This study aimed to compare plantar loading during uphill and flat jogging on both outdoor ground and treadmill surfaces. Twelve healthy male runners, equipped with in-shoe pressure measurement devices (Podoon insoles), completed uphill and level running sessions at 7 km/hr on both ground and treadmill surfaces. One-minute steady-state data were collected and analyzed. Results indicated no significant interaction effect of surface and slope on peak impact force and peak active forces (p > 0.05). However, uphill running led to significantly lower peak impact forces and higher peak active forces compared to level running (p < 0.05). In conclusion, uphill running, whether on ground or treadmill, can reduce peak impact forces and increase active forces. It is recommended that runners with prior lower limb injuries undergo uphill jogging training on a treadmill with controllable slope to mitigate impact loads.