LATEST BUZZ FROM KC

Psoas 2

26th January 2014

Koen Schoolmeeters reflects further on psoas and considers actions of Psoas Major during submaximal isometric trunk efforts on painfree subjects.

 

Park R, Tsao H, Cresswell AG, Hodges P, 2012, Differential Activity of Regions of the Psoas Major and Quadratus Lumborum during Submaximal Isometric Trunk Efforts, J. Orthopaedic Research Febr:311-318

 

Park e.a (2012) concluded that Psoas Major’s anatomically different fascicles also differ in their functional roles during submaximal isometric trunk efforts. Anterior Psoas and Posterior Psoas are both active if trunk torque was generated towards lateral-flexion but their activation pattern were opposite in the sagittal plane: with greater activation of Posterior Psoas when torque is generated towards extension and with greater activation of Anterior Psoas when torque is generated towards flexion.

 

Co-contraction of both may further enhance the control of the lumbar spine in the sagittal plane by generating opposing torques.

 

They also concluded that Psoas activity did not change according to breathing phases.

 

In our opinion these findings should be interpreted and reproduced with some caution:

  • This study delivers evidence that Anterior Psoas and Posterior Psoas differ in their functional role.
  • Psoas Posterior resembles an extensor activity (as Multifidi and Erector Spinae) while Psoas Anterior resembles a flexor activity (as External Obliques).
  • But Posterior Psoas should not be considered as a prime mover towards extension because the Erector Spinae showed the greatest EMG-activity during extension torque.
  • Moreover, an increased EMG-activity of Psoas Posterior can also be interpreted as an isometric or even eccentric activity of Psoas Posterior to resist displacement and/or to control translation of the vertebra during the extension torque.
  • Anterior Psoas should not be considered as a prime mover towards flexion because the External – and Internal Obliques showed the greatest EMG-activity during the flexion torque. Moreover, an increased EMG-activity of Psoas Anterior can also also be explained by an isometric or even eccentric activity of Psoas anterior.
Keywords: Review 2014