How hard do you have to push yourself to get stronger?

You're sweaty and sore, and just hoisting your gym bag onto your shoulder makes you groan. The workout was exhausting, but was it effective?

- ALYSSA AGES

Many trainers and athletes have long believed that lifting to failure — the moment when you can’t complete another repetition of an exercise — is the best way to build muscle. But recent research has challenged that idea, suggesting that training at a slightly lower intensity can produce similar results.

"The question I ask people is, ‘Are we getting better or are we getting tired?,” said David Frost, an associate professor in the kinesiology department at the University of Toronto in Canada.

If you're new to lifting, it can be tough to know how hard your workout should feel. Learning what failure feels like — and understanding when you should push that far — can help you build a sustainable strength training routine and allow you to safely progress as you get stronger.

What is training to failure?

There are two types of failure in strength training. “Technical failure” is when you can’t do another repetition with proper form and control, so you may have to rely on other muscles and joints to lift.

“Muscular failure” happens when your muscles are so fatigued that you can’t lift the weight at all. Although you can build muscle mass by training to failure, some experts say the risks may outweigh the benefits.