FasterSkier is starting a once-a-month series looking at new research in the field of sports science. Periodically, we’ll flip through some of the world’s best peer-reviewed medical journals and summarize, in plain English, studies that we think will be of interest to skiers. Here’s our second installment; you can check out the first here.
* Compartment syndrome, the compression of muscles with in a myofascial “compartment,” is prevalent though it has become in cross-country skiing, but is not a well-understood disease. Drs. Andrew Roberts and Andrew Franklyn-Miller of Surrey, England, admit as much in a recent paper in the Scandinavian Journal of Medicine and Science in Sports.
“The pathophysiology of the condition is poorly understood, and the criteria used to make the diagnosis are based on small sample sizes of symptomatic patients,” they write.
Chronic exertional compartment syndrome, or CECS, can’t be diagnosed just by MRI’s or other non-invasive means. Instead, doctors typically cut a slit in the skin and insert a catheter (in some cases a fluid-filled needle) into the muscle, then ask the patient to exercise on a treadmill or bike and measure how the pressure in the muscle changes from rest to exercise.
CECS also usually can’t be cured simply by resting or doing physiotherapy. Typically, skiers (and other athletes) with bad cases of CECS have surgery to remove the fascia, or coating, around the affected muscles in their calves or shins so that they can expand without causing pain.
Nobody wants to have surgery that they don’t need, so it’s troubling that there doesn’t seem to be a quick and easy diagnosis. Drs. Roberts and Franklyn-Miller examined the use of intramuscular pressures to assess the technique’s accuracy. Even before starting their literature review, they knew that some of the studies which were used to set the cutoff values defining CECS had failed to use a control group of healthy subjects.
So, the pair set out in search of studies that would give them some baseline information. And what they found was troubling: when researchers actually look at intramuscular pressure in healthy people, the values are sometimes above the cutoff currently used to diagnose CECS.
“If a measured [intramuscular pressure] is above the criteria, clinicians can not have confidence as to whether the subject belongs to the upper end of the distribution curve for healthy subjects or at the lower end of the curve for subjects with CECS,” the authors wrote.
Furthermore, they found that factors such as how deep the catheter was inserted and its position in the muscle, as well as which activity the patient was doing and even shoe shape contributed to variation in measurements of intramuscular pressure. The authors called the intramuscular pressure method “flawed” and wrote that they would not recommend it as a mode of diagnosis.
“The [intramuscular pressure] at all the gold-standard time points has shown to be dependent on variables other than the presence or absence of CECS, and considerable overlap exists in the available literature between normal and symptomatic subjects in IMP measurement,” Robers and Franklyn-Miller wrote. “The current diagnostic criteria certainly cannot be applied with reliable certainty… These flaws could potentially lead to false positives and subsequent fasciotomy where it is not indicated.”
Among other things, the authors suggested that rest and conservative treatments be tried before jumping to surgery. For instance, the fact that shoe shape and construction could determine intramuscular pressure dictates that athletes might want to change their footwear – several times – before going under the knife and losing weeks or months of training. The takeaway message for skiers is not to jump to conclusions when their calves and shins start hurting – and that if pain isn’t severe, having high measured intramuscular pressure doesn’t mean that it’s compartment syndrome.
* In Acta Physiologica, both an editorial by Dr. Timothy Carroll of the University of Queensland and a paper by researchers from Deakin University in Melbourne argue that a large part of an athlete’s improvement in strength can be tied to adaptations in their brains, not just the muscles themselves.
The Deakin team, led by Dr. Dawson Kidgell and his graduate student Ashleigh Weier, began from the pattern that athletes generally see improvements in strength very early on in a training program, before their muscles actually get significantly bigger. To examine whether the improvements might be all in their heads, the team used transcranial magnetic stimulation: they sent of magnetic pulses through a subjects head, which then gave them information about synaptic activity and possible inhibitions.
Briefly, the magnetic pulse technique has been used many times before to examine how the brain controls performance of many tasks, including strength training – where results have been conflicting and inconclusive. The Deakin team took a slightly different approach of comparing single-pulse with paired-pulse stimulations.
After four weeks of training, university students improved their squats significantly but did not develop thicker muscles compared to a control group. More importantly, the study showed an adaptation to training: the students who had been training showed changes in the motor cortex that led them to perform better.
The editorial further hypothesized that, compared to other studies, the more complex a task is, the larger the magnitude of change in the cortex will be. Because the maximum-load squats were both taxing and required very specific technique combining multiple muscle and joint movements, the brain changed more to facilitate the difficult task.
“It seems likely that repetitive muscle actions against high loads alter motor cortical connectivity to facilitate the specific patterns of muscle activity required to produce maximal force in the training context,” Carroll wrote.
Training: maybe it really is mind over matter….
* The International Olympic Committee published its consensus statement on thermoregulation and altitude adjustment this month in the British Journal of Sports Medicine. In short, the IOC wants to make sure that environmental conditions don’t adversely affect the health of its athletes. As examples of some conditions they want to control, they listed heat, cold, wind, altitude, and humidity.
The group, anchored by Dr. Lars Engebretsen of the University of Oslo, noted that it was difficult to set hard-and-fast criteria for conditions given that each sport – summer to winter, from land to water – encountered different challenges.
In terms of challenges relevant to nordic sports, the IOC started by writing off hypothermia: “And while some Nordic skiing and biathlon events require 2 h to complete, metabolic heat production during these activities is even higher, often reaching 13–18 METS (1250–1800 W)… these very high-metabolic rates will offset heat loss and prevent athletes from developing hypothermia during competition in conditions typifying the past three winter Olympics, and probably even with much more extreme cold conditions.”
It’s worth noting, however, that the group used as its guidelines only the temperatures from the last three winter Olympics – including, for example, the rather warm Vancouver edition. They wrote that air temperature would have to be below -4° F – the technical cutoff for FIS-sanctioned races – for nordic athletes to get frostbite, and suggested that it was more a concern to worry about coaches, volunteers, and support staff.
The group went on to note the prevalence of exercise-induced asthma and bronchial hyper-responsiveness in elite skiers and swimmers. “Furthermore,” the authors wrote, “participation in competitive cross-country skiing over a winter season markedly enhanced airway infl ammation in bronchial biopsies in young skiers with and without asthma.”
What to do? The IOC helpfully recommends recording temperature and wind speed at events and telling athletes to wear warm, windblocking clothes when training. and notes that inhaled steroids can treat asthma without being performance-enhancing and warned against over-using beta-2 agonists (read more about that issue in our piece from last week).
While the consensus statement itself was based on many previously published studies and revealed little that was new or exciting, it did provide a pulling-together of the IOC’s thoughts on many medical issues. And perhaps the group failed to make any bold statements because they are waiting on more results from researchers around the world: the piece closed with a call for more work to be done.
“We urge the Commission and Federations leaders to assertively and openly press further in their pursuit to better appreciate, closely monitor and appropriately respond to the health and safety challenges in all sport venues, so every Olympic and international-level athlete is adequately protected and thus given the opportunity to demonstrate optimal athletic performance,” the group wrote.
