https://physoc.onlinelibrary.wiley.com/doi/10.1113/JP278056
Exercising until you can't do any more (exercise to failure) maximises the amount of muscle used and so is very good for encouraging muscle growth (muscle hypertrophy). This research paper looked at the difference in the amount of muscle used when exercising to failure with heavy weights compared to light weights. They found that as long as the person went to failure it made no difference what weight was used. So if your exercising to failure the weight you use does not matter.
