Abstract
Manual demolition tasks are heavy, physically demanding tasks that could cause muscle fatigue accumulation and lead to work-related musculoskeletal disorders (WMSDs). Fatigue and recovery models of muscles are essential in understanding the accumulation and the reduction in muscle fatigue for forceful exertion tasks. This study aims to explore the onset of muscle fatigue under different work/rest arrangements during manual demolition tasks and the offset of fatigue over time after the tasks were performed. An experiment, including a muscle fatigue test and a muscle fatigue recovery test, was performed. Seventeen male adults without experience in demolition hammer operation were recruited as human participants. Two demolition hammers (large and small) were adopted. The push force was either 20 or 40 N. The posture mimicked that of a demolition task on a wall. In the muscle fatigue test, the muscle strength (MS) before and after the demolition task, maximum endurance time (MET), and the Borg category-ratio-10 (CR-10) ratings of perceived exertion after the demolition task were measured. In the muscle fatigue recovery test, MS and CR-10 at times 1, 2, 3, 4, 5, and 6 min were recorded. Statistical analyses were performed to explore the influence of push force and the weight of the tool on MS, MET, and CR-10. Both muscle fatigue models and muscle fatigue recovery models were established and validated. The results showed that push force affected MET significantly (p < 0.05). The weight of the tool was significant (p < 0.05) only on the CR-10 rating after the first pull. During the muscle fatigue recovery test, the MS increase and the CR-10 decrease were both significant (p < 0.05) after one or more breaks. Models of MET and MS prediction were established to assess muscle fatigue recovery, respectively. The absolute (AD) and relative (RD) deviations of the MET model were 1.83 (±1.94) min and 34.80 (±31.48)%, respectively. The AD and RD of the MS model were 1.39 (±0.81) N and 1.9 (±1.2)%, respectively. These models are capable of predicting the progress and recovery of muscle fatigue, respectively, and may be adopted in work/rest arrangements for novice workers performing demolition tasks.
Highlights
Work-related musculoskeletal disorders (WMSDs) are disorders of muscles, bones, nerves, tendons, ligaments, joints, and cartilages in different body segments caused by factors, such as excessive load, vibration, repetitive operation, and awkward posture [1]
In China, the literature has shown work-related musculoskeletal disorders (WMSDs) are common at work in hospitals [3], coal mines [4], factories [5], farms [6], transportation [7], and construction sites [8]
This study aims to explore the development of muscle fatigue and the progress of muscle recovery for manual demolition tasks
Summary
Work-related musculoskeletal disorders (WMSDs) are disorders of muscles, bones, nerves, tendons, ligaments, joints, and cartilages in different body segments caused by factors, such as excessive load, vibration, repetitive operation, and awkward posture [1]. They have become the second most common occupational disease in many developing and industrialized countries. Many countries, such as the United States, Britain, Germany, and. Japan, have listed these disorders as occupational diseases [2]. Hand–arm vibration syndromes have been included as one of the occupational diseases in China [9], other WMSDs, such as
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