Extended periods of intense training without adequate recovery may compromise bone health, according to a study in elite rowers.
Typically, bone mineral density — an indicator of bone strength — increases with regular exercise, acting as a protective mechanism against bone fractures and osteoporosis.
But researchers from Brock University and the Canadian Sports Institute of Ontario found that the extended, high-intensity training sessions of elite athletes could reverse beneficial bone changes.
The research team spent nine months monitoring changes in osteoprotegerin (OPG, a protein that stops bone mineral loss) and sclerostin (SOST, a protein that inhibits new bone formation) levels in female rowers who were training for the 2016 Olympic Games.
This group of athletes were chosen because they often have a “high incidence of stress fractures and are at risk of [bone mineral density] loss,” explained Nigel Kurgan, first author of the study.
Reporting on the study, the American Physiological Society said that the amount of training done by the rowers varied, but averaged about 18 hours per week. OPG — measured through blood samples — significantly decreased during the study period, suggesting that the athletes were at risk for bone loss. SOST levels fluctuated, with the highest levels corresponding with the highest training volume and the lowest occurring when training volume was lower. Inflammation in the body also increased with more training and this is thought to increase the expression of SOST, Kurgan said.
To assess bone mineral density, the researchers used dual X-ray absorptiometry imaging before and after the study period and this revealed no change. However, the fact that OPG and SOST expression changed significantly during heavy training may serve as a warning that “very intense training without adequate recovery period may lead to increased inflammation and subsequent bone resorption (loss),” Kurgan wrote.
The findings were presented at last month’s Experimental Biology 2017 meeting in Chicago, and have been published in The FASEB Journal.