Case study: Patient Scenario: A 45-year-old marathon runner, Maria, visits a clinic reporting muscle fatigue and decreased performance during races. Her history reveals she has increased her training intensity over the past six months. Her symptoms include prolonged muscle soreness after runs, occasional muscle cramps, and a noticeable drop in endurance. Tests reveal reduced force production in her soleus and extensor digitorum longus (EDL) muscles. A biopsy highlights a shift in muscle fiber composition, showing a reduction in Type I fibers and increased reliance on Type II fibers.