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Exercise-related adaptation in geometry and mechanical properties of immature rat tibia and vertebra
1077
Abstracts-International Society of BiomechanicsXII Congress1989 USE OF SURFACE AND FINE WIRE ELECTROMYOGRAPHY EXTREMITY FLEXORS DURING CYCLING
IN THE
STUDY
OF LOWER
Mimi Ryan, Robert J. Gregor, Bitte Healy* Department of Kinesiology,UCLA,Los Angeles,CA 90024-1568 and Centinela Hospital,Inglewood,CA 90302* Although either surfaceor indwelling electrodesare commonly used to obtain the electrical activity of muscles (EMG), reports indicate that surface electrodes have been employed exclusively in the collection of lower extremity EMG during cycling. Recent cycling surfaceEMG data reported by Ryan et al. (1988) indicated that although EMG patterns for the extensors were relatively immutable, the flexors showed a great deal of variability. To further investigate this variability, knee flexor activity patterns were monitored using both fine wire and surface electrodes to compare patterns obtained from each preparation with those reported in the literature. Five recreational cyclists rode a racing bicycle at 90 RPM (250W). Fine wire electrodes (50 urn) were inserted into the muscle bellies of long head of biceps femoris (BF), semitendinosus (ST), and distal semimembranosus(SM). Bipolar pairs of silver-silverchloride surfaceelectrodeswere placed on either sideof the insertion of the indwelling electrodes.Data were sampled at 2KHz, stored and processedon an Amiga 2000 microcomputer. A comparison between surface and fine wire EMG collected from the samemuscle shows that relative timing of principal EMG activity from each electrode pair was approximately the same; however, the burst duration from the surface electrodesappearedlonger. Both preparations of BF and SM recorded a small burst of EMG just prior to top dead center. The ST fine wire preparation did not record this small burst while the surfaceelectrode preparation did indicating possible crosstalkin this preparation. In general, EMG collected in this study suggested that activation patterns obtained using surface electrodes provide sufficient and reliable representationof muscle involvement during the cycling task. However, more detailed analysesat low levels of activity may require fine wire preparations.
SEPARATION ANALYSIS.
Dunedin,
OF THE IMPACT AND ACTIVE COMPONENTS OF DROP JUMPS USING FOURIER Ross, H. Sanders, and Barry, D. Wilson. University of Otago,
NZ.
The vertical
ground reaction forces of a jump following landing from a height may be regarded as a superposition of an impact component comprising high frequency waveforms and an active component comprising low frequency waveforms. An attempt was made to separate these components utilising the fact that the high frequency waveforms associated with the impact decay during the period of contact with the force platform. A Fourier transform was applied to the force data. An inverse transform was then performed for each frequency harmonic cutoff up to the Nyquist limit,. Root mean square (RMS) errors of each reconstructed function with respect to the original force function were calculated for each decile of the contact period. Selection of the appropriate harmonic cutoff to separate the impact and active components was based on the magnitude of the RMS errors for deciles 6,l and 8. Using this technique it was found that the impact component resembled a damped oscillation about the zero line in keeping with that expected. It was concluded that the Fourier technique with RMS error of deciles 6,7 and 8 being used as the criterion for the frequency cutoff was a satisfactory means of separating the active and impact components of a drop jump to permit independent analysis of these.
EXERCISE-RELATED ADAPTATION IN GEOMETRY PROPERTIES OF IMMATURE RAT TIBIA AND VERTEBRA
AND
MECHANICAL
George J. Salem, Kung-Chia Li, Ronald F. Zemicke, R. JamesBarnard Depamnent of Kinesiology, UCLA, Los Angeles, CA 90024-1568 USA To quantify the exercise-relatedresponsesof tibia and vertebra of rapidly-growing animals, 20 female Sprague-Dawley rats (8 wks, 1.50-170 g) were progressively (10 wks) trained (75-80% maximum aerobic capacity) on a motor-driven treadmill 5 d/wk until they were running 1.8 km/hr at a lo-12% grade for 1 hr/d. Twenty age-matched rats served as controls. Using a servocontrolled electromechanicaltesting system,3 point-bending teststo failure were conducted with tibia loaded in a medial to lateral direction at midlength; vertebral bodies were compressedto 50% of their initial height at a 50% /s strain rate. Tibial length, periosteal circumference, linear load, maximum load, energy to maximum load, and energy to failure decreased significantly in the exercised animals. Significant differencesin vertebral-body geomehy and mechanicalproperties were not found. Differential loading or differences in load responseof cortical and trabecular bone may account for the exercise-related adaptations.
Abstracts-International Society of BiomechanicsXII Congress1989 USE OF SURFACE AND FINE WIRE ELECTROMYOGRAPHY EXTREMITY FLEXORS DURING CYCLING
IN THE
STUDY
OF LOWER
Mimi Ryan, Robert J. Gregor, Bitte Healy* Department of Kinesiology,UCLA,Los Angeles,CA 90024-1568 and Centinela Hospital,Inglewood,CA 90302* Although either surfaceor indwelling electrodesare commonly used to obtain the electrical activity of muscles (EMG), reports indicate that surface electrodes have been employed exclusively in the collection of lower extremity EMG during cycling. Recent cycling surfaceEMG data reported by Ryan et al. (1988) indicated that although EMG patterns for the extensors were relatively immutable, the flexors showed a great deal of variability. To further investigate this variability, knee flexor activity patterns were monitored using both fine wire and surface electrodes to compare patterns obtained from each preparation with those reported in the literature. Five recreational cyclists rode a racing bicycle at 90 RPM (250W). Fine wire electrodes (50 urn) were inserted into the muscle bellies of long head of biceps femoris (BF), semitendinosus (ST), and distal semimembranosus(SM). Bipolar pairs of silver-silverchloride surfaceelectrodeswere placed on either sideof the insertion of the indwelling electrodes.Data were sampled at 2KHz, stored and processedon an Amiga 2000 microcomputer. A comparison between surface and fine wire EMG collected from the samemuscle shows that relative timing of principal EMG activity from each electrode pair was approximately the same; however, the burst duration from the surface electrodesappearedlonger. Both preparations of BF and SM recorded a small burst of EMG just prior to top dead center. The ST fine wire preparation did not record this small burst while the surfaceelectrode preparation did indicating possible crosstalkin this preparation. In general, EMG collected in this study suggested that activation patterns obtained using surface electrodes provide sufficient and reliable representationof muscle involvement during the cycling task. However, more detailed analysesat low levels of activity may require fine wire preparations.
SEPARATION ANALYSIS.
Dunedin,
OF THE IMPACT AND ACTIVE COMPONENTS OF DROP JUMPS USING FOURIER Ross, H. Sanders, and Barry, D. Wilson. University of Otago,
NZ.
The vertical
ground reaction forces of a jump following landing from a height may be regarded as a superposition of an impact component comprising high frequency waveforms and an active component comprising low frequency waveforms. An attempt was made to separate these components utilising the fact that the high frequency waveforms associated with the impact decay during the period of contact with the force platform. A Fourier transform was applied to the force data. An inverse transform was then performed for each frequency harmonic cutoff up to the Nyquist limit,. Root mean square (RMS) errors of each reconstructed function with respect to the original force function were calculated for each decile of the contact period. Selection of the appropriate harmonic cutoff to separate the impact and active components was based on the magnitude of the RMS errors for deciles 6,l and 8. Using this technique it was found that the impact component resembled a damped oscillation about the zero line in keeping with that expected. It was concluded that the Fourier technique with RMS error of deciles 6,7 and 8 being used as the criterion for the frequency cutoff was a satisfactory means of separating the active and impact components of a drop jump to permit independent analysis of these.
EXERCISE-RELATED ADAPTATION IN GEOMETRY PROPERTIES OF IMMATURE RAT TIBIA AND VERTEBRA
AND
MECHANICAL
George J. Salem, Kung-Chia Li, Ronald F. Zemicke, R. JamesBarnard Depamnent of Kinesiology, UCLA, Los Angeles, CA 90024-1568 USA To quantify the exercise-relatedresponsesof tibia and vertebra of rapidly-growing animals, 20 female Sprague-Dawley rats (8 wks, 1.50-170 g) were progressively (10 wks) trained (75-80% maximum aerobic capacity) on a motor-driven treadmill 5 d/wk until they were running 1.8 km/hr at a lo-12% grade for 1 hr/d. Twenty age-matched rats served as controls. Using a servocontrolled electromechanicaltesting system,3 point-bending teststo failure were conducted with tibia loaded in a medial to lateral direction at midlength; vertebral bodies were compressedto 50% of their initial height at a 50% /s strain rate. Tibial length, periosteal circumference, linear load, maximum load, energy to maximum load, and energy to failure decreased significantly in the exercised animals. Significant differencesin vertebral-body geomehy and mechanicalproperties were not found. Differential loading or differences in load responseof cortical and trabecular bone may account for the exercise-related adaptations.