UNASSIGNED: Research has shown that total @entity251 (tT) levels in @entity1 increase acutely during a prolonged bout of aerobic exercise. Few studies, however, have considered the impact of the menstrual cycle phase on this response or have looked at the biologically active free @entity251 (fT) form responses. Therefore, this study examined the fT concentration response independently and as a percentage (fT%) of tT to prolonged aerobic exercise during phases of the menstrual cycle with low @entity172 - @entity1420 (L-EP; i.e., follicular phase) and high @entity172 - @entity1420 ( @entity8108 -EP; i.e., luteal phase). Ten healthy, recreationally trained, eumennorrheic @entity1 (X    SD: age = 20    2 y, mass = 58.7    8.3 kg, body fat = 22.3    4.9 %, VO2max = 50.7    9.0 ml/kg/min) participated in a laboratory based study and completed a 60-minute treadmill run during the L-EP and @entity8108 -EP menstrual phases at ~70% of VO2max. Blood was drawn prior to (PRE), immediately after (POST) and following 30 minutes of recovery (30POST) with each 60-minute run. During @entity8108 -EP, there was a significant increase in fT concentrations from PRE to POST (p < 0.01) while in L-EP fT levels were unchanged; which resulted in fT being significantly higher at @entity8108 -EP POST versus L-EP POST (p < 0.03). Area-under-the-curve (AUC) responses were calculated, for fT the total AUC was greater in @entity8108 -EP than L-EP (p < 0.04). There was no significant interaction of fT% between phases and exercise sampling time. There was, however, a main effect for exercise where fT% POST was a greater proportion of tT than at PRE (p < 0.01). In summary, hormonal changes associated with the menstrual cycle impact fT response to a prolonged aerobic exercise bout; specifically, there being higher levels under @entity8108 -EP conditions. This suggests more biologically active T is available during exercise in this phase. This response may be a function of the higher core temperatures found with @entity8108 -EP causing greater sex hormone binding protein release of T, or could be a function of greater degrees of glandular production. Further work is warranted to elucidate the mechanism of this occurrence. It is recommended that researchers examining T responses to exercise in @entity1 look at both tT and fT forms in order to have an accurate endocrine assessment in @entity1 .

Menstrual cycle phase effects free XXXX responses to prolonged aerobic exercise.

@entity1 :: ('9606', 'Species') :: ['women'] @entity172 :: ('MESH:D004967', 'Chemical') :: ['estrogen'] @entity251 :: ('MESH:D013739', 'Chemical') :: ['testosterone'] @entity1420 :: ('MESH:D011374', 'Chemical') :: ['progesterone'] @entity8108 :: ('D006859', 'Chemical') :: ['H']
@entity251 :: (MESH:D013739,Chemical) :: ['testosterone']
