Biomedical subjects

H A Seelen

Publications and source records attributed to H A Seelen.

10 recordsLinked to original sources

PubMed2001

Motor preparation in postural control in seated spinal cord injured people.

Spinal cord injured (SCI) people try to compensate for the loss of postural muscle function by increased use of non-postural muscles. Such alternative muscle use, however, may necessitate important modifications in motor control. In this study motor programming processes were investigated in three groups, i.e. in high thoracic SCI, low thoracic SCI and non-SCI subjects. A bimanual forward-reaching task, in which graded sitting balance perturbation was systematically invoked, was presented to the subjects as a visual precue choice reaction time (RT) task. Effects of movement preparation were examined by precuing reaching distance information. RT and movement times were recorded. Centre of pressure (CP) displacement was used as an indicator for sitting balance perturbation. Results indicated that high thoracic SCI subjects programmed balance-perturbing reaching movements as fast as did non-SCI subjects. Low thoracic SCI subjects, on the other hand, showed substantially longer programming times. This latter outcome is consistent with the hypothesis that the low thoracic SCI subjects adopted a more complex postural control strategy involving residual motor functions in an attempt to actively compensate for loss of postural muscle function. High thoracic SCI subjects, on the other hand, appeared to adopt a less complex and thus easier to programme postural control strategy.

Adult↗

PubMed2001

Evaluation of effect of ankle-foot orthosis use on strength restoration of paretic dorsiflexors.

OBJECTIVE: To assess whether a difference exists in restoration of strength between patients with a recent paresis of the dorsiflexors of the ankle using an ankle-foot orthosis (AFO) and patients without an AFO. DESIGN: Prospective case-control study. SETTING: Patients from regional hospitals, tested in a rehabilitation research center. PARTICIPANTS: Twenty-nine patients with a recent (6wk-1yr) peripheral paresis, alternately assigned to a group using an AFO or a control group. There was no significant difference in duration of the paresis and in torque at entering the study (T0) between the 2 groups. INTERVENTIONS: The use of an ankle-foot orthosis. MAIN OUTCOME MEASURES: Isometric torque production of ankle dorsiflexors, expressed as ratio of paretic and healthy side, in 2 measurement sessions, over a period of 6 weeks (T0-T6) with the ankle in 0 degrees and 30 degrees plantarflexion. RESULTS: Both groups had significant restoration of strength +/- standard deviation between T0 and T6 in 30 degrees flexion: non-AFO group 17% +/- 15%, AFO group 9% +/- 12%. No significant difference existed between the 2 groups (30 degrees p = .56). No significant shift in strength ratio 0 degrees :30 degrees occurred (AFO group p = .82). CONCLUSION: The use of an orthosis does not influence restoration of strength in patients with a recent peripheral paresis of the ankle dorsiflexors.

Adult↗

PubMed2001

Physical activity in daily life in patients with chronic low back pain.

OBJECTIVES: To evaluate disuse (ie, a decreased daily physical activity level) in patients with chronic low back pain (LBP) and to evaluate the construct validity of accelerometry for measuring physical activity in daily life. DESIGN: Case-control study in a cross-sectional design; comparison of accelerometry to the criterion standard (doubly labeled water technique). SETTING: Normal daily living (unrestricted by the measurement devices). PATIENTS: Thirteen patients with chronic nonspecific LBP and 13 age- and gender-matched healthy controls. MAIN OUTCOME MEASURES: Physical activity in daily life, expressed as whole-body acceleration measured with a triaxial accelerometer (Tracmor), and as the ratio between average daily metabolic rate (ADMR), measured by the doubly labeled water technique, and resting metabolic rate (RMR), measured by the ventilated hood. Both techniques were used simultaneously for 14 days. RESULTS: Mean physical activity level in patients and controls did not differ significantly. The correlation between the Tracmor and ADMR and RMR was .72 (p < .01). CONCLUSIONS: Decreased physical activity levels in this sample of chronic LBP patients was not confirmed. The Tracmor is a valid instrument for measuring daily activity in LBP patients.

Activities of Daily Living↗

PubMed2001

The effect of seat tilting on pelvic position, balance control, and compensatory postural muscle use in paraplegic subjects.

OBJECTIVE: To study the effect of seat tilting on pelvic tilt, balance control, and postural muscle use in persons with a thoracic spinal cord injury (SCI). DESIGN: Cross-sectional group study. SETTING: Rehabilitation centers and rehabilitation hospital departments. PATIENTS: Ten complete high thoracic SCI (level T2-8) patients, 10 complete low thoracic SCI (level T9-12) patients, and 10 matched able-bodied controls. INTERVENTION: A 10 degrees forward inclination of the seat. MAIN OUTCOME MEASURES: Pelvic tilt, center of pressure displacement, and muscle activity. RESULTS: Anterior tilting of the pelvis as a result of forward inclination of the seat could not be shown, either in persons with or without SCI. Balance control was not influenced by forward inclination of the seat. Participants' overall muscle activity decreased while they were seated in the chair with the forwardly inclined seat. CONCLUSIONS: Evidence provided by the kinematic and electromyographic data is not sufficient to develop a protocol for wheelchair prescription on the basis of pelvic positioning.

Adult↗

PubMed2000

Chair configuration and balance control in persons with spinal cord injury.

OBJECTIVE: To study whether chair configuration influences sitting balance in persons with spinal cord injury (SCI). DESIGN: Cross-sectional group study. SETTING: Rehabilitation centers and hospital rehabilitation departments. PATIENTS: Ten complete high thoracic SCI (level T2-T8) patients, 10 complete low thoracic SCI (T9-T12) patients, and 10 matched able-bodied controls. SCI participants had completed their active rehabilitation at least 6 months before the study. INTERVENTIONS: A balance-changing (forward) reaching task while seated in four differently configured chairs. Tilt angle (7 degrees and 12 degrees) and reclination angle (22 degrees) were varied relative to a standard chair configuration (10 degrees reclination). MAIN OUTCOME MEASURES: Maximal unsupported reaching distance, center-of-pressure displacement and muscle activity. RESULTS: Although no significant difference in actively controllable reach was found in controls or in subjects with low SCI, sitting balance improved in all chairs relative to the standard chair. Ability to control displacement of arms and trunk during reaching improved. No apparent need for additional postural muscle activity was found. Persons with high SCI did not improve their sitting balance. They were unable to control a shift in body mass larger than the one induced by arm movement. However, they had less muscle activity after backrest reclination or tilting the chair backwards. CONCLUSIONS: The tested chairs had an overall positive effect. However, for individually tailored chair configurations factors other than those investigated should be considered.

Adult↗

PubMed2000

Effect of immobilization on ankle dorsiflexion strength.

This study was performed in order to determine the loss of strength of the dorsiflexors in healthy persons after immobilization of the ankle, and the ability of these muscles to regain strength. First, isometric ankle dorsiflexion strength was measured in 33 healthy male and 39 female subjects in age categories 20-40 and 40-80 years, in order to obtain reference data and to determine the reproducibility of the measurement protocol. Gender, age and ankle position had a significant influence on the ankle dorsiflexion torque. Secondly, torque was measured in 15 patients after 4-6 weeks' immobilization of the ankle due to a fracture. A 28% decrease in dorsiflexion torque was seen. Strength reduction in neutral position and in 30 degrees plantar flexion was not significantly different. Without specific therapy restoration of torque was almost complete 6 weeks after cast removal.

Adult↗

PubMed1999

Postural muscle responses in the spinal cord injured persons during forward reaching.

To compensate for postural muscle function loss spinal cord injured (SCI) people have to use parts of the sensorimotor system which are still intact. In this study, postural control was investigated in high and low thoracic SCI people and in able-bodied controls, using a bimanual forward-reaching task. Muscle activity was recorded bilaterally from the erector spinae (ES) at level L3, T9 and T3, latissimus dorsi (LD), ascending part of the trapezius muscle (TPA), serratus anterior (SA), sternocostal head of the pectoralis major (PM) and the oblique abdominal muscles (OA) by means of surface electromyography. Sitting balance was monitored by measuring the changes in the location of the centre of pressure (CP) using a force platform. Muscle activity analyzed in different phases of the movement showed that SCI people adopt different postural adjustments to face the balance changes due to the reaching movement. SCI people make alternative use of non-postural muscles like the LD and TPA to maintain their sitting balance.

Adaptation, Physiological↗

PubMed1998

Development of new muscle synergies in postural control in spinal cord injured subjects.

The development of new patterns of postural control in patients with a complete thoracic spinal cord injury (SCI) during their active clinical rehabilitation was studied. Especially the role of non-postural muscles, like the latissimus dorsi (LD) and the trapezius pars ascendens (TPA), in maintaining and restoring sitting balance during standardized bimanual task performance was investigated. Twelve patients, diagnosed with an acute complete thoracic SCI between spinal cord level T2 and T12, participated in a longitudinal experimental study. Changes in the centre of pressure (CP) and electromyographic activity of the erector spinae (ES) at level L3, T9 and T3, the LD, the TPA, the pectoralis major (PM), the serratus anterior and the oblique abdominal muscles were investigated at several moments in the rehabilitation process. Results show a gradual development of specific muscle activation patterns for both high and low thoracic SCI patients. These patterns seem to be related to a combination of restoration of function of the ES-L3 and ES-T9 in the low thoracic SCI subjects and increased compensatory muscle use of the LD, TPA and PM in high SCI patients. The range in which low thoracic SCI patients can actively vary their CP increased slightly during rehabilitation.

Adolescent↗

PubMed1998

Postural motor programming in paraplegic patients during rehabilitation.

One of the basic aims in the rehabilitation of thoracic spinal cord injured (SCI) patients concerns the regaining of sitting posture control. This implies the development of new postural strategies requiring the adjustment of motor programming processes. The aim of this study was to investigate the time course of postural reorganization during active, clinical rehabilitation of thoracic SCI patients with different SCI levels. Thus changes in motor programming in sitting balance control were investigated in two groups of complete low or high thoracic SCI patients. At several stages during the rehabilitation process an experiment was held in which sitting posture was perturbed systematically using submaximal reaching movements over four reaching distances. This bimanual reaching task was presented as a visual precue choice reaction time (RT) task in which reaching distance (i.e. grade of postural perturbation) was precued. Results indicated that in both high and low thoracic SCI patients RTs in movements involving postural perturbation became shorter during the course of the rehabilitation period. However, low thoracic SCI patients were generally slower in the programming of balance perturbing movements than high thoracic SCI patients, a phenomenon that did not change over time. Furthermore, initial differences in RTs as a function of grade of postural perturbation disappeared in both groups in the course of the rehabilitation phase. Precue benefit, equally large for both groups, did not change as a function of rehabilitation time. It is concluded that the observed phenomena signify the gradual development of new central postural control processes in both SCI groups during rehabilitation. Low thoracic SCI patients, having more residual sensorimotor functions, seem to adopt more complex strategies in maintaining and restoring sitting balance that take longer to specify and to programme. High thoracic SCI patients seem to rely on simpler strategies using more passive postural support.

Adolescent↗

PubMed1991

Compensatory muscle activity for sitting posture during upper extremity task performance in paraplegic persons.

Compensation for the loss of postural activity of the erector spinae (ES) muscle in spinal cord injured (SCI) subjects was investigated. All SCI subjects had clinically complete lesions below the T3 level. Body disbalance was invoked by requiring sitting subjects to execute reaching movements over individually predetermined distances in a horizontal plane. Myoelectric activity of the latissimus dorsi (LD) muscle and the trapezius pars ascendens (TPA) muscle both in the SCI subjects and in controls was recorded. The body disbalance was measured in terms of changes in the position of the body centre of gravity. The effects of anticipation for body displacement were examined by cuing the direction of the reaching movement. Our results indicate that paraplegic subjects use both LD and TPA to stabilize their sitting posture, in contrast to non-disabled persons. Secondly, the movement anticipation is in general slower in persons with paraplegia. Furthermore, the paraplegic subjects showed considerable impairments concerning the processing of precued information prior to a goal-directed upper extremity movement.

Adolescent↗