Exercise is Medicine: The Recommended Dose of Activity for Better Health

Summary of article

If you aren’t currently physically active, simply getting started can improve your health
If you can, aim to meet or exceed the physical activity guidelines published by the World Health Organisation
The intensity of an activity is an important factor in determining if you are meeting or exceeding the physical activity guidelines

Article

As outlined here, being regularly physically active is a great way to improve your health. But, how much activity do you need to do to gain those benefits? What types of activity do you need to do? How hard do you need to work? The answers to these questions are outlined below.

How Much Physical Activity is Recommended

The World Health Organisation (WHO) lays out its recommendations for physical activity (and sedentary behaviour) this document. These recommendations draw upon the same research that inform the national physical activity guidelines of different countries, and therefore the recommendations are broadly very similar.

The WHO Guidelines on Physical Activity and Sedentary Behaviour contain recommendations for different groups including:

Children and adolescents (aged 5 – 17)
Adults (aged 18 – 64)
Older adults (aged over 65)
Pregnant and postpartum women
Adults and older adults with chronic conditions (aged over 18)
Children and adolescents (aged 5-17) and adults (aged over 18) living with disability

The main physical activity recommendations from the WHO guideline are summarised below:

Children and adolescents (aged 5 – 17):

At least 60 minutes of moderate intensity cardiovascular activity each day,
AND vigorous intensity aerobic activity on at least 3 days a week,
AND strengthening activity on at least 3 days a week (1).

Adults (aged 18-64):

At least 150-300 minutes of moderate intensity cardiovascular activity each week,
OR at least 75-150 minutes of vigorous intensity cardiovascular activity each week,
OR an equivalent combination of moderate and vigorous intensity cardiovascular activity,
AND strengthening activity on at least 2 days a week (1).

Older adults (aged over 65):

At least 150-300 minutes of moderate intensity cardiovascular activity each week,
OR at least 75-150 minutes of vigorous intensity cardiovascular activity each week,
OR an equivalent combination of moderate and vigorous intensity cardiovascular activity,
AND strengthening activity on at least 3 days a week,
AND balance activity on at least 3 days a week (1).

Pregnant and post-partum women:

At least 150 minutes of moderate intensity cardiovascular activity each week,
AND a variety of muscle strengthening activities,
AND daily pelvic floor exercise (1).

The recommendations for adults with chronic conditions, and children and adults with disabilities, are effectively the same as for those without chronic conditions or disabilities.

Cardiovascular Activity

Cardiovascular activities challenge the circulatory system (heart and blood vessels) and respiratory system (lungs and airways) to sustain movement (1). Examples include walking, running, swimming, cycling, rowing, and playing football and tennis.

Strengthening Activity

Strengthening activities challenge the muscles to produce force (1). Examples include resistance training (eg. traditional gym-based exercise), calisthenics (ie. bodyweight strength exercises), and weightlifting (the snatch and clean and jerk). The major muscle groups to be worked in a bout of strength activity include muscles of the legs, back, abdomen, chest, and shoulders.

The WHO guidelines don’t explicitly state the volume (amount) of exercise that is needed to meet the minimum requirements. However, the research that informs these recommendations typically includes performing 2-4 sets of 6-15 repetitions for each exercise (2,3).

Balance Activity

Balance activities challenge the body’s ability maintain the desired posture or position statically, during movement, or withstanding perturbations from the external environment (1). Examples include dancing, tai chi, standing on one leg, and coordination exercises.

Again, the WHO guidelines don’t explicitly state the volume of balance exercise that is needed to meet these minimum requirements, and there is a lot of variation in the studies underlying the recommendations (4). However, some of these studies demonstrate benefit from completing as little as 42 minutes of balance activity a week (5). This equates to 14 minutes, 3 times a week. This may, therefore, be seen as an appropriate minimally effective dose.

Pelvic Floor Exercise

Pelvic floor exercises involve the voluntary contraction and relaxation of the pelvic floor muscles that are responsible for, among other things, controlling bowel and bladder function (6).

A recommended dose for pelvic floor exercise is 8-10 near maximal contractions, where each held for 6-8 seconds, 2-3 times a day (7).

The Recommended Intensity of Activity

Like with most things, there is a goldilocks zone when it comes to the intensity of physical activity. If your activity is too low in intensity (for example, if the only walking you do is when you stroll the aisles of the supermarket), it will not cause your body to make the positive adaptations necessary for improved health and fitness. If your activity is always performed at very high intensity (for example, every time you go to the gym you attempt to lift the heaviest weight possible), you run the risk of injury. The recommended intensities for cardiovascular, strengthening, and balance activities are outlined below.

Intensity for Cardiovascular Activity

The WHO Guidelines make recommendations for activity that is either “moderate intensity” or “vigorous intensity”. The table below outlines how these descriptors relate to other measures of intensity for cardiovascular activity:

You can calculate your predicted maximum heart rate with the formula:

HRmax = 208 – (0.7 x age) (9)

For example, for a 35 year old, predicted maximum heart rate can be calculated as follows:

HRmax = 208 – (0.7 x 35) = 208 – 24.5 = 183.5

As with all things, the calculations to predict your maximum heart rate, and percentage of maximum heart rate to achieve the desired training intensity, are based on averages. Your actual maximum heart rate, and response to different training intensities, might differ from those indicated above.

Intensity for Strengthening Activity

The WHO Guidelines recommend that strength exercises be completed at a moderate or greater intensity. The table below outlines how this descriptor relates to other measures of intensity for strength exercise:

In strength exercise, RPE is often defined as being an inverse of the Repetitions In Reserve (RIR) scale. The RIR scale is what it sounds like: it represents the number of additional repetitions that could have been completed for an exercise. For example, if you complete a set of deadlifts and feel you could have done another 3 repetitions, that represents in intensity of 3 RIR. The other way of stating this would be to say the intensity was RPE 7.

Applying this measure of intensity to the guideline recommendations, this means that strengthening exercises should be sufficiently hard that at the end of each set it should not feel like you could complete more than 5 additional repetitions. If, for example, you do a set of 10 squats, and feel you could immediately do another set of 10 without a rest, this represents an intensity that is too low. In this example you would need to either add repetitions, add a weight, or otherwise change the exercise to increase the intensity.

At the other end of the spectrum, it is generally recommended to not always exercise at a maximal intensity. If at the end of each set you feel that you could not have done another repetition, you may need to decrease the number of repetitions you are performing, reduce the weight, or select a less intense exercise.

In strength exercise, a 1 Repetition Maximum refers to the heaviest weight that could be lifted for a single repetition. The table above indicates the relationship between RPE, RIR and %1RM assuming a single repetition was being completed. For example, if your Barbell Deadlift 1RM is 100kg, and you complete a single repetition at 85kg, this would represent an RPE 4, or 6 RIR.

Building on the relationship between RPE and %1RM, the below table outlines this relationship for different numbers of repetitions (10):

Using this table, you can see that completing a set of 10 repetitions of an exercise with 70% of your 1RM would result in an intensity of RPE 5. It’s worth noting that people can vary widely in terms of the number of repetitions that they can complete at a given %1RM. The table above represents the average, and your experience might be quite different.

Intensity for Balance Activity

As with strength exercise, the WHO guidelines recommend balance exercises be completed at a moderate or greater intensity. However, compared to cardiovascular exercise and strength exercise there has not been as much research conducted that demonstrates clearly how to assess balance exercise intensity, and the ideal intensity that the exercise should be completed at to elicit improvements. As such, the information in the table below is based on much less data than those in the previous sections, and should be viewed in that context (11):

In Summary

For people who are not currently active, simply getting started has benefits. However, for those who can, meeting the guidelines listed above can result in substantial health improvements. When working to meet the guidelines, it is important to aim towards a target intensity. Undershooting the recommended intensity can result in fewer health benefits being accrued, while consistently working at a maximal intensity increases the risk of injury.

References

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