scholarly journals Acute Effect of High-Intensity Climbing on Performance and Muscle Oxygenation in Elite Climbers

2021 ◽  
Author(s):  
Andri Feldmann ◽  
Remo Lehmann ◽  
Frieder Wittmann ◽  
Peter Wolf ◽  
Jiří Baláš ◽  
...  
Keyword(s):  
High Intensity ◽  
Strong Association ◽  
Maximum Voluntary Contraction ◽  
Force Production ◽  
Oxidative Capacity ◽  
Acute Effect ◽  
Voluntary Contraction ◽  
Muscle Oxygenation ◽  
Control Group ◽  
Endurance Tests

AbstractHigh-intensity training (HIT) is known to have deteriorating effects on performance which manifest in various physiological changes such as lowered force production and oxidative capacity. However, the effect of HIT in climbing on finger flexor performance has not been investigated yet. Twenty-one climbers partook in an intervention study with three assessment time points: pre-HIT, post-HIT, and 24-h post-HIT. The HIT involved four five-minute exhaustive climbing tasks. Eight climbers were assigned to a control group. Assessments consisted of three finger flexor tests: maximum voluntary contraction (MVC), sustained contraction (SCT), and intermittent contraction tests (ICT). During the SCT muscle oxygenation (SmO2) metrics were collected via NIRS sensors on the forearm. The HIT had significant deteriorating effects on all force production metrics (MVC − 18%, SCT − 55%, ICT − 59%). Post-24 h showed significant recovery, which was less pronounced for the endurance tests (MVC − 3%, SCT − 16%, ICT − 22%). SmO2 metrics provided similar results for the SCT with medium to large effect sizes. Minimally attainable SmO2 and resting SmO2 both showed moderate negative correlations with pre-HIT force production respectively; r = − 0.41, P = 0.102; r = − 0.361, P = 0.154. A strong association was found between a loss of force production and change in minimally attainable SmO2 (r = − 0.734, P = 0.016). This study presents novel findings on the deteriorating effects of HIT on finger flexor performance and their oxidative capacity. Specifically, the divergent results between strength and endurance tests should be of interest to coaches and athletes when assessing athlete readiness.

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.

scholarly journals Acute effect of tendon vibration applied during isometric contraction at two knee angles on maximal knee extension force production

PLoS ONE ◽  
2020 ◽  
Vol 15 (11) ◽  
pp. e0242324
Author(s):  
Jonathan Harnie ◽  
Thomas Cattagni ◽  
Christophe Cornu ◽  
Peter McNair ◽  
Marc Jubeau
Keyword(s):  
Isometric Contraction ◽  
Vastus Lateralis ◽  
Force Production ◽  
Knee Extensor ◽  
Acute Effect ◽  
Knee Extension ◽  
Voluntary Contraction ◽  
Voluntary Activation ◽  
Tendon Vibration ◽  
Knee Angle

The aim of the current study was to investigate the effect of a single session of prolonged tendon vibration combined with low submaximal isometric contraction on maximal motor performance. Thirty-two young sedentary adults were assigned into two groups that differed based on the knee angle tested: 90° or 150° (180° = full knee extension). Participants performed two fatigue-inducing exercise protocols: one with three 10 min submaximal (10% of maximal voluntary contraction) knee extensor contractions and patellar tendon vibration (80 Hz) another with submaximal knee extensor contractions only. Before and after each fatigue protocol, maximal voluntary isometric contractions (MVC), voluntary activation level (assessed by the twitch interpolation technique), peak-to-peak amplitude of maximum compound action potentials of vastus medialis and vastus lateralis (assessed by electromyography with the use of electrical nerve stimulation), peak twitch amplitude and peak doublet force were measured. The knee extensor fatigue was significantly (P<0.05) greater in the 90° knee angle group (-20.6% MVC force, P<0.05) than the 150° knee angle group (-8.3% MVC force, P = 0.062). Both peripheral and central alterations could explain the reduction in MVC force at 90° knee angle. However, tendon vibration added to isometric contraction did not exacerbate the reduction in MVC force. These results clearly demonstrate that acute infrapatellar tendon vibration using a commercial apparatus operating at optimal conditions (i.e. contracted and stretched muscle) does not appear to induce knee extensor neuromuscular fatigue in young sedentary subjects.

A STUDY OF MODELS FOR HANDGRIP FORCE PREDICTION FROM SURFACE ELECTROMYOGRAPHY OF EXTENSOR MUSCLE

2009 ◽  
Vol 21 (02) ◽  
pp. 81-88 ◽  
Author(s):  
Wensheng Hou ◽  
Xiaolin Zheng ◽  
Yingtao Jiang ◽  
Jun Zheng ◽  
Chenglin Peng ◽  
...  
Keyword(s):  
Root Mean Square ◽  
Surface Electromyography ◽  
Random Sequence ◽  
Maximum Voluntary Contraction ◽  
Force Production ◽  
Voluntary Contraction ◽  
Mean Square ◽  
Force Level ◽  
Force Output ◽  
Mean Square Errors

Force production involves the coordination of multiple muscles, and the produced force levels can be attributed to the electrophysiology activities of those related muscles. This study is designed to explore the activity modes of extensor carpi radialis longus (ECRL) using surface electromyography (sEMG) at the presence of different handgrip force levels. We attempt to compare the performance of both the linear and nonlinear models for estimating handgrip forces. To achieve this goal, a pseudo-random sequence of handgrip tasks with well controlled force ranges is defined for calibration. Eight subjects (all university students, five males, and three females) have been recruited to conduct both calibration and voluntary trials. In each trial, sEMG signals have been acquired and preprocessed with Root–Mean–Square (RMS) method. The preprocessed signals are then normalized with amplitude value of Maximum Voluntary Contraction (MVC)-related sEMG. With the sEMG data from calibration trials, three models, Linear, Power, and Logarithmic, are developed to correlate the handgrip force output with the sEMG activities of ECRL. These three models are subsequently employed to estimate the handgrip force production of voluntary trials. For different models, the Root–Mean–Square–Errors (RMSEs) of the estimated force output for all the voluntary trials are statistically compared in different force ranges. The results show that the three models have different performance in different force ranges. Linear model is suitable for moderate force level (30%–50% MVC), whereas a nonlinear model is more accurate in the weak force level (Power model, 10%–30% MVC) or the strong force level (Logarithmic model, 50%–80% MVC).

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 Impaired dynamic cerebral autoregulation at rest and during isometric exercise in type 2 diabetes patients

2015 ◽  
Vol 308 (7) ◽  
pp. H681-H687 ◽  
Author(s):  
Lauro C. Vianna ◽  
Shekhar H. Deo ◽  
Areum K. Jensen ◽  
Seth W. Holwerda ◽  
Matthew C. Zimmerman ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Type 2 Diabetes ◽  
High Intensity ◽  
Cerebral Autoregulation ◽  
Maximum Voluntary Contraction ◽  
Voluntary Contraction ◽  
Isometric Handgrip ◽  
Systemic Oxidative Stress ◽  
Dynamic Cerebral Autoregulation

Type 2 diabetes mellitus patients (T2D) have elevated risk of stroke, suggesting that cerebrovascular function is impaired. Herein, we examined dynamic cerebral autoregulation (CA) at rest and during exercise in T2D patients and determined whether underlying systemic oxidative stress is associated with impairments in CA. Middle cerebral artery blood velocity and arterial blood pressure (BP) were measured at rest and during 2-min bouts of low- and high-intensity isometric handgrip performed at 20% and 40% maximum voluntary contraction, respectively, in seven normotensive and eight hypertensive T2D patients and eight healthy controls. Dynamic CA was estimated using the rate of regulation (RoR). Total reactive oxygen species (ROS) and superoxide levels were measured at rest. There were no differences in RoR at rest or during exercise between normotensive and hypertensive T2D patients. However, when compared with controls, T2D patients exhibited lower RoR at rest and during low-intensity handgrip indicating impaired dynamic CA. Moreover, the RoR was further reduced by 29 ± 4% during high-intensity handgrip in T2D patients (0.307 ± 0.012/s rest vs. 0.220 ± 0.014/s high intensity; P < 0.01), although well maintained in controls. T2D patients demonstrated greater baseline total ROS and superoxide compared with controls, both of which were negatively related to RoR during handgrip (e.g., total ROS: r = −0.71, P < 0.05; 40% maximum voluntary contraction). Collectively, these data demonstrate impaired dynamic CA at rest and during isometric handgrip in T2D patients, which may be, in part, related to greater underlying systemic oxidative stress. Additionally, dynamic CA is blunted further with high intensity isometric contractions potentially placing T2D patients at greater risk for cerebral events during such activities.

scholarly journals Crossfit Practice: An Electromyographic Analysis of Masticatory Muscles

2020 ◽  
Author(s):  
Nayara Soares da Silva ◽  
Marcelo Palinkas ◽  
Evandro Marianetti Fioco ◽  
Edson Donizetti Verri ◽  
Saulo César Vallin Fabrin ◽  
...  
Keyword(s):  
Maximum Voluntary Contraction ◽  
Masticatory Muscles ◽  
Voluntary Contraction ◽  
Control Group ◽  
Electromyographic Activity ◽  
Physical Conditioning ◽  
Striated Muscles ◽  
Functional Changes ◽  
Significant Difference ◽  
The Impact

Abstract Background: CrossFit is a regular high-intensity physical conditioning exercise for skeletal striated muscles, which promotes functional changes in the human body. The aim of this study was to investigate the impact of CrossFit exercise on the electromyographic activity of the masseter and temporalis muscles. Methods: Forty participants were divided into two groups: athletes who practiced CrossFit (n=20) and controls who did not practice sports (n=20). The electromyographic activities of the masseter and temporalis muscles were measured using mandibular tasks at rest, protrusion, right laterality, left laterality, and dental clenching in maximum voluntary contraction and habitual chewing of peanuts and raisins. Both the groups were matched for age, sex, and body mass index. The data were analyzed using the t-test with a 5% significance level. Results: Reduced electromyographic activities were found in all mandibular tasks in the CrossFit group than in the control group, with a significant difference for the right masseter (p=0.01), left masseter (p=0.001), and left temporal muscles (p=0.001) at mandibular rest; right (p=0.001) and left (p=0.001) masseter in chewing of peanuts. Conclusion: The results of this study suggest that CrossFit promotes positive changes in electromyographic activity of the masticatory muscles, especially in the mandibular rest and chewing of hard food. CrossFit exercise practiced within the appropriate technical protocols improves masticatory muscle function.

Factors Affecting Force Loss With Prolonged Stretching

2001 ◽  
Vol 26 (3) ◽  
pp. 262-272 ◽  
Author(s):  
David G. Behm ◽  
Duane C. Button ◽  
Jeremy C. Butt
Keyword(s):  
Maximal Voluntary Contraction ◽  
Muscle Activation ◽  
Maximum Voluntary Contraction ◽  
Voluntary Contraction ◽  
Control Group ◽  
Tetanic Force ◽  
Factors Affecting ◽  
Passive Stretching ◽  
Interpolated Twitch Technique ◽  
Muscle Compliance

The purpose of this study was to investigate factors underlying the force loss occurring after prolonged, static, passive stretching. Subjects were tested before and 5-10 min following 20 min of static, passive stretching of the quadriceps (N = 12) or a similar period of no stretch (control, N = 6). Measurements included isometric maximal voluntary contraction (MVC) force, surface integrated electromyographic (iEMG) activity of the quadriceps and hamstrings, evoked contractile properties (twitch and tetanic force), and quadriceps inactivation as measured by the interpolated twitch technique (ITT). Following stretching, there was a significant 12% decrement in MVC with no significant changes in the control group. Muscle inactivation as measured by the ITT and iEMG increased by 2.8% and 20.2%, respectively. While twitch forces significantly decreased 11.7%, there was no change in tetanic force post-stretch. Although possible increases in muscle compliance affected twitch force, a lack of tetanic force change would suggest that post-stretch force decrements are more affected by muscle inactivation than changes in muscle elasticity. Key Words: antagonist, electromyography, maximum voluntary contraction, muscle activation, twitch, tetanus

scholarly journals Comparing neck extensor muscle function in asymptomatic Canadian adults and adults with tension-type headache: a cross-sectional study

BMJ Open ◽  
2019 ◽  
Vol 9 (5) ◽  
pp. e020984 ◽  
Author(s):  
Andrée-Anne Marchand ◽  
Mariève Houle ◽  
Marie-Pier Girard ◽  
Marie-Ève Hébert ◽  
Martin Descarreaux
Keyword(s):  
Muscle Fatigue ◽  
Maximum Voluntary Contraction ◽  
Tension Type Headache ◽  
Voluntary Contraction ◽  
Extensor Muscle ◽  
Control Group ◽  
Physical Parameters ◽  
Cross Sectional ◽  
Neck Extension ◽  
Type Headache

AimTo further the understanding of the pathophysiological mechanisms underlying tension-type headache (TTH) by comparing the endurance and strength of neck extensor muscles under acute muscle fatigue in participants with TTH and asymptomatic participants.MethodsWe conducted a cross-sectional analysis of neck extensor muscle performance. Asymptomatic participants and participants with TTH were recruited via social media platforms and from the Université du Québec à Trois-Rivières community and employees. A total of 44 participants with TTH and 40 asymptomatic participants took part in an isometric neck extensor endurance task performed at 60% of their maximum voluntary contraction. Inclusion criteria for the headache group were to be older than 18 years old and to fulfil the International Headache Society classification’s criteria for either frequent episodic or chronic TTH. Clinical (self-efficacy, anxiety, neck disability and kinesiophobia) and physical parameters (neck extensors maximum voluntary contraction, endurance time, muscle fatigue) as well as characteristics of headache episodes (intensity, frequency and associated disability) were collected for all participants. Surface electromyography was used to document upper trapezius, splenius capitis and sternocleidomastoids muscle activity and muscle fatigue.ResultsBoth groups displayed similar neck extensor muscle endurance capacity with a mean difference of 6.2 s (p>0.05) in favour of the control group (control=68.1±32.3; TTH=61.9±20.1). Similarly, participants in the headache group showed comparable neck extensor muscle strength (95.9±30.4 N) to the control group (111.3±38.7 N). Among participants with TTH, those scoring as severely incapacitated by headaches were the ones with higher neck-related disability (F[1,44]=10.77; p=0.002), the more frequent headache episodes (F[1,44]=6.70; p=0.01) and higher maximum headache intensity (F[1,44]=10.81; p=0.002).ConclusionA fatigue task consisting of isometric neck extension cannot efficiently differentiate participants with TTH from asymptomatic participants.

scholarly journals Nеw tесhniquеs for physiсal rеhabilitation of powеr sports athlеtеs with artеrial hypеrtеnsion: a randomizеd сontrollеd trial

2020 ◽  
Vol 97 (3) ◽  
pp. 76-82
Author(s):  
A.B. Miroshnikov ◽  
A.V. Smolеnskiy ◽  
A.D. Formеnov
Keyword(s):  
Blood Pressure ◽  
High Intensity ◽  
Blood Pressure Measurement ◽  
Clinical Manifestations ◽  
Oxidative Capacity ◽  
Main Group ◽  
Physical Rehabilitation ◽  
Control Group ◽  
Heavy Weight ◽  
The Impact

Essential hypertension is a frequent diagnosis in power sports athletes, heavy weight categories. The aim of the study: To evaluate the impact of high-intensity aerobic work on blood pressure and oxidative abilities of hypertensive athletes of power sports, heavy weight categories. Rеsеarсh mеthods: Examination and physical rehabilitation were conducted in 55 hypertensive representatives of power sports, heavy weight categories comparable in age, sex and main clinical manifestations. Athletes were randomized into two groups: the main group (n=35) and the control group (n=20). Athletes of the main group were trained for 180 days (3 times a week) on an ergometer using a high-intensity interval protocol, while the control group participants were trained for 180 days (3 times a week) using their traditional power protocol. The tasks were performed using the following methods: examination, polling, gasometric analysis, triple blood pressure measurement, muscle tissue oxygenation level measurement and mathematical statistics methods. Rеsults: After 180 days of physical rehabilitation, the participants in the main group had a 148% reduction in oxygen oxygenation, an increase in capacity and working time at maximum oxygen consumption, and a reliable decrease in blood pressure: systolic blood pressure by 8.0%, diastolic blood pressure by 10.8%. Сonсlusion: Our protocol for physical rehabilitation of power sports athletes allows us to effectively and safely influence the oxidative capacity of working muscles and blood pressure.

scholarly journals Maximum voluntary muscle contraction and fatigue in multibacillary leprosy

2020 ◽  
Vol 33 ◽  
Author(s):  
Luciane Lobato Sobral ◽  
Marcio Clementino de Souza Santos ◽  
Larissa Salgado de Oliveira Rocha ◽  
Bianca Callegari ◽  
Givago da Silva Souza ◽  
...  
Keyword(s):  
Muscle Contraction ◽  
Fatigue Test ◽  
Healthy Subjects ◽  
Maximum Voluntary Contraction ◽  
Onset Time ◽  
Voluntary Contraction ◽  
Control Group ◽  
Time Interval ◽  
Leprosy Patients ◽  
Multibacillary Leprosy

Abstract Introduction: The impairment of muscle strength and fatigue in leprosy remains a problem that requires careful attention to avoid or minimize its progression, as well as prevention of disabilities and deformities. Objective: To investigate the maximum voluntary contraction and time to muscle fatigue in leprosy patients. Method: A total of 21 leprosy patients and 21 healthy subjects completed the sample. The method used to determine the maximum voluntary contraction (MVC) of the handgrip followed the recommendation of the American Society of Hand Therapists with the use of a hydraulic hand grip dynamometer. The test was performed three times with each hand, with a time interval of 60 seconds between successive trials. The subject was instructed to perform a maximal isometric force against the dynamometer for 5 seconds. The peaks were recorded and used for the fatigue test. For the fatigue test, we recorded the electromyogram of the forearm muscles to offline determine the onset time for the muscle contraction (14 bits, Miograph 2 USB®, Miotec, Brazil). Results: Leprosy patients had lower MVC compared with healthy subjects (p > 0.05), both in the dominant and the non-dominant hands. The time to fatigue in the leprosy and control groups was similar (p < 0.05). We observed that leprosy patients had more contractions than the healthy subjects (22.6 ± 11.8 contractions for the leprosy group vs. 12.3 ± 6.9 contractions for the control group, p > 0.05). Conclusion: Multibacillary leprosy patients lost muscle force without modifying the resistance to fatigue.

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