Humans: Walking and Running Biology 201 Dr. Edwin DeMont Humans: Walking and Running St. Francis Xavier University

A variety of energy saving mechanisms have evolved. Terrestrial movement A variety of energy saving mechanisms have evolved. Legged (2 or 4) terrestrial locomotion is metabolically expensive. (Why?) Mechanisms are very different, depending on the gait of locomotion. Human walking and running gaits are very different, and thus save energy in different ways. St. Francis Xavier University

Demonstration of walking and running Human Movement Demonstration of walking and running My computer apps on ‘caesar’ (S:) Biomechanics Programs HBMA5.2 Press Run (Arrow under the Edit near top) Select Image Series Accept Settings Step > St. Francis Xavier University

Walking Vertical (and horizontal) changes in center of mass. Images from The Human Machine, McNeill Alexander. Filmed live Vertical (and horizontal) changes in center of mass. Contact leg is straight. Mechanical energy of the center of mass changes during cycle. St. Francis Xavier University

Center of mass rotates around straight leg. Walking Filmed live Center of mass rotates around straight leg. St. Francis Xavier University

Walking Center of mass and support leg look like an innervated pendulum. Mechanical energy changes in a pendulum similar to a human walking. St. Francis Xavier University

Pendulum Energy of motion is called kinetic energy units are joules where m is the mass of the object (kg) and V is the velocity of the object (m/s). St. Francis Xavier University

Pendulum Another type of energy we will examine is the energy of height (or position), and is called potential energy: P.E. = mgh units in Joules where m is the mass of the object (kg), g is the acceleration of gravity, and h is the ‘height’ (m) of the object. St. Francis Xavier University

Mechanical energy is conserved in a pendulum. Online Example St. Francis Xavier University

Walking Total K.E. P.E. Energy 2 3 Time St. Francis Xavier University

Mechanical energy of the center of mass changes during cycle. Running Filmed live Large vertical and horizontal oscillations Knees bent Aerial phase Mechanical energy of the center of mass changes during cycle. St. Francis Xavier University

Running ? Energy d b Time St. Francis Xavier University

Running External mechanical energy is transferred into internal ‘elastic’ energy. St. Francis Xavier University

Similar to hopping on a pogo stick. Running Similar to hopping on a pogo stick. St. Francis Xavier University

‘Springs’ are achilles tendon and ligaments in the bottom of the foot. Running ‘Springs’ are achilles tendon and ligaments in the bottom of the foot. St. Francis Xavier University

Running Energy transfer Energy d b Time St. Francis Xavier University