Figure 1. Illustration of the experimental protocol.

(A) Experimental paradigm: subjects had to reach to a homogeneous (without salient point) surface placed at 130% of arm’s length, from the standing position. (B) Representation of the three initial arm starting postures: P1: hands at shoulder height, elbow bent, P2: forearm at 90° degrees with respect to trunk, and P3: arm hanging vertically along the body (natural posture)). Subjects adopted these initial postures in a random fashion before each trial for each equilibrium condition. (C) Representation of the two equilibrium conditions: Normal base of support condition (NBoS), subject’s feet normally placed on the floor at a comfortable stance width; Reduced base of support condition (RBoS), in which subjects stood on a horizontal 40 × 40 cm board under which a 5 cm large × 5 cm piece was fixed.