Watching a skilled runner such as Kilian Jornet on a technical descent is a memorable sight. Taking full advantage of gravity, they throw themselves down hillsides without fear. Just like a car with the clutch in rolling down a hill, they expend no energy, saving it for when they need it to attack the ascents.
And in the same way that an old car with a one-litre petrol engine rolls down the hill just as quickly as a powerful TDI three-litre model, a relatively slow runner can match an apparently faster rival on the downhills. Those who apply their body’s ‘brakes’ on the downhills will be left for dead by fearless rivals.
At elite level, it’s often the descents rather than ascents where races are won. Indeed, at any level it can make a huge difference to your finishing time.
Take the Dolomites Sky Race in Italy: 22km in length with the first half mainly uphill and the latter half almost all downhill. Starting and finishing at 1450m altitude, the runners ascend to a peak of 3150m. In the 2016 event, just two minutes 48 seconds separated the first 10 runners in reaching the peak at 11km, after around 80 minutes of running. However, when it came to quickest 10 descents over the final 11km, the difference was three minutes, despite this being over 45 minutes, almost half the time it took for the ascent.
The right ingredients
So, what makes a good descender? Which factors are most important and how can knowing this information arm you to be better when facing the technical downhills?
When it comes to running generally, performance can be predicted relatively simply by a small handful of factors such as VO2 max and running economy. However, downhill running on the trails is much more complex. So complex in fact that a recent study to investigate the various factors involved in running downhill successfully was the first of its type.
For the scientific paper, researchers led by Grégory Doucende at the University of Perpignan assembled 28 trail runners in a lab and put them through several physical and mental tests before assessing their downhill ability. They tested visual perception, conducted muscular and proprioceptive tests and a psychological questionnaire, followed by an assessment of maximal aerobic speed on a running track.
The questionnaire consisted of 42 questions designed to ascertain the runners’ ‘telic’ dominance level, specifically to predict their attitude towards risk. The perception test assessed the athletes’ speed in pointing correctly to photocells flashing a specific symbol. To test proprioception, subjects were asked to stand as still as possible on a force platform with their eyes closed for 40 seconds, with vibration applied for half of that time. Muscular tests assessed the force, velocity and endurance capacities of lower limb muscles, while researchers also recorded maximal aerobic speed by means of something similar to what we know as the ‘bleep test’, and force velocity by means of 40-metre sprints.
On the second day, runners were timed running as quickly as possible over 1km with 255 metres of negative elevation, which included a technical section, as well as one described as more rolling. During this, scientists also analysed the percentage of rearfoot strikes for each athlete.
What they discovered is that four parameters – footstrike pattern, visual perception score, telic dominance score and rate of force development of the quadriceps – accounted for 78% of downhill running performance.
Unsurprisingly, a forefoot strike pattern was found to be better than a rearfoot action. In fact, footstrike pattern was the biggest single factor, accounting for 24.5% of descent time.
Earlier studies have found that runners with rearfoot striking have larger muscular contraction of quads, thus a greater contraction time and a reduction of efficiency. The scientists in this study also surmised that forefoot striking allowed for greater efficiency in changing direction or speed.
Visual perception was the next most important factor, at 23.7%. “High performance in trail running downhill could be related to a quick and efficient selection of information,” the researchers concluded.
Rate of force development in the quads was the third most important factor, accounting for 16.5% of the descent time. Explosive force is important for all running but particularly important when it comes to downhill. Your body exerts a great amount of force when your leg hits the ground and it’s important to avoid losing as little of that energy as possible.
The only non-physical factor – runners’ tendency to take risks – is also key, accounting for 13% of the speed. It was more important on the technical section, at 27.3%. The authors of the paper said the telic dominance score
of top trail runners is similar to that seen in extreme sports such as paragliding or climbing.
Gianluca Vernillo, an assistant professor at the University of Milan, has done much research into the biomechanics of running on hills and was intrigued to see this scientific paper.
“It is important to study the discriminants during downhill running as the results could give us important information regarding, for example, the extent of neuromuscular fatigue, training prescription and injury prevention,” he told us.
Put it into practice
The above information should greatly influence coaches and trail runners when it comes to devising training programmes; particularly, for example, consciously thinking about trying to run on your toes in training, and doing resistance work. Further, while to a great extent you are either born a risk-taker or not, training on technical downhill trails is repeatedly advised by running guides as an effective means of building confidence.
On this, Vernillo said: “Certainly a natural predisposition, both from a physiological and psychological point of view, helps. However, research thus far has shown that, among all known strategies to mitigate the negative effects of downhill running, training is the best option... After a subsequent bout of similar exercise, the neuromuscular system adapts so that it is partially protected from subsequent damaging stimuli. Therefore, training helps to develop a better tolerance to the physiological stress imposed by downhill running, but this help will undoubtedly have positive consequences on the psychological aspects of the runner. He or she will be more confident.”
So, if you find yourself picking your way down the hills in races, slamming on the brakes as others hurtle past you, it may be worth scheduling some time in your training specifically to improve on the descents. Downhills can be a free ride if you handle them correctly and a chance to save your energy for the ascents which will probably follow.
Main photo credit: Alex Gorham