| 1. |
- Halder, Amitava, et al.
(författare)
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Effects of leg fatigue due to exhaustive stair climbing on gait biomechanics while walking up a 10˚ incline – implications for evacuation and work safety
- 2021
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Ingår i: Fire Safety Journal. - : Elsevier BV. - 0379-7112.
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Tidskriftsartikel (refereegranskat)abstract
- This biomechanics study explored stride length (SL), duration (SDN), and gait ground reaction forces (GRFspeak), required coefficient of friction (RCOFpeak), joint angle (anglepeak, anglemin), angular velocities (angvelx peak), angular accelerations (angaccx peak), muscle electromyography (EMG) during the dominant leg stance phase (SP) following an exhaustive stair ascent for evacuation. Data were collected by a three-dimensional motion capture system synchronized with EMG and force plate when walking upwards on a 10° inclined walkway.The significantly (p≤0.05) decreased EMG median frequencies of tibialis anterior during early (ES) and late stance (LS) phases, and vastus lateralis muscles during LS are the evidence of leg local muscle fatigue (LMF). The perpendicular and longitudinal shear GRFspeaks were significantly reduced during ES (p≤0.05) and LS (p≤0.01), respectively. The post-fatigue SP, SL, and SDN were significantly (p<0.05) shorter. Specially, the foot anglemins, ankle anglepeaks, and relevant angvelx peaks, and angaccx peaks significantly (p≤0.05) decreased in post-fatigue trials. The post-fatigue RCOFpeaks were found significantly (p≤0.01) lower during LS phase. Thus, whole body exhaustion and leg LMF constrained the gait kinetics and kinematics when walking upwards indicating a cautious gait associated with the risks of falls, accidents, which can hinder the process of evacuation and work safety on slopes.
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| 2. |
- 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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| 3. |
- Halder, Amitava, et al.
(författare)
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Physiological Capacity During Simulated Stair Climbing Evacuation at Maximum Speed Until Exhaustion
- 2020
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Ingår i: Fire Technology. - : Springer Science and Business Media LLC. - 0015-2684 .- 1572-8099.
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Tidskriftsartikel (refereegranskat)abstract
- Stair-ascending at maximum ability is required during emergency evacuations to reach a safe refuge from deep underground structures. We hypothesized that an ascent can last maximum 5 min at the individual’s maximum step rate (SR), and oxygen uptake (V˙O2) would not reach a stable state. This study explored stair-ascending endurance and some physiological constraints of performance. Eighteen healthy volunteers with mean (standard deviation, SD) age 26.7 (4.0) years, height 172.2 (10.7) cm, weight 68.0 (11.3) kg, BSA 1.8 (0.2) m−2, V˙O2max 48.5 (5.4) mL min−1 kg−1, and HRmax 192 (9) b min−1 ascended on a stair machine at a SR equivalent to their 100% V˙O2max. The mean (SD) ascending duration was 3.47 (1.18) min, supporting the hypothesis. The calculated vertical height covered was 85.5 (32.1) m. The V˙O2highest reached 44.8 (7.3) mL min−1 kg−1, which was 92.3 (9.7)% of V˙O2max when the HRhighest peaked at 174 (11) b min−1. However, the mean V˙O2 reached a relatively steady state after the sharp rise. The post-ascent blood lactate, respiratory exchange ratio, and perceived exertion values recorded were high, 14.4 (4.0) mmol l−1, 1.20 (0.09), and 18.2 (0.7), respectively, indicated that exhaustion was reached. The ascending SR rate was above the lactate threshold; therefore, the attainment of V˙O2 steady state was slowly reached. EMG amplitudes of four major leg muscles increased and the median frequencies of two muscles decreased significantly (p < .01) indicating local muscle fatigue (LMF). Leg LMF and hyperventilation resulted in speedy exhaustion leading to termination. These results infer that stair ascending at maximum ability (122 steps min−1) is possible to sustain 2–6 min. These overall results offer useful and vital information to consider when designing underground emergency evacuation facilities
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