at age 35, jan runs a 5k race in july, finishing third. forty years later, she runs the same race but cannot…

at age 35, jan runs a 5k race in july, finishing third. forty years later, she runs the same race but cannot finish. which of the following is a possible hypothesis to explain this difference? years of running have increased her muscle fiber diameter. as a result, she cannot produce the needed atp to sustain this hypertrophic muscle contraction. the myoglobin does not bind oxygen as efficiently as it did when she was younger. this means her muscles go into anaerobic glycolysis too soon. jans skeletal muscles have become more elastic with age. this loss of rigidity results in her muscles collapsing. due to her age, jan cannot regulate her body temperature effectively, causing her to fatigue quickly and overheat.

at age 35, jan runs a 5k race in july, finishing third. forty years later, she runs the same race but cannot finish. which of the following is a possible hypothesis to explain this difference? years of running have increased her muscle fiber diameter. as a result, she cannot produce the needed atp to sustain this hypertrophic muscle contraction. the myoglobin does not bind oxygen as efficiently as it did when she was younger. this means her muscles go into anaerobic glycolysis too soon. jans skeletal muscles have become more elastic with age. this loss of rigidity results in her muscles collapsing. due to her age, jan cannot regulate her body temperature effectively, causing her to fatigue quickly and overheat.

Answer

Brief Explanations:

  • First option: Muscle fiber hypertrophy (increase in diameter) generally improves muscle strength and endurance, not the opposite. Also, well - trained muscles have better ATP - producing mechanisms (like increased mitochondrial density). So this option is incorrect.
  • Second option: Myoglobin is an oxygen - binding protein in muscle. As people age, the efficiency of various physiological processes, including oxygen - binding and utilization, can decline. If myoglobin doesn't bind oxygen as efficiently, the muscles will switch to anaerobic glycolysis (which produces less ATP per glucose molecule and leads to lactate accumulation) sooner. This can cause fatigue and inability to complete a strenuous activity like a 5K race.
  • Third option: Skeletal muscles tend to lose elasticity (become more rigid) with age due to factors like collagen cross - linking. So the statement about increased elasticity is incorrect.
  • Fourth option: While thermoregulation can be affected by age, it is not the most likely direct cause related to muscle function failure during a race. The primary issue in muscle - related performance decline during a race is more likely related to oxygen - utilization and energy - production mechanisms within the muscle (as in the myoglobin - related hypothesis).

Answer:

The myoglobin does not bind oxygen as efficiently as it did when she was younger. This means her muscles go into anaerobic glycolysis too soon.