Morten Essendrop

A dynamic 3D biomechanical evaluation of the load on the low back during different patient-handling tasks.

The objective of this study was to investigate the low-back loading during common patient-handling tasks. Ten female health care workers without formal training in patient handling performed nine patient-handling tasks including turning, lifting and repositioning a male stroke patient. The low-back loading was quantified by net moment, compression, and shear forces at the L4/L5 joint, measured muscle activity (EMG) in erector spinae muscles and rate of perceived exertion (RPE; Borg scale). The experiments were videotaped with a 50Hz video system using five cameras, and the ground and bedside reaction forces of the health care worker were recorded by means of force platforms and force transducers on the bed. The biomechanical load was calculated using a dynamic 3D seven-segment model of the lower part of the body, and the forces at the L4/L5 joint were estimated by a 14 muscles cross-sectional model of the low back (optimisation procedure). Compression force and torque showed high task dependency whereas the EMG data and the RPE values were more dependent on the subject. The peak compression during two tasks involving lifting the patient (4132/4433N) was significantly higher than all other tasks. Four tasks involving repositioning the patient in the bed (3179/3091/2932/3094N) did not differ, but showed higher peak compression than two tasks turning the patient in the bed (1618/2197N). Thus, in this study the patient-handling tasks could be classified into three groups-characterised by lifting, repositioning or turning-with different levels of peak net torque and compression at the L4/L5 joint.

Biomechanical analysis of the effect of changing patient-handling technique

The objective of the study was to assess the changes in the mechanical load on the low-back when shifting from a self-chosen to a recommended patient-handling technique. Nine female health care workers without formal education in patient-handling carried out 8 different tasks involving moving, turning and lifting situations. By means of a dynamic 3D biomechanical model of the lower part of the body, peak torque, compression and shear forces at the L4/L5 joint were compared using the two different patient-handling techniques. In 5 of the 8 tasks, a significant reduction was observed in spinal loading. Application of the recommended technique decreased the compression value significantly for all tasks with a mean value above 3000 N. For the two tasks with the highest compression values when using the self-chosen technique (4223, 4446 N), the loading was reduced with 36% and 25%, respectively. If the principles behind the recommended technique are implemented and maintained, a decrease in the risk of low-back disorders during patient-handling should thus be expected.

Reliability of isometric muscle strength tests for the trunk, hands and shoulders

The objective of this study was to determine the reliability of isometric muscle strength tests for the trunk, hand and shoulders. At the same time the inadequacy of correlation coefficients as useful manifestation of reliability was highlighted. Nineteen healthy subjects performed a test and retest with exactly 1 week interval. The measurements consisted of recordings of maximal voluntary contractions (MVC) during isometric back flexion, back extension, shoulder elevation, shoulder abduction and handgrip. No habituation to the equipment was made before the initial test since this is often for practical reasons not possible in occupational settings. All Pearson and Intraclass correlation coefficients showed r-values above 0.9. However, a significant increase from test to retest was present in the muscle strength measures for back flexion, back extension and handgrip. In conclusion all tests showed reasonable reliability on group level judged by 95% confidence intervals, however on the individual level the variation was wide according to the calculated limits of agreement. If this variation is not taken into consideration the tests can be of limited use on individual level. Finally, this study clearly showed the inadequacy of correlation coefficients as a single number estimate of reliability.Relevance to industryIn this study we have looked at isometric strength tests, which are applicable at the workplace for measuring shoulder, hand and trunk strength. In the description of the relationship between work demands and workers capacity these measures are important.

Measures of low back function: A review of reproducibility studies

OBJECTIVE The objective of the present study was to make a systematic literature review with preset quality criteria concerning reproducibility of the tests of the low back regarding strength, endurance and range of motion. DESIGN Literature in Medline and local databases was reviewed for articles concerning the reproducibility of strength, endurance, and range of motion measurements. BACKGROUND Measures of low back function are widely used, and are important for both clinical and research purposes in relation to low back problems. A review of the reproducibility of these tests has not previously been made. METHODS After extensive discussion among all the authors, general evaluation parameters were defined for the quality assessment. Every study was graded from 0 to 2 for each parameter. Parameters evaluated were: number of subjects, subject description, method description, test/retest interval, description of results, and statistics. RESULTS The literature search revealed a total of 79 studies. Most studies suffered from methodological weaknesses and only eleven studies received ten or more quality points (maximum 14). The results from the highest graded studies are highlighted. CONCLUSIONS It may be concluded that there is a considerable lack of information about the reproducibility of functional measures for the low back, and therefore a recommendation for consensus is difficult. However, most tests performed in the sagittal plane are reliable for use on groups. RELEVANCE Measures of low back function are thought to be of great importance for clinicians, and low back researchers in general. A review of reproducibility will be helpful both as a survey of tests, and to provide information on the usefulness in relation to the level of reproducibility.

Intra-abdominal pressure and activation of abdominal muscles in highly trained participants during sudden heavy trunk loadings.

Study Design. Ten participants were exposed to heavy sudden trunk loads as they might occur during patient handling. Objectives. The aim was to observe if well-trained men and women use their full rate of intra-abdominal pressure (IAP) development when exposed to heavy sudden trunk loads. Further, to elucidate to what degree the rectus abdominus muscle is activated when the IAP is developed. Summary of Background Data. Well-trained judo fighters are used to heavy sudden trunk loads and can produce a high IAP. It is unknown whether they use their full potential. IAP can increase the spinal stability and has been suggested to unload the spine. The unloading effect will, however, disappear if the development of the IAP demands substantial activity in the vertical fibers of the abdominal muscles. Methods. Five male and five female well-trained judo and jujitsu fighters were exposed to heavy sudden trunk loadings through imitated patient handling situations where the patient fell and the fighters should hold the patient and prevent the fall. IAP was measured with a catheter in the stomach. Along with the IAP measurement, EMG was measured on the abdominal muscles, and the load on the low back was quantified by a three-dimensional dynamic biomechanical calculation of the torques at the L4–L5 joint. Results. The well-trained judo fighters did not use their full potential of the IAP development when exposed to the heavy sudden trunk loads, but the women had to use a higher level of their IAP and extension torque capacity to comply with the heavy loads. The rectus abdominus muscle does not contribute to the IAP development when the trunk is exposed to a sudden heavy load.

The effect of delayed-onset muscle soreness on stretch reflexes in human low back muscles

The aim of the study was to investigate the effect of moderate delayed‐onset muscle soreness (DOMS) on the short latency stretch reflex (SLR) and long latency stretch reflex (LLR) response i.e. electromyographic (EMG) onset latencies and EMG amplitudes in erector spinae (ES). Nine males with muscle soreness (DOMS group) were tested 24, 48 h, and 7 days post‐exercise. Eight males (control group) were tested likewise. EMG was measured from ES bilaterally at the level of L3/L4. The SLR was elicited by mechanically tapping the ES at L3/L4, and the LLR was elicited by sudden loadings of the spine. Significant reductions in force during maximal voluntary contractions and range of motion, and a significant increase in muscle soreness (measured by pressure algometry) and subjective experience of soreness in the low back indicated DOMS 24, and 48 h post‐exercise in the DOMS group. No changes were observed in the control group. The SLR and LLR response were unaffected by DOMS, i.e. no changes in EMG latencies and amplitudes were observed. In conclusion, despite changes in DOMS indicators, the reflex system protecting the stability of the lumbar spine is apparently capable of maintaining an appropriate triggering of SLR and LLR.

Back muscle response to sudden trunk loading can be modified by training among healthcare workers.

Study Design. Experimental study of the effect of physical training on the reaction to sudden back loading. Objective. To investigate the effect and sustainability of “on the job training” on the reaction to sudden back loading among employees at a geriatric ward. Summary of Background Data. Available data suggest that a delayed muscle reflex response to sudden trunk loading may increase the risk of low back injuries. We have previously shown that training may alter the response to sudden trunk loading in healthy subjects and decrease the time elapsed until stopping of the forward movement of the trunk (stopping time). Data on the possibilities of a training-induced improvement in the reflex response among workers exposed to sudden trunk loading on the job are, however, nonexistent, and there is no evidence of long-term benefits, i.e., the sustainability of a positive training effect. Methods. The study included 23 participants and 14 controls. All were healthy without prior history of low back pain (LBP). The training group participated in a total of 18 training sessions during a 9-week period. The training focused on reactions to a variety of sudden trunk loadings. Before and after the training intervention and at a 1-year follow-up, all subjects were tested for their reaction to expected and unexpected sudden trunk loading by applying a horizontal force of 58 N to the upper back of the subjects and measuring the electromyographic (EMG) response from the erector spinae muscles. Results. In the training group, the stopping time and the distance moved after unexpected sudden trunk loading decreased significantly (13%–19%, P = 0.02). The improved stopping time was associated with marked changes in the time-wise distribution of the EMG signal after training. In addition, the follow-up study showed a high sustainability of the training effect. Conclusions. The results demonstrated a training-induced improvement of the response to sudden trunk loading that may be beneficial in workers, such as nurses, who are exposed to sudden trunk perturbations during patient handling.

Fast Development of High Intra-abdominal Pressure When a Trained Participant Is Exposed to Heavy, Sudden Trunk Loads

Study Design. This study focused on intra-abdominal pressure (IAP) during sudden trunk loads. Ten participants were exposed to heavy, sudden trunk loads as they might occur during patient handling. Objectives. The aim was to study the development of intra-abdominal pressure when well-trained participants cope with heavy, sudden trunk loads. It is hypothesized that high IAP develops sufficiently fast to be present when the large torques act on the low-back structures. Summary of Background Data. Well-trained sportsmen expose themselves to heavy sudden loads of the trunk without getting injured, but it is unknown how they cope with these loads. Do they use IAP? IAP is believed to play a significant role in spine stability, but this has only been documented in experimental studies with light trunk loads. Materials and Methods. Ten well-trained judo and jujitsu fighters were exposed to heavy sudden trunk loads through imitated patient handling situations in which the patient fell, and the fighters were to hold the patient and prevent the fall. IAP was measured with a catheter in the stomach. Along with the IAP measurement, the load on the low back during the patient falls was quantified by a three-dimensional dynamic biomechanical calculation of the torques and the compression at the L4/L5 joint. Results. High IAP developed quickly and timed in relation to the external torque when the fighters were exposed to a sudden patient fall. When the trunk load was heavy and sudden, IAP was developed to be present at the time when low-back structures had to cope with the large load. Conclusions. High IAP was developed sufficiently fast to be present when the low-back structures had to cope with the large torques released from the sudden trunk loading.

Short latency stretch reflex in human lumbar paraspinal muscles

The aim of the study was to measure stretch reflex latencies of the lumbar paraspinal muscles. An electromechanical tapping system was constructed enabling an accurate estimation of short latencies by utilizing a new technique combining results for different tapping durations. Latency parameters (onset, peak and zero-crossing of EMG signal) were obtained for the paraspinal muscles at the L3/L4 level for 10 male subjects. Detection of EMG onset, which was determined by a threshold criterion (2.5 S.D. of pre-activity), yielded 7.4+/-1.4 ms corresponding to a physiological short latency onset of 6.5 ms, which is considerably shorter than previously reported. However, it is shown to be consistent with the expected latency value for a monosynaptic stretch reflex for the paraspinal muscles of the low back.

Measures of low back function: a review of reproducibility studies

Abstract Objective . The objective of the present study was to make a systematic literature review with preset quality criteria concerning reproducibility of the tests of the low back regarding strength, endurance and range of motion. Design . Literature in Medline and local databases was reviewed for articles concerning the reproducibility of strength, endurance, and range of motion measurements. Background . Measures of low back function are widely used, and are important for both clinical and research purposes in relation to low back problems. A review of the reproducibility of these tests has not previously been made. Methods . After extensive discussion among all the authors, general evaluation parameters were defined for the quality assessment. Every study was graded from 0 to 2 for each parameter. Parameters evaluated were: number of subjects, subject description, method description, test/retest interval, description of results, and statistics. Results . The literature search revealed a total of 79 studies. Most studies suffered from methodological weaknesses and only 11 studies received 10 or more quality points (maximum 14). The results from the highest graded studies are highlighted. Conclusions . It may be concluded that there is a considerable lack of information about the reproducibility of functional measures for the low back, and, therefore, a recommendation for consensus is difficult. However, most tests performed in the sagittal plane are reliable for use on groups. Relevance . Measures of low back function are thought to be of great importance for clinicians, and low back researchers in general. A review of reproducibility will be helpful both as a survey of tests, and to provide information on the usefulness in relation to the level of reproducibility.