A new study reported in The New York Times finds that people who lift relatively light weights can build just as much strength and muscle size as those who grunt through sessions using much heftier weights.

Traditional weight-training programs set the bar with the heaviest amount of weight an individual can possibly can lift one time. This is his or her one-repetition maximum weight, and it determines the rest of the program, which typically calls for lifting a percentage of that amount eight to 12 times to reach fatigue.

A new study funded by the Natural Sciences and Engineering Research Council of Canada and published in May of this year recruited 49 young men who had been weight training for a year or more. One group was assigned the standard weight-training regimen, and the other volunteers began a lighter routine. Each group lifted their respective weights until the muscles were exhausted. The results showed no significant differences between the two groups. All of the men had gained muscle strength and size, and these gains were almost identical, whether they had lifted heavy or light weights.

The key to getting stronger for these men was fatigue. The volunteers in both groups had to attain almost total muscular fatigue in order to increase their muscles’ size and strength.