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6.19 Adaptations of walking pattern on a compliant surface
Chapter 6. Multi-segmental coordination
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responses of superficial and deep trunk muscles, and compromised control when respiration increases.
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Adaptations of walking pattern on a compliant surface
M.J. MacLellan, A.E. Patla. University of Waterloo, Waterloo,
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Ontario, Canada Influence of voluntary arm movement during locomotion on stability margin
M.G.A. Ishac, A.E. Patla. Gait & Posture Lab, Department of Kinesiology, University of Waterloo, Waterloo, Ontario, Canada Introduction: Voluntary arm movement during standing resulted
in both regulation of total body centre of mass (CoM) and joint stabilization [1]. This experiment investigates the effect of mediolateral arm movement during locomotion on stability margin. Method: Three AMTI force plates, two OptoTrak camera banks, and 23 markers (5th metatarsals, heels, reals., femur heads, gts, iliac crests, ghs, olecranons, styloid, ear lobes, clavicles and xyphoid) were used to collect data at 60 (Hz). Participants were instructed to raise left arm (LA) or right arm (RA) to shoulder level upon seeing an indicator light during walking. The light indicator is randomly triggered by the participant heel contact (LH or RH) with the first force plate. 6 young adults participated and 120 randomised trials (5 s each) were collected per each participant; 30 for LH (10 LA, 10 NA, 10 RA), 30 for RH (10 LA, 10 NA, 10 RA) and 60 catch trials. A 13-segment 3D model is used to estimate the location of the CoM within the base of support
(BoS). Results: The CoM distance to the edge of the BoS in the perturbed step showed an interaction effect between the stance limb (LH, RH) and arm (LA, RA) [F(2,10) 5.62, p 0.023]. No such interaction in the subsequent step was found. Discussion: The distance margin increased in the LH_LA and RH_RA conditions. This shows that foot placement is modified to minimize the danger to stability.
References [1] Patla, AE, Ishac, MG, Winter, DA, Experimental Brain Research, 2002; 143:318 327.
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Postural organization of cascade juggling
Introduction: It is unknown how humans adapt to locomotion on unstable surfaces such as a soggy field. This study used foam to simulate an unstable walking surface and locomotion was analyzed. Methods: Participants (N 5) were asked to walk on a travel path 5 m long, 0.91 m wide. Whole body kinematics and EMG activity in 10 lower limb muscles were recorded. Participants engaged in 20 walking trials: 10 trials on flat ground then 10 trials walking on the medium density piece of foam. During the foam trials, locomotion was initiated on stable ground and the second foot contact was on the foam surface. Results: Evaluation of full body center of mass (CoM) revealed that initial body CoM did not differ in the medio-lateral direction (p 0.188) or during locomotion (p 0.132). There was a significant condition effect in the vertical direction (p < 0.05). Examining time to peak CoM suggests that there was a phase shift in the vertical CoM trajectory (p <0.005). Step width (p 0.717) and step width variance (p 0.235) did not differ in the foam condition. There was a significant interaction effect in step length (p < 0.002) suggesting that step length is successively shorter while walking on foam. Step time was also significantly longer while walking on the foam (p < 0.02). Discussion and Conclusion: The foam surface may have caused differences in vertical CoM trajectory due to compression of the foam during walking which suggests that humans do not control vertical CoM while stepping on a compliant surface. Step characteristics may change to increase base of support while walking on the foam surface. This study was funded with a grant from NSERC Canada.
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Active control of knee flexion during the step off an unexpected compliant surface to maintain similar toe clearance
D.S. Marigold, A.E. Patla. Gait and Posture Lab, Department of Kinesiology, University of Waterloo, Waterloo, Canada
D. Leroy, R. Thouvarecq, J. Vittecocq, N. Germaine. CETAPS EA
Introduction: Previous studies have investigated hopping on a
3832, University of Rouen; GRHAL, Hospital of Rouen, France
compliant surface [1]. The purpose of this study was to examine the scaling behavior of lower limb dynamics during the step off an unexpected compliant surface during locomotion. Methods: Eight participants (age 24.5±1.9 years) walked along a walkway and stepped on an unexpected compliant surface in the middle of the travel path with their left (i.e. perturbed) limb. There were three different types of surface compliances (i.e. stiffness) and participants experienced either no compliant surface or one of three compliant surfaces for a given trial. Perturbed limb knee angle and toe clearance (vertical distance between ground and toe marker) over the obstacle created by the depression of the compliant surface were determined. Results: Toe clearance did not change for any of the compliant surfaces or the control condition (range 6.67 7.37cm, p 0.090). However, perturbed limb knee angle was significantly more flexed as surface compliance increased (i.e. surface depressed to a greater extent) after toe-off from the compliant surface apparatus (range 115.8 123.4 °, p <0.0001). Discussion and Conclusion: The perturbed limb knee was flexed to a greater extent as surface compliance increased in order to maintain similar toe clearance over the obstacle created by the depression of the compliant surface suggesting active control of the knee.
Introduction: Juggling is constrained by the spatial limits of the
objects in the air [1]. Cascade juggling is a complex, cyclic activity, involving three balls or more, in which the hands move along more or less elliptical trajectories. A ball cycle corresponds to the time between a throw of a ball by the right hand and the catch of that ball by the same hand [2]. The aim of this study was to examine the jugglers postural coordination according to these rhythmical constraints. Methods: Experts are defined as being able to juggle with 5 balls or more. Apprentices are only able to juggle with three balls but during more than one minute. The three-balls cascade juggling and the interlimbs coordination of 5 experts and of 5 apprentices were compared using an optoelectronic system. All data were normalized to a ball cycle (100%). Results: Since the average of the vertical ball trajectory is not different between experts and apprentices, experts present a rhythmical lateral oscillation of their trunk, which is not seen with the apprentices. Discussion: Juggling regularly for a long time (more than 5 years) seems to occur not only a manual organization but also an intersegmentary coordination.
References [1] Beek PJ, Turvey MT. Temporal Patterning in Cascade Juggling. J Exp Psy: Hum Perc & Perf 1992; 18:934 947. [2] Post AA, Daffertshofer A, Beek PJ. Principal components in threeball cascade juggling. Biol Cyb 1999; 82:143 152.
References [1] Moritz CT, Farley CT. Passive dynamics change leg mechanics for an unexpected surface during human hopping. J Appl Physiol 2004; 97:1313 1322.
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responses of superficial and deep trunk muscles, and compromised control when respiration increases.
I
•
Adaptations of walking pattern on a compliant surface
M.J. MacLellan, A.E. Patla. University of Waterloo, Waterloo,
I•
Ontario, Canada Influence of voluntary arm movement during locomotion on stability margin
M.G.A. Ishac, A.E. Patla. Gait & Posture Lab, Department of Kinesiology, University of Waterloo, Waterloo, Ontario, Canada Introduction: Voluntary arm movement during standing resulted
in both regulation of total body centre of mass (CoM) and joint stabilization [1]. This experiment investigates the effect of mediolateral arm movement during locomotion on stability margin. Method: Three AMTI force plates, two OptoTrak camera banks, and 23 markers (5th metatarsals, heels, reals., femur heads, gts, iliac crests, ghs, olecranons, styloid, ear lobes, clavicles and xyphoid) were used to collect data at 60 (Hz). Participants were instructed to raise left arm (LA) or right arm (RA) to shoulder level upon seeing an indicator light during walking. The light indicator is randomly triggered by the participant heel contact (LH or RH) with the first force plate. 6 young adults participated and 120 randomised trials (5 s each) were collected per each participant; 30 for LH (10 LA, 10 NA, 10 RA), 30 for RH (10 LA, 10 NA, 10 RA) and 60 catch trials. A 13-segment 3D model is used to estimate the location of the CoM within the base of support
(BoS). Results: The CoM distance to the edge of the BoS in the perturbed step showed an interaction effect between the stance limb (LH, RH) and arm (LA, RA) [F(2,10) 5.62, p 0.023]. No such interaction in the subsequent step was found. Discussion: The distance margin increased in the LH_LA and RH_RA conditions. This shows that foot placement is modified to minimize the danger to stability.
References [1] Patla, AE, Ishac, MG, Winter, DA, Experimental Brain Research, 2002; 143:318 327.
I~
Postural organization of cascade juggling
Introduction: It is unknown how humans adapt to locomotion on unstable surfaces such as a soggy field. This study used foam to simulate an unstable walking surface and locomotion was analyzed. Methods: Participants (N 5) were asked to walk on a travel path 5 m long, 0.91 m wide. Whole body kinematics and EMG activity in 10 lower limb muscles were recorded. Participants engaged in 20 walking trials: 10 trials on flat ground then 10 trials walking on the medium density piece of foam. During the foam trials, locomotion was initiated on stable ground and the second foot contact was on the foam surface. Results: Evaluation of full body center of mass (CoM) revealed that initial body CoM did not differ in the medio-lateral direction (p 0.188) or during locomotion (p 0.132). There was a significant condition effect in the vertical direction (p < 0.05). Examining time to peak CoM suggests that there was a phase shift in the vertical CoM trajectory (p <0.005). Step width (p 0.717) and step width variance (p 0.235) did not differ in the foam condition. There was a significant interaction effect in step length (p < 0.002) suggesting that step length is successively shorter while walking on foam. Step time was also significantly longer while walking on the foam (p < 0.02). Discussion and Conclusion: The foam surface may have caused differences in vertical CoM trajectory due to compression of the foam during walking which suggests that humans do not control vertical CoM while stepping on a compliant surface. Step characteristics may change to increase base of support while walking on the foam surface. This study was funded with a grant from NSERC Canada.
I•
Active control of knee flexion during the step off an unexpected compliant surface to maintain similar toe clearance
D.S. Marigold, A.E. Patla. Gait and Posture Lab, Department of Kinesiology, University of Waterloo, Waterloo, Canada
D. Leroy, R. Thouvarecq, J. Vittecocq, N. Germaine. CETAPS EA
Introduction: Previous studies have investigated hopping on a
3832, University of Rouen; GRHAL, Hospital of Rouen, France
compliant surface [1]. The purpose of this study was to examine the scaling behavior of lower limb dynamics during the step off an unexpected compliant surface during locomotion. Methods: Eight participants (age 24.5±1.9 years) walked along a walkway and stepped on an unexpected compliant surface in the middle of the travel path with their left (i.e. perturbed) limb. There were three different types of surface compliances (i.e. stiffness) and participants experienced either no compliant surface or one of three compliant surfaces for a given trial. Perturbed limb knee angle and toe clearance (vertical distance between ground and toe marker) over the obstacle created by the depression of the compliant surface were determined. Results: Toe clearance did not change for any of the compliant surfaces or the control condition (range 6.67 7.37cm, p 0.090). However, perturbed limb knee angle was significantly more flexed as surface compliance increased (i.e. surface depressed to a greater extent) after toe-off from the compliant surface apparatus (range 115.8 123.4 °, p <0.0001). Discussion and Conclusion: The perturbed limb knee was flexed to a greater extent as surface compliance increased in order to maintain similar toe clearance over the obstacle created by the depression of the compliant surface suggesting active control of the knee.
Introduction: Juggling is constrained by the spatial limits of the
objects in the air [1]. Cascade juggling is a complex, cyclic activity, involving three balls or more, in which the hands move along more or less elliptical trajectories. A ball cycle corresponds to the time between a throw of a ball by the right hand and the catch of that ball by the same hand [2]. The aim of this study was to examine the jugglers postural coordination according to these rhythmical constraints. Methods: Experts are defined as being able to juggle with 5 balls or more. Apprentices are only able to juggle with three balls but during more than one minute. The three-balls cascade juggling and the interlimbs coordination of 5 experts and of 5 apprentices were compared using an optoelectronic system. All data were normalized to a ball cycle (100%). Results: Since the average of the vertical ball trajectory is not different between experts and apprentices, experts present a rhythmical lateral oscillation of their trunk, which is not seen with the apprentices. Discussion: Juggling regularly for a long time (more than 5 years) seems to occur not only a manual organization but also an intersegmentary coordination.
References [1] Beek PJ, Turvey MT. Temporal Patterning in Cascade Juggling. J Exp Psy: Hum Perc & Perf 1992; 18:934 947. [2] Post AA, Daffertshofer A, Beek PJ. Principal components in threeball cascade juggling. Biol Cyb 1999; 82:143 152.
References [1] Moritz CT, Farley CT. Passive dynamics change leg mechanics for an unexpected surface during human hopping. J Appl Physiol 2004; 97:1313 1322.