Aerobic Activity

Metabolic rate typically increase with swimming speed in fish as a J-shaped curve, due to the drag that the fish has to overcome.

For running speed, metabolic rate increases linearly.

  • Slope is steeper for smaller animals due to allometry

For flying, the theoretical relationship between metabolic rate and flying speed is U-shaped due to aerodynamics.

Note that the energy cost per time unit and distance at each speed respectively are different

  • Latter is called cost of transport

Animals that have similar forms of locomotion (e.g. flying) have similar allometric relationships between the minimum weight-specific cost of transport and body weight

  • E.g. flies and pigeons obey the same allometry, despite not being closely related

  • Note that for swimming, fish have their own allometry when compared to other less streamlined underwater swimmers (e.g. turtles, seals, marine mammals).

Swimming has the lowest minimum cost of transport, followed by flying, walking, and running

Also, larger species cover a given distance with much lower weight-specific cost than smaller species.

The criterion value for maximum weight-specific cost of transportation (beyond which migrations are not considered sustainable), is 20 J/m/kg

VO2-max

  • Aerobic capacity

    • Maximal rate of oxygen consumption

    • Determines the peak rate at which an animal synthesises ATP by aerobic catabolism

      • Thus how intensely it can exercise

    • Declines with age

      • By 9% in sedentary people

      • By 5% in active people

    • Declines with altitude and atmospheric oxygen pressure