Malleability of skeletal muscle in overcoming limitations: structural elements

Area of Science:

• Muscle physiology
• Cellular biology
• Mitochondrial function

Background:

• Skeletal muscle's quantitative structure varies across species and functions.
• Exercise and electrical stimulation alter muscle ultrastructure.
• Mitochondrial volume density significantly increases with endurance exercise or chronic stimulation.

Purpose of the Study:

• To investigate the relationship between mitochondrial volume and oxygen consumption in skeletal muscle.
• To determine if mitochondrial metabolic capacity is constant across species.
• To establish a method for estimating aerobic power production based on mitochondrial content.

Main Methods:

• Analysis of quantitative structural composition of skeletal muscle tissue.
• Experimental manipulations including exercise training and chronic electrical stimulation.
• Measurement of mitochondrial volume density and maximal oxygen consumption rates.

Main Results:

• Mitochondrial volume density can increase over threefold with training or stimulation.
• Inner mitochondrial membrane surface density remains constant despite volume changes.
• A linear relationship exists between mitochondrial volume and maximal oxygen consumption.
• Maximal oxygen consumption per unit volume of mitochondria is consistent across species (approx. 5 ml O2 min-1 cm-3).

Conclusions:

• Mitochondrial metabolic capacity is conserved under limiting conditions in working skeletal muscle.
• Aerobic power production potential can be estimated from mitochondrial volume density.
• This finding has implications for understanding muscle adaptation and performance.