When guys who work out a little bit lift heavy weights (85% of their max), their triceps muscles grow faster and more reliably than when they lift light weights (30% of their max)—so how heavy you lift might change when your muscles start getting bigger.

If you're a young woman just starting weight training, slowly lifting heavier weights over time will make your triceps (the back of your arms) grow about twice as much as just doing the same workout over and over.

Even if you lift the same weight every time without making it heavier, your arms can still get noticeably bigger in just two months — at least when you're just starting out and you're a young woman.

If you do push-ups or bench presses with light weights until you can't do another rep, twice a week for two months, your arms and chest will grow just as much — so push-ups can be just as good as gym machines for building muscle, if you push yourself just as hard.

This claim says that lifting lighter weights until you're tired, done regularly for six weeks, can build muscle just as well as lifting heavier weights. It specifically found growth in arm and chest muscles, showing you don't always need heavy weights to get stronger.

When people who’ve never lifted weights before train their chest and arms with the same total muscle tension time, the back part of their triceps (near the elbow) grows more than the middle or shoulder-end parts.