Fig. 2
From: Neck Muscle EMG-Force Relationship and Its Reliability During Isometric Contractions
Schematic diagrams of the data sampling setup and torque calculation. a shows body positioning during neck extensions with a square block stabilizing the spine in a neutral posture, arms hanging slack beside the torso, and legs placed to prevent them from aiding during trials. A wall-attached force transducer, supported by a sling from the roof, is fixed to a strap that is level with the supraorbital ridge. Visual feedback is provided by a monitor on the wall. During neck flexions, subjects are reversed 180°, facing an additional monitor (not shown in figure). b shows the neck extension torque (τ) formula along with a visual description of its variables: the resistance force of the strap (F S), the force on the center of mass of the head and neck (filled square) due to gravitational acceleration (F G), and their respective lever arms (l S and l G) originating from the axis of rotation between the C7–T1 spinous process (filled circle)