Are You Too Old – or Too Young – to Run your Best Marathon?

The two Olympic marathons held last August in Beijing were literally races for the ages. Kenya's Samuel Wanjiru, 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 Tomescu-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 two 25-year-olds - Dathan Ritzenhein and Ryan Hall - who qualified for the US Olympic squad (and finished ninth and 10th, respectively, in Beijing), as well as 19-year-old Kum-Ok Kim, a North Korean who finished 12th in the women's race. And on the other side of the age spectrum, the US women's team was led by two 35-year-olds - Deena Kastor and Magdalena Lewy Boulet - while 'old-timers' and world record holders Paula Radcliffe (34) and Haile Gebrselassie (35) showed no signs of slowing down. Impressive results from youngsters like Wanjiru and older runners like Tomescu-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 marathoners 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? First, the bad news. Whether you're an Olympic champ or a midpack 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. It's that your max 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. 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. Aging also leads to a decline in muscle mass, as neurons supplying the muscles begin to die. If the neurons shrink and die, the muscle fibres die. 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 off 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. 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 percent per decade’, says Dieter Leyk, a researcher at the Institute for Physiology and Anatomy in Cologne, 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 percent per decade for men and 14.8 percent among women. But that study yielded encouraging news for runners outside of the lead pack. For the non-elites tracked, 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. The bottom line: Keep up your training, and there's no reason you can't continue to put in solid performances well into middle-age. 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 age 50 and older 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 age 35 to 49 in the World Mountain Running Championships. The authors say the results suggest that VO2max can be held at high levels up to age 49. Sandra Prior runs her own bodybuilding website at http://bodybuild.rr.nu

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