ups are considered a “heavy” exercise. Performing a heavy exercise that engages multiple muscle groups gives your body a powerful signal to increase strength, while still leaving plenty of time for lighter exercises, if that’s how you prefer to spend your time in the gym.