Energetics

Question 1

Wilson et al. 2003.

Answer 1

A catapult action for rapid limb protraction.
• Horses cannot achieve rapid limb protraction as there muscles are large and slow and cannot produce enough power.
• The horses rapid limb protraction is achieved by storing and releasing elastic strain energy in the biceps.

Question 2

Modica and Kram. 2005.

Answer 2

. Metabolic energy and muscular activity required for leg swing in running.
• Test comprised of using an ‘external swing assist’ to provide the force to swing the leg so that in theory the subject no longer used any energy to do so.
• Energy required for initiating and propagating leg swing accounts for approximately 20% of the metabolic cost of running.

Question 3

Marsh et al. 2004.

Answer 3

Partitioning the energetics of walking and running: swinging the legs is expensive.
• Injected micro-spheres into blood of guinea fowl so that a known density of micro-spheres was in the blood, these get trapped in capillaries of muscles and allow calculation of blood flow to said muscle during exercise.
• In guinea fowl the energy required to swing the legs is appreciable at approximately 26% and was independent of speed.

Question 4

Gottshall and Kram. 2005.

Answer 4

Energy cost and muscular activity required for leg swing during walking.
• By assisting both leg swing and centre of mass propulsion compared to just assisting centre of mass propulsion it was concluded that propagating and swinging the legs whilst walking accounts for 10-15% of total metabolic cost of walking.

Question 5

Doke et al. 2005.

Answer 5

Mechanics and energetics of swinging the human leg.
• Energy required for leg swing increases with approximately the fourth power of frequency during walking above the natural frequency of the leg.
• This experiment was limited by the fact they tried but struggled to limit the movement of the upper body during le swinging due to the reaction forces produced by swinging the leg.

Question 6

Rubenson and Marsh. 2009.

Answer 6

Mechanical efficiency of leg swing during walking and running in guinea fowl.
• Reverse dynamics model used.
• Efficiency of leg swing lower than expected muscle efficiency.
• Mechanical work is not a strong determinant of metabolic work.

Question 7

Umberger. 2010.

Answer 7

Stance and swing phase costs in human walking.
• A forwards dynamic modelling approach was used to estimate the instantaneous rates of energy consumption of individual muscles.
• Leg swing represents 29% of the total muscular cost of walking.