What does cross-section or cross-sectional training mean?

Increasing the size of the muscles/ getting bigger.

Bodybuilders train to increase the size of their muscles(their muscles cross-section). Sprinter do to a lesser extent but the main goal for sprinters is to improve their strength without gaining added size.

The idea for cross-section training for sprinters is that bigger fibres are better shock absorbers.
But it has also been suggested that more dense muscles act better as shock absorbers.

You might find that the cross-section mass of some muscles respond better to 4-6 reps whilst other areas might respond better to higher reps.

Thank you guys.