Prosthetic climbing legs

These are prosthetic climbing legs custom-engineered by designer Wayne Alexander of Dashfoot Ltd for double amputee athlete Mark Inglis to help fulfil Mark's goal of returning to mountain climbing.

Wayne Alexander
In the late 1990s, Alexander became interested in designing high performance prosthetics for amputees involved in sports and other physical challenges. He noted that 'it's much easier to reverse-engineer something that's been honed in that environment than to go the other way'.

Prosthetic legs
In recent years there have been huge advances in prosthetics - mostly in the use of materials such as carbon fibre. However, the fundamental problem in prosthetics is that they produce no power and can't receive sensory information. Energy-storing feet, where a spring captures power at the strike of the heel and propels the leg forward, were developed in the 1980s.

Design
These legs are prototypes made from steel and carbon fibre. Alexander originally built titanium legs but they were not reliable enough. Carbon fibre was used for the spar connecting the foot to the socket because it is light, immensely strong, and has energy-storing properties. However, as carbon fibre becomes brittle at low temperatures, a mixture of spring steel and titanium were used for the working components of the feet.

An eight-millimetre spring was used to capture energy on the heelstrike. The energy stored was released as the front of the foot left the ground and effectively 'kicked' the prosthesis forward, thereby saving Mark energy.

Significance
With the help of these legs, Mark Inglis successfully reached the summit of Aoraki / Mt Cook on 7 January 2002 in near perfect conditions. Wayne Alexander accompanied him on the climb (Inglis went on to climb Mount Everest in 2006 with even better legs made by Alexander).