Increase of superoxide production at the muscle fiber level involves recruitment of supplemental units with no increase in per-unit production.
This does not, however, exclude that PTMs in other contractile proteins, such as thin filament proteins, play an important role for the impaired force generating capacity at the single muscle fiber level.
For instance, the analysis of X-ray or laser-light diffraction patterns gives accurate sarcomere length estimates on both the muscle fiber level (12, 7) and cell level (9, 11).
11 Recently, these findings have been extended to demonstrate that when low intensity (30% of 1RM) resistance exercise to failure is performed repeatedly, comparable increases in muscle hypertrophy (whole muscle and fiber level) are observed between low and high intensities.
In human subjects that undergo fatigue, muscle fiber ATP levels can be reduced by up to 20% (Sahlin et al., 1997; Karatzaferi et al., 2001a, 2001b; Jones et al., 2009), suggesting that the reduced ATP levels in Ryr1 AG/+ muscle might impair ATP-dependent enzyme activity during and after contraction (Homsher, 1987; Clausen et al., 1991; Smith et al., 2005; Barclay et al., 2007; Clausen, 2013b).
In control muscle, VDR was detected in muscle fibers but levels were very low, whereas in regenerating muscle, VDR expression was detected in the central nuclei of newly regenerating muscle fibers [ 29].
To evaluate an effect of niacin on fiber type distribution, muscle fiber typing and transcript level measurement of fiber-specific MHC isoforms was carried out.
In skeletal muscles, both at the single fiber level and at the whole muscle level, the passive force becomes significant only after the active force has peaked (i.e., at long lengths) [41], so that the total force exhibits a region of "negative stiffness".
We hypothesized that ongoing derangement of skeletal muscle cytoarchitecture at the single fiber level may precede and be responsible for the progressive muscle weakness.
HIIT's metabolic inefficiency has been contributed to rapid changes in skeletal muscle oxidative capacity due to the high level of muscle fiber recruitment, particularly in type II fibers [25].
Prior observations in which a 50 and 100% minced graft repair achieved similar levels of muscle fiber regeneration and strength recovery in a rat tibialis anterior muscle VML model supported the use of this level of repair in the current study.
