Validity and reliability of self-assessed physical fitness using visual analogue scales.

To test the validity and reliability of self-assessed physical fitness samples included healthcare assistants working at a hospital (women=170, men=17), persons working with physically and mentally handicapped patients (women=530, men= 123), and two separate groups of healthcare students (a) women=91 and men=5 and (b) women=159 and men=10. Five components of physical fitness were self-assessed by Visual Analogue Scales with illustrations and verbal anchors for the extremes: aerobic fitness, muscle strength, endurance, flexibility, and balance. Convergent and divergent validity were evaluated by age-adjusted correlations stratified by sex with performance-based measures of physical fitness. Self-assessed aerobic fitness (r = .36 - .64) (women/men), muscle strength (r = .30 - .51), and flexibility (r = .36 - .31) showed moderate convergent validity. The divergent validity was satisfactory except for flexibility among men. The reliability was moderate to good (ICC = .62 - .80). Self-assessed aerobic fitness, muscle strength, and flexibility showed moderate construct validity and moderate to good reliability using visual analogues.

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.

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.

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.

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.

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.

Training can modify back muscle response to sudden trunk loading.

Sudden, unexpected loading to the trunk has been reported in the literature as a potential cause of low-back disorders. This study's aim was to investigate the effect of "readiness training" on the response to sudden back loading among untrained healthy individuals. The study included 19 participants and 19 matched controls. All were employees at the National Institute of Occupational Health. The participants received ten 45-min training sessions during a 4-week period. The training focused on reactions to a variety of expected and unexpected sudden trunk loadings, including balance and coordination exercises. Before and after the training, all subjects were tested for reaction to sudden trunk loading (SL). This entailed applying a horizontal force of 58 N to the subject's upper back. Elapsed time--measured between SL and stopping--decreased significantly in the training group (from 337 to 311 ms) compared with the control group. The improved stopping time was associated with a changed EMG signal, characterized by an increase in the early parts of the response (up to 225 ms) and a subsequent decrease. EMG onset latency was unaffected by training. This study is apparently one of the first to demonstrate that the response to sudden trunk loading can be improved in healthy subjects without an increase in pre-activation and associated trunk stiffness. In perspective, the results indicate a possibility for a training-induced reduction of the risk of low-back injuries, e.g., in nurses exposed to sudden trunk perturbations during patient handling.