Becs also said that people think picking up the heaviest weights they "can possibly bicep curl" will get them toned arms quicker than "just doing reasonable weight." Heavier weights do not necessarily lead to quicker muscle tone because, she said, you're more likely to end up injuring your muscles trying to take on those loads that you can't actually handle. Injured muscles equals inability to train as often.
When asked if she had tips for finding the best weight for toning muscles, Becs said, "You're going to be looking to go into hypertrophy training, where you're lifting about 10 to 12 repetitions of the weight for three to four sets. What you want to be able to do is complete every single one of those moves with control." That means, you're not letting the weight take your arm down or slamming it back to the floor, and you're not using any other area of your body to move the weight, other than the muscle group you're working on, she said.
For example, sometimes people will use their knees to pop up into a shoulder press when they're tired, Becs explained. Lifting the right weight is still going to fatigue you by the third and fourth sets — "you're obviously going to be tired," she said — but you're not "cheating" your way by using other parts of your body to lift the weight. Here's more on how to choose the right weight.
Personal trainer Katie Crewe, CSCS, added that she'll hear people say, "'Oh, I'm lifting lighter weights because I want to tone. I don't want to get bulky, so I'm not lifting heavy.'" But, she said, research shows that you can get similar muscle gains lifting lighter weights for more reps as opposed to heavier weights for fewer reps if you're "still going within a couple of reps of failure because you're still getting the same hypertrophic response."