MEASURES OF PARASPINAL MUSCLE PERFORMANCE DO NOT PREDICT INITIAL TRUNK KINEMATICS AFTER TRIPPING

The ability to limit the trunk flexion associated with an anteriorly d irected trip is a determinant of successful recovery of recovering pos tural stability and is subservient to rapidly detecting and correcting the imposed trunk flexion in the available time. This experiment test ed the hypothesis that subjects demonstrating greater eccentric trunk/ hip extension strength, faster voluntary reaction times, shorter autom atic response latencies, and larger automatic activation amplitudes of the paraspinal muscles, would demonstrate less trunk flexion followin g a trip. An isokinetic protocol was used to obtain measures of trunk extension strength, response latencies, and activation amplitudes. Mot ion analysis methods were used to quantify trunk kinematics during the positioning phase of recovery following an induced trip. Statisticall y significant and functionally meaningful relationships between eccent ric strength of the trunk/hip extensors, voluntary-reaction time, auto matic reaction time, activation amplitudes and trunk kinematics failed so emerge. Thus, although automatic and voluntary paraspinal muscle r esponses have the potential to limit trunk flexion during the position ing phase of recovery, the task may be achieved through intersegmental factors or other muscular sources such as the gluteus maximus and ham strings. Published by Elsevier Science Ltd.