Fig. 1From: Intra-session absolute and relative reliability of pressure pain thresholds in the low back region of vine-workers: effect of the number of trialsSchematic representation of the low back pressure pain threshold recording grid of the left (blank square) and right (black squares) erector spinae muscles. d1 represents the distance between the first (L1) and the fifth (L5) lumbar vertebrae. d2 equals one fourth of d1Back to article page