Kinematics and muscle activities of the lumbar spine during and after working in stooped postures

Enabling context aware data analysis for long-duration repetitive stooped work through human activity recognition in sheep shearing

There is evidence to suggest that changes in kinematics and neuromuscular control in activities that take place over long periods of time lead to increased injury risk. The collection of biometric data over long time periods could provide insight into these injuries. However, it is difficult to analyse long period biometric data for occupations as the analysis depends on the activity being performed, and it is not practical to manually label the amount of data required. A sufficiently accurate human activity recognition algorithm can provide a means to segment the activities and allow this analysis, but the classification must be robust to the inter-individual differences, as well as the intra-individual variations in movement over time that are the target of analysis. This work presents a person-independent human activity recognition algorithm for sheep shearing using a Hidden Markov Model with physical features that are identified to be relevant to spinal movement quality. The classifier achieved an F1 score of 96.47% in identifying the shearing task.

The immediate and prolonged effects of military body armor on the relative timing of thorax and pelvis rotations during toe-touch and two-legged squat tasks

Although military body armor is an effective life saver, it considerably loads more weight on the warfighters, increasing the risk of musculoskeletal injury. This study investigated the immediate and prolonged effects of wearing body armor on timing aspect of lumbo-pelvic coordination during the toe-touch (TT) and two-legged-squat (TLS) tests. A cross-over study design was used wherein twelve asymptomatic and gender-balanced individuals completed two experimental sessions with and without body armor. A session included two similar sets of tests, before and after exposure to a treadmill walk, containing a TT and a TLS test with ten cycles of fast bending and return. Reflective markers were attached on the participants to capture the kinematics of body segments in conjunction with a motion capture system. The mean absolute relative phase (MARP) and deviation phase (DP) between the thorax and pelvis were calculated for each test. The pre-walk MARP in the return was significantly larger with versus without body armor (p = 0.022), while there were no significant effects of body armor on the other outcome measures. In addition, the pre-walk MARP and DP in the bending and return, as well as the walk-induced changes in the MARP in the bending phase were significantly larger in TLS versus TT (p < 0.026). Therefore, using a body armor immediately made the lumbo-pelvic coordination less in-phase during return, but no prolonged effects were found. Further investigation is necessary to specify chances wearing a body armor increases the risk of musculoskeletal injuries in the lower back and lower extremities joints.

The Ipswich Microbreak Technique to alleviate neck and shoulder discomfort during microscopic procedures

Neck and shoulder disorders are a considerable health problem amongst frequent microscope users. We aimed to investigate the neck and shoulder discomfort experienced during prolonged microscopic activity and to assess the benefits of minibreaks. A prospective crossover study was performed on 17 healthy volunteers sitting still while looking down a bench with and without the Ipswich Microbreak Technique (IMT). We used a subjective measure of time to fatigue and pain in the neck and shoulder regions as well as objective readings from a surface electromyogram (sEMG). The IMT delayed the sensation of pain in the neck and shoulder region while reducing the overall sEMG muscle activation. In conclusion, IMT is a useful strategy in reducing and delaying the pain in neck and shoulder from prolonged working under the microscope. This technique can be incorporated in other activities that involve a sustained stationary position.

Effects of varying the rest period on the onset angle of lumbar flexion-relaxation in simulated sheep shearing: a preliminary study

Wool harvesting remains an important industry in Australia, but its workers suffer from extreme rates of injury, in particular, the lower back injuries. Reducing injuries in sheep shearing could be as simple as extending shearer rest periods between sheep, but the effect of this has not previously been studied. The lumbar flexion-relaxation phenomenon is present in sheep shearing and the onset angle of this phenomenon can provide insight into lower back injury risk. The increase in the onset angle of lumbar flexion-relaxation over several work-rest periods for a simulated sheep shearing task is studied. The rate of increase in the onset angle of lumbar flexion-relaxation was higher when shorter breaks were taken for all participants at least unilaterally, indicating that longer rest breaks could reduce back injury risk. Due to the constraints of the sheep shearing occupation, this type of intervention is better suited to learner and novice shearers. Assistive robotic devices would be more suited to reduce injuries in expert shearers, and some insight is provided for the application of these within sheep shearing. Further study of this phenomenon in sheep shearing could provide additional insight to developing an assistive device that could reduce injury.

Acute muscle stretching and the ability to maintain posture in females with adolescent idiopathic scoliosis

BACKGROUND

Physiotherapy scoliosis specific exercises include exercises to attain and maintain proper posture, as well as flexibility movements such as stretching.

OBJECTIVE

To examine the effect of prior muscle stretching on the performance of posture exercise in females with adolescent idiopathic scoliosis (AIS).

METHODS

Eighteen females with AIS were randomly assigned to perform a posture maintenance task for three minutes preceded by either stretching protocol (group A) or no-stretching (group B). A second session was carried out after three days, where the same procedure was repeated in a reverse order between groups. During each session, three outcomes were tested: the ability to complete the task, the ability to maintain postural body alignment, and the perceived effort.

RESULTS

All participants completed the task in both sessions. Subjects' ability to preserve the required lower trunk alignment decreased following stretching compared to no-stretching. Lower-trunk angle changed toward flexion by 10∘ and 4.3∘ respectively, p= 0.032. There was no difference in perceived effort.

CONCLUSIONS

Prior muscle stretching has a negative effect on the ability to preserve body positional alignment during posture exercise. The present findings should be considered by practitioners when designing protocols for scoliosis-specific exercises. Stretching immediately prior to posture maintenance exercises should be avoided.

Use of antagonist muscle EMG in the assessment of neuromuscular health of the low back

BACKGROUND

Non-specific low back pain (LBP) has been one of the most frequently occurring musculoskeletal problems. Impairment in the mechanical stability of the lumbar spine has been known to lower the safety margin of the spine musculature and can result in the occurrence of pain symptoms of the low back area. Previously, changes in spinal stability have been identified by investigating recruitment patterns of low back and abdominal muscles in laboratory experiments with controlled postures and physical activities that were hard to conduct in daily life. The main objective of this study was to explore the possibility of developing a reliable spine stability assessment method using surface electromyography (EMG) of the low back and abdominal muscles in common physical activities.

METHODS

Twenty asymptomatic young participants conducted normal walking, plank, and isometric back extension activities prior to and immediately after maintaining a 10-min static upper body deep flexion on a flat bed. EMG data of the erector spinae, external oblique, and rectus abdominals were collected bilaterally, and their mean normalized amplitude values were compared between before and after the static deep flexion. Changes in the amplitude and co-contraction ratio values were evaluated to understand how muscle recruitment patterns have changed after the static deep flexion.

RESULTS

Mean normalized amplitude of antagonist muscles (erector spinae muscles while conducting plank; external oblique and rectus abdominal muscles while conducting isometric back extension) decreased significantly (P < 0.05) after the 10-min static deep flexion. Normalized amplitude of agonist muscles did not vary significantly after deep flexion.

CONCLUSIONS

Results of this study suggest the possibility of using surface EMG in the evaluation of spinal stability and low back health status in simple exercise postures that can be done in non-laboratory settings. Specifically, amplitude of antagonist muscles was found to be more sensitive than agonist muscles in identifying changes in the spinal stability associated with the 10-min static deep flexion. Further research with various loading conditions and physical activities need to be performed to improve the reliability and utility of the findings of the current study.