Chapter 2: Describing Motion in One Dimension, 1-D Linear Kinematics: Introduction

Motion is fundamental to the field of kinesiology, where we study the causes and consequences of human movement across many different domains. For instance, we may consider the effects of not enough motion (movement) on the heart and lungs, where we learn that low levels of physical activity is the most common modifiable risk factor for cardiovascular disease. While studying the psychology of physical activity we learn about the beneficial effects of movement on mental health, and also the challenges of behaviour change to increase physical activity. Similarly, anatomy teaches us which muscles produce movement at each joint and which nerves carry the messages from our brain to initiate movement. In courses on rehabilitation we gain insight into how the human body adapts to injury by changing how we walk or perform other activities of daily living.

So in order to study all these fascinating aspects of human movement we must first learn how to describe movement. In biomechanics this is referred to as kinematics, or the description of motion through properties such as position, time, velocity, and acceleration. While a full treatment of kinematics considers motion in two and three dimensions, for now we discuss motion in one dimension. This will provide us with the tools necessary to study more complex, multidimensional human movement. A good example of one-dimensional motion in biomechanics are short duration running races, such as the 100m, 200m and 400m. In these events, athletes must accelerate from a stationary position and generally travel along a (mostly) straight path in one direction. That is, we can describe their movement by considering only their forwards motion – movement side-to-side is generally negligible.