THE SCIENCE OF RUNNING: September/October 2010

Tapering under the microscope

Researchers at Ball State University’s Human Performance Laboratory took a highly invasive look at the muscle fibres of runners preparing for a big race and found strong evidence for why it’s important to rest up before competition. Members of a university cross-country team provided muscle biopsies three weeks before and immediately after their year-end championship race; the scientists extracted individual fibres and measured their size, contraction speed and force output. The results, published in the Journal of Applied Physiology, showed that after a three-week taper (reduction in training), the fast-twitch muscle fibres responsible for leg power were bigger, faster and stronger.

The study also measured markers of aerobic fitness such as VO2 Max, and found no change – an equally significant result. “One of the challenges for both athletes and coaches is to get them to rest, to convince them that they won’t lose fitness,” says Scott Trappe, the senior author of the study. Previous research has found that cutting training to about 50 per cent of normal volume in the final week or two before a race, while maintaining the same frequency and intensity, leads to a performance boost of two to eight per cent. That’s exactly what Trappe and his colleagues found with their test subjects, who raced six per cent faster in an 8K race than they had at the beginning of the study.

Weak hips and knee pain

For the past few years, sports injury specialists have been investigating the link between hip strength and running injuries. For example, Reed Ferber of the University of Calgary’s Running Injury Clinic found that an astonishing 92 per cent of the 284 patients who visited his clinic over a seven-month period in 2007 had weak hips, and 89 per cent of them improved their symptoms after undertaking a strengthening program. Now researchers at Indiana University have completed a new study suggesting that hip strengthening can help eliminate patellofemoral pain syndrome, sometimes known as “runner’s knee,” in female runners.

The Indiana study, which was presented at the annual meeting of the American College of Sports Medicine in Baltimore, involved just five injured runners and four controls. But the reduction in pain, from seven out of 10 to two or less after six weeks of twice-a-week hip strengthening exercises, was significant. “I wasn’t expecting such huge reductions, to be honest,” lead researcher Tracy Dierks admitted. Weak hips allow the knees to collapse inward, particularly in female runners, leading to knee problems, Dierks believes; exercises such as single-leg squats help to prevent this collapse. Further studies with a larger number of participants are planned to see if the results are repeatable.

Distance for heart, sprints for the muscles

One of the hottest trends in fitness research is “high-intensity interval training” – the idea that short bursts of intense exercise can provide as much benefit as long slogs. Most of the studies have examined cycling, but a new study from researchers at the University of Western Ontario’s Exercise Nutrition Research Laboratory applies the idea to running. They had 20 volunteers exercise three times a week for six weeks: one group ran steadily at a moderate effort for 30 to 60 minutes, while the other group did four to six hard 30-second sprints with a four-minute recovery. Both groups improved 2K time trial performance by about five per cent, and boosted their VO2 Max (a measure of aerobic fitness) by about 12 per cent.

What’s most interesting is that the researchers also measured maximal cardiac output, which is the biggest volume of blood your heart can pump at a time. In this case, only the long-run group improved (by 9.5 per cent), while the sprinters didn’t improve. VO2 Max depends on two basic quantities: how much oxygen your heart can deliver to your muscles and how much oxygen your muscles can actually use. Since both groups improved VO2 Max by the same amount, this means that the long-run group primarily improved their cardiac function, while the sprint group primarily improved their muscle function. If anything, this is an excellent reason to incorporate both types of training in your weekly routine, since you’re only as strong as your weakest link.

Fuel for a one-hour run

If you’re running a marathon, you need to take in some carbohydrates to fuel yourself; if you’re sprinting 100m, you can leave the buffet belt at home. Where it gets murky is the middle ground, for sessions lasting about an hour. To address this question, researchers from Loughborough University in Britain had 10 volunteers eat a high-carbohydrate meal three hours before a treadmill test where they ran as far as they could in one hour. Before and during the run, they either consumed a sports drink containing 6.4 percent carbohydrate, or placebo drink. The results: no difference whatsoever in performance, blood glucose, lactate, respiration, carbohydrate burning, perceived exertion or anything else they measured.

Crucially, the same group performed a similar study last year where the subjects didn’t eat a meal three hours before the run. In that case, taking a sports drink did improve performance during a one-hour run. When you fast – for example, sleeping overnight – the glycogen stores in your liver drop by about 50 per cent because they’re fuelling your heart and brain. It’s these liver glycogen stores that you need to top up if you’re going for a run on a completely empty stomach, such as first thing in the morning. At other times, the new study suggests that your body has plenty of energy to get you through a one-hour jaunt.

The training effect

Runners at every level often wonder exactly how champions train. Readers of the Journal of Strength and Conditioning Research were recently offered a rare glimpse into the training diaries of “an Olympic 1500m finalist,” who turned out to be three-time Olympian and Canadian record-holder Kevin Sullivan. Researchers from Eastern Michigan University were granted access to Sullivan’s highly detailed training logs between 2000 and 2006, which they analyzed according to something called “impulse-response” theory. Essentially, every bit of training you do leads to immediate fatigue and a subsequent increase in fitness. That means that your performance on any given day should be the sum of all the bits of fatigue and adaptation from your previous workouts.

The researchers painstakingly converted every entry in Sullivan’s log to a “training stress score” where 100 points was equivalent to running all-out for an hour. As it turns out, Sullivan tends to average 50-55 per day over a full year. During base training, he averages over 60, with individual days sometimes exceeding 100. In his 2000 season, the data show a big dip in training stress and a corresponding performance peak just before the Sydney Olympics, where he finished fifth – a well-timed peak capitalizing on several months of hard training.