Short-latency stretch reflex modulation in response to varying soleus muscle activities. |
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| Authors: | K Ogiso J M McBride T Finni P V Komi |
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| Affiliation: | 1. Neuromuscular Research Center, Department of Biology of Physical Activity, University of Jyväskylä, 40100, Jyväskylä, Finland;2. Department of Education, Kogakkan University, 1704 Kodakujimoto-cho, Ise, 516-8555, Mie, Japan;3. University of Wisconsin — La Crosse, 152 Mitchell Hall, La Crosse, WI 54601, USA;1. Department of Morphology, Federal University of Minas Gerais, Brazil;2. Department of Technical Services, Agroceres PIC, Brazil;3. Department of Veterinary Clinic and Surgery, Federal University of Minas Gerais, Brazil;1. Department of Information Engineering, Università Politecnica delle Marche, 60131 Ancona, Italy;2. Posture and Movement Analysis Laboratory, Italian National Institute of Health and Science on Aging (INRCA), 60131 Ancona, Italy;1. Laboratorio de Neurobiología del Sueño, Departamento de Fisiología, Facultad de Medicina, Universidad de la República, Montevideo, Uruguay;2. Departamento de Farmacología y Terapéutica, Hospital de Clínicas, Universidad de la República, Montevideo, Uruguay;1. Department of Biomedical Engineering, Duke University, Durham, NC, USA;2. Department of Electrical and Computer Engineering, Duke University, Durham, NC, USA;3. Department of Neurobiology, Duke University, Durham, NC, USA;1. Molecular Imaging Center Antwerp, Universiteitsplein 1 – 2610 Wilrijk, University of Antwerp, Antwerp, Belgium;2. Department of Nuclear Medicine, Wilrijkstraat 10 – 2650 Edegem, University Hospital Antwerp, Antwerp, Belgium |
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| Abstract: | The current investigation examined the effect of various types of background muscle contractions on the short-latency stretch reflex (SLR) elicited from the soleus muscle while subjects were in a sitting position. A stretch was applied to the calf muscles while they performed an isometric (pre-ISO), shortening (pre-SHO) and lengthening contraction (pre-LEN) with several pre-contraction levels. The ankle was at a 90 degrees tibio-tarsal joint angle when the perturbation was applied. Subjects developed and maintained a given pre-load level, which was maintained at various percentages of the maximum voluntary isometric plantar flexion torque. This was performed at 80 degrees in pre-SHO, 90 degrees in pre-ISO and 100 degrees in pre-LEN for about 2s before the contractions. The SLRs in trials with 0, 35 and 50% of the maximum voluntary contraction torque level were compared among the three conditions. The main results were as follows. (1) Pre-ISO and pre-SHO showed an equal SLR area and a different SLR waveform in the active muscle. (2) Pre-LEN showed the smallest SLR area of three conditions in the active muscle. (3) Pre-LEN showed shorter SLR latencies than the other conditions. (4) Pre-SHO showed a longer SLR latency in the relaxed muscle than in the active muscle. (5) The SLR area was larger in the active muscle than in the relaxed muscle. These findings demonstrate that the muscle contraction type and the pre-contraction level before a stretch perturbation have a considerable influence on the latency, the area and the waveform of the SLR. In particular, the equal area and the different waveforms of the SLR between pre-ISO and pre-SHO were a unique finding in the present study. They might result from differences in muscle spindle sensitivity and afferent input from various receptors induced by the present motor task. |
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