Running

• Energy During Running:

  • Gravitational potential & kinetic energy not trading off anymore
  • CoM moving slowest in running, but highest?
  • Absorb the force = slowest CoM
  • Fastest CoM in the air
  • Walking → running; doesn’t gradually change, changes over at a certain point
• Running Model:

  • velocity (v) highest during flight phase, lowest at mid stance
  • CoM lowest at mid stance
  • Energy absorbed during early stance & released in late stance
• Running Model:

  • Better model for running = mass spring model
  • The arch CoM follows
  • Absorb & release energy
  • 2 very different models = different models of locomotion
• Heel Strike Running GRF:

  • Double peak in Fz in heel strike running
  • Impact transient & push off
  • Fy shows braking & propulsion
• Heel Strike Running GRF:

  • Vertical component of force & forward, backward component
  • Pos y = direction walking
  • Pos z = vertical ground reaction force
  • Pos x = to the right
  • Quick build up in the force (steep slope = loading rate [can lead to injury = aggressive on tissues])
  • Initial take off = initial spike, go thru mid stance (similar to butterfly diagram) & final peak as pushing off
• Heel Strike Running GRF:

  • Same pattern for opposite leg
  • y = neg force at beginning (braking force, forward & backwards), second half of stance = pos force)
  • Shallow curve by bigger strides → as foot out further resultant tipped out more, vertical force a little less, neg y is gonna be a little bit more
  • Change technique → land softly, landing on toes shown on next slide
• Forefoot Strike Running GRF:

  • Associated with barefoot/minimal shoe running
  • Single peak; transient rounded off by more gradual deceleration
  • Load taken up by Achilles rather than heel & compressive forces
• Forefoot Strike Running GRF:

  • Only barefoot with forefoot running
  • Land on more lateral metatarsals
  • Absorb some of the force
• Forefoot Strike Running GRF:

  • Ankle torques takes up more load than on heel (goes straight thru tibia)
  • Loading rate is what is affective
  • Not much change of pattern of y
  • Load has to go somewhere still
  • Switch to this technique, is now taken up with structures of foot & achilles