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- Halder, Amitava, et al.
(författare)
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Gait Biomechanics While Walking Down an Incline After Exhaustion
- 2023
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Ingår i: Fire Technology. - 1572-8099. ; 59:4, s. 1833-1863
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Tidskriftsartikel (refereegranskat)abstract
- This gait biomechanics study investigated stride length (SL), stride duration (SDN), the peak values of ground reaction forces (GRFspeak), required coefficient of friction (RCOFpeak), leg joints’ angles (anglepeak), angular velocity (angvelx.peak), angular acceleration (angaccx.peak), minimum angle (anglemin.) 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 GRFzpeak. was significantly (p ≤.01) reduced during late stance (LS) phase, however, the antero-posterior GRFypeak. was found to be significantly (p ≤ 0.01) higher. The RCOFpeak. 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’ anglepeak, anglemin., 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.
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- Halder, Amitava, et al.
(författare)
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Limitations of oxygen uptake and leg muscle activity during ascending evacuation in stairways
- 2017
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Ingår i: Applied Ergonomics. - : Elsevier BV. - 0003-6870. ; 66, s. 52-63
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Tidskriftsartikel (refereegranskat)abstract
- Stair ascending performance is critical during evacuation from buildings and underground infrastructures. Healthy subjects performed self-paced ascent in three settings: 13 floor building, 31 floor building, 33 m stationary subway escalator. To investigate leg muscle and cardiorespiratory capacities and how they constrain performance, oxygen uptake (VO2), heart rate (HR) and ascending speed were measured in all three; electromyography (EMG) in the first two. The VO2 and HR ranged from 89-96 % of the maximum capacity reported in the literature. The average highest VO2 and HR ranged from 39-41 mL·kg-1·min-1 and 162-174 b·min-1, respectively. The subjects were able to sustain their initial preferred maximum pace for a short duration, while the average step rate was 92-95 steps·min-1. In average, VO2 reached relatively stable values at ≈37 mL·kg-1·min-1. EMG amplitudes decreased significantly and frequencies were unchanged. Speed reductions indicate that climbing capacity declined in the process of fatigue development. In the two buildings, the reduction of muscle power allowed the subjects to extend their tolerance and complete ascents in the 48 m and 109 m high stairways in 2.9 and 7.8 minutes, respectively. Muscle activity interpretation squares were developed and proved advantageous to observe fatigue and recovery over time.
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- Kuklane, Kalev, et al.
(författare)
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A model to estimate vertical speed of ascending evacuation from maximal work capacity data
- 2016
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Ingår i: Safety Science. - : Elsevier BV. - 0925-7535. ; 89, s. 369-378
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Tidskriftsartikel (refereegranskat)abstract
- This paper describes the development of an ascending evacuation model based on physical work capacity of a selected sample. The model is based on the combination of several field experiments, existing databases and pre-tests that were combined to define initial test conditions in the laboratory environment on a step machine. Maximal oxygen consumption (VO2max) of 13 male and 12 female subjects (data was pooled), was measured, and they climbed at 3 step rates specified according to individual percentage of their maximal aerobic capacity %VO2max) levels. The first nineteen subjects were used for model development and the last six for validation. The paper gives an overview on the collected laboratory data and puts it into relation with the field data from both oxygen consumption and heart rate perspective. The maximum vertical displacement (hvert in m/min) can be calculated according to: hvert = −21.7727 + 0.4024 ∗ VO2max + 0.2658 ∗ %VO2max. The discussion covers limitations and possibilities of the model and suggests the literature and databases that form the basis for practical use of the prediction model. Paper defines the needs for future work and possible information sources to improve the model.
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- Vanggaard, Leif, et al.
(författare)
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The “AVA - organ”
- 2015
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Ingår i: Environmental Ergonomics. ; XVI, s. 114-114
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Konferensbidrag (refereegranskat)
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- Delin, Mattias, et al.
(författare)
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Ascending stair evacuation : walking speed as a function of height
- 2017
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Ingår i: Fire and Materials. - : Wiley. - 0308-0501 .- 1099-1018. ; 41:5, s. 514-534
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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- Eggeling, Jakob, et al.
(författare)
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Validating an advanced smartphone application for thermal advising in cold environments
- 2023
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Ingår i: International Journal of Biometeorology. - 1432-1254. ; 67:12, s. 1957-1964
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Tidskriftsartikel (refereegranskat)abstract
- The ClimApp smartphone application was developed to merge meteorological forecast data with personal information for individualized and improved thermal warning during heat and cold stress and for indoor comfort in buildings. For cold environments, ClimApp predicts the personal thermal stress and strain by the use of the Insulation REQuired model that combines weather and personal physiological data with additional consideration of the Wind Chill index based on the local weather forecast. In this study, we validated the individualized ClimApp index relative to measurements and compared it with the Universal Temperature Climate Index (UTCI). To this aim, 55 participants (27 females) were exposed to at least 1 h in an outdoor environment of 10 °C or below (average 1.4 °C air temperature, 74.9% relative humidity, and 4.7 m/s air velocity) inputting their activity level and clothing insulation as instructed by ClimApp. The UTCI and ClimApp indices were calculated and compared to the participants' perceived thermal sensation. The ClimApp index root mean square deviation (RMSD) was below the standard deviation of the perceived thermal sensation which indicates a valid prediction and the UTCI RMSD was higher than the standard deviation which indicates an invalid prediction. The correlation of ClimApp and UTCI to the perceived thermal sensation was statistically significant for both models.
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