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Overexertion, usually caused by manual material handling (MMH), often leads to work-related musculoskeletal disorders (WMSDs). These can be prevented during MMH tasks by redesigning them to include sufficient rest periods. Task characteristics play an important role in the redesign of the job. This study evaluated the effect of five task characteristics—weight, duration, frequency, distance, and angle of symmetry—at two levels on the maximum voluntary contraction recovery rate (Muscle Voluntary Contraction Recovery Time (MVCRT), defined as the time required for the muscle to recover to 80% of the initial Maximum Voluntary Contraction (MVC) value) of the muscles and developed a work-rest interval model based on these task characteristics. The results show that the weight and duration had a significant effect on MVCRT, increasing it by 32% and 21%, respectively. The interaction between frequency and distance also significantly impacted MVCRT. A simplified mathematical model was developed and validated by comparing a set of the model-generated data with experimental data. The simplified regression model demonstrated moderate predictive capability with an R2 value of 0.52. The ANOVA shows no significant difference between the data. The study’s results and mathematical models can be used during task design to reduce WMSDs. Because approximately 48% of the variability in MVCRT remained unexplained, direct application of the model to establish worker-specific work-rest intervals may result in underestimation or overestimation of recovery requirements. Therefore, the model should be interpreted as a preliminary estimation framework. 

Climbing A-frame ladders places high physical demand on the legs. We measured how lower-limb muscles work through each phase of climbing to identify when and where effort is greatest. Using surface electromyography, we found that the quadriceps are most active while supporting the body, the calf muscles assist during push-off, and the tibialis anterior engages mainly for foot clearance. During descent, the quadriceps appeared to playa substantialrole in controlling lowering through eccentric action. These findings provide insight into when leg support may be most needed and suggest potential timing windows for future exoskeleton assistance during ladder climbing. 

Maximum aerobic capacity (MAC) helps in physical work capacity evaluation. In practice, the construction jobs are designed using the standard treadmill or ergometer MAC value, which is inappropriate and leads to injuries. According to NIOSH, the average oxygen consumption during an 8 h day is recommended to be no more than 33% of the exercise-specific MAC. Therefore, there is a necessity for construction activity-specific MAC exercise protocols and estimation models. The aim of the study is to develop MAC estimation models for common construction activities such as walking, carrying, lifting, and combined (carrying, dragging, hammering, lifting, and wrenching) using the submaximal exercise test mode. Ten male participants performed all four activities at three different intensities for five minutes each. The oxygen uptake and heart rate were recorded for each trial. This study shows that the average MAC value for walking, carrying, lifting, and combined activities is 0.779 gpm (2.95 L/m), 0.674 gpm (2.55 L/m), 0.745 gpm (2.82 L/m), and 0.608 gpm (2.30 L/m), respectively. The MAC value of combined construction activities is significantly lower than walking (28%), carrying (11%), and lifting (22%). The study recommends using a construction activity-specific exercise protocol for evaluating jobs or workers to prevent a mismatch between job demands and worker capabilities. 

Exoskeletons are increasingly used in industrial settings, yet most are designed for structured, repetitive tasks, limiting adaptability to dynamic movements. In construction, frequent locomotion tasks demand continuous lower-limb engagement, and ladder climbing places substantial loads on coordination and flexibility. This study aimed to identify key muscles involved in climbing to support the development of adaptive exoskeletons. Ten healthy male participants (33.8 ± 3.4 years; 178.7 ± 5.0 cm; 87.4 ± 16.1 kg) performed vertical and A-frame ladder ascents in a controlled laboratory setting. Surface electromyography was recorded from eight right-leg muscles and processed using band-pass filtering, rectification, and root mean square smoothing. Two normalization strategies were applied: walking normalization, expressing climbing activity relative to level walking, and maximum voluntary contraction normalization, with amplitudes expressed as a percentage of maximum voluntary contraction. Our results showed that all muscles were more active in climbing than walking, with quadriceps (vastus medialis, vastus lateralis, rectus femoris) exhibiting the greatest increases. Gastrocnemius also approached or exceeded 100%MVC, tibialis anterior averaged 70–80%MVC, and hamstrings contributed 20–40%MVC mainly for stabilization. Vertical and A-frame ladders followed similar patterns with subtle posture-related variations. These findings highlight knee extensors as primary targets for adaptive exoskeleton assistance during ladder climbing tasks commonly performed on construction sites. 

The physical workload evaluation of construction activities will help to prevent excess physical fatigue or overexertion. The workload determination involves measuring physiological responses such as oxygen uptake (VO2) while performing the work. The objective of this study is to develop a procedure for automatic oxygen uptake prediction using the worker’s forearm muscle activity and motion data. The fused IMU and EMG data were analyzed to build a bidirectional long-short-term memory (BiLSTM) model to predict VO2. The results show a strong correlation between the IMU and EMG features and oxygen uptake (R = 0.90, RMSE = 1.257 mL/kg/min). Moreover, measured (9.18 ± 1.97 mL/kg/min) and predicted (9.22 ± 0.09 mL/kg/min) average oxygen consumption to build one scaffold unit are significantly the same. This study concludes that the fusion of IMU and EMG features resulted in high model performance compared to IMU and EMG alone. The results can facilitate the continuous monitoring of the physiological status of construction workers and early detection of any potential occupational risks. 

Despite the introduction of preventive safety measures, such as near-miss reporting, to mitigate accidents and minimize fatalities, construction workers are constantly exposed to stressful situations that negatively affect their safety behavior and reporting efficiency. Occupational stress is induced by various factors, with mental stress and auditory stress being common workplace stressors that impact workers on the job site. While previous studies have demonstrated the effect of stressor conditions on workers’ hazard recognition and safety performance, research gaps persist regarding the direct impact of workplace stressors on workers’ stress levels and near-miss recognition performance. This study investigates workers’ near-miss recognition ability through an eye-tracking experiment conducted in a controlled environment under mental and auditory stress conditions. The findings from this study reveal that workplace stressors triggered by mental and auditory stress can adversely affect worker stress levels, safety behavior, and cognitive processing toward near-miss recognition. Visual attention towards near-miss scenarios was reduced by 26% for mental stress conditions and by 46% for auditory stress conditions compared to baseline. The results may potentially open avenues for developing wearable stress prediction and safety intervention models using bio-sensing technology and personalized safety training programs tailored to individuals with low identification abilities.