The truth is, there's no correct strategy -- both are valid choices. Lifting heavy dumbbells, kettlebells and barbells will certainly make you stronger. But lighter weights can help you get stronger too -- it just may take you a bit longer. It all comes down to one important factor: muscle fatigue.

Is it better to use heavy or light weights?

Lifting heavier weights for a fewer reps, which calls for a shorter workout, actually builds more muscle than a longer workout using lighter weights. The more muscle mass you have, the faster your metabolism will be. You'll burn more fat even when you're not working out, because muscle burns more than fat.

When should I use heavier weights?

“A good rule for when someone should up the weights they use is to see if they can perform all the reps and sets with proper form,” Suter says. “If they had two to three more reps left in them, then it is time to go up in weight.”