The muscle activity paradox during circular rhythmic leg movements
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CONTRIBUTORS:
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JOURNAL:
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YEAR:
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1988
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PUB TYPE:
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Journal Article
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SUBJECT(S):
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LEG; MUSCLE; CYCLING; KINESIOLOGY; ELECTROMYOGRAPHY; BIOMECHANICS
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DISCIPLINE:
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No discipline assigned
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HTTP:
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LANGUAGE:
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English
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PUB ID:
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103-366-263
(Last edited on
2002/02/27 18:45:02 US/Mountain)
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SPONSOR(S):
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ABSTRACT:
In order to analyze simple and complex leg movement during cycling, the activity of six lower limb muscles was measured under field circumstances on nine elite cyclists using a portable EMG data acquisition system and active surface electrodes allowing remote (non-telemetric) monitoring of the cyclists' muscle activity patterns. Measurements were made during a 1000 m submaximal but constant effort and during a 200 m sprint. Confirmation of the anatomical paradox was found in both test circumstances. Analyses of the normalized EMG in combination with torque values of both hip and knee during the pedalling cycle indicate a zero torque at 135 degrees for the knee, while at this same angle the overall extensor activity ends in one leg and starts simultaneously in the other leg (at 315 degrees). Since the propulsion does not continue until 180 degrees, the flexor muscles have to be activated before the extension activity ends in order to generate the continuation of the circular motion until (and beyond) the bottom dead centre (180 degrees). In addition, differences in muscular intensity were found between submaximal and sprint cycling. Treadmill studies (from the literature) do not produce identical patterns to field measurements, due to six different ankling patterns.
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