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The two Olympic marathons held last August in Beijing were literally races for the ages. Kenya's Samuel Wanjiru, then 21, broke more than an Olympic record with his 2:06:32 win; he crushed long-held conventional wisdom that marathon performance peaks among runners in their late 20s and early 30s. That conventional wisdom also took a beating when a 38-year-old mother with 10 marathons under her belt, Romania's Constantina Dita, won the women's event.
To a casual observer, these Olympian efforts resembled an emerging trend, with runners young and old bursting through a narrow age boundary. The youth movement included 19-year-old Kim Kum-Ok, a North Korean who finished 12th in the women's race. And on the other side of the age spectrum, the GB women's team was led by Mara Yamauchi (now 36) and Liz Yelling (now 34), while ‘old-timers' and world-record holders Paula Radcliffe (now 35) and Haile Gebrselassie (now 36) show no signs of slowing down.
Impressive results from youngsters like Wanjiru and older runners like Dita might imply that marathon performance isn't bound by rigid age limits. But are these remarkable performances simply the exceptions to a rule, or are top marathon runners truly stretching age boundaries? If so, how and what are the implications for those of us who finish races far behind? Is there an ideal age to run your best marathon?
We posed these questions to top physiologists, statisticians, coaches and elite athletes. Their answers paint a picture that offers lots of encouragement to runners of all ages and talents.
First, the bad news. Whether you're an Olympic champ or a mid-pack runner, your aerobic capacity falls with age. For a healthy, trained athlete, it's not your heart's stroke volume or your ability to extract oxygen from blood that changes with age, says Sandra Hunter, an exercise scientist at Marquette University in the USA. "It's that your maximum heart rate declines, and no one can change that. It just plummets."
While the classic formula for calculating max heart rate (220 minus your age) is just a rough estimate, Hunter says, "The reality is, your max heart rate declines by about a beat a year." No one knows the explanation, but this drop in aerobic capacity explains why the average 50-year-old can't compete against a 20-year-old. "You can't reach the same max heart rate, so you're operating at a lower intensity to begin with," Hunter explains.
Ageing also leads to a decline in muscle mass, as neurons supplying the muscles begin to die. "If the neurons die, the muscle fibres die," says Hunter. "Sometimes they get regenerated by new neurons, but as you age you can't keep pace with cell death. Training can slow the process, but it won't end it." The atrophy seems to pick up about age 60, and hits fast-twitch muscle fibres hardest. That's why speed falls before endurance.
Usually, the age-related change that runners notice first is a drop in their ability to recover from training. Muscles store glycogen, so when you lose muscle mass with age, you also lose some of your glycogen reserves – and this means it takes longer to replenish these stores after a hard effort.
Age-related hardening of the arteries also cuts blood flow to your tissues, which means it takes longer for stressed muscle fibres to receive the materials they need to rebuild. In addition, with age your cells and their power-generating components (called mitochondria) begin to accumulate oxidative damage as a by-product of normal metabolism, and as a result they operate less efficiently. Adding insult to injury, levels of testosterone and growth hormones that aid recovery also fall with age, says exercise physiologist Jonathan Dugas, co-author of the blog Science of Sport.
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Improving With Age
These physiological changes inevitably alter marathon performance. Though individuals will age differently, studies indicate that beyond about age 35, endurance performance declines by about five to 15 per cent per decade, says Dieter Leyk, a researcher at the Institute for Physiology and Anatomy in Germany. Leyk recently examined age-related changes in marathon performance among 300,757 runners, and found that among top-10 finishers, running times slowed by about 10.5 per cent per decade for men and 14.8 per cent among women.
But that study yielded encouraging news for runners outside of the lead pack. For the non-elites, the decline was a little lower – and began later. "For these runners, significant age-related losses in endurance performance did not occur before the age of 50. Mean marathon and half-marathon times were nearly identical for the age groups from 20 to 49 years."
In fact, a 2004 study in the British Journal of Sports Medicine found that between 1983 and 1999, New York City Marathon finish times for top runners aged 50 and over improved more rapidly than did times for younger athletes. In the same vein, a 2008 Austrian study found no significant difference between the finish times of the top five racers aged 35 to 49 in the world mountain-running championships. The authors say the results suggest that VO2 max can be held at high levels up to age 49.
"Sure, there's an inevitable decline with age, but people are breaking down that barrier," says Mark Tarnopolsky, director of the Neuromuscular and Neurometabolic Clinic at McMaster University in Canada. Tarnopolsky won an Ontario trail-running series three times in a row, at ages 41, 42, and 43. "Last year, I was running better times in some races than I did in my 20s," says Tarnopolsky, now 45. The difference? He's smarter about training, cross-trains more, and can tolerate pain better than he could. Tarnopolsky also says his decades-long endurance base lets him get by on fewer miles.
Subscribers can access more information - including more in-depth physiological advice and tips for master marathon runners - in the full magazine article. If you'd like to subscribe, you can enjoy your first three issues for £3 by subscribing online now.