|
| |
|
|
|
|
||||
| Home Help Feedback Subscriptions Archive Search Table of Contents | ||||
|
Fig. 3. Mechanics of leg swinging as a function of frequency f, were
modeled well by a forced pendulum. (A) Subjects performed leg swinging at
decreasing amplitudes (filled symbols) with increasing frequency. Target swing
amplitudes were selected (Eqn 1)
to maintain a constant average rate of positive mechanical work. An additional
trial (open symbols) was performed at smaller amplitude for 0.67 Hz, to
provide an independent test of metabolic energy predictions. (B) Hip torque
amplitude T0 increased with f0.5
(R2=0.97), as predicted by the pendulum model
(Eqn 5). (C) The average rate of
positive mechanical work,
(+), remained nearly
constant for frequencies between 0.75 Hz and 1.08 Hz. A linear fit to these
data yielded a slope not significantly different from zero
(P>0.05). These data demonstrate that the experimental conditions
successfully produced leg swinging at a variety of frequencies but keeping
rate of mechanical work constant, facilitating the isolation of the cyclic
force cost. Data fits were performed using dimensionless variables (right-hand
axis) with body mass, gravitational constant, and leg length serving as base
units; conventional units are shown (left-hand axis) for convenience. Data
values shown are means ± s.d. (N=6).
|
