Ergonomics is the study of the human body and its interaction with the environment in general, but more specifically, with the working environment. It is good practice, before designing a new product, to take into account the ergonomics of the user. Ergonomics can be broken down into the following sub-topics:

A body can be visualised as a machine.  Muscle and bone structure work in unison so that the machine functions efficiently.  The muscles oxidise nutrients to produce energy, this process metabolic by-products which are excreted as waste.  Physiology is the study of this energy conversion process.
This is a study of the forces at play in a body structure.  Damage can occur to muscle, joints and tissue if the principles of biometrics are not adhered to.  Damage can occur from a single movement, like lifting a heavy load, or can occur over a period of time from a repetition of the same movement.
This is the study of the dimensions, weight and strength of a body and such data is invaluable to a designer in the design of the best and most appropriate product for a particular body shape and size.
Although this subject deals with the allocation of work between people and machines, it can also be applied to the interaction of a body with a machine.  For example, how many buttons need to be pressed in order to get the desired reaction from a machine?
All of the above are important when designing a new product or re-designing an old product. The limitations of the human body must be taken into account in order that the design is user friendly. The proposed design for a shower head with an integral shower gel dispenser must take into account the bone and muscle structure of the human hand and its’ ability to grip and operate the shower head functions. The reach of the human arm must also be taken into account for the same reason.
                                                           SHOULDER AND ELBOW
The majority of injuries that occur to the arm are in the shoulder and elbow. Shoulder injuries are commonly tendon or ligament problems. Tendinitis: Inflammation of tendon. Rotator Cuff: Damage to the muscles that hold the joint in position. Damage can be permanent. The elbow injuries are similar to the shoulder. Injuries specific to the elbow are: Bursitis: Loose sack of skin on elbow tip that can get inflamed and swollen. Tennis Elbow:  Inflammation of the tendons that join the forearm muscles on the outside of the elbow.
                                                   WRIST AND HAND
The wrist and hand are at the working end of the arm and are subjected to a great deal of abuse. The fingers can be easily fractured and dislocated. Impact on the end of the finger causes tendon rupture, this leads to the inability to straighten the finger.The wrist can be easily damaged by misuse. Wrist Ligament Tear: Caused by impaction or twisting injury of wrist. This will impair movement and grip. Ulna Collateral Ligament Tear: Tear of the ligament that stabilizes the thumb when grasping.                                                                                                           


                                                        HIPS, UPPER LEGS AND KNEES
Hips are susceptible to strains which are stretched or torn muscle or tendon. Like elbows, they can suffer from Bursitis. The ligaments that connect the upper leg to the lower leg via the knee are susceptible to strains (stretching and/or tears). The knee is a very complex joint comprised of bone, cartilage, ligaments and fluid. Arthritis is the most common disease that affects the knee joint. This is caused by the wearing away of the cartilage causing swelling and pain.  Another common injury is to the anterior cruciate ligament (ACL). This is usually caused by a sudden twisting motion.
                                           LOWER LEG, ANKLE AND FOOT

The main lower leg/ankle injury is damage to the Achilles tendon which connects the calf muscle to the foot. Ankle injuries are usually sprains which is damage to the ligaments that interconnect the bones. Damage to tendons, which join the muscles to the bones, can cause pain throughout the length of the entire leg. The tendons connecting the toes to the anterior leg muscles are easily strained; this is also a common injury.  

Back pain caused by spinal injury is the most common of medical problems. Intervertebral Disk Degeneration: This condition is caused by the break down of the disks between the vertebrae and is a common condition which occurs with age. Sprains and tears to the ligaments that support the spine are caused by lifting or twisting incorrectly. Many conditions and diseases are associated with the spine: Scoliosis, Spondylolisthesis, Arthritis, Ankylosing Spondylitis, Spinal Stenosis. The spine is also prone to infections and tumours: Osteomyelitis, Diskitis, Cancer.
All images courtesy of:- 
(, 2010),,,,
US National Library of Medicine and the National Institute of Health (2010) [Online]. Available from:
The conditions outlined above are not a full list of problems that can occur in the human limbs and spine. Some conditions are brought on by injury, others are hereditary or simply wear and tear with the onset of old age. A full understanding of the limitations of the human muscular/skeletal structure is important during the design process of a new product. Any design fault could cause injury or make an existing condition more painful.