The debate over how much exercise is needed can seem endless. the minimum recommendation in the UK is 30 minutes of ‘moderate’ exercise five times a week, not that most adults encounter it. Some health experts believe that alternative diets will do us more good, such as shorter fights very intense exercise three to four times a week; or restrict periods of inactivity to a maximum of 60 minutes at a time.
The problem with this debate is that it risks assuming that exercise is always good for you. In reality, this is not always the case. Most of us know the need to warm up properly and avoid exercising when we’re in bad weather, but some risks may not yet have reached the public consciousness. What follows are a few words of caution for anyone who gets into a sweat. You never know, they might just save your life.
1. Easy to do
People who aren’t used to exercising and go all out can develop an unpleasant condition called delayed onset muscle pain. This involves sore, tender muscles and a reduced range of motion of the joint in the affected area. It can last several days and peak about 48 hours after exercise.
The condition is caused by the body’s reaction to the trauma of sudden exercise: white blood cells infiltrate the muscles and digest the damaged tissue, causing acute inflammation. How avoid this experience? Anyone starting an exercise program should build it up gradually.
2. Do not stimulate too much
In extreme cases of delayed onset muscle pain, enzymes released by muscles during digestion of damaged tissue can induce a condition called rhabdomyolysis in which enzymes from damaged muscle cells are released into the blood. In severe cases this can lead to kidney failure, but fortunately this seems to be relatively rare.
The use of electrical stimulation devices as a substitute or supplement to exercise may also would have cause rhabdomyolysis. These devices work by attaching electrodes to different muscle groups and have become increasingly popular in recent years. Now, however, clinicians emit warnings about the dangers of overuse.
3. Hey, Ironman…
If you’re thinking of pushing yourself seriously, a brief lesson on the function of the heart is in order. The heart works in two phases, a contraction phase and a relaxation phase. In the contraction phase, blood is ejected from the right and left ventricles into the arteries by contraction of the heart muscle. In the relaxation phase, blood fills the ventricles to prepare for the next contraction.
The average human heart contracts about 70 times per minute, 24 hours a day, and accumulates about 3 billion contractions over a 75-year period. It is considered that the heart can cope with even strenuous exercise, reaching around 200 beats per minute to pump enough blood and oxygen throughout the body.
Yet studies looking at the effects of prolonged intensive exercise such as an Ironman triathlon showed a temporary decrease in the relaxation function of the heart after the athlete stops exercising. This effect has been called “cardiac stunning”.
Perhaps more worryingly, some participants in these grueling events displayed biomarkers of heart damage are usually only found after a heart attack – although levels tend to be just above the threshold indicating damage and the effects appear to be short-term. However, later studies also suggest this could be detrimental to heart function in the longer term.
That said, it’s worth pointing out that not all exercise is bad for the heart. Exercise maintains heart function and, in the case of heart attack patients undergoing a rehabilitation program, can significantly improve it.
4. Immune Care
Moderate exercise is believed to boost our immune function by causing an increase in the number of white blood cells in our blood. On the other hand, performing three or four hours of intense exercise – normal for the course for professional athletes – was related to a decline in immune function over the next 24 hours.
After that it would go back to normal, but for people like athletes who do it daily, longer term studies have demonstrated that intense exercise repeated over several weeks can suppress immune function by lowering the number of white blood cells and making them less effective. It would then take much longer for the immune system to correct itself.
What to do about it? You can lessen some of the effects with a good diet (or exacerbate them by eating poorly). Even better, you can also keep bugs away with good personal hygiene. It is no coincidence that this message is transmitted to the athletes who participate in the Olympic Games today.
Back to home
None of this is meant to suggest that moderate exercise isn’t good for us. Sports doctors and scientists would agree that it maintains and promotes good heart, muscle, immune and also metabolic function. We may still be debating which diet is best, but it’s still rightly a major goal for medical professionals to educate the public about the beneficial effects of exercise.
That said, there are limits. People need to be more aware of the risks of doing too much too soon – and taking things to extremes. Exercise is good for you, but take the wrong approach and you might wish you were on the couch.