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Asger Roer Pedersen, Peter William Stubbs, and Jørgen Feldbæk Nielsen

The aim was to investigate trial-by-trial response characteristics in the short-latency stretch reflex (SSR). Fourteen dorsiflexion stretches were applied to the ankle joint with a precontracted soleus muscle on 2 days. The magnitude and variability of trial-by-trial responses of the SSR were assessed. The SSR was log-normally distributed and variance heterogeneous between subjects. For some subjects, the magnitude and variance differed between days and stretches. As velocity increased, variance heterogeneity tended to decrease and response magnitude increased. The current study demonstrates the need to assess trial-by-trial response characteristics and not averaged curves. Moreover, it provides an analysis of SSR characteristics accounting for log-normally distributed and variance heterogeneous trial-by-trial responses.

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Daniela Mattos, Joshua Kuhl, John P. Scholz, and Mark L. Latash

The concept of motor equivalent combinations of arm muscles, or M-modes, was investigated during reaching to insert a pointer into a cylindrical target with and without an elbow perturbation. Five M-modes across 15 arm/scapula muscles were identified by principal component analysis with factor extraction. The relationship between small changes in the M-modes and changes in the position/orientation of the pointer were investigated by linear regression analyses. The results revealed a motor equivalent organization of the M-modes for perturbed compared with nonperturbed reaches, both with respect to hand position and orientation, especially in the first 100-ms postperturbation. Similar findings were obtained for motor equivalence computed based on changes in the joint configuration, although the kinematically defined motor equivalence was stronger for pointer orientation. The results support the hypothesis that the nervous system organizes muscles into M-modes and flexibly scales M-mode activation to preserve stable values of variables directly related to performance success.

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Jacob Buus Andersen and Thomas Sinkjaer

Due to the complexity of applying a well-defined stretch during human walking, most of our knowledge about the short latency stretch reflex modulation in humans is based on H-reflex studies. To illuminate the difference between the two methodologies, both types of reflexes were evoked in the same subjects, same experiment. Stretch reflexes were evoked via a stretch device capable of evoking stretch reflexes of the human soleus muscle during walking. H-reflexes were elicited by an electrical stimulation of the tibial nerve at the popliteal fossa at the knee. A significantly different modulation of the two reflexes was found in the late stance where the stretch reflex decreased in relation to the H-reflex. This was consistent with an unloading of the muscle spindles during the push-off in late stance, suggesting a complex alpha-gamma coactivation, if any, at this time of the step. The soleus stretch reflex and H-reflex were compared during the stance phase of walking and sitting at matched soleus EMG activity. No difference was found in the amplitude of the stretch reflex. However, there was a significant decrease of the H-reflex during the stance phase of walking, consistent with a task-specific presynaptic mediated reflex control. It is proposed that the short latency stretch reflex during walking is not sensitive to such a presynaptic inhibition.

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Original Article Statistical Considerations When Assessing Short Latency Stretch Reflexes in the Human Soleus Muscle Asger Roer Pedersen * Peter William Stubbs * Jørgen Feldbæk Nielsen * 10 2015 19 4 253 270 10.1123/mc.2013-0095 The Role of Sensorimotor Incongruence in Pain in Professional

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Muscle? Walter Herzog 11 1997 13 13 4 4 443 443 448 448 10.1123/jab.13.4.443 The Best Jump Is the Highest Jump At L. Hof 11 1997 13 13 4 4 448 448 451 451 10.1123/jab.13.4.448 Stretch Reflexes Can Have an Important Role in Force Enhancement during SSC Exercise Paavo V. Komi Albert Gollhofer 11

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Masakazu Matsuoka, Hiroshi Kunimura, and Koichi Hiraoka

contributes to stretch reflexes in the tibialis anterior muscle in man . Journal of Physiology, 512, 267 – 276 . PubMed ID: 9729635 doi:10.1111/j.1469-7793.1998.267bf.x 10.1111/j.1469-7793.1998.267bf.x Runge , C.F. , Shupert , C.L. , Horak , F.B. , & Zajac , F.E. ( 1998 ). Role of vestibular

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Nicholas Tam, Ross Tucker, Jordan Santos-Concejero, Danielle Prins, and Robert P. Lamberts

the muscle spindle potentiating stretch reflexes to enhance musculotendinous stiffness, thus improving running economy. 32 Regarding stride frequency, our results also agree with previous literature. 33 An important reason why this relationship between these spatiotemporal variables and running

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Olaf Prieske, Helmi Chaabene, Christian Puta, David G. Behm, Dirk Büsch, and Urs Granacher

. Stretch reflexes can have an important role in force enhancement during SSC exercise . J Appl Biomech . 1997 ; 13 ( 4 ): 451 – 460 . doi:10.1123/jab.13.4.451 10.1123/jab.13.4.451 9. Bencke J , Damsgaard R , Saekmose A , Jorgensen P , Jorgensen K , Klausen K . Anaerobic power and muscle

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Luca Puce, Ilaria Pallecchi, Lucio Marinelli, Maria May, Laura Mori, Piero Ruggeri, and Marco Bove

-dependent increase in the tonic stretch reflexes (“muscle tone”) with exaggerated tendon jerks resulting from hyperexcitability of the stretch reflex. 1 Compelling evidence exists that spasticity is due to an exaggerated stretch reflex. 2 – 4 Spasticity may assist motor function and motor coordination, yet it may