Understanding Oxidative Stress

Did you know that exercising too long can shorten your lifespan? Most people think exercising is good, therefore more exercising is better. Scientists, however, have discovered that it is not so simple. Too little or too much exercise, along with stress, improper diet, inflammation and even pollution can lead to oxidative DNA damage. This causes cells to stop replicating. In order to increase life expectancy, it's very important to get the right amount of exercise.

What are telomeres and why should you care?

Within each cell is a DNA molecule composed of thread-like coils called chromosomes. At the end of each chromosome is a cap to prevent the ends from fraying. These caps are called telomeres: Telo (end) mere (segment). Think of the aglet, or plastic coating around the end of a shoelace. Each time a cell replicates, its telomere loses some of its base pairs and gets shorter.

Environmental and behavioral factors throughout the course of a lifetime, including too little or too much exercise, progressively shorten the telomere. When the telomere becomes so short that it cannot protect the chromosome from fraying, the cell can no longer divide properly — a condition called senescence. The result is that tissues stop regenerating, you age, and then you die. While this process is unavoidable, the rate of telomere decay can be slowed down through behavior modifications. In 2009, Dr. Elizabeth Blackburn and her team won the Nobel Prize in Medicine for this discovery(1).



Understanding oxidative stress

Every cell contains energy-producing organelles called mitochondria. Mitochondria provide the energy to do tasks such as breaking down nutrients and converting oxygen and glucose into usable fuel. These normal metabolic processes also produce atoms that contain unpaired electrons called “free radicals” that search for and steal partner electrons from other atoms to stabilize itself. As a result, damage is done to the DNA and other parts of cells, which sets off a chain reaction from atom to atom. To combat this, special molecules donate an electron to free radicals to make them stable and less able to react. These molecules are called antioxidants. Oxidative stress is an imbalance between too many free radicals and too few antioxidants in the body(2). This imbalance is a major cause of cancers and type 2 diabetes (3).

Exercise and oxidative stress

Oxygen itself is a free radical. Whenever a person works out, their muscles demand more oxygen, causing the heart to work harder. More blood flows to the brain, the blood vessels become more flexible, organs get more nourishment and the immune system is invigorated. All this is good. However, as a result of exertion, micro-tears also occur in the muscles. To repair them, enzymes and proteins flood the bloodstream and promote cell replication. The combination of the presence of increased oxygen free radicals, oxidative damage and cell replication results in the shortening of telomeres. This happens during all types of exercise and the amount of damage is determined by the exercise intensity and duration.

The importance of muscle fibers

There are two types of muscle fibers: Slow-twitch and fast-twitch. Slow-twitch muscle fibers burn fat and oxygen and are used in aerobic exercise like walking, jogging at an easy to moderate pace. Anaerobic (“without oxygen”) exercise uses fast-twitch muscles that rely on glycogen for short, intense bursts of activity, like jumping, sprinting and lifting heavy weights. Anaerobic activity also releases human growth hormone (HGH). HGH helps to reverse the signs of aging by:

• Restoring muscle mass, lost hair, and the size of the liver, the heart and other organs
• Decreasing body fat
• Increasing energy, sexual function and cardiac output
• Improving cholesterol, vision and memory
• Thickening skin and reducing wrinkles
• Normalizing blood pressure

Studies have shown that higher levels of HGH correlate with longer telomeres(3). Unfortunately, as we age, adults do less and less of the short, fast, intense activity that uses fast-twitch muscle fibers. Less HGH is released as a result, and decay starts to overtake growth. It is important, then, to use both types of muscle fibers to maintain good health.

Why shorter and faster exercise is better

Exercise is so important, that without it you are four times as likely to die at any given time. Your ability to push yourself during a workout is calledexercise capacity and it outranks even smoking and a history of chronic disease as a predictor of death(3).

When you exercise at an easy to moderate pace, you use slow-twitch muscles. The more you exercise this way, the more efficient you become and your body burns calories much more slowly. And since the muscles are doing the work really well, there is no need to produce new muscle tissue. People who exercise this way often become frustrated because they easily plateau, and regardless of how much or how long they exercise, they don’t seem to lose much weight. In addition, athletes who participate in extreme sports like marathons and triathlons are losing their fast-twitch muscles and activating free radicals. The oxidative damage produced from hours and hours of exercise requires a lot of cellular repair and replication, which is shortening the telomeres.

Meanwhile, just eight to ten seconds of high-intensity exercise performed at 90 percent or more of maximum effort will force the body into oxygen debt and trigger the release of HGH, which will continue for up to two hours after you exercise. In addition, increased metabolic activity orexcess postexercise consumption can continue for as long as 24 hours(4). This increased metabolic activity and HGH secretion leads to increased fat burning. When compared to runners, for example, people who practiced high-intensity training on a regular basis burned less than half the calories but up to nine times the body fat(5). This is why shorter and faster exercise is better.

Exercise and telomere length

There is a link between telomere length and exercise. People who exercise vigorously for an average of twenty-five minutes per day are biologically nine years younger than people who are sedentary and exercise less than fifteen minutes a week. Moderate exercise, defined as 90 minutes a week, provided a four-year advantage(6). People who participate in frequent endurance exercise, however, show increased stress on muscles and have shorter telomeres(7). By contrast, exercise programs lasting twenty minutes or less that mix high-intensity bursts with moderate-intensity active recovery periods produce the best results with the least amount of oxidative damage and telomere shortening.

In summary

Exercise done properly is the best way to counteract the aging process. What is the best way to get the most fitness while causing the least amount of oxidative damage? Limit your workouts to high-intensity exercise that uses and causes the growth of fast-twitch muscle fibers. Exercising this way will promote growth that balances the decaying process while slowing the rate of telomere shortening so that you can live longer!

Siphiwe Baleka - Contributing Writer, Physician’s Choice