Introduction - Three week stage races in cycling, such as Tour de France, Giro d’Italia and Vuelta a Espana, probably rank amongst the most strenuous athletic performances in elite sports. Weight impact on bones is essential for maintenance of bone health and strength. Because cycling is a non-weight-bearing activity, professional cyclists often have even lower bone density than non-active peers.
Methods - In this regard, Lombardi and his co-workers investigated bone and energy metabolism parameters in nine pro cyclists from the Liquigas-Cannondale team during the Giro d’Italia from May 8th to May 29th 2011. Throughout the Giro their diet was strictly controlled to supply 6000 kcal per day (45% carbohydrates, 36% protein and 19% lipids), while their energy expenditure was calculated from power outputs measured during the stages (SRM GmbH, Germany) plus standard metabolic rates during rest and sleeping time. Furthermore, blood samples for hormonal analyses were collected before the start of the Giro, and in early morning of stages 11 and 20.
Results - From the start to the end of the Giro the cyclists on average lost ~1.7 kg body weight, indicating that 6000 kcal per day was not enough to match the energy expenditure of the riders. However, in major stage races such imbalance is rather common because the drive to eat is often impaired due to accumulation of fatigue, loss of appetite, and increasing symptoms of gastrointestinal distress, especially following stages in the heat. Hormonal markers of bone metabolism clearly pinpointed an imbalance in bone metabolic activity towards bone resorption, which may eventually result in breakdown of bone mineral mass. Accordingly, the authors also found a drop of plasma total osteocalcin levels, which provides additional evidence to indicate that the Giro created a catabolic state leading to deterioration of bone health. In fact, the catabolic state was not specific for bone metabolism. Also circulating levels of some other important hormones such as testosterone, cortisol and leptin dropped during the Giro. This indicates that stage races also disable the capacity of the human body to maintain a healthy hormonal profile.
Conclusion – Three week stage races in cycling induce a metabolic condition that may result in regression of bone health. Therefore, it is recommended that cyclists involved in extreme cycling combined with severe dietary energy restriction to reduce body weight, take adequate measures in training and diet to counteract the potential drain of bone mass induced by stage races.
Lombardi G, Lanteri P, Graziani R, Colombini A, Banfi G, Corsetti R. (2012) Bone and energy metabolism parameters in professional cyclists during the Giro d’Italia 3-weesk stage race. PLoS ONE 7(7): e42077