Oxygen uptake and efficiency related to external work rate during loaded walking.

The work load for the treadmill test is generally controlled by changing the slope of the treadmill (vertical method). Recently a new loading method was devised in which the subject pulls a weight horizontal from behind on the treadmill (horizontal method). The present study was conducted to compare the oxygen uptake (VO2 between the vertical and horizontal methods. The VO2 was 8 to 15% higher with the horizontal than with the vertical method on the same load levels. The difference was significant for 700 kpm/min (p less than 0.05). When unloaded, the frequency of steps was 109 +/- 9.3 steps/min. The frequency of steps was substantially unchanged with increasing external work rate in both methods. There was no difference in the frequency of steps between the two methods. The present paper discusses the significance of the VO2 difference resulting from the difference ways of loading, but the effect of frequency of steps was regarded as insignificant. The present study discussed the assumptions in calculating delta efficiency, delta efficiency per one step and net efficiency, and proposed the necessary conditions for the calculations. Although the efficiency from the three calculation ways was scattered, after selecting the efficiency under the necessary conditions, its value was almost the same and showed about 23%.