Limits to maximal performance.

The research explores how body size affects the maximum speed and performance in mammals. The study indicates that different-sized animals produce differing results based on whether measurements are made on a relative or absolute scale. The paper also suggests that smaller animals have a higher cost of transport than larger ones.

Body Size and Locomotor Performance

• The research posits that body size plays a significant role in determining the maximum speed and performance of mammals. This is because numerous factors associated with the mechanics, energetics, and elastic energy storage during locomotion change with different body sizes.
• Comparing performances of different-sized animals may yield varying results depending on whether the measurement scales used are relative or absolute. Absolute speed seems to be a reliable method for animals whose survival depends on evading predators in real-time.

Metabolic Power and Body Size

• The comparison of metabolic power in animals of differing sizes needs to consider the mass-specific basis. Small mammals tend to have lower enzymatic capacities for anaerobic glycolysis and higher specific aerobic capacities compared to their larger counterparts.
• The research suggests that the energetic cost of locomotion is typically more expensive for smaller mammals than larger ones, explaining why smaller animals generally run slower than larger ones. This difference is attributed to the higher ratio of cost to available power in smaller mammals.

Maximal Aerobic Capacity and Body Size

• The maximum aerobic capacity is related to the body size of mammals. Limits to VO2max can be imposed by mitochondrial oxidative capacity, illustrated by goats, or by the oxygen transport system, shown in humans and horses.
• No single step in the oxygen transport system can limit the oxygen flow itself. However, in an average non-athletic mammal species, any step in the transport system might appear as the weakest link.
• In highly aerobic athletic species and potentially elite athletic individuals in other species, like humans, the flexible elements of the oxygen transport system might develop to such an extent that their oxygen transport capacities approach that of the least flexible element in the system, such as the lung.
• The study notes that maximum oxygen consumption is very high in these individuals and seems to be limited by the simultaneous failure of all components of the oxygen transport system.