Chiropractic Research March 27, 2021

The Effects of Spinal Manipulation on Motor Unit Behavior

The Effects of Spinal Manipulation on Motor Unit Behavior

A ChiroSecure Research Update

Over recent years, a growing body of research has highlighted the neural plastic effects of spinal manipulation on the central nervous system. Recently, it has been shown that spinal manipulation improved outcomes, such as maximum voluntary force and limb joint position sense, reflecting improved sensorimotor integration and processing. This study aimed to further evaluate how spinal manipulation can alter neuromuscular activity.

High density electromyography (HD sEMG) signals from the tibialis anterior were recorded and decomposed in order to study motor unit changes in 14 subjects following spinal manipulation or a passive movement control session in a crossover study design.

Participants were asked to produce ankle dorsiflexion at two force levels, 5% and 10% of maximum voluntary contraction (MVC), following two different patterns of force production (“ramp” and “ramp and maintain”).

A significant decrease in the conduction velocity (p = 0.01) was observed during the “ramp and maintain” condition at 5% MVC after spinal manipulation. A decrease in conduction velocity suggests that spinal manipulation alters motor unit recruitment patterns with an increased recruitment of lower threshold, and lower twitch torque motor units.

This study shows that spinal manipulation provides at least short-term benefits in low intensity movement, via the improvement of the recruitment of low threshold motor unit and low twitch torque that are better suited for low force precise tasks.

Further research is required to investigate the longer term and potential functional effects of spinal manipulation and chiropractic care in a variety of patients who would benefit from improved muscle function.

Robinault, L.; Holobar, A.; Crémoux, S.; Rashid, U.; Niazi, I.K.; Holt, K.; Lauber, J.; Haavik, H. The Effects of Spinal Manipulation on Motor Unit Behavior. Brain Sci. 2021, 11, 105.