Aerobic exercise: what you need to know

Aerobic exercise - what you need to know

What is aerobic exercise?

‘Aerobic’ exercise refers to exercise that requires the consumption of substantially more oxygen than at rest. It involves repeated rhythmic movements of the large muscles of your body, such as those in your arms or legs.

Examples of aerobic exercise include

  • brisk walking;
  • jogging;
  • swimming;
  • cycling;
  • dancing;
  • cross-country skiing;
  • ice-skating;
  • kayaking;
  • roller-blading; and
  • aerobic dance (often simply called aerobics).

Because you need more oxygen to do aerobic exercise, you breathe more rapidly and deeply to get extra oxygen into your lungs. Your heart also beats faster to deliver more oxygen-carrying blood from your lungs to your muscles.

How fast your heart beats and how rapidly you breathe will depend on how intense (hard) the exercise is, with gentle exercise causing only slight increases in breathing and heart rate, but more vigorous exercise resulting in greater increases.

Aerobic versus anaerobic exercise

The term ‘aerobic exercise’ comes from the fact that the energy used during this form of exercise is linked to the consumption of oxygen (aerobic metabolism). Aerobic exercise is of a light to moderate intensity, and is characterised by our ability to maintain it for a prolonged duration (many minutes to several hours).

Very strenuous exercise, such as running fast or rapidly cycling uphill uses energy at a very fast rate, and will exceed our muscles’ capacity to work aerobically. Exercise at these higher intensities does involve the use of oxygen, but also requires your muscles to undertake some additional metabolism without oxygen (anaerobic metabolism). This anaerobic metabolism results in the production of fatiguing factors that cause you to have to slow down and eventually stop. The length of time before this occurs will depend on how much anaerobic metabolism is involved, with higher exercise intensities that require greater anaerobic metabolism causing fatigue to occur more quickly.

How often should I do aerobic exercise?

For general health and fitness benefits, such as reducing your risk of heart disease and improving your stamina, it is recommended that you do some form of moderate intensity aerobic exercise on most, and preferably all, days of the week, for a minimum of 30 minutes a day. This 30-minute total can be made up of shorter 10-minute sessions, if this is better suited to your day. These short sessions will still provide health benefits and produce some fitness improvements, although to substantially increase your fitness you probably need to include at least some 30-minute sessions in your week.

To maintain your level of aerobic fitness, and the health advantages that go with it, you need to keep up a regular aerobic exercise routine. Giving up your routine or doing less exercise will cause your fitness and associated health benefits to decline.

It’s also important to avoid prolonged sedentary behaviour, such as sitting continuously for several hours. So, in addition to trying to incorporate exercise into your day, you should also try to break up your sedentary behaviours, for example by getting up and walking around your office for a few minutes every hour, or during the advertisement breaks when watching TV.

How hard should I do aerobic exercise?

To improve your general health and fitness, moderate intensity aerobic exercise is recommended. However, if you are very unfit and currently do no exercise, even short bouts of light exercise will be of benefit. With continued participation, this light exercise will produce fitness improvements that will enable you to progress to moderate intensity exercise.

As a general guide, ‘moderate intensity’ aerobic exercise may make you slightly breathless, but still able to hold a conversation, and you should be able to sustain this level of exercise for at least 30 minutes. An example would be when going on a brisk walk, jog or bike ride with a friend.

If you want to be more exact in determining your exercise intensity, then you can use your heart rate as a guide. Moderate intensity exercise is likely to increase your heart rate to between 55 and 70 per cent of your maximum heart rate. More vigorous exercise will increase your heart rate even further.

How to estimate your maximum heart rate

How to estimate your maximum heart rate

Your maximum heart rate in beats per minute = approx 220 minus your age

But this is a rough estimate, and there is a lot of individual variation. (Your maximum heart rate tends to decline by about 1 beat per year with increasing age.)

You can estimate your maximum heart rate by subtracting your age in years from 220. For someone who is 40, for example, their maximum heart rate would be estimated to be around 220 minus 40, which is 180 beats per minute. So, during moderate intensity exercise, this person could expect to have a heart rate between 99 and 126 beats per minute (55 to 70 per cent of their maximum heart rate). However, this is just a rough estimate, and some people can have maximum heart rates more than 20 beats above or below that estimated for their age. So it’s a good idea to also use your perception of how hard the exercise is — the guide of being slightly breathless but able to hold a conversation is a good one.

Beta-blockers and exercise

Beta-blockers are one type of medicine used to lower blood pressure as well as treat angina and certain heart rhythm disorders. They work by slowing down the rate at which the heart beats. People taking beta blockers should talk to their doctor about their planned exercise programme. Moderate intensity exercise is often recommended for people taking beta-blockers, but since the heart rate calculations described above do not apply to them, the best guide to determining a suitable exercise intensity is their perceived exertion.

Measuring your heart rate

If you do not possess a heart rate monitor, an easy way to measure your heart rate is to count your pulse for 10 seconds then multiply this count by 6 to calculate your heart rate per minute. To find your pulse, locate either your carotid artery (found on the side of your neck, just under your jaw bone) or your radial artery (in your wrist at the base of your thumb). Then gently place your index and middle fingers over the artery, but don’t press too hard or you will stop the flow of blood in that artery and not be able to detect a pulse.

Be aware that aiming for a target heart rate when exercising is a rough guide and may not work for some people. Older people who are physically fit may have a higher maximum heart rate than a younger, less fit person, and a higher maximum heart rate than that given by subtracting their age from 220.

Progressing to greater levels of fitness

If you are already active and getting 150 minutes of moderate intensity exercise a week but want to attain a higher level of health and fitness, you will need to increase your aerobic exercise levels, either by exercising at a higher intensity and/or by doing more exercise.

Vigorous aerobic exercise — exercising at 70 to 85 per cent of your maximum heart rate — will result in further fitness and health gains. As a guide, at this intensity you will be breathing hard and finding it difficult to talk in full sentences between breaths. This level of exercise is more strenuous and should only be contemplated if you are already accustomed to regular moderate intensity aerobic exercise. To prevent ‘overdoing it’, it is a good idea to alternate between moderate and vigorous exercise days with, for example, 30 or more minutes of vigorous aerobic exercise on 3 or 4 days a week, interspersed with days of 30-60 minutes of moderate intensity aerobic exercise.

For people undertaking high-level sports training, a qualified trainer is likely to develop an individualised programme that varies from the above guidelines with regard to the intensity (how hard), the duration (how long) and the frequency (how often) of the aerobic exercise sessions. This is because the main aim of their training is to improve their sporting performance - the associated health benefits that accompany this are a fortunate side benefit, rather than the main goal.

A balanced fitness programme

For people of all fitness levels, aerobic exercise should form part of a balanced exercise programme that also includes 2 to 3 sessions per week of exercise to increase muscle strength, e.g. resistance training; and some stretching and flexibility work, e.g. a basic stretching routine or attending a yoga class. Needless to say, healthy eating and plenty of rest will complete a well-rounded fitness programme.

Aerobic exercise precautions

Appropriate aerobic exercise is recommended for almost everybody, regardless of age, but may need to be modified to ensure its suitability for people with existing health problems.

If you have existing health problems, are at high risk of cardiovascular disease, or have muscle, bone or joint injuries, check with your doctor before undertaking an aerobic exercise programme. Also, men aged over 40 years and women aged over 50 years who have not exercised regularly in the recent past should check with a doctor before undertaking a programme of vigorous physical activity. The level and type of exercise may be adjusted to ensure that it can be undertaken safely and effectively.

As with any form of exercise, be aware of over-exercising, either by doing aerobic exercise too hard, for too long or too often. This approach can lead to injury and abandonment of your fitness programme. Remember to build up gradually from your current activity level, and not to progress too rapidly. If you are new to regular aerobic exercise, several weeks of low to moderate intensity aerobic exercise are usually advised before introducing more vigorous aerobic exercise sessions. When you do increase your level of aerobic exercise, increase only one component — the intensity, duration, or frequency of your aerobic exercise sessions — at a time.

It’s never too late to start

An important health and fitness message is that people of all ages can benefit from regular aerobic exercise. And, if you are unfit, unhealthy or an older adult, you may have the most to gain from including it in your lifestyle.

Last Reviewed: 24 March 2015
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