This theory consists of three parts: 1) A human can lift his body with force less than his weight, even though the force needed to lift an object must be slightly greater than the object's weight 2) A force f will accelerate a human body faster than accelerating any other object with the same mass. 3) The normal force by the ground on a person standing is less than the human weight. The force acting on the body in the above situations is the force of the human muscles on the same human. It is force of muscles on the muscles or the force of the muscles on the body as a whole muscle or the human lifting or moving his body by his own muscles' force, not any other external force exerted on him. 1) A human lifts his body with force less than his weight: Observations: A human of 60 kg can lift his body up like someone trying to pick a fruit from a tree with his feet and calves' muscles several times, but he will not be able to even move a rock of 60 kg with his all body muscles. A human of 60 kg can lift his body up holding a bar many times with his arm muscles, but he will not be able to even move a rock of 60 kg with his all body muscles. The human used force relatively very smaller than his maximum body muscles force and this is because the lifting is easy and can be done several times in both movements above, but the human cannot even move the rock by his maximum body muscles' force even though both the rock and his body are of the same mass 60 kg. The force must be bigger than the rock's weight 60 kgF to lift the rock if the human cannot lift the rock with his maximum muscles force then his maximum muscles' force is less than the weight of the rock 60 kgF. The human uses force far less than the maximum 60 kgF or far less than the human weight 60 kgF to lift his body. Experiment: A human stands on a scale. The scale reads his mass 60 kg. If the human lifts his body up like someone trying to pick a fruit from a tree, he exerts a force "f" on the scale. The scale will exert the same force "f" upwards on the human, this force "f" by the scale is the force that lifts the body. When the human lifts his body up like someone tries to pick a fruit from a tree with constant speed the scale will increase by f N in which the total measurement displayed on the scale will be 588+f N (the mass of the human displayed is 60 kg, the force of weight is 588 N, g=9.8 m/s/s) The scale will show the "f" force; which is the total read of the scale (588+f) minus the weight 588 or f N. This force f N which lifts the human is always less than 588 N or less than the human weight. In fact the force turns out to be relatively very small and this implies that the constant for any equation is a small fraction. Let's say for the the experiment the foot is 20 cm or 0.2 meters long , Now let's calculate for a 0.2 m lever. First the lever will be class 2 : The weight for 60 kg will be 60*9.8=588 Newtons. Class 2 is the fulcrum at the toes , and in this case both the weight of the human body and the force of his calves' muscles he lifts his body with will be at the ankle(also I can balance my body and make my body exactly vertical) F: force of the human weight f: force of muscles strength L: the distance of the weight from the ankle to the toes. l: distance of the muscles force from the ankle to the toes. f * l=FL. F=588 and L=l =0.2 f*0.2=588*0.2 f=588 Newton The force needed to lift the human body in the experiment does not change which is 588 N. The human must exert a 588 N force to lift his body but he actually lifts by weak calves' muscles and feet's muscles with the small force f N as in the experiment. 2) A force f will accelerate a human body faster than accelerating any other object with the same mass: Observations: An average human can jump with high acceleration against gravity by exerting force with only his legs' muscles, but he cannot throw a rock in the air with his all body muscles, this is if the average human with average muscles' strength could even move it with all body muscles. 3) The normal force by the ground on a person standing is less than the human weight: The human of 60 kg mass has 588 N weight (g=9.8 m/s/s). The force downwards of any human standing on the ground is his weight, that what the scale measures, however the normal force upwards is smaller than the weight, this makes the pressure on human soles when standing relatively small even if a massive human body of 60 kg is pressing on the soles. This is because the normal force by the ground on the soles is relatively small. Observations: The measurement here is human body damage: An average human body mass above the knees is approximately 55 kg. Even though the human body above the knees is massive, the human knees can bear it for years without knees' damage,this is as a result of small pressure on the knees and this pressure is small because the normal force on the knees is relatively small. Experiment: A human is lying by the belly on a concrete block. The concrete block does not touch any bones, just the belly, and the rest of the body is free in air. The human body weight 60 kg will not damage the belly. However, a rock of 60 kg put on the belly will damage it severely. Conclusion: When a human moves or lifts his own body, his mass is M=Cm : M is the value of mass the human suppose to move or lift. m is the true mass of the human body that the scale displays. C is a constant For example: A human does not actually lift his body 60 kg but he lifts a smaller value M, he needs force equals to the weight of this mass M. The force to lift the human will be smaller than the weight 60 kgF because the mass M is smaller than 60 kg. A human does not actually push a 60 kg of his body, but he pushes a smaller value M that has smaller inertia and gives greater acceleration that why jumping is fast and high compared to trying to throw a rock with the same mass so the Newtonian equation F=ma applies to this situation, for a human, F=Ma, M=Cm, C is a constant m is the human mass 60 kg A human knees does not actually bear a 60 kg mass but it bears a smaller mass M as above this makes human knees live longer. The theory applies to all organisms including animals.