Increased oxygen extraction and mitochondrial protein expression after small muscle mass endurance training.
Scand J Med Sci Sports
; 30(9): 1615-1631, 2020 Sep.
Article
in En
| MEDLINE
| ID: mdl-32403173
ABSTRACT
When exercising with a small muscle mass, the mass-specific O2 delivery exceeds the muscle oxidative capacity resulting in a lower O2 extraction compared with whole-body exercise. We elevated the muscle oxidative capacity and tested its impact on O2 extraction during small muscle mass exercise. Nine individuals conducted six weeks of one-legged knee extension (1L-KE) endurance training. After training, the trained leg (TL) displayed 45% higher citrate synthase and COX-IV protein content in vastus lateralis and 15%-22% higher pulmonary oxygen uptake ( V Ë O 2 peak ) and peak power output ( W Ë peak ) during 1L-KE than the control leg (CON; all P < .05). Leg O2 extraction (catheters) and blood flow (ultrasound Doppler) were measured while both legs exercised simultaneously during 2L-KE at the same submaximal power outputs (real-time feedback-controlled). TL displayed higher O2 extraction than CON (main effect 1.7 ± 1.6% points; P = .010; 40%-83% of W Ë peak ) with the largest between-leg difference at 83% of W Ë peak (O2 extraction 3.2 ± 2.2% points; arteriovenous O2 difference 7.1 ± 4.8 mL· L-1 ; P < .001). At 83% of W Ë peak , muscle O2 conductance (DM O2 ; Fick law of diffusion) and the equilibration index Y were higher in TL (P < .01), indicating reduced diffusion limitations. The between-leg difference in O2 extraction correlated with the between-leg ratio of citrate synthase and COX-IV (r = .72-.73; P = .03), but not with the difference in the capillary-to-fiber ratio (P = .965). In conclusion, endurance training improves O2 extraction during small muscle mass exercise by elevating the muscle oxidative capacity and the recruitment of DM O2, especially evident during high-intensity exercise exploiting a larger fraction of the muscle oxidative capacity.
Key words
Full text:
1
Collection:
01-internacional
Database:
MEDLINE
Main subject:
Oxygen Consumption
/
Regional Blood Flow
/
Citrate (si)-Synthase
/
Mitochondrial Proteins
/
Quadriceps Muscle
/
Endurance Training
/
Mitochondria, Muscle
Limits:
Adult
/
Humans
Language:
En
Journal:
Scand J Med Sci Sports
Journal subject:
MEDICINA ESPORTIVA
Year:
2020
Type:
Article
Affiliation country:
Norway