Monosynaptic spinal reflexes elicited at various phases of the EEG alpha cycle

Autonomic nervous system activities during motor imagery in elite athletes

Motor imagery (MI), a mental simulation of voluntary motor actions, has been used as a training method for athletes for many years. It is possible that MI techniques might similarly be useful as part of rehabilitative strategies to help people regain skills lost as a consequence of diseases or stroke. Mental activity and stress induce several different autonomic responses as part of the behavioral response to movement (e.g., motor anticipation) and as part of the central planning and preprogramming of movement. However, the interrelationships between MI, the autonomic responses, and the motor system have not yet been worked out. The authors compare a number of autonomic responses (respiration, heart rate, electro skin resistance) and motoneuron excitability (soleus H-reflex) in elite and nonelite speed skaters during MI. In contrast to the nonelite athletes, MI of elite speed skaters is characterized by larger changes in heart rate and respiration, a greater reliance on an internal perspective for MI, a more vivid MI, a more accurate correspondence between the MI and actual race times, and decreased motoneuron excitability. Two observations suggest that the changes in the autonomic responses and motoneuron excitability for the elite speed skaters are related to the effects of central motor programming: (1) there was no correlation between the autonomic responses for MI and those recorded during mental arithmetic; and (2) mental arithmetic did not significantly alter motoneuron activity. It is suggested that in elite speed skaters, the descending neural mechanisms that reduce motoneuron excitability are activated even when full, vivid MI is performed internally. These inhibitory responses of the motor system may enhance actual motor performance under conditions of remarkably high mental stress, such as that which occurs in the Olympic games.

Amplitude reduction of H-reflex during mental movement simulation in elite athletes

In order to investigate the changes of motoneuron excitability during mental simulation of a voluntary movement (motor imagery; MI), the soleus H-reflex and several activities of autonomic effectors were recorded simultaneously when MI of speed skate sprint was performed. The subjects were seven elite speed skate athletes ranging in age from 18 to 24 years old. They were all skilled in MI, and could imagine full vivid skating movement internally as if they were really exercising. The subjects were awake, relaxed and blindfolded. At first, rest (5 min), positive relaxation (4 min) and concentration periods (2.5 min) were set up. Then, after the previous announcement for the start, MI was initiated by the sound of a signal gun which was recorded by a tape recorder. MIs were continued for each subject from about 36 s to 38 s, and these imaging times were very close to the actual personal best records of each subject. The autonomic effectors represented by skin conductance response (SCR), heart rate (HR), and respiration rate (RSR) became remarkably active during MI in all trials. SCR was increased by 51% on the average. Furthermore, HR and RSR were increased by 57% and 76% respectively, compared with those during resting period. These changes in the autonomic effectors were all significant and were those which were activated in actual movements. The amplitudes of H-reflex were almost all constant before MI initiation. However, the reduction of the H-reflex amplitude arose just after the start and lasted to the end of MI.(ABSTRACT TRUNCATED AT 250 WORDS)