Whether you're training for your first 10K, adding onto long bike rides, or working toward your first pullup, weight lifting has something to offer for everyone. That said, having so many options at your fingertips can sometimes feel overwhelming, especially when it comes to strength training and the question of lifting light vs. heavy weights. How do you make sure you’re hitting all the right muscles? When are light weights or heavy weights better for your upper-body workouts? We turned to Peloton instructors Rebecca Kennedy and Ally Love for their expert tips on choosing the arm workout that’s right for you.

The Weighty Debate in Strength Training

First things first: You can lift both light and heavier weights. In fact, including both in your training routine can be good for you, according to Ally. “Diversifying your fitness portfolio is extremely important in working various muscle groups, including both the local smaller muscles and global larger muscle groups,” she says, adding that exercise diversity “makes working out much more enjoyable!”

Light Weights vs Heavy Weights: The Core Differences

As you’d imagine, the main difference between heavy and light weights is not just how much they literally weigh, but how difficult it is for you to lift them. A weight that’s “heavy” for one person could be someone else’s warm up set. Both intensity levels have their benefits.

Benefits of Heavy Weights

Lifting heavy weights can have a slew of benefits, such as improving your overall strength, size, and endurance. In addition to supporting your muscles, lifting heavy also increases your bone mineral density, which in turn helps decrease your likelihood of fractures and skeletal injuries. Heavy resistance training has also been shown to reduce your risk of heart attack and stroke, increase your resting metabolic rate (aka how many calories your body burns while at rest), and promote healthy aging. 

Advantages of Light Weights

Exercises with lighter weights, on the other hand, are more about increasing muscular endurance. That’s why instructors often program a lot of repetitive movements; working with lighter weights can “build endurance strength, build the muscles around damaged joints or ligaments, and help prevent injuries,” Ally says.

If you’ve never done strength training before, you might find working with lighter weights to be less intimidating, Ally adds. They’re also a great entry point for anyone with pre-existing injuries or a limited range of motion. And as you grow stronger and become more comfortable with the moves, you can begin branching out to heavier upper-body workouts too.

Is It Better to Use Heavy or Light Weights?

As with so many things in fitness, the answer is really “it depends.” These two types of workouts have different purposes, so you may want to focus on the one that best meets your training needs. When choosing your weights, you first want to determine your fitness goals. For example, are you looking to improve your overall fitness, increase your stamina, or build muscle mass?

Light Weights vs Heavy Weights for Muscle Growth and Endurance

As you lift more and more, you’ll naturally get stronger and need to move up in weight. It’s important to change up your weights as you progress, whether that means doing a few more reps or moving up to the next dumbbell on the rack. (One strategy is to increase your weight once you can comfortably do 12 reps.)

Risk of Injury and Form

Any exercise carries some risk of injury. Make sure you practice proper form during your lifting and build rest days into your schedule. Pay attention to how your body feels during your workout. You can always start out with a lighter weight to work on your form before progressing to a heavier one.

Incorporating Different Weights into Your Routine

Periodization and Variation

Ally recommends doing upper-body strength workouts two to four times a week, depending on your goals. Some workouts also “allow you to train with various loads specific to the exercise and muscle group,” Rebecca says. “For example, you can do lighter loads for rotator cuff strengthening, heavier loads for biceps, and medium dumbbells for kickbacks.” These types of workouts are programmed for general strength and building muscle or increasing muscle mass.

Listening to Your Body

You’ll know you’re lifting the right amount of weight when your last few reps feel like a struggle, but not so much so that you can’t maintain your form. It’s normal to feel like your muscles are engaged and working while lifting, but experiencing sharp pains or cramping is a warning that you should take a break and reassess. 

Finding the Right Balance in Weight Selection

Ultimately, what matters most is not how much weight you choose, but whether you’re willing to push yourself and stick with it. “If it challenges you, it's for you,” Rebecca says. “Push-ups will always be challenging until, one day, they're not—if you keep doing them. It's the most gratifying feeling to witness your own strength improve, finally get your first push-up, notice you're able to lift heavier weights, see the peak of your bicep when you flex, and to feel insanely proud when things that were once beyond your imagination are your reality. If those things are meaningful to you, I'll see you on the mat and help make you the strongest version of yourself.”