The Landau reaction: a clinical and electromyographic analysis.
Thirty normal infants aged two months (N=10), five months (N=11) and eight months (N=9) participated in a three-month longitudinal study of the Landau reaction. Each infant's response to horizontal suspension was filmed and electromyographically recorded. Thoraco-lumbar extension and head elevation 90 degrees above the horizontal (face vertical to the horizontal) were present in 45 per cent of infants at four months and in 90 per cent of infants between five and 10 months. The postural response changed little between five and ten months of age. Less than 10 per cent of the infants regressed in postural response between monthly examinations. No infant hung limply over the examiner's hand, and electromyographic activity of the neck extensors never decreased to zero. All infants were able to reassume neck and spinal extension following active and passive flexion of the neck. Kicking activity was observed in 80 per cent of infants over four months of age. A pattern of motor responses for the normal infant was noted and variations from this pattern which have been observed in infants with motor dysfunction are discussed. The EMG recordings correlated well with the visual observations and provided an accurate written record of the responses. They proved to be a reliable research tool in the study of infants' gross motor responses.