ENGAGE OTHER MUSCLE GROUPS
Exercises that use many different muscles, such as squats, burn more calories than exercises that use fewer muscles, such as crunches. Cosgrove accentuates this effect by using unbalanced weights that force the muscles of the shoulders, core and hips to come into play as stabilizers.
You need to increase the number of exercises you can do when off balance by using unilateral moves like lunges. This way, while you do eight repetitions for each arm or leg, the stabilizer muscles do 16 for each set, working the abs reflexively.
Muscle fibers have different sizes and the body activates the ones it needs from time to time. Your goal is to activate the thickest fibers, which use the most energy and burn the most calories. You can do this in two ways: first of all by increasing the load, because by lifting heavier weights you use larger fibres. Or moving the weights faster, because it’s more challenging than moving them slowly and therefore involves bigger fibers. Whatever technique you use, don’t take it to extremes but commit: as Cosgrove says “if you don’t struggle it doesn’t work”.