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The effect of work pace on workload, motor variability and fatigue during simulated light assembly work

This study investigated the effect of work pace on workload, motor variability and fatigue during light assembly work. Upper extremity kinematics and electromyography (EMG) were obtained on a cycle-to-cycle basis for eight participants during two conditions, corresponding to "normal" and "high" work pace according to a predetermined time system for engineering. Indicators of fatigue, pain sensitivity and performance were recorded before, during and after the task. The level and variability of muscle activity did not differ according to work pace, and manifestations of muscle fatigue or changed pain sensitivity were not observed. In the high work pace, however, participants moved more efficiently, they showed more variability in wrist speed and acceleration, but they also made more errors. These results suggest that an increased work pace, within the range addressed here, will not have any substantial adverse effects on acute motor performance and fatigue in light, cyclic assembly work.STATEMENT OF RELEVANCE: In the manufacturing industry, work pace is a key issue in production system design and hence of interest to ergonomists as well as engineers. In this laboratory study, increasing the work pace did not show adverse effects in terms of biomechanical exposures and muscle fatigue, but it did lead to more errors. For the industrial engineer, this observation suggests that an increase in work pace might diminish production quality, even without any noticeable fatigue being experienced by the operators.

Postoperative muscle loss, protein intake, physical activity and outcome associations

Background: Skeletal muscle loss is often observed in intensive care patients. However, little is known about postoperative muscle loss, its associated risk factors, and its long-term consequences. The aim of this prospective observational study is to identify the incidence of and risk factors for surgery-related muscle loss (SRML) after major abdominal surgery, and to study the impact of SRML on fatigue and survival. Methods: Patients undergoing major abdominal cancer surgery were included in the MUSCLE POWER STUDY. Muscle thickness was measured by ultrasound in three muscles bilaterally (biceps brachii, rectus femoris, and vastus intermedius). SRML was defined as a decline of 10 per cent or more in diameter in at least one arm and leg muscle within 1 week postoperatively. Postoperative physical activity and nutritional intake were assessed using motility devices and nutritional diaries. Fatigue was measured with questionnaires and 1-year survival was assessed with Cox regression analysis. Results: A total of 173 patients (55 per cent male; mean (s.d.) age 64.3 (11.9) years) were included, 68 of whom patients (39 per cent) showed SRML. Preoperative weight loss and postoperative nutritional intake were statistically significantly associated with SRML in multivariable logistic regression analysis (P < 0.050). The combination of insufficient postoperative physical activity and nutritional intake had an odds ratio of 4.00 (95 per cent c.i. 1.03 to 15.47) of developing SRML (P = 0.045). No association with fatigue was observed. SRML was associated with decreased 1-year survival (hazard ratio 4.54, 95 per cent c.i. 1.42 to 14.58; P = 0.011). Conclusion: SRML occurred in 39 per cent of patients after major abdominal cancer surgery, and was associated with a decreased 1-year survival.

Skeletal muscle alterations in patients with acute Covid-19 and post-acute sequelae of Covid-19

Skeletal muscle-related symptoms are common in both acute coronavirus disease (Covid)-19 and post-acute sequelae of Covid-19 (PASC). In this narrative review, we discuss cellular and molecular pathways that are affected and consider these in regard to skeletal muscle involvement in other conditions, such as acute respiratory distress syndrome, critical illness myopathy, and post-viral fatigue syndrome. Patients with severe Covid-19 and PASC suffer from skeletal muscle weakness and exercise intolerance. Histological sections present muscle fibre atrophy, metabolic alterations, and immune cell infiltration. Contributing factors to weakness and fatigue in patients with severe Covid-19 include systemic inflammation, disuse, hypoxaemia, and malnutrition. These factors also contribute to post-intensive care unit (ICU) syndrome and ICU-acquired weakness and likely explain a substantial part of Covid-19-acquired weakness. The skeletal muscle weakness and exercise intolerance associated with PASC are more obscure. Direct severe acute respiratory syndrome coronavirus (SARS-CoV)-2 viral infiltration into skeletal muscle or an aberrant immune system likely contribute. Similarities between skeletal muscle alterations in PASC and chronic fatigue syndrome deserve further study. Both SARS-CoV-2-specific factors and generic consequences of acute disease likely underlie the observed skeletal muscle alterations in both acute Covid-19 and PASC.

Exercise-induced muscle fatigue leads to changes in gait-related parameters among older adults: a systematic review and meta-analysis

Respiratory and non-respiratory symptoms in patients with IPF or sarcoidosis and controls

Introduction: Besides dyspnoea and cough, patients with idiopathic pulmonary fibrosis (IPF) or sarcoidosis may experience distressing non-respiratory symptoms, such as fatigue or muscle weakness. However, whether and to what extent symptom burden differs between patients with IPF or sarcoidosis and individuals without respiratory disease remains currently unknown. Objectives: To study the respiratory and non-respiratory burden of multiple symptoms in patients with IPF or sarcoidosis and to compare the symptom burden with individuals without impaired spirometric values, FVC and FEV1 (controls). Methods: Demographics and symptoms were assessed in 59 patients with IPF, 60 patients with sarcoidosis and 118 controls (age ≥18 years). Patients with either condition were matched to controls by sex and age. Severity of 14 symptoms was assessed using a Visual Analogue Scale. Results: 44 patients with IPF (77.3% male; age 70.6±5.5 years) and 44 matched controls, and 45 patients with sarcoidosis (48.9% male; age 58.1±8.6 year) and 45 matched controls were analyzed. Patients with IPF scored higher on 11 symptoms compared to controls (p<0.05), with the largest differences for dyspnoea, cough, fatigue, muscle weakness and insomnia. Patients with sarcoidosis scored higher on all 14 symptoms (p<0.05), with the largest differences for dyspnoea, fatigue, cough, muscle weakness, insomnia, pain, itch, thirst, micturition (night, day). Conclusions: Generally, respiratory and non-respiratory symptom burden is significantly higher in patients with IPF or sarcoidosis compared to controls. This emphasizes the importance of awareness for respiratory and non-respiratory symptom burden in IPF or sarcoidosis and the need for additional research to study the underlying mechanisms and subsequent interventions.

The correlation of muscle quantity and quality between all vertebra levels and level L3, measured with CT

INTRODUCTION: In patients with cancer, low muscle mass has been associated with a higher risk of fatigue, poorer treatment outcomes, and mortality. To determine body composition with computed tomography (CT), measuring the muscle quantity at the level of lumbar 3 (L3) is suggested. However, in patients with cancer, CT imaging of the L3 level is not always available. Thus far, little is known about the extent to which other vertebra levels could be useful for measuring muscle status. In this study, we aimed to assess the correlation of the muscle quantity and quality between any vertebra level and L3 level in patients with various tumor localizations.METHODS: Two hundred-twenty Positron Emission Tomography (PET)-CT images of patients with four different tumor localizations were included: 1. head and neck ( n = 34), 2. esophagus ( n = 45), 3. lung ( n = 54), and 4. melanoma ( n = 87). From the whole body scan, 24 slices were used, i.e., one for each vertebra level. Two examiners contoured the muscles independently. After contouring, muscle quantity was estimated by calculating skeletal muscle area (SMA) and skeletal muscle index (SMI). Muscle quality was assessed by calculating muscle radiation attenuation (MRA). Pearson correlation coefficient was used to determine whether the other vertebra levels correlate with L3 level. RESULTS: For SMA, strong correlations were found between C1-C3 and L3, and C7-L5 and L3 ( r = 0.72-0.95). For SMI, strong correlations were found between the levels C1-C2, C7-T5, T7-L5, and L3 ( r = 0.70-0.93), respectively. For MRA, strong correlations were found between T1-L5 and L3 ( r = 0.71-0.95). DISCUSSION: For muscle quantity, the correlations between the cervical, thoracic, and lumbar levels are good, except for the cervical levels in patients with esophageal cancer. For muscle quality, the correlations between the other levels and L3 are good, except for the cervical levels in patients with melanoma. If visualization of L3 on the CT scan is absent, the other thoracic and lumbar vertebra levels could serve as a proxy to measure muscle quantity and quality in patients with head and neck, esophageal, lung cancer, and melanoma, whereas the cervical levels may be less reliable as a proxy in some patient groups.