Abstract of the 68th Meeting (Spring Meeting) 6–9 March 1990, Heidelberg

Short and long latency reflex responses elicited by electrical and mechanical stimulation in human hand muscle

The relationship between electrically and mechanically induced reflex responses in the rectified, averaged surface electromyogram of the first interosseus dorsalis muscle was examined in 18 healthy human subjects. Both methods evoked identifiable short and long latency reflex responses. The onset latencies for short latency reflexes with electrical and mechanical stimulations were 30.6 ms (+/- 2.2 ms) and 28.9 ms (+/- 2.2 ms) and for long latency reflexes 50.0 ms (+/- 2.8 ms) and 51.2 ms (+/- 5.2 ms), respectively. The correlation of the onset latencies of the reflexes revealed significant correspondence between the electrical and mechanical methods implying at least partly mutual mechanism…

Mechanically induced reflex responses in human triceps brachii.

The short and long latency reflex responses of human triceps brachii muscle were recorded in 14 healthy volunteers. An electromechanical hammer was used to stretch the muscle and recordings were made from a surface electromyogram. The monosynaptic tendon reflex occurred at a mean latency of 12.5 ms (SE 0.7 ms). Later responses were observed in activated conditions (weak force production, preparatory period) at a mean latency of 62.8 ms (SE 3.5 ms). The amplitude of the short latency reflex increased during weak tension, the long latency reflex amplitude seemed to increase during the preparatory period testing. The amplitude increases can be attributed to increased lower motoneuron excitabil…

Changes in the probability of firing of motor units following electrical stimulation in human limb muscles

Changes in the probability of motor unit firing was studied in ten different muscles (six muscles in the upper extremity and four muscles in the lower extremity) of eleven healthy human subjects. The responses were elicited by the electrical stimulation of cutaneous or mixed nerves during weak voluntary contraction of the muscle studied, and were recorded by averaging the rectified surface electromyogram. In eight of the ten muscles, well-detectable, short and long latency excitatory phases were observed. The most constant and well-identified excitatory responses were observed in the first interosseus dorsalis muscle in the hand, and in the extensor digitorum brevis muscle in the foot. Thes…