Running Shoes

Abstract

A running shoe comprises an upper and a midsole attached to the upper, the midsole having a front portion corresponding to a forefoot and a rear portion corresponding to a heel. The front portion of the midsole may define a toe spring of at least 40 mm and a plurality of flex grooves, the plurality of flex grooves including one or more horizontal flex grooves and one or more longitudinal flex grooves, the horizontal flex groove(s) extending in a lateral to medial direction of the running shoe and allowing the front portion of the midsole to lie flat in response to application of less than 15 pounds of force against the toe spring, the longitudinal flex groove(s) extending in a front to back direction of the running shoe. The rear portion of the midsole may have a flat bottom that is narrower than the upper.

What is claimed is: 
     
         1 . A running shoe comprising:
 an upper; and   a midsole attached to the upper, the midsole having a front portion corresponding to a forefoot and a rear portion corresponding to a heel, the front portion of the midsole defining a toe spring of at least 40 mm and a plurality of flex grooves, the plurality of flex grooves including one or more horizontal flex grooves and one or more longitudinal flex grooves, the one or more horizontal flex grooves extending in a lateral to medial direction of the running shoe and allowing the front portion of the midsole to lie flat in response to application of less than 15 pounds of force against the toe spring, the one or more longitudinal flex grooves extending in a front to back direction of the running shoe, the rear portion of the midsole having a flat bottom that is narrower than the upper in the lateral to medial direction of the running shoe.   
     
     
         2 . The running shoe of  claim 1 , wherein the toe spring is at least 50 mm. 
     
     
         3 . The running shoe of  claim 1 , wherein the one or more horizontal flex grooves allow the front portion of the midsole to lie flat in response to application of less than 10 pounds of force against the toe spring. 
     
     
         4 . The running shoe of  claim 3 , wherein the one or more horizontal flex grooves allow the front portion of the midsole to lie flat in response to application of less than 5 pounds of force against the toe spring. 
     
     
         5 . The running shoe of  claim 1 , wherein the one or more horizontal flex grooves includes a first lower flex groove extending into the front portion of the midsole from a bottom thereof and a first upper flex groove extending into the front portion of the midsole from a top thereof, the first upper flex groove being vertically aligned with the first lower flex groove so as to reduce a thickness of the midsole therebetween. 
     
     
         6 . The running shoe of  claim 5 , wherein the first upper flex groove is vertically aligned with the first lower flex groove so as to reduce the thickness of the midsole therebetween to 20%-35% of a maximum thickness of the midsole. 
     
     
         7 . The running shoe of  claim 6 , wherein the first upper flex groove is vertically aligned with the first lower flex groove so as to reduce the thickness of the midsole therebetween to 25%-30% of a maximum thickness of the midsole. 
     
     
         8 . The running shoe of  claim 1 , wherein the one or more horizontal flex grooves includes a first flex groove and a second flex groove spaced from each other in the front to back direction of the running shoe. 
     
     
         9 . The running shoe of  claim 1 , wherein the one or more longitudinal flex grooves includes a first lower flex groove extending into the front portion of the midsole from a bottom thereof and a first upper flex groove extending into the front portion of the midsole from a top thereof, the first upper flex groove being vertically aligned with the first lower flex groove so as to reduce a thickness of the midsole therebetween. 
     
     
         10 . The running shoe of  claim 9 , wherein the first upper flex groove is vertically aligned with the first lower flex groove so as to reduce the thickness of the midsole therebetween to 20%-35% of a maximum thickness of the midsole. 
     
     
         11 . The running shoe of  claim 10 , wherein the first upper flex groove is vertically aligned with the first lower flex groove so as to reduce the thickness of the midsole therebetween to 25%-30% of a maximum thickness of the midsole. 
     
     
         12 . The running shoe of  claim 1 , wherein the one or more longitudinal flex grooves includes a first flex groove and a second flex groove spaced from each other in the lateral to medial direction of the running shoe. 
     
     
         13 . The running shoe of  claim 1 , wherein the upper comprises an elastic material. 
     
     
         14 . The running shoe of  claim 1 , wherein the rear portion of the midsole is rounded from the flat bottom thereof to the lateral and medial sides of the running shoe according to one or more radii of curvature of 15-25 mm. 
     
     
         15 . The running shoe of  claim 1 , wherein the flat bottom of the rear portion of the midsole is rounded about a perimeter thereof. 
     
     
         16 . The running shoe of  claim 1 , wherein the midsole exhibits zero drop from the rear portion to the front portion thereof. 
     
     
         17 . The running shoe of  claim 1 , wherein a maximum width of the front portion of the midsole in the lateral to medial direction of the running shoe is greater than 140% of a maximum width of the rear portion of the midsole in the lateral to medial direction of the running shoe. 
     
     
         18 . The running shoe of  claim 1 , further comprising an outsole attached to the midsole. 
     
     
         19 . A running shoe comprising:
 an upper; and   a sole unit attached to the upper, the sole unit having a front portion corresponding to a forefoot and a rear portion corresponding to a heel, the front portion of the sole unit defining a toe spring of at least 40 mm and a plurality of flex grooves, the plurality of flex grooves including one or more horizontal flex grooves and one or more longitudinal flex grooves, the one or more horizontal flex grooves extending in a lateral to medial direction of the running shoe and allowing the front portion of the sole unit to lie flat in response to application of 2-15 pounds of force against the toe spring, the one or more longitudinal flex grooves extending in a front to back direction of the running shoe, the rear portion of the sole unit having a flat bottom that is narrower than the upper in the lateral to medial direction of the running shoe.   
     
     
         20 . The running shoe of  claim 16 , wherein the sole unit comprises a midsole and an outsole.