Gary L Soderberg

Synergistic muscle activation during maximum voluntary contractions in children with and without spastic cerebral palsy.

We examined muscle recruitment patterns in children with cerebral palsy (CP) and comparison children without CP under conditions of maximum voluntary contractions. Three groups of children participated in the study: (1) 12 children with diplegic CP (eight males, four females; age range 4-10 y, mean age 7 y [SD 2 y 4 mo]); (2) six children with hemiplegic CP (four males, two females; age range 5-10 y, mean age 7 y 4 mo [SD 2 y]); and (3) 13 comparison children with normal motor function (seven males, six females; age range 4-11 y, mean age 7 y 2 mo, [SD 2 y]). The children with CP were classified according to the Gross Motor Function Classification System: eight were Level I, five were Level II, four were Level III, and one was Level IV. Surface electromyography was recorded from four proximal and distal lower extremity (LE) muscles. Children with CP more frequently activated a muscle other than the intended prime mover first, compared with the comparison children, especially when the prime mover was a distal muscle. For example, during ankle plantar flexion, when the lateral gastrocnemius muscle was the prime mover, children with hemiplegia showed preactivation of the tibialis anterior muscle and children with diplegia showed medial hamstring coactivation. In conclusion, children with CP showed considerable differences to the comparison children in how LE muscles were voluntarily activated. Greater understanding of muscle recruitment patterns under a variety of tasks may provide new directions for motor control retraining or other forms of intervention.

Co-Activity during Maximum Voluntary Contraction: A Study of Four Lower-Extremity Muscles in Children with and without Cerebral Palsy.

This study was designed to determine whether children with cerebral palsy (CP) showed more co‐activity than comparison children in non‐prime mover muscles with regard to the prime mover during maximum voluntary isometric contraction (MVIC) of four lower‐extremity muscles. Fourteen children with spastic diplegic CP (10 males, four females; age range 4–10y), seven children with spastic hemiplegic CP (five males, two females; age range 5–10y), and 14 comparison children (eight males, six females; age range 4–11y) participated in the study. Gross Motor Function Classification System levels of the children with CP were as follows: eight children at Level I, seven children at Level II, five children at Level III, and one child at Level I V. Surface electromyographic recordings were made simultaneously from the vastus lateralis (VL), medial hamstrings (MH), tibialis anterior, and lateral gastrocnemius (LG) muscles during maximal voluntary contraction. Children with CP showed higher co‐activity than the comparison children in both antagonist and adjacent muscles. This was particularly true when VL, MH, or LG muscles were engaged in MVIC. These findings may contribute to the weakness and abnormal movement patterns seen in CP, and they have implications for treatment.

An EMG Analysis of Posterior Trunk Musculature during Flat and Anteriorly Inclined Sitting

The purpose of this study was to determine the differences in the electromyographic (EMG) activity of the posterior musculature of the trunk while subjects were first seated on a conventional chair, and then while the chair surface was inclined anteriorly to 100 and 110 deg. Twenty healthy subjects had electrodes applied lateral to the spinous processes of C6, T10, and L3 while EMG was monitored every other minute for 15 minutes. All subjects assumed each posture and used a keyboard to operate an interactive computer terminal. Before analysis, all data were processed by root-mean-square circuit and normalized to the EMG from maximum voluntary contractions. Analyses of variance showed significant differences (p < 0.0005) between postures; the EMG activity was found to be less with greater inclination of the chair seat.

Comparison of skeletal muscle motor unit discharge characteristics in young and aged humans

The purpose of this study was to determine the discharge characteristics of motor unit action potentials. Three decades of aged subjects ranging from 60 to 90 yr of age were compared to a group of 20-35 yr olds. Motor unit behavior was described by the interspike interval (ISI) and expressed statistically as a mean, a floating standard deviation (FSD), and a floating serial correlation (FRHO). The 70- to 79-yr-old group tended to have a slow motor unit discharge rate, an increased variability of discharge (FSD) and a negative serial correlation coefficient (FRHO). All three factors describing motor unit discharge behavior possibly suggest substitution of larger motor units for small motor units normally active at low tensions for the 70-79 age group.

Priorities for Publication

A number of readers and those who have submitted manuscripts to Physical Therapy have asked how a manuscript gets accepted. The Style Manual for Physical Therapy and the 1986 April Guest Editorial in the Journal discuss the mechanics of manuscript submission and review and the qualities of good research. Not all good manuscripts and research, however, can be published in Physical Therapy. Occasionally in the past, and probably more frequently in the future, a number of manuscripts, some of which are excellent, will be rejected for publication. Although some manuscripts simply are not appropriate to Physical Therapy, other manuscripts might be of interest to a very limited audience of physical therapists. To best use the limited publication space in the Journal, the Associate Editors and the Editor have developed a list of priorities for future publications.… [ ARTICLE][1] [1]: /lookup/volpage/66/501?iss=4