What Really Happens When You Lifting Weights That Are Too Heavy For You

While lifting heavy weights is great for your overall health, as you get started with a strength training routine, it's important to take it slow and gradually add weight. Starting with a weight that's too heavy for your current fitness level can be downright dangerous and can increase your risk of injury.

"A good guideline is to lift heavy enough that the last two to three reps on each set feel challenging to complete but not so hard that you can't do them with proper form," certified personal trainer Cassie Lynn Lambert, wrote on Self.com. "After the last rep, you should feel close to maxed out with enough energy left to do however many sets you have left."

Note that having a weight feel challenging on the final repetitions means the first few repetitions with a weight should feel fairly easy—you want to feel challenged, but not struggling. You will be able to increase the weight over time, so don't feel intimidated if you're starting with a small weight. This isn't just a newbie mistake: Plenty of seasoned weight lifters will add a new exercise to their routine and choose a weight that's far too heavy for that particular movement.

The weight that you lift is important, but your form in the movement is even more important. Lifting heavy weights can cause you to recruit muscles that aren't supposed to be used in the specific exercise that you're doing, and in addition to risking injury, you're also just not getting an efficient workout. "If you are just swinging weight around in a way that is uncontrolled, your muscles are not really working. You must control the weight in order to form that mind-muscle connection," Fitplan's trainer Scott Mathison told NBC News.

Remember, it's always better to start light and slowly add more—you're better to lift a little lighter than you're capable of and then come back and work out again tomorrow, versus going for that slightly too-heavy weight and ending up injured and out of the gym for eight weeks. Don't neglect the other workout staples like a warmup and cool down, especially when doing heavier lifts. And never sacrifice form for the sake of squeaking out an extra rep (via Harvard Health).