**5. Conclusions**

The findings of this study provided empirical evidence that patients with chronic low back pain had worse postural balance and enhanced depression than patients with acute low back pain. In contrast, patients with acute and chronic low back pain showed a similar enhancement in pain sensitivity. Finally, we found that depression, but not enhanced pain sensitivity, accounted for the deficits in postural balance. All these findings revealed the different relevance of postural balance, pain sensitivity and depression in the transition from acute to chronic pain conditions. Further investigation of the neurophysiological mechanisms involved in the association between these variables could help to better understand the chronification of pain and improve clinical assessment and intervention of chronic and acute low back pain.

**Author Contributions:** Conceptualization, J.A.M., P.M., J.G.V.M. and I.R.; Data curation, J.A.M. and J.G.V.M.; Formal analysis, P.M. and J.G.V.M.; Investigation, J.A.M. and I.R.; Methodology, J.A.M., J.G.V.M. and I.R.; Project administration, P.M. and I.R.; Software, J.G.V.M.; Supervision, P.M.; Writing original draft, J.A.M., P.M. and I.R.; Writing—review & editing, J.A.M. and I.R. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research was funded by grants from the Spanish State Secretariat for Research, Development and Innovation and European Regional Development Funds (#PSI2017-88388-C4-1-R) to P.M., grant PID2020-114967GA-I00 funded by MCIN/AEI/10.13039/501100011033 to I.R., and the support of the National Council of Technological and Scientific Development, CNPq, Brazil (Grant number: 307828/2018-2).

**Institutional Review Board Statement:** The study was conducted according to the guidelines of the Declaration of Helsinki, and approved by the Research and Ethics Committee of The Republic of the Gambia on 20 July 2016 with the code 01082016.

**Informed Consent Statement:** Informed consent was obtained from all subjects involved in the study.

**Data Availability Statement:** The data presented in this study are available on request from the corresponding author.

**Conflicts of Interest:** The authors declare no conflict of interest.
