Footwear with impact absorbing system

An article of footwear comprising:

• an upper portion, said upper portion forming a shell, said shell including a heel portion and a toe region;
• a sole, said sole having a curved lower surface extending generally from a heel area of said sole to at least a middle portion of said sole;
• an energy storage system, said energy storage system initially absorbing at least some of the impact forces generate by a user of the footwear at said heel portion and releasing the absorbed energy when the user's foot has pivoted about said curved lower surface.

An article of footwear comprising:

• an upper portion, said upper portion forming a shell, said shell including a heel portion and a toe region and having a longitudinal axis;
• a sole, said sole having a heel portion and a toe portion;
• an energy storage member, said energy storage member extending along said longitudinal axis between said shell and said sole, said energy storage member having a longitudinal extent and a variable spring constant across said longitudinal extent wherein said energy storage member generates a varying resistance along said longitudinal axis of said shell.

An article of footwear comprising:

• an upper portion, said upper portion forming a shell, said shell including a heel portion and a toe portion and having a longitudinal axis;
• a sole, said sole including a heel portion and a toe portion;
• a pair of spring portions, said spring portions transferring a reaction force from said sole to said upper portion, each of said spring portions including an upper spring portion connecting to said upper portion, a lower spring portion connecting to said sole, and a middle portion extending between said upper and lower spring portions, said middle portion being forward relative to said upper and lower spring portions wherein said upper spring portion deflects about said medial portion to define a first moment arm when said sole makes initial contact with a ground surface with said heel portion of said sole, said upper spring portion translating forward with respect to said lower spring portion when the user's body weight shifts forward, and said upper spring portion rolling about said middle portion as the user's body weight continues to shift forward and, thereafter, generating a propulsion force for the user of the footwear.