A scientist claims that endurance training is an exercise method that can improve physical performance by inducing changes in type 1 skeletal muscle fibers that allow the fiber to perform aerobic respiration more efficiently to generate ATP. Given this, which of the following adaptations is most likely to occur in type 1 fibers in response to endurance training?Mitochondrial density of the muscle fibers increasesCapillary supply around the muscle fiber increasesMyoglobin concentration per muscle fiber increases

Question

A scientist claims that endurance training is an exercise method that can improve physical performance by inducing changes in type 1 skeletal muscle fibers that allow the fiber to perform aerobic respiration more efficiently to generate ATP.  Given this, which of the following adaptations is most likely to occur in type 1 fibers in response to endurance training?Mitochondrial density of the muscle fibers increasesCapillary supply around the muscle fiber increasesMyoglobin concentration per muscle fiber increases

Quizplus · Accepted Answer

11ecba2d_0fe5_8fcb_a3bf_5de6b4a1ed0e_MD0008_00 Skeletal muscle fibers (cells) can be identified as type 1 (slow oxidative), 2A (fast oxidative-glycolytic), or 2X (fast glycolytic); this classification is based on two features of muscle fibers: Their contractile speed (fast or slow): Contractile speed is determined largely by the catalytic speed of the myosin ATPase and the activity of the associated motor neuron at the neuromuscular junction. Their primary means of producing ATP (oxidative or glycolytic): To generate ATP, oxidative fibers use aerobic respiration, but glycolytic fibers use anaerobic glycolysis. Type 1 fibers are fatigue-resistant, contract slowly, and use aerobic respiration as their primary method of ATP production. Consequently, compared with glycolytic fibers, type 1 fibers are much richer in mitochondria, the site where many enzymes involved in aerobic respiration reside. Type 1 fibers also have access to a continuous supply of oxygen (the final electron acceptor of aerobic respiration) through an extensive network of capillaries that surround the muscle. In addition, type 1 fibers appear red under the microscope due to high concentrations of myoglobin, a red-pigmented, oxygen-binding molecule that delivers oxygen to the muscle cell interior, where the mitochondria are housed. To perform aerobic respiration more efficiently, endurance-trained type 1 fibers would likely exhibit increased mitochondrial density to improve metabolic capacity (Number I), increased capillary supply to enhance oxygen delivery to the fiber (Number II), and increased myoglobin content to ferry oxygen within the fiber more efficiently (Number III). Educational objective: Skeletal muscle fibers can be classified as type 1 (slow oxidative), 2A (fast oxidative-glycolytic), or 2X (fast glycolytic). The speed of contraction (slow or fast) is determined by the catalytic speed of the myosin ATPase and the activity of the fiber's associated motor neuron. Oxidative fibers are fatigue resistant and synthesize ATP through aerobic respiration (oxygen-requiring pathways). Glycolytic fibers are easily fatigable and generate ATP through anaerobic glycolysis (in the absence of oxygen).

A Scientist Claims That Endurance Training Is an Exercise Method