And I’m here to rock your world: It’s not.
First, where this all comes from. Cardio has been used in bodybuilding programs for decades to get to single digit body fat percentages. Most competitors are sitting at 7 to 8% body fat the day they step on stage. This gets perpetuated on and on by word of mouth: “I lost 15 pounds just walking for 60 minutes a day!” What they don’t tell you is, after that 15 pounds of loss -- it stops. Their body has metabolically adjusted to the demand, and the only way to increase the weight loss is to go for longer periods of time. This same situation will be reflected in many of the bodybuilder’s weight cutting regimes. Starting out at 25 minutes a day, 3 days a week and finally peaking the week of the show at 60 to 90 minutes 5 days a week to cut that last bit of fat.
The main way to cut weight, as I laid out in my previous article, eating at a calorie deficit is the way to cut that weight.
So, even though cardio is largely useless for weight loss, you should still use it for Cardiovascular Fitness, right? I mean, the most important muscle in your body is your heart, right? Well, not anymore.
A new study (available for free and in full here) lays it out plain and simple: "Resistance training performed to failure can induce acute and chronic physiological effects which appear to be similar to aerobic endurance training, which in turn produces similar enhancements in CV fitness.”
Yes, resistance training, when done to failure will produce the same cardiovascular fitness benefits that actual cardio work will. So, not only will you be strengthening your heart by lifting to temporary muscular failure, but you will be getting stronger and bigger at the same time.
The conclusion: The single most efficient use of your time in the gym is lifting until you can’t lift anymore.
The study did provide one specific qualifier for their study. The effect of resistance training on the cardiovascular system is lessened the more trained an individual becomes. For instance, a professional athlete would not see much of an increased benefit in their sport’s specific demands for cardiovascular fitness because they are already highly trained.
So, what is cardio good for? It depends on what sort of cardio you’re doing. High Intensity Interval Training (HIIT) is fantastic for aerobic endurance and VO2 Max (your body’s ability to use oxygen). It is also the only cardiovascular exercise that is has been linked to metabolic adaptability. You can do the same set of intervals, without your body adapting like typical, moderate intensity cardio.
Another type of effective cardio is speed work, or essentially intervals with resistance: parachute sprints, sled drags or pushes, and so on.
Finally, if your sport is a cardiovascular endurance event, the best way to train for it is to do the sport. So, if you're doing a marathon or an ironman event -- hit the pavement, and hammer out the cardio along with some resistance training.