ABSTRACT INTRODUCTION AND OBJECTIVE:Delta efficiency (DE) and oxygen uptake kinetics (K<img src="/img/revistas/rbme/v17n4/en_a13cr01.jpg" align="absmiddle" />2) are influenced by muscle metabolic parameters and oxygen transport. The aim of this study was to determine the difference in DE and K<img src="/img/revistas/rbme/v17n4/en_a13cr01.jpg" align="absmiddle" />2 in three effort intensities in both genders. METHODS: Fifty-six subjects (26 women) were submitted to a graded maximal exercise test (GXT) on cycle ergometer to determine the maximum oxygen uptake ( <img src="/img/revistas/rbme/v17n4/en_a13cr01.jpg" align="absmiddle" />2max ), maximal power output (Wmax), anaerobic threshold (AT) and respiratory compensation point (RCP). The AT and RCP were determined using the V-slope and <img src="/img/revistas/rbme/v17n4/en_a13cr02.jpg" align="absmiddle" />E / <img src="/img/revistas/rbme/v17n4/en_a13cr01.jpg" align="absmiddle" />2 methods; the RCP using the relationship <img src="/img/revistas/rbme/v17n4/en_a13cr01.jpg" align="absmiddle" />2versus <img src="/img/revistas/rbme/v17n4/en_a13cr02.jpg" align="absmiddle" />E both by two investigators. The DE and K<img src="/img/revistas/rbme/v17n4/en_a13cr01.jpg" align="absmiddle" />2 have been considered as a slope between <img src="/img/revistas/rbme/v17n4/en_a13cr01.jpg" align="absmiddle" />2versus Watts and <img src="/img/revistas/rbme/v17n4/en_a13cr01.jpg" align="absmiddle" />2versus time (s), respectively, from the beginning of test until AT (S1), from AT to RCP (S2) and from RCP to <img src="/img/revistas/rbme/v17n4/en_a13cr01.jpg" align="absmiddle" />2max (S3), determined by linear regression analysis. RESULTS: Regarding DE, significant differences were observed between S1 versus S2 (p = 0.001), S1 versus S3 (p = 0.001) and S2 versus S3 (p = 0.006). There was no significant difference (p = 0.060) or interaction (p = 0.062) between men and women. For K<img src="/img/revistas/rbme/v17n4/en_a13cr01.jpg" align="absmiddle" />2, significant differences were observed between S1 versus S3 (p = 0.001) and S2 versus S3 (p = 0.001) in both genders. Significant differences (p = 0.001) and interaction (p = 0.006) were observed between men and women, in the last parameter. CONCLUSIONS: DE decreases with increasing intensity of power output, but there are no differences when comparing men and women. On the other hand, women present faster K<img src="/img/revistas/rbme/v17n4/en_a13cr01.jpg" align="absmiddle" />2than men
ergospirometry; effort test; <img border=0 src="../../../../../img/revistas/rbme/v17n4/a13cr01.jpg" align=absmiddle />2 e <img border=0 src="../../../../../img/revistas/rbme/v17n4/a13cr01.jpg" align=absmiddle />2máx slow component
