This is because light weights are more effective than heavy weights when it comes to building muscle, according to researchers at McMaster University in Canada.
In their study, the researchers found that carrying out more repetitions of light weights could build muscle mass just as effectively, if not more so, than lower reps of heavy weights, 'The Daily Telegraph' reported.
Lead author Nicholas Burd said: "Other resistance protocols, beyond the often discussed high-intensity training, can be effective in stimulating a muscle building response that may translate into bigger muscles after resistance training."
There is a catch.
Trainers must still carry on pumping iron until they can do no more -- known as reaching fatigue -- in order to build muscle mass. With lighter weights that could mean much longer in the gym to achieve similar results, say the researchers.
However, Burd said the lower intensity workout could be better at building muscles because the higher repetitions "sustained the muscle building response for days".