The purpose of this study was to compare the ventilatory threshold (VT) between treadmill walking against a horizontal impeding force (horizontal load walking) and a cycle ergometer exercise. Seven adult men volunteered to participate in this study. They performed horizontal load walking (velocity: 1.11 m/s) and a cycle ergometer exercise (pedaling frequency: 60 rpm), with loads imposed using a ramp slope technique. Oxygen uptake at the VT during horizontal load walking was greater than that during a cycle ergometer exercise (p < 0.05), whereas the opposite was noted for the work rate at VT (p < 0.05). The greater metabolic cost was because of the small output (work rate at VT) incurred during horizontal load walking. This suggested that the muscle mass recruited for exercise would be much greater for horizontal load walking than a cycle ergometer exercise because pedaling requires fewer muscles (lower extremities). In addition, a high reliability of VT during horizontal load walking was indicated from the correlation coefficient, standard error, and the confidence coefficient in two trials for the same subjects, which were 0.97, 0.097 L/min, and 0.96, respectively. These results suggest that horizontal load walking may be a modality for aerobic conditioning.