Effects of Clenching Strength on Exercise Performance: Verification Using Spinal Function Assessments

2021 ◽  
pp. 194173812110148
Author(s):  
Ryo Hirabayashi ◽  
Mutsuaki Edama ◽  
Arisa Saito ◽  
Yuki Yamada ◽  
Ryohei Nawa ◽  
...  
Keyword(s):  
Exercise Performance ◽  
Maximum Voluntary Contraction ◽  
High Strength ◽  
Peak Torque ◽  
Voluntary Contraction ◽  
Ankle Dorsiflexion ◽  
Anterior Horn ◽  
Joint Movement ◽  
Level Of Evidence ◽  
Spinal Function

Background: This study aimed to determine the relationship between exercise performance and spinal function based on clenching strength. Hypothesis: Low-intensity clenching contributes to joint movement, whereas high-intensity clenching contributes to joint fixation. Study Design: Randomized crossover trial. Level of Evidence: Level 3. Methods: Two experiments were conducted using 2 groups of 20 healthy adults. The 4 clenching conditions in experiment 1 were 0%, 12.5%, 25%, and 50% of the maximum voluntary contraction (MVC) of the masseter muscle. Experiment 2 consisted of 3 conditions: no-bite condition, moderate effort, and maximum effort (max condition). In experiment 1, spinal function and ankle dorsiflexion tasks were measured for each clenching condition, and the ankle dorsiflexion task was measured in experiment 2. Regarding spinal function, we measured spinal reciprocal inhibition (RI) and excitability of spinal anterior horn cells. For the ankle dorsiflexion task, ankle dorsiflexion MVC was performed for 3 seconds under each clenching condition. The items analyzed were reaction time, peak ankle dorsiflexion torque, and soleus (Sol)/tibialis anterior (TA) electromyography (EMG) ratio. Results: The results of experiment 1 illustrated that RI was significantly attenuated or eliminated with increasing clenching strength (>25% MVC). Spinal anterior horn cell excitability increased significantly with increasing clenching strength. The peak torque was significantly higher at 50% MVC than that at 0% MVC. In experiment 2, the peak torque was significantly higher under moderate and max conditions than no-bite condition, and the Sol/TA EMG ratio was significantly higher under max condition than that under moderate condition. Conclusion/Clinical Relevance: The results illustrated that during high-strength clenching (≥50% MVC), antagonist muscles are activated simultaneously to increase muscle strength. High-strength clenching improved kinetic performance (joint fixation), whereas low-strength clenching (<50% MVC) enhanced exercise performance (joint movement).

scholarly journals Effects of whole-body vibrations on neuromuscular fatigue: a study with sets of different durations

PeerJ ◽  
2020 ◽  
Vol 8 ◽  
pp. e10388
Author(s):  
Miloš Kalc ◽  
Ramona Ritzmann ◽  
Vojko Strojnik
Keyword(s):  
High Frequency ◽  
Maximum Voluntary Contraction ◽  
Peak Torque ◽  
Voluntary Contraction ◽  
Neuromuscular Fatigue ◽  
Voluntary Activation ◽  
Whole Body ◽  
Peripheral Fatigue ◽  
Single Twitch ◽  
Whole Body Vibrations

Background Whole body vibrations have been used as an exercise modality or as a tool to study neuromuscular integration. There is increasing evidence that longer WBV exposures (up to 10 minutes) induce an acute impairment in neuromuscular function. However, the magnitude and origin of WBV induced fatigue is poorly understood. Purpose The study aimed to investigate the magnitude and origin of neuromuscular fatigue induced by half-squat long-exposure whole-body vibration intervention (WBV) with sets of different duration and compare it to non-vibration (SHAM) conditions. Methods Ten young, recreationally trained adults participated in six fatiguing trials, each consisting of maintaining a squatting position for several sets of the duration of 30, 60 or 180 seconds. The static squatting was superimposed with vibrations (WBV30, WBV60, WBV180) or without vibrations (SHAM30, SHAM60, SHAM180) for a total exercise exposure of 9-minutes in each trial. Maximum voluntary contraction (MVC), level of voluntary activation (%VA), low- (T20) and high-frequency (T100) doublets, low-to-high-frequency fatigue ratio (T20/100) and single twitch peak torque (TWPT) were assessed before, immediately after, then 15 and 30 minutes after each fatiguing protocol. Result Inferential statistics using RM ANOVA and post hoc tests revealed statistically significant declines from baseline values in MVC, T20, T100, T20/100 and TWPT in all trials, but not in %VA. No significant differences were found between WBV and SHAM conditions. Conclusion Our findings suggest that the origin of fatigue induced by WBV is not significantly different compared to control conditions without vibrations. The lack of significant differences in %VA and the significant decline in other assessed parameters suggest that fatiguing protocols used in this study induced peripheral fatigue of a similar magnitude in all trials.

scholarly journals INDICATORS OF NEUROMUSCULAR FATIGUE IN LEG PRESS EXERCISE IN MEN AND WOMEN

2020 ◽  
Vol 26 (3) ◽  
pp. 243-247
Author(s):  
Camila Brasileiro Azevedo Barros ◽  
Manoel da Cunha Costa ◽  
Antônio Gonçalves dos Santos Neto ◽  
José Hildemar Teles Gadelha ◽  
Brendha Stephany Rodrigues da Silva ◽  
...  
Keyword(s):  
Muscle Activation ◽  
Isometric Force ◽  
Maximum Voluntary Contraction ◽  
Voluntary Contraction ◽  
Level Of Evidence ◽  
Similar Reduction ◽  
Time Curve ◽  
Men And Women ◽  
Leg Press ◽  
Force Time

ABSTRACT Introduction Muscle fatigue is characterized by reduced ability to produce maximum strength or power, and may differ between men and women. Changes in velocity of movement during exercise, and in the ability to produce strength after exercise, may help when comparing fatigue in men and women. Objective To analyze the differences between men and women in relation to number of repetitions, kinetics, kinematics and isometric force-time curve performance, and their respective muscle activation in horizontal leg press exercises. Methods Fifteen men and fifteen women underwent isometric force-time curve (Cf-t) and electromyographic (EMG) assessments before and after performing horizontal leg press exercises. The exercises were performed in three sets until voluntary exhaustion, at 70% maximal repetition. During the exercises, kinetic and kinematic variables were obtained by means of two force transducers, a linear position potentiometer and accelerometer adapted for the horizontal leg press and synchronized by a signal conditioning plate. Results The mean propulsive velocity significantly reduced between the first and last repetition of each series, with a similar reduction for men (-12.4 to -29.2%) and women (-29.2 to -35.6%). The same pattern was observed for the other kinetic and kinematic variables. The maximum voluntary contraction and peak force development rate also decreased for both men (-15.1 ± 8.7% and -26.9 ± 21.2%, respectively) and women (-13.9 ± 10.4% and -28.2 ± 11.5%, respectively). Conclusion Based on the different variables used to quantify the effect of fatigue during and after horizontal leg press exercises, the research found practically no differences between men and women. Level of evidence II; Comparative prospective study.

scholarly journals The Physiological and Perceptual Effects of Stochastic Simulated Rugby League Match Play

2021 ◽  
Vol 16 (1) ◽  
pp. 73-79
Author(s):  
Thomas Mullen ◽  
Craig Twist ◽  
Jamie Highton
Keyword(s):  
Perceived Exertion ◽  
Maximum Voluntary Contraction ◽  
Peak Torque ◽  
Team Sport ◽  
Rugby League ◽  
Stroop Test ◽  
Voluntary Contraction ◽  
Rating Of Perceived Exertion ◽  
Voluntary Activation ◽  
Cognitive Responses

Purpose: To examine responses to a simulated rugby league protocol designed to include more stochastic commands, and therefore require greater vigilance, than traditional team-sport simulation protocols. Methods: Eleven male university rugby players completed 2 trials (randomized and control [CON]) of a rugby league movement simulation protocol, separated by 7 to 10 d. The CON trial consisted of 48 repeated ∼115-s cycles of activity. The stochastic simulation (STOCH) was matched for the number and types of activity performed every 5.45 min in CON but included no repeated cycles of activity. Movement using GPS, heart rate, rating of perceived exertion, and Stroop test performance was assessed throughout. Maximum voluntary contraction peak torque, voluntary activation (in percentage), and global task load were assessed after exercise. Results: The mean mental demand of STOCH was higher than CON (effect size [ES] = 0.56; ±0.69). Mean sprint speed was higher in STOCH (22.5 [1.4] vs 21.6 [1.6] km·h−1, ES = 0.50; ±0.55), which was accompanied by a higher rating of perceived exertion (14.3 [1.0] vs 13.0 [1.4], ES = 0.87; ±0.67) and a greater number of errors in the Stroop test (10.3 [2.5] vs 9.3 [1.4] errors; ES = 0.65; ±0.83). Maximum voluntary contraction peak torque (CON = −48.4 [31.6] N·m and STOCH = −39.6 [36.6] N·m) and voluntary activation (CON = −8.3% [4.8%] and STOCH = −6.0% [4.1%]) was similarly reduced in both trials. Conclusions: Providing more stochastic commands, which requires greater vigilance, might alter performance and associated physiological, perceptual, and cognitive responses to team-sport simulations.

scholarly journals Development of a trunk motor paradigm for use in neuroimaging

2020 ◽  
Vol 11 (1) ◽  
pp. 193-200
Author(s):  
Elizabeth Saunders ◽  
Brian C. Clark ◽  
Leatha A. Clark ◽  
Dustin R. Grooms
Keyword(s):  
Motor Control ◽  
Maximum Voluntary Contraction ◽  
Voluntary Contraction ◽  
Erector Spinae ◽  
Head Motion ◽  
Low Back ◽  
Cyclic Contraction ◽  
Cyclic Contractions ◽  
Measurement Units ◽  
Healthy Participants

AbstractThe purpose of this study was to quantify head motion between isometric erector spinae (ES) contraction strategies, paradigms, and intensities in the development of a neuroimaging protocol for the study of neural activity associated with trunk motor control in individuals with low back pain. Ten healthy participants completed two contraction strategies; (1) a supine upper spine (US) press and (2) a supine lower extremity (LE) press. Each contraction strategy was performed at electromyographic (EMG) contraction intensities of 30, 40, 50, and 60% of an individually determined maximum voluntary contraction (MVC) (±10% range for each respective intensity) with real-time, EMG biofeedback. A cyclic contraction paradigm was performed at 30% of MVC with US and LE contraction strategies. Inertial measurement units (IMUs) quantified head motion to determine the viability of each paradigm for neuroimaging. US vs LE hold contractions induced no differences in head motion. Hold contractions elicited significantly less head motion relative to cyclic contractions. Contraction intensity increased head motion in a linear fashion with 30% MVC having the least head motion and 60% the highest. The LE hold contraction strategy, below 50% MVC, was found to be the most viable trunk motor control neuroimaging paradigm.

scholarly journals The Effects of Spinal Manipulation on Motor Unit Behavior

2021 ◽  
Vol 11 (1) ◽  
pp. 105
Author(s):  
Lucien Robinault ◽  
Aleš Holobar ◽  
Sylvain Crémoux ◽  
Usman Rashid ◽  
Imran Khan Niazi ◽  
...  
Keyword(s):  
Motor Unit ◽  
Conduction Velocity ◽  
Spinal Manipulation ◽  
Maximum Voluntary Contraction ◽  
Force Production ◽  
Movement Control ◽  
Position Sense ◽  
Joint Position Sense ◽  
Voluntary Contraction ◽  
Passive Movement

Over recent years, a growing body of research has highlighted the neural plastic effects of spinal manipulation on the central nervous system. Recently, it has been shown that spinal manipulation improved outcomes, such as maximum voluntary force and limb joint position sense, reflecting improved sensorimotor integration and processing. This study aimed to further evaluate how spinal manipulation can alter neuromuscular activity. High density electromyography (HD sEMG) signals from the tibialis anterior were recorded and decomposed in order to study motor unit changes in 14 subjects following spinal manipulation or a passive movement control session in a crossover study design. Participants were asked to produce ankle dorsiflexion at two force levels, 5% and 10% of maximum voluntary contraction (MVC), following two different patterns of force production (“ramp” and “ramp and maintain”). A significant decrease in the conduction velocity (p = 0.01) was observed during the “ramp and maintain” condition at 5% MVC after spinal manipulation. A decrease in conduction velocity suggests that spinal manipulation alters motor unit recruitment patterns with an increased recruitment of lower threshold, lower twitch torque motor units.

Comparison of Biomechanical and Anatomical Effects Following Eccentric and Concentric Exertions

2005 ◽  
Vol 49 (14) ◽  
pp. 1287-1291
Author(s):  
Amrish O. Chourasia ◽  
Mary E. Sesto ◽  
Youngkyoo Jung ◽  
Robert S. Howery ◽  
Robert G. Radwin
Keyword(s):  
Signal Intensity ◽  
Intensity Ratio ◽  
Maximum Voluntary Contraction ◽  
Magnetic Resonance Images ◽  
Voluntary Contraction ◽  
Work Place ◽  
Signal Intensity Ratio ◽  
Mechanical Stiffness ◽  
Average Decrease ◽  
Muscle Shortening

Work place exertions may include muscle shortening (concentric) or muscle lengthening (eccentric) contractions. This study investigates the upper limb mechanical properties and magnetic resonance images (MRI) of the involved muscles following submaximal eccentric and concentric exertions. Twelve participants were randomly assigned to perform at 30° per second eccentric or concentric forearm supination exertions at 50% isometric maximum voluntary contraction (MVC) for 30 minutes. Measurement of mechanical stiffness, isometric MVC, localized discomfort and MRI supinator: extensor signal intensity ratio was done before, immediately after, 1 hour after and 24 hours after the bout of exercise. A 53% average decrease in mechanical stiffness after 1 hour was observed for the eccentric group (p< 0.05) compared to a 1% average decrease for the concentric group (p> 0.05). Edema, indicative of swelling, was observed 24 hrs after exercise, with an average increase in the MRI supinator: extensor signal intensity ratio of 36% for the eccentric group and less than 10% for the concentric group (p<0.05).

scholarly journals Long-Term Microgravity Effects on Isometric Handgrip and Precision Pinch Force with Visual and Proprioceptive Feedback

2018 ◽  
Vol 2018 ◽  
pp. 1-11
Author(s):  
Ilario Puglia ◽  
Michele Balsamo ◽  
Marco Vukich ◽  
Valfredo Zolesi
Keyword(s):  
Maximum Voluntary Contraction ◽  
Space Station ◽  
Voluntary Contraction ◽  
Force Output ◽  
Isometric Handgrip ◽  
Short Term ◽  
Space Flights ◽  
Pinch Force ◽  
Long Duration

The study and analysis of human physiology during short- and long-duration space flights are the most valuable approach in order to evaluate the effect of microgravity on the human body and to develop possible countermeasures in prevision of future exploratory missions and Mars expeditions. Hand performances such as force output and manipulation capacity are fundamental for astronauts’ intra- and extravehicular activities. Previous studies on upper limb conducted on astronauts during short-term missions (10 days) indicated a temporary partial reduction in the handgrip maximum voluntary contraction (MVC) followed by a prompt recovery and adaptation to weightlessness during the last days of the mission. In the present study, we report on the “Crew’s Health: Investigation on Reduced Operability” (CHIRO) protocol, developed for handgrip and pinch force investigations, performed during the six months increment 7 and increment 8 (2003-2004) onboard International Space Station (ISS). We found that handgrip and pinch force performance are reduced during long-term increments in space and are not followed by adaptation during the mission, as conversely reported during short-term increment experiments. The application of protocols developed in space will be eligible to astronauts during long-term space missions and to patients affected by muscle atrophy diseases or nervous system injury on Earth.

Index finger position and force of the human first dorsal interosseus and its ulnar nerve antagonist

1994 ◽  
Vol 77 (2) ◽  
pp. 987-997 ◽  
Author(s):  
I. Zijdewind ◽  
D. Kernell
Keyword(s):  
Ulnar Nerve ◽  
Index Finger ◽  
Maximum Voluntary Contraction ◽  
Normal Subjects ◽  
Voluntary Contraction ◽  
Abduction Angle ◽  
Hand Position ◽  
First Dorsal Interosseus ◽  
Length Analysis ◽  
Neutral Angle

In normal subjects, maximum voluntary contraction (MVC) and electrical ulnar nerve stimulation (UNS; 30-Hz bursts of 0.33 s) were systematically compared with regard to the forces generated in different directions (abduction/adduction and flexion) and at different degrees of index finger abduction. With a “resting” hand position in which there was no index finger abduction, UNS produced about one-half of the abduction force elicited by an MVC (mean ratio 51%). Qualitatively, such a discrepancy would be expected, because UNS activates two index finger muscles with opposing actions in the abduction/adduction plane of torques: the first dorsal interosseus (FDI) and the first palmar interosseus (FPI). The abduction forces produced by MVC and UNS were very sensitive to index finger abduction angle: at a maximum degree of abduction, the UNS-generated force even reversed its direction of action to adduction (with FPI dominating) and the abduction MVC declined to 37% of that in the resting hand position. Inasmuch as these declines in MVC- and UNS-generated abduction force could not be explained by a change in moment arm, the main alternative seemed to be abduction-associated alterations in FDI fiber length (analysis by previously published biomechanical data). The FDI and FPI were further compared by application of a UNS-generated fatigue test (5-min burst stimulation), with the index finger kept at a "neutral" angle, i.e., the abduction angle at which, in the unfatigued state, the forces of the FDI and FPI were in balance (zero net UNS-generated abduction/adduction force).(ABSTRACT TRUNCATED AT 250 WORDS)

Changes in muscle fiber conduction velocity indicate recruitment of distinct motor unit populations

2003 ◽  
Vol 95 (3) ◽  
pp. 1045-1054 ◽  
Author(s):  
C. J. Houtman ◽  
D. F. Stegeman ◽  
J. P. Van Dijk ◽  
M. J. Zwarts
Keyword(s):  
Conduction Velocity ◽  
Muscle Fiber ◽  
Tibialis Anterior Muscle ◽  
Maximum Voluntary Contraction ◽  
Isometric Exercise ◽  
Motor Units ◽  
Voluntary Contraction ◽  
Type I ◽  
Muscle Fiber Conduction Velocity ◽  
Depth Study

To obtain more insight into the changes in mean muscle fiber conduction velocity (MFCV) during sustained isometric exercise at relatively low contraction levels, we performed an in-depth study of the human tibialis anterior muscle by using multichannel surface electromyogram. The results show an increase in MFCV after an initial decrease of MFCV at 30 or 40% maximum voluntary contraction in all of the five subjects studied. With a peak velocity analysis, we calculated the distribution of conduction velocities of action potentials in the bipolar electromyogram signal. It shows two populations of peak velocities occurring simultaneously halfway through the exercise. The MFCV pattern implies the recruitment of two different populations of motor units. Because of the lowering of MFCV of the first activated population of motor units, the newly recruited second population of motor units becomes visible. It is most likely that the MFCV pattern can be ascribed to the fatiguing of already recruited predominantly type I motor units, followed by the recruitment of fresh, predominantly type II, motor units.

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