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 ar ea) 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 year s). Cervical motor units were of lower amplitude and area than thoraci c and lumbar motor units (P = 0.0001), respectively. The durations of lumbar motor units were longer and larger than cervical and thoracic m otor units (P = 0.0004). Analysis of covariance of the measured charac teristics against age showed no significance in the cervical and thora cic regions. In lumbar paraspinal motor units, phases and turns increa sed significantly with age (P = 0.044 and P = 0.016, respectively). Th e increase was <1.0 phase over 30 years. Motor unit amplitude increase d with aging (P = 0.055) showing an increase of 360 mu V over a 30-yea r time period, It is appropriate to assess the number of phases and tu rns, as well as the duration of the motor units in the cervical and th oracic (but not lumbar) spines in addition to seeking evidence of spon taneous, single fiber discharges. (C) 1995 John Wiley and Sons, Inc.