Energy Metabolism, Muscular Damage And Cytokine Changes During Giro D’Italia 3-Week Stage Race

Objective:To further understand characteristics of exercise demands and metabolic load and physiological stress responses, adaptations and relationships in professional 3-week stage race through investigating actual power output, energy expenditure and the behavior and relationships of serum metabolic markers, muscular damage markers and cytokines in Giro d’Italia.Methods:Nine professional road cyclists from the same team were recruited in 2013 Giro d’Italia 3-week stage race. Power output (PO) and energy expenditure were measured by SRM power meter and blood samples were collected on the day before the start of the race (T1), day 10 (T2) and day 23 (T3). Serum muscular damage markers, metabolic markers and inflammatory cytokines were also tested and analyzed together with corrected values by plasma volume change (ΔPV) during the race. Correlation analysis was also performed among parameters forementioned.Results:SRM data showed that ITT had the highest PO followed by HMS and MMS which had the most energy expenditure. Although FS had the lowest P0, Mean Maximal Power Output in 15 seconds was the highest in FS. For Hematological parameters, Hb and Hct significantly decreased during the entire course of race and correlated to P0, however, there was a significant increase trend at T3 compared to T2. Besides, an obvious plasma volume expansion was found during the race and furthermore, parameters showed obvious differences after being corrected by ΔPV. For muscular damage markers, CK and LDH increased significantly during the race, but there was a significant decrease trend at T3 compared to T2 for CK and LDH. Mb and ALD only significantly increased at T2 and recovered to normal level at T3. For auxiliary parameters of muscular damage, AST and ALT increased signifi canty at T2 and stabilized in the second part. A significant correlation between CK and PO was also found. For metabolic markers, blood glucose and urea significantly increased during the race, while Insulin and C-peptide only showed significant increase at T3. TC, TG and LDL-C were significantly lowered at T2 but all showed a significant increase trend at T3 compared to T2, among which LDL-C was still significantly lower than the prerace basal level at T1. Significant correlations were also found between LDL-C and muscular damage markers. On the contrary, HDL-C significantly increased during the entire course of the race, while showed an obvious decrease trend at T3 compared to T2. Proinflammatory cytokines IL-1β and IL-12 were significantly increased at T2 but all recovered to prerace basal level at T3. TRAIL and IL-8 showed a non-significant increase at T2, while they showed a significant decrease trend at T3 compared to T2. TNF-α, IFN-γ, IL-2, IL-6, IL-1Ra, IL-4, IL-10 and IL-13 showed no significant difference during the entire race. Acute phase protein CRP significantly increased during the race.Conclusions:(1)In Giro d’Italia, different types of stages had obviously different power output and energy expenditure characteristics, while similar exercise intensities and metabolic demands of the same type of stage were found as those reported in Tour de France; (2) The behavior of hematological parameters, muscular damage markers, metabolic markers and cytokines reflected the stress responses, adaptations and mutual relationships of physiological functions in professional 3-week stage race.