Physiological tremor is suppressed and force steadiness is enhanced with increased availability of serotonin regardless of muscle fatigue

2021 ◽  
Author(s):  
Tyler Thomas Henderson ◽  
Jacob R Thorstensen ◽  
Steven Morrison ◽  
Murray G Tucker ◽  
Justin J Kavanagh
Keyword(s):  
Steady State ◽  
Peak Power ◽  
Elbow Flexion ◽  
Voluntary Contraction ◽  
Isometric Contractions ◽  
Physiological Tremor ◽  
Constant Force ◽  
Force Steadiness ◽  
Main Effects ◽  
Flexion Force

Although there is evidence that 5-HT acts as an excitatory neuromodulator to enhance maximal force generation, it is largely unknown how 5-HT activity influences the ability to sustain a constant force during steady-state contractions. A total of 22 healthy individuals participated in the study, where elbow flexion force was assessed during brief isometric contractions at 10% maximal voluntary contraction (MVC), 60% MVC, MVC, and during a sustained MVC. The selective serotonin reuptake inhibitor, paroxetine, suppressed physiological tremor and increased force steadiness when performing the isometric contractions. In particular, a main effect of drug was detected for peak power of force within the 8-12 Hz range (p = 0.004) and the coefficient of variation (CV) of force (p < 0.001). A second experiment was performed where intermittent isometric elbow flexions (20% MVC sustained for 2 min) were repeatedly performed so that serotonergic effects on physiological tremor and force steadiness could be assessed during the development of fatigue. Main effects of drug were once again detected for peak power of force in the 8-12 Hz range (p = 0.002) and CV of force (p = 0.003), where paroxetine suppressed physiological tremor and increased force steadiness when the elbow flexors were fatigued. The findings of this study suggest that enhanced availability of 5-HT in humans has a profound influence of maintaining constant force during steady state contractions. The action of 5-HT appears to suppress fluctuations in force regardless of the fatigue state of the muscle.

Changes in Elbow Flexor Power with Intermittent Contractions and Various Loads

2008 ◽  
Vol 107 (2) ◽  
pp. 597-606
Author(s):  
Shunsuke Yamaji ◽  
Shinichi Demura ◽  
Hiroki Aoki ◽  
Kei Yamamoto
Keyword(s):  
Power Output ◽  
Peak Power ◽  
Muscle Power ◽  
Average Power ◽  
Elbow Flexion ◽  
Voluntary Contraction ◽  
Significant Difference ◽  
Average Power Output ◽  
Power Outputs ◽  
Intermittent Contractions

This study examined intermittent elbow flexion every 2 see. for 1 min. using various loads to study the properties of muscle power output and their relationship to peak power, defined as the maximum power output. 18 young men performed intermittent explosive elbow flexion (30 times × min.−1) using 30%, 40%, and 50% maximal voluntary contraction (MVC). The power outputs at 30% and 40% MVC slightly decreased (rate of decrease from peak power to average power output during the 26 to 30 contractions was about 5%). However, at 50% MVC, there was a marked decrease (33.6%). Power output for 8 contractions was significantly larger at 50% MVC than at 30% and 40% MVC, but after 9 contractions there was no significant difference between 40% and 50% MVC. In addition, after 27 contractions, 40% MVC was significantly larger than 30% and 50% MVC. That is, the tendency for power output to decrease differed among the various loads. The rate of decrease of power outputs showed no significant correlation with peak power for each load. Therefore, the rate of decrease or power output in intermittent contractions may help sustain the power output and cannot be evaluated as accurately as peak power.

Force Perception before and after Maximal Voluntary Contraction

1993 ◽  
Vol 76 (2) ◽  
pp. 399-402 ◽  
Author(s):  
Judith L. Gooch ◽  
Jeffrey Randle
Keyword(s):  
Maximal Voluntary Contraction ◽  
Elbow Flexion ◽  
Voluntary Contraction ◽  
Low Level ◽  
Force Perception ◽  
Before And After ◽  
The Mean ◽  
Flexion Force

Capacity to match a low level of elbow flexion force maintained in the control arm was measured in the experimental arm in 16 subjects before and after maximal voluntary contraction (MVC). Prior to a 1-min. MVC, the mean force exerted by the experimental arm was 3.4 ± 1.0 kg when attempting to match the tension of a 2.3-kg weight in the control arm. After the MVC, the mean force exerted in the experimental arm was 4.4 ± 2.6 kg. The change in perception of force after a prolonged MVC as demonstrated in this study may be due to postcontraction potentiation of contraction, which has been demonstrated by others after a brief MVC.

Laterality of Hand Grip and Elbow Flexion Power in Right Hand–Dominant Individuals

2009 ◽  
Vol 4 (3) ◽  
pp. 355-366 ◽  
Author(s):  
Hiroki Aoki ◽  
Shinichi Demura
Keyword(s):  
Gender Difference ◽  
Peak Power ◽  
Maximum Voluntary Contraction ◽  
Elbow Flexion ◽  
Voluntary Contraction ◽  
Power Ratio ◽  
Young Males ◽  
Left Hand ◽  
Hand Grip ◽  
Right Hand

Purpose:This study aimed to compare the laterality, and its gender difference, of hand grip and elbow flexion power according to load in right hand–dominant individuals.Results:The subjects were 15 healthy young males (age 22.1 ± 0.7 y, height 171.3 ± 3.4 cm, mass 64.5 ± 4.1 kg) and 15 healthy young females (age 22.4 ± 1.0 y, height 161.1 ± 3.0 cm, mass 55.4 ± 4.6 kg). Isotonic peak power was measured with 6 different loads ranging from 20% to 70% of maximum voluntary contraction (MVC) for grip and elbow flexion movements.Results:The peak power was significantly larger in males than in females in both movements (ratio, males:females was 58.1:49.4%). The dominant right hand had larger peak power in all loads for hand grip power (ratio, dominant:nondominant was 83.6:71.1%) and in loads of 20% to 50% MVC for elbow flexion power (88.7:85.7%) in both genders, confirming laterality in both movements. The peak power ratio of the dominant right hand to the nondomi-nant left hand was significantly larger in hand grip than in elbow flexion for all loads in females.Conclusion:Even though laterality was confirmed in both grip and elbow flexion, gender difference is more marked in hand grip.

scholarly journals Exercise tolerance during muscle contractions below and above the critical torque in different muscle groups

2018 ◽  
Vol 43 (2) ◽  
pp. 174-179 ◽  
Author(s):  
Leonardo Henrique Perinotto Abdalla ◽  
Benedito Sérgio Denadai ◽  
Natália Menezes Bassan ◽  
Camila Coelho Greco
Keyword(s):  
Exercise Intensity ◽  
Maximal Voluntary Contraction ◽  
Exercise Tolerance ◽  
Voluntary Contraction ◽  
Knee Extensors ◽  
Isometric Contractions ◽  
Plantar Flexors ◽  
Significant Difference ◽  
Muscle Groups

The objective of this study was to test the hypotheses that end-test torque (ET) (expressed as % maximal voluntary contraction; MVC) is higher for plantar flexors (PF) than knee extensors (KE) muscles, whereas impulse above ET (IET) is higher for KE than PF. Thus, we expected that exercise tolerance would be longer for KE than PF only during the exercise performed above ET. After the determination of MVC, 40 men performed two 5-min all-out tests to determine ET and IET. Eleven participants performed a further 4 intermittent isometric tests, to exhaustion, at ET + 5% and ET – 5%, and 1 test for KE at the exercise intensity (%MVC) corresponding to ET + 5% of PF. The IET (7243.2 ± 1942.9 vs. 3357.4 ± 1132.3 N·m·s) and ET (84.4 ± 24.8 vs. 73.9 ± 19.5 N·m) were significantly lower in PF compared with KE. The exercise tolerance was significantly longer for PF (300.7 ± 156.7 s) than KE (156.7 ± 104.3 s) at similar %MVC (∼60%), and significantly shorter for PF (300.7 ± 156.7 s) than KE (697.0 ± 243.7 s) at ET + 5% condition. However, no significant difference was observed for ET – 5% condition (KE = 1030.2 ± 495.4 s vs. PF = 1028.3 ± 514.4 s). Thus, the limit of tolerance during submaximal isometric contractions is influenced by absolute MVC only during exercise performed above ET, which seems to be explained by differences on both ET (expressed as %MVC) and IET values.

Modelling Age Differences in Isometric Elbow Flexion Using Hill's Three-Element Visco-Elastic Model

1993 ◽  
Vol 37 (2) ◽  
pp. 202-205
Author(s):  
R. Darin Ellis ◽  
Kentaro Kotani
Keyword(s):  
Mechanical Properties ◽  
Steady State ◽  
Age Differences ◽  
Elbow Flexion ◽  
Model Parameters ◽  
Elastic Model ◽  
Tissue Elasticity ◽  
Age Related ◽  
Complex Models ◽  
State Force

A visco-elastic model of the mechanical properties of muscle was used to describe age-differences in the buildup of force in isometric elbow flexion. Given information from the literature on age-related physiological changes, such as decreasing connective-tissue elasticity, one would expect changes in the mechanical properties of skeletal muscle and their related model parameters. Force vs. time curves were obtained for 7 young (aged 21–27) and 7 old (aged 69–83) female subject. There were significant age group differences in steady-state force level and the best fitting model parameters. In particular, the viscous damping element of the model plays a large role in describing the increased time to reach steady-state force levels in the older subject group. Implications of this research include incorporating parameter differences into more complex models, such as crash impact models.

Mechanical behavior of skeletal muscle during intermittent voluntary isometric contractions in humans

1997 ◽  
Vol 83 (5) ◽  
pp. 1557-1565 ◽  
Author(s):  
N. K. Vøllestad ◽  
I. Sejersted ◽  
E. Saugen
Keyword(s):  
Skeletal Muscle ◽  
Mechanical Behavior ◽  
Recovery Period ◽  
Oscillation Amplitude ◽  
Voluntary Contraction ◽  
Knee Extensors ◽  
Isometric Contractions ◽  
Target Force ◽  
The Mean ◽  
Type Of Exercise

Vøllestad, N. K., I. Sejersted, and E. Saugen. Mechanical behavior of skeletal muscle during intermittent voluntary isometric contractions in humans. J. Appl. Physiol. 83(5): 1557–1565, 1997.—Changes in contractile speed and force-fusion properties were examined during repetitive isometric contractions with the knee extensors at three different target force levels. Seven healthy subjects were studied at target force levels of 30, 45, and 60% of their maximal voluntary contraction (MVC) force. Repeated 6-s contractions followed by 4-s rest were continued until exhaustion. Contractile speed was determined for contractions elicited by electrical stimulation at 1–50 Hz given during exercise and a subsequent 27-min recovery period. Contraction time remained unchanged during exercise and recovery, except for an initial rapid shift in the twitch properties. Half relaxation time (RT1/2) decreased gradually by 20–40% during exercise at 30 and 45% of MVC. In the recovery period, RT1/2 values were not fully restored to preexercise levels. During exercise at 60% MVC, the RT1/2 decreased for twitches and increased for the 50-Hz stimulation. In the recovery period after 60% MVC, RT1/2 values declined toward those seen after the 30 and 45% MVC exercise. The force oscillation amplitude in unfused tetani relative to the mean force increased during exercise at 30 and 45% MVC but remained unaltered during the 60% MVC exercise. This altered force-fusion was closely associated with the changes in RT1/2. The faster relaxation may at least partly explain the increased energy cost of contraction reported previously for the same type of exercise.

scholarly journals Rate modulation of human anconeus motor units during high-intensity dynamic elbow extensions

2016 ◽  
Vol 121 (2) ◽  
pp. 475-482 ◽  
Author(s):  
Brianna L. Cowling ◽  
Brad Harwood ◽  
David B. Copithorne ◽  
Charles L. Rice
Keyword(s):  
High Intensity ◽  
Peak Power ◽  
Maximum Voluntary Contraction ◽  
Motor Units ◽  
Voluntary Contraction ◽  
Elbow Extension ◽  
Concentric Contractions ◽  
Motor Unit Firing ◽  
Maximal Effort ◽  
Isometric Maximum Voluntary Contraction

Investigations of high-intensity isometric fatiguing protocols report decreases in motor unit firing rates (MUFRs), but little is known regarding changes in MUFRs following fatigue induced by high-intensity dynamic contractions. Our purpose was to evaluate MUFRs of the anconeus (an accessory elbow extensor) and elbow extension power production as a function of time to task failure (TTF) during high-velocity fatiguing concentric contractions against a moderately heavy resistance. Fine-wire intramuscular electrode pairs were inserted into the anconeus to record MUs in 12 male participants (25 ± 3 yr), over repeated sessions on separate days. MUs were tracked throughout a three-stage, varying load dynamic elbow extension protocol designed to extend the task duration for >1 min thereby inducing substantial fatigue. Mean MUFRs and peak power were calculated for three relative time ranges: 0–15% TTF (beginning), 45–60% TTF (middle) and 85–100% TTF (end). Mean duration of the overall fatigue protocol was ∼80 s. Following the protocol, isometric maximum voluntary contraction (MVC), highest velocity at 35% MVC load, and peak power decreased 37, 60, and 64% compared with baseline, respectively. Data from 20 anconeus MUs tracked successfully throughout the protocol indicated a reduction in MUFRs in relation to power loss from 36 Hz/160 W (0–15% TTF) to 28 Hz/97 W (45–60% TTF) to 23 Hz/43 W (85–100% TTF). During these high-intensity maximal effort concentric contractions, anconeus MUFRs decreased substantially (>35%). Although the absolute MUFRs were higher in the present study than those reported previously for other muscles during sustained high-intensity isometric tasks, the relative decrease in MUFRs was similar between the two tasks.

scholarly journals Quantifying Topographical Changes in Muscle Activation: A Statistical Parametric Mapping Approach

Proceedings ◽  
2020 ◽  
Vol 49 (1) ◽  
pp. 71
Author(s):  
Patricio A. Pincheira ◽  
Eduardo Martinez-Valdes ◽  
Carlos De la Fuente ◽  
Felipe Palma ◽  
Oscar Valencia ◽  
...  
Keyword(s):  
Repeated Measures ◽  
Muscle Activation ◽  
Plantar Flexion ◽  
Statistical Parametric Mapping ◽  
High Sensitivity ◽  
Voluntary Contraction ◽  
Medial Gastrocnemius ◽  
Isometric Contractions ◽  
Parametric Mapping ◽  
Repeated Measures Anova

Regional changes in muscle activation occur at different contraction intensities. These changes can be observed with activity maps created with high-density electromyography (HDEMG). When quantifying these changes, statistical parametric mapping (SPM) is a neuroimaging technique that may be used to perform statistical analyses with high sensitivity and spatial resolution. The aim of this study was to identify regional changes in muscle activation at different contraction intensities, comparing SPM and the HDEMG barycenter (centroid). Twelve participants performed plantar flexion isometric contractions at 20%, 40%, and 60% of the maximal voluntary contraction (MVC), while HDEMG was recorded from the medial gastrocnemius. An SPM repeated measures ANOVA design revealed specific mediolateral and cephalocaudal changes in muscle activation with increasing contraction intensities, which were not clearly detected by the variation in the barycenter coordinates. Only SPM revealed statistically significant nonuniform changes in EMG amplitude between all increasing levels of muscle activation.

13C-NMR measurements of muscle glycogen during low-intensity exercise

1991 ◽  
Vol 70 (4) ◽  
pp. 1836-1844 ◽  
Author(s):  
T. B. Price ◽  
D. L. Rothman ◽  
M. J. Avison ◽  
P. Buonamico ◽  
R. G. Shulman
Keyword(s):  
Steady State ◽  
13C Nmr ◽  
Muscle Glycogen ◽  
Plantar Flexion ◽  
Maximum Voluntary Contraction ◽  
Blood Velocity ◽  
Voluntary Contraction ◽  
Low Intensity ◽  
13C Nuclear Magnetic Resonance ◽  
Low Intensity Exercise

Glycogen metabolism in exercising gastrocnemius muscles was examined by natural abundance 13C nuclear magnetic resonance (NMR) spectroscopy. Five-minute 13C-NMR measurement of muscle glycogen had a reproducibility of +/- 6.5% (+/- 4.8 mM). Experiments were performed on healthy fed male and female subjects. Two protocols were followed. 1) Subjects performed plantar flexion from rest at 15, 20, or 25% of maximum voluntary contraction for up to 9 h. 2) Subjects predepleted gastrocnemius glycogen with heavy exercise and then either performed low-intensity exercise as before or rested. Gastrocnemius glycogen was measured by NMR at rest and after each hour of exercise. In some sessions, both the exercised leg and the nonexercised leg were monitored with 13C-NMR. In protocol 1, blood velocity in the femoral artery was similarly assessed with ultrasonography. During low-intensity exercise from rest (protocol 1) muscle glycogen fell to a new steady-state value after several hours and then remained constant despite continued exercise. Mean blood velocity increased ninefold within 2 min of onset of exercise and remained constant thereafter. After predepletion (protocol 2), muscle glycogen was repleted both during low-intensity exercise and at rest. After 1 h the amount of glycogen repletion was greater when coupled with light exercise [48.5 +/- 2.8 mM after 1 h of exercise, 39.7 +/- 1.1 mM after 1 h of rest (P less than 0.05)]. During subsequent light exercise, glycogen reached a steady-state value similar to that obtained in protocol 1, while in resting, recovery glycogen levels continued to increase (+2.7 mM/h) over a 7-h period.(ABSTRACT TRUNCATED AT 250 WORDS)

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