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"It is well known that to stay young, intensity of exercise is more important than volume." Earl Fee, author of Secrets of a World Masters Champion.
The Necessity of Intensity
A number of people have called my attention to the feature story in the September 2000 issue of Scientific American: Muscles, Genes and Athletic Performance by the director and two researchers at the Copenhagen Muscle Research Center. Several were kind enough to actually send me the magazine. The article is an in-depth look at what we know about muscle fibers and how they affect athletic performance. The authors discuss the well-known fact that world-class sprinters have a predominance of fast-twitch muscle fibers, which contract up to 10 times faster -- and fatigue faster -- than slow-twitch fibers, which prevail in marathon runners and other endurance athletes. The average person, however, has roughly equal numbers of slow and fast fibers. The ratio of fast- to slow-twitch fibers appears to be determined by heredity. Exercise makes the fibers larger and stronger, but we are generally stuck with the ratio we have at birth. The one exception is a type of intermediate fiber which can take on the characteristics of fast or slow fibers, depending upon the type of exercise they are called on to perform. In sprinters, these intermediate fibers are transformed to fast fibers, and in endurance athletes to slow fibers. In short, it appears that world class athletes are both born and made; born with a desirable fiber ratio and made through training that converts the intermediate fibers in the direction required by their sport. The article ends with a teaser that recent developments in biotechnology may soon make it possible through gene doping to create a super-fast form of muscle fibers, which will allow athletes to run faster, jump higher and lift more.
While interesting, except for the teaser, the article contains little thatís really new and offers no practical guidance on how this knowledge can be applied to improve athletic performance. What really peaked my interest and got my mind going was a sidebar titled "Muscle and the Elderly." As I read it, the same authors generally take the position that little or nothing can be done to prevent aging muscles from becoming weaker and slower. Weight training can prevent some loss of muscle mass by thickening individual fibers, according to the sidebar, "but it appears to have no major effect on the loss of [fast-twitch] fibers." The problem, say the authors, is that the nerves which activate the fast fibers die off as we age, which causes the fibers to atrophy and eventually die. "Aging appears to be harder on the fast fibers, which atrophy at a higher rate than the slow ones do," the researchers write. Yes, but I wonder if the atrophy is the result of aging, or is it caused by the fact that most seniors do no high-intensity exercise. In other words, is the death of the fast fibers due to aging or lack of use?
Comparable Rule Thatís Wrong
Exercise physiologists have for years told us itís an ironclad rule that maximum heart rate slows every year after age 25. We all know the formula: 220 minus age. According to the textbooks, the decline occurs to the same extent in active and sedentary men and women; it is not altered by training. In my case, at least, thatís not true. As detailed in The Lean Advantage 3, Lovelace Foundation for Medical Education and Research in Albuquerque, New Mexico, measured my maximum heart rate for the first time in 1977, when I was a few months short of 40. It was 180, exactly in accordance with the standard formula (220 - 40 = 180). Interestingly, that was a few years after I began doing regular high-intensity aerobics.
Since then, my maximum heart rate has been measured in a laboratory setting seven times -- at ages 44, 47, 50, 51, 55, 60 and 62 Ė and has consistently exceeded the predicted rate by an ever widening margin. In June of this year, the Cooper Clinic in Dallas recorded my maximum heart rate at 182. Confounding the formula, my maximum heart rate has remained 180 or higher for 22 years. Why have I been able to defy the rule? Am I an aberration?
As I wrote in The Lean Advantage 3, I believe researchers simply havenít studied enough men and women who, like me, continue to train at a level which regularly causes their heart to beat at its maximum capacity. Like many other things having to do with the aging human body, itís a matter of use it or lose it. My guess is that the same is true of aging fast fibers.
Masters Sprinters Versus Marathon Runners
According to Secrets of a World Masters Champion, a book by Earl Fee, the world record results for masters runners show that sprinters decline in performance at a substantially slower rate than middle distance and marathon runners. Fee says this is true at all ages, from 35 to 90. For example, the 100 meter records for ages 35 to 65 decline 0.73 percent per year, while the marathon records decline 1.1 percent per year. Interestingly, the difference in rate of decline in sprinters and marathon runners is even wider for those in the 85 to 90 age group: 1.7 percent per year for the 100 meter record compared to 2.7 percent for the marathon. Sprinters, as noted Scientific American, rely on their fast-twitch fibers, while marathon runners use primarily slow fibers. This, of course, runs contrary to the statement of the Copenhagen researchers that aging appears to be harder on the fast-twitch fibers. What gives?
Sprinters obviously work more on maintaining speed than long distance runners. According to Earl Fee, 95 percent of the running mileage of sprinters is intense, compared only 12 percent for middle distance runners [and even less for marathoners]. Plus, Fee says sprinters supplement their running with weight training, plyometrics and flexibility drills, while distance runners usually do little or no weight training, no plyometrics, and no flexibility drills (they do a little stretching).
Fee also observes that athletes participating in activities involving muscular strength, such as the throwing events (shot, discus and javelin), decline at a slower rate than most other athletes, as shown by the many older athletes in these events at the Olympics.
"All this indicates the importance to staying younger and living longer of regular weight training, frequent stretching, and maintenance of intensity in training," says Earl Fee.
I agree. It seems clear to me that the loss of fast fibers usually seen in seniors is not written in stone, as suggested in Scientific American. Remember that most older people donít exercise, and those that do tend to gravitate toward slow jogging or other low-intensity forms of aerobics or high-rep, light weight training. What would happen if older people did hard interval training and high-intensity weight training? Thatís probably not going to happen on a large scale, but I believe people should be told that precipitous decline in strength and speed as we age is not necessarily in our genes. To a far greater extent than most exercise physiologists now suggest, I am convinced that the rate at which speed, strength and flexibility decline is subject to our control. I plan to fight the decline all the way. How about you?
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