Amitava Halder

This gait biomechanics study investigated stride length (SL), stride duration (SDN), the peak values of ground reaction forces (GRFs_peak), required coefficient of friction (RCOF_peak), leg joints’ angles (angle_peak), angular velocity (ang_velx.peak), angular acceleration (ang_accx.peak), minimum angle (angle_min.) of the foot, and muscles’ electromyography (EMG) during the stance phase (SP) of the dominant leg following an exhaustive stair ascent on a stair machine. Data were collected by a three-dimensional motion capture system synchronized with EMG and force plate while walking down a 10° inclined stationary walkway. Although the leg muscles’ EMG showed no significant local muscle fatigue (LMF) during post-exhaustive walking downwards, the SL was significantly (p < 0.05) shorter than the pre-exhaustive. The mean vertical GRFz_peak. was significantly (p ≤ .01) reduced during late stance (LS) phase, however, the antero-posterior GRFy_peak. was found to be significantly (p ≤ 0.01) higher. The RCOF_peak. was significantly (p ≤ .05) higher during the post-exhaustive walking downwards, LS phase. The available coefficient of friction value of ~ 0.350 seems to be the RCOF to reduce slips and falls on an inclined dry surface. None of the post-exhaustive lower limb joints’ angle_peak, angle_min., ang._velx.peak, and ang._accx.peak were significantly changed in post-exhaustion walking, except the knee ang._accx.peak., which was significantly (p < 0.05) increased during the LS period. The constrained post-exhaustive gait biomechanics indicate a perturbed gait, which may increase the risks for slips and fall-related accidents, when walking downwards and working on slopes. However, the non-significant joint angle changes imply that walking down is less demanding in a kinesiological perspective compared to walking up an incline.

This paper describes the functional development of the ClimApp tool (available for free on iOS and Android devices), which combines current and 24 h weather forecasting with individual information to offer personalised guidance related to thermal exposure. Heat and cold stress assessments are based on ISO standards and thermal models where environmental settings and personal factors are integrated into the ClimApp index ranging from −4 (extremely cold) to +4 (extremely hot), while a range of −1 and +1 signifies low thermal stress. Advice for individuals or for groups is available, and the user can customise the model input according to their personal situation, including activity level, clothing, body characteristics, heat acclimatisation, indoor or outdoor situation, and geographical location. ClimApp output consists of a weather summary, a brief assessment of the thermal situation, and a thermal stress warning. Advice is provided via infographics and text depending on the user profile. ClimApp is available in 10 languages: English, Danish, Dutch, Swedish, Norwegian, Hellenic (Greek), Italian, German, Spanish and French. The tool also includes a research functionality providing a platform for worker and citizen science projects to collect individual data on physical thermal strain and the experienced thermal strain. The application may therefore improve the translation of heat and cold risk assessments and guidance for subpopulations. ClimApp provides the framework for personalising and downscaling weather reports, alerts and advice at the personal level, based on GPS location and adjustable input of individual factors.

This study investigates how ascending movement is affected by carrying load during a stair‐climbing motion. The methods adopted are based on exercise physiology and fire safety engineering. Experiments with 21 volunteers with mean (SD) age of 27 (4) have been carried out on a stair machine with or without carrying a mass of 8 kg, typical weight of a hand luggage or the average weight of an 8‐months old infant. Oxygen uptake (V˙O2), heart rate (HR), metabolic rate (M), and perceived exertion results showed a decrease in performance in the scenario with additional load. Participants climbed an average of 92 m without carrying a load, in comparison to 84 m when they were carrying it in a 5 minutes task. An average increase of 4% in the V˙O2 and the HR was found in the experiments with the additional mass. The strongest correlating variables observed were M and the vertical distance covered. Differences in perceived exertion occurred after four minutes into the exercise, with higher values in the case with additional load. These results show the need for considering the negative impact of carrying load while designing infrastructures in case of ascending evacuation and while developing evacuation modelling tools.

This laboratory study examined human stair ascending capacity and constraining factors including legs’ local muscle fatigue (LMF) and cardiorespiratory capacity. Twenty-five healthy volunteers, with mean age 35.3 years, maximal oxygen uptake (VO_2max) of 46.7 mL·min⁻¹·kg⁻¹ and maximal heart rate (HR) of 190 bpm, ascended on a stair machine at 60 and 75% (3 min each) and 90% of VO_2max (5 min or until exhaustion). The VO₂, maximal heart rate (HR_max) and electromyography (EMG) of the leg muscles were measured. The average VO_2highest reached 43.9 mL·min⁻¹·kg⁻¹, and HR_highest peaked at 185 bpm at 90% of VO_2max step rate (SR). EMG amplitudes significantly increased at all three levels, p < .05, and median frequencies decreased mostly at 90% of VO_2max SR evidencing leg LMF. Muscle activity interpretation squares were developed and effectively used to observe changes over time, confirming LMF. The combined effects of LMF and cardiorespiratory constraints reduced ascending tolerance and constrained the duration to 4.32 min. Practitioner Summary: To expedite ascending evacuation from high-rise buildings and deep underground structures, it is necessary to consider human physical load. This study investigated the limiting physiological factors and muscle activity rate changes (MARC) used in the muscle activity interpretation squares (MAIS) to evaluate leg local muscle fatigue (LMF). LMF and cardiorespiratory capacity significantly constrain human stair ascending capacities at high, constant step rates.

Working and walking environments often involve standing positions on different surfaces with inclination and different friction. In this study, standing balance of thirteen participants during sudden and irregular external perturbation to calf muscles was investigated. The aim of the study was to evaluate the combined effect of surface inclination and friction on standing balance. The main findings when eyes closed revealed that the standing utilised coefficient of friction (μSUCOF) increased when the surface was inclined for both high and low friction materials. The anterior-posterior torque increased more anteriorly when the surface was inclined toes down and when the surface friction was low. The results indicate that the anterior-posterior torque is a sensitive parameter when evaluating standing balance ability and slip risk. On inclined surface, particularly on the surface with lower friction, the potential slip and fall risk is higher due to the increase of standing utilised coefficient of friction and increased forward turning torque.

Summary: There is reason to believe that factors such as physical exertion and behavioural changes will influence the ascending walking speed and ultimately the possibility of satisfactory evacuation. To study these effects, a 2‐year research project was initiated with the focus on effects of physical exertion on walking speeds, physiological performance and behaviours during long ascending evacuations. Two sets of experiments on human performance during ascending long stairs, with a height of 48 and 109 m, were performed. The results include aspects such as walking speeds, physical exertion (oxygen consumption, heart rates and electromyography data), perceived exertion and behavioural changes, showing that physical work capacity affects walking speeds in case of long ascending evacuation and should be considered while using long ascending evacuation. Analysis of both walking and vertical speeds is recommended because it provides additional insights on the impact of stair configuration on vertical displacement and the importance of not using the same value for walking speed for different stairs because the design of the stairs has an impact. The novel datasets presented in this paper are deemed to provide useful information for fire safety engineers both for assisting fire safety design as well as the calibration of evacuation modelling tools. Copyright © 2016 John Wiley & Sons, Ltd.