The Cost of Transport

Question 1

Dokes - 2004

HYPOTHESIS

Answer 1

To investigate how metabolic rate increases when increasing the frequency of leg swing

Question 2

Dokes - 2004

RESULTS

Answer 2

• Pendulum predicted work increases sharply with frequency, rate of work proportional to f^3
• Low economy of force productions explains why we don’t have short strides
• Metabolic rate depends on work done on legs and force/time and cannot distinguish
• Two views:
o Taylor 1980 - cost of running is to generate force to support body weight on ground
o Myers 1985 - moving legs faster does change metabolic energy
• Leg swings approximates a pendulum and therefore at NF the least energy is used (Mochon 1980)

Question 3

Dokes - 2004

METHOD

Answer 3

Used a mathematical pendulum model and 12 adults and compared results

Question 4

Modica - 2004

HYPOTHESIS

Answer 4

To find out what fraction of energetic cost of running at moderate speed is due to initiating the leg swing (and what muscles do this)

Question 5

Modica - 2004

RESULTS

Answer 5

• Metabolic rate reduced with a greater external swing assist force
• Approx 20% of metabolic rate is due to leg swing (with a force of 4% of bodyweight)

Question 6

Modica - 2004

Method

Answer 6

Made an external swing assist machine to accelerate the swing leg forward to help running

Question 7

Gottschall - 2005

HYPOTHESIS

Answer 7

To investigate the metabolic cost of initiating and propagating leg swing during walking

Question 8

Gottschall - 2005

RESULTS

Answer 8

• When applying a 10% of bodyweight force, metabolic cost of walking decreased to 58% of original
• Approx. 10% of net cost of walking is required to initiate and propagate leg swing

Question 9

Gottschall - 2005

METHOD

Answer 9

Applied an external force to people on a treadmillr

Question 10

March - 2005

HYPOTHESIS

Answer 10

Measure the split of muscles that are required during stance and swing phases of walking and running

Question 11

March - 2005

RESULTS

Answer 11

• Distribution of blood flow to muscles during swing and stance phases independent of running speed
  o Stance phase: 74% of blood flow
  o Swing phase: 26% of blood flow
• Therefore, swing phase during walking and running is appreciable, rejects Taylor where legs represent minor contribution to total metabolism

Question 12

March - 2005

RESULTS

Answer 12

Measured blood flow to muscles as this is controlled by mechanisms linked to metabolic rate

Question 13

Wilson - 2003

HYPOTHESIS

Answer 13

Show that larger animals contract their muscles using an elastic catapult, which is much more effective than normal non-elastic muscle

Question 14

Wilson - 2003

RESULTS

Answer 14

• Peak energy storage of 261J
• Biceps released 261J in 0.11s after foot off. Power is 4400W compared to muscle power of 90W
• Therefore, catapult mechanism is essential the movement of the horse