[4] Preferred walking speed has important clinical applications as an indicator of mobility and independence.
Improving (increasing) people's preferred walking speed is a significant clinical goal in these populations.
[citation needed] People have suggested mechanical, energetic, physiological and psychological factors as contributors to speed selection.
For example, they may trade off time to destination, which is minimized at fast walking speeds, and metabolic rate, muscle force or joint stress.
Conversely, aging, joint pain, instability, incline, metabolic rate and visual decline cause people to walk more slowly.
Economic theory therefore predicts that value-of-time is a key factor influencing preferred walking speed.
Supporting this idea, Darley and Bateson show that individuals who are hurried under experimental conditions are less likely to stop in response to a distraction, and so they arrive at their destination sooner.
Ralston (1958) showed that humans tend to walk at or near the speed that minimizes gross cost of transport.
He showed that gross cost of transport is minimized at about 1.23 m/s (4.4 km/h; 2.8 mph), which corresponded to the preferred speed of his subjects.
Biomechanical factors such as mechanical work, stability, and joint or muscle forces may also influence human walking speed.
[11] Similarly, swinging the legs relative to the center of mass requires some internal mechanical work.
Norris showed that elderly individuals walked faster when their ankle extensors were augmented by an external pneumatic muscle.
There, the environment flows past an individual more quickly than their walking speed would predict (higher than normal visual gain).
[16] The timing and direction of these responses strongly indicate that a rapid predictive process informed by visual feedback helps select preferred speed, perhaps to complement a slower optimization process that directly senses metabolic rate and iteratively adapts gait to minimize it.
With the wide availability of inexpensive pedometers, medical professionals recommend walking as an exercise for cardiac health and/or weight loss.
Maximum heart rate for exercise (220 minus age), when compared to charts of "fat burning goals" support many of the references that give the average of 1.4 m/s (3.1 mph), as within this target range.