Published 12/12 2011 10:00AM

Updated 12/12 2011 10:51AM

Is Resistance Training a Good Cardiovascular Workout?
Most fitness experts recommend a combination of aerobic exercise and resistance training to build muscle strength and boost aerobic capacity and heart health. Traditionally, cardio exercises such as running, aerobics or cycling were thought to be best for cardiovascular training and resistance workouts best for building muscle strength. But these days more people are using circuit resistance training as a substitute for aerobics. With circuit resistance training, you move from one strength exercise to the next with little rest between sets. This elevates the heart rate more than traditional weight training where there are longer rest periods between exercises. Is circuit resistance training a good substitute for cardio?

Do You Need to Do Cardio if You Lift Weights?
Most people prefer strength training over running or cycling on an exercise bike. They'd rather flex their muscles with weights than spend 30 minutes working out on a cardio machine. It would be music to their ears to find out that circuit resistance training conditions their heart as well as traditional aerobic exercise does. Unfortunately, this may not be the case.
It's logical to think that resistance training boosts aerobic capacity. After all, your heart rate goes up when you lift weights, and it's elevated even more when you do circuit style training. There are some differences though.
When you do one of my aerobic videos or run on a treadmill, your heart rate increases along with stroke volume which is the amount of blood the heart pumps to the body with each beat. This increase in heart rate and stroke volume allows muscles that are now more metabolically active to receive greater amounts of blood and oxygen.
When you lift weights or do some other form of resistance exercise, your heart rate rises, but stroke volume and oxygen delivery don't increase like they do with aerobic exercise. The increase in heart rate that occurs with resistance training is a reflex response that's triggered by muscle contraction. As a result, you don't get the same increase in oxygen delivery to the muscles with resistance training. This reduces the cardiovascular training benefits.

Does Circuit Resistance Training Have Cardiovascular Benefits?
Resistance training with periods of rest between sets has little cardiovascular training effect. If you minimize the amount of time you rest between sets to 30 seconds or less, you get slightly more benefits but not equivalent to what you'd get during an aerobics class, running on a treadmill or cycling on a bike. According to ACE Fitness, circuit resistance training boosts aerobic capacity around 6%. In contrast, running and cycling can increase aerobic capacity by as much as 25%.

Does This Mean You Have to Do Traditional Cardio to Train Your Heart?
Circuit resistance training may not be the best way to increase your aerobic capacity, but there are ways to make it better. Instead of doing straight circuit training, do 1-minute cardio segment between each resistance training exercise. When you finish each strength set, grab a jump rope and skip rope for a minute, do jumping jacks or run in place before picking up the weights again. This will give your heart the additional stimulus it needs to adapt without doing traditional cardio.

Resistance Training Has Other Benefits
Even though resistance training alone doesn't significantly increase aerobic capacity, it does indirectly benefit the heart. Research shows that circuit-style resistance training helps to reduce blood pressure over time in some subjects. Aside from its effects on the heart, it also increases lean body mass, bone density and improves strength. Almost everyone can benefit from some form of resistance training.

The Bottom Line?
Resistance training has benefits, but it isn't a good substitute for cardio. Circuit resistance training can modestly improve aerobic capacity but not as much as cardiovascular exercises like aerobic classes, running or cycling. To improve the cardiovascular benefits of resistance training, do short intervals of cardio between each resistance set. Otherwise, keep strength training, but make time for cardio too.
ACE Fitness. "Why Is an Elevated Heart Rate Alone Not Always a Valid Indicator of an Effective Aerobic-Training Stimulus?" "Strength Training and Hemodynamic Responses to Exercise: Summary and Clinical Application" "Endurance Exercise and Resistance Training in Cardiovascular Disease: Benefits of Resistance Training"

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