For Mike Teti, the 50-year- old head coach of the U.S. men’s rowing team and a three-time Olympian, it came all at once, on a day in 2000 he still remembers clearly.
The team had a rare day off, and Teti took his newspaper to a coffee shop in Princeton, N.J., to relax. He opened it and couldn’t read the print. He went to the boathouse to work out on a power-measuring machine called an ergometer. He had the worst scores he’d ever seen. Getting dressed to go home, he noticed his pants were tight.
“For me, everything happened at once. Almost overnight. And you say, ‘Oh my God, I’m over the hill.’ ” Teti has long since come to terms with the fact he will never again be the athlete he was.
To understand why the decline of athletic performance is inevitable with aging – and why it is partially reversible at any age – requires a little knowledge of exercise physiology. (Don’t worry, it’s worth it.)
Sports that combine strength and endurance – rowing is perhaps the best example – are enterprises that in many ways come down to one basic task: finding a way to deliver the most oxygen to muscles as fast as possible.
Oxygen is part of the fuel that allows muscle tissue to produce mechanical energy – to contract, in a word. Glucose (a form of sugar) or fat are the other necessary fuels.
Muscles can work for short periods without oxygen – so- called anaerobic respiration. But for sustained, long-term exertion, there is no substitute for oxygen.
Oxygen is carried in the blood, principally attached to hemoglobin in red blood cells but also dissolved in the blood’s water, or plasma.
It is put into the blood by the lungs, which are basically an elaborate mechanism for exposing an extremely thin layer of blood to air. Once it reaches muscle cells, oxygen is taken up by mitochondria, a vast archipelago of microscopic power plants floating in each cell’s inland sea.
When a person commences athletic conditioning, the demand for oxygen goes up. Muscles want more oxygen as fuel. The number of muscle cells increases, and the cells already present get bigger. The number of mitochondria in each cell also goes up, in some cases dramatically.
For oarsmen and marathoners, it can double.
The body’s capacity to use oxygen is measurable. It’s called “oxygen uptake,” is designated “VO2” and is reported as the liters of gas absorbed per minute through breathing. When people train, their VO2 goes up; when they become sedentary, it goes down.
But there’s a limit – maximum oxygen uptake, or VO2 max.
A rower or runner might enhance performance beyond that point through extraordinary effort, but the extra speed won’t come from oxygen-based energy.
It will require anaerobic respiration – a process that produces lactic acid, makes muscles feel as if they’re on fire, and can’t be sustained for long.
Training not only raises VO2 max, it also dramatically increases the level of exertion a person can sustain for long periods. This is something sedentary people realize when they try to keep up with their fit friends over a mile and not just 100 yards. Trained athletes can function at 87 percent of their VO2 max for an hour and then 83 percent for a second hour. For the untrained, it is 50 percent the first hour and 35 percent the second.
In theory, many things could determine VO2 max, but in practice one thing predominates – the heart’s ability to move oxygen-rich blood around the body. That is far more important than, say, the lungs’ ability to put oxygen into the blood or the muscles’ ability to take it out.
Endurance training enhances blood delivery in several ways. The distribution system improves; blood vessels get wider; and the number of capillaries in muscle tissue goes up. But again, one variable predominates – it’s the heart’s pumping capacity, the volume of blood it can move per minute.
Training can raise this so-called cardiac output from a maximum of about 6.6 gallons per minute in an untrained person to about 10.6 gallons in a highly fit athlete. The heart achieves this by beating faster, filling fuller after each beat and squeezing harder.
And it is all those capacities (and more) that decline with age.
Maximum heart rate declines about 5 percent per decade as the heart becomes less responsive to the adrenaline-like hormones that whip it into action. VO2 max declines from 6 percent to 10 percent per decade after age 25, and this accelerates to 15 percent per decade after age 60.
At the receiving end, muscle strength declines from 10 percent to 15 percent per decade starting at about age 30. This is because there is an actual loss of muscle fibers (and the nerves that drive them), and because some fibers usually used to generate brief bursts of power are transformed to longer-acting endurance fibers – a change that reduces strength overall.
By age 70, a person is only half as strong as he or she was in youth.
While the performance of nearly all the body’s physiological variables goes down with age, the decrement in athletic performance depends on the sport and the athlete’s baseline fitness and skill.
Exercise physiologists have come up with many interesting observations about sports. In football and baseball cardiovascular fitness is less important to overall performance than it is in such activities as swimming.
Age makes little difference in the performance of punters in the National Football League, but the passing success of quarterbacks improves significantly between ages 22 and 26.
For pro baseball players, the number of hits a batter gets and the number of strikeouts a pitcher gets both peak at age 27.
But the percentage of times a player walks peaks at 30, fielding percentage peaks at 31, and the earned run average for pitchers peaks at 29.
Conclusion: Experience and practice count and can make up for loss of strength.
A study of triathletes in their 20s, 30s, 40s and 50s competing in a half-Ironman race found that performance for each part of the event (swimming, biking, running) declined at roughly the same rate in each age group.
A study of weightlifters showed that upper-body strength declined at the same rate as lower-body strength.
Conclusion: No part of your body is spared the effects of age. So exercise it all.
That last piece of advice is the thing that falls out of the vast, detailed understanding of exercise physiology of the past 90 years.
Aerobic capacity and muscle strength can be improved with exercise even when people are in their 80s.
Peak performance for most sports may occur in a person’s 20s or early 30s, but “in terms of the trainability of the tissue, that seems to be maintained even when the person has another 50 years on their bones,” said Edward T. Howley, a physiologist and exercise researcher at the University of Tennessee in Knoxville.
“It’s never too late to start an exercise program.” Still, the fact that it may be too late to win a race is a hard thing to accept. Especially if you are used to winning races.
