How much cardio do I really need?
Cardiovascular exercise, or cardio, i.e. swimming, running, cycling, etc., promotes weight loss, endurance, and is great for getting your heart rate up and making your blood pump faster. There are however downsides to cardio, including your decreasing your resting metabolism rate, constrained energy expenditure, and possible muscle loss. This post is about the effects cardio has for people looking to lose fat, gain muscle, or those just looking for a healthier lifestyle.
The benefits of cardio
Starting with the good news, there are 3 major benefits of cardio, weight loss, strengthening the heart, and being a great transitional workout. Those alone, or just the enjoyment of doing it, sway many into putting cardio into their exercise routine.
A cardio workout increases blood flow and acts as a filter system. It brings nutrients like oxygen, protein, and iron to the muscles that you’ve been training and helps them recover faster.
Harley Pasternak, personal trainer, motivational speaker, author and television host
Firstly, cardio does promote weight loss. According to Healthline.com, if you weigh around 160 pounds, a 30-minute jog would burn around 250 calories, with the calories increasing if you weighed more, or if you run faster. Compare this to weight training, where you would only burn between 130 to 220 calories in the same amount of time. A big chunk of losing weight is burning calories and in that sense, cardio does a great job in helping you achieve this.
Secondly, cardio is a great workout for your heart and lungs, your cardiovascular system. Cardio is a workout that speeds up your heart rate, so it’s not surprising that it would help your heart muscles grow stronger. In essence, cardio pushes more oxygen into your bloodstream without putting too much pressure on your body, making cardio great for people who want to maintain their current weight or add some exercise to their daily lives. It’s also one of the best options for people who have heart problems or are slightly injured.
Lastly, cardio is a great transitional workout. Unlike cardio, weight training puts a lot of stress on your body, this makes it a bit intimidating and unattractive to people who haven’t worked out for a while. Starting with cardio before doing a harder workout decreases the chance of injury, and trains your body to breathe properly. Cardio is not just a good transitional workout for weight training, but also as a warm-up for High-Intensity Interval Training (HIIT) or endurance training.
How much cardio in a week? Recommendations suggest you get at least 150 minutes of moderate aerobic activity or 75 minutes of vigorous aerobic activity per week, or a combination of moderate and vigorous activity. Greater amounts of exercise will provide even greater health benefits.
The importance of muscle growth
While cardio is good for your heart and lungs, the bad news is that cardio doesn’t really help your metabolism, in fact, it can discourage muscle growth and leaves you with constrained energy expenditure. Scientifically, according to Gravity Transformation, “Cardio reduces the activity of mTOR, which is a crucial enzyme for muscle growth while also raising AMPK, which is an enzyme that impairs muscle growth,” More simply put, regular cardio exercise causes two key enzymes to work against your body to inhibit muscle growth.
Now, even if muscle growth (or looking like the next Arnold Schwarzenegger) is not your main goal, weight training has an advantage over cardio by maximizing the calories you burn when you are resting! This is known as the after-burn effect, or more formally the Excess Post-Exercise Oxygen Consumption, or EPOC.
After an intense cardio session, your EPOC duration lasts about 3-24 hours, and it makes up around 6-15% of the net total oxygen cost of the exercise. This means your body burns little to no calories more than it did during your workout. HIIT workouts also only burn around 30-60 more calories per day while resting, but weight training has the highest EPOC and burns about 150 calories while you are resting after your workout. Amazingly, you can burn as many calories resting as you did lifting weights in the gym. This high EPOC for weight training is due to the energy required to grow muscle, and because muscle as a tissue burns the most fat for fuel.
Whether you are doing both cardio and weight training, or just cardio, it is important to understand that cardio does not help your muscles grow, and in fact, that it slows the muscle growth. If you do both cardio and weight training it’s important you do the weights first or wait for a long period after your cardio workout before starting to lift weights. Cardio exercises prohibit you from reaching optimal stimulus or maximum potential which is key for repairing and building muscles. It also reduces your production of mTOR enzymes and obstructs hypertrophy or muscle growth exercises.
Finally, it’s worth understanding the relationship between cardio and constrained energy expenditure. Doing cardio before eating, or doing too much of it, can result in constrained energy expenditure. This is when your body wants to save as much energy as possible and stops doing simple tasks you would otherwise normally do. This could be small things like sitting down more, fidgeting less, or not wanting to walk your dog. This may not seem like a big problem but this ‘constrainment’ may actually prevent you from burning calories that you would otherwise normally burn, not only making your afterburn less effective but possibly even slowing down your metabolism as well.
So, who should do cardio?
In the end, there are both pros and cons to doing cardio. Cardio isn’t great for quickly gaining muscle, or for beginners to weight training. Cardio is also not the most effective for extreme weight loss, however, it’s great for maintaining shape and having healthy lungs and heart. Cardio is also good at removing visceral fat around your abdominal organs, and subcutaneous fat that’s stuck under the skin. However, while exercise will keep you fit, to keep your shape a healthy diet is the most effective! Cardio does not replace a good diet.
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