Week 5 Assignment
Changes that Occur in Skeletal Muscles as a Result of Endurance Training
Endurance training induces significant adaptations in skeletal muscle that make it less fatigable and a better organ for working at high intensities for long times. The most significant is a shift in muscle fiber composition. There are Type I (slow-twitch) and Type II (fast-twitch) fibers in skeletal muscles. Type I fibers resist fatigability and utilize oxidative metabolism almost exclusively, but Type II fibers have a function in generating rapid, powerful activity: Week 5 Assignment.
Endurance training brings about a transformation towards Type II (fast-oxidative) and an increased proportion of Type I fibers, and this strengthens the muscle’s sustained contraction capacity (Hall et al., 2021). Mitochondrial density in muscle fibers is augmented with training, and oxidative phosphorylation for generating ATP is augmented in efficiency and effectiveness. Greater mitochondrial content reduces the use of anaerobic processes producing lactic acid, a principal cause of fatigability.
Another adaptation is the increased density of capillaries in relation to muscle fibers. Endurance training induces angiogenesis, and increased delivery of oxygen to exercising muscles is facilitated. This permits increased aerobic production of energy and rapid disposal of metabolites, including hydrogen and carbon dioxide ions. Oxidative training raises oxidative enzymes, maximizing aerobic metabolism.
Oxidative enzymes promote carbohydrate and fat degradation, and fat use as a source of fuel, and glycogen conservation is increased (Muscella et al., 2020). Alteration in fuel use maximizes endurance through glycogen conservation and delayed exhaustion. Further, endurance training maximizes neuromuscular coordination, maximizing muscle contraction during long exercise.
How Endurance Training Improves Acid-Base Balance During Exercise
During high-intensity exercise, hydrogen ions (H+) in the body are generated through processes including ATP hydrolysis and lactic acid development. Consequently, acid accumulates, and its presence drops pH, producing metabolic acidosis, impairing function, and lessening performance. Strength training fortifies the acid-base regulating function in the body through an improvement in its capacities for buffering (Nam & Park, 2020).
Intracellular buffers, including bicarbonate, phosphate, and histidine-dipeptides, resist excessive hydrogen ions. With training, its level and effectiveness increase, and muscles can sustain contraction for a prolonged duration with less drop in pH. H+ is also removed from cells in trained muscles with increased effectiveness, lessening acidosis.
Extracellular buffering mechanisms maintain acid-base balance. The bicarbonate buffering mechanism takes in hydrogen ions and releases carbonic acid, which dissociates into water and CO2 and is eliminated through respiration in the lungs, taking with it excessive blood acid. Endurance training maximizes such a function through augmented capacity for ventilation and efficiency in the respiratory system and with it, an increased capacity for expulsion of CO2.
Endurance training subjects maintain a steady blood pH during high-intensity exercise, minimizing impairment in performance through acidosis of metabolites (Hopkins et al., 2022). All such adaptations work towards enhancing increased endurance through the maximized function of the metabolite-stressed muscles
Physiological Benefits May Happen for an Older Adult who Begins a Progressive Resistance-Training Program
A progressive resistive training regimen brings numerous positive aspects for older adults, particularly in regard to muscle maintenance. Sarcopenia, age-related loss of both strength and muscle mass, lessens falls and reduced mobility risk. Resistance training triggers anabolic processes in muscle, providing a micro-environment for increased strength and muscle fiber growth (Hurst et al., 2022).
Mobility is enhanced, and older adults can then preserve independence. Resistance training strengthens neuromuscular coordination and balance, minimizing fall and fall-related injury risk. With preserved coordination and strength, older adults can preserve a level of independence in activity performance.
Beyond muscle, resistance training aids in bone and metabolism. It strengthens bones, reducing osteoporosis-related fractures. Resistance exercise triggers bone-producing cells and, through them, strengthens bones and skeletal structures resistance training aids in insulin and blood sugar levels, reducing type 2 diabetes risk.
Cardiovascular improvements include reduced blood pressure, healthy arteries, and circulation (Nazir et al., 2024). Resistance training even aids in brain function, improving memory, executive function, and mood, and is a necessity for healthy aging.
References
Hall, E. C. R., Semenova, E. A., Bondareva, E. A., Borisov, O. V., Andryushchenko, O. N., Andryushchenko, L. B., Zmijewski, P., Generozov, E. V., & Ahmetov, I. I. (2021). Association of muscle fiber composition with health and exercise-related traits in athletes and untrained subjects. Biology of Sport, 38(4), 659–666. https://doi.org/10.5114/biolsport.2021.102923
Hopkins, E., Sharma, S., & Sanvictores, T. (2022, September 12). Physiology, Acid-Base Balance. National Library of Medicine; StatPearls Publishing. https://www.ncbi.nlm.nih.gov/books/NBK507807/
Hurst, C., Robinson, S. M., Witham, M. D., Dodds, R. M., Granic, A., Buckland, C., De Biase, S., Finnegan, S., Rochester, L., Skelton, D. A., & Sayer, A. A. (2022). Resistance exercise as a treatment for sarcopenia: prescription and delivery. Age and Ageing, 51(2). https://doi.org/10.1093/ageing/afac003
Muscella, A., Stefàno, E., Lunetti, P., Capobianco, L., & Marsigliante, S. (2020). The Regulation of Fat Metabolism during Aerobic Exercise. Biomolecules, 10(12), 1699. https://doi.org/10.3390/biom10121699
Nam, S.-S., & Park, H.-Y. (2020). Effects of endurance exercise under hypoxia on acid-base and ion balance in healthy males. Physical Activity and Nutrition, 24(3), 7–12. https://doi.org/10.20463/pan.2020.0015
Nazir, A., Henhen Heryaman, Cep Juli, Azizah Ugusman, Martha, J., Moeliono, M., & Atik, N. (2024). Resistance Training in Cardiovascular Diseases: A Review on Its Effectiveness in Controlling Risk Factors. Integrated Blood Pressure Control, Volume 17, 21–37. https://doi.org/10.2147/ibpc.s449086
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Question
Week 5 Assignment: Please use information from the book referenced below.
- Describe the changes that occur in skeletal muscle as a result of endurance training. Include a brief discussion on how endurance training improves acid-base balance during exercise. What physiological benefits may happen for an older adult who begins a progressive resistance-training program?
Reading:
- Powers, S. (2023). Exercise Physiology: T
heory and Application to Fitne ss and Performance (12th ed.). McGraw-Hill Higher Education (US). https://online.vitalsour ce.com/books/9781266201882 -
- Chapters: 11-14
- 11th ed
-
EAS Academy-An organization dedicated to education and community-outreach efforts in the areas of sports nutrition and sports medicine. The EAS Academy promotes cutting-edge scientific research to advance the knowledge base in nutrition and physical performance, and is a strong advocate for the discipline of sports nutrition and has strong ties with other professional organizations for promoting the relationships among nutrition, physical fitness, and good health.The following link includes a resource for athletes and trainers who participate in endurance training.

Week 5 Assignment
- “Endurance Exercise: Fatigue and Recovery”
- http://easacademy.org/trainer-
resources/article/endurance- exercise-fatigue-recovery Links to an external site.
- http://easacademy.org/trainer-
- UPMC Pinnacle – A nationally recognized leader in providing high-quality healthcare education and direct care services to 1.2 million residents in the central Pennsylvania region. The site’s interactive human map allows you to search for research-based information about a specific condition or recommendation for optimum health and fitness.
- https://www.pinnaclehealth.
org/wellness-library Links to an external site.
- https://www.pinnaclehealth.
- The following health resource article includes fundamental information on vital signs, including body temperature, pulse rate, respiration rate, and blood pressure.
- https://www.pinnaclehealth.
org/wellness-library/blog-and- staywell/health-resources/ article/36036 Links to an external site.
- https://www.pinnaclehealth.
- Acid-Base Balance – Khan Academy videos introducing the acid-base balance.
- “Definition of pH”
- https://www.khanacademy.org/
science/biology/water-acids- and-bases/modal/v/ introduction-to-definition-of- ph Links to an external site.
- https://www.khanacademy.org/
- “Buffer System”
- https://www.khanacademy.org/
science/biology/water-acids- and-bases/modal/v/buffer- system Links to an external site.
- https://www.khanacademy.org/
- “Definition of pH”
