This Winter in Journals, Part Two: Skis and Boots, Injuries and Eating

Welcome back to This Month in Journals! After taking the winter off to focus on race reporting, we’re doing a series to catch up on the ski-related research that has been published in scientific and social science journals this winter.

* In the journal Sports Engineering, five researchers from Trondheim, Norway, reported having built an “instrumented rollerski.”

Come again?

The team built full bridge strain gauges into the shaft of the rollerskis so that they could measure force while a skier trained on a treadmill. A wireless sensor picked up the information and transmitted to a base station via a radio transmitter. They also used a motion-capture system to track the rollerski’s position in three-dimensional space.

That allowed them to be able to detect differences in technique between two skiers, or for instance between the same skier when he was skating with and without poles. The researchers hope that the system will allow better work on ski technique – but they wrote that a few adjustments still had to be made to the system.

* Meanwhile in Austria, researchers were focusing on boots.

“Ski boot quality is determined by mechanical properties and comfort,” Dr. Patrick Hofer and four coauthors wrote in their abstract in Applied Ergonomics. “Comfort is strongly affected by cold feet.”

Point taken. The group set out to determine the “microclimate” in ski boots: temperature, humidity, and how much water the boots absorbed. They asked five skiers to participate in their study, using two different brands of alpine ski boots. The men went into a climate chamber set at various temperatures and simulated skiing (rounds of squats, followed by rests so simulate riding on a chairlift); two of the men also did field tests.

The ski boots were outfitted with sensors to detect the temperature and humidity. After the simulation was done, the wetness of the boot liner was measured by weighing it on a scale and seeing how much water weight it had gained.

Alpine boots are completely different than cross-country ski boots, but some of the researchers’ conclusions are still quite valid for our community. Because there are no large muscles in the foot, feet are kept warm only by blood flow. That means that once boots (and feet) start to get cold, they just keep going. In every case, the temperature in the boots declined once the skiing began.

The men began saying that their feet were cold and hurt when their toes reached about 20ºC (68ºF), or when they were about 5ºC colder than the main part of the foot (toes and feet had different sensors). The coldest temperature any of the mens’ toes reached was 11ºC (52ºCF), at which point he said his toes were numb.

The researchers also found that ski boots got far wetter in the field than in the climate chamber (duh) and noted that although boots have good insulation, when they are exposed to snow and get wet, that insulation doesn’t work as well.

In order to keep feet from getting cold – important! – the researchers said that boots would probably have to be built with different materials and maybe even different designs.

* Other researchers were studying the health effects of sports. The American Medical Society for Sports Medicine published a position statement in the British Journal of Sports Medicine about overuse injuries and burnout in youth sports. Noting a culture pushing children towards excellence at younger and younger ages, the panel gave an overview of possible effects with the aim of helping doctors identify young athletes at risk.

Among the consequences of heavier training loads for young athletes, they discussed that:

• overuse injuries are most likely to occur during the adolescent growth spurt
• prior injury is the biggest risk factor for developing an overuse injury
• growth cartilage may be particularly susceptible to repetitive stress
• early “sport specialization” increases injury and burnout; participating in a diverse array of sports should be encouraged early in a child’s athletic “career”
• scheduled rest periods are essential in maintaining a physically and mentally healthy relationship to sport
• emphasis should be placed on skill development and correct technique, not just competition
• pressure from family and peers is discouraged
• the female athlete triad places girls at increased risk of injury

* While we’re on the subject of the female athlete triad…. Two other research groups addressed the phenomenon. Defined as a combination of disordered eating and irregular menstrual cycles, which eventually through hormonal effects can lead to decreased bone density, the triad, also sometimes referred to as relative energy deficiency syndrome, is assumed to be common in female athletes.

Not all three symptoms have to be present for a woman’s health to be affected. Even without disordered eating, for example, a female athlete can be taking in few enough calories to stress daily body function, at which point reproductive functioning is diminished. Regardless, reducing the energy deficiency – that is, making sure an athlete is taking in more calories than they are burning – can solve a lot of the problems.

The IOC put out a consensus statement pointing out that male athletes are also affected, although few studies have examined to what extent. In any case, the IOC listed the potential effects of relative energy deficiency: decreases in metabolic rate, menstrual function, bone health, immunity, protein synthesis, and cardiovascular health. Because of these risks, which can have long-term consequences, it is important to remedy the symptoms of the triad.

The group called for better clinical approaches to dealing with the syndrome, and suggested dividing athletes into three categories, each with different treatment plans in relation to when they should be allowed to return to sport.

Low-risk athlete should be encouraged to play their sport full-time, with an emphasis on healthy eating. Medium-risk athletes should be placed on a training plan and diet plan, and allowed to train if they follow these plans; they can be cleared for competition by their doctor. For high-risk athletes, competition should not be allowed, and only minimal training under supervision.

The statement was published in the British Journal of Sports Medicine, which also published a paper by a group of Scandinavian researchers who developed a questionnaire to determine whether athletes are affected by the triad. Consisting of 25 questions, validation showed that the survey was effective in identifying female athletes who showed signs of the triad. The researchers suggested that such a questionnaire (called LEAF-Q) be used for early detection of the triad so that female athletes could change their habits before the effects became more serious.