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Dynamic strategies and motor control of human walking
789
Abstracts-International Societyof BiomechanicsXIII Congress1991 DYNAMIC LOADINGS DURING WALKING AND LOAD CARRYING Erlk B. Simonscn, Poul Dyhre-Paulsen,Michael Voigt, Per Aagaaul and GiselaSjegaard. Depanment of Anatomy C. and Institute of Neurophysiotbgy, Occupati&tal Health, Denmark.
University of Copenhagen & National Institute of
The primary purpose of this study was to examine bone on bone forcesduring walking and load carrying. Seven healthy male subjectswalked acrossa force platform while they were filmed at 200 frames per second.Beside unloaded walking both symmetricaland asymmeuicalload carryingwere performed at 10 kg and 20 kg total load carriedin the hands. At the same time EMG from the erector spinaemuscleand five leg muscleswere recorded. By use of muscle models and the free body segmentmethod bone on bone forces wem calculateddynamically at the ankle, the knee and the hip joint. In addition disc compmssionforces at L4/L5 were computed. Between unloaded walking and 20 kg symmetrical load carrying the averagepeak bone on bone forces at the hip joint increasedfrom 7.0 times body weight (BW) to 9.1 BW. The correspondingvaluesat the knee joint were 5.8 and 7.4 BW while at the ankle joint the values were 5.3 and 6.9 BW, respectively.No consistentdifferenceswere seenbetween asymmetricaland symmetrical loading. Averagepeak disc compressionforce at LA/L.5 increasedfrom 3484 N during unloaded walking to 4514 N during 20 kg symmetricalload carrying. The two subjectswho produced the lowest forces at the ankle joint showed the highest forcesat the hip joint and at L&L5 It is concludedthat dynamic calculationsof peak bone on bone forces revealedmuch higher valuescomparedto a static approach,which would only predict forces proportional to the massof the segmentsabovethe actualjoint plus the load carried.
DYNAMIC
STRATEGIES
AND MOTOR
CONTROL
OF HUMAN
WALKING
Erik B. Simonsen,Pot11Dyhre-Pot&en, Michael Voigt, Nils Fallentin and Pii Bojsen-MeIler. Anatomy Department C. and Institute of Neurophysiology, Institute of Occupational Health, Denmark.
University of Copenhagen & National
The purpose of this study was to explain some of the reasonswhy the shape and polarity of net joint moments differ between individuals during human walking. Sevenhealthy male subjectswalked acrossa force platform while they were filmed at 200 frames per second.At the same time EMG was recordedfrom five leg muscles.In addition treadmill walking was performed at 4.5 km/hour. Net joint momentx were calculatedby standardprocedures.Instsntaneousmuscle-tendonlength and internal moment arms were computed by musclemodels. EMG signalsfrom teu repmsentativestep cycleson the tmuhill were digitally mctified, averagedand normal&d to the step cycle. Two of the subjectsshowed dorsi flexor momentsjust after heel strike while the other five subjectsshowed plantar flexor dominance. It was revealedthat the ground reaction forcesproduced an external moment which could explain the net ankle joint moment. When dorsi flexor dominance prevailed the ground reactiou vector passedbehind the ankle joint and vice versa.The averagedEMG mcordmgs appearedto be very similar between all sevensubjectsindicating that the subjectsused a basic motor pattern, which is probably inherited. It is therefore suggestedthat individual diff&nces in joint moments are due to small kinematic differencesin how the foot is put to the ground.
FACTORS RELATED TO REARFOOT KINEMATICS DURING K Simpson Biomechanics Laboratory, Dept. Exercise Scieoce, Univ. Georgia,
A RAPID
BRAKING
MOVEMENT
Athens, USA
The purpose of the study was to ident@ morphological, movement and biomechanical factors related to the maximum rear-foot velocity (MRV) and the corresponding time to h4RV (tMRV) during a lateral braking movement. Seven male skilled tennis players performed 24 trials of sideward shuffle movements at 60 to 100% maximum velocity. A rear view of the right leg landing onto a force platform (500 Hz) during the braking step was filmed (200 fps). Except for structural inversion, other morphological variables as well as the movement characteristic variables were not highly correlated (r =.21-.37). The correlations between MRV and the biomechanical parameters were all significant (p c .OOOl)except for the impulse parameters. Gradient parameters demonstrated the greatest correlations for the biomechanical parameters. The tMRV correlations generally were less than the MRV correlations, ranging from .@I to .37. The left foot is on the ground during the right foot landing phase, therefore the performer can use a variety of movement strategies to reduce the horizontal momentum of the body, which accounts for the low correlations for the movement velocity and biomechanical impulse variables with MRV. Because the maximum gradient parameter values and their corresponding temporal parameters were the most sensitive to changes in MRV, these variables are useful for evah&ng rearfoot motion.
Abstracts-International Societyof BiomechanicsXIII Congress1991 DYNAMIC LOADINGS DURING WALKING AND LOAD CARRYING Erlk B. Simonscn, Poul Dyhre-Paulsen,Michael Voigt, Per Aagaaul and GiselaSjegaard. Depanment of Anatomy C. and Institute of Neurophysiotbgy, Occupati&tal Health, Denmark.
University of Copenhagen & National Institute of
The primary purpose of this study was to examine bone on bone forcesduring walking and load carrying. Seven healthy male subjectswalked acrossa force platform while they were filmed at 200 frames per second.Beside unloaded walking both symmetricaland asymmeuicalload carryingwere performed at 10 kg and 20 kg total load carriedin the hands. At the same time EMG from the erector spinaemuscleand five leg muscleswere recorded. By use of muscle models and the free body segmentmethod bone on bone forces wem calculateddynamically at the ankle, the knee and the hip joint. In addition disc compmssionforces at L4/L5 were computed. Between unloaded walking and 20 kg symmetrical load carrying the averagepeak bone on bone forces at the hip joint increasedfrom 7.0 times body weight (BW) to 9.1 BW. The correspondingvaluesat the knee joint were 5.8 and 7.4 BW while at the ankle joint the values were 5.3 and 6.9 BW, respectively.No consistentdifferenceswere seenbetween asymmetricaland symmetrical loading. Averagepeak disc compressionforce at LA/L.5 increasedfrom 3484 N during unloaded walking to 4514 N during 20 kg symmetricalload carrying. The two subjectswho produced the lowest forces at the ankle joint showed the highest forcesat the hip joint and at L&L5 It is concludedthat dynamic calculationsof peak bone on bone forces revealedmuch higher valuescomparedto a static approach,which would only predict forces proportional to the massof the segmentsabovethe actualjoint plus the load carried.
DYNAMIC
STRATEGIES
AND MOTOR
CONTROL
OF HUMAN
WALKING
Erik B. Simonsen,Pot11Dyhre-Pot&en, Michael Voigt, Nils Fallentin and Pii Bojsen-MeIler. Anatomy Department C. and Institute of Neurophysiology, Institute of Occupational Health, Denmark.
University of Copenhagen & National
The purpose of this study was to explain some of the reasonswhy the shape and polarity of net joint moments differ between individuals during human walking. Sevenhealthy male subjectswalked acrossa force platform while they were filmed at 200 frames per second.At the same time EMG was recordedfrom five leg muscles.In addition treadmill walking was performed at 4.5 km/hour. Net joint momentx were calculatedby standardprocedures.Instsntaneousmuscle-tendonlength and internal moment arms were computed by musclemodels. EMG signalsfrom teu repmsentativestep cycleson the tmuhill were digitally mctified, averagedand normal&d to the step cycle. Two of the subjectsshowed dorsi flexor momentsjust after heel strike while the other five subjectsshowed plantar flexor dominance. It was revealedthat the ground reaction forcesproduced an external moment which could explain the net ankle joint moment. When dorsi flexor dominance prevailed the ground reactiou vector passedbehind the ankle joint and vice versa.The averagedEMG mcordmgs appearedto be very similar between all sevensubjectsindicating that the subjectsused a basic motor pattern, which is probably inherited. It is therefore suggestedthat individual diff&nces in joint moments are due to small kinematic differencesin how the foot is put to the ground.
FACTORS RELATED TO REARFOOT KINEMATICS DURING K Simpson Biomechanics Laboratory, Dept. Exercise Scieoce, Univ. Georgia,
A RAPID
BRAKING
MOVEMENT
Athens, USA
The purpose of the study was to ident@ morphological, movement and biomechanical factors related to the maximum rear-foot velocity (MRV) and the corresponding time to h4RV (tMRV) during a lateral braking movement. Seven male skilled tennis players performed 24 trials of sideward shuffle movements at 60 to 100% maximum velocity. A rear view of the right leg landing onto a force platform (500 Hz) during the braking step was filmed (200 fps). Except for structural inversion, other morphological variables as well as the movement characteristic variables were not highly correlated (r =.21-.37). The correlations between MRV and the biomechanical parameters were all significant (p c .OOOl)except for the impulse parameters. Gradient parameters demonstrated the greatest correlations for the biomechanical parameters. The tMRV correlations generally were less than the MRV correlations, ranging from .@I to .37. The left foot is on the ground during the right foot landing phase, therefore the performer can use a variety of movement strategies to reduce the horizontal momentum of the body, which accounts for the low correlations for the movement velocity and biomechanical impulse variables with MRV. Because the maximum gradient parameter values and their corresponding temporal parameters were the most sensitive to changes in MRV, these variables are useful for evah&ng rearfoot motion.