Is Exercise Bad For You?

Is intense exercise hard on the immune system?

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You go to the gym, you huff, you puff, but you don't feel any better. You finish your session looking like a sweaty beetroot, go home and collapse on the couch. Isn't this supposed to be doing you good??? Depends how hard you exercise - this could answer your question...

Does exercise, help, hurt or have no effect on the immune system? Experts have debated that question over the last few years with no firm answers. Some fitness advocates claim that regular training improves resistance to infections and prevents tumour growth, yet athletes and coaches often report that strenuous training actually seems to produce a higher risk of respiratory infections. Published studies have shown that marathon runners have a much higher than normal chance of developing a cold during the week after a marathon, suggesting that vigorous exercise may open the door for opportunistic pathogens.

The final word on the link between exercise and health is not in yet, but there's now evidence that exercise intensity may be a key factor. Specifically, new research from Denmark suggests that light to moderate exercise boosts immune-system activity, while intense exercise may depress it.

The Bodydoctor Personal Fitness Training Programme offers a sensible approach to fitness and weight Loss. Combining exercise and nutrition its available as a Fitness Book and DVD.

In the Danish research, six healthy individuals exercised on a bicycle for one hour on three different occasions, separated by two-week intervals. In one instance, the subjects cycled at a low intensity of only 25% V02max (just 45-50 per cent of maximal heart rate). On the other occasions they pedalled at either a moderate intensity of 50% V02max (65 per cent of maximal heart rate) or a relatively high intensity of 75% V02max (84 per cent of max heart rate). After each ride, immune-system status was evaluated.

The most dramatic changes in immune-system activity occurred after the high-intensity ride. Blood concentrations of monocytes - a type of white blood cell - were above normal, but the activities of two key types of white cells which destroy invading pathogens - natural killer (NK) cells and Iymphokine-activated killer (LAK) cells - were suppressed following the high-intensity exertions. The Danish researchers suggested that the surplus monocytes which appeared during and after the high-intensity ride released chemicals called prostaglandins which inhibited NK- and LAK-cell activity. That's an undesirable response, single immune-system strength declines as NK and LAK activity ebbs.

Meanwhile, concentrations of white blood cells increased during both light and moderate exercise, as did NK cell activity, and there was no suppression of NK cells. The Danish researchers concluded that light and moderate exercise tends to boost the immune system, while intense exercise has some potentially negative effects.

The Danish cyclists were previously untrained, but the strong observed link between hard training or racing and illness suggests that the relationship holds for more experienced athletes, too. It's apparent that sports-active people should consider cutting back on their high intensity training at times when the risk of infection is high (for example, in the winter, when athletes tend to be cooped up with lots of coughing, sniffing people). In addition, when athletes are under increased physical or emotional stress or are getting less rest and sleep than usual, it makes sense for them to temporarily bias their training towards moderate- or low-intensity efforts in order to lower the risk of illness.

("The Effect of Light, Moderate and Severe Bicycle Exercise on Lymphocyte Subsets, Natural and Lymphokine Activated Killer Cells, Lymphocyte Proliferation Response and Interleukin 2 Production". International Journal of Sports Medicine, vol 14(5), pp 275-282, 1993)

Exercising at the correct intensity which is beneficial to the immune system is a fundamental part of the Bodydoctor programme. Order the Bodydoctor fitness book.