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排序方式: 共有389条查询结果,搜索用时 15 毫秒
1.
The present study investigated the feasibility and reliability of continuous relative phase (CRP) and deviation phase (DP) to assess intersegmental hind limb coordination pattern and coordination variability in rats during walking. Twenty-six adult rats walked at 8 m/min, 12 m/min and 16 m/min while two-dimensional kinematics were recorded. Segment angles and segment angular velocities of the paw, shank and thigh on the left hind-limb were extracted from 15 strides and CRP was calculated for the paw-shank and shank-thigh coupling. The effect of walking speed on the time point average curve of the CRP (ACRP) and DP and on the mean ACRP and mean DP was established by statistical parametric mapping (SPM) and a one-way ANOVA for repeated measures. Absolute and relative reliability were assessed by measurement error and intra-class correlation coefficient. The SPM analysis revealed time dependent differences in the effect of speed. Thus, the CRP of the paw-shank coupling decreased with increasing speed during most of the gait cycle while the CRP of the shank-thigh coupling was decreased during the swing phase. The session-to-session reliability was fair to good for the coordination measure and poor for the variability measure. 相似文献
2.
Here, we seek to determine how compliantly suspended loads could affect the dynamic stability of legged locomotion. We theoretically model the dynamic stability of a human carrying a load using a coupled spring-mass-damper model and an actuated spring-loaded inverted pendulum model, as these models have demonstrated the ability to correctly predict other aspects of locomotion with a load in prior work, such as body forces and energetic cost. We report that minimizing the load suspension natural frequency and damping ratio significantly reduces the stability of the load mass but may slightly improve the body stability of locomotion when compared to a rigidly attached load. These results imply that a highly-compliant load suspension could help stabilize body motion during human, animal, or robot load carriage, but at the cost of a more awkward (less stable) load. 相似文献
3.
Paul DeVita Lars Janshen Patrick Rider Stanislaw Solnik Tibor Hortobgyi 《Journal of biomechanics》2008,41(16):3354-3359
This study tested the hypothesis that skeletal muscles generate more mechanical energy in gait tasks that raise the center of mass compared to the mechanical energy they dissipate in gait tasks that lower the center of mass despite equivalent changes in total mechanical energy. Thirteen adults ran on a 10° decline and incline surface at a constant average velocity. Three-dimensional (3D) joint powers were calculated from ground force and 3D kinematic data using inverse dynamics. Joint work was calculated from the power curves and assumed to be due to skeletal muscle–tendon actuators. External work was calculated from the kinematics of the pelvis through the gait cycle. Incline vs. decline running was characterized with smaller ground forces that operated over longer lever arms causing larger joint torques and work from these torques. Total lower extremity joint work was 28% greater in incline vs. decline running (1.32 vs. −1.03 J/kg m, p<0.001). Total lower extremity joint work comprised 86% and 71% of the total external work in incline (1.53 J/kg m) and decline running (−1.45 J/kg m), which themselves were not significantly different (p<0.180). We conjectured that the larger ground forces in decline vs. incline running caused larger accelerations of all body tissues and initiated a greater energy-dissipating response in these tissues compared to their response in incline running. The runners actively lowered themselves less during decline stance and descended farther as projectiles than they lifted themselves during incline stance and ascended as projectiles. These data indicated that despite larger ground forces in decline running, the reduced displacement during downhill stance phases limited the work done by muscle contraction in decline compared to incline running. 相似文献
4.
Inspired from template models explaining biological locomotory systems and Raibert׳s pioneering legged robots, locomotion can be realized by basic sub-functions: elastic axial leg function, leg swinging and balancing. Combinations of these three can generate different gaits with diverse properties. In this paper we investigate how locomotion sub-functions contribute to stabilize walking at different speeds. Based on this trilogy, we introduce a conceptual model to quantify human locomotion sub-functions in walking. This model can produce stable walking and also predict human locomotion sub-function control during swing phase of walking. Analyzing experimental data based on this modeling shows different control strategies which are employed to increase speed from slow to moderate and moderate to fast gaits. 相似文献
5.
James A. Wanner 《American journal of physical anthropology》1977,47(1):99-102
An analysis of the anterior patellar groove of the human femur shows considerable variation in its medial and lateral spects. The groove itself, measured by the angle it encloses, shows considerably less variation than its individual components. The suggested functional relationship between bicondylar angle and lateral elevation of the patellar groove does not obtain for this sample. 相似文献
6.
J. T. Watson R. E. Ritzmann 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1997,182(1):23-33
We have combined kinematic and electromyogram (EMG) analysis of running Blaberus discoidalis to examine how middle and hind leg kinematics vary with running speed and how the fast depressor coxa (Df) and fast extensor
tibia (FETi) motor neurons affect kinematic parameters. In the range 2.5–10 Hz, B. discoidalis increases step frequency by altering the joint velocity and by reducing the time required for the transition from flexion
to extension. For both Df and FETi the timing of recruitment coincides with the maximal frequency seen for the respective
slow motor neurons. Df is first recruited at the beginning of coxa-femur (CF) extension. FETi is recruited in the latter half
of femur-tibia (FT) extension during stance. Single muscle potentials produced by these fast motor neurons do not have pronounced
effects on joint angular velocity during running. The transition from CF flexion to extension was abbreviated in those cycles
with a Df potential occurring during the transition. One effect of Df activity during running may be to phase shift the beginning
of joint extension so that the transition is sharpened. FETi is associated with greater FT extension at higher running speeds
and may be necessary to overcome high joint torques at extended FT joint angles.
Accepted: 24 May 1997 相似文献
7.
We studied micro-benthic copepods and cladocerans in the bottom substrates of 12 lakes in the Bol’shezemel’skaya tundra in
North-East European Russia during the summer. About 30 species of Cladocera and 28 species and subspecies of Copepoda were
found. The majority of the micro-crustaceans are palaearctic or northern palaearctic. But the harpacticoid fauna of the western
part of the studied region had specific European features, and three species of the harpacticoid fauna in the eastern part
of the region were Siberian. It is therefore a boundary territory for two zoogeographical regions, the arctic and subarctic
zones. Acidophilic (Arcticocamptus arcticus (Lilljeborg 1902)) and halophilic (Microsetella norvegica (Boeck 1864)) harpacticoid species were found in the lakes of the eastern part of Bol’shezemel’skaya tundra. On basis of
their way of locomotion we distinguished five ecological groups and on basis of their feeding habits four ecological groups
of micro-crustaceans. Groups with a similar way of locomotion were likely distributed over the studied water bodies. Habitat
(inshore versus offshore), substrate particle size and substrate hardness were of paramount importance for the species distribution. 相似文献
8.
In this study, we examined Spatial–temporal gait stride parameters, lower extremity joint angles, ground reaction forces (GRF) components, and electromyographic activation patterns of 10 healthy elderly individuals (70 ± 6 years) walking in water and on land and compared them to a reference group of 10 younger adults (29 ± 6 years). They all walked at self-selected comfortable speeds both on land and while immersed in water at the Xiphoid process level. Concerning the elderly individuals, the main significant differences observed were that they presented shorter stride length, slower speed, lower GRF values, higher horizontal impulses, smaller knee range of motion, lower ankle dorsiflexion, and more knee flexion at the stride’s initial contact in water than on land. Concerning the comparison between elderly individuals and adults, elderly individuals walked significantly slower on land than adults but both groups presented the same speed walking in water. In water, elderly individuals presented significantly shorter stride length, lower stride duration, and higher stance period duration than younger adults. That is, elderly individuals’ adaptations to walking in water differ from those in the younger age group. This fact should be considered when prescribing rehabilitation or fitness programs for these populations. 相似文献
9.
《Geobios》2014,47(1-2):45-55
Seven previous proposals of aptychus (sensu stricto) function are reviewed: lower mandible, protection of gonads of females, protective operculum, ballasting, flushing benthic prey, filtering microfauna and pump for jet propulsion. An eighth is introduced: aptychi functioned to actively stabilize the rocking produced by the pulsating jet during forward foraging and backward swimming. Experiments with in-air models suggest that planispiral ammonites could lower their aperture by the forward shift of a mobile cephalic complex. In the experiments, the ventral part of the peristome is lowered from the lateral resting (neutral) position by the added “ballast” of a relatively thin Laevaptychus to an angle < 25° from horizontal with adequate stability to withstand the counter-force produced by the jet of the recurved hyponome. However, of the shell forms tested, only brevidomes with thick aptychi, e.g., the Upper Jurassic Aspidoceratidae with Laevaptychus and average whorl expansion rates, were stable enough to swim forward by jet propulsion at about Nautilus speed (∼ 25 cm/s). We propose that aptychus function most commonly combined feeding (jaw, flushing, filtering) with protection (operculum), and, more rarely, with locomotion (ballast, pump, diving and stabilizing plane). Aptychi may thus have been multi-functional. 相似文献
10.
Dionisios Youlatos 《Primates; journal of primatology》1998,39(4):449-457
Recent studies on the positional behavior of primates reveal that significant seasonal variation occurs in both locomotion
and postures that is related to changes in diet and foraging techniques. Howling monkeys (genusAlouatta), which also have a seasonally varied diet, are predicted to have correspondingly varied positional behaviors. Two groups
of red howling monkeys were studied in a primary rain forest in French Guinana during the dry and wet seasons. During the
dry season, when howler diet is based mainly on leaves, howlers traveled more frequently by quadrupedal walking on large supports,
a mode of progression that is probably inexpensive energetically and relatively stable. During feeding, quadrupedal and tripedal
stand contributed considerably, a posture probably associated with the equal distribution of leaves within a tree crown. In
contrast, during the wet season, when fruit was abundant, howlers fed very frequently by sitting on large supports, probably
because fruit consumption required more time for special manipulation. However, most seasonal changes in feeding postures,
and in travel and feeding locomotion, were difficult to associate directly with dietary shifts. These behavioral changes may
be more highly correlated with slight modifications in microhabitat use (horizontal and vertical daily ranges, similar and
alternative arboreal pathways) that are not considered in this paper. 相似文献