Following up on this because what I said about VO2 max is misleading. I’ve since learned that VO2 max is unusually useful as a measure of fitness specifically because it bypasses the problem of motivation. As effort and power output increase during the test, VO2 initially increases but then plateaus even as output continues to increase. So as long as motivation is sufficient to reach that plateau, VO2 max measures a physiological parameter rather than a combination of physiology and motivation.
Following up on this because what I said about VO2 max is misleading. I’ve since learned that VO2 max is unusually useful as a measure of fitness specifically because it bypasses the problem of motivation. As effort and power output increase during the test, VO2 initially increases but then plateaus even as output continues to increase. So as long as motivation is sufficient to reach that plateau, VO2 max measures a physiological parameter rather than a combination of physiology and motivation.