In 2023, Tigist Assefa of Ethiopia set a new record with a time of 2 hours, 11 minutes, and 53 seconds. Scientists, trainers, and athletes alike have wondered about the extent to which muscle structure and function contribute to success in athletes such as Assefa. 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. Understand the muscle types: Recognize that the human body has different types of muscle fibers, primarily slow-twitch (Type I) and fast-twitch (Type II). Slow-twitch fibers are more efficient at using oxygen to generate more fuel (known as ATP) for continuous, extended muscle contractions over a long time. Fast-twitch fibers are better at generating short bursts of strength or speed.
2. Identify the muscle in question: The gastrocnemius muscle, part of the calf, is crucial for running as it helps in plantar flexing the foot at the ankle joint and flexing the leg at the knee joint. This muscle contains both types of fibers, but the proportion can vary.
3. Consider the effects of endurance training: Training for a marathon typically involves long, sustained periods of running, which primarily engages and develops slow-twitch muscle fibers. This type of training enhances the efficiency and endurance of these fibers.
4. Predict changes in muscle cells: While the total number of muscle cells (muscle fibers) generally remains constant, the size and efficiency of the existing muscle fibers can increase. Endurance training like marathon running can lead to physiological changes in the muscle fibers, such as increased mitochondrial density, increased capillary growth, and changes in enzyme activity, which improve aerobic capacity.
5. Summarize the effect on muscle cells: Training for a marathon would not necessarily increase the number of muscle cells in the gastrocnemius but would enhance the functionality and endurance capacity of the existing slow-twitch muscle fibers.

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 are fatigue-resistant and utilize oxygen effectively for energy. In contrast, fast-twitch fibers are geared towards short bursts of power and speed. Elite distance runners typically have a higher proportion of slow-twitch fibers, which enhances their endurance and performance in long-distance events.

Muscle Hypertrophy

Muscle hypertrophy refers to the increase in muscle size and strength resulting from resistance training or endurance training. In the context of marathon training, while hypertrophy is more commonly associated with strength training, endurance training can also lead to adaptations in muscle cells, including an increase in the number of mitochondria and capillaries, which improves oxygen delivery and energy production. This adaptation is crucial for enhancing performance in long-distance running.

Gastrocnemius Muscle Function

The gastrocnemius is a major muscle in the calf that plays a vital role in running and walking by facilitating plantar flexion of the foot. This muscle is particularly important for distance runners, as it helps propel the body forward with each stride. Training for a marathon can lead to adaptations in the gastrocnemius, including increased endurance and efficiency, which may involve changes in the number of muscle cells or their functional capacity to support prolonged activity.