Effects of different lifting and lowering heights on upper arm, shoulder and back muscle activity during a manual material handling task

The Application of Surface Electromyography Technology in Evaluating Paraspinal Muscle Function

Surface electromyography (sEMG) has emerged as a valuable tool for assessing muscle activity in various clinical and research settings. This review focuses on the application of sEMG specifically in the context of paraspinal muscles. The paraspinal muscles play a critical role in providing stability and facilitating movement of the spine. Dysfunctions or alterations in paraspinal muscle activity can lead to various musculoskeletal disorders and spinal pathologies. Therefore, understanding and quantifying paraspinal muscle activity is crucial for accurate diagnosis, treatment planning, and monitoring therapeutic interventions. This review discusses the clinical applications of sEMG in paraspinal muscles, including the assessment of low back pain, spinal disorders, and rehabilitation interventions. It explores how sEMG can aid in diagnosing the potential causes of low back pain and monitoring the effectiveness of physical therapy, spinal manipulative therapy, and exercise protocols. It also discusses emerging technologies and advancements in sEMG techniques that aim to enhance the accuracy and reliability of paraspinal muscle assessment. In summary, the application of sEMG in paraspinal muscles provides valuable insights into muscle function, dysfunction, and therapeutic interventions. By examining the literature on sEMG in paraspinal muscles, this review offers a comprehensive understanding of the current state of research, identifies knowledge gaps, and suggests future directions for optimizing the use of sEMG in assessing paraspinal muscle activity.

Workers’ subjective discomfort, muscle fatigue, and kinematics during a manual packaging task

BACKGROUND: Due to the prevalence and increased demand for manual packaging tasks, the concern for worker health and safety has grown. OBJECTIVE: This study aims to assess the effects of gender and work postures on subjective discomfort, muscle fatigue, and kinematics during a manual packaging task. METHODS: Twenty participants, including 10 males and 10 females, were recruited to perform a 60-minute manual packaging task in sitting and standing postures. RESULTS: Discomfort was evidenced by increased the rating of perceived exertion (RPE) values (sit: from 6 to 14.55; stand: from 6 to 17.15) and muscle fatigue was supported by decreased median power frequency (MPF) values for right brachioradialis (RB) (sit: –23.68% ; stand: –16.20%), right upper trapezius (RUT) (sit: –20.14% ; stand: 11.79%), and right erector spinae (RES) (sit: 8.64% ; stand: 11.21%) muscles. Women were more likely to bend forward in a relaxed upper body position, especially while sitting, which may increase the risk of low back pain and women also reported greater discomfort than men, but not in the hands and back. Compared with sitting, the back showed greater muscle fatigue in standing, while muscle fatigue for the shoulders and hands was the opposite. CONCLUSION: These findings suggest that work posture should be considered to prevent fatigue in manual packaging tasks. Given the impact of gender on muscle fatigue, work performed by women and men should both be considered. The results can help to develop action strategies and work posture design to prevent musculoskeletal disorders in the manual packaging industry.

Effects of stretching on muscle activation in gas cylinder handling

BACKGROUND

Previously, a stretching regimen was designed for manual material handling (MMH) of gas cylinders as a potential ergonomic solution for reducing occupational injury. No studies have made use of objective process measures, such as muscle activation levels, for evaluation of effects of stretching programs.

OBJECTIVE

Examine acute effects of stretching on muscle activation levels and driver perceived level of exertion in gas cylinder handling during simulated delivery operations.

METHODS

A within-subject experiment was conducted with eight male participants being subjected randomly to two conditions over a two-day period: stretching before delivery trials and no stretching. Surface electromyography and the Borg CR-10 scale for perceived exertion were used.

RESULTS

Generally, results were variable among muscle responses. The extensor muscle bundle in the forearm was found to show a significant decrease (p = 0.0464) in activation level because of stretching. The anterior deltoid and trapezius significantly increased (p < .0001) the EMG activation level with stretching. Also counter to expectations, participants rated perceived exertion significantly higher (p = 0.0423) for trials preceded by stretching.

CONCLUSIONS

This research indicates a muscle stretching regimen in advance of MMH activities has mixed effects on activation levels across muscles. It is possible that effects are attributable to body posture positions, or manner of muscle use, during actual work activities. Findings indicate that stretching prior to work activity does have an impact on specific muscle activation.

Development of a device to reduce the risk of injury in handling unstable loads

BACKGROUND

Manual material handling (MMH) task is the most common cause of work-related musculoskeletal disorders (MSDs). Operators carrying unstable loads were recently shown to be at greater risk of back injury compared to workers carrying stable loads.

OBJECTIVE

This study focused on developing a device to minimize trunk muscle activity and cardiovascular demand while handling a 19-liter bottle.

METHOD

After evaluating several designs, one was selected to be developed, manufactured and tested through an experimental study. Healthy participants (n = 42) manually carried a 19-liter bottle. The carrying technique (i.e., carrying a lateral load while holding the load using the dominant hand, pulling the load using the developed device, carrying the load on the back using the developing device) was the independent variable. The muscular activities (e.g., neck extensor, upper trapezius, pectoralis major, deltoid medial, rectus abdominis, and erector spinae muscles of the dominant side), cardiac costs, plantar pressures, walking speeds, and subjective measures were the dependent variables.

RESULTS

Results show that carrying the developed device like a backpack significantly reduced trunk muscle activity, cardiovascular demand, and plantar pressure compared to the usual practice. The present results suggest that carrying a 19-liter water bottle using the developed device is likely to contribute to lower MSDs.

CONCLUSION

Implementation of the develop device recommended to lessen the risk of injury when handling unstable loads such as liquids.

Neck posture during lifting and its effect on trunk muscle activation and lumbar spine posture

Neck and head posture have been found to have a significant influence on the posture of the lower spine region during lifting and both an extended/upward gaze and a flexed/downward gaze have been hypothesized to lead to increased pain and/or overuse of the neck musculature. As a result, strength training recommendations have turned to the use of a retracted neck posture as being the safer posture to assume during lifting. This study examined trunk and neck muscle activity and lumbar spine posture in seven participants while performing moderate load lifts using a retracted neck posture (chin drawn in posteriorly; recently gaining popularity among coaches, trainers, and physical therapists to reduce neck pain during lifting, and freestyle neck posture (no instructions given). The retracted neck resulted in less lumbar spine flexion and increased lumbar erector spinae, external oblique, and sternocleidomastoid activity. The retracted posture also resulted in decreased activity in the thoracic erector spinae and dorsal neck musculature. The increased trunk and sternocleidomastoid activity and decreased spine flexion observed in the seven participants of this study when lifting with a retracted neck may have the potential to help lower the risk of spine pain/injury.