We have always heard that in order to gain muscles, we need to lift heavier weights because light weights are not as effective. The key is to lift a higher number of repetitions with lighter weights, so that your muscles get just as tired as lifting heavier weights.
“Lift to the point of exhaustion, and it doesn’t matter whether the weights are heavy or light,” Stuart Phillips, a professor of kinesiology at McMaster University in Ontario, Canada, said in a statement.
Most women probably need to reconsider what they think is “light”, as most women consider a 5kg dumbbell to be heavy. Most often, women are not lifting their approximate light weight level, which is 30 percent of their maximum capability.
“Fatigue is the great equalizer here”.
In 2010, researchers at McMaster University in Canada, conducted a study by looking at two groups of professional weightlifting men (no women were included in this study—boo!) who followed a 12-week full-body routine — one group with heavier weights and fewer repetitions, the second group with lighter weights and more repetitions. After their muscle and blood samples were analyzed, their key measures of strength were the gains in muscle mass and fiber size; they were essentially identical.
This means that fatigue, not weight, helps us get stronger. However, for people who are in a hurry, heavy weights are probably still your best bet!