scholarly journals Potentiation and Electrical Stimulus Frequency During Self-Paced Exercise and Recovery

2014 ◽  
Vol 42 (1) ◽  
pp. 91-101 ◽  
Author(s):  
Christian Froyd ◽  
Fernando G. Beltrami ◽  
Jørgen Jensen ◽  
Guillaume Y. Millet ◽  
Timothy David Noakes
Keyword(s):  
Stimulus Frequency ◽  
Time Trial ◽  
Peak Torque ◽  
Electrical Stimulus ◽  
Voluntary Contraction ◽  
Peripheral Fatigue ◽  
Paired Stimuli ◽  
Torque Measurements ◽  
Before And After ◽  
The Right

Abstract The aim of this study was to investigate the effect of potentiation on stimulation-induced muscle function during and after an intense bout of self-paced dynamic exercise. Ten active subjects performed a time trial involving repetitive concentric extension-flexion of the right knee using a Biodex dynamometer. Electrical stimulation before and after a 5 s maximal isometric voluntary contraction was performed before the start of the time trial and immediately (< 5 s) after each 20% of the time trial as well as 1, 2, 4 and 8 min after time trial termination. Potentiation was observed before the time trial and as early as 1-2 min after the time trial, but no potentiation was detected during or immediately after the time trial for neither single or paired stimuli. At termination of the time trial, “potentiated” peak torque was significantly more reduced than “unpotentiated" peak torque for single stimulus (-65 ± 10% and -42 ± 18%, respectively) and paired stimuli at 100 Hz (-51 ± 10% and -33 ± 15%, respectively). Faster recovery for “potentiated” compared to “unpotentiated” peak torque indicate that potentiate peak torque measurements or delay the post-exercise measurements more than a few seconds, will underestimate peripheral fatigue. In conclusion, the potentiation after maximal contraction disappears during intense exercise. Whether the muscle is already potentiated during intense contraction or fatiguing mechanisms inhibits potentiation remains to be clarified

Strength training the free limb attenuates strength loss during unilateral immobilization

2009 ◽  
Vol 106 (3) ◽  
pp. 830-836 ◽  
Author(s):  
Jonathan P. Farthing ◽  
Joel R. Krentz ◽  
Charlene R. A. Magnus
Keyword(s):  
Strength Training ◽  
Muscle Activation ◽  
Muscle Thickness ◽  
Strength Loss ◽  
Peak Torque ◽  
Ulnar Deviation ◽  
Before And After ◽  
Cross Education ◽  
The Right ◽  
Arm Strength

The objective was to determine if strength training the free limb during a 3-wk period of unilateral immobilization attenuates strength loss in the immobilized limb through cross-education. Thirty right-handed participants were assigned to three groups. One group ( n = 10) wore a cast and trained the free arm (Cast-Train). A second group ( n = 10) wore a cast and did not train (Cast). A third group ( n = 10) received no treatment (control). Casts were applied to the nondominant (left) wrist and hand by a physician. Strength training was maximal isometric ulnar deviation (right hand) 5 days/wk. Peak torque (dynamometer), electromyography (EMG), and muscle thickness (ultrasound) were assessed in both arms before and after the intervention. Cast-Train improved right arm strength [14.3 (SD 5.0) to 17.7 (SD 4.8) N·m; P < 0.05] with no significant muscle hypertrophy [3.73 (SD 0.43) to 3.84 (SD 0.52) cm; P = 0.09]. The immobilized arm of Cast-Train did not change in strength [13.9 (SD 4.3) to 14.2 (SD 4.6) N·m] or muscle thickness [3.61 (SD 0.51) to 3.57 (SD 0.43) cm]. The immobilized arm of Cast decreased in strength [12.2 (SD 3.8) to 10.4 (SD 2.5) N·m; P < 0.05] and muscle thickness [3.47 (SD 0.59) to 3.32 (SD 0.55) cm; P < 0.05]. Control showed no changes in the right arm [strength: 15.3 (SD 6.1) to 14.3 (SD 5.8) N·m; muscle thickness: 3.57 (SD 0.68) to 3.52 (SD 0.75) cm] or left arm [strength: 14.5 (SD 5.3) to 13.7 (SD 6.1) N·m; muscle thickness: 3.55 (SD 0.77) to 3.51 (SD 0.70) cm]. Agonist muscle activation remained unchanged after the intervention for both arms [right: 302 (SD 188) to 314 (SD 176) μV; left: 261 (SD 139) to 288 (SD 151) μV] with no group differences. Strength training of the free limb attenuated strength loss in the immobilized limb during unilateral immobilization. Strength training may have prevented muscle atrophy in the immobilized limb.

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 Effects of an increase in intensity during tapering on 1500-m running performance

2019 ◽  
Vol 44 (7) ◽  
pp. 783-790
Author(s):  
Kate L. Spilsbury ◽  
Myra A. Nimmo ◽  
Barry W. Fudge ◽  
Jamie S.M. Pringle ◽  
Mark W. Orme ◽  
...  
Keyword(s):  
Prediction Models ◽  
Training Session ◽  
Time Trial ◽  
Interval Training ◽  
Voluntary Contraction ◽  
Distance Runners ◽  
Running Performance ◽  
Before And After ◽  
Trained Runners ◽  
Regular Training

We examined the effect of completing the final interval training session during a taper at either (i) race pace (RP) or (ii) faster than RP on 1500-m running performance and neuromuscular performance. Ten trained runners (age, 21.7 ± 3.0 years; height, 182.9 ± 7.0 cm; body mass, 73.4 ± 6.8 kg; and personal best 1500-m time, 4:17.5 ± 0:26.9 min) completed 2 conditions consisting of 7 days of regular training and a 7-day taper, separated by 3 weeks of training. In 1 condition, the taper was prescribed using prediction models based on the practices of elite British middle-distance runners, with the intensity of the final interval session being equal to 1500-m RP. The taper was repeated in the high-intensity (HI) condition, with the exception that the final interval session was completed at 115% of 1500-m RP. A 1500-m treadmill time trial and measures of maximal voluntary contraction (MVC) and rate of force development (RFD) were completed before and after regular training and tapering. Performance was most likely improved after RP (mean ± 90% confidence limits, 10.1 ± 1.6 s), and possibly beneficial after HI (4.2 ± 12.0 s). Both MVC force (p = 0.002) and RFD (p = 0.02) were improved after tapering, without differences between conditions. An RP taper based on the practices of elite middle-distance runners is recommended to improve performance in young, subelite runners. The effect of this strategy with an increase in interval intensity is highly variable and should be implemented with caution.

scholarly journals Effect of Acute Static Stretching on the Activation Patterns Using High-Density Surface Electromyography of the Gastrocnemius Muscle during Ramp-Up Task

Sensors ◽  
2021 ◽  
Vol 21 (14) ◽  
pp. 4841
Author(s):  
Noriaki Maeda ◽  
Makoto Komiya ◽  
Yuichi Nishikawa ◽  
Masanori Morikawa ◽  
Shogo Tsutsumi ◽  
...  
Keyword(s):  
Motor Unit ◽  
Muscle Activation ◽  
Gastrocnemius Muscle ◽  
Peak Torque ◽  
Voluntary Contraction ◽  
Motor Unit Recruitment ◽  
Static Stretching ◽  
Activation Patterns ◽  
Muscle Activation Patterns ◽  
Before And After

This study aimed to evaluate motor unit recruitment during submaximal voluntary ramp contraction in the medial head of the gastrocnemius muscle (MG) by high-density spatial electromyography (SEMG) before and after static stretching (SS) in healthy young adults. SS for gastrocnemius was performed in 15 healthy participants for 2 min. Normalized peak torque by bodyweight of the plantar flexor, muscle activity at peak torque, and muscle activation patterns during ramp-up task were evaluated before and after SS. Motor unit recruitment during the submaximal voluntary contraction of the MG was measured using SEMG when performing submaximal ramp contractions during isometric ankle plantar flexion from 30 to 80% of the maximum voluntary contraction (MVC). To evaluate the changes in the potential distribution of SEMG, the root mean square (RMS), modified entropy, and coefficient of variation (CV) were calculated from the dense surface EMG data when 10% of the MVC force was applied. Muscle activation patterns during the 30 to 80% of MVC submaximal voluntary contraction tasks were significantly changed from 50 to 70% of MVC after SS when compared to before. The variations in motor unit recruitment after SS indicate diverse motor unit recruitments and inhomogeneous muscle activities, which may adversely affect the performance of sports activities.

scholarly journals Strength of the Shoulder Rotators in Second-League Volleyball Players

2015 ◽  
Vol 22 (4) ◽  
pp. 215-218
Author(s):  
Aneta Popieluch ◽  
Michał Staniszewski ◽  
Michał Wychowański
Keyword(s):  
Maximal Voluntary Contraction ◽  
Peak Torque ◽  
Voluntary Contraction ◽  
Statistical Testing ◽  
Control Group ◽  
Horizontal Position ◽  
Left Limb ◽  
Volleyball Players ◽  
Torque Values ◽  
The Right

AbstractIntroduction.The main aim of the study was to assess the strength of the shoulder rotator muscles of a group of second-league volleyball players. These muscles are assumed to have a crucial impact on attack effectiveness in volleyball. Strength was assessed based on peak torque values obtained for the rotator muscles measured using the maximal voluntary contraction (MVC) method. Torque was measured in both limbs and the differences between the two limbs were examined. The torque values obtained for the volleyball players were also compared against those measured in a group of students who had never trained any sports.Material and methods.The study involved 20 students (mean age = 20 ± 1 years) who played in the second league when the study was conducted. Their results were compared with those of a control group consisting of 30 students (mean age = 20 ± 1 years) who had not trained any sports. Peak torque of the shoulder rotator muscles was measured during external and internal rotation of the shoulder in isometric conditions. The assessment was performed on a special measuring station with the forearm in a vertical and horizontal position. The following basic statistics were calculated for the torque values obtained in the measurement: the mean, standard deviation, minimum value, and maximum value. The data were then subjected to statistical testing.Results.Compared to the students, the volleyball players had higher torque values of the internal and external rotators of the right and left shoulders, in both positions of the forearm. When the results obtained for the right and left limbs were compared for the group of volleyball players, it was found that the torque values for the right limb, which was the dominant limb, were significantly higher than those recorded for the left limb. The study also showed that the position of the forearm had an impact on torque values: when the forearm was in a horizontal position, higher mean values were obtained for the external rotators of the right (p < 0.05) and left (p < 0.01) limbs, and when it was in a vertical one, the internal rotators were stronger compared to the external rotators.Conclusions.The shoulder rotator muscles of the volleyball players were found to be considerably stronger than those of the students, and the rotators of the dominant limb were significantly stronger than those of the non-dominant limb in the group of volleyball players. The position of the forearm had a considerable impact on the strength of the internal and external rotator muscles. The maximal voluntary contraction method used in the study can be helpful in measuring the strength of the shoulder rotator muscles in any phase of the training process.

scholarly journals Effects of ipsilateral and contralateral fatigue and muscle occlusion on the complexity of knee extensor torque output in humans

2018 ◽  
Author(s):  
Jamie Pethick ◽  
Samantha Lee Winter ◽  
Mark Burnley
Keyword(s):  
Dominant Role ◽  
Recovery Period ◽  
Knee Extensor ◽  
Approximate Entropy ◽  
Voluntary Contraction ◽  
Peripheral Fatigue ◽  
Knee Extensors ◽  
Fluctuation Analysis ◽  
The Right ◽  
Cuff Occlusion

To determine whether the fatigue-induced loss of torque complexity could be accounted for by central or peripheral factors, nine healthy participants performed four experimental trials involving intermittent isometric contractions of the knee extensors at 50% of the maximal voluntary contraction (MVC) torque. These trials involved: 1) two bouts of contractions to failure using the right leg separated by 3 min recovery (ISP); 2) the same protocol but with cuff occlusion during the 3-min recovery (ISP-OCC); 3) contractions of the left leg to failure, followed 1 min later by contractions of the right leg to failure (CONT); and 4) the same protocol but with cuff occlusion applied to the left leg throughout both the recovery period and right leg contractions (CONT-OCC). Supramaximal electrical stimulation during MVCs was used to determine the degree of central and peripheral fatigue, whilst complexity was determined using Approximate Entropy (ApEn) and Detrended Fluctuation Analysis alpha-exponent (DFA alpha). Neuromuscular fatigue was consistently associated with a loss of torque complexity in all conditions (e.g., ISP bout 1 ApEn from [mean +/- SD]: 0.46 +/- 0.14 to 0.12 +/- 0.06 [P &lt; 0.001]). In ISP-OCC, occlusion abolished the recovery from fatigue and torque complexity remained at the values observed at task failure in the preceding bout (IPS-OCC bout 2, first minute: 0.14 +/- 0.03, P &lt; 0.001). Prior contralateral contractions had no effect on torque complexity. These results demonstrate that peripheral fatigue plays a dominant role in the loss of torque complexity.

scholarly journals Sex difference in fatigability of knee extensor muscles during sustained low-level contractions

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Ryota Akagi ◽  
Shinya Sato ◽  
Kana Yoshihara ◽  
Hideki Ishimatsu ◽  
Ryoichi Ema
Keyword(s):  
Muscle Strength ◽  
Shear Modulus ◽  
Sex Difference ◽  
Peak Torque ◽  
Voluntary Activation ◽  
Peripheral Fatigue ◽  
Knee Extensors ◽  
Maximal Voluntary Isometric Contraction ◽  
Before And After ◽  
Maximal Muscle Strength

Abstract This study investigated whether the sex difference in fatigability of the knee extensors (KE) is explained by the sex difference in fatigue-induced changes in the shear modulus of one or more muscles of KE in 18 young men and 23 young women. The shear moduli of the resting rectus femoris and medial and lateral vastus muscles (VL) were measured before and after a sustained contraction at 20% peak torque during a maximal voluntary isometric contraction of KE until the endurance limit, in addition to evoked torque and voluntary activation (VA%). The fatigue-induced decrease in maximal muscle strength was more prominent in men than in women. Only the VL shear modulus for men increased after the fatiguing task, and a sex difference was observed in the percentage change in the VL shear modulus before and after the fatiguing task. The fatigue-induced decreased ratio was greater for men than for women in evoked torque, but not in VA%. These results suggest that although peripheral and central fatigue both influenced the fatigue-induced decrease in maximal muscle strength regardless of sex, the sex difference in KE fatigability is explained by that in peripheral fatigue, particularly the degree of peripheral VL fatigue.

Comparative Arterial Antithrombotic Activity of Clopidogrel and Acetyl Salicylic Acid in the Pig

1992 ◽  
Vol 68 (05) ◽  
pp. 500-505 ◽  
Author(s):  
Ch M Samama ◽  
Ph Bonnin ◽  
M Bonneau ◽  
G Pignaud ◽  
E Mazoyer ◽  
...  
Keyword(s):  
Platelet Aggregation ◽  
Femoral Artery ◽  
Bleeding Time ◽  
Ex Vivo ◽  
Flow Reduction ◽  
Cyclic Flow ◽  
Left Femoral Artery ◽  
Before And After ◽  
The Right ◽  
Induced Aggregation

SummaryWe investigated the comparative antithrombotic properties of clopidogrel, an analogue of ticlopidine, and aspirin, using the Folts' model on femoral arteries in 22 pigs. On each animal, clopidogrel or aspirin were used to treat the thrombotic process on the left femoral artery and to prevent this process on the right femoral artery. Sequentially: an injury and stenosis were carried out on the left femoral artery; the thrombotic process was monitored with a Doppler during a 30-min observation period for cyclic flow reductions or permanent cessation of flow; after the first cyclic flow reduction occurred, clopidogrel (5 mg kg-1) or aspirin (2.5, 5, 100 mg kg-1) were injected intravenously; if cyclic flow reductions were abolished, epinephrine (0.4 µg kg-1 min-1) was injected to try to restore cyclic flow reductions and/or permanent cessation of flow; then injury and stenosis were applied on the right femoral artery. Before and after injection of clopidogrel or aspirin, ear immersion bleeding times and ex-vivo platelet aggregation were performed. Clopidogrel (n = 7) abolished cyclic flow reductions in all animals and epinephrine did not restore any cyclic flow reduction. On the right femoral artery, cyclic flow reductions were efficiently prevented, even for two injuries. Basal bleeding time (5 min 28) was lengthened (>15 min, 30 min after clopidogrel and remained prolonged even after 24 h). ADP-induced platelet aggregation was inhibited (more than 78%). Comparatively, aspirin had a moderate and no dose-dependent effect. Aspirin 2.5 mg kg-1 (n = 6) abolished cyclic flow reductions in 2 animals, CFR reoccurred spontaneously in one animal and epinephrine restored it in a second animal. Aspirin 5 mg kg-1 (n = 6) abolished cyclic flow reductions in only 3 animals and epinephrine always restored it. Aspirin 100 mg kg-1 (n = 3) was unable to abolish cyclic flow reductions. On the right femoral artery, aspirin did not significantly prevent cyclic flow reductions which occurred in all animals after one (n = 14) or two injuries (n = 1), except for one animal. Basal bleeding time was lengthened but it shortened rapidly, reaching its basal value after 24 h. ADP-induced aggregation was not significantly inhibited, whereas arachidonic acid induced aggregation was always inhibited. Clopidogrel appears as a more potent antithrombotic drug than aspirin in this model, in treating and preventing spontaneous or epinephrine-induced cyclic flow reductions and lengthening bleeding time.

EFEKTIVITAS METODE DEMONSTRASI DALAM MENINGKATKAN HASIL BELAJAR SISWA SEKOLAH MENENGAH KEJURUAN PADA PENGAJARAN SISTEM KOLOID

2013 ◽  
Vol 19 (1) ◽  
pp. 28
Author(s):  
Hamda Situmorang ◽  
Manihar Situmorang
Keyword(s):  
High School ◽  
High School Students ◽  
Abstract Concept ◽  
Vocational High School ◽  
School Students ◽  
Lecture Method ◽  
Colloid System ◽  
Before And After ◽  
The Right ◽  
And Control

Abstract Implementation of demonstration method in the teaching of chemistry is assigned as the right strategy to improve students’ achievement as it is proved that the method can bring an abstract concept to reality in the class. The study is conducted to vocational high school students in SMKN1 Pargetteng getteng Sengkut Pakfak Barat at accademic year 2013. The teaching has been carried out three cycles on the teaching of chemistry topic of colloid system. In the study, the class is divided into two class, experiment class and control class. The demontration method is used to teach students in experimental class while the teaching in control class is conducted with lecture method. Both are evaluated by using multiple choise tests before and after the teaching procedures, and the ability of students to answer the problems are assigned as students’ achievements. The results showed that demonstration method improved students’ achievement in chemistry. The students in experimental class who are taughed with demonstration method (M=19.08±0.74) have higher achievements compare with control class (M=12.91±2.52), and both are significantly different (tcalculation 22.85 > ttable 1.66). The effectivity of demostration method in experimental class (97%) is found higer compare to conventional method in control class (91%).

EDUKASI TERHADAP REMAJA DALAM PENINGKATAN PENGETAHUAN TENTANG PENGGUNAAN GAME DENGAN BIJAK

2020 ◽  
Vol 2 (1) ◽  
pp. 11
Author(s):  
Ikhsan Fuady ◽  
Rangga Saptya MP
Keyword(s):  
Side Effects ◽  
Violent Behavior ◽  
Daily Lives ◽  
Before And After ◽  
Improper Use ◽  
Effective Role ◽  
Education And Outreach ◽  
The Right ◽  
Dedicated Team ◽  
User Ratings

<p align="center"><strong>Abstrak</strong></p><p><em>Pemanfaatan game dikalangan remaja memiliki peran yang efektif sebagai wadah untuk hiburan. Tetapi pemanfaatan game tidak tepat memiliki efek samping game terhadap kehidupan sehari hari remaja, mulai dari kurang bersosialIsasi hingga perilaku kekerasan dikalangan remaja. Penyuluhan terhadap remaja bertujuan untuk memberikan pemahaman kepada remaja tentang variasi game berdasarkan rating pengguna, maupun cerdas dalam manajemen penggunaan game dalam kehidupan remaja sehari hari. Pengetahuan remaja tentang varian/ragam game berdasarkan rating relatif rendah sebagaian besar pemengetahuannya tersebar pada kategori sangat rendah dan rendah yaitu sebesar 65 persen. Metode edukasi dan sosialisasi ini adalah dengan beberapa tahapan. Tahap pertaman tim pengabdian memberikan edukasi dan diskusi tentang beragam bentuk game, karakteristik, serta karakteristik pengguna game yang tepat. Selanjutnya beberapa permainan dan kuis untuk meingkatkan literasi remaja tentang pemanfaatan game secara bijak. Kegiatan penyuluhan ini mampu meningkatkan pemahaman para remaja dalam mengenali game yang baik digunakan, hal ini dapat dilihat dari peningkatan pengetahuan remaja relatif signifikan sebelum dan sesudah penyuluhan.</em></p><p><strong>Kata kunci<em>:</em></strong><strong><em> </em></strong><strong><em>Edukasi, Game, Penyuluhan </em></strong></p><p align="center"><em> </em></p><p align="center"><strong>Abstract</strong> </p><p><em>The use of games among teenagers has an effective role as a forum for entertainment. But the improper use of games has the side effects of games on the daily lives of adolescents, ranging from lack of socialization to violent behavior in adolescents. Counseling against adolescents aims to provide understanding to adolescents about the variety/variance of games based on user ratings, as well as being smart in managing game use in daily teenage life. Teenagers' knowledge about game variants/based on the rating is relatively low, most of the knowledge is spread in the very low and low categories, which is 65 percent. The method of education and outreach is by several stages. The first stage of the dedicated team provided education and discussion about various forms of games, characteristics, and characteristics of the right game user. Furthermore, some games and quizzes to improve teen literacy about game use wisely. This counseling activity can increase the understanding of teenagers in recognizing games that are well used, this can be seen from the relatively significant increase in adolescent knowledge before and after counseling.</em></p><p><strong>Keywords<em>:</em></strong><em> <strong>Education, Games, Counseling</strong></em></p>

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