HUMAN POWER CAPABILITY ver 1: 9199
A curve that can be very handy in understanding Human Power Capability is a plot of power vs. Endurance (time).
Many researchers have measured the ability of athletes to produce power. The experiments are designed to require a subject to performs at a specific amount of power until exhausted; no additional power is available without rest and recovery. HPcap.jpg reflects ergometric data contributed by Harrison, Kyle, Wylkie, and NASA researchers . Scatter among measurements is large, due to variability of age, general health, motivation, subject acclimation to the ergometer device, etc. The curves represent smoothed averages. While none of the curves represent on-road bicycling, they nevertheless establish an objective measure of human capability in similar activities. The key feature of all the curves is a sharply declining endurance slope dropping quickly with a marginal increase in power demand.
The FIRST CLASS ATHLETES curve represents younger people in constant training for competitive events. These remarkable subjects can produce 0.4 HP for up to 8 hours. The HEALTHY HUMANS curve includes college and military personnel, as well as people in moderate training. They can produce 0.1 HP for 8 hours.
However there is a group of people who are not represented on these curves. They are what I call “Average Humans.”
Average Humans are physically active but do not participate in regular training. Their ability to produce the "natural" level of .1HP comes from such daily activities as walking, lifting, climbing stairs, and modest exercise. The area between upper and lower limits (cross-hatched) is large because it represents a broad range of individuals, ranging from women to older people.
This addition to the human power curve
has been reviewed and agreed on by C. Kyle.
The characteristic steepness of the measured power curves has been retained for the Average Humans. For this group a change in power demand as small as 0.01 HP is noticeable and significant. For example, the time to fatigue at 0.10 HP is 6.0 hours, whereas the endurance limit at 0.11 HP is only 4.7 hours, a drop in duration of 22% for a demand increase of 10%. At higher power levels, near the limit of long-term effort for Average Humans (about 0.14 HP), any increase in demand will be difficult to manage. From the quasi- steady baseline of 0.10 HP, it takes the addition of only three or four marginal demand increments at .01 HP each to reach the long-term limit.
Note; although the curve shows a value of around two hours at 0.14 HP this is to a state of exhaustion.
An exciting prospect in conjunction with the spreadsheets ability to quantify power, is nearly any bicycle enjoys the potential of functioning as an ergonometer. This gives anyone the ability to plot their own capability curve.
 Ref 1; Second International Human Powered Vehicle Scientific Symposium 1984, pg50.
Bicycling Science pg 51; Frank Rowland Whitt, David Gordon Wilson, 1981.