Montero 2015 J Physiol
|Montero D, Cathomen A, Jacobs RA, Flück D, de Leur J, Keiser S, Bonne T, Kirk N, Lundby AK, Lundby C (2015) Haematological rather than skeletal muscle adaptations contribute to the increase in peak oxygen uptake induced by moderate endurance training. J Physiol 593:4677-88.|
Abstract: KEY POINTS: This study assessed the respective contributions of haematological and skeletal muscle adaptations to any observed improvement in peak oxygen uptake (VO2 peak ) induced by endurance training (ET). VO2 peak , peak cardiac output (Q̇ 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 VO2 peak and Q̇ peak were determined again. We speculated that the contribution of skeletal muscle adaptations to an ET-induced increase in VO2 peak could be identified when offsetting the ET-induced increase in RBCV. VO2 peak , Q̇ peak , blood volumes, skeletal muscle mitochondrial volume density and capillarization were increased after ET. Following RBCV normalization, VO2 peak and Q̇ peak reverted to pre-ET levels. These results demonstrate the predominant contribution of haematological adaptations to any increase in VO2 peak induced by ET.
ABSTRACT: It remains unclear whether improvements in peak oxygen uptake (V̇O2 peak ) following endurance training (ET) are primarily determined by central and/or peripheral adaptations. Herein, we tested the hypothesis that the improvement in V̇O2 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, V̇O2 peak = 3.5 ± 0.5 l min-1 ) underwent supervised ET (6 weeks, 3-4 sessions per week). V̇O2 peak , peak cardiac output (Q̇ 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 V̇O2 peak and Q̇ peak were measured again. We speculated that the contribution of skeletal muscle adaptations to the ET-induced increase in V̇O2 peak would be revealed when controlling for haematological adaptations. V̇O2 peak and Q̇ 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, Q̇ peak , RBCV and Hbmass were found to be independent predictors of V̇O2 peak . In conclusion, the improvement in V̇O2 peak following 6 weeks of ET is primarily attributed to increases in Q̇ peak and oxygen-carrying capacity of blood in untrained healthy young subjects.
Labels: MiParea: Respiration, Exercise physiology;nutrition;life style
Organism: Human Tissue;cell: Skeletal muscle Preparation: Permeabilized tissue
Coupling state: OXPHOS, ET