KEY POINTS: This study assessed the respective contributions of haematological and skeletal muscle adaptations to any observed improvement in peak @entity26 uptake ( @entity4962 peak ) induced by endurance training (ET). @entity4962 peak , peak cardiac output (Q   peak ), blood volumes and skeletal muscle biopsies were assessed prior (pre) to and after (post) 6  weeks of ET. Following the post-ET assessment, red blood cell volume (RBCV) reverted to the pre-ET level following phlebotomy and @entity4962 peak and Q   peak were determined again. We speculated that the contribution of skeletal muscle adaptations to an ET-induced increase in @entity4962 peak could be identified when offsetting the ET-induced increase in RBCV. @entity4962 peak , Q   peak , blood volumes, skeletal muscle mitochondrial volume density and capillarization were increased after ET. Following RBCV normalization, @entity4962 peak and Q   peak reverted to pre-ET levels. These results demonstrate the predominant contribution of haematological adaptations to any increase in @entity4962 peak induced by ET. ABSTRACT: It remains unclear whether improvements in peak @entity26 uptake ( @entity4962 peak ) following endurance training (ET) are primarily determined by central and/or peripheral adaptations. Herein, we tested the hypothesis that the improvement in @entity4962 peak following 6  weeks of ET is mainly determined by haematological rather than skeletal muscle adaptations. Sixteen untrained healthy male volunteers (age  =  25      4  years, @entity4962 peak   =  3.5      0.5  l  min(-1) ) underwent supervised ET (6  weeks, 3-4 sessions per week). @entity4962 peak , peak cardiac output (Q   peak ), haemoglobin mass (Hbmass ) and blood volumes were assessed prior to and following ET. Skeletal muscle biopsies were analysed for mitochondrial volume density (MitoVD ), capillarity, fibre types and respiratory capacity (OXPHOS). After the post-ET assessment, red blood cell volume (RBCV) was re-established at the pre-ET level by phlebotomy and @entity4962 peak and Q   peak were measured again. We speculated that the contribution of skeletal muscle adaptations to the ET-induced increase in @entity4962 peak would be revealed when controlling for haematological adaptations. @entity4962 peak and Q   peak were increased (P  <  0.05) following ET (9      8 and 7      6%, respectively) and decreased (P  <  0.05) after phlebotomy (-7      7 and -10      7%). RBCV, plasma volume and Hbmass all increased (P  <  0.05) after ET (8      4, 4      6 and 6      5%). As for skeletal muscle adaptations, capillary-to-fibre ratio and total MitoVD increased (P  <  0.05) following ET (18      16 and 43      30%), but OXPHOS remained unaltered. Through stepwise multiple regression analysis, Q   peak , RBCV and Hbmass were found to be independent predictors of @entity4962 peak . In conclusion, the improvement in @entity4962 peak following 6  weeks of ET is primarily attributed to increases in Q   peak and @entity26 -carrying capacity of blood in untrained healthy young subjects.

Haematological rather than skeletal muscle adaptations contribute to the increase in peak XXXX uptake induced by moderate endurance training.

@entity26 :: ('MESH:D010100', 'Chemical') :: ['oxygen'] @entity4962 :: ('CHEBI:30046', 'Chemical') :: ['V  O2']
@entity26 :: (MESH:D010100,Chemical) :: ['oxygen']
