Dear Editor-in-Chief: In response to Prof. Kuipers' concerns regarding our study (2), very few studies have been carried out on glucocorticoid (GC) administration, exercise performance, and inconsistencies found regarding the ergogenic effect of GC administration in humans that may be attribute to the dosage, route, mode of administration (acute/short term), and intensity of exercise. To our knowledge, there is no published study testing the ergogenic effects of therapeutic GC inhalation. Probably, such local low-dose administration will fail to improve performance in view of the lack of significant systemic bioavailability. The mode of administration also appears to be a key factor. Indeed, no study has yet demonstrated any ergogenic effect after acute systemic ACTH or GC administration, whatever the exercise intensity performed: 70-75% V˙O2max (3), 80-85% V˙O2max (1), or maximal exercise (6). It may, however, be considered that an ergogenic effect of acute GC administration may occur after higher administration. Short-term dexamethasone intake did not modify performance during a classical incremental V˙O2max test (5), although, contrary to acute intake, we found a significant improvement at 70-75% V˙O2max (80-85% V˙O2max was not tested) in healthy, recreationally trained men after short-term prednisolone treatment both with (4) and without (2) combined intense training. We completely agree with Prof. Kuipers and Dr. Pluim that the performance improvement obtained after short-term GC administration is directly linked to our choice of a submaximal exercise. Indeed, we have suggested that the speculative mechanisms proposed for an eventual performance gain after GC intake may require exercise for a relatively long duration. Regarding Article 25 of the UNESCO International Convention on the Fight against Doping (7): "When promoting anti-doping research… States parties shall ensure that such research will: … b) Avoid the administration to athletes of prohibited substances and methods; c) Be undertaken only with adequate precautions in place to prevent the results of anti-doping research being misused and applied for doping." We are not authorized in our country to administer doping substances to elite athletes. Therefore, we have adapted the exercise intensity to the physical status of our recreationally trained subjects that can be maintained under placebo for at least 30-40 min before exhaustion. However, it is obvious that elite endurance athletes are able to maintain much higher exercise intensities for hours. As mentioned in our conclusion, it appears necessary to verify whether elite athletes are less (or perhaps more, as we hypothesized in our last paper) sensitive to the ergogenic effects of GC than recreationally trained subjects, but we completely refute the formulation used by Prof. Kuipers: "…this study is the first that showed an ergogenic effect of corticosteroid administration … this is only true for endurance time at an exercise intensity ≤ 75% of V˙O2max." Katia Collomp, PharmD, PhD Dr. Alexandre Arlettaz, PhD LAPSEP Faculty of Sports Science University Orléans Orléans, France