Common exercise myths busted

There’s a lot of misleading information about exercise — we take a look at fitness facts and fictions
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03.How much and how often?

Myth: "Exercising three times a week is enough."

There’s a lot of conflicting advice about the amount of exercise you need to do to get results, ranging from ‘anything is better than nothing’ to ‘over an hour a day, every day’. There’s a bit of truth in both extremes, and everything in between, though it also depends on what you mean by ‘get results’. For example:

  • If you go for a 30 to 40-minute brisk walk, you can temporarily reduce blood sugar, triglycerides and blood pressure levels. So in that sense, just one session can have a benefit.
  • People who’ve lost a great deal of weight (20kg or more) seem to require one hour to 90 minutes of moderate to vigorous exercise every day to maintain that weight loss.

The current Federal Government National Physical Activity Guidelines for Australians recommend that, for good health, adults exercise for a total of 30 minutes or more on most, preferably all days. The 30 minutes can comprise several sessions of at least 10 minutes each. The activity should be strenuous enough to raise your heart rate and rate of breathing. You should be able to talk, but not sing.

For greater health and fitness benefits, the guidelines recommend three or four sessions of vigorous exercise each week, for at least 30 minutes each time, in addition to the moderate exercise listed above. Exercise should be continuous, and hard enough to make you puff — where it’s difficult to talk in full sentences without taking a breath. Your heart rate should be about 70–85% of its maximum (which is 220 beats per minute, minus your age).

Finally, for good all-round physical health, you might consider including two or three resistance or strength training (weightlifting) sessions per week, as well as a flexibility and balance program (such as yoga or Pilates, or even just some gentle stretching), in your exercise routine.

Bottom line:

Anything is better than nothing, but for good health, do moderate exercise totalling at least 30 minutes a day, on five or more days a week.

Myth: "I just ate a 300 calorie chocolate bar. Walking burns 300 calories per hour, so if I walk for about an hour, I’ll burn off the chocolate." Couple running on beach

If you look up most exercise and calorie tables, they’ll tell you that a 68kg person walking for one hour at a moderate speed of 5 to 6km/h burns between 250 and 300 calories. They don’t usually remind you that by sitting around doing nothing or pottering about, you’d also burn some calories — maybe up to 140. In other words, they give ‘gross’ calorie expenditure per unit of time, not ‘net’ calories (the amount above and beyond what you’d normally expend).

Now assuming the chocolate is surplus to your daily energy needs, and you want to burn off an extra 300 calories, you’ll need to do 300 ‘net’ calories of exercise. Researchers have worked out that the net calories burned walking in this situation would be about 180 calories per hour. This means more than 1.5 hours of walking to burn off the chocolate . And eating it took you … how long?

Bottom line:

 Calculating energy expenditure based on gross, rather than net calorie burn overestimates the contribution of exercise to total daily expenditure.

Myth: "I’m slim and healthy, I don’t need to exercise."

Even if you’re slim and seem to be healthy, you’re probably not as healthy as you could be if you are inactive. Furthermore, studies have found that people who are ‘fat and fit’ — that is, who are overweight but do regular exercise — are healthier than people who don’t exercise, and therefore likely to live longer.

Meeting the minimum exercise recommendations can go a long way to achieving good health. Benefits include:

  • Normal blood pressure.
  • Healthy cholesterol levels.
  • Lower levels of anxiety and depression.
  • Stronger bones and better balance (particularly important for older people otherwise at risk of osteoporosis).
  • Weight management.
  • Good cardio-respiratory fitness, muscular strength and flexibility.
  • General self-esteem and psychological wellbeing.

Bottom line:

 Exercise contributes to good overall physical and mental health — it’s not just about body weight.


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