How Much Cardio Do I Need?

( – During a recent study, a group of over 40,000 business professionals was asked whether or not they could burn fat by only doing weight training.

About 85% responded that strength training alone was a sufficient way to burn fat.

This is not the correct answer – while yes, increasing lean muscle mass is a vital step in maintaining a healthy, calorie-burning metabolism, there is no way to avoid getting in some cardio if you want to burn fat (and help keep your cardiovascular system strong).

But this answer inevitably leads to yet another popular question: exactly how much cardio do you even have to do?

Q: I’ve read so much conflicting information about just how much cardio I need, and exactly how hard my heart needs to be working to meet my goals. Now I’m confused. Help!

A: Cardiovascular endurance, or aerobic endurance, is a vital component of a complete fitness program. This training makes the heart (cardio), lungs, and system of blood vessels and capillaries (vascular) transport nutrients more efficiently. Knowing how much cardio you need starts with a basic understanding of what these systems do for the body.

A well-trained heart will pump more blood in a single stroke than a poorly trained heart. So let’s suppose your resting heart rate (RHR) is 78 bpm. That means your heart beats 75 times in a minute to move a certain amount of blood. Your neighbor, Fitt Trainer, has a RHR of 68 bpm. That means his heart beats 10 times less in a minute to move the same amount of blood. This efficiency of moving blood with fewer strokes is one of the benefits of cardiovascular training.

A second benefit is the greater exchange of fuel for working muscles. Working muscles need important nutrients like oxygen and glucose in order to perform necessary tasks. A stronger heart will not only beat fewer times in a minute but, as a result of cardio training, will move a greater volume of blood with each stroke. So when you are exercising, more nutrients reach the muscles and the heart doesn’t need to beat as many times.

How Do We Get To A Better Cardio Workout?

There are four essential keys to effective cardio training:

Mode. Which exercises are you doing? That is up to you. Choose rhythmic activities like walking, running, cycling, stepping or cardio equipment. Select an activity that will keep you interested and feel free to change it as often as you like.

Intensity. How hard (or easy) is the activity? Knowing your predicted maximum heart rate (220-age) coupled with the Ratings of Perceived Exertion is a great place to start.

Let’s Take a 38 year old man and name him Charles. For Charles, this max would be 182bpm, and his or her heart rate should not exceed this limit. A more reliable formula is the Karvonen Formula, which determines a target heart rate zone to maintain for cardio endurance.

Let’s look at Charles again, with a RHR of 68pbm, and use the Karvonen Formula to determine the correct THRZ.

Training Heart Rate= Maximum heart rate – resting heart rate x desired intensity (50% -85%) + resting heart rate.

Basic Formula

220-38 (age)= 182 MHR
182- 68 (RHR) x .50 + 68=
114 x .50 + 68=
57 + 68 = 125pbm

Basic Formula (as applied to Charles)

182 – 68 x .85 + 68=
114 x .85 + 68 =
96.9 + 68 = 165 bpm
THRZ is between 125-165pbm.

Performing any type of cardio exercise within this zone will produce positive results but what about how it feels?

How Hard Are You Working?

Once you have determined the zone, make adjustments based on the RPE scale. This scale, ranging from 6-20, is another great indicator of how intense the work is. It’s often a better indicator of whether or not you should increase or decrease the intensity.

Charles is on an arc trainer machine. After a brief warm-up moves, his THRZ is at 135bpm. At the 10-minute mark, he can continue to carry on a full conversation (about a 9 on the RPE) so he begins to increase the intensity. 5 minutes later, now at 145bpm he can no longer speak, even in short sentences, and rates his exertion as 17 (very hard). Even though Charles is well within his zone, he feels like he is working very hard and could probably not maintain this level for very long. But by using the RPE scale either alone or in conjunction with the THRZ, he can  determine how intense the cardio workouts need to be.

How long is each workout? An effective cardio workout can range from 10-30 minutes. Anything more than 30 minutes moves into anaerobic training which is a different stage of training and for the average exerciser is not a necessity. 30 minutes max in your zone and in the middle of the RPE scale will seriously challenge the heart and lungs.

How many times a week? This is somewhat determined by your level of conditioning. A poorly conditioned client can perform cardio 2-3/week on non-consecutive days whereas a client who has passed the initial conditioning stage can do 3-4/week sometimes on consecutive days. Keep in mind that 50% of all new exercisers burn out within the first 6 months so it is far better to maintain 2 days/week of cardio for a year slowly increasing the intensity than 4 days/week for the same year without increasing intensity on an inconsistent basis. 

The Bottom Line: rhythmic activity you like (mode); THRZ and RPE scale (intensity); 30 minutes max (duration); and 2-3/week consistently (frequency).

By Steffanie White, BDO Fitness Expert

Steffanie White is a Certified Personal and Fitness Trainer at Boston Sports Clubs. With over 15 years of experience in the industry, bringing quality fitness information and instruction to clients has become Steffanie’s greatest passion. In addition, this Certified Pilates Instructor teaches dance and fitness classes at Dana Hall and Bridgewater State College, as well as current pursuing a doctoral program in sports medicine.