Exercise intensity alters breathing patterns

Steps:

• Identify the graph as likely showing respiratory cycles over time, with X and Y marking a shift in pattern frequency or depth.
• Recognize that running increases oxygen demand compared to walking, accelerating breathing rate.
• Match this to option B, as transitioning to running would shorten cycle intervals on the graph.
• Eliminate options that reduce or maintain respiratory effort, which wouldn't cause an intensified pattern change.

Why B is correct:

• Running elevates metabolic rate, increasing respiratory frequency per the ventilatory response to exercise (Fick's law of diffusion demands higher O2/CO2 exchange).

Why the others are wrong:

• A: Switching to walking decreases intensity, slowing breathing and flattening the pattern.
• C: Reduced intercostal contraction frequency would decrease overall respiratory rate, not accelerate it.
• D: Weaker contractions reduce tidal volume but don't typically alter cycle frequency patterns.

Final answer: B