MONOPOLAR NEEDLE EVALUATION OF PARASPINAL MUSCULATURE IN THE CERVICAL, THORACIC, AND LUMBAR REGIONS AND THE EFFECTS OF AGING

Motor unit characteristics (phases, turns, amplitude, duration, and area) were measured using a monopolar needle and narrowed bandpass (500 Hz to 10 kHz) in cervical, thoracic, and lumbar paraspinal muscles in 66 subjects (36 women and 30 men) aged 22-81 years (mean age 45.7 years). Cervical motor units were of lower amplitude and area than thoracic and lumbar motor units (P = 0.0001), respectively. The durations of lumbar motor units were longer and larger than cervical and thoracic motor units (P = 0.0004). Analysis of covariance of the measured characteristics against age showed no significance in the cervical and thoracic regions. In lumbar paraspinal motor units, phases and turns increased significantly with age (P = 0.044 and P = 0.016, respectively). The increase was <1.0 phase over 30 years. Motor unit amplitude increased with aging (P = 0.055) showing an increase of 360 mu V over a 30-year time period, It is appropriate to assess the number of phases and turns, as well as the duration of the motor units in the cervical and thoracic (but not lumbar) spines in addition to seeking evidence of spontaneous, single fiber discharges. (C) 1995 John Wiley and Sons, Inc.