Responses of Hoffman-reflex in human soleus to gravity and/or fluid shift.

Responses of Hoffman (H)-reflex in human soleus to changes in the levels of gravity, activities of skeletal muscles, and/or fluid distribution of lower limbs during the parabolic flight of a jet airplane and/or using a tilting table were studied. The time interval between the electrical stimulation and the appearance of either M- or H-wave and the amplitude of M-wave were not influenced by the changes in gravity and fluid distribution levels. However, the H-wave amplitude was increased when the subjects were exposed to microgravity (microgravity-G).