Some bodybuilders tell me they perform cardio along with their weight training workouts – because they can only get to the gym once a day. They assume it can’t hurt performing cardio after resistance exercise. Many if not most workout programs instruct you to do cardio before hitting the weights.
In a recent edition of the Journal of Applied Physiology, researchers reported that combining resistance exercise and cardio in the same session will short-circuit muscle anabolism.
This study was a good one – it utilized trained individuals and exercise protocols typical of many bodybuilders. Results demonstrated a clear detrimental effect on the activation of the muscle genes that promote anabolism (growth).
Researchers used resistance-trained men and assigned them to either one of two conditions: One experimental trial consisted of a bout of resistance exercise followed by a bout of cardio exercise while in the other trial subjects performed the reverse exercise order (i.e. cardio then resistance exercise).
The resistance training workout consisted of a standardized warm-up followed by 8 sets of 5 maximal effort repetitions (approx 80% 1-RM) . Each set was separated by a 3 min recovery. The cardio consisted 30 min of stationary cycling at approx 70% of the participants VO2max.
Muscle biopsies were taken before, 15 minutes after exercise and 3 hours after exercise.
Results showed that whenever you combine cardio with weight training, it’s a “no-win” situation no matter which order you perform them. Here is what the researchers found when muscle genes were analysed.
Cardio before resistance exercise suppressed IGF-I mRNA expression by 42%! But also induced small declines in MGF (Mechano Growth Factor) by 27%. The bottom line is, cardio before resistance exercise significantly impairs the anabolic response of the workout.
When cardio was performed after resistance exercise it dramatically increased gene expression for muscle tissue breakdown. For example, key “muscle breakdown genes” Atrogin and MuRF mRNA increased 21% and 53% respectively. Results indicate that cardio after resistance exercise up-regulates the muscle genes responsible for catabolism and protein degradation – precisely the opposite of what you’re trying to achieve.
If you want to maximize your results from your resistance training workouts don’t perform them back-to-back with cardio just because its convenient. If you’re going to do cardio and resistance exercise in the same day, perform them at least 8 hours apart. Inconvenient? Maybe. But let me tell you what’s worse, busting your ass in the gym for half of the results you should be getting.