scholarly journals Post‐activation potentiation induced by concentric contractions at three speeds in humans

2021 ◽  
Author(s):  
Alexander M. Zero ◽  
Charles L. Rice
Keyword(s):  
Concentric Contractions

scholarly journals Effects of trunk extensor eccentric exercise on lipid profile and glycaemic response

2020 ◽  
Vol 6 (1) ◽  
pp. e000861
Author(s):  
Ho-Seong Lee ◽  
Takayuki Akimoto ◽  
Ah-Ram Kim
Keyword(s):  
Lipid Profile ◽  
Muscle Soreness ◽  
Blood Lipid ◽  
Eccentric Contraction ◽  
Trunk Muscles ◽  
Eccentric Contractions ◽  
Glycaemic Response ◽  
Concentric Contractions ◽  
Positive Effects ◽  
Trunk Extensor

ObjectivesA number of previous studies reported physiological responses and adaptations after eccentric muscle contraction of limb muscles. In contrast, no study has determined physiological response after eccentric contraction of trunk muscles. The purpose of the present study was to compare the functional and metabolic changes after eccentric or concentric exercises of trunk extensor muscles.MethodsIn this randomised, crossover study, 10 men performed a single bout of 50 maximal voluntary concentric and eccentric contractions of the trunk extensor with an interval of 2 weeks between bouts. The activities of the paraspinal muscles were recorded during concentric and eccentric contractions. Muscle soreness, muscle function, blood lipid profiles and glycaemic responses were measured before, immediately after and at 24, 48, 72 and 96 hours after each bout.ResultsThe lumbar multifidus and iliocostalis lumborum activities during eccentric contractions were significantly higher than those during concentric contractions (p<0.05). The maximal strength and muscle endurance of the trunk extensor were not decreased even after the eccentric contractions. Compared with concentric contractions, muscle soreness was significantly increased at 24, 48, 72 and 96 hours after eccentric contractions (p<0.05). The TG, TC and LDL-C were significantly lower at 48, 72 and 96 hours after eccentric contractions (p<0.05), while blood glucose levels and HOMA-IR were significantly greater at 48 and 72 hours after eccentric contractions (p<0.05).ConclusionThis study indicated that eccentric contractions of the trunk extensor had positive effects on the lipid profile and the glycaemic response.

scholarly journals Quadriceps activation during maximal isometric and isokinetic contractions: The minimal real difference and its implications

2020 ◽  
pp. 1-13
Author(s):  
Luigi Catino ◽  
Chiara Malloggi ◽  
Stefano Scarano ◽  
Valeria Cerina ◽  
Viviana Rota ◽  
...  
Keyword(s):  
Intraclass Correlation ◽  
Correlation Coefficients ◽  
Voluntary Activation ◽  
Real Difference ◽  
Concentric Contractions ◽  
Rehabilitation Programs ◽  
Logit Transformation ◽  
Isokinetic Contractions ◽  
Electrical Stimuli ◽  
Voluntary Contractions

BACKGROUND: A method of measurement of voluntary activation (VA, percent of full muscle recruitment) during isometric and isokinetic concentric contractions of the quadriceps femoris (QF) at 60∘/s and 120∘/s was previously validated. OBJECTIVE: This study aimed to quantify the test-retest minimal real difference (MRD) of VA during isometric (ISOM) and isokinetic concentric contractions of QF (100∘/s, ISOK) in a sample of healthy individuals. METHODS: VA was measured through the interpolated twitch technique. Pairs of electrical stimuli were delivered to the QF at 40∘ of knee flexion during maximal voluntary contractions. Twenty-five healthy participants (20–38 years, 12 women, 13 men) completed two testing sessions with a 14-day interval. VA values were linearized through logit transformation (VAl). The MRD was estimated from intraclass correlation coefficients (model 2.1). RESULTS: The VA (median, range) was 84.20% (38.2–99.9%) in ISOM and 94.22% (33.8-100%) in ISOK. MRD was 0.78 and 1.12 logit for ISOM and ISOK, respectively. As an example, in terms of percent VA these values correspond to a change from 76% to 95% and from 79% to 98% in ISOM and in ISOK, respectively. CONCLUSIONS: The provided MRD values allow to detect significant individual changes in VA, as expected after training and rehabilitation programs.

scholarly journals Kinesio Taping Does Not Alter Quadriceps Isokinetic Strength and Power in Healthy Nonathletic Men: A Prospective Crossover Study

2015 ◽  
Vol 2015 ◽  
pp. 1-5 ◽  
Author(s):  
Paweł Korman ◽  
Anna Straburzyńska-Lupa ◽  
Radosław Rutkowski ◽  
Jakub Gruszczyński ◽  
Jacek Lewandowski ◽  
...  
Keyword(s):  
Repeated Measures ◽  
Peak Torque ◽  
Quadriceps Muscle ◽  
Knee Extensors ◽  
Isokinetic Strength ◽  
Acute Effects ◽  
Isokinetic Dynamometer ◽  
Mean Power ◽  
Concentric Contractions ◽  
Kinesio Taping

Objectives. The effects of Kinesio Taping (KT) on muscular performance remain largely unclear. This study aimed to investigate the acute effects of KT on the maximum concentric and eccentric quadriceps isokinetic strength.Study Design. This is a single-blinded, placebo crossover, repeated measures study.Methods. Maximum isokinetic concentric/eccentric extension torque, work, and power were assessed by an isokinetic dynamometer without taping (NT) and with KT or placebo taping (PT) in 17 healthy young men. Repeated measures one-way analysis of variance (ANOVA) was used for statistical analyses.Results. Testing concentric contractions at 60°/s or 180°/s isokinetic speed, no significant differences in peak torque (Nm), total work (J), or mean power (W) were noted among the application modes under different conditions. Testing eccentric contractions at 30°/s or 60°/s isokinetic speed, no significant differences in mentioned parameters were noted, respectively. KT on the quadriceps neither decreased nor increased muscle strength in the participants.Conclusion. KT application onto the skin overlying the quadriceps muscle does not enhance the strength or power of knee extensors in healthy men.

Effect of quadriceps femoris muscle length on neural activation during isometric and concentric contractions

2003 ◽  
Vol 94 (3) ◽  
pp. 983-990 ◽  
Author(s):  
Nicolas Babault ◽  
Michel Pousson ◽  
Anne Michaut ◽  
Jacques Van Hoecke
Keyword(s):  
Knee Flexion ◽  
Muscle Length ◽  
Isometric Contractions ◽  
Neural Activation ◽  
Length Effect ◽  
Neural Drive ◽  
Concentric Contractions ◽  
Twitch Interpolation ◽  
Predominant Effect ◽  
Femoris Muscle

The effect of muscle length on neural drive (here termed “neural activation”) was investigated from electromyographic activities and activation levels (twitch interpolation). The neural activation was measured in nine men during isometric and concentric (30 and 120°/s) knee extensions for three muscle lengths (35, 55, and 75° knee flexion, i.e., shortened, intermediate, and lengthened muscles, respectively). Long (76°), medium (56°), and short (36°) ranges of motion were used to investigate the effect of the duration of concentric contraction. Neural activation was found to depend on muscle length. Reducing the duration of contraction had no effect. Neural activation was higher with short muscle length during isometric contractions and was weaker for shortened than for intermediate and lengthened muscles performing 120°/s concentric contractions. Muscle length had no effect on 30°/s concentric neural activation. Peripheral mechanisms and discharge properties of the motoneurons could partly explain the observed differences in the muscle length effect. We thus conclude that muscle length has a predominant effect on neural activation that would modulate the angular velocity dependency.

Intent-Related Differences in Surface EMG of Maximum Eccentric and Concentric Contractions

2003 ◽  
Vol 19 (2) ◽  
pp. 99-105 ◽  
Author(s):  
Mark D. Grabiner ◽  
Tammy M. Owings
Keyword(s):  
Muscle Activation ◽  
Vastus Lateralis ◽  
Knee Extensor ◽  
Eccentric Contraction ◽  
Surface Emg ◽  
Vastus Lateralis Muscle ◽  
Concentric Contractions ◽  
Concentric Contraction ◽  
Contraction Condition ◽  
The Difference

For this study it was hypothesized that when participants intended to perform a maximum voluntary concentric (or eccentric) contraction but had an eccentric (or concentric) contraction imposed upon them, the initial EMG measured during the isometric phase preceding the onset of the dynamometer motion would reflect the intended contraction condition. The surface EMG of the vastus lateralis muscle was measured in 24 participants performing isokinetic concentric and eccentric maximum voluntary knee extensor contractions. The contractions were initiated from rest and from the same knee flexion angle and required the same level of external force to trigger the onset of dynamometer motion. Vastus lateralis EMG were quantified during the isometric phase preceding the onset of the dynamometer motion. When participants intended to perform a concentric contraction but had an eccentric contraction imposed upon them, the initial EMG resembled that of a concentric contraction. When they intended to perform an eccentric contraction but had a concentric contraction imposed upon them, the initial EMG resembled that of an eccentric contraction. Overall, the difference between concentric and eccentric contractions observed during the period of theinitialmuscle activation implies that descending signals include information that distinguishes between eccentric and concentric contractions.

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 Measuring voluntary activation of the Quadriceps femoris during isokinetic concentric contractions

2019 ◽  
Vol 27 (2) ◽  
pp. 125-134 ◽  
Author(s):  
Chiara Malloggi ◽  
Luigi Catino ◽  
Viviana Rota ◽  
Stefano Scarano ◽  
Luigi Tesio
Keyword(s):  
Quadriceps Femoris ◽  
Voluntary Activation ◽  
Concentric Contractions

A Comparison between Two Models of Shoulder Muscle Force Estimation

2009 ◽  
Vol 25 (1) ◽  
pp. 43-53 ◽  
Author(s):  
Daniel Cury Ribeiro ◽  
Joelly Mahnic de Toledo ◽  
Roberto Costa Krug ◽  
Jefferson Fagundes Loss
Keyword(s):  
Latissimus Dorsi ◽  
Reasonable Agreement ◽  
Muscle Force ◽  
Poor Correlation ◽  
Shoulder Injuries ◽  
Force Estimation ◽  
Concentric Contractions ◽  
Shoulder Muscle ◽  
Teres Major ◽  
The Difference

Shoulder injuries are often related to rotator cuff muscles. Although there are various models for muscle force estimation, it is difficult to ensure that the results obtained with such models are reliable. The aim of the current study was to compare two models of muscle force estimation. Eight subjects, seven male and one female (mean age of 24 yr; mean height of 1.83 m), performed five isokinetic maximum concentric contractions of internal and external shoulder rotation. Two models with different algorithms were used. In both, the input data consisted of the measured internal rotation moment. Comparisons were made between the difference and the average results obtained with each model of muscle force estimation. There was reasonable agreement among the results for force between the two models for subscapularis, pectoralis major, and anterior deltoideus muscles results. Conversely, poor correlation was found for the latissimus dorsi, teres major, and middle deltoid. These results suggest that the algorithm structure might have a strong effect on muscle force estimation results.

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