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How Much Cardio Should You Do For Good Health?
So as we get close to that time of year when we make New Year resolutions, I thought I would give some advice on one of the most popular ones. Exercise is one of those resolutions that many people want to start with, but there are some barriers in terms of knowing what to do. The subject of this blog is aerobic exercise which is an activity that brings your heart rate into an aerobic zone. This involves using large muscle groups in a continuous manner to bring the hear rate up to the aerobic zone. I will talk about hear rate and aerobic zone later.
What Are The Health Benefits of Aerobic Exercise?
Regular aerobic exercise has a positive impact on every modifiable risk factor for heart disease.
- High blood pressure: Regular aerobic exercise can reduce blood pressure by 5-10mmHg. This is a 10-20% reduction in the risk of having a heart attack.
- Cigarette smoking: Smokers who become active are more likely to stop or reduce the amount they smoke.
- Diabetes: Regular aerobic exercise improves resting blood glucose levels, reducing the complications for Diabetes.
- Aerobic exercise reduces bad cholesterol (LDL cholesterol) and increases good cholesterol (HDL cholesterol)
- Aerobic exercise only has a moderate effect on weight loss, but this also has a positive effect on cholesterol, blood pressure and blood sugar.
- Decreased risk of stroke and some forms of cancer.
- Aerobic exercise preserves bone mass and reduces the risk of falling in older adults.
- Aerobic exercise assists in prevention and improvement of moderate depressive disorders and anxiety.
- Aerobic physical activity improves cognitive function and lowers the risk of dementia.
Sitting involves low levels of energy expenditure and includes activities such as television watching, computer use, and sitting in a car or at a desk. Spending long periods of time in sedentary activities is associated with elevated risks of heart disease mortality and depression; increased waist circumference, elevated blood pressure, increases bad cholesterol. It also has a negative impact on chronic disease biomarkers such as blood glucose, insulin, and lipoproteins. Research has even shown that being sedentary is detrimental even among individuals who meet the minimal physical activity recommendations.
To counter these detrimental effects to health, it is recommended to take breaks, even just standing to break up sedentary activities. When looking at your activity level as a whole, it is important to look at how much your week is spent just sitting, even though you might be meeting the minimal activity guidelines.
What Are The Recommendations for Aerobic Exercise?
These recommendations are taken from The American College Of Sports Medicine. ACSM Guidelines on Exercise
To achieve the health benefits of aerobic exercise it is recommended to accumulate moderate-intensity exercise (40-60% of Heart Rate Reserve [HRR]) for at least 30 minutes on 5 or more days a week, for a total of 150 minutes per week. Or, vigorous-intensity exercise (60-85% of HRR) for at least 20-25 minutes on 3 or more days a week for a total of 75 minutes per week. For weight loss, 50-60 minutes per day to a total of 300 minutes moderate exercise is recommended. Interestingly, they also recommend that intermittent activities in 10-minute increments have same health benefits as continuous activities. Durations of exercise in 10 minute intervals may result in fitness and health benefits, particularly in sedentary individuals however, the evidence is sparse and inconclusive.
Large prospective studies show that energy expenditure of 1000 kilo-calories per week produce the above benefits of aerobic exercise. Some studies have even shown health benefits starting at just 500 kilo-calories.
How to exercise at the right level for Aerobic Exercise?
One of the simplest and safest way of monitoring if you are working in your aerobic zone is to use The Rating Of Perceived Exertion Scale. The Table below shows a simple version of this scale. Exercising at a moderate intensity involves exercising between 40-60% of heart rate reserve, or 4-6 out of 10 of perceived exertion. At a vigorous intensity, you want to rate yourself between 6 and 8 out of 10 on the scale. The scale uses how difficult it is to converse while exercising. If you are exercising on your own. just use common sense on hard you feel you are working.
Rating of Perceived Exertion (RPE) On A Scale of 1 to 10
|1-2||Extremely easy. You can easily carry on a conversation.|
|3||Very easy. You can converse with almost no effort.|
|4||Moderately easy. You can converse with a little bit of effort.|
|5||Starting to get challenging. Conversation requires more effort.|
|6-7||Difficult. Conversation requires a lot of effort.|
|8||Very difficult. Conversation requires maximum effort.|
|9-10||Full-out effort. No conversation is possible.|
How To Calculate Your Heart Rate To Exercise In The Aerobic Zone.
The rating of perceived scale is enough for most people, but it useful to know the heat rate method as well. It is not complicated at all. Some people like to use heart rate monitors, but you need to check the reliability of these models. I would not recommend using the heart monitors on treadmills and cross trainers in the gym.
40-60% of (HRR) heart rate reserve is considered moderate intensity and 60-85% heart rate reserve is considered vigorous. Very deconditioned individuals may begin to improve at about 30-40% of HRR. Your heart rate reserve is calculated as follows:
Max heart rate at 220 (beats per minute), minus your age. This equals your estimated heart rate. You then subtract your resting heart rate to give you your heart rate reserve. Example:
Max heart rate 220 BPM minus age 50 = estimated max heart rate 170 beats per minute (BPM)
Estimated max heart rate 170 BPM minus minus resting heart rate 70 BPM = 100 BPM Heart Rate Reserve.
If I want to exercise at 40% of my heart rate reserve, I can calculate my target heart rate for aerobic exercise.
Heart rate reserve 100 BPM x 40% = 40 BPM
40 BPM plus 70 BPM resting heart rate is a target heart rate of 110 beats per minute.
You can then calculate the same for 60% of heart rate reserve, to give you a target heart range between 40% and 60%. This would be for moderate intensity exercise.
If you want to see this calculation in more detail, the following website link lays it out very well:
I think it is a good idea to work out your heart rate zone and then you just know what it feels like in your body. Once you have that sense you don’t need to keep taking your pulse, you will just know you are in the right zone. My advice is to use this calculation with the above Rating Of Perceived Exertion. When you know what your target heart rate is in beats per minute, you can just calculate the equivalent in 10 seconds and then take your pulse.
You can check your hear rate easily and match it with the perceived exertion scale. This is another link to an easy explanation of how to do this: Check Your RPE And Heart Rate
Putting it all together.
Using the guidelines from the American College Of Sports Medicine above, start with a workout of 10 to 20 minutes duration. If you are already used to cardio, you could do between 20 and 6o minutes.
If you are very de-conditioned you may even need to split it up into several 10-minute segments. Increase your duration by 5 minutes a week until you reach the minimal recommendations.
If you are starting out with cardio, pick something simple like walking, bicycling or cross trainer. A gym membership is ideal, as I think it is a good idea to combine your use of the equipment. Don’t get bored, take music with you!
Set your goal for the duration of each session and then work in your aerobic zone until you achieve the time goal. Then you can increase the intensity of your heart rate zone when you feel it’s too easy. Unfortunately, if training is discontinued, gains in fitness regress by approximately 50% within 4-12 weeks. So keep it up!
If weight loss is your goal, frequent, enjoyable exercise periods of low to moderate intensity and relatively long duration result in the largest weekly caloric expenditures.
Stay within your heart rate range. Monitor using a good heart rate monitor or manually at the carotid artery on the neck or radial artery on thumb side of wrist. Otherwise use the Rate of Perceived Exertion Scale above. Measure Your Heart Rate
If you have any questions about the heart rate zone, you can email me and I can work out your aerobic zone. I wont be able to provide specific training recommendations unless you are a patient and have a physiotherapy assessment.
About the Author
Damian Wyard trained is a Registered Physiotherapist and Stott Pilates Rehabilitation Instructor with 20 years experience in his field. He is the owner of Pilates4Physio in Toronto. You can reach him privately at firstname.lastname@example.org, or at his Pilates studio www.pilates4physio.ca www.facebook.com/pilates4physio