In a fitness test a subject repeatedly stepped up using the right leg while the left leg was used to oppose the effect of gravity in the step down. Muscle pain was experienced several hours after the test. The soreness reached a peak in 1 to 2 days and persisted for about a week. The presences of proteins specific for muscle in the subject’s serum provided evidence for muscle cell injury. Structural damage was apparent in biopsy samples from the affected muscles
I know the answer to 1 is D and 2 is A but I can not seem to find information that makes enough sense for me to write an explanation.1. Which circumstances are most likely to impose excessively high forces and might
injure muscle cells? Explain your answer
A. isometric contraction when no shortening occurs
B. Overstretching of inactive muscle cells
C. Excessive shortening of contracting muscle cells
D. Stretching of contracting muscle cells by gravitational or other loads imposed during exercise
E. Rapid shortening at low loads
2. Why are metabolic limitations that lead to ATP depletion not responsible for delayed-
onset muscle soreness? Explain your answer.
A. ATP depletion would lead to rigor (attached, non-cycling crossbridges).
B. Any metabolic effect should have a rapid onset.
C. ATP consumption is highest in rapidly shortening muscles, where forces are
modest.
D. ATP production was not impaired in the test in which brief contractions did not
limit blood flow.
E. All of the above.
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