Fig 1.
Metabolism in the cytosol and mitochondria of the skeletal muscle.
The metabolites are grouped in different pathways: the glycogen metabolism pathway, glycolysis, pentose phosphate pathway (PPP) and amino acid metabolism: BCAA: branched-chain amino acid; AAA: aromatic amino acid; PEP: phosphoenol pyruvic acid; MPC: mitochondrial pyruvate carrier; CPT: carnitine palmitoyl transferase; OXPHOS: oxidative phosphorylation. The TCA cycle is the final and universal step before the vast amount of ATP is created at the level of the electron transport system (OXPHOS). Apart from fat and glucose, also proteins can be catabolized to produce precursors of glycolysis and the TCA cycle. Amino acids can feed into the TCA cycle at acetyl CoA, as well as at steps further downstream from acetyl CoA (jagged arrows).
Fig 2.
Branched-chain amino acid metabolism (BCAA) in muscle mitochondria.
Intermediates derived from alternative pathways can feed into the TCA cycle. BCAT: branched-chain amino acid aminotransferase; BCKDH: branched-chain keto-acid dehydrogenase complex; CrAT: carnitine acetyltransferase.
Fig 3.
Ultrasonographic assessment of muscle morphometrics.
(A) in spindle shaped muscles; (B): in triangular shaped muscles.
Fig 4.
Muscle fiber typing with myosin heavy chain staining method.
(A) type I fibers in green; (B) type IIA fibers in blue; (C) type IIX fibers and sarcolemma in red; (D) merged image.
Fig 5.
Overview of changes in muscle diameter after 8 weeks of dry treadmill training and 8 weeks of aquatraining.
Green: significant decrease in muscle diameter (p<0.05); Red: significant increase in muscle diameter (p<0.05); Yellow: significant increase in muscle diameter right side > left side (p<0.05); Blue: significant increase in muscle diameter left side > right side (p<0.05). (A) Dry treadmill training; (B) Aquatraining.
Table 1.
Results of the muscle morphometric study.
Evolution of muscle diameter after dry treadmill training and aquatraining.
Fig 6.
Muscle fiber type composition of M. pectoralis, M. vastus lateralis and M. semitendinosus of untrained Friesian horses.
Results are percentages and are given as median (minimum-maximum).
Fig 7.
Cross sectional area of type I, IIA, IIAX and type IIX muscle fibers in different muscles.
Results are given as median (minimum-maximum) in μm2.
Fig 8.
Effect of dry treadmill training on muscle fiber type composition and cross sectional area (CSA).
Effect of 8 weeks of DT on muscle fiber type composition and CSA of the different muscle fibers was measured in the M. pectoralis, M. vastus lateralis and M. semitendinosus at rest in unconditioned state (untrained) and after 8 weeks of DT (trained) in Friesian horses.
Fig 9.
Effect of dry treadmill training on mean cross sectional area (CSA).
Effect of 8 weeks of DT on mean CSA was measured in the M. pectoralis, M. vastus lateralis and M. semitendinosus at rest in unconditioned state (untrained) and after 8 weeks of DT (trained) in seven Friesian horses.
Fig 10.
Principal component analysis (PCA) of metabolomic datasets.
PCA was performed on the M. pectoralis and the M. vastus lateralis of untrained and dry treadmill trained Friesian horses.
Table 2.
Metabolic heatmap of the M. pectoralis and M. vastus lateralis.
Table 3.
Overview of muscle morphometrics and muscle metabolism in horses.