The Science of Running
Do Soft Surfaces Make a Difference?, Prepping for Altitude, Stress Fracture Signs, LCHF for Endurance
Aside from the scenery, one of the biggest attractions of trail running is the escape from concrete. From an injury-prevention standpoint, trails are thought to offer two key advantages over roads: softer, more forgiving surfaces, which reduce the jarring impacts of each stride; and uneven terrain that forces your foot to land in slightly different positions, reducing the repetitiveness of the impact. Proving that these factors really reduce injuries, however, has turned out to be surprisingly difficult. The few studies that have tested these claims have produced conflicting results, and some researchers argue that we automatically “tune” our muscles to produce a similar impact force no matter what surface we’re running on.
That makes the results of a recent study by scientists in Belgium, published in the journal Sports Biomechanics, particularly interesting. Instead of measuring impact forces in a laboratory setting, they used tiny accelerometers attached to the shins of 35 volunteers to measure running impacts on three different real-life surfaces: concrete, a synthetic running track and a wood chip trail. The results showed that vertical acceleration of the lower leg was indeed reduced on wood chips compared to the other two surfaces, suggesting that it could – in theory, at least – lower injury risk.
So what about the role of variability? That’s much harder to quantify, but similar ultra-light accelerometers may soon allow researchers to collect data on that too. In 2015, as a proof-of-principle, researchers in France had top mountain trail runner Kilian Jornet wear three of these accelerometers during a 45-kilometre trail race. They found that as the terrain varied, he made liberal use of three completely different foot-strike patterns: forefoot, midfoot and rear-foot. Whether that variability translates to lower injury risk remains to be seen – but it certainly seems to work for Jornet.
Prepping for altitude
The challenge of mountain trails isn’t just the rocky terrain, steep climbs and vertiginous drop-offs. Once you get above about 1,000 m of elevation – roughly Calgary’s level – the thin air begins to have measurable effects on your aerobic capacity. By the time you get to Banff, at 1,383 m above sea level, the effects are obvious; at the 2,350 m summit above Kicking Horse resort, where the national mountain running championships finished a few years ago, you’ll be gasping.
The best defence against altitude is weeks of acclimatization. But for those who don’t live in the mountains (and don’t own an expensive altitude tent), are there any alternatives? A series of recent studies have raised hopes that the simple act of training your breathing muscles – the seven to 11 lb. of muscle around your diaphragm and ribcage – can improve high-altitude endurance. A study of British soldiers trekking toward Makalu, in Nepal, found that those who had done four weeks of training for their breathing muscles, which essentially involved repeatedly inhaling against
resistance, had higher levels of oxygen in their blood.
That study used a device called PowerBreathe. More recently, a University of Buffalo study published last year used a technique that involved half an hour of controlled hyperventilation, three times a week for four weeks, to boost endurance in a cycling test to exhaustion at a simulated altitude of 3,600 metres. The findings suggest that, since thin air forces us to breathe more heavily to get the oxygen we need, our breathing muscles are likely to fatigue prematurely at altitude. Training those muscles in advance prepares them to handle that extra work without fatiguing as much. For now, the concept remains preliminary and requires more research – but it’s a promising possibility for flatlanders planning a trip to the mountains.
Stress fracture warning signs
It’s no secret that not getting enough calories can lead to a spiral of health problems, including weakened bones, in female runners. But identifying who is really at risk remains a challenge. A consensus statement published in the British Journal of Sports Medicine in 2014 tried to quantify risk based on six criteria: inadequate calorie intake; low body-mass index; irregular periods; delayed age of menarche; low bone mineral density; and history of stress fractures. Combining these categories produces a risk score that is classified as low, moderate or high.
But how reliable is this prediction? Researchers at Stanford University tracked 323 female athletes, including 47 cross-country runners – with sobering results that were recently published in the American Journal of Sports Medicine. About half the runners were identified as low-risk, and only three of these runners went on to develop stress fractures. But of the remaining runners who were classified as moderate- or high-risk, more than half of them suffered from season-ending stress fractures, within an average time of a year. The risk score can be used to identify runners who need dietary changes and monitoring, says Adam Tenforde, the study’s lead author; and these athletes may also benefit from a switch to more low-impact cross-training.
LCHF for endurance
The claim that low-carbohydrate, high fat ( lchf) diets can boost endurance performance has been hotly debated in recent years – but mostly with competing anecdotes. New results published in the Journal of Physiology, from researchers at the Australian Institute of Sport, offer some muchneeded data. A group of 21 world-class Olympic racewalkers, including Canadian near-medallist Evan Dunfee, gathered in Australia last winter to complete a series of three-week training blocks. Some were fed a standard diet with 60– 65 per cent carbohydrate, 15–20 per cent protein and 20 per cent fat; others went lchf, with 75–80 per cent fat, 15–20 per cent protein and less than 50 g per day of carbohydrate, scarcely more than a single can of Coke.
The results showed a dramatic increase in fat-burning capacity in the lchf group, nearly tripling their pre-intervention levels. But it came at a cost: they were also less efficient, requiring more oxygen to maintain their goal race pace. As a result, the lchf group performed worse than the control group in the 10k racewalk trials used as a performance test. It’s still possible that lchf diets may have benefits in other contexts – for example, in reducing the need to refuel during ultra-events, particularly in athletes whose primary goal is simply to finish rather than compete. And there may be other ways of combining lchf and normal diets to get an edge; Dunfee and other racewalkers returned to Australia this winter for a follow-up study to test that idea. The debate, in other words, will continue.