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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  • Updated:2 Sep 2007

04.Walk, run or swim?

Myth: "Walking one kilometre burns the same calories as running one kilometre."

What’s amazing about this myth is that it has persisted for so long. Scientists have known for years that it’s not true, but you’ll still hear it touted as fact by any number of health and fitness industry professionals. It even features on lists of exercise myths — except that the ‘myth’ is that 'running a mile burns more calories than walking a mile' .

Walking is an extremely efficient way for humans to move around. With straight-ish legs and a reasonably level centre of gravity, you’re bit like a bunch of swinging pendulums with good momentum, especially when you include your arms. Running requires a lot more energy than walking: you’re effectively jumping from one foot to the other, raising and lowering your centre of gravity far more than walking. Think more like a bouncing ball than pendulums.

In fact, running consumes around 40 to 50% more gross calories, or twice as many net calories (see the 'walking-off-a-chocolate-bar' myth for the difference between net and gross calories) per kilometre than walking — at least up to a certain walking speed.

At speeds over 8km per hour, walking burns more calories than running at the same speed because it’s more inefficient and difficult.
If speed’s not your thing, the good news is that it doesn’t matter how fast you run: it’s the distance that matters. So, running a kilometre fast burns as many calories as running a kilometre slowly.

However, given that running burns two times as many net calories per kilometre as walking in a given amount of time, that means if you run twice as fast as you walk, you’ll get twice as far and therefore burn four times as many net calories. The Straight Dope presents a fun discussion of running versus walking.

Bottom line:

Running burns twice as many net calories per kilometre as walking.

Myth: "Swimming isn’t a good way to lose weight." Man in swimming pool

Media reports in recent years have turned the received wisdom — that swimming is great for heavy people who want to lose weight — on its head. We’re now told studies have found that people who swim for exercise don’t lose weight or even (shudder) gain weight.

There are several possible explanations for these findings. One study found that swimmers gained weight (though not a significant amount) while walkers and cyclists lost weight. Calories weren’t restricted (so the swimmers may have eaten more) and exercise intensity wasn’t monitored or controlled. This one study seems to be cited over and over again, giving the impression that the evidence is based on lots of different sources.

Another study found that people who exercised in cold (20°C) water ate more afterwards than people who exercised in neutral (33°C) water. So swimming in cold water may indeed stimulate the appetite, which may result in weight gain if calories aren’t restricted. If you swim pretty slowly — essentially floating, with minimal propulsion — you’re likely to expend less effort than if walking or cycling. Swimming without changing calorie intake might mean that you’re building muscle and losing fat, so your weight may not change much — though your clothes may become looser.

Finally, you might get tired out from swimming and laze around the rest of the day. Improving your ‘efficiency’, through stroke correction lessons, say, can help prevent strains, injuries and fatigue caused by poor technique. If you’re very heavy, swimming can be a great way to start exercising, because your weight is supported and it works all parts of the body (especially if you include some work with a kickboard and flippers). It’s possible to lose as much weight swimming as walking or cycling — you just have to do it fast enough (you might need to take your pulse regularly to help you determine how hard you’re working ).

Bottom line:

Swimming can help you lose weight, as long as you go fast enough and long enough. Just watch your diet as well.


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