The Effect Of Ageing On Endurance


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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.

Slowing Down

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.

Never too late

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.

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."


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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.

Whether they're competitive non-elites like Tarnopolsky or world-class performers like Dita, Master runners who perform well past 35 share one trait – they've turned their experience into an advantage. They have learned to recognise the types of training their bodies respond to best and they know how to reach their individual peak.

Most studies of physical decline associated with ageing haven't factored in the role of physical activity, says Scott Trappe, an exercise physiologist at Ball State University in the USA. "If you look at the cardiovascular system, people lose about one per cent per year," says Trappe. "We used to think that decline started at about age 25, but we're starting to see that people can maintain their aerobic capacity longer if they keep training. I'm 42, and my VO2 max is the same as it was in college."

"It's never too late to start," says Tarnopolsky. "We've put adults aged 65 and older on exercise programmes, and it's incredible the kind of gains they can make." Non-elites who came to the sport late are especially likely to hang on to their performance, or even improve with age. "If you've never trained seriously until age 35, it's quite possible to keep improving into your 40s and beyond," says exercise physiologist and running coach Jason Karp (runcoachjason.com). Runners who decide to get serious about the marathon at age 40 can easily continue setting PBs for years because they have so much room for improvement, he says.

As you age, factors like diet, body weight, time constraints and stress are just as likely to hurt your performance as is age – and those are factors you can actually manage, says Karp. What's more, it's your top-end performance that falls off first, so you're unlikely to see drops in performance like elites who're pushing the limits of human performance. "The higher the level that you've achieved," says Karp, "the further you have to fall."

Go the distance

Physiologically, there's nothing special about the decade between age 25 and 35, says exercise physiologist Dugas. Instead, he says, the fact that so many marathon runners hit their PBs at that age is probably a relic of their career paths, rather than a statement about intrinsic physiology. "There's not any rule that says you peak in your early 30s," says Dugas. "It's just that many runners don't move to the event until later in their careers."

In the absence of injury or mental issues, the world's fastest runner at 10K should also be the fastest marathon runner, says Dugas. "If we put you on a treadmill and keep upping the pace, the top speed you achieve is ‘peak speed', and it will predict who's the fastest runner for all distance events," he says. As evidence, Dugas points to Ethiopian Haile Gebrselassie, who broke his own world record in the marathon last September in Berlin, having already set records at 5,000m and 10,000m earlier in his career.

Framing marathon performance as an age issue is wrong, says Terrence Mahon, coach to US elite runner Ryan Hall, who came third in this year's Boston Marathon. What's key, says Mahon, isn't chronological age but athletic age – a runner's history of aerobic training.

In the past, coaches worried that turning to the marathon too soon would unduly shorten a runner's career. Running coach Brad Hudson, author of Run Faster from the 5K to the Marathon (£9.40, Broadway Books), ran his first marathon at age 12. "I think it hurt my career to go to the marathon so young," he says. Today, he doesn't advise kids to begin racing marathons as young as he did, but he says that secondary school and university runners can handle high volumes of training if they increase their mileage gradually. Hudson set his marathon PB (2:13) at 23.

What successful young marathon runners like Wanjiru have in common with older ones like Dita is a solid mileage base. "There are athletes out there running marathons at 21, but if you look at most of them, you'll see they've had a high training volume for a good many years before they've run the event," says Mahon.


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Obviously, young runners outside the elite ranks don't need to attain 100-mile weeks. But the same principle applies – to prepare for the marathon, first build a strong endurance base, then adopt a graduated training programme that builds to the marathon distance, says Jack Daniels, an exercise physiologist and running coach.

And there's still some way to go once you make the step up to the 26.2-miler. "It takes time to understand your body and how it responds to the marathon," says Hudson. "In the marathon you go through bad patches just like in life, and you have to be able get through. If you push too early, you'll be in trouble. You have to learn the speed your body can take for that distance."

Most runners need at least three cycles of marathon training to adjust to the training load. It's not just the mileage – it's the optimal nutrition, hydration and recovery. "The marathon is the only event where you're going to run out of sugar, and learning how to train for that is tricky," says Mahon. "To do really well could take in the neighbourhood of two to four years."

Exercise physiologist Dugas and his team have studied runners at the Two Oceans ultramarathon in Cape Town, South Africa, and found that people who run the 35-mile race multiple times generally post their best result on the second or third attempt. "I suspect the same thing would happen in the marathon," says Dugas.

Today's young marathon runners, like Wanjiru, have a lot of good times to look forward to, says Dita. "After 30 years, you have more experience, more mileage in your legs and your training is more serious."


Built for the long haul? How a marathon runner ages

Bones
When you age, your bones get less dense. Weight-bearing exercise like running helps, but it won't halt the process. As your bone density falls, you'll become more susceptible to stress fractures and other injuries.

Heart
Your maximum heart rate falls by about one beat per minute each year – and there's nothing you can do about it. The stiffening of your blood vessels that occurs with age will reduce blood flow to your muscles. Running, eating right and good genetics can help, but only so much.

Stress
Whether it's from life stress (a sleepless night or a deadline) or training stress (intervals or a long run), your body doesn't recover as it once did. Your muscle fibres dwindle and lose the ability to recover from hard efforts. Also, your glycogen stores shrink and blood flow to your muscles is reduced. Translation: it takes longer for injured or stressed muscle fibres to rebuild.

Body Composition
Even regular runners can gain body fat as they age. But adding a few extra miles to your programme each year can help you hold off the pounds. In one study, men and women who ran more than 29 miles per week gained half as much weight as those who logged roughly 15 miles or less per week.

Joints
Forget those warnings from non-runners – running does not increase your risk of osteoarthritis. But age does, especially in joints that you might have injured in your youth. Keep your weight down to minimise your risk.

Old Injuries
As you grow older, all those little injuries you ignored in your 20s can come back to haunt you. Your flexibility will decrease, as will your muscles' ability to recover from little tweaks. Consequently, you may feel stiffer after a hard effort since your muscle fibres require more time to repair themselves.

Muscles
No matter how much you train, you'll inevitably lose some strength with age, as your muscle fibres shrink and the neurons supplying the muscles begin to die off. Strength training can slow – but not stop – this process.


Youth Rules: Training wisdom for young athletes


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Build your mileage...
There's a reason most top marathon runners run 100 miles or more per week – success at that distance requires a solid mileage base. While that kind of high mileage isn't for most runners, having an aerobic foundation – and the time to build it – are mandatory.

...but don't overdo it
Give your body as much mileage as it can take – and no more. Overtraining is a huge challenge for marathon runners, so listen to your body's cries for rest. If your performance is flat, or you're unusually tired or taking extra long to recover, it's time for a break, says Alberto Salazar, elite runner-turned-coach. It's better to come in under-prepared than overtrained.

Focus on intensity
The marathon may be a test of endurance, but speedwork will really help you string together 26 strong miles. Still, all those hard tempo runs and track workouts take a toll on your body. You can handle that stress – and recover from it – better in your 20s than you can in your late 30s and beyond, says exercise physiologist Jonathan Dugas. Build that speed base now, while you can take the strain.


Age Gracefully: How Master marathon runners can run stronger

Focus on quality
Once you've built an aerobic base, you can get by on fewer miles. "You've built the foundation, so you're trying to maintain and be really efficient,” says elite coach Brad Hudson. "Start dropping the junk miles that helped you when you were younger.” Aim for the same types of interval sessions and tempo runs you did at an earlier age, says physiologist Jonathan Dugas, though you might have to do fewer intervals in a session or simply lengthen the recovery time between efforts.

Emphasise recovery
Age brings a decline in testosterone and growth hormone, which aid your recovery, says Dugas. The end result: you need to rest more. "Now that I'm older, I need more time to recover from my training,” says Constantina Dita, who won Olympic gold at the age of 38. She also uses massage and Jacuzzi baths to help her bounce back from hard efforts.

Adjust for stress
Whether it's a sick child, travel or a nasty deadline, stress hampers your recovery, so give yourself more rest so you're ready for the next training session. Dita knows that travelling takes a toll, so she builds extra rest into her programme when she journeys to a race.