This Month in Journals: VO2Max is Stable, Heart Rate Isn’t, and How to Dope Your Brain

Welcome back to This Month in Journals, where we read the latest exercise and sports science and pull out some research that might be of interest to skiers.

* Junior, college, and elite skiers often face test after test on a treadmill or double-poling machine, to measure physiological improvements and chase an increase in VO2Max, maximal oxygen uptake. But over the course of a training year, how much change can an athlete really expect to see?

Curious, a team of researchers from the Norwegian School of Sport Sciences in Oslo tracked 13 elite male skiers for a year and asked them to perform five different 1,000-meter tests on a rollerski treadmill. The skiers – some of whom had top-15 World Cup finishes that season – otherwise followed their normal training programs, but made sure to come by for tests during summer and fall training, once during the season, and once the following June as training was just starting up again in earnest.

Earlier hypotheses had suggested that VO2Max changes throughout the year, and the best skiers are the ones that can improve theirs the most by the time competition season rolls around, while the rest are stuck with the same capacity they had in summer training. But writing in the Journal of Strength and Conditioning Research, Thomas Losnegard and colleagues found that VO2Max did not change significantly over the course of a season.

The authors conclude, in agreement with research in cycling, that the time when VO2Max can best be developed is during puberty and the teen years, and after a certain volume of training is reached, the capacity has been reached and will no longer expand. “In high-level athletes, V̇O2Max may have reached their maximal genetic potential after many yearsof training and further increase may be difficult or even impossible, despite the increase in [High Intensity Training] during the season,” they write.

However, the results did not show a complete lack of physiological improvement. The actual times to complete the 1,000 meter test dropped, as did oxygen cost (the amount of energy used, roughly) and oxygen deficit (a measure of the anaerobic system). The takeaway? When looking at test results, athletes may be improving dramatically even if that seemingly-magic V̇O2Max number stays the same. Other parameters may be more useful in assessing athlete trajectories over the course of a season.

* Writing in the journal Sports Medicine, Nick Davis of Bangor University in Britain reviews a new performance-enhancing technique which he deems “neurodoping.” While no drugs are involved, Davis concludes that brain stimulation may lead to improvements in performance just as large as chemically-induced ones, and wonders if this can be regulated.

Currently, there are two main techniques for neurodoping. The first is transcranial magnetic stimulation (TMS), where magnetic pulses are sent towards the brain by a stimulating coil. Place the coil on the head and voila! The brain cells nearest to the center of the coil will fire.

The second technique is transcranial current simulation (tCS), where a current is passed from a negative electrode to a positive electrode, spreading an electric field across the entire brain surface. (Editor’s note: both of these things sound terrifying.)

In both cases, effects can last ten or thirty minutes or more after the stimulation ends, and subjects show better motor skills, response time, and take longer to fatigue during this time. Athletes could spend some their last few minutes before setting out of the start gate getting brain stimulation, and likely perform better. The techniques could also be used during training, as tCS has been shown to help subjects learn skills faster.

Davis is unsure whether all of this would apply to elite athletes, who of course are quite different than the average, untrained study participants used by most researchers. There has been no research into what “doses” of stimulation would be ideal in different athletic situations. Furthermore, there is no way to detect whether someone has undergone one of these stimulation techniques.

So should they be considered doping? Davis suggests that each sport consider whether the technique is in disagreement with its “ethos.”

“There is clearly an important exchange between people who wish to improve skills in sport and those who wish to rehabilitate motor function after brain injury or physical trauma,” he writes. “I would urge researchers to be more explicit about this dialogue.”

* But back to cross country skiers. The question of how to detect fatigue is a perplexing one for endurance athletes: if someone says they are tired, are they? How tired is too tired, depending on the period of training? Are they getting sick? Is this part of the plan and they must just push through?

Morning heart rate has been considered a useful indicator of health and fatigue for years. If it suddenly goes up, then something is going on – the athlete is likely sick or tired. But that doesn’t solve the problem of how to distinguish regular, planned fatigue from overtraining.

A large group of French scientists thought that a different aspect of the heart beat might be the answer: heart rate variability (HRV), or the amount of difference in timing between heartbeats over some period of time, say a minute or two. To examine their hunch, they enlisted 57 members of the French national teams in cross country, biathlon, and nordic combined, and followed them for four years, periodically performing HRV tests.

When they did so, they would also give the athletes a questionnaire to determine how tired they were. If they said “yes” to more than 20 of the 54 items, then they were deemed to be in a “fatigue” state. Each athlete was fatigued for at least a few of the tests, and comparisons were made between that and a normal state for each athlete.

Laurent Schmitt and the team reported in Plos One that not only were heart rates eight to ten beats higher both standing and lying down when athletes were fatigued, but HRV parameters were lower. There was large variation between and among athletes, suggesting multiple ways that the body is stressed and/or copes with exhaustion, but the authors still believed that HRV may be a useful way to detect fatigue. It is less invasive and time consuming than most biological methods, which rely on blood or urine tests to look at hormones or other chemicals in the body. However, they write that more research is necessary to determine whether HRV can help distinguish a high fatigue level from complete overtraining.