Engineering enables: running blades


The development of running blades has greatly enhanced the running ability of amputees and people born without legs.  Learn more about how the inventor of running blades applied the scientific concept of potential elastic energy and biomimicry to design a high performance prosthetic leg.

When he was 21 years old, Van Phillips had his left leg amputated below the knee as the result of an accident.  He was given a prosthetic leg, but was frustrated that it didn’t work like his other leg. He called it a ‘dumb leg’ because it was heavy and it wouldn’t allow him to run and jump like he had done before his accident.

Van decided to design a prosthetic leg that would enable him to bounce, jump and run like he had been able to before his accident.

After years of designing, making, testing and breaking lots of prototypes, Van developed a prosthetic leg that enabled him to start running again.



Time to observe: working in pairs, students should observe how we move our bodies and use our muscles in a range of different activities from jumping as high as they can from standing and bouncing up and down on the spot.  They should use drawings to show the stages involved and observe how each differ.  Students will note the movement is a bit like how a spring works and will explore elastic potential energy.

Time to investigate: students will use a number of different types of balls to investigate elastic potential energy, discussing why the balls in their test might have different levels of elastic potential energy.

Stretch and challenge: Hooke's law states that the amount an elastic material changes when it is compressed (squashed) or extended (stretched) is directly proportional to the force applied to it.  Students will learn about the Hooke's law equation and apply it to calculate the potential energy of a given spring.

Time to calculate: using the data provided within the resource, students can discover the specific strength of a material by dividing the figure for its strength by the value given for its density.  Specific strength = strength / density.  They should add their answers to a copy of the table within the resource, draw charts to compare strengths and then discuss which material they think Van Phillips used to make his prosthetic leg and give reasons.

Supported by

  • Royal Academy of Engineering
  • Royal Air Force
  • BAE Systems