Tidal Volume: The amount of air which enters the lungs during normal inhalation at rest. The average tidal volume is 500ml. The same amount leaves the lungs during exhalation.

Inspiratory Reserve Volume: The amount of extra air inhaled (above tidal volume) during a deep breath. This can be as high as 3000ml.

Expiratory Reserve Volume: The amount of extra air exhaled (above tidal volume) during a forceful breath out.

Residual Volume: The amount of air left in the lungs following a maximal exhalation. There is always some air remaining to prevent the lungs from collapsing.

Vital Capacity: The most air you can exhale after taking the deepest breath you can. It can be up to ten times more than you would normally exhale.

Total Lung Capacity: This is the vital lung capacity plus the residual volume and is the total amount of air the lungs can hold. The average total lung capacity is 6000ml, although this varies with age, height, sex and health.

This continuum is concerned with the effects of the environment on skills (Knapp 1967)^[1]

Open skills: sports such as Netball, Football, and Hockey involve open skills. The environment is constantly changing and so movements have to be continually adapted. Skills are predominantly perceptual and externally paced, for example a pass in football.

Closed skills. These skills take place in a stable, predictable environment and the performer knows exactly what to do and when. Skills are not affected by the environment and movements follow set patterns and have a clear beginning and end. The skills tend to be self-paced, for example a free throw in Basketball, and serving in Squash or Tennis.

Knapp (1967)^[1] suggests that skills can fit on a continuum between open and closed.