The point of lifting during a fat loss phase is to preserve (and if you’re very lucky even add a little) muscle. It’s aim should not be to primarily burn fat–at least not DURING the workout.
Yes, more moderate weight lifting with higher reps may burn a little more fat during the session, but will do little to nothing to either preserve muscle mass or stimulate your metabolism; in fact, it could overly stress a system in a hypo-caloric state, leading to muscle loss.
Your body needs a “reason” to hold onto muscle during calorically deprived states, as muscle is a metabolically expensive tissue to maintain. The best way to do this is through low rep heavy training.
If you combine this with short rest intervals, e.g., by arranging your compound movements into circuits with 60 sec. or less rest between movements, you maintain adequate recovery between subsequent sets of the same movement, while simultaneously creating a significant EPOC (excessive post-exercise oxygen consumption).
This allows you to keep the weights heavy while using compound movements which involve more muscle mass. The more muscle stimulated, the higher your metabolic rate will be elevated post-exercise (as well as the greater the likelihood you will retain that muscle mass).
Furthermore, compound movements are a much more effecient way to stimulate muscle–both in terms of intensity and quantity. For example, chin-ups are an excellent back exercise as well as a great biceps builder.
In this way you can keep your workouts short and intense–which is essential when in a calorie deprived state. Dieting is enough of a stress and provides your body with fewer substrates for recovery, thus your workouts must stimulate the maximum amount of muscle in the least amount of time.
Here’s a recent circuit I did (yesterday in fact):
A1) Deadlifts: 4X6
345 X 6 355 X 6 355 X 6 355 X 6
REST: 60 SEC.
A2) Dumbbell Bench Press: 4X6
85's X 6 90's X 6 95's X 6 95's X 6
REST: 60 SEC.
A3 Standing Calf Raise: 4X6
210 X6 210 X 6 210 X 6 210 X 6
REST: 60 SEC.
A4) Supinated lat pulldown: 4 X 6
190 X 6 190 X 6 190 X 6 190 X 6
REST: 60 SEC.
A5) Decline Crunches: 4 X 6
35lb. plate X 6 35lb. X 6 35lb. X 6 35lb. X 6
REST: 60 SEC.
Repeat circuit 4 times
I keep my total reps in the 24-30 rep range for each movement.
I use full body workouts(generally, 3X week)with compound movements, as they are the most effecient and work well to manage nervous system fatigue. I will sometimes do an upper/lower split and one full body workout in a week, and if I’m very pressed for time two full body workouts.
I follow up each workout with 20-30 min. of moderate intensity cardio. On off days I keep my activity level high by walking, swimming, lawn mowing, various other outdoor activities.
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