1. A climbing exercise apparatus, comprising a first and second pedal means pivotally secured to a frame and adapted for providing a user with a vertically reciprocating climbing exercise movement for simulating hill climbing; resistance means for applying a variable level of resistance in opposition to said reciprocating climbing exercise movement, said resistance means being selectively adjustable in response to a load control signal for varying the level of resistance representing to at least a portion of hill; load control means for generating said load control signal to apply said resistance independently of the rate of said reciprocating climbing exercise movement, wherein said load control signal is effective to maintain said resistance at a constant value for a predetermined difficulty value; and display means for displaying an image representing said resistance of said at least a portion of a hill.