What ‘training to failure’ means and how to incorporate it into your workout

No pain, no gain, as the old exercise adage goes. But just how much pain do you have to endure to benefit from weight training? That depends on what you’re trying to accomplish, fitness experts say.

For years, some trainers have instructed gym-goers that to get the best results, they need to train “until failure,” meaning until you cannot physically do one more repetition or exercise. Some recent studies, however, suggest this extreme regimen, when applied to weight training, may only benefit certain people.