• Jesper Hedegaard Rasmussen
  • Søren Simonsen Dueholm
H-reflexes are well documented as a tool to estimate the synaptic activity of the motoneuron pool. Only little research has focused on the modulation of Hreflexes in the hamstring muscle group (HMG) despite their importance in human gait. The aim was to design and validate a new technique to stimulate the sciatic nerve and to evaluate the intersession reliability of this techniques’ ability to elicit H-reflexes in the HMG. 12 healthy subjects (25.58§0.99 yrs) lying in prone position were applied electrical stimuli through a custom-made 4x2 grid electrode (cathode) placed two cm below the buttocks with anode placed above trochanter major of the dominant leg. Optimal cathode site was found by applying stimuli 25% above the threshold of Ia afferents to each grid site. sEMG was recorded from the long and the short heads of biceps femoris (LH-BF and SH-BF), semitendinosus (SEMI), soleus (SOL) and tibialis anterior (TA). SOL and TA were control muscles. Stimuli were applied at the optimal cathode site (10 to 100 mA) and Hmax, and the latencies for M-waves and H-reflexes were extracted as parameters. Two identical sessions were conducted one day apart and intraclass correlation coefficients (ICC) were calculated for each parameter within each muscle. Data showed reliable Hmax ICCs for LH-BF (0.967), SH-BF (0.762) and SEMI (0.736). ICC values for M-wave- and H-reflex latencies for LH-BF (0.931 and 0.993), SH-BF (0.935 and 0.99) and SEMI (0.7 and 0.978) were considered reliable according to the benchmarks of Landis and Koch (1977). H-reflexes were observed in SOL and TA. The novel technique provided reliable H-reflexes in the HMG, and can be used as a tool to investigate synaptic activity in the motoneuron pool. The technique might be able to test the interaction between leg muscles.
Publication date4 Jun 2013
Number of pages64
ID: 77227502