running economy

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Some things about running are pretty obvious. By now, nearly everyone knows that running 1200- and 1600-metre intervals at 95% VO2max (5K speed) is a good way to improve maximal aerobic capacity. Almost all runners know that completing two-mile intervals at 10K velocity is great for lactate-threshold boosting. Just about everyone realizes that hill training is excellent for economy. And everyone, including even the most dedicated sofa slug, has accepted the idea that running is a pretty effective way to lose weight.

However, some things about running aren't so obvious. For example, you may not be aware that if you test short-distance (800- and 1500-metre), middle distance (3K, 5K, and 10K), and long-distance (marathon) runners for running economy, the short-distance competitors will almost always have the best economy at speeds of marathon race pace and faster (eg, they will use the least oxygen to run at marathon, 10K, 5K, 3K, 1500m, and 800m race velocities). This is true for both male and female runners, and it contradicts what many coaches and runners have traditionally believed - that marathon runners tend to be the individuals who develop the most efficient running style. The truth is that the speediest athletes are the most economical - even when you slow them down to marathon-type velocity ('Running Economy of Elite Male and Elite Female Runners,' Medicine and Science in Sports and Exercise, vol. 24(4), pp. 483-489, 1992).

So, we can forget about those foolish recommendations to develop a 'marathon shuffle' in order to save energy for the 42K long haul, since you run more efficiently if you mimic the 1500m competitor. Why didn't mum tell us that! And we are free to chastise her for not telling us that up-tempo training (800- and 1500m style) seems to be best for building economy, not those longer runs at more middling paces. We should also tell her that she should have required us to read Frank Horwill's fine book, An Obsession for Running, which outlines the merits of training at 5K, 3K, 1500m and 800m paces, even if you are a long-distance runner.

You may not be aware that marathon runners have the best economy, compared to other runners, only at speeds slower than marathon pace. Evidently all those long runs do some good after all! Now we just have to convince most marathoner trainers to switch their preferred race distance to 100K, rather than 26 miles.

One of the reasons that marathon runners have tended to do pretty well on economy evaluations in the past has been that most previous economy research asked runners to amble along at very moderate (sub-marathon) speeds during testing. When that is the case, marathon runners indeed do very well, but when you speed the lab treadmill up to race-type efforts, the marathoners suddenly look shockingly energy-wasteful. Basically, they lack the strength and coordination which are needed to be truly efficient at high speed.


What Said did
Your mum also no doubt forgot to tell you that when Said Aouita was in his prime, he would train during the track season at 5K, 3K, 1500m, 800m, and 400m velocities over a period of 10 days. The day after one of these five different quality sessions, he would simply run four or five miles at 6:30 per mile to recover. When running track, Said seldom exceeded 50 miles of running per week!
That 'small' number of miles doesn't mean that Said was lazy, however. He simply knew about the importance of high-quality training. And you probably didn't know that once a week during the winter, Aouita would complete a fair number of 100m uphill sprints to build up his strength and economy. In fact, he would do 50 such sprints per workout (for the mathematically challenged, that's 5K of uphill sprinting)!
Speaking of high-quality running, you probably didn't realize that, for runners over the age of 60, one of the best ways to reduce the risk of heart disease is to run faster. If you weren't aware of that, you're not alone: most runners over 60 haven't heard the news either, and have consequently substituted moderate running for their track intervals. People who have reached 60 usually think that hard running is great for competition - but not for health.

Not so, says Paul Williams, PhD., of the Lawrence Berkeley Laboratory in Berkeley, California. Recently, Williams compared the HDL-cholesterol concentrations, total-cholesterol-to-HDL ratios, plasma fat levels, systolic and diastolic blood pressures, body compositions, and waist circumferences of 1,110 male runners over the age of 60 with their average racing speeds and training volumes ('Coronary Heart Disease Risk Factors of Vigorously Active Sexagenarians and Septuagenarians,' Journal of the American Geriatric Society, vol. 46, pp. 134-142, 1998).

Williams' findings were heartening. Better 10K times were strongly associated with higher HDL-cholesterol (aka 'good' cholesterol) readings, better total-cholesterol-to-HDL ratios, and lower blood pressures. In fact, Williams was able to show that for each kilometre per hour increase in 10K running speed, HDL rose by about 1.5 mg/dL. Translated, that means that a man who improved 10K running pace from 10 kilometres per hour (which would produce a finishing time of exactly 60 minutes) to 12 kilometres per hour (with a race clocking of 50 minutes) could benefit from a nice, three-point rise in HDL, reducing his risk of heart disease by almost 20 per cent. To put it another way, each improvement in 10K pace of about 22 seconds per mile could be associated with a drop in heart-disease risk of around 5 per cent.

If you're an acute reader, you may be saying 'Whoa - hold on there!' You're probably thinking that there's no real evidence that running faster actually causes the HDL upswings: Williams' research simply detected associations between variables, so it doesn't provide hard evidence that A (quicksilver pacing) causes B (good blood HDLs).

However, there is a reasonable physiological mechanism to back up the idea that running harder leads to higher HDLs. And that mechanism is simply that individuals who run faster10Ks (and no doubt also train harder than other runners) tend to lose more weight because they burn more calories per workout minute, compared to runners who amble along in a more relaxed fashion. As it turns out, reduced body fat accounts for almost all of the difference in HDL concentrations between runners and sedentary people ('Weight-Set Point Theory and the High-Density Lipoprotein Concentrations of Long-Distance Runners,' Metabolism, vol. 39, pp. 460-467, 1990). Thus, running faster makes you slimmer (Williams was able to find this in his data, too), and the slimness helps boost HDL.

Speaking of the link between speed and HDL levels, you probably weren't aware that you could roughly predict a runner's HDL concentration, plus total cholesterol, LDL-cholesterol (aka 'bad' cholesterol), blood pressure, and blood-fat levels from his/her marathon time, but you can! Research carried out in Germany reveals that as marathon times slow down, HDL readings fall, LDL levels rise, blood fat increases, and blood pressure ascends. As the Germans put it, 'Cardiovascular risk factors are related to fitness level,' even in a group of well-trained runners who are able to complete a marathon in a reasonable amount of time ('Does Conditioning Affect Cardiovascular Risk Factors in Long-Distance Runners?' Medicine and Science in Sports and Exercise, vol. 25(5), 1993).


Changes in waist girth per 10K
What other things did mum forget to tell you about running? Well, she probably didn't mention that once you reach the age of 60, your HDL should rise by about 1.5 ticks for each additional 10 kilometres of running that you complete per week. Plus, for each 10 kilometres, your waist circumference will narrow by one centimetre, your hip circumference will do the same, your diastolic blood pressure will dive by .4 mm Hg, resting heart rate will go down by .6 beats, and blood-fat levels will decrease by 3.3 mg/dL.

Overall, increasing running mileage actually works better than raising running speed for boosting HDL-cholesterol in both men and women, according to a follow-up study conducted by Williams which analyzed 7,059 male and 1,837 female runners (it was about time that women were included in this kind of research!). However, speed was stronger than distance at lowering total cholesterol, body fat, waist circumference, and both systolic and diastolic blood pressure in men - and also systolic blood pressure in women ('Relationships of Heart Disease Risk Factors to Exercise Quantity and Intensity,' Archives of Internal Medicine, vol. 158, pp. 237-245, 1998). The subjects in this study ranged in age from about 30 to 80 (average age was 46 for men and 41 for women).

Your dear mother probably also didn't reveal that - in terms of getting slimmer - total mileage is much more important for runners over the age of 60 than it is for younger competitors. The reduction in waist size per 10 weekly kilometres of running is significantly greater in sexagenarians, compared to fresh-faced whippersnappers. In addition, added mileage is more likely to cut away intra-abdominal fat (the kind highly associated with heart disease) in oldsters, compared to young runners. That's particularly important, since caloric restriction (dieting) is less effective for promoting weight loss in older individuals, compared to younger people ('Effects of Weight Loss Vs. Aerobic Exercise Training on Risk Factors for Coronary Disease in Healthy, Obese, Middle-Aged and Older Men,' Journal of the American Medical Association, vol. 274, pp. 1915-1921, 1995).

Being the conservative person that she was, mum probably did tell you that if you're over 60 and decide to run either more or faster, it probably would be a good idea to get a symptom-limited maximum exercise test first, especially if you already have coronary risk factors. But she no doubt failed to tell you about the relative efficiency of males and females.


The economy of being male or female
The truth is that when male and female runners get together and run at the same, fairly high-quality pace, the males will usually be more economical. For example, if a group of males and females run briskly along at 268 metres per minute (about six minutes per mile), the men will simply require less oxygen to keep moving along at that speed. Mum didn't tell you that.

However, she also didn't tell you that there's a good reason for this apparent male parsimony. That is, since males on average have higher maximal aerobic capacities than females, and since pace is linearly related to oxygen consumption (the faster the pace, the greater the O2 use), any particular quality pace will usually be more stressful for women (eg, it will coincide with a higher percentage of their VO2max, since their VO2max is lower).

If you actually took into account the usually lower VO2max in females, you would test the two sexes for economy by having the men and women run at the same percentage of VO2max, not the same absolute speed (for example, you could have males and females running at 85% VO2max). Of course, when you do that, the females will usually be running more slowly, since their VO2maxs are lower. But if you do that, you will also find that economy is absolutely equal in male and female runners ('Running Economy of Elite Male and Elite Female Runners,' Medicine and Science in Sports and Exercise, vol. 24(4), pp. 483-489, 1992).

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