Animal Phylogeny and Human Locomotion Overview

Phylogenetic tree

Diagram showing evolutionary relationships among species.

Node

Point representing a common ancestor in phylogeny.

Phenetics

Focus on overall similarities among organisms.

Cladistics

Focus on shared novel traits among organisms.

Common ancestor

Most recent species from which others evolved.

Gait cycle

Repeating sequence of limb movements in locomotion.

Stride length

Distance between successive initial contacts of one foot.

Step length

Distance between heel prints of opposite feet.

Stance phase

Time when foot is on the ground during gait.

Swing phase

Time when foot is in the air during gait.

Duty cycle

Ratio of stance duration to stride duration.

Ground reaction force

Force exerted by the ground in response to weight.

Kinetics

Study of forces involved in movement.

Potential energy (PE)

Energy stored due to height or position.

Kinetic energy (KE)

Energy of motion, dependent on velocity.

Inverted pendulum model

Model explaining energy efficiency in walking.

Spring mass model

Model explaining energy efficiency in running.

Bipedalism

Locomotion on two legs, characteristic of humans.

Pelvis adaptation

Structural changes supporting efficient upright walking.

Symmetrical gait

Footfalls evenly spaced in time during locomotion.

Asymmetrical gait

Unequal timing between footfalls of limbs.

Double support phase

Period when both feet are on the ground.

Aerial phase

Moment when both feet are off the ground.

Stride frequency

Number of strides per unit time.

Cost of transport

Energy expenditure per unit distance traveled.

Humans vs. chimps locomotion

Humans are more energy-efficient than chimps.

Gluteus medius and minimus

Muscles stabilizing the pelvis during locomotion.

Femoral neck orientation

Angle of femur affecting center of mass stability.