Efficacy of three interventions at mitigating the adverse effects of muscle fatigue on postural control

Low Back Biomechanics during Repetitive Deadlifts: A Narrative Review

OCCUPATIONAL APPLICATIONSHeavy deadlifting is used as a screening tool or training protocol for recruitment and retention in physically-demanding occupations, especially in the military. Spinal loads experienced during heavy deadlifts, particularly shearing forces, are well above recommended thresholds for lumbar spine injury in occupational settings. Although members of the noted occupation likely have stronger musculoskeletal systems compared to the general population, experiencing shearing forces that are 2 to 4 times larger than the threshold of injury, particularly under repetitive deadlift, may transform a screening tool or training protocol to an occupationally-harmful physical activity.

The effect of trunk muscle fatigue on postural control of upright stance: A systematic review

BACKGROUND

Fatigability and postural control deficits are both serious concerns in a variety of chronic musculoskeletal conditions. Research has shown that muscle fatigue may adversely affect postural control. This is while the evidence on the relevance of fatigue to postural control has never been summarized nor critically appraised.

RESEARCH QUESTION

Is there sufficient and strong enough evidence to accept trunk muscle fatigue as a contributing factor to postural control alterations during upright standing posture?.

METHODS

EMBASE, Scopus, ELSEVIER, PubMed, ProQuest, Google scholar and reference lists of the relevant articles were searched through April 2018. Studies having investigated the trunk muscle fatigue effect on postural control in asymptomatic individuals were included in the study. Only those studies having assessed postural control in terms of center of pressure driven variables were included.

RESULTS

Twelve studies (218 asymptomatic participants) matched the inclusion criteria of this systematic review. Their results supported the hypothesis that fatigue has a significant effect on postural control in terms of the time domain variables. Sway velocity was consistently found to be affected by fatigue. The results were inconsistent in the frequency domain. The only study on the structural dynamics of center of pressure displacements also confirmed such a relationship.

SIGNIFICANCE

The present review indicates that postural control is altered in asymptomatic individuals following trunk muscle fatigue. This may suggest that trunk muscle endurance training is crucial to address postural impairment in chronic spine musculoskeletal conditions.

The Impact of a Rigorous Multiple Work Shift Schedule and Day Versus Night Shift Work on Reaction Time and Balance Performance in Female Nurses: A Repeated Measures Study

OBJECTIVE

The aim of this study was to determine the impact of a demanding work schedule involving long, cumulative work shifts on response time and balance-related performance outcomes and to evaluate the prevalence of musculoskeletal disorders between day and night shift working nurses.

METHODS

A questionnaire was used to identify the prevalence of past (12-month) and current (7-day) musculoskeletal disorders. Nurses worked three 12-hour work shifts in a 4-day period. Reaction time and balance tests were conducted before and after the work period.

RESULTS

The work period induced impairments for reaction time, errors on reaction time tasks, and balance performance, independent of shift type. Musculoskeletal symptom prevalence was high in workers of both work shifts.

CONCLUSIONS

Compressed work shifts caused performance-based fatigue in nurses. Reaction time and balance tests may be sensitive fatigue identification markers in nurses.

HEALTHY STATE MONITOR OF UPPER LIMB FOR SPACE FLIGHT TASK BASED ON SIGNAL ANALYSES OF MULTIPLE MUSCLE FORCES

A novel healthy state monitor method of upper limb for space flight task is proposed. Without taking other complex diagnosis equipment in orbit, this method only uses the ordinary exercise instruments to collect and analyze the multiple muscle forces of astronauts, and deduces where the serious muscle atrophy occurs in their muscle groups of upper limb. First, the typical multiple muscle forces data of upper limb are accumulated. A 45-day 6-degree head-down tilt bed rest experiment together with a multiple muscle forces test experiment are carried out to collect the corresponding data. These data include both the muscle force data of healthy state and the related data of unhealthy state. Second, the Wavelet Packet Transform (WPT) and the Empirical Mode Decomposition (EMD) methods are used to compute the signal features of these data above. Third, a Support Vector Machine (SVM) classifier is trained by the related signal features. Finally, the trained SVM can be utilized to evaluate the healthy state of upper limb in orbit for astronaut. If the output of SVM is negative, the C-means method and the Euclidean distance can be used to locate the abnormal muscle forces and muscle groups. The concept of typical muscle group health state evaluation for upper limb is emphasized in this paper. The comparisons among the traditional diagnosis-based method, the electromyogram (EMG)-based muscle forces analysis method, and the proposed method are made. Many experiment results on ground have verified the effectiveness of proposed method.

Work organization and health among immigrant women: Latina manual workers in North Carolina

OBJECTIVES

We sought to describe work organization attributes for employed immigrant Latinas and determine associations of work organization with physical health, mental health, and health-related quality of life.

METHODS

We conducted a cross-sectional survey with 319 employed Latinas in western North Carolina (2009-2011). Measures included job demands (heavy load, awkward posture, psychological demand), decision latitude (skill variety, job control), support (supervisor control, safety climate), musculoskeletal symptoms, mental health (depressive symptoms), and mental (MCS) and physical component score (PCS) health-related quality of life.

RESULTS

Three fifths reported musculoskeletal symptoms. Mean scores for depression, MCS, and PCS were 6.2 (SE = 0.2), 38.3 (SE = 0.5), and 42.8 (SE = 0.3), respectively. Greater job demands (heavy load, awkward posture, greater psychological demand) were associated with more musculoskeletal and depressive symptoms and worse MCS. Less decision latitude (lower skill variety, job control) was associated with more musculoskeletal and depressive symptoms. Greater support (supervisor's power and safety climate) was associated with fewer depressive symptoms and better MCS.

CONCLUSIONS

Work organization should be considered to improve occupational health of vulnerable women workers. Additional research should delineate the links between work organization and health among vulnerable workers.

The effects of work organization on the health of immigrant manual workers: A longitudinal analysis

This analysis uses a longitudinal design to examine the associations of work organization and health outcomes among Latino manual workers. Participants included 247 Latino workers who completed baseline and 1-year follow-up interviews and clinical examinations. Health outcome measures were epicondylitis, rotator cuff syndrome, back pain, and depressive symptoms. Independent measures were measures of job demand, job control, and job support. Workers commonly experienced rotator cuff syndrome (6.5%), back pain (8.9%), and depressive symptoms (11.2%); fewer experienced epicondylitis (2.4%). Psychological demand was associated with rotator cuff syndrome; awkward position and decision latitude were associated with back pain. Decreased skill variety but increased decision latitude was associated with elevated depressive symptoms. Work context factors are important for health outcomes among vulnerable workers. Further research is needed to expand upon this work, particularly cultural perspectives on job support.

Musculoskeletal and neurological injuries associated with work organization among immigrant Latino women manual workers in North Carolina

BACKGROUND

This analysis examines the associations of work organization attributes among Latino women in manual occupations with musculoskeletal and neurological injuries.

METHODS

Participants included 234 women in western North Carolina. Outcome measures included epicondylitis, rotator cuff syndrome, back pain, and carpal tunnel syndrome. Independent measures included indicators of job demand, job control, and job support, as well as personal characteristics.

RESULTS

Latina workers commonly experienced epicondylitis, rotator cuff syndrome, back pain, and CTS. Awkward posture and decision latitude were associated with epicondylitis. Rotator cuff syndrome was associated with awkward posture and psychological demand. Awkward posture and psychological demand, and decreased skill variety and job control were related to CTS.

CONCLUSIONS

Work organization factors are potentially important for musculoskeletal and neurological injury among vulnerable workers. Research is required to understand the associations of work and health outcomes of these women. Policy initiatives need to consider how work organization affects health.

Physiological and biomechanical responses to a prolonged repetitive asymmetric lifting activity

This study investigated the effects of a prolonged repetitive asymmetric lifting task on behavioural adaptations during repetitive lifting activity, measures of tissue oxygenation and spine kinematics. Seventeen volunteers repeatedly lifted a box, normalised to 15% of the participant's maximum lifting strength, at the rate of 10 lifts/min for a period of 60 min. The lifts originated in front of the participants at ankle level and terminated on their left side at waist level. Overall, perceived workload increased during the repetitive lifting task. Erector spinae oxygenation levels, assessed using near-infrared spectroscopy, decreased significantly over time. Behavioural changes observed during the repetitive lifting task included increases in the amount of forward bending, the extension velocity and the lateral bending velocity, and a reduced lateral bending moment on the spine. These changes, with the exception of the reduced lateral bending moment, are associated with increased risk of low back disorder.

Effects of lumbar extensor fatigue and surface inclination on postural control during quiet stance

A number of work environments require workers to perform tasks on inclined surfaces. Such tasks, along with muscle fatigue, can impair postural control and increase falling risks. The objective of this study was to determine the effects of surface inclination angle, standing direction, and lumbar extensor fatigue on postural control during quiet standing. A group of 16 young, healthy participants were tested while standing on inclined surfaces before and after lumbar extensor fatigue (induced by repetitive isotonic exercise). Three inclination angles (0°, 18° and 26°) and three standing directions (uphill, downhill, and lateral facing) were examined. Postural control was assessed using several measures derived from center-of-pressure time series and subjectively perceived stability. Significant main and interactive effects of inclination angle and standing direction were found for all dependent measures. The adverse effects of standing on inclined surfaces were found to differ between the three standing directions. In general, dose-response relationships with inclination angle were evident, particularly in the lateral-facing direction. Fatigue-related effects differed between conditions, suggesting that the adverse effect of lumbar extensor fatigue on postural control depend on inclination angle and standing direction. These findings may facilitate the development of fall prevention interventions for work involving inclined surfaces.