A comparison of the effect of external loading upon power output in stair climbing and running up a ramp

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Abstract
Previous studies have shown that external loading increases the power output measured during stair climbing. However, it was noted in an earlier study that stairtreads form mechanical contraints which limit the extent to which a subject can be externally loaded, and, thereby, make it impossible to observe maximal power output for this type of activity. The purpose of this study was to compare the effects of external loading upon power output when running up stairs or a ramp. Since a ramp is free of the mechanical constraints of stairtreads, it was felt that higher power output values would be achieved using the ramp, and that it would be possible to observe an asymptote in power output which could not be obtained for stair climbing. Seven male subjects performed maximal ramp and stair climbing tests under five experimental loading conditions (no external load, 10.1, 19.2, 24.2, and 29.2 kg). For the ramp, it was possible to employ a sixth loading condition of 34.2 kg. For stair climbing, the mean (±SD) power output values under the five experimental conditions were 16.6±0.7, 17.3±1.3, 18.5±1.0, 18.6±1.5, and 18.9±1.7 W·kg−1, respectively. In contrast, the mean (± SD) power output values observed while running up the ramp were 18.8±1.4, 19.9±1.6, 20.5±1.6, 20.1±2.1, 20.3±2.1, and 19.8±1.9 W·kg−1, respectively. At each experimental condition, the differences between the ramp and stairs was significant (P<0.05). For the ramp, the highest mean power output occurred at a load of 19.2 kg. Beyond this load, power output progressively declined. In contrast, for the stairs, the highest power output occurred at a load of 29.2 kg. The results of this study demonstrate that the effect of loading upon power output measurements can be extended to running up a ramp. Furthermore, unlike stair climbing, it was possible using the ramp to observe a maximal power output value for each subject.