In this study, the AC RMS power across a load resistor attached
to the energy harvester was measured. Therefore, before beginning
the experiments on the treadmill, the approximate optimal
load resistance was found. To determine the optimal load resistance,
one participant walked at a normal pace of about 3–3.5 mph
(4.8–5.6 km/h) for 30 s with several different load resistances
attached. The test was repeated 3 times for each load resistance
value. The results are shown in Fig. 10. The solid line connects the
average value of the 3 different data points. The optimal resistance
was about 680