Barefoot running may have dramatic impacts on the posture of the spine.
Seventeen runners, who normally wore shoes during runs, were instructed to run barefoot. While they were running, posture analysis was conducted and muscle activation of various body parts were observed.
The researchers found that running barefoot caused runners to adopt a more extended posture in the lumbar area and also decreased activation of the paraspinals.
Conclusions
This is an interesting study that suggests for most people who are already overly extended, barefoot running will only make the situation worse. Some previous research has found that barefoot running promotes forefoot dominance, which may be the reason why extension was promoted. According to the Postural Restoration Institute, the heel is an essential reference center for maintaining positioning in the sagittal plane, and it may be that the lack of heel contact during barefoot running was the cause of the increase in extension.
Reference