If we are focused on the hamstrings muscle group and how they function at the knee (point of rotation) in a nordic hamstring curl, why does the movement seem to increase in difficulty as the individual's chest gets closer to the floor? 

The resistance moment arm is increasing in length

 The resistance moment arm is decreasing in length 

The resistance moment arm is greater in length than the force moment arm 

The resistance moment arm is short in length than the force moment arm.