How Much Exercise Should I Be Doing?
“How much should I exercise?”
This is a question I have had a few times recently.
It’s a tricky one to answer but here I go…
A reasonably trustworthy and reliable rule of thumb is to try to follow the national guidelines for physical activity.
Frequency: Adults should be active most days, preferably every day.
Duration:
Moderate-intensity activity: 150–300 minutes per week (e.g., brisk walking, swimming).
Vigorous-intensity activity: 75–150 minutes per week (e.g., jogging, aerobics).
Or an equivalent combination of both.
Muscle-strengthening: Include activities that strengthen muscles on at least 2 days per week (e.g., push-ups, squats, lifting weights).
Sedentary behaviour: Minimise prolonged sitting and break up long periods of sitting whenever possible.
Key principle: Doing any physical activity is better than doing none. Start small and build up gradually.
Guidelines for older adults (65 years and older)
Frequency: Be active every day in as many ways as possible.
Duration:
Aim for at least 30 minutes of moderate-intensity physical activity on most, preferably all, days (e.g., brisk walking, swimming, cycling).
If 30 minutes is challenging, start with shorter sessions (e.g., 10 minutes) and build up gradually.
Types of Activities:
Fitness (Cardio): Activities that improve heart, lungs, and circulation (e.g., walking, water aerobics).
Strength: Include muscle-strengthening activities at least 2–3 times per week (e.g., resistance training, lifting groceries).
Flexibility: Stretch daily to maintain mobility.
Balance: Incorporate exercises like Tai Chi or simple balance drills to reduce fall risk.
Sedentary Behaviour: Minimise sitting time and break up long periods of inactivity.
Key Principle: Any activity is better than none. Start small and progress gradually.
How are these guidelines determined?
Hint: It’s not a strictly objective science. Sorry if that disappoints you.
Anyway, here’s how it’s done.
Panels of subject matter experts review the scientific literature on the effect of exercise on health. One of the things they are looking for is the “minimum effective dose”. That is, the minimum amount of exercise which yields a substantial health improvement.
In the Australian and American physical activity guidelines, it is recommended that adults do 150 minutes of moderate intensity exercise or 75 minutes of vigorous exercise per week, as a minimum. Additionally, twice weekly strengthening exercises of the major muscle groups is recommended.
Why that much? Why not more (or less)?
According to this article at Harvard Medical School, 150 minutes of cardio could repeatedly be seen to the minimum effective dose for yielding substantial health improvement in areas like chronic disease (e.g. diabetes, cardiovascular disease), cancer and weight management.
The twice-weekly muscle strengthening frequency is recommended for similar reasons. This amount is thought to be effective at producing substantial health improvement, although anything is much better than nothing (in case you’re wondering if it’s worth doing one session of strengthening per week or fortnight).
So, achieving the guideline amounts is a great start. But for many people, this is not easy. Life can override your new year’s resolutions pretty swiftly. Deadlines loom. Peak winter hits, and the call of the couch becomes irresistible.
Can we trust the subject experts on this?
Yes you can. That’s because exercise the closest thing we have to a silver bullet for health. It is almost universally beneficial for everyone. Side effects are rare and minor. Even if the experts are off in terms of the quantity they are recommending, you can bank on these things:
most people are not exercising enough (probably including you)
most people will benefit a lot from doing more (if it is realistic for them)
people occasionally do too much but this is rare and relatively easy to identify
the experts are incentivised to understate how much is needed in order to benefit you, because they want to make it realistically achievable to meet the guidelines
If I can’t meet the guidelines, is it worth bothering at all?
Yes, very much so.
An important thing to understand is that health benefits flow from exercise in a non-linear, dose dependant way.
Here’s what I mean:
Non-linear = once you go from nothing to something small, you get a big, big benefit: a steep increase in benefit for only increasing your activity by a little bit. Then, the more you do, the more the improvement curve flattens out. You get less and less from doing more and more. The benefit keeps going up but you need to exert more and more effort (time & energy) to get greater improvement.
Dose dependant = the more you do, the more you benefit. You increase your cardio fitness if you spend more time running, swimming, walking or cycling. You gain more muscle if you increase the weight you lift. I’m making generalisations but you get the gist. A higher dose of exercise (in terms of duration and intensity) yields more health benefit.
Grasping this is important for the person who thinks that there’s no point exercising if they can’t do a lot. Such a person will certainly benefit from increasing their activity. There is no minimum threshold of exercise for gaining benefit.
But there’s an important caveat here. At some point, if you keep increasing the dose, you’ll poison yourself. You will be exercising so much that it will be BAD for your health - making you sick or injured.
In summary, the health response to exercise is non-linear and dose dependant until the medicine becomes poison and the curve slopes downwards. Health improvement becomes health decline when you overtrain the human body.
What are the key takeaways?
1/ Striving to achieve the physical activity guidelines is an excellent goal for most people
2/ You get the biggest bang for your buck going from nothing to something
3/ If you want more and more health benefit, increase the dose, but not so far that the medicine becomes poison
How do I know when I reach that point? (The point where the medicine becomes poison).
Well, here’s some ideas. This is not an exhaustive list, but these symptoms typically occur if you’re overtraining:
diminished sleep quality and duration
loss of motivation
low mood and libido
elevated susceptibility to injury
long-standing intractable muscle soreness
irritability and unusual anger
dysregulated appetite (loss or gain)
What would this look like?
Here are two scenarios. One for a white collar worker, and another for a blue collar worker.
WHITE COLLAR
Monday - 30 minute brisk walk during lunch and 45 minutes at the gym (strengthening) on the way home from work.
Tuesday - 30 minutes brisk walk before work
Wednesday - Ride to work and back (Total ride time = 1 hour)
Thursday - Rest
Friday - 30 minutes of lap swimming
Saturday - some jobs and errands
Sunday - 15 minute jog and 30 minute home-based weights circuit
BLUE COLLAR
Typically people are on their feet a lot, and doing long duration low-to-moderate intensity movement. They are physically drained by the end of the day which makes structured exercise a challenge. Counterintuitively, trades people and manual workers don’t get all the exercise they need from their work, even though they may utilise a lot of energy during the day. The prevalence of musculoskeletal injury in heavy labouring jobs means strength training is especially important. What’s more, their jobs rarely involve any high intensity activity. Also, the hours and the food environment can be uniquely detrimental for health, which is one reason why overweight and obesity are ubiquitous in blue collar settings.
Monday - gym on the way home from work (machine based strength training - because you can sit down on the machines which makes it easier to get motivated)
Tuesday - 45 minute brisk walk before work
Wednesday - 20-minute weights circuit before work
Thursday - Social touch rugby match (use team sport to help you to stay motivated)
Friday - Rest day
Saturday - 10-20 mins High Intensity Interval Training HIIT on a rowing machine or exercise bike then strength training session
Sunday - 90 minute walk on alternate weeks