162 Pak J Med Sci 2011 Vol. 27 No. 1 www.pjms.com.pk Original Article The Inhibition of short latency reflex linking the pretibial muscles to quadriceps motoneurones during stance to swing transition in humans Khosro K Kalantari 1 , Ronald H Baxendale 2 , Asghar Rezasoltani 3 ABSTRACT Objective: The modulation of short latency reflex linking the pretibial to quadriceps muscle (CPQ reflex) was investigated in seven subjects during walking on a treadmill at the stance to swing transition period. Methodology: The intensity of quadriceps (Q) EMG was increased throughout the gait cycle by using a modified knee orthosis. Pairs of spring were added to the orthosis to produce different levels of muscular activity in Q during the midstance, transition period and terminal swing phase of gait. Electrical stimulation was applied to the common peroneal nerve (CPN) at these three instants of gait. Results: The peak to peak amplitude of CPQ reflex was significantly increased with escalation of background EMG in Q during midstance (p<0.015) and terminal swing (p<0.04). At the transition period however, despite significant increase in the Q activity no responses was evoked. Conclusions: The results were indicative of an active inhibition of the reflex pathway during transition period. This inhibition could help the unloading of the limb that is necessary for the initiation of the swing phase. KEY WORDS: Quadriceps, Reflex, Gait, Inhibition, Swing Phase. Pak J Med Sci January - March 2011 Vol. 27 No. 1 162-166 How to cite this article: Kalantari KK, Baxendale RH, Rezasoltani A. The Inhibition of short latency reflex linking the pretibial muscles to quadriceps motoneurones during stance to swing transition in humans. Pak J Med Sci 2011;27(1):162-166 1. Khosro K Kalantari, PhD PT, Associate Professor. 2. Ronald H Baxendale, PhD, Reader, FBLS, Integrative and Systems Biology Research Theme, West Medical Building, University of Glasgow G12 8QQ. 3. Asghar Rezasoltani, PhD, Associate Professor. 1, 3: Department of Physiotherapy, Shahid Beheshti University of Medical Sciences, Tehran-16169, Iran. Correspondence: Khosro K Kalantari, PhD PT E-mail: khosro_khademi@yahoo.co.uk * Received for Publication: December 9, 2009 * Accepted: October 25, 2010 INTRODUCTION The spinal cord in humans 1,2 contains circuitry capable of generating alternating activity for stereo- typical limb movements such as walking. While the motor output associated with human walking is thought to be largely generated by spinal centers, both supraspinal and afferent input contribute considerably to the locomotor output. 3 Considerable evidence derived from both animal and human experiments suggests that specific afferent input to the spinal cord such as hip proprioceptors, Group-I muscle afferents and plantar cutaneous afferents play a significant role in modulating reflex transmission during walking and standing. One aspect of the sen- sory control of gait is the control of the transition from the stance to swing phase. Both hip and ankle affer- ents responding to stretch and load respectively reset the locomotor rhythm, signifying their impact on the walking pattern. 4,5 Practically the hip joint has to reach a certain extended angle for the swing phase to be initiated, 6 and the extensor muscles to be unloaded. 7 In humans, evidence suggests that hip angle is critical for soleus H-reflex 8 and flexion