The World Anti-Doping Agency prohibit glucocorticoid (GC) administration during competition but allow administration in periods out of competition. However, GC administration may accelerate erythropoiesis and resemble blood volume manipulation methods, which are prohibited at all times. Here, we investigated whether a single GC injection accelerate erythropoiesis, increase total hemoglobin mass (Hb_mass ) and improve exercise performance. 

In a randomized, double-blinded, placebo-controlled crossover design (3-month washout), eight trained males (maximal oxygen uptake 60±5 ml O2 ·min^-1 ·kg^-1 ) were injected with 40 mg triamcinolone acetonide (GC group) or saline (PLA group) in the gluteal muscles. Venous blood samples collected before and 7-10h, 1, 3, 7, 14 and 21 days after treatment were analyzed for [Hb] and reticulocyte percentage (ret%). Hb_mass and mean power output in a 450-kCal time trial was measured before as well as one and three weeks after treatment. 

A 27±28% and 54±41% higher ret% was evident three (P<0.01) and seven (P<0.001) days after the GC administration, respectively, compared with PLA, whereas [Hb] was similar between groups. Additionally, Hb_mass was 20±28g higher (P<0.05) one week after GC administration compared with PLA, but similar after three weeks. The mean power output was similar between groups one (GC: 285±70 W, PLA: 279±69 W) and three (GC: 279±72 W, PLA: 276±71 W) weeks after treatment. 

In conclusion, a single intramuscular injection of triamcinolone acetonide was sufficient to accelerate erythropoiesis and increase Hb_mass, but did not translate into improved aerobic exercise performance in the present study. Future research should confirm whether anti-doping authorities should consider glucocorticoid injections as a method of blood volume manipulation.