Glycogen-depleted training improves performance without sacrificing immunity

New research suggests that glycogen-depleted training improves your triathlon performance without sacrificing your immunity…

The Bastion at Hever Castle

We first came across sports scientist Laurie-Anne Marquet of the French National Institute of Sport and Physical Education (INSEP) at last year’s annual International Triathlon Union Science and Triathlon Conference in Paris.


There Marquet presented her research on glycogen-depleted training, and was one of the few practitioners to actually show a performance improvement as well as the accepted physiological benefits that include improved fat-burning.

Now Marquet is back and evolving the idea of glycogen-depleted training by focusing on the potential impact on immune function.

“While the results of the last study proved favourable, clearly this type of training is physiologically stressful,” Marquet explains about the research. 

“Any physiological stress, if not complemented by both good nutrition and quality sleep, can decrease immune function and increase the chances of illness or injury.”

Several ‘training low’ strategies are used by endurance athletes. For instance, swim, bike or running 6-10hrs after their last meal; training twice per day where the second session is with reduced glycogen stores; or restricting carbohydrate intake during the recovery period after exercise.

Marquet, along with the likes of John Hawley of the Australian Catholic University, have focused on the concept of ‘sleeping low’, which comprises high-intensity training followed by an overnight fast and then another low-intensity training session in the morning to accentuate the glycogen depletion.

Marquet applied this fasting template to assess the impact on immunity of one group of triathletes, while the other followed a normal diet. The ‘depleted’ group undertook a pretty extreme nine twice-a-day sessions with lowered glycogen levels, while the control group followed the same training plan but with full glycogen levels.

The athletes undertook 10km running tests before and after the three-week period, with sleep quality and quantity measured every night. Blood and saliva tests were taken pre, during and post to measure immune function, while incidence of URTI (upper-respiratory tract infection) was also recorded.

“The results were very positive,” says Marquet. “Like my previous study, the glycogen-depleted group significantly improved their 10km running time. But, importantly, there were no significant changes in white blood cell counts or plasma cortisol – both parameters of immune function. 

“The incidence of URTI was also not altered in the groups,” she adds, “though in both vitamin D was down.”


  • This is for experienced or very fit triathletes only. Even then, don’t follow the template of high-intensity training, followed by glycogen-depleted sleep and low-intensity morning training more than once a week.
  • Ensure that you maintain a carbohydrate intake throughout both days of around 6g/kg bodyweight.
  • Vitamin D strengthens the immune system but is depleted through exercise. The sun is the greatest source of vitamin D, which is why a daily supplement is recommended through the winter months.