Relationships between lower limb and trunk discomfort and vascular, muscular and kinetic outcomes during stationary standing work

Changes in Baropodometric Evaluation and Discomfort during the Workday in Assembly-Line Workers

Prolonged standing at work is associated with health risks. The appearance of lower-limb and lower-back discomfort is one of the most prevalent factors in prolonged standing workers. The aim of this research was to evaluate the effect of an eight-hour workday on foot pressure and musculoskeletal discomfort in standing workers. Thirty-six assembly-line workers (six women) were recruited to participate in a cross-sectional study to assess foot pressure and surface, foot, knee, and lower-back discomfort before and after a real workday. Baropodometry outcomes (surface and pressure) were evaluated by the pressure platform SensorMedica and musculoskeletal discomfort was evaluated by Cornell's Musculoskeletal Discomfort Questionaire. Total foot surface (p = 0.01) and foot discomfort (p = 0.03) increased significantly at the end of the workday. Prolonged standing during 8 h workday increased the foot discomfort and total foot surface in assembly-line workers. No foot pressure variable (forefoot, rearfoot, or total) was significantly modified after the workday in assembly-line workers.

Common law enforcement load carriage systems have limited acute effects on postural stability and muscle activity

Law enforcement officers are inherently at a high risk of injury and the loads they must carry during their occupational duties further increase their injury risk. It is unknown how different methods of carrying a law enforcement officer's load influence factors related to injury risk. This study assessed the effects of common law enforcement load carriage systems on muscular activity and postural stability while standing. Twenty-four participants performed single and dual-task (i.e. concurrent performance of cognitive tasks) standing while wearing a duty belt, tactical vest, and no load. The postural stability and muscle activity were measured and effects of condition and task examined. Dual task standing decreased postural stability and increased muscular activity. The belt and vest (7.2 kg each) increased muscle activity compared to control for the right abdominals, low back, right thigh. The duty belt resulted in less muscle activity in the right abdominals but more muscle activity in the left multifidus compared to the control. The findings indicate that common law enforcement load carriage systems increase muscular activity but do not affect postural stability. However, the lack of differences between the duty belt and tactical vest did not provide clear support for one load carriage system versus the other.

Designing and validation of Yoga module for workers with prolonged standing

BACKGROUND

Prolonged standing is a part of several professions, which can have physical and psychosocial implications. Yoga as a mind-body therapy may be useful to prevent and manage such health issues. However, there is a lack of a standardized yoga module addressing the health issues of workers with prolonged standing.

OBJECTIVES

Thus, the present study was undertaken to design and validate a specific yoga module for the target population.

METHODS

A yoga module was prepared by reviewing yoga texts for the specific needs of the target population. This was validated for content validity for the experts on a Likert scale. 71 yoga experts validated the module. The content validity ratio (CVR) above 0.70 was considered to be valid.

RESULTS

The validated yoga module consists of joint loosening and strengthening exercises, asana, pranayama and relaxation techniques. The average CVR for the module was found to be 0.80.

CONCLUSION

The designed yoga module is found to be valid by the experts. The module needs to be assessed for feasibility and efficacy in the target population.

Comparison of Physiological Effects Induced by Two Compression Stockings and Regular Socks During Prolonged Standing Work

OBJECTIVE

The goal of this study was to evaluate and compare lower-leg muscle fatigue, edema, and discomfort induced by the prolonged standing of security guards wearing regular socks and those wearing 15-20 or 20-30 mmHg compression stockings as intervention.

BACKGROUND

Compression stockings are sometimes used by individuals standing all day at work. However, quantitative evidence showing their potential benefits for lower-leg health issues in healthy individuals during real working conditions is lacking.

METHOD

Forty male security employees participated in the study. All were randomly assigned to the control or one of the two intervention groups (I15-20 or I20-30). Lower-leg muscle twitch force, volume, and discomfort ratings were measured before and after their regular 12-hr standing work shift.

RESULTS

Significant evidence of lower-leg long-lasting muscle fatigue, edema, and discomfort was observed after standing work for guards wearing regular socks. However, no significant changes were found for guards wearing either compression stockings.

CONCLUSION

In healthy individuals, compression stockings seem to attenuate efficiently the tested outcomes in the lower leg resulting from prolonged standing.

APPLICATION

Occupational activities requiring prolonged standing may benefit from 15-20 or 20-30 mmHg compression stockings. As similar benefits were observed for both levels of compression, the lower level may be sufficient.

Comparison of intermittent pneumatic compression device and compression stockings for workers with leg edema and pain after prolonged standing: a prospective crossover clinical trial

BACKGROUND

During prolonged standing, insufficient calf muscle pumping accompanies venous stasis and hypertension in the lower legs, resulting in valve dysfunction, venous wall problems, and sub-sequent inflammation. Compression therapy, which includes medical compression stockings (MCS) and mechanical intermittent pneumatic compression (IPC), is one of the most effective therapeutic interventions for treating chronic venous diseases. This study aimed to compare the therapeutic effect among resting, IPC and MCS alone, and IPC with MCS in long-standing workers (> 8 h daily).

METHODS

This crossover trial was conducted with 39 participants with complaints of leg edema and pain whose work involved standing for more than 8 h daily. Four treatment protocols were established for each visit as follows: protocol A (not wear MCS during work and rest without IPC after work), protocol B (wear MCS during work and rest without IPC after work), protocol C (not wear MCS during work and treat with IPC after work), and protocol D (wear MCS during work and treat with IPC after work). The primary outcome was the visual analogue scale (VAS) score for leg pain. The secondary outcomes were leg volume (mL), circumference (cm), extracellular fluid/total body fluid (ECF/TBF), and extracellular water/total body water (ECW/TBW) through bioelectrical impedance analysis. Outcomes were assessed before work (T0), after work (T1), and 60 min after intervention (T2).

RESULTS

All four protocols had significantly increased leg pain after work (T0-1) but improved 60 min after intervention (T1-2), particularly protocol C (decreased VAS by 1.9). When leg swelling was compared at T0 and T1, protocols A and C showed significant increases in leg volume and circumference, indicating significant work-induced edema, whereas protocols B and D showed no change or even a decrease. After interventions, leg volume and circumference significantly decreased in protocols A and C, although protocols B and C did not show significant improvement. The ECF/TBF and ECW/TBW of all protocols decreased after interventions.

CONCLUSIONS

Leg pain and edema after prolonged standing (T1-T2) in adults were safely and effectively improved by both IPC alone and IPC with MCS. Although the use of MCS during the workday did not show improvement in leg pain immediately after work (T0-T1), both MCS with resting and MCS with IPC decreased leg pain at T1-T2 and prevented leg edema at T0-T1.

TRIAL REGISTRATION

This trial protocol was registered at the Clinical Research Information Service (KCT0005383, the date of first registration: 08/09/2020).

Nonlinear analysis of postural changes related to the movement interventions during prolonged standing task

This study assessed the effects of movement-based interventions on the complexity of postural changes during prolonged standing. Twenty participants, equally distributed in gender and standing work experience (SWE), completed three simulated prolonged standing sessions: without movement (control), leg exercise and footrest. The amount and complexity of variability in the centre of pressure (COP) and lumbar curvature angle were quantified using linear and nonlinear tools. Lower leg swelling and back/leg discomfort were also monitored. Participants in the SWE group showed significantly greater postural complexity during the standing. Regular leg exercise resulted in significantly higher postural complexity and lower leg discomfort and swelling. The footrest led to significant changes in amount of COP variability. Both interventions significantly reduced back discomfort. Overall, the nonlinear analysis of postural changes provided different findings compared to linear ones, considering the standing time, interventions and standing job experience. Nonlinear results were consistent with leg discomfort and swelling. Practitioner summary: The effect of movement-based interventions on dynamics of postural alterations over prolonged standing were characterised using nonlinear techniques. The effect of standing work experience was also considered. Previous experience of standing jobs and leg movements increase the complexity of postural behaviour over standing period.

Use of an inflatable mat to reduce body discomfort development when performing computer work at a standing desk

This study aimed to determine the effects of inflatable mat design on body discomfort, task performance, and musculoskeletal exposures during standing computer work. Twenty-seven healthy adults completed three 2-hour standing trials on different mediums (concrete floor, foam mat, and inflatable mat) on different days in an experimental laboratory. Both mats were associated with reduced discomfort in all lower-body regions and increased typing performance compared to the concrete floor. Perceived discomfort in lower extremities (except thighs) was further alleviated while standing on the inflatable mat than on the foam mat. Use of the inflatable mat led to increased lower-body muscle activity, a flexed lower back, and a wide range of sagittal knee movements. As standing time increased, body discomfort increased, typing accuracy decreased, and there were increased variations in muscle activity and postural movements in the lower body. The inflatable mat shows potential to improve the ergonomic experience during prolonged standing. Practitioner summary: Incorporating standing postures in office-based workplaces can reduce sitting time and may mitigate the health hazards associated with sedentary behaviour. With adequate weight-shifting movements, using an inflatable mat for standing could be an effective way to lessen discomfort and accumulated musculoskeletal strain due to constrained standing, without jeopardising task productivity. Abbreviations: APDF: amplitude probability distribution function. AVR: average rectified value. CI: confidence interval. CMRR: common mode rejection ratio. COP: center of pressure. CV: coefficient of variation. EA: electrical activity. EMG: electromyography. FL: fibularis longus. GM: gluteus medius. LBP: lower back pain. LES: lumbar erector spinae. MVC: maximum voluntary contraction. PD: pain developer. rANOVA: repeated-measures analysis of variance. SOL: soleus. VAS: visual analog scale. WPM: words per minute.

Does active sitting provide more physiological changes than traditional sitting and standing workstations?

This cross-sectional study examined the physiological effects of two active chairs (AC1: had the feature to pedal and slide forward; AC2: was a multiaxial chair) compared to a traditional office chair and standing workstation. Twenty-four healthy participants computed at each of the workstations for 60 min. The active protocol was to alternate between a pedalling/side-to-side motion and sliding forward/front-to-back motion to the sound of a metronome operating at 40 bpm. The participants' physiological effects were recorded using near-infrared spectroscopy (NIRS); electrodermal activity (EDA) and a heart rate (HR) monitor for each collection period. Statistical analysis was conducted using a repeated measures analysis of variance for within-task and between-workstation comparisons. A Tukey's post hoc analysis was calculated for significant findings. Both active chairs significantly increased oxygenated blood in the gastrocnemius and participants' heart rate and EDA (stress) levels were affected slightly by task and time. However, participants felt more "productive" sitting in the control chair than in either of the active chairs.

Thirty Minutes Identified as the Threshold for Development of Pain in Low Back and Feet Regions, and Predictors of Intensity of Pain during 1-h Laboratory-Based Standing in Office Workers

This study with 40 office workers investigated (a) the effect of time spent standing on low- back and lower limb pain during a 1-h laboratory-based task; (b) the standing time after which a significant increase in pain is likely; and (c) the individual, physical and psychosocial factors that predict pain. The primary outcome was bodily location of pain and pain intensity on a 100-mm Visual Analogue Scale recorded at baseline and every 15 min. Physical measures included trunk and hip motor control and endurance. Self-report history of pain, physical activity, psychosocial job characteristics, pain catastrophizing and general health status were collected. Univariate analysis and regression models were included. The prevalence of low-back pain increased from 15% to 40% after 30 min while feet pain increased to 25% from 0 at baseline. The intensity of low-back and lower limb pain also increased over time. A thirty-minute interval was identified as the threshold for the development and increase in low-back and feet pain. Modifiable factors were associated with low-back pain intensity-lower hip abductor muscle endurance and poorer physical health, and with feet symptoms-greater body mass index and less core stability.

Different sit:stand time ratios within a 30-minute cycle change perceptions related to musculoskeletal disorders

Regular standing interruptions to sedentary work are recommended, but their dosage is understudied. To measure perception variations associated with different sit:stand ratios, 16 people used six ratios (30:0, 27:3, 24:6, 21:9, 18:12 and 15:15) within 30-min cycles in their normal office environment. At start and end of each workday, study participants recorded their perception of 11 factors on a 10-point scale. Musculoskeletal discomfort in 10 body regions was measured before and after exposure to sit-stand ratios. Overall preferred ratios were recorded. Sit:stand ratio affected all perceived factors, with impact varying. Standing at least 6 min improved results most overall; however, individual perceived factors were least impacted by any of 30:0, 27:3, 24:6 or 21:9. Preferred sit:stand ratios were 15:15, 18:12 and 21:9. Typically, least liked ratios involved briefest standing (30:0, 27:3, 24:6) although two participants least liked 15:15. Understanding these variations contributes to appropriate standing dosage recommendations.

Determining the interactions between postural variability structure and discomfort development using nonlinear analysis techniques during prolonged standing work

PURPOSE

Nonlinear analysis techniques provide a powerful approach to explore dynamics of posture-related time-varying signals. The aim of this study was to investigate the fundamental interactions between postural variability structure and discomfort development during prolonged standing.

METHODS

Twenty participants, with equal distribution for gender and standing work experience (SWE), completed a simulated long-term standing test. Low back and legs discomfort, center of pressure, lumbar curvature, and EMG activity of trunk and leg muscles were monitored. Nonlinear measures including largest lyapunov exponent, multi-scale entropy, and detrended fluctuation analysis were applied to characterize the variability structure (i.e., complexity) in each signal. The size (i.e., amount) of variability was also computed using traditional linear metrics.

RESULTS

With progress of low back and legs discomfort over standing periods, significant lower levels were perceived by the participants having SWE. The amount of variability in all signals (except external oblique EMG activity) were significantly increased with the time progress for all participants. The structure of variability in most signals demonstrated a lower complexity (more regularity) with fractal properties that deviated from 1/f noise. The SWE group showed a higher complexity levels.

CONCLUSIONS

Overall, the findings verified variations in structure and amount of the postural variability. However, nonlinear analysis identified postural strategies according to the perceived discomfort in a different way. These results provide supports for future application of nonlinear tools in evaluating standing tasks and related ergonomics interventions as it allows further insight into how discomfort development impact the structure of postural changes.

Associations of objectively measured total duration and maximum bout length of standing at work with lower-extremity pain intensity: a 2-year follow-up of construction and healthcare workers

Background

Musculoskeletal disorders are among the major reasons for years lived with disability. Approximately one third of the European working population report lower-extremity discomfort and many attribute these discomforts to work-related factors. Employees in the healthcare and construction sectors reports high levels of lower-extremity pain and commonly relate the pain to their profession. These workers spend a large part of their workday standing. Periods of prolonged standing is suggested to increase lower-extremity symptoms, but this cannot be concluded on, since limited evidence is available from longitudinal studies using objective measures. This study aimed to determine possible associations between objectively measured total duration and maximum bout length of static- and dynamic standing at work and lower-extremity pain intensity (LEPi) among Norwegian construction- and healthcare workers.

Methods

One-hundred and twenty-three construction and healthcare workers wore two accelerometers for up to four consecutive days, to establish standing behavior at baseline. The participants reported LEPi (Likert scale 0–9) for the preceding 4 weeks at baseline and after 6, 12, 18, and 24 months. We investigated associations between standing at work and average and change in LEPi using linear mixed models with significance level p ≤ 0.05.

Results

Total duration of static- and dynamic standing showed weak associations with average LEPi, for the total sample and for construction workers. Maximum bout of static- and dynamic standing was associated with average LEPi in construction workers, but not in healthcare workers. Furthermore, we found no associations between standing and change in LEPi over the 2-year follow-up in any of our analyses.

Conclusions

This study indicate that objectively measured standing is associated with average LEPi over 2-years follow-up in construction workers, and that maximal bout of standing have a stronger association to LEPi than total duration. For every 10 min added to the maximal length of continuous standing during an average workday, we found approximately one unit increase in pain on a 0–9 scale. The lack of significant findings in analyses on healthcare workers suggest that the association between standing and LEPi depend on work-tasks, gender and/or other sector-specific factors.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12891-020-03868-0.

Efectos del trabajo de pie en trabajadores del sector sanitario

Introducción: En el sector sanitario es común la ejecución de actividades de pie; sin embargo, es un tema poco atendido, a pesar de los efectos negativos que se pueden generar en la salud de los trabajadores. Objetivo: Analizar la variación de dolor musculoesqueléticos en las extremidades inferiores y espalda baja, y la variación de volumen en las piernas presentados en trabajadores sanitarios que realizan sus actividades de pie durante una jornada laboral. Materiales y métodos: Estudio transversal donde se registró la percepción de dolor musculoesquelético de los segmentos corporales: espalda baja y el lado derecho e izquierdo de: muslo-cadera, rodilla, pierna y tobillo-pie y se midió la circunferencia para calcular su volumen de las piernas con la cinta métrica Gulick II a 21 trabajadores del sector sanitario. Los registros y mediciones se realizaron durante la primera y la última hora de una jornada laboral de 8 horas. Resultados: En todos los segmentos corporales la percepción de dolor musculoesquelético y el volumen en ambas piernas aumentó al final de la jornada laboral respecto al inicio. Los segmentos corporales muslo-cadera izquierda, tobillo-pie derecho y el volumen en ambas piernas aumentaron significativamente. Discusión: Los resultados obtenidos son similares a estudios con diseños experimentales, con la diferencia que nuestro estudio se desarrolló en condiciones reales sin control de variables. Conclusiones: Este estudio muestra cómo actividades del sector sanitario ejecutadas durante tiempos prolongados de pie pueden ocasionar en los trabajadores dolor musculoesqueléticos en las extremidades inferiores y la espalda baja, así como un aumento en el volumen de las piernas.

Brain activity during a working memory task in different postures: an EEG study

While working is more comfortable in a supine position and healthier in a standing, most people work in a sitting. However, it is unclear whether there are differences in brain activity efficiency in different postures. Here, we, therefore, compared changes in brain activity across three different postures to determine the optimal posture for performing working memory tasks. Their effect on brain activity was examined using EEG signals together with the information of accuracy and reaction times during 2-back task in 24 subjects. Substantial differences in brain waves were observed at sitting and standing positions compared to the supine, especially in delta waves and frontal lobe, where is known to improve the modulation of brain activity efficiently. Brain efficiency was higher during standing and sitting than in a supine. These findings show that postural changes may affect the efficiency of brain activity during working memory tasks. Practitioner summary: Differences in brain efficiency between different postures during working memory tasks have not been explored. This study suggests that efficiency in several brain areas is higher during sitting and standing than in a supine position. This finding has important implications regarding workplace environments. Furthermore, this result would be useful to improve accomplishment and reduce negative effects of work posture. Abbreviations: EEG: electroencephalogram; PSQI: Pittsburgh sleep quality index; KSS: Karolinska sleepiness scale; FFT: fast fourier transform; ROI: region of interest; ANS: autonomic nervous system; Fp: prefrontal; AF: anterior frontal; frontal; Fz: midline frontal; temporal; central; Cz: midline central; P: parietal; Pz: midline parietal; O: occipital; Oz: midline occipital.

Robotic Surgery Is Less Physically Demanding Than Laparoscopic Surgery: Paired Cross Sectional Study

OBJECTIVE

To study musculoskeletal workload in experienced surgeons during laparoscopic surgery (LS) compared with robotic assisted laparoscopy (RALS).

BACKGROUND

70-90% of surgeons who regularly perform LS report musculoskeletal symptoms, mainly in neck and shoulders. Data regarding the potential ergonomic benefits of RALS in a clinical setting is very limited.

METHODS

Twelve surgeons with advanced experience in both LS and RALS each performed 2 hysterectomies on the same day. LS was performed standing, RALS sitting, the latter allowing forearm and head support. Bipolar surface electromyogram (EMG) was recorded from several muscles and was expressed relative to EMG during maximum contractions (%EMGmax). Gaps per minute plus static (p0.1), mean (p0.5), and peak (p0.9) muscle activation were calculated. Perceived exertion was rated before and just after each surgery.

RESULTS

Neck muscle activity (p0.1 4.7 vs. 3.0%EMGmax, p0.5 7.4 vs. 5.3%EMGmax, p0.9 11.6 vs. 8.2%EMGmax, all P < 0.05) and static shoulder muscle activity (p0.1 5.7 vs. 2.8%EMGmax, P < 0.05) were higher for LS than for RALS. Both a higher level of gaps during RALS and a lower rating of perceived exertion, also for the legs, after RALS supported these observations. However, low back muscle activity was higher for RALS.

CONCLUSIONS

RALS is significantly less physically demanding than LS, and also feels less strenuous for the surgeons. However, for both types of surgeries, there still is room for improvement of working conditions. To further optimize these, we suggest a scheme to regularly observe and advise the surgeons.

Physiological and neuromotor changes induced by two different stand-walk-sit work rotations

The potential of rotating postures to alleviate the effects of prolonged standing and sitting postures has been advocated to attenuate the accumulation of muscle fatigue, considered a precursor to musculoskeletal disorders. We aimed to evaluate the effects of two posture rotations, both including standing, walking, sitting, on physiological and neuromotor measures. Twenty-two participants followed two posture rotations, with different rest-break distributions, for 5.25 h. Lower-leg muscle twitch force, volume, force control and discomfort perception were evaluated during and after work exposure on two non-consecutive days. Significant changes in all measures indicate a detrimental effect in lower-leg long-lasting muscle fatigue, oedema, performance and discomfort after 5 h for both exposures. However, for both exposures recovery was significant 1 h and 15 h post-workday. Differences between the two rotation schedules were not significant. Hence, stand-walk-sit posture rotation promotes recovery of the tested measures and is likely to better prevent muscle fatigue accumulation. Practitioner summary: Lower-leg muscle twitch force, volume, force control, and discomfort were quantified during and after 5 h of stand-walk-sit work rotations with two different rest-break distributions. Measures revealed similar significant effects of work exposures regardless of rotation; which did not persist post-work. This beneficial recovery contrasts with the standing only situations. Abbreviations: MSDs: musculoskeletal disorders; MTF: muscle twitch force; RMSE: root mean square error; MVC: maximum voluntary contraction; M: mean; SE: standard error.

Spinal shrinkage, sagittal alignment and back discomfort changes in manufacturing company workers during a working day

Prolonged standing and lifting heavy loads are risk factors for the appearance of low back pain in work. The aim of this study was to observe changes in the height, spinal sagittal alignment, and the lumbar and dorsal discomfort perception in assembly line workers. Cross-sectional study, 40 assembly line workers (6 females). Height, sitting height, grades of thoracic kyphosis and lumbar lordosis and perceived spine discomfort, before and after the working day, were determined. Thoracic and lumbar sagittal alignment was compared between discomfort developers and no developers. There was a significant decrease in the height and sitting height of the workers at the end of the day. Thoracic and lumbar curvature increased significantly, as did the perceived lumbar discomfort. Workers on the assembly line, in a prolonged standing work, suffer an increase in lumbar discomfort, and changes in height and thoracic and lumbar curvatures. Practitioner summary: Spinal shrinkage, sagittal alignment and back discomfort (upper and lower back), were analysed in assembly line workers in prolonged standing during a workday. Assembly line workers suffer a decrease in height, an increase in their thoracic and lumbar curvature, and in lumbar discomfort throughout their workday.

Musculoskeletal and Cognitive Effects of a Movement Intervention During Prolonged Standing for Office Work

OBJECTIVE

To investigate whether use of a movement intervention when undertaking prolonged standing affected discomfort and cognitive function.

BACKGROUND

Alternate work positions to break up prolonged sitting for office workers are being trialed, such as standing. Prolonged standing has potential negative health implications, including low back and lower limb discomfort, and may influence cognitive function. Introducing movement during standing may provide a healthy and productive alternative work posture.

METHOD

Twenty adult participants undertook a laboratory study of 2 hr of standing and standing with movement (using a footrest) while performing computer work. Changes in discomfort and cognitive function, with muscle fatigue, low back angle, pelvis movement, lower limb swelling, and mental state, were investigated.

RESULTS

Discomfort increased significantly over time across all body regions. Ankle/foot differed between conditions (incident rate ratio [95% confidence interval]: 1.89 [1.10-3.23]), with higher discomfort during standing with movement. Creative problem-solving errors increased during standing with movement and decreased during standing (Time × Condition: β = 0.64 [0.10-1.18]), with no other cognitive function measure differences. Mental state deteriorated over time for both conditions, greater during standing with movement (Time × Condition: β = 2.44 [0.23-4.66]). No significant interaction effects were found for the other outcome variables.

CONCLUSION

Standing with movement provided no advantage in discomfort or cognitive function. There were some negative effects for ankle/foot discomfort and creative problem solving. An alternate footrest design and protocol for use may yield more favorable results.

APPLICATION

Based on the results from this study, footrest use to raise alternative foot for forced 5-min intervals would not be recommended to assist with managing discomfort while prolonged standing in workplaces.

Muscular and Vascular Issues Induced by Prolonged Standing With Different Work-Rest Cycles With Active or Passive Breaks

OBJECTIVE

The aim of this study was to evaluate the long-lasting motor, behavioral, physiological, and perceptual effects of prolonged standing work in three work-rest cycle conditions including passive or active rest breaks.

BACKGROUND

Muscle fatigue has been evidenced after prolonged standing work through physiological and neuromotor measures. It has been postulated that muscle fatigue induced by prolonged work could be attenuated by appropriate scheduling of work and rest periods. However, investigations in this domain remain limited.

METHOD

Thirty participants simulated standing work for 5 hr with work-rest cycles of short, medium, or long standing periods including passive or active breaks. Lower-leg muscle twitch force (MTF), muscle oxygenation, lower-leg volume, postural stability, force control, and discomfort perception were quantified on 2 days.

RESULTS

Prolonged standing induced significant changes in all measures immediately after 5 hr of work, indicating a detrimental effect in long-lasting muscle fatigue, performance, discomfort, and vascular aspects. Differences in the measures were not significant between work cycles and/or break type.

CONCLUSION

Similar physiological and motor alterations were induced by prolonged standing. The absence of difference in the effects induced by the tested work-rest cycles suggests that simply altering the work-rest cycle may not be sufficient to counteract the effects of mainly static standing work. Finally, standing for 3 hr or more shows clear detrimental effects.

APPLICATION

Prolonged standing is likely to contribute to musculoskeletal and vascular symptoms. A limitation to less than 3 hr of mostly static standing in occupational activities could avoid alterations leading to these symptoms.

The Short Term Musculoskeletal and Cognitive Effects of Prolonged Sitting During Office Computer Work

Office workers are exposed to high levels of sedentary time. In addition to cardio-vascular and metabolic health risks, this sedentary time may have musculoskeletal and/or cognitive impacts on office workers. Participants (n = 20) undertook two hours of laboratory-based sitting computer work to investigate changes in discomfort and cognitive function (sustained attention and problem solving), along with muscle fatigue, movement and mental state. Over time, discomfort increased in all body areas (total body IRR [95% confidence interval]: 1.43 [1.33–1.53]) reaching clinically meaningful levels in the low back and hip/thigh/buttock areas. Creative problem solving errors increased (β = 0.25 [0.03–1.47]) while sustained attention did not change. There was no change in erector spinae, trapezius, rectus femoris, biceps femoris and external oblique median frequency or amplitude; low back angle changed towards less lordosis, pelvis movement increased, and mental state deteriorated. There were no substantial correlations between discomfort and cognitive function. The observed changes suggest prolonged sitting may have consequences for musculoskeletal discomfort and cognitive function and breaks to interrupt prolonged sitting are recommended.

A detailed description of the short-term musculoskeletal and cognitive effects of prolonged standing for office computer work

Due to concerns about excessive sedentary exposure for office workers, alternate work positions such as standing are being trialled. However, prolonged standing may have health and productivity impacts, which this study assessed. Twenty adult participants undertook two hours of laboratory-based standing computer work to investigate changes in discomfort and cognitive function, along with muscle fatigue, movement, lower limb swelling and mental state. Over time, discomfort increased in all body areas (total body IRR [95% confidence interval]: 1.47[1.36-1.59]). Sustained attention reaction time (β = 18.25[8.00-28.51]) deteriorated, while creative problem solving improved (β = 0.89[0.29-1.49]). There was no change in erector spinae, rectus femoris, biceps femoris or tibialis anterior muscle fatigue; low back angle changed towards less  lordosis, pelvis movement increased, lower limb swelling increased and mental state decreased. Body discomfort was positively correlated with mental state. The observed changes suggest replacing office work sitting with standing should be done with caution. Practitioner Summary: Standing is being used to replace sitting by office workers; however, there are health risks associated with prolonged standing. In a laboratory study involving 2 h prolonged standing discomfort increased (all body areas), reaction time and mental state deteriorated while creative problem-solving improved. Prolonged standing should be undertaken with caution.

Lower limb blood flow and mean arterial pressure during standing and seated work: Implications for workplace posture recommendations

Sit-stand workstations are a popular workplace intervention. Organizations often require a medical professional's guidance for implementation. Therefore, it is important to understand potential negative outcomes associated with standing work, such as lower limb discomfort and peripheral vascular issues. The objective of this study was to compare changes in lower limb discomfort, blood pressure and blood flow accumulation during a light-load repetitive upper limb work task accomplished from seated and standing postures. At the Jewish Rehabilitation Hospital (Laval, Quebec, Canada), 16 participants were outfitted with Laser Doppler Flow (LDF) electrodes to measure blood flow in the lower limb, and a sphygmomanometer to measure lower limb mean arterial blood pressure (MAP). Participants completed simulated work over 34 min in standing and seated conditions. Repeated measures ANOVAs (Posture x Time) were used to assess the differences. There were significant effects for both Posture (p = 0.003) and Time (p = 0.007) for LDF-measured of blood flow accumulation in the soleus and the foot, with a mean increase of 77% blood flow over time in the standing posture, when compared to seated work. There was a significant 'Posture × Time' (p = 0.0034) interaction effect and a significant Posture (p = 0.0001) effect for MAP, with higher values in the standing posture by a mean of 37.2 mmHg. Posture had a significant effect (p < 0.001) on lower limb discomfort, with standing posture reporting higher levels. These results suggest that recommendations for using static standing work postures should be tempered, and physicians' guidance on workstation changes should consider the impacts on the lower limb.

Associations of prolonged standing with musculoskeletal symptoms-A systematic review of laboratory studies

While prolonged standing has shown to be detrimentally associated with musculoskeletal symptoms, exposure limits and underlying mechanisms are not well understood. We systematically reviewed evidence from laboratory studies on musculoskeletal symptom development during prolonged (≥20min) uninterrupted standing, quantified acute dose-response associations and described underlying mechanisms. Peer-reviewed articles were systematically searched for. Data from included articles were tabulated, and dose-response associations were statistically pooled. A linear interpolation of pooled dose-response associations was performed to estimate the duration of prolonged standing associated with musculoskeletal symptoms with a clinically relevant intensity of ≥9 (out of 100). We included 26 articles (from 25 studies with 591 participants), of which the majority examined associations of prolonged standing with low back and lower extremity symptoms. Evidence on other (e.g., upper limb) symptoms was limited and inconsistent. Pooled dose-response associations showed that clinically relevant levels of low back symptoms were reached after 71min of prolonged standing, with this shortened to 42min in those considered pain developers. Regarding standing-related low back symptoms, consistent evidence was found for postural mechanisms (i.e., trunk flexion and lumbar curvature), but not for mechanisms of muscle fatigue and/or variation in movement. Blood pooling was the most consistently reported mechanism for standing-related lower extremity symptoms. Evidence suggests a detrimental association of prolonged standing with low back and lower extremity symptoms. To avoid musculoskeletal symptoms (without having a-priori knowledge on whether someone will develop symptoms or not), dose-response evidence from this study suggests a recommendation to refrain from standing for prolonged periods >40min. Interventions should also focus on underlying pain mechanisms.

A narrative review of musculoskeletal problems of the lower extremity and back associated with the interface between occupational tasks, feet, footwear and flooring

At least 50% of workers are exposed to the risk of musculoskeletal disorders (MSD) due to spending prolonged hours standing at work. There is a lack of information regarding issues with the feet, solutions to the problem, and links between MSD, feet, footwear and flooring. The present article provides a narrative review of the research in this area, based on 31 papers. Workers who stand for large proportions of the working day had a level of MSD considerably greater than a normal population. Muscle co-activation, blood pooling, muscle fatigue and individual characteristics are all associated with MSD. Altering flooring provided mixed results, while footwear appeared to have the potential to affect MSD, although the dearth of literature limited the conclusions that could be drawn. Despite their inextricable link, literature regarding the relationship between occupational tasks, MSD, footwear and flooring remains limited and future studies will benefit from rigorously designed protocols.

Long-Lasting Changes in Muscle Twitch Force During Simulated Work While Standing or Walking

OBJECTIVE

The aim of this study was to evaluate the long-lasting effects of prolonged standing work on a hard floor or floor mat and slow-pace walking on muscle twitch force (MTF) elicited by electrical stimulation.

BACKGROUND

Prolonged standing work may alter lower-leg muscle function, which can be quantified by changes in the MTF amplitude and duration related to muscle fatigue. Ergonomic interventions have been proposed to mitigate fatigue and discomfort; however, their influences remain controversial.

METHOD

Ten men and eight women simulated standing work in 320-min experiments with three conditions: standing on a hard floor or an antifatigue mat and walking on a treadmill, each including three seated rest breaks. MTF in the gastrocnemius-soleus muscles was evaluated through changes in signal amplitude and duration.

RESULTS

The significant decrease of MTF amplitude and an increase of duration after standing work on a hard floor and on a mat persisted beyond 1 hr postwork. During walking, significant MTF metrics changes appeared 30 min postwork. MTF amplitude decrease was not significant after the first 110 min in any of the conditions; however, MTF duration was significantly higher than baseline in the standing conditions.

CONCLUSION

Similar long-lasting weakening of MTF was induced by standing on a hard floor and on an antifatigue mat. However, walking partially attenuated this phenomenon.

APPLICATION

Mostly static standing is likely to contribute to alterations of MTF in lower-leg muscles and potentially to musculoskeletal disorders regardless of the flooring characteristics. Occupational activities including slow-pace walking may reduce such deterioration in muscle function.

Associations of occupational standing with musculoskeletal symptoms: a systematic review with meta-analysis

OBJECTIVE

Given the high exposure to occupational standing in specific occupations, and recent initiatives to encourage intermittent standing among white-collar workers, a better understanding of the potential health consequences of occupational standing is required. We aimed to review and quantify the epidemiological evidence on associations of occupational standing with musculoskeletal symptoms.

DESIGN

A systematic review was performed. Data from included articles were extracted and described, and meta-analyses conducted when data were sufficiently homogeneous.

DATA SOURCES

Electronic databases were systematically searched.

ELIGIBILITY CRITERIA

Peer-reviewed articles on occupational standing and musculoskeletal symptoms from epidemiological studies were identified.

RESULTS

Of the 11 750 articles screened, 50 articles reporting 49 studies were included (45 cross-sectional and 5 longitudinal; n=88 158 participants) describing the associations of occupational standing with musculoskeletal symptoms, including low-back (39 articles), lower extremity (14 articles) and upper extremity (18 articles) symptoms. In the meta-analysis, 'substantial' (>4 hours/workday) occupational standing was associated with the occurrence of low-back symptoms (pooled OR (95% CI) 1.31 (1.10 to 1.56)). Evidence on lower and upper extremity symptoms was too heterogeneous for meta-analyses. The majority of included studies reported statistically significant detrimental associations of occupational standing with lower extremity, but not with upper extremity symptoms.

CONCLUSIONS

The evidence suggests that substantial occupational standing is associated with the occurrence of low-back and (inconclusively) lower extremity symptoms, but there may not be such an association with upper extremity symptoms. However, these conclusions are tentative as only limited evidence was found from high-quality, longitudinal studies with fully adjusted models using objective measures of standing.

Influence of unstable footwear on lower leg muscle activity, volume change and subjective discomfort during prolonged standing

PURPOSE

The present study was an attempt to investigate the effect of unstable footwear on lower leg muscle activity, volume change and subjective discomfort during prolonged standing.

METHODS

Ten healthy subjects were recruited to stand for 2 h in three footwear conditions: barefoot, flat-bottomed shoe and unstable shoe. During standing, lower leg discomfort and EMG activity of medial gastrocnemius (MG) and tibialis anterior (TA) muscles were continuously monitored. Changes in lower leg volume over standing time also were measured.

RESULTS

Lower leg discomfort rating reduced significantly while subjects standing on unstable shoe compared to the flat-bottomed shoe and barefoot condition. For lower leg volume, less changes also were observed with unstable shoe. The activity level and variation of right MG muscle was greater with unstable shoe compared to the other footwear conditions; however regarding the left MG muscle, significant difference was found between unstable shoe and flat-bottomed shoe only for activity level. Furthermore no significant differences were observed for the activity level and variation of TA muscles (right/left) among all footwear conditions.

CONCLUSIONS

The findings suggested that prolonged standing with unstable footwear produces changes in lower leg muscles activity and leads to less volume changes. Perceived discomfort also was lower for this type of footwear and this might mean that unstable footwear can be used as ergonomic solution for employees whose work requires prolonged standing.

Long-Term Muscle Fatigue After Standing Work

OBJECTIVE

The aims of this study were to determine long-term fatigue effects in the lower limbs associated with standing work and to estimate possible age and gender influences.

BACKGROUND

The progressive accumulation of muscle fatigue effects is assumed to lead to musculoskeletal disorders, as fatigue generated by sustained low-level exertions exhibits long-lasting effects. However, these effects have received little attention in the lower limbs.

METHOD

Fourteen men and 12 women from two different age groups simulated standing work for 5 hr including 5-min seated rest breaks and a 30-min lunch. The younger group was also tested in a control day. Muscle fatigue was quantified by electrically induced muscle twitches (muscle twitch force [MTF]), postural stability, and subjective evaluation of discomfort.

RESULTS

MTF showed a significant fatigue effect after standing work that persisted beyond 30 min after the end of the workday. MTF was not affected on the control day. The center of pressure displacement speed increased significantly over time after standing work but was also affected on the control day. Subjective evaluations of discomfort indicated a significant increase in perception of fatigue immediately after the end of standing work; however, this perception did not persist 30 min after. Age and gender did not influence fatigue.

CONCLUSION

Objective measures show the long-term effects of muscle fatigue after 5 hr of standing work; however, this fatigue is no longer perceived after 30 min of rest postwork.

APPLICATION

The present results suggest that occupational activities requiring prolonged standing are likely to contribute to lower-extremity and/or back disorders.

Alteration in cardiovascular and postural control relationship in non-fainting elderly individuals

It is known that standing induces orthostatic stress on the cardiovascular system. Our previous works have presented that the postural control during standing and cardiovascular changes are related to each other in the health young individuals. However, it remains to be checked if such a relationship is present in the elderly individuals as well. The present study conducted experiments similar to our previous studies and collected data for the muscle activation in lower leg muscles along with blood pressure during a passive stand test. Application of wavelet transform coherence method provided time frequency distribution of the coherence between the two signals. High coherence (>threshold) was observed between the two signals suggesting a strong relationship. Additionally, a frequency dependent behavior was observed between the two signals. The results from this study present strong evidence that there is a change in the relationship between the two signals with aging.

A Physiological Perspective on Treadmill and Sit-to-Stand Workstations

Active workstations, such as treadmill and sit-to-stand workstations, enable office employees to break prolonged sitting with bouts of light-intensity walking and/or standing. Compared with sitting, walking and/or standing accumulated during the workday using these workstations will increase muscle contractions, which may influence blood flow, energy expenditure, metabolism, musculoskeletal health, and brain function. Physiological responses when using treadmill and sit-to-stand workstations may vary due to differences in muscle contraction type (dynamic vs. static) and may thus affect cardio-metabolic and musculoskeletal health and brain function in different ways.

Physiological interdependence of the cardiovascular and postural control systems under orthostatic stress

The cardiovascular system has been observed to respond to changes in human posture and the environment. On the same lines, frequent fallers have been observed to suffer from cardiovascular deficits. The present article aims to demonstrate the existence of interactions between the cardiovascular and postural control systems. The behavior of the two systems under orthostatic challenge was studied through novel adaptations of signal processing techniques. To this effect, the interactions between the two systems were assessed with two metrics, coherence and phase lock value, based on the wavelet transform. Measurements from the cardiovascular system (blood pressure), lower limb muscles (surface electromyography), and postural sway (center of pressure) were acquired from young healthy adults (n = 28, men = 12, age = 20-28 yr) during quiet stance. The continuous wavelet transform was applied to decompose the representative signals on a time-scale basis in a frequency region of 0.01 to 0.1 Hz. Their linear coupling was quantified through a coherence metric, and the synchrony was characterized via the phase information. The outcomes of this study present evidence that the cardiovascular and postural control systems work together to maintain homeostasis under orthostatic challenge. The inferences open a new direction of study for effects under abnormalities and extreme environmental conditions.

Statistical validation of wavelet transform coherence method to assess the transfer of calf muscle activation to blood pressure during quiet standing

BACKGROUND

Continuous and discrete wavelet transforms have been established as valid tools to analyze non-stationary and transient signals over Fourier domain methods. Additionally, Fourier transform based coherence methods provide aggregate results but do not provide insights into the changes in coherent behavior over time, hence limiting their utility.

METHODS

Statistical validation of the wavelet transform coherence (WTC) was conducted with simulated data sets. Time frequency maps of signal coherence between calf muscle electromyography (EMG) and blood pressure (BP) were obtained by WTC to provide further insight into their interdependent time-varying behavior via the skeletal muscle pump during quiet stance. Data were collected from healthy young males (n = 5, 19-28 years) during a quiet stance on a balance platform. Waveforms for EMG and BP were acquired and processed for further analysis.

RESULTS

Low values of bias and standard deviation (< 0.1) were observed and the use of both simulated and real data demonstrated that the WTC method was able to identify time points of significant coherence (> Threshold) and objectively detect existence of interdependent activity between the calf muscle EMG and blood pressure.

CONCLUSIONS

The WTC method effectively identified the presence of linear coupling between the EMG and BP signals during quiet standing. Future studies with more human data are needed to establish the exact characteristics of the identified relationship.