Although heavy backpack carriage has been associated with back pain in schoolchildren, its causal relationship is still unknown. As people with low back pain exhibit an abnormal spinal control and backpack carriage has been shown to affect spinal repositioning ability in static upright stance, the goal of this study is to use dynamical systems theory to investigate the effects of backpack carriage on lumbopelvic control under dynamic situation. Lumbopelvic coordination was quantified in terms of Mean Absolute Relative Phase (MARP) and Deviation Phase (DP) whilst performing a reaching task under four loading conditions, i.e. no load, carrying 5%, 10% and 15% bodyweight (BW). It was shown that inter-segmental coordination was less in-phase (i.e. significant reduction in MARP with p < 0.001) and more variable (i.e. significant increase in DP with p − 0.005) during backpack carriage of 10% and 15% BW in forward reaching movement, suggesting greater alteration in lumbopelvic coordination at heavier weights. As abnormal movement strategies tend to increase the risk of spinal injury, pragmatic approaches should be considered to eradicate the adverse effect of heavy backpack carriage on spinal proprioception. Relevance to industry: Adverse effects of backpack carriage on lumbopelvic control were demonstrated. Greater alteration in trunk control at heavier weights was shown. Strategies should be devised to eradicate the effects of backpack carriage on proprioception. Copyright © 2014 Elsevier B.V. All rights reserved.