What happens to the density of mitochondria during heavy resistance training?

What happens to the density of mitochondria during heavy resistance training?

• A. The density decreases
• B. The density increases
• C. The density remains unchanged
• D. The density fluctuates unpredictably

Answer: (A)

During heavy resistance training, you get substantial muscle fiber hypertrophy, meaning the cytoplasmic volume of the muscle cells expands a lot due to growth of contractile proteins. Mitochondria don’t increase in number at the same pace with this rapid expansion, so the amount of mitochondria per unit muscle volume—or mitochondrial density—drops. In other words, you can have more mitochondria overall or similar total content, but because the cell volume has grown so much, the density decreases. Endurance-type training tends to boost mitochondrial biogenesis and density, but the heavy resistance stimulus mainly expands the contractile machinery rather than mitochondria, leading to reduced density.

During heavy resistance training, you get substantial muscle fiber hypertrophy, meaning the cytoplasmic volume of the muscle cells expands a lot due to growth of contractile proteins. Mitochondria don’t increase in number at the same pace with this rapid expansion, so the amount of mitochondria per unit muscle volume—or mitochondrial density—drops. In other words, you can have more mitochondria overall or similar total content, but because the cell volume has grown so much, the density decreases. Endurance-type training tends to boost mitochondrial biogenesis and density, but the heavy resistance stimulus mainly expands the contractile machinery rather than mitochondria, leading to reduced density.