Swimming is often touted as the best form of exercise for weight loss. And when you think about it, it seems to make sense.
After all, swimming uses almost all of your major muscle groups. It places a vigorous demand on your heart and lungs. Swimming is also popular with people who are extremely overweight, pregnant, or suffering from some kind of injury.
When you swim breastroke or backstroke, you're burning about the same number of calories as a fast walk or a slow jog. However, for some reason, swimming appears to be less effective than other forms of exercise at promoting weight loss.
Swimming weight loss
Research published in the American Journal of Sports Medicine shows that in the absence of a controlled diet, swimming has little or no effect on weight loss [1].
Professor Grant Gwinup compared three exercise programs for three months. Each program began with up to 10 minutes of daily exercise. The length of each workout was increased by five minutes every week.
• Test subjects following the walking program lost 17 pounds of weight during the three-month study.
• Those following the cycling program lost 19 pounds of weight.
• However, subjects following the swimming program actually gained 5 pounds.
Assuming that all three groups burned a similar number of calories, the swimmers must have compensated by eating more. "Presumably," speculates Professor Gwinup, "swimming in cold water stimulates the appetite to increase caloric consumption."
Professor Louise Burke, Head of Nutrition at the Australian Institute of Sport, also points out that competitive swimmers typically have body fat levels that are higher than those of runners or cyclists who expend a similar amount of energy when they train.
"Many female swimmers have fought well-publicized battles with their body fat levels," says Burke. "They are generally prescribed 'land training' (running or cycling) in addition to their many laps of the pool in the belief that it is a necessary treatment to produce lower skinfold levels."
Appetite
There are suggestions that swimming doesn't cause the same drop in appetite that accompanies heavy running and cycling training. Many people feel extremely hungry after training in the pool, and may simply replace all the calories they've burned with a large post-exercise meal.
"Many people observe that they feel like 'eating a horse' after they have finished a swim training session, and may overcompensate for the energy they have just burned," says Professor Burke.
"Some research suggests that this is due to the cool temperatures in which swimmers train. By contrast, runners and cyclists usually experience an increase in body temperature during training, which may serve to suppress appetite - at least in the short term."
In one recent study, researchers examined the effect of water temperature on calorie intake after exercise [3].
A group of 11 men exercised for 45 minutes in "neutral" and "cold" water temperatures. After the workout, they were allowed to eat as much food as they wanted.
The men burned a similar number of calories in the cold and neutral water conditions, averaging 505 and 517 calories, respectively. However, calorie intake after exercise in the cold water averaged 877 calories, which was 44% more than for the neutral temperature. The problem here is that the water temperature during the "cold" condition was extremely cold (20 degrees celsius), and isn't really indicative of the water temperature of most pools (which is usually nearer 30 degrees celsius).
Professor Burke also points out that swimmers are less active outside their training sessions. They are so tired from the hours spent training that they sleep, sit or otherwise avoid any real physical activity outside their sessions.
In one study, researchers compared collegiate swimmers and collegiate distance runners [2]. As you can see in the table below, the runners had lower body fat levels than swimmers. However, detailed three-day food records and one-day activity records offered no convincing explanation as to why.
Swimmers Runners
Men 12% 7%
Women 20% 15%
According to Professor Burke, it's almost impossible to measure usual energy intake from diaries.
"Apart from the errors in translating descriptions of food into calorie counts," she says, "it is unlikely that people eat 'normally' while they are recording. It is well-known that those who are conscious of their body fat underreport their food intake."
"In reporting, athletes try to appear as 'good' as possible and thereby cover-up the clues to any energy balance problems. The behavior of individuals may also be masked by the 'averaging' of results."
Burke also speculates that elite swimmers are predisposed to higher body fat levels because it is a help, or at least less of a disadvantage, to their swimming - rounded shoulders and smooth curves may simply be more biomechanically sound than bony angles.
Muscle
One of the reasons a properly designed weight-training program is so effective at burning fat is that just one workout can give your metabolic rate a real boost. In some cases, this rise can last for well over a day [4].
When your metabolic rate goes up, you burn more calories. And more calories burned means faster weight loss.
One of the things that contribute to this rise in metabolic rate is the muscle damage caused during resistance exercise [5]. And it's eccentric muscle actions (pronounced ee-sen-trick) that appear to cause most of this damage.
What's an eccentric muscle action?
Take one hand and let it hang down by your side. Now, bend your arm as if you were curling a weight, bringing your hand towards your shoulder.
The muscle that's working to raise your arm is the biceps (other smaller muscles are also working to assist it). The movement is known as a concentric muscle action (pronounced con-sen-trick).
If you lower your arm under control (rather than just letting it flop down) your biceps are working again. Only this time, the muscle action is called eccentric.
So, what does all of this have to do with swimming? Most of the work your body does in the water involves concentric muscle actions. There's virtually no eccentric work there at all. Because of this, I'm guessing that swimming has only a minor impact on your metabolic rate after exercise.
The bottom line
I prefer to put all forms of exercise into one of three categories - good, better or best.
Any form of exercise, be it swimming, walking or weight-training, is good if the alternative is doing nothing. A mixture of some form of resistance exercise and cardiovascular exercise is better, while combining interval exercise and free weights - in my opinion at least - is the best way to get in shape (see Burn The Fat Feed The Muscle for an example of a highly effective weight loss program).
Losing weight is all about burning more calories than you eat. Any form of exercise, swimming included, will get the job done.
If you enjoy swimming, then stick with it. It's more important to be consistent with an exercise program you enjoy than to be inconsistent with one you hate. Just make sure to guard against the urge to eat more after you get out of the pool.
References
2. Jang, K.T., Flynn, M.G., Costill, D.L., Kirwan, J.P., Houmard, J.A., Mitchell, J.B., & D'Acquisto, L.J. (1987). Energy balance in competitive swimmers and runners. Journal of Swimming Research,
3, 19-233. White, L.J., Dressendorfer, R.H., Holland, E., McCoy, S.C., & Ferguson, M.A. (2005). Increased caloric intake soon after exercise in cold water. International Journal of Sport Nutrition and Exercise Metabolism, 15
4. Schuenke, M.D., Mikat, R.P., & McBride, J.M. (2002). Effect of an acute period of resistance exercise on excess post-exercise oxygen consumption: implications for body mass management.
European Journal of Applied Physiology, 86, 411-417
5. Dolezal, B.A., Potteiger, J.A., Jacobsen, D.J., & Benedict, S.H. (2000). Muscle damage and resting metabolic rate after acute resistance exercise with an eccentric overload.
Medicine and Science in Sports and Exercise, 32, 1202-1207
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