Negative Impacts of Prolonged Standing at Work on Musculoskeletal Symptoms and Physical Fatigue: The Fifth Korean Working Conditions Survey.

PURPOSE: We aimed to investigate variations in the risk of low back pain (LBP), lower extremity muscle pain, and whole body fatigue according to differences in prolonged standing work hours in relation to risk factor exposure and rest frequency. MATERIALS AND METHODS: From the fifth Korean Working Conditions Survey data collected in 2017, data for 32970 full-time workers who worked for more than 1 year at their present job were analyzed. We classified the workers according to exposure to fatigue or painful postures, carrying heavy objects, performance of repetitive movements that burden the musculoskeletal system, and how often they took a break. Relationships between time spent in a standing posture at work and risks of LBP, lower extremity muscle pain, and whole body fatigue were analyzed by multivariate logistic regression. RESULTS: Of the full-time workers in the survey, 48.7% worked in a standing position for more than half of their total working hours. A higher odds ratio (OR) value for lower extremity muscle pain was observed in female not exposed to carrying heavy objects [OR: 3.551, 95% confidence interval (CI): 3.038-4.150] and not exposed to performing repetitive movements (OR: 3.555, 95% CI: 2.761-4.557). CONCLUSION: Changes in work methodologies are needed to lower the number of hours spent in a prolonged standing posture at work, including being able to rest when workers want to do so, to reduce pain and fatigue.

Immediate effect of insoles on balance in older adults.

BACKGROUND: In recent years, fall prevention in older adults has received considerable attention in healthcare. Among many interventions, insoles are considered cost-effective and easily adopted tools to improve balance in older people. Numerous studies have verified the immediate effects of insoles on balance in older adults. However, there is still lack of consensus regarding the immediate benefits of using insoles on balance improvement. RESEARCH QUESTION: Given this, a meta-analysis was conducted to provide more conclusive evidence about the immediate effect of insoles on balance in older adults and answer the question: "Do insoles influence balance in older people?" METHODS: PubMed, NDSL, Medline, Google Scholar, and Web of Science were searched from March to August 2018. The key terms were "insole", "elderly", "gait", "balance", "shoe", "foot", and "postural". Finally, seven primary studies were selected for this meta-analysis. The balance related outcomes were coded to compute effect sizes and the overall effect size of the standardized mean differences was analyzed. Moderating variables included kinematic variables of balance, static and dynamic balance, and type of insole. RESULTS: The overall effect size of insoles was medium (d = 0.618), which suggests that insoles are beneficial for older adults for improving balance. More specifically, this study revealed that textured and vibration insoles were the most effective types of insoles. SIGNIFICANCE: This finding supports the idea that augmented tactile and mechanical sensory input from insoles can enhance the postural control mechanisms in older adults with age-related deterioration of sensory mechanisms. The use of insoles may lead to a reduction in the rate of falls which are related to decreased quality of life in older adults.

Comparative Effects of 4 Single-Leg Squat Exercises in Subjects With Gluteus Medius Weakness.

CONTEXT: Of the weight-bearing exercises, single-leg squats (SLSs) represent one of the most commonly used hip-strengthening exercises that require more gluteus medius (GMED) activity. To date, no studies have investigated how the 4 SLS exercises affect muscle imbalance of GMED, tensor fasciae latae (TFL), and adductor longus (AL), and kinematics of hip. OBJECTIVE: To investigate the hip muscle activities, onset time, and kinematics during 4 different SLS exercises (unilateral squat, unilateral wall-squat [UWS], lateral step-down, and front step-down) in subjects with GMED weakness. DESIGN: Repeated-measures experimental design. SETTING: Research laboratory. PARTICIPANTS: Twenty-two subjects (11 males and 11 females) participated in this study and were compared using 1-way repeated-measures analysis of variance. MAIN OUTCOME MEASURES: Surface electromyography was used to measure the muscle activities and onset time of the GMED, TFL, and AL, and 3-dimensional motion tracking system was used to measure the hip adduction and internal/external rotation angles during SLS exercises. One-way repeated-measures analysis of variance was used at a significance level of P < .05. RESULTS: The UWS produced higher GMED/TFL activity ratio and lower GMED/TFL onset time ratio than in the other 3 exercises (P < .05). No difference in GMED/AL activity ratio and GMED/AL onset time ratio was observed. The hip adduction angle was greater in UWS than in the other 3 exercises (P < .05). As for the hip internal/external rotation, lateral step-down exhibited higher hip internal rotation angle than front step-down (P < .05). CONCLUSION: The UWS may be recommended as an effective exercise for the subjects with GMED weakness, but they should take care to avoid excessive hip adduction during the exercise.

Effects of footrest heights on muscle fatigue, kinematics, and kinetics during prolonged standing work.

BACKGROUND: Among the tools for relieving lower back pain, footrests are commonly recommended. Few studies have investigated the effects of footrest and the proper application of footrest height. OBJECTIVE: The purpose of this study was to compare the effects of the normalized footrest height on muscle fatigue, kinematics, kinetics, and pain intensity. METHODS: In total, 13 males who had a history of non-specific lower back pain during prolonged standing were recruited. The experimental conditions were 2-hour prolonged standing with no footrest and with footrests of 5%, 10%, and 15% of body height. Muscle fatigue was investigated through measurements of the median frequency ratio and the muscle activity ratio (post/pre) in lumbar erector spinae. The lumbo-pelvic angles, and the external moment in the lumbar region were investigated. A visual analog scale was used to investigate the intensity of the pain. RESULTS: The footrests at 10% and 15% of the body height caused a lower change in the median frequency ratio and the muscle activity ratio than the other conditions. The footrest at 10% of the body height placed the lowest external moment on the lumbar region among all the conditions. The pain intensity was significantly lower in with footrest conditions than with no footrest condition. CONCLUSIONS: The results suggests that a footrest height of 10% of the body height can be recommended as a normalized height for prolonged standing work in subjects with a history of non-specific lower back pain during prolonged standing.

Difference in static and dynamic stability between flexible flatfeet and neutral feet.

Different postural stability may be a contributor to secondary injuries in individuals with flexible flatfeet (FF) compared to those with neutral feet (NF). However, the differences between static and dynamic stability of FF and NF have not been examined. This study compared the static and dynamic stability of subjects with FF and NF and investigated the relationship between static and dynamic stability. Twenty-eight subjects (14 each in the FF and NF groups) performed three tasks (single leg standing with eyes open, with eyes closed, and the Y balance test). We quantified the center of pressure (COP) speed and Y balance test score (Y score) within the tasks. COP speed was significantly greater in the FF group than in the NF group under both conditions (eyes open and closed) and directions (anteroposterior and mediolateral). Y scores did not differ significantly between the two groups. No significant relationship was observed between the COP speed and Y score in either group. These results show that individuals with FF have different static stabilities, but not dynamic stabilities, compared with those with NF. This might indicate the absence of a relationship between static and dynamic stabilities.

Effect of Selective Muscle Training Using Visual EMG Biofeedback on Infraspinatus and Posterior Deltoid.

We investigated the effects of visual electromyography (EMG) biofeedback during side-lying shoulder external rotation exercise on the EMG amplitude for the posterior deltoid, infraspinatus, and infraspinatus/posterior deltoid EMG activity ratio. Thirty-one asymptomatic subjects were included. Subjects performed side-lying shoulder external rotation exercise with and without visual EMG biofeedback. Surface EMG was used to collect data from the posterior deltoid and infraspinatus muscles. The visual EMG biofeedback applied the pre-established threshold to prevent excessive posterior deltoid muscle contraction. A paired t-test was used to determine the significance of the measurements between without vs. with visual EMG biofeedback. Posterior deltoid activity significantly decreased while infraspinatus activity and the infraspinatus/posterior activity ratio significantly increased during side-lying shoulder external rotation exercise with visual EMG biofeedback. This suggests that using visual EMG biofeedback during shoulder external rotation exercise is a clinically effective training method for reducing posterior deltoid activity and increasing infraspinatus activity.