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?
To discover the relationship between muscle-fiber types and performance, researchers obtained tiny biopsies of the gastrocnemius of 14 elite distance runners, 18 trained but non-elite distance runners, and 19 untrained subjects. They categorized the fiber types as slow or fast. (At the time of the study, intermediate fibers had not been identified as a third type.) Some of their data are shown here (* means). What conclusions can you draw from these data?

Verified step by step guidance

1. Examine the bar graph which shows the percentage of slow muscle fibers in three groups: elite runners, non-elite runners, and untrained subjects.
2. Notice that the elite runners have the highest percentage of slow fibers, followed by non-elite runners, and then untrained subjects.
3. Understand that slow muscle fibers, also known as Type I fibers, are more efficient at using oxygen to generate more fuel (ATP) for continuous, extended muscle contractions over a long time. They are crucial for endurance activities like long-distance running.
4. Observe the asterisks above the bars, which indicate statistically significant differences between the groups. This suggests that the differences in slow fiber percentages are not due to random chance.
5. Conclude that a higher percentage of slow muscle fibers is associated with better performance in distance running, as seen in elite runners compared to non-elite and untrained individuals.

Key Concepts

Muscle Fiber Types

Muscle fibers are categorized into two main types: slow-twitch (Type I) and fast-twitch (Type II). Slow-twitch fibers are more efficient for endurance activities, as they use oxygen to generate energy and are resistant to fatigue. In contrast, fast-twitch fibers are geared towards short bursts of power and speed but fatigue quickly. Understanding the distribution of these fibers in athletes can provide insights into their performance capabilities.

Gastrocnemius Muscle

The gastrocnemius is a major muscle in the calf that plays a crucial role in running and other athletic activities. It is composed of both slow and fast muscle fibers, contributing to both endurance and explosive power. Analyzing the fiber composition of the gastrocnemius in elite versus non-elite runners helps researchers understand how muscle structure influences performance in distance running.

Performance Correlation

The correlation between muscle fiber composition and athletic performance is a key area of study in exercise physiology. Research often shows that elite athletes, such as distance runners, tend to have a higher percentage of slow-twitch fibers, which enhances their endurance capabilities. By comparing the muscle fiber types of elite, non-elite, and untrained individuals, researchers can draw conclusions about how these differences contribute to overall running performance.