Factors in Jumping
The focus here is on lowering mass over volume, increasing elasticity and tensile energy, and using effective proportional structures in creating leaping force and lowering stresses from impacts.
Larger animals will need adaptations that lower the weight of their bodies overall. Birds, even large birds, are known to have hollow bones to lower mass and assist with flight. Jumping may have similar considerations, but note that jumping introduces physical stresses that are not seen with flight.
Elasticity and Tension
The other side of the bone density consideration is that highly elastic muscles are important in jumping, so bone density must be high where the elastic tension and landing impacts are highest. The flea, one of the highest jumpers of the insect world has highly elastic muscle proteins. Frogs have really stretchy tendons to help with their jumps. The muscle structure must add tension either to itself, or to nearby tendons and then release the energy suddenly.
Proportion and Structure
The key factor here is keeping the upper part of the body small (perhaps tending towards rounded or oval for 4 legged creature) and keeping at least the back legs long. The examples of the frog and the flea are excellent for this. The counterpoint is that the front legs must be able to withstand impacts. The kangaroo is an example of a body type which creates a workaround to this, as the leaping and impacts both occur in the lower body.
Frog legs fold neatly out to either side of themselves, indicating that the upper part of the hind leg is a similar length to the lower leg. They also have very long toes, esp. the species that jump best. Front legs are smaller, and structured well for impact, thick, fleshy, and short.
Frog (South African Sharp Nosed):
- length of body (not including legs): 2.1 inch (53.34 mm)
- hind legs proportions: (.7 (upper leg) + .8 (lower leg) + .8(feet)) = 2.3 times the body length (about 5 inches)
- proportions source
- jump length: 130 inches
"The tibia bone of the hind leg (shin bone) is twice as long as the femur >(thigh bone) and creates a sort of "z" shape to the hind legs which act like >two giant springs, capable of propelling the kangaroo up to 30 feet in a >single bound. This unusual form of locomotion is called saltation."
Kangaroo (Eastern Grey):
- nose to rump: about 4 feet
- tail length: about 4 feet
- leg length: not yet available, still looking for source material
- jump length: about 35 feet
- jump height: up to 10 feet