Should I Lift Heavy or Light?

As professional trainers, that's one of the questions I've heard at the gyms many times.  The answer (like most answers) is "IT DEPENDS"!!!  Experts tend to group resistance training goals into 3 groups: endurance, hypertrophy, and strength.

Endurance training is for beginners and for the experienced lifters who would rather "tone" than get bigger or stronger.  Choose a weight that you can lift 15 to 20 times.  This type of workout stimulates an increase in aerobic enzymes and mitochondrial density which improves endurance.

On the other hand, hypertrophy training is for those experienced lifters that would like to add size.  Choose a weight that you can lift 8 to 12 times.  This will stimulate an increase in size of the muscle fiber with added contractile proteins like actin and myosin.

Furthermore, strength goals are for those who would like to get stronger without necessarily getting bigger.  Experienced lifters should choose a heavy weight they can only lift 1 to 5 times.  This will enhance greater, more efficient, neural response while lifting heavy weights.

In conclusion, recent studies have shown that emphasizing one protocol but utilizing all 3 will elicit the best results for muscular fitness.  Happy Lifting!!!