An article of footwear comprising: an upper; and a sole structure joined to the upper, the sole structure comprising a base, and an incline adjuster, and wherein the base is located in a forefoot portion of the sole structure, a midfoot portion of the sole structure, and a heel portion of the sole structure, the incline adjuster comprises an incline adjuster forefoot section located in the forefoot portion of the sole structure, the incline adjuster forefoot section comprising at least three chambers (35, 35a, 35b, 35c, 36, 36a, 36b, 36c), each of the chambers (35, 35a, 35b, 35c, 36, 36a, 36b, 36c) contains an electrorheological fluid and is configured to change outward extension in correspondence to change in volume of the electrorheological fluid within the chamber (35, 35a, 35b, 35c, 36, 36a, 36b, 36c), the chambers (35, 35a, 35b, 35c, 36, 36a, 36b, 36c) are connected by transfer channels (61, 62, 63, 64, 65), the transfer channels (61, 62, 63, 64, 65) comprise a flow-regulating transfer channel, the flow-regulating transfer channel comprising opposing first and second electrodes (107, 157) extending along a field-generating portion of the flow-regulating transfer channel; each of the chambers (35, 35a, 35b, 35c, 36, 36a, 36b, 36c) comprises a flexible wall (53, 53a, 53b, 53c, 54, 54a, 54b, 54c, 553a) forming a part of the chamber (35, 35a, 35b, 35c, 36, 36a, 36b, 36c) and that is configured to expand as the volume of the electrorheological fluid within the chamber (35, 35a, 35b, 35c, 36, 36a, 36b, 36c) increases and that is configured to contract as the volume of electrorheological fluid within the chamber (35, 35a, 35b, 35c, 36, 36a, 36b, 36c) decreases, the flexible wall (53, 53a, 53b, 53c, 54, 54a, 54b, 54c, 553a) of one of the chambers (35, 35a, 35b, 35c, 36, 36a, 36b, 36c) comprises a central section (71, 71a, 71b, 71c, 72, 72a, 72b, 72c) and a side section (73a, 73b, 73c, 74a, 74b, 74c) surrounding the central section (71, 71a, 71b, 71c, 72, 72a, 72b, 72c), and characterised in that the sole structure comprises a support plate located in at least the forefoot portion of the sole structure, the incline adjuster forefoot section is located between the base and the support plate in the forefoot portion of the sole structure, the chambers (35, 35a, 35b, 35c, 36, 36a, 36b, 36c) are connected in a series by the transfer channels (61, 62, 63, 64, 65), each of the transfer channels (61, 62, 63, 64, 65) permitting flow between two of the chambers (35, 35a, 35b, 35c, 36, 36a, 36b, 36c), the first and second electrodes extend along an interior of the field-generating portion of the flow-regulating transfer channel, and the side section (73a, 73b, 73c, 74a, 74b, 74c) comprises at least one fold defining a bellows shape of the chamber (35, 35a, 35b, 35c, 36, 36a, 36b, 36c). an upper; and a sole structure joined to the upper, the sole structure comprising a base, and an incline adjuster, and wherein the base is located in a forefoot portion of the sole structure, a midfoot portion of the sole structure, and a heel portion of the sole structure, the incline adjuster comprises an incline adjuster forefoot section located in the forefoot portion of the sole structure, the incline adjuster forefoot section comprising at least three chambers (35, 35a, 35b, 35c, 36, 36a, 36b, 36c), each of the chambers (35, 35a, 35b, 35c, 36, 36a, 36b, 36c) contains an electrorheological fluid and is configured to change outward extension in correspondence to change in volume of the electrorheological fluid within the chamber (35, 35a, 35b, 35c, 36, 36a, 36b, 36c), the chambers (35, 35a, 35b, 35c, 36, 36a, 36b, 36c) are connected by transfer channels (61, 62, 63, 64, 65), the transfer channels (61, 62, 63, 64, 65) comprise a flow-regulating transfer channel, the flow-regulating transfer channel comprising opposing first and second electrodes (107, 157) extending along a field-generating portion of the flow-regulating transfer channel; each of the chambers (35, 35a, 35b, 35c, 36, 36a, 36b, 36c) comprises a flexible wall (53, 53a, 53b, 53c, 54, 54a, 54b, 54c, 553a) forming a part of the chamber (35, 35a, 35b, 35c, 36, 36a, 36b, 36c) and that is configured to expand as the volume of the electrorheological fluid within the chamber (35, 35a, 35b, 35c, 36, 36a, 36b, 36c) increases and that is configured to contract as the volume of electrorheological fluid within the chamber (35, 35a, 35b, 35c, 36, 36a, 36b, 36c) decreases, the flexible wall (53, 53a, 53b, 53c, 54, 54a, 54b, 54c, 553a) of one of the chambers (35, 35a, 35b, 35c, 36, 36a, 36b, 36c) comprises a central section (71, 71a, 71b, 71c, 72, 72a, 72b, 72c) and a side section (73a, 73b, 73c, 74a, 74b, 74c) surrounding the central section (71, 71a, 71b, 71c, 72, 72a, 72b, 72c), and characterised in that the sole structure comprises a support plate located in at least the forefoot portion of the sole structure, the incline adjuster forefoot section is located between the base and the support plate in the forefoot portion of the sole structure, the chambers (35, 35a, 35b, 35c, 36, 36a, 36b, 36c) are connected in a series by the transfer channels (61, 62, 63, 64, 65), each of the transfer channels (61, 62, 63, 64, 65) permitting flow between two of the chambers (35, 35a, 35b, 35c, 36, 36a, 36b, 36c), the first and second electrodes extend along an interior of the field-generating portion of the flow-regulating transfer channel, and the side section (73a, 73b, 73c, 74a, 74b, 74c) comprises at least one fold defining a bellows shape of the chamber (35, 35a, 35b, 35c, 36, 36a, 36b, 36c).