In the long run, exertion regulation wins the day for marathon runners

Long-distance running is widely seen as one of the great physical challenges a human can undertake and as the 2008 Summer Olympics commence in Beijing on August 8, many eager sports fans will await with baited breath the last event of the Games – the men's marathon, held on August 24. For these armchair fans, how marathon runners can complete the grueling, 42.195 km event – physically and mentally – may seem like a great mystery.

Now, reporting in the open-access journal PLoS ONE, Jonathan Esteve-Lanao and Alejandro Lucia at the European University of Madrid and colleagues at the VU University-Amsterdam and the University of Wisconsin-La Crosse describe their investigation of the physiological methods employed by well-trained runners in order to regulate the great physical strain and effort that are needed in order to complete and perform well in marathons and other endurance challenges.

In order to measure the exercise intensity undergone by male runners of various abilities, Esteve-Lanao and colleagues evaluated the heart rate response of 211 middle- and long-distance runners during running competitions ranging in length from five to 100 km. These runners were not elite performers but all were serious competitors and some had enjoyed success in regional competitions.

The researchers found that throughout the course of the races, the runners' heart rate increased in a very controlled way, which appeared to be scaled to the distance of the race. When the heart rate response was scaled to the proportional distance completed, the results across races of different lengths were virtually identical. These findings support the notion that athletes actively manage the increasing strain on their body, in anticipation of reaching the finish line, constantly reassessing their levels of fatigue. Peripheral muscle fatigue, for example, would be highly regulated, with the working muscles giving continuous sensory feedback to the central nervous system to ensure that muscle fatigue is confined within a threshold, above which potentially dangerous consequences – especially muscle damage – could occur.

A surprising finding in this study was that the elite runners didn't run proportionally harder than the less-accomplished athletes and the heart rate response was very similar in all the participants despite the wide variations in competition ability and running performance. This suggests that Paula Radcliffe and other elite marathon runners do so well because of their great, underlying physiological capacity rather than because they put in more effort into their competitions.

Esteve-Lanao and colleagues also investigated instances of discontinuity in a runner's performance, most notably that of "hitting the wall." This happens when the athlete's glycogen stores have run so low that the body must burn stored fat for energy, which does not burn so easily, leading to dramatic fatigue and, potentially, life-threatening collapses, such as Dorando Pietri's collapse, 100 years ago, at the London Olympics in 1908. These examples support the idea that physiological catastrophes can and do occur frequently during strenuous endurance competitions because the athletes are either unwilling or unable to slow down their heart rate, despite dangerously high levels of strain.

The scientists conclude that athletes actively control their relative physiological strain during competition proportionally to the length of the race. According to the runner, Sir Roger Bannister, "The man who can drive himself further once the effort gets painful is the man who will win," but athletes who are not able to regulate their heart rate over the course of a long-distance race may burn out too soon and end up crashing out of the competition.

Citation: Esteve-Lanao J, Lucia A, deKoning JJ, Foster C (2008) How Do Humans Control Physiological Strain during Strenuous Endurance Exercise? PLoS ONE 3(8): e2943. doi:10.1371/journal.pone.0002943 http://dx.plos.org/10.1371/journal.pone.0002943

Source: Public Library of Science

Perfect Running Pace Revealed

A new study finds each person has an optimal running pace that uses the least amount of oxygen to cover a given distance.

By Dan Peterson

Most regular runners can tell you when they reach that perfect equilibrium of speed and comfort. The legs are loose, the heart is pumping and it feels like you could run at this pace forever.

Researchers at the University of Wisconsin-Madison now have an explanation for this state of running nirvana, and we can thank our ancestors and some evolutionary biology for it.

For years, it has been thought that humans have a constant metabolic energy rate. It was assumed that you would require the same total energy to run one mile, no matter if you ran it in 5 minutes or 10 minutes. Even though your energy burn rate would be higher at faster speeds, you would get there in half the time.

Turns out, however, that each person has an optimal running pace that uses the least amount of oxygen to cover a given distance. The findings, by Karen Steudel, a zoology professor at Wisconsin, and Cara Wall-Scheffler of Seattle Pacific University, are detailed in latest online edition of the Journal of Human Evolution.

Steudel's team tested both male and female runners at six different speeds on a treadmill while measuring their oxygen intake and carbon dioxide output. As expected, each runner had different levels of fitness and oxygen use but there were ideal speeds for each runner that required the least amount of energy.

Overall, the optimal speeds for the group were about 8.3 mph (about a 7:13 minutes per mile) for males and 6.5 mph (9:08 min/mile) for females.

The most interesting finding: At slower speeds, about 4.5 mph (13 min/mile), the metabolic efficiency was at its lowest. Steudel explains that at this speed, halfway between a walk and a jog, the runner's gait can be awkward and unnatural.

"What that means is that there is an optimal speed that will get you there the cheapest," Steudel says.

So, why is a zoology professor studying running efficiency? Steudel's previous work has tried to build a theory of why our early ancestors evolved from moving on four limbs to two limbs, also known as bipedalism. She has found that human walking is a more efficient method of getting from point A to point B than on all fours. It might also have been an advantage for hunting.

This latest research could offer some more clues of how we moved on to running. Steudel explains, "This is a piece in the question of whether walking or running was more important in the evolution of the body form of the genus Homo."

Dan Peterson writes about sports science at his site Sports Are 80 Percent Mental.

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Does Conjugated Linoleic Acid Work?

Conjugated linoleic acid is a natural substance found in many of our foods that according to many studies can reduce fat and improve muscle mass in the body. Taken as a supplement with no change in eating or exercise habits, it would not make you lose weight but it could help you lose fat. It is often taken by men looking to lose weight and bodybuild at the same time, but it can also be useful for anyone who is overweight and under-exercising, as any increase in muscle will increase the metabolism, burning more calories.

Like many natural weight loss products, conjugated linoleic acid (CLA) combined with a flexible healthy eating plan can lead to gradual long term weight loss and help you get out of the yoyo dieting cycle where you are constantly losing and gaining the same 10, 20 or 50 pounds. Yoyo dieting is very bad for the health. It is better to remain overweight than to keep on losing and gaining, losing and gaining.

Most experts (unless they are trying to sell you something) agree that the diet that works best in the long term is the non-diet, where instead of eating special foods and banning others, you eat slightly smaller quantities of a normal healthy diet. If you are currently living entirely on pizza, fries and chocolate, then okay, some changes may be overdue. But you can still have small portions of all of those foods from time to time. If this is the kind of diet that you want, then CLA can help reinforce your plan by boosting your fat loss. Dr Michael Pariza of University of Wisconsin-Madison, reported to the American Chemical Society that CLA "doesn’t make a big fat cell get little. What it rather does is keep a little fat cell from getting big."

Many studies have been done on CLA. One study published in the Journal of Nutrition found that people taking CLA lost on average six pounds of body fat more than a group that took a placebo. The researchers discovered that you need around 3.4 grams of CLA per day for it to be effective. CLA is found in food, especially meat and dairy products, but supplementation is necessary for most people to reach that level.

Another study at Purdue University, Indiana, found that CLA improved insulin levels in about two-thirds of diabetics, and slightly decreased their blood glucose level and triglyceride levels, suggesting that it may help to maintain normal insulin levels. But see your doctor before taking any supplements if you have diabetes.

There are no magic pills for weight loss but if you are willing to commit to reducing your body fat permanently, CLA may help you. Keep in mind that its main effect is to convert fat to muscle, which by itself will not weigh any less. But your body will look slimmer and feel healthier if you do this, and combined with a good weight control eating plan conjugated linoleic acid can help you move toward your ideal weight too.