In elite sports, heavy training loads followed by appropriate recovery is termed overreaching and is widely used by athletes before competitions to get into peak performance. But there is a risk involved that the athlete trains too hard and performance does not bounce back the way it should. Instead of adapting to the workload, maladaptations occur and the body starts to break down. This state is termed non-functional overreaching and can develop into the more severe overtraining syndrome which can end the athletes’ career. Until now, the razor-sharp line between functional and non-functional overreaching has puzzled scientists. No clear answer has been provided behind the cellular events when the body goes from adaptation to maladaptation. In an article published in Cell Metabolism and highlighted by Nature.com, TheScientist and the New York Times, Svexa’s Chief Scientific Officer Filip Larsen and his research group find that training excessively hard with too little recovery disturbs the muscle mitochondria, deranges carbohydrate metabolism and downregulates anaerobic metabolism while halting the positive adaptations in performance.
Mysteries of overtraining starting to resolve
We used a progressive training model where we increased the amount of high intensity training week by week. And the end of each week we took muscle biopsies, measured mitochondrial function and did glucose tolerance test and thorough performance testing, says Larsen. In the beginning we saw all the classic benefits of increased training doses; better performance, more mitochondria, better metabolic flexibility etc. But after the toughest week that we like to call “Hellweek”, when athletes did daily high intensity sessions, everything just flipped; performance did not improve and the athletes could no longer produce as much lactic acid after the hard sessions. The most surprising observation was that the mitochondrial respiration was suppressed by 40% and glucose tolerance was
much worse than the week before.
We are onto something extremely interesting here, Larsen continues. If we can track this metabolic switch when athletes “goes over the edge” training wise, we are in a better position to stop them in time and thereby improve their performance.
As an additional observational study Larsen's team put continuous glucose meters, that monitors your bloods glucose level 24 hours a day, on world-class endurance athletes and a matched control group for two weeks. They found that the athletes' glucose control was worse than the control group. The athletes had episodes of low blood glucose during the night and had higher glucose levels in the early afternoon.
We don’t really think that all the world-class athletes were overtraining, but tracking your glucose levels can be fundamental for recovery. If your blood glucose drops to low levels at night this will affect both your sleep quality and recovery levels. We are experimenting with different dietary strategies right now, such as late evening snacks with slow-release carbohydrates to keep the blood glucose levels stable during night, Larsen says.
FIlip is Associate Professor, Swedish School of Sports & Health Sciences, and a Physiologist for Swedish National Orienteering Team.