Assumption of a ‘gravity only region’ for gravity correction of passive joint moment data may be problematic

Passive muscle mechanical properties of the medial gastrocnemius in young adults with spastic cerebral palsy

“…The gravitational moment was modelled using a generalised sinusoid equation (Andersen et al, 2010) in the region where passive moments were lowest. Because a range of joint angles where there is zero passive force does not exist in the ankle joint (Clarke et al, 2010), the fit was constrained to bias the effect of weight. The gravitational fit was constrained using experimental measures of the relationship between joint position and torque with a 1 kg mass, similar to that of the foot (Clauser et al, 1969), located within the centre of the foot restraints.…”