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Height hits economy
Speaking of economy, mum probably didn't mention that the taller you are, the more miserable (that's miserable, not miserly) is your economy. But - it's true. As height increases, it costs more to run at a particular pace, even when the cost is expressed per kilogram of body weight. Research in France bears this out ('Influence of Training, Sex, Age, and Body Mass on the Energy Cost of Running,' European Journal of Applied Physiology, vol. 66(5), pp. 439-444, 1993).

Why would that be true? Analyzing the situation, mum used to like to say that bone mass increases exponentially, not linearly, as a function of height, which means that taller runners have both absolutely and relatively heavier bones, compared to shorties. It costs energy to lug those bones around, so economy dips. Small wonder that the majority of world-class marathoners tend to be relatively slight figures. Of course, lack of economy doesn't faze sprinters, the best of whom tend to be fairly tall. Their goal in running is to maximize power, not worry about saving a millilitre of oxygen here and there, and power maximization tends to mean long limbs and rippling muscles.


A run a day keeps the doctor away?
You probably did know that the risk of illness tends to increase as training volume mounts ('Infectious Diseases in Athletes: New Interest for an Old Problem,' Journal of Sports Medicine and Physical Fitness, vol. 34, pp. 11-21, 1994). For example, famed American marathoner Alberto Salazar developed 12 colds in 12 months while overtraining for the 1984 Olympic Marathon, in which he performed poorly (the average adult contracts 'only' two to three colds per year). 'My immune system was totally shot as a result of my training,' says Salazar. Many other athletes, including Liz McColgan and Uta Pippig, have noticed a strong connection between high-volume training and illness, and the most common medical problem for athletes at both the Winter and Summer Olympic Games is not strained ligaments or sprained tendons; it's the upper-respiratory-tract infection (aka the common cold).

However, you probably weren't aware that a single, rugged test of endurance can also markedly increase your chances of getting sick. Research carried out in South Africa has shown that about 33 per cent of runners who complete 56K races come down with an upper-respiratory-tract infection during the two weeks after the race ('Respiratory Tract Infections: An Epidemiological Survey,' South African Medical Journal, vol. 64, pp. 582-584, 1983). Similarly, 13 per cent of the runners who completed the Los Angeles Marathon in 1987 became ill during the week after the race, versus just 2 per cent of control runners who didn't participate in the 26-mile event ('Infectious Episodes in Runners Before and After the Los Angeles Marathon,' Journal of Sports Medicine and Physical Fitness, vol. 30, pp. 316-328, 1990).

And mum probably forgot to tell you that if you run about 60 or more miles per week, your risk of illness is about double, compared to the individuals who log less than 20 weekly miles. That suggests, of course, that immune function declines as training volume increases, yet we also know that runners tend to be healthier than sedentary people. So, a very reasonable question would be: what number of miles per week is best for overall health?

Even mum herself doesn't know the answer to that question. The epidemiological evidence indicates that running a moderate amount of miles is better for your health than staying on the couch. However, running lots and lots of miles is worse for your health than being moderate: mega-mileage is associated with lots of sniffles, hacks, coughs, and perhaps other problems. Basically, the graphical plot of illness frequency versus mileage is a U-shaped curve. If there's no mileage, there is quite a bit of sickness, middle mileage leads to little illness, and high miles let the microorganisms rule again. The 'middle ground' of best health may well be 15 to 30 miles per week or so, or 35 to 45 minutes per day, but no one knows for certain, and the optimal amount no doubt varies from person to person.

You may not have been aware that over 200 different viruses can cause colds, but that a certain class of viruses - the 'rhinoviruses' (literally, viruses which affect the nose) seems to produce the most mayhem. Contrary to what you may have thought, it's not very easy to catch a cold directly from someone who is coughing and/or sneezing, because only small numbers of cold viruses leave the body in emitted mucus (that's not true for flu viruses, however, which fly out of the respiratory system in droves with a cough or sneeze). Running in damp, cold weather does not raise your risk of getting a cold, either.

As mentioned, moderate running, even in the winter, provides some protection against those ubiquitous cold viruses. People who run or walk moderately briskly for 35 to 45 minutes per day, five days a week, spend about half the number of days per year suffering from cold symptoms, compared to sedentary people. In addition, about 60 per cent of recreational runners experience fewer colds after they initiate a running programme, compared to when they were sedentary (only 4 per cent come down with more colds after starting to run regularly).


Protect your natural killer cells
Immune-system expert Dr. David Nieman of Loma Linda University says that 35 to 45 minutes of moderate exercise tends to boost immune-system activity, whereas three hours of exertion thwarts immune-system effectiveness for at least six to nine hours after the workout is over. For one thing, concentrations of 'salivary IgA', an oral-cavity antibody which helps prevent microorganisms from spreading from the mouth to other parts of the body, tend to fall after a strenuous workout ('Mucosal (Secretory) Immune-System Responses to Exercise of Varying Intensity and during Overtraining,' International Journal of Sports Medicine, vol. 15, pp. S179-S183, 1994). For another, the activity of 'natural killer cells,' key components of the immune system which directly attack and kill virally infected and tumour cells, declines by 45 to 62 per cent for at least six hours after a prolonged bout of exercise ('The Effect of Long Endurance Running on Natural Killer Cells in Marathoners,' Medicine and Science in Sports and Exercise, vol. 22, pp. 207-212, 1990). Studies also show that neutrophil function (neutrophils are white blood cells which consume many bacterial and viral pathogens) is normal in athletes undertaking relatively light training but below par during extended periods of intensive training ('PMN Cell Counts and Phagocytic Activity of Highly Trained Athletes Depend on Training Period,' Journal of Applied Physiology, vol. 77, pp. 1731-1735, 1994).

In addition to running moderately, another key way to stay away from colds is to stop touching your eyes, nose, and mouth. The average person touches those areas with his/her hands every 20 minutes or so, transferring viruses which have been picked up from keyboards, phones, doorknobs, etc. directly to the respiratory tract.

Overall, it's clear that if you are a very serious trainer, you're probably at increased risk of respiratory illness, so you would be very wise to take a number of precautions. Ingesting an optimal diet which is rich in vitamins and minerals and adequate in calories, getting adequate sleep, recovering well after workouts, and 'cycling' your training with hard and easy periods (rather than hammering all the time) should help keep the cold bugs at bay.

Almost finally, the dear old lady probably didn't tell you that running is more effective than diet at reducing blood pressure - and is just as effective as many prescribed medications at sending pressure downward. A single workout can decrease systolic blood pressure by five to six points and diastolic pressure by six to eight points for up to 13 hours. Overall, getting fitter can diminish everyday systolic blood pressure by 10 to 12 mm Hg and normal diastolic pressure by up to seven mm in people with pressure problems. Such decreases are associated with a 20- to 25-percent drop in the death rate associated with blood-pressure problems, for both Caucasians and individuals with an African heritage ('Exercise Can Reduce High Blood Pressure,' ACSM's Health and Fitness Journal, vol. 2(1), pp. 29-36, 1998).

However, mum probably didn't mention that if your blood pressure is already normal, your running routine may not change it very much, if at all. And she probably didn't say that exercise is most effective at reducing pressure when it simultaneously makes people fitter and slimmer. She may, however, have told you that endurance running is better than resistance training at reducing pressure, and maybe she even reported (correctly) that 'circuit' strength training may be nearly as good as regular endurance workouts for calming down your blood.

Overall, the research suggests that moderate-intensity exercise is more effective than high-intensity work at relieving blood pressure - and that 40- to 60-minute workouts are significantly more effective than 20- to 30-minute affairs.

As you can see, running has all kinds of surprising aspects and applications, many of which have a significant impact on your health. Mum forgot to tell you that putting one foot in front of the other is not such a simple thing after all.

Owen Anderson

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