The Science of Running
Outlegging Back Pain; The Price of a Pound; Ultra Hydration; Whither the Knees?
Outlegging back pain
If your back hurts, you’d think the logical remedy would be to strengthen your back. And indeed, that’s fairly standard advice. But a few years ago, researchers in Singapore studied runners with persistent lower back pain, and noticed a pattern: runners with back trouble were more likely to have weak quads compared to painfree runners. Could the weak quads lead to poor shock absorption while running, and ultimately to more stress on the lower back, they wondered?
To test this theory, they assembled 84 runners who were on a waiting list for physiotherapy to deal with persistent lower back pain, and assigned them to one of three exercise groups. One group did exercises to strengthen their back extension muscles, like “bird dogs”; another group did balance-focused back stabilization exercises; and a third group did leg exercises like single-leg squats and leg presses. Each group trained twice a week under supervision and were asked to complete exercises on their own on the other days, for a total of eight weeks.
The results, published in Medicine & Science in Sports & Exercise, showed that all three groups decreased their reported pain by similar amounts, but the leg exercise group reported a slightly bigger improvement in their ability to run comfortably. Strength tests showed that all three groups – even the leg exercise group – improved their back strength to a similar degree, while only the leg group improved leg strength.
Without a cont rol g roup, it’s hard to know exactly how effective the exercise programs were compared to just resting and waiting. But the results do suggest that simple leg-strengthening exercises can yield extra benefits by keeping your back muscles and stabilizers strong too – a point that’s worth bearing in mind not just for treating back pain, but perhaps also for preventing it in the first place.
The price of a pound
Anyone who has ever tried running with a backpack knows that extra weight slows you down. But how much, exactly? Back in 1978, researchers at the University of Georgia loaded runners down with a waist and shoulder harness, and found that each kilogram slowed them by about 1.9 seconds per kilometre. In a study presented earlier this year at the American College of Sports Medicine conference in Denver, Greek researchers tried the opposite approach, using a system of pulleys and upward-pulling ropes to subtract weight from their subjects. The verdict was surprisingly similar, with a speed-up of about 3.3 seconds per kilometre for each kilogram removed. In real life, of course, the weight on your body doesn’t behave exactly like weight added or subtracted with harnesses. Muscle helps propel you forward and keeps you injury-free, and even fat, beyond a certain level, plays an important role in your overall health. For the most part, your racing weight should be a natural consequence of your training rather than a separate goal. Still, the results offer a useful back-of-the-envelope tool for comparing performances across different weights – whether you’re trying to figure out how fast you can commute to work with lunch and a change of clothes on your back, or forec ast ing f ut ure improvements as you round into shape.
Ultra hydration
Exactly how much you need to drink during exercise has been a source of controversy for years now. One of the lesser known elements of the debate is the fact that, during prolonged exercise, you actually create new water within your body. As you burn carbohydrate and fat to fuel your muscles, the byproducts of these metabolic reactions are carbon dioxide (which you breathe out) and water. Moreover, your muscles store carbohydrates in the form of glycogen, which also locks away one to three grams of water for every gram of carbohydrate stored. As you burn through your glycogen stores, this water also becomes available for hydration.
Over the course of a marathon, a 2007 study estimated that you could lose one to three per cent of your starting weight without any change in hydration – a dramatic departure from the usual advice to avoid losing more than two per cent of your body mass. And the effects are even more dramatic in longer events, according to a new analysis by ultra researcher Martin Hoffman of the University of California Davis, presented at the Medicine & Science in UltraEndurance Sports conference earlier this year. A typical finisher at the 100-mile Western States Endurance Run, Hoffman and his colleagues calculated, should expect to lose 4.5 to 6. 4 per cent of his or her starting weight simply to maintain the same level of hydration.
One of the reasons these findings are important is because Hoffman and others have studied real-life hydration behaviour at Western States, and found widely varying approaches. Some runners lose eight per cent of their weight; others gain an astounding 10 per cent, with the fastest runners tending to lose slightly more weight. Hoffman has put together a set of hydration recommendations for ultra events, which focus on drinking when you’re thirsty, expecting to lose some weight, and carrying enough water between aid stations to allow yourself to drink whenever thirst strikes. The guidelines are available at ultrasportsscience.us.
Whither the knees?
Is osteoarthritis really a modern epidemic, or does it just seem that way because we’re living longer (and carrying more weight) than we used to? To find out, a Harvard University research team crisscrossed the continent examining about 2,500 skeletons from people who died as long as 6,000 years ago and as recently as 2015. Signs of “eburnation,” a polishing that occurs when your cartilage wears away and the bones of your knee joint rub together, revealed who did and didn’t have osteoarthritis. For the 20th-century skeletons, medical records indicated the age and weight of the subjects when they died.
The surprising result? Even after accounting for age and weight, knee osteoarthritis was still about twice as common in people born after Second World War than for those born earlier, according to the analysis published in the Proceedings of the National Academy of Sciences. While there are numerous possible explanations (the fact that we spend so much time walking on hard pavement now, for example), senior author Dan Lieberman and his colleagues suspect the culprit is widespread inactivity. Like muscles, joints and cartilage are healthiest when used regularly – so instead of worrying about whether you’re wearing your knees out, make sure you’re taxing them enough.