Modeling and Validation of Fatigue and Recovery of Muscles for Manual Demolition Tasks

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.

Fatigue and Recovery of Muscles for Pulling Tasks

“…Exploring the relationship between the recovery level of muscle strength and the recovery time periods is essential for job designers. Muscle fatigue recovery is often assessed by measuring muscle strength over a recovery time period [ 30 , 31 , 32 , 33 ]. Muscle strength models have been reported established [ 30 , 31 , 32 , 33 ].…”

“…Muscle fatigue recovery is often assessed by measuring muscle strength over a recovery time period [ 30 , 31 , 32 , 33 ]. Muscle strength models have been reported established [ 30 , 31 , 32 , 33 ]. Those models are also helpful in determining rest allowance for workers.…”

“…Subjective ratings provide an easy assessment tool for muscle fatigue. The relationship between these ratings and objective muscle strength data has been reported [ 33 , 34 , 35 , 36 ]. Models based on subjective data were adopted to assess muscle fatigue [ 35 , 36 , 37 ] and muscle fatigue recovery [ 33 ].…”

“…The relationship between these ratings and objective muscle strength data has been reported [ 33 , 34 , 35 , 36 ]. Models based on subjective data were adopted to assess muscle fatigue [ 35 , 36 , 37 ] and muscle fatigue recovery [ 33 ]. These models provided estimations of muscle fatigue levels over a certain period.…”

“…The levels of muscle fatigue recovery for pulling tasks under walking conditions, however, have not been explored. When conducting the muscle fatigue recovery test, an endurance experiment was usually adopted to induce muscle fatigue [ 30 , 31 , 33 ]. Therefore, we designed a muscle fatigue and a muscle fatigue recovery test for pulling tasks in this study.…”