Ramp-and-hold force control in the upper and lower lips: developing new neuromotor assessment applications in traumatically brain injured adults.

The relation among several parameters of the ramp-and-hold force contraction and target force level was quantified for the upper and lower lip in 40 normal adults and in 4 young adults who had sustained traumatic brain injury (TBI). Using visual feedback, subjects produced ramp-and-hold compression lip forces as rapidly and accurately as possible to end-point target levels ranging from 0.25 to 2.00 newtons. In normal adults, significant positive linear relations were found between the parameters of the ramp-and-hold lip force task and target force level, including the peak rate of force change, peak force, and the mean and standard deviation of force during the hold phase. Though males and females have been shown to differ greatly on absolute maximum force-generating capabilities, they are virtually identical on the measures used to quantify the lip force ramp-and-hold task over the range of compression forces studied. Preliminary investigation of lip force control in 4 TBI subjects suggests that these quantitative measures are useful in determining the distribution and nature of motor impairment between the upper and lower lips during a dynamic force control task.