Energy return member for footwear

1. An article of footwear comprising:

a sole defining a lateral side and a medial side;

an upper attached to the sole, the upper and the sole defining a foot cavity; and

a resilient member positioned within the sole, the resilient member comprising a plurality of arms including a medial arm extending along the medial side of the sole and a lateral arm extending along the lateral side of the sole, wherein an end of the medial arm is connected to an end of the lateral arm, the resilient member further including at least one indentation in the medial arm or the lateral arm, the at least one indentation extending in a direction transverse to the length of the sole on a side of the resilient member that faces the foot cavity.

2. The article of footwear of claim 1 , the sole further comprising an insole and an outsole, wherein the resilient member is embedded in the sole between the insole and the outsole.

3. The article of footwear of claim 1 , the sole further defining a forefoot region, a midfoot region, and a heel region, the medial arm extending along the medial side of the sole from the midfoot region to the forefoot region of the sole, and the lateral arm extending along the lateral side of the sole from the midfoot region to the forefoot region of the sole.

4. The article of footwear of claim 3 wherein the end of the medial arm is connected to the end of the lateral arm in the midfoot region of the sole.

5. The article of footwear of claim 4 , the resilient member further comprising a central portion at least partially positioned in the heel region of the sole and connecting the medial arm and the lateral arm, the medial arm and lateral arm extending outward from the central portion.

6. The article of footwear of claim 5 further comprising at least one posterior arm extending outward from the central portion into the heel region of the sole.

7. The article of footwear of claim 6 wherein the resilient member is an H-shaped spring plate, and wherein the at least one posterior arm includes a first posterior arm on the medial side of the sole and a second posterior arm on the lateral side of the sole.

8. The article of footwear of claim 1 wherein the resilient member is a Y-shaped spring plate.

9. The article of footwear of claim 1 , the sole further comprising an insole and an outsole, wherein the resilient member is embedded between the insole and the outsole.

10. The article of footwear of claim 1 wherein the resilient member is comprised of carbon.

11. An article of footwear comprising:

an upper;

a sole attached to the upper, the sole including a forefoot region, a midfoot region, and a heel region, wherein the upper and the sole form a foot cavity; and

a resilient member embedded in the sole, the resilient member including a first cantilever arm, a second cantilever arm, a third cantilever arm, a fourth cantilever arm and a central portion, the central portion at least partially positioned in the midfoot region of the sole, the first cantilever arm and the second cantilever arm extending from the central portion into the forefoot region of the sole, the third cantilever arm and the fourth cantilever arm extending from the central portion into the heel region of the sole, the first and third cantilever arms extending along a lateral side of the sole and the second and fourth cantilever arms extending along a medial side of the sole, the resilient member further including at least one indentation extending in a direction transverse to the length of the sole on a side of the resilient member that faces the foot cavity, the at least one indentation configured to promote deformation of the resilient member in response to the force on the sole.

12. The article of footwear of claim 11 wherein the at least one indentation is provided on one of the first, second, third or fourth cantilever arms.

13. The article of footwear of claim 12 wherein the at least one indentation includes a plurality of indentations on the first and second cantilever arms.

14. An article of footwear configured for a foot of a human wearer, the article of footwear comprising:

a sole including a medial side, a lateral side, a forefoot region and a heel region;

an upper attached to the sole, the upper and sole defining a foot cavity configured to receive the foot; and

a spring plate positioned within the sole, the spring plate comprising:

a central member positioned posterior to the forefoot region of the sole;

a first medial arm extending from the central member to the forefoot region of the sole on a medial side of the sole;

a first lateral arm extending from the central member to the forefoot region of the sole on a lateral side of the sole;

at least one posterior arm extending from the central member to the heel region of the sole; and

at least one indentation in the first medial arm or the first lateral arm, the at least one indentation extending in a direction transverse to the length of the sole on a side of the spring plate that faces the foot cavity;

wherein the first medial arm and the first lateral arm are configured to resiliently deform in response to a force on the sole during a stride of the wearer and resiliently recover in response to the force being removed from the sole, the at least one indentation configured to promote deformation of the spring plate in response to the force on the sole.

15. The article of footwear of claim 14 , the at least one posterior arm in the spring plate further comprising:

a second medial arm extending from the central member to the heel region on the medial side of the sole; and

a second lateral arm extending from the central member to the heel region on the lateral side of the sole.

16. The article of footwear of claim 14 , the central member extending into the heel region.

17. The article of footwear of claim 14 , wherein the spring plate is a carbon fiber reinforced polymer member.

18. The article of footwear of claim 14 , the first medial arm being configured to deform to a greater degree than the first lateral arm during a pronated stride of the human wearer.

19. The article of footwear of claim 14 , the first medial arm further comprising an inwardly extending bulge positioned proximate to the central member on the first medial arm.