Work Study and Ergonomics

Introduction

This chapter focuses upon the physiological aspects of muscular work, and it describes how various physiological systems work together to meet the energy expenditure requirements of work load and how these requirements can be measured quantitatively and considered in the analysis of physical work. Whereas in subsequent chapters the focus is on the mechanical aspects of physical work and awkward postures and heavy exertion forces that can lead to severe musculoskeletal problems, such as low-back pain and upper-extremity disorders.

This chapter begins with a depiction of the physiological structure of muscles and how energy is generated and made available for use by the muscles. Subsequently, it describes how the raw materials for energy production are supplied and its waste products removed by the circulatory and respiratory systems. The human body has a musculoskeletal system of bones, muscles and connective tissues which enable it to uphold the body posture, walk and run and lift and carry objects. Physical work is possible only when there is sufficient energy/vigour to support muscular contractions. Energy expenditure requirements of various types of activities are then described, together with a discussion about how the levels of energy expenditure can be measured quantitatively. Clearly, there are upper limits of energy production and muscular work for each individual. The implications of these work capacity limits for ergonomic job design are discussed in the last section of the chapter.

Muscle Structure

The primary role of muscle is to generate force and produce movement by exerting forces such as pull and push. The human body has mainly three types of muscle cells, also called as muscle fibres. However, this chapter is primarily focused upon the skeletal muscle, since it is directly responsible for physical work, these are described below.