Distance runner Paula Radcliffe has won dozens of long-distance races and held the women's world record for the marathon since 2003. Scientists, trainers, and athletes alike have wondered about the extent to which muscle structure and function contribute to success in athletes such as Radcliffe.
What makes elite distance runners so good? Are their muscles somehow different from those of less successful athletes and non-athletes?
Predict the effect of training for a marathon on the number of muscle cells in the gastrocnemius. Explain.

Verified step by step guidance

1. Begin by understanding the basic structure of muscle tissue. Muscle tissue is composed of muscle fibers, which are long, cylindrical cells. These fibers are grouped together to form muscle bundles.
2. Consider the concept of muscle hypertrophy, which is the increase in muscle size due to exercise. Hypertrophy occurs primarily through the enlargement of existing muscle fibers rather than an increase in the number of muscle cells.
3. Training for a marathon involves endurance exercises that typically lead to adaptations in muscle fibers. These adaptations include an increase in the number of mitochondria, improved oxidative capacity, and changes in muscle fiber type composition, favoring slow-twitch fibers.
4. Understand that while the number of muscle cells (muscle fibers) generally does not increase, the existing fibers undergo changes that enhance their efficiency and endurance. This is due to the body's response to the demands of prolonged aerobic activity.
5. Conclude that marathon training does not increase the number of muscle cells in the gastrocnemius but rather enhances the function and efficiency of existing muscle fibers through physiological adaptations.

Key Concepts

Muscle Hypertrophy

Muscle hypertrophy refers to the increase in muscle size due to exercise, particularly resistance training. It involves the enlargement of existing muscle fibers rather than an increase in the number of muscle cells. This process is driven by the synthesis of new proteins and the repair of muscle tissue, enhancing the muscle's ability to generate force.

Muscle Fiber Types

Muscle fibers are categorized into different types based on their contraction speed and endurance capabilities: Type I (slow-twitch) and Type II (fast-twitch). Elite distance runners typically have a higher proportion of Type I fibers, which are more efficient at using oxygen to generate energy for prolonged activities, contributing to their endurance and success in long-distance events.

Adaptation to Endurance Training

Endurance training leads to physiological adaptations in muscles, including increased mitochondrial density, capillary networks, and oxidative enzyme activity. These changes enhance the muscle's ability to sustain aerobic metabolism, improving endurance performance. However, the number of muscle cells generally remains unchanged; instead, existing cells become more efficient at energy production.