If you’re just starting a program, coming back after taking some time off from the gym, or recovering from an injury, it’s important to avoid lifting heavy on your first day. Eventually, you’ll need to increase the weight you lift, but as you get started, using lighter weights can help you get your form right and still build muscle.
It can be risky to lift heavy weights, especially if you’re using improper form, don’t have a spotter, or try to lift weights while recovering from an injury. However, if you’re untrained—that is, new to weight lifting or deconditioned from a long time off—lifting about 30% of your one-rep maximum (1RM) has effects on muscle growth similar to lifting 70–80% of your 1RM. To see these results, you’ll need to use high-rep counts (think 4 sets of 12–15, or until failure). When your muscles are tired, they still use the same amount of energy—despite the weight—causing them to repair the muscle similar to higher load lifting, resulting in muscle growth.
Using light weights for a few weeks gives you a chance to check your form too. When you’re getting back into it, just doing the movements with the proper technique can lead to quick changes and strength gains because you’re using the muscles as they’re designed—instead of compensating with the rest of your body. Build it into your periodized program, and after 3–4 weeks of light lifting, you can start to increase your weights. If you’re working around an injury, or just coming back from one, be sure to check with your healthcare provider about any restrictions to how fast you can progress.