What is the effect of taping along or across a muscle on motoneurone excitability? A study using triceps surae

Taping along the skin overlying lower trapezius reduces motoneurone excitability in healthy subjects [Alexander, C.M., Stynes, S., Thomas, A., Lewis, J., Harison, P.J., 2003. Does tape facilitate or inhibit the lower fibres of trapezius? Manual Therapy 8, 37-41]. It remains unclear whether this effect is: (a) specific to trapezius and (b) specific to the direction of application of the tape. In light of this, the excitability of another muscle was measured in order to see if these results were repeatable and independent of the muscle taped. Thus, the excitability of the medial and lateral gastrocnemius (MG and LG) and soleus (Sol) motoneurone pool was assessed using the Hoffman reflex (H reflex). The amplitude of this reflex was measured with the tape aligned across and then along the direction of the MG muscle fibres. Tape aligned across the fibres failed to affect motoneurone excitability (MG P=0.61, LG P=0.69, Sol P=0.17). Under tape and sports tape applied together aligned along the MG muscle reduced the excitability of both MG and LG (19% (P=0.01) and 13% (P=0.01), respectively). These observations suggest that any change to movement patterns with tape application cannot be explained by facilitation of the motoneurone excitability.