We examined the spatial organization of feed-forward postural adjustments produced prior to and during voluntary arm reaching movements executed while standing. We wished to investigate if the activity of postural muscles before and during reaching was directionally tuned and if a strategy of horizontal force constraint could be observed. To this end, 8 human subjects executed self-paced reach-to-point movements upon the random illumination of 1 of 13 light targets placed within a 180º array centered along the mid-line of the body. Analysis was divided into 2 periods: a first corresponding to the 250 ms preceding the onset of the reaching movements (termed pPA period), and a second 250 ms period immediately preceding target attainment (the aPA period). For both periods, EMG activity of the lower limb muscles revealed a clear directional tuning, with groups of muscles being activated for similar directions of reach. Analysis of horizontal ground reaction forces supported the existence of a force constraint strategy only for the pPA period, however, with those in the aPA period being more widely dispersed. We suggest that the strategy adopted for feed-forward pPAs is one where the tuned muscle synergies constrain the forces diagonally away from the centre of mass (CoM) to move it within the support base. However, the need to control for final finger and body position for each target during the aPA phase resulted in a distribution of vectors across reaching directions. Overall, our results would support the idea that end-point limb force during postural tasks depends upon the use of functional muscle synergies, which are used to displace the CoM or decelerate the body at the end of the reach.