We investigate if amateur runners exhibit load asymmetries in their limbs and whether FFP2 masks may have an impact on them. We use 5 smart inertial measurements units (Xsens MTw Awinda) attached to the tibiae, the sacrum and the scapulae to monitor peak accelerations during each running cycle. We compare trails run under shoed and barefoot conditions as well with and without wearing FFP2 masks. Statistical analyses show some intriguing effects.