The rod bent in jerks, the trout pumping against the current.

This prevents a fall in pressure, even though the heart must suddenly pump harder against gravity.

The heart works harder to pump against increased pressure, which weakens the muscle.

His heart had to pump against three times the normal "head" of liquid.

One's heart would adjust to the absence of any need to pump blood against gravity.

They were coming after him, and when he tried to run, his legs pumped uselessly against nothing.

His heart had to pump against three times the normal resistance of gravity.

He felt his breath pumping against the back of his throat.

As a result, it takes more power to pump against gravity than with it.

I locked my legs around his waist, and felt him pumping against me.