Muscular System Case Study 2


A 26 year old male came to his doctor complaining of sore muscles.  He had been taking an aerobics class for several weeks without any problems.  He recently noticed weakness in his legs when descending a flight of stairs.  The weakness lasted approximately 2 hours and pain began 48 hours later and persisted for about a week.


Lab tests showed an increase in blood serum levels of soluble proteins, such as creatine phosphate and myoglobin.  A biopsy of the patients’ left quadriceps showed a breakdown and disorganization of the myofilaments.  The doctor diagnosed the condition as DOMS, Delayed Onset of Muscle Soreness.


1.) Describe the structure of skeletal muscle at the sarcomere level. Explain the mechanism of muscle contraction.


2.)What role does ATP play in muscle fatigue?


3.) Is lack of ATP or low synthesis of ATP a reasonable explanation for fatigue in the quadriceps?


4.) What might be responsible for the slow development of weakness and soreness experienced by the patient?


5.) Exercise can raise the temperature of active muscles 5 o C or more.  Is heat injury a plausible explanation for DOMS?


 6.) Are there clinical signs of muscle cell injury?  What mechanism might have caused the injury of the muscle cells?


7.) Pain is usually a signal to protect the body from further injury.  How is muscle fatigue related to muscle “soreness”?  Is this a reasonable explanation for DOMS?