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Spinal Cord and Reflexes
Published in Nassir H. Sabah, Neuromuscular Fundamentals, 2020
The tonic vibration reflex (TVR) is elicited by applying an electric vibrator to the muscle-tendon junction, the vibration being typically about 100 Hz in frequency and 1 mm or less in amplitude. The result is a slow contraction of the muscle that starts a few seconds after the application of vibration, builds up gradually to a level that is sustained as long as the vibration is applied, then gradually subsides over a few seconds after the vibration ceases. Recordings from α-motoneurons during the TVR reveal a slow depolarization with some epsps that are synchronized with the vibration and which are due to the monosynaptic terminations of the Ia afferents of the primary muscle spindles that are activated by the vibration. The slow depolarization is due to polysynaptic pathways mainly involving primary and secondary muscle spindles but also, and to a lesser extent, GTOs and cutaneous receptors.
Effects of Whole Body Vibration on the Elderly
Published in Redha Taiar, Christiano Bittencourt Machado, Xavier Chiementin, Mario Bernardo-Filho, Whole Body Vibrations, 2019
Maíra Florentino Pessoa, Helga C. Muniz de Souza, Helen K. Bastos Fuzari, Patrícia E. M. Marinho, Armèle Dornelas de Andrade
During vibration, muscle spindles are the first sensory structure activated, followed by Golgi tendon organs and type I and type II joint mechanoreceptors. Vibratory stimuli initially act on these three sensory structures, hypersensitizing the gamma (γ) system and leading to a contraction reflex called tonic vibration reflex (TVR), which recruits the motor units through the polysynaptic pathway. Parallel to this recruitment, maintenance of the vibratory stimulus leads motor units that are already in operation to derecruitment through a presynaptic inhibition mechanism with consequent reduction of the monosynaptic reflexes, so that the muscle tends to reduce its reflex stretch, improving contraction by synchronizing the motor units (Bogaerts et al., 2011).
The effects of whole-body vibration and head supported mass on performance and muscular demand
Published in Ergonomics, 2023
Aaron J. Derouin, Andrew J. Law, Heather Wright Beatty, Viresh Wickramasinghe, Steven L. Fischer
Contrary to our second hypothesis, we found that acute exposure to WBV led to an increase in peak angular velocity of the head in both the yaw and pitch axes (Figure 3). Indeed, the range of peak angular velocity magnitudes recorded in this study are consistent with those derived for various scanning tasks of military helicopter aircrew that are detailed in an operationally relevant physical demands analysis (Tack et al. 2014). Interestingly, exposure to acute WBV without the CW increased yaw peak angular velocity in the acceleration stage in a manner that is difficult to explain but may be contextualised by looking at examples from sports and reaching tasks. In evaluating the bat swing speed of baseball players, Reyes et al. (2010) found that pre-exposure to acute WBV increased bat speed by 2.6%. The one-repetition maximum of athletes performing half squats has also reportedly been improved by acute exposure to WBV (Rønnestad 2009). Various physiological mechanisms may be responsible for WBV-induced increases in movement speed and force production capacity of muscles. However, neurogenic potentiation via enhanced spinal reflex activity, known as the tonic vibration reflex (Cochrane 2011), is the most plausible explanation for the associated increase in muscular force and speed production associated with acute WBV exposure. This potential alteration of spinal reflex activity induced by WBV may have important implications for head control during the braking and corrective phase of rapid aiming head movements within the cockpit, which could make the cervical spine more susceptible to fatigue and injury.
Tendon vibration changes perceived joint angle independent of voluntary body motion direction in virtual environments
Published in Advanced Robotics, 2021
Daiki Hagimori, Naoya Isoyama, Shunsuke Yoshimoto, Nobuchika Sakata, Kiyoshi Kiyokawa
Vibration stimulation is a common method of activating muscle spindles and Golgi tendon organs [10]. However, the application of vibration to muscles may cause the tonic vibration reflex (TVR) and prevent the illusion. Anatomical evidence suggests that noninvasive electrical stimulation can activate muscle spindles and Golgi tendon organs [17]. This method activates Golgi tendon organs more selectively. However, the threshold level of the perception of pain induced by electrical stimulation varies among individuals, and more care should be taken when using electrical stimulation than when using vibration stimulation in terms of pain [18]. Finally, there is a way to give vibratory stimulation to the tendon rather than the muscle whenever possible. Vibration stimuli have lower spatial resolution than electrical stimuli, but TVR can be suppressed by attaching an actuator to a tendon. However, TVR may develop in areas where muscles and tendons are still tightly packed [11].
The effect of vibration on kinematics and muscle activation during cycling
Published in Journal of Sports Sciences, 2022
Josef Viellehner, Wolfgang Potthast
It has been suggested that involuntary reflex responses to the vibration stimulus increase muscle activation through the tonic vibration reflex (Burke et al., 1976). Previous studies described the effects of vibration on cycling performance in the perspective of a cost-oriented analysis, e.g., by averaging the muscular activation over several pedalling cycles and determining the resulting physiological energy demand. Vibration was shown to increase mean muscular activation (Munera et al., 2018; Rønnestad et al., 2018; Viellehner & Potthast, 2021), increase oxygen consumption (Rønnestad et al., 2018; Sperlich et al., 2012; Viellehner & Potthast, 2021) and elevate heartrate (Viellehner & Potthast, 2021) during cycling. A step towards a more detailed understanding of the effects of vibration on movement technique in cycling is the analysis of muscular activation and kinematics waveforms over the pedal cycle by means of the SPM statistics method (Pataky et al., 2016, 2015). This allows the interpretation of potential changes in muscular activity and kinematics during essential phases of pedalling cycle as the downstroke, around the 90° crank position. In this phase most of the propulsion is generated (Martin & Brown, 2009; Strutzenberger et al., 2014). The main power contributors are the muscles associated with the knee and hip joint, while the ankle joint mainly transmits the resulting forces to the crank (Aasvold et al., 2019; Mornieux et al., 2007; Zajac et al., 2002).Time-dependent tasks and differing contributions of joints and corresponding muscles illustrate that a phase-specific analysis adds an additional dimension to understanding whether vibrations translate into a functional impairment (Munera et al., 2018; Viellehner & Potthast, 2021).