scholarly journals Post-Activation Potentiation and Fatigue of Quadriceps Muscle after Continuous Isometric Contractions at Maximal and Submaximal Intensities

2018 ◽  
Vol 4 (67) ◽  
Author(s):  
Nerijus Masiulis ◽  
Albertas Skurvydas ◽  
Sigitas Kamandulis ◽  
Jūratė Kudirkaitė ◽  
Vytautas Sukockas ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Recovery Period ◽  
Maximum Voluntary Contraction ◽  
Isometric Exercise ◽  
Quadriceps Muscle ◽  
Knee Extension ◽  
Voluntary Contraction ◽  
Contractile Properties ◽  
Contraction Time ◽  
Isometric Knee Extension

The dominance of fatigue or post-activation potentiation (PAP) depends on the type, intensity, and duration of exercise and duration of the recovery before contractility is tested. Although the decrease in PAP magnitude with decreased exercise intensity is well documented (Vandervoort et al., 1983; Behm et al., 2004), it is not clear how PAP and fatigue influences the contractile properties of skeletal muscle when exercise is of different intensity but with the same amount of work performed. Thus it is important to understand the manifestation of PAP and fatigue of skeletal muscle after continuous maximal and submaximal contractions but with the same amount of work performed. Eight healthy untrained men (age 23—27 years, mass 83.5 ± 5.4 kg) performed maximal sustained isometric knee extension for 30 s (MVC-30 s) and on the other occasion the same subject performed sustained isometric knee extension for 60 s at 50% of maximal (50% MVC-60 s). We assumed that the amount of performed work was the same during both MVC-30 s and 50% MVC-60 s exercises. The experimental order was randomized. The contractile properties of quadriceps muscle evoked by electrical stimulation at 1 Hz (P 1), 10 Hz (P 10), 20 Hz (P 20), and 50 Hz (P 50) as well as contraction time (CT) and relaxation time (RT) of single twitch (P 1) and EMGrms of v. lateralis muscle were recorded before and immediately after the exercises (0 min) and 1, 2, and 3 min following the exercises. A significantly greater potentiation (p < 0.05) of P1 was observed after 30-s MVC (MVC-30 s) compared with the 60-s MVC (50% MVC-60 s) immediately after exercise and at 1 min of recovery. No changes in P 1 contraction time (CT) were observed during 3 min recovery period, however half relaxation of P 1 (½ RT) was more prolonged (p < 0.05) immediately after 50% MVC-60 s exercises. Moreover, immediately and 1 min post exercise the P 10 force after MVC-30 s exercise was higher (p < 0.05) compared to 50% MVC-60 s exercise. No differences between MVC-30 s and 50% MVC-60 s exercises were observed at high stimulation frequencies, maximal voluntary contraction force (MVC) as well as for EMGrms values during 3 min recovery period. The main finding of the present study was that PAP was observed after both maximal and submaximal intensity exercises when the same amount of work was performed. The more intensively exercise is performed, the more PAP offsets fatigue straight after exercise (maximal intensity); while after submaximal exercise PAP becomes more evident only during the recovery period.Keywords: skeletal muscle, isometric exercise, maximum voluntary contraction, recovery.

Force control of quadriceps muscle is bilaterally impaired in subacute stroke

2011 ◽  
Vol 111 (5) ◽  
pp. 1290-1295 ◽  
Author(s):  
John W. Chow ◽  
Dobrivoje S. Stokic
Keyword(s):  
Force Control ◽  
Maximum Voluntary Contraction ◽  
Quadriceps Muscle ◽  
Knee Extension ◽  
Voluntary Contraction ◽  
Force Variability ◽  
Stroke Patients ◽  
Subacute Stroke ◽  
Peak Knee ◽  
Isometric Knee Extension

We tested the hypothesis that force variability and error during maintenance of submaximal isometric knee extension are greater in subacute stroke patients than in controls and are related to motor impairments. Contralesional (more-affected) and ipsilesional (less-affected) legs of 33 stroke patients with sufficiently high motor abilities (62 ± 13 yr, 16 ± 2 days postinjury) and the dominant leg of 20 controls (62 ± 10 yr) were tested in sitting position. After peak knee extension torque [maximum voluntary contraction (MVC)] was established, subjects maintained 10, 20, 30, and 50% of MVC as steady and accurate as possible for 10 s by matching voluntary force to the target level displayed on a monitor. Coefficient of variation (CV) and root-mean-square error (RMSE) were used to quantify force variability and error, respectively. The MVC was significantly smaller in the more-affected than less-affected leg, and both were significantly lower than in controls. The CV was significantly larger in the more-affected than less-affected leg at 20 and 50% MVC, whereas both were significantly larger compared with controls across all force levels. Both more-affected and less-affected legs of patients showed significantly greater RMSE than controls at 30 and 50% MVC. The CV and RMSE were not related to the Fugl-Meyer motor score or to the Rivermead Mobility Index. The CV negatively correlated with MVC in controls but only in the less-affected leg of patients. It is concluded that isometric knee extension strength and force control are bilaterally impaired soon after stroke but more so in the more-affected leg. Future studies should examine possible mechanisms and the evolution of these changes.

scholarly journals Post-Activation Potentiation and Fatigue in Quadriceps Femoral Muscle after a 5 s Maximal Voluntary Isometric Contraction

2018 ◽  
Vol 1 (68) ◽  
Author(s):  
Nerijus Masiulis ◽  
Albertas Skurvydas ◽  
Sigitas Kamandulis ◽  
Audrius Sniečkus ◽  
Marius Brazaitis ◽  
...  
Keyword(s):  
Electrical Stimulation ◽  
Isometric Exercise ◽  
Low Frequency ◽  
Quadriceps Muscle ◽  
Knee Extension ◽  
Voluntary Contraction ◽  
Simultaneous Occurrence ◽  
Contraction Force ◽  
Maximal Voluntary Isometric Contraction ◽  
Low Frequency Fatigue

Following an acute physical exercise, both post-activation potentiation and fatigue of the neuromuscular apparatus may occur. The voluntary recruitment of motor units occurs with frequencies that elicit incompletely fused tetanic contractions and these frequencies are most susceptible for post-activation potentiation as well as low-frequency fatigue. Therefore, the goal of the present study was to investigate which of the processes post-activation potentiation or low-frequency fatigue will be prevalent after 5 s maximal voluntary contraction (MVC). Eight healthy untrained men (age 24—35 years, mass 81.2 ± 5.1 kg) performed maximal sustained isometric knee extension for 5 s at a knee angle of 90 degrees. The contractile properties of quadriceps muscle evoked by electrical stimulation at 1, 7, 10, 15, 20, 50 Hz and 100 Hz, were recorded before and immediately after the exercise and 3, 5, and 10 min following the exercise. The rest interval between muscle electrical stimulation was 3 s. A significant raise of force evoked by 1—15 Hz stimulation was observed immediately after the 5 s MVC exercise (p < 0.01). Later in recovery (at 10 min) the contraction force at 15 Hz and 20 Hz significantly decreased (p < 0.05). Tetanic force at 50 Hz and 100 Hz demonstrated a significant decrease immediately after the exercise and remained depressed up to 3 min (p < 0.01). The ratio of 20 / 50 Hz recorded immediately after the 5 s MVC increased significantly (p < 0.05), however 10 min after the exercise there was a significant decrease compared to its initial level (p < 0.05). The simultaneous occurrence of post-activation potentiation at low stimulation frequencies and suppressed forces at high stimulation frequencies suggests that potentiation and fatigue mechanisms were acting concurrently. Moreover, when post-activation potentiation is lost (in 10 min after the 5 s MVC exercise), the contraction force at low stimulation frequencies decreases resulting in significant low-frequency fatigue.Keywords: isometric exercise, electrical stimulation, low-frequency fatigue, recovery.

scholarly journals Postactivation Potentiation Counteracts Low- Frequency Fatigue of Quadriceps Muscle during Explosive Strength Training Session

2018 ◽  
Vol 4 (63) ◽  
Author(s):  
Nerijus Masiulis ◽  
Albertas Skurvydas ◽  
Sigitas Kamandulis ◽  
Lina Kamandulienė
Keyword(s):  
Strength Training ◽  
Recovery Period ◽  
Maximum Voluntary Contraction ◽  
Training Session ◽  
Low Frequency ◽  
Quadriceps Muscle ◽  
Voluntary Contraction ◽  
Postactivation Potentiation ◽  
Explosive Strength ◽  
Low Frequency Fatigue

Repeated activation of muscle induces processes resulting in decreased performance (fatigue) as well as enhanced performance (postactivation potentiation, (PAP)). This implies that at any time during contraction, fatiguing effects are being countered by potentiation effects, and vise versa. Therefore, which of the processes will be prevalent during and after explosive strength training is not clear.The purpose of this investigation was to study the acute neuromuscular responses to one explosive strength training session. Eleven healthy untrained men (aged 22—35 years) performed explosive strength training session of six sets (fi ve repetitions each) of the unilateral isometric contractions at an angle of 90 degrees in the knee. The contractility of the muscle was monitored via the electrically evoked contractions at 1, 20, and 50 Hz (P 1, P 20, and P 50, re-spectively) before (Ini), after the fi rst and sixth sets as well as during the 5 and 30 min recovery period (A 5 and A 30, respectively). Contraction time (CT) and relaxation time (RT) of a single twitch (P1) of quadriceps was registered. Maximal voluntary contraction (MVC) force as well force developed during 100 ms (MVC 0-100ms ) was also determined. The ratio of P 20 / P 50 kinetics after exercise was used for the evaluation of low-frequency fatigue (LFF). There was statistically signifi cant repetition effect observed on MVC (p = 0.045) and MVC 0-100ms  (p = 0.012). After the fi rst set there was a signifi cant increase in muscle force induced by very low (1 Hz) and low (20 Hz) stimulation frequencies and did not change during all explosive strength training session (p < 0.05). The ratio of P 20 / P 50 recorded after the fi rst set increased signifi cantly (p < 0.05), however 30-min after the explosive strength training session it was signifi cantly decrease in P 20 / P50 ratio compared to its Ini level (p < 0.05). The present study showed that potentia-tion increases P 20 / P 50 ratio during the explosive strength training session, however the subsequent (after 30 min of recovery) decline in P 20 / P 50 ratio is an outcome of diminishing infl uence of potentiation on the background of persistent LFF. Therefore, when muscles are potentiated, it may seem as if no LFF is present.Keywords: explosive strength training, low-frequency fatigue, maximum voluntary contraction, post-activation potentiation.

scholarly journals Characterizing rapid-onset vasodilation to single muscle contractions in the human leg

2015 ◽  
Vol 118 (4) ◽  
pp. 455-464 ◽  
Author(s):  
Daniel P. Credeur ◽  
Seth W. Holwerda ◽  
Robert M. Restaino ◽  
Phillip M. King ◽  
Kiera L. Crutcher ◽  
...  
Keyword(s):  
Maximum Voluntary Contraction ◽  
Knee Extensor ◽  
Rapid Onset ◽  
Knee Extension ◽  
Voluntary Contraction ◽  
Muscle Contractions ◽  
Isometric Contractions ◽  
Single Muscle ◽  
Isometric Knee Extension ◽  
Mechanical Factors

Rapid-onset vasodilation (ROV) following single muscle contractions has been examined in the forearm of humans, but has not yet been characterized in the leg. Given known vascular differences between the arm and leg, we sought to characterize ROV following single muscle contractions in the leg. Sixteen healthy men performed random ordered single contractions at 5, 10, 20, 40, and 60% of their maximum voluntary contraction (MVC) using isometric knee extension made with the leg above and below heart level, and these were compared with single isometric contractions of the forearm (handgrip). Single thigh cuff compressions (300 mmHg) were utilized to estimate the mechanical contribution to leg ROV. Continuous blood flow was determined by duplex-Doppler ultrasound and blood pressure via finger photoplethysmography (Finometer). Single isometric knee extensor contractions produced intensity-dependent increases in peak leg vascular conductance that were significantly greater than the forearm in both the above- and below-heart level positions (e.g., above heart level: leg 20% MVC, +138 ± 28% vs. arm 20% MVC, +89 ± 17%; P < 0.05). Thigh cuff compressions also produced a significant hyperemic response, but these were brief and smaller in magnitude compared with single isometric contractions in the leg. Collectively, these data demonstrate the presence of a rapid and robust vasodilation to single muscle contractions in the leg that is largely independent of mechanical factors, thus establishing the leg as a viable model to study ROV in humans.

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.

Metabolic heat production during fatigue from voluntary repetitive isometric contractions in humans

1996 ◽  
Vol 81 (3) ◽  
pp. 1323-1330 ◽  
Author(s):  
E. Saugen ◽  
N. K. Vollestad
Keyword(s):  
Energy Cost ◽  
Isometric Force ◽  
Recovery Period ◽  
Isometric Exercise ◽  
Muscle Mechanics ◽  
Force Production ◽  
Cellular Level ◽  
Voluntary Contraction ◽  
O2 Uptake ◽  
Postexercise Recovery

The effect of repetitive isometric knee extensions on the energy cost of contraction was examined. The rate of temperature rise (dT/dt) was determined in test contractions at 30 and 50% of maximal voluntary contraction (MVC) force before and during 30% MVC repetitive isometric exercise (RIE) to exhaustion and regularly in a 30-min postexercise recovery period (n = 9). Pulmonary O2 uptake and muscle temperature (Tmus) were determined at regular intervals. During the 30% MVC test contractions, dT/dt was 5.6 +/- 0.6 mK/s in unfatigued muscle, increasing linearly by 68% during exercise. In the 50% MVC test contractions, dT/dt rose by 84% from 9.8 +/- 1.1 mK/s. dT/dt determined during test contractions at both force levels did not decrease significantly throughout the 30-min postexercise recovery period. The rise in dT/dt was paralleled by 76% increased in O2 uptake. In contrast, Tmus rose initially and then leveled off. The present data indicate that RIE induced a gradual rise in the rate of energy turnover associated with isometric force production. Neither increased Tmus nor recruitment of less economic type II fibers can fully explain the increased energy cost. We suggest that energetic changes may occur at the cellular level and argue that this may be associated with the changes in muscle mechanics occurring during fatigue from submaximal voluntary RIE.

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.

Changes of muscular sound during sustained isometric contraction up to exhaustion

1989 ◽  
Vol 66 (4) ◽  
pp. 1593-1598 ◽  
Author(s):  
C. Orizio ◽  
R. Perini ◽  
A. Veicsteinas
Keyword(s):  
Isometric Contraction ◽  
Exercise Intensity ◽  
Maximum Voluntary Contraction ◽  
Isometric Exercise ◽  
Surface Emg ◽  
Voluntary Contraction ◽  
Biceps Muscle ◽  
Output Force ◽  
Contact Transducer ◽  
Four Levels

The sound (SMG) generated by the biceps muscle during isometric exercise at 20, 40, 60, and 80% of maximum voluntary contraction (MVC) up to exhaustion has been recorded by a contact transducer and integrated (iSMG), together with the surface electromyogram (EMG) in eight young untrained men. At the onset of exercise, iSMG and integrated surface EMG (iEMG) amplitude increased linearly with exercise. iSMG remained constant for 253 +/- 73 (SD), 45 +/- 16, 21 +/- 5, and 0 s at the four levels of contraction. Then iSMG increased linearly at 20% MVC, fluctuated at 40% MVC, and decreased exponentially at 60 and 80% MVC. iSMG exhaustion-to-onset ratio was 5.0 at 20%, 1.0 at 40%, and 0.2 at 60 and 80% MVC. On the contrary, independently of exercise intensity, iEMG increased with time, being 1.4 higher at exhaustion than at the onset. The nonunivocal iSMG changes with time and effort of exercise suggest that the sound may be a useful tool to acquire different information to EMG and output force during muscle contraction up to fatigue.

Alternate muscle activity observed between knee extensor synergists during low-level sustained contractions

2002 ◽  
Vol 93 (2) ◽  
pp. 675-684 ◽  
Author(s):  
Motoki Kouzaki ◽  
Minoru Shinohara ◽  
Kei Masani ◽  
Hiroaki Kanehisa ◽  
Tetsuo Fukunaga
Keyword(s):  
Muscle Activity ◽  
Vastus Lateralis ◽  
Force Production ◽  
Knee Extensor ◽  
Rectus Femoris ◽  
Quadriceps Muscle ◽  
Knee Extension ◽  
Voluntary Contraction ◽  
Low Level ◽  
Integrated Emg

To determine quantitatively the features of alternate muscle activity between knee extensor synergists during low-level prolonged contraction, a surface electromyogram (EMG) was recorded from the rectus femoris (RF), vastus lateralis (VL), and vastus medialis (VM) in 11 subjects during isometric knee extension exercise at 2.5% of maximal voluntary contraction (MVC) for 60 min ( experiment 1). Furthermore, to examine the relation between alternate muscle activity and contraction levels, six of the subjects also performed sustained knee extension at 5.0, 7.5, and 10.0% of MVC ( experiment 2). Alternate muscle activity among the three muscles was assessed by quantitative analysis on the basis of the rate of integrated EMG sequences. In experiment 1, the number of alternations was significantly higher between RF and either VL or VM than between VL and VM. Moreover, the frequency of alternate muscle activity increased with time. In experiment 2, alternating muscle activity was found during contractions at 2.5 and 5.0% of MVC, although not at 7.5 and 10.0% of MVC, and the number of alternations was higher at 2.5 than at 5.0% of MVC. Thus the findings of the present study demonstrated that alternate muscle activity in the quadriceps muscle 1) appears only between biarticular RF muscle and monoarticular vasti muscles (VL and VM), and its frequency of alternations progressively increases with time, and 2) emerges under sustained contraction with force production levels ≤5.0% of MVC.

The Effects of Hypertension and Aging on Left Ventricular Function during Isometric Exercise

1996 ◽  
Vol 4 (1) ◽  
pp. 69-79 ◽  
Author(s):  
Michael Sagiv ◽  
Amira Sagiv ◽  
David Ben-Sira ◽  
Jacob Rudoy ◽  
Michael Soudry
Keyword(s):  
Systolic Function ◽  
Maximum Voluntary Contraction ◽  
Isometric Exercise ◽  
Left Ventricular Systolic Function ◽  
Left Ventricular ◽  
Voluntary Contraction ◽  
Chronic Hypertension ◽  
Ventricular Systolic Function ◽  
Hypertensive Patients ◽  
Effects Of Aging

Hemodynamic and left ventricular systolic function were studied by Doppler echocardiography in 14 young and 15 older adult hypertensive patients and in 15 young and 12 older normotensive individuals. Measures were made at rest and during upright deadlift isometric exercise, at 30% of maximum voluntary contraction for 3 min. At rest, young and older hypertensive patients demonstrated impaired left ventricular systolic function compared to both old and young normotensive subjects. The impaired systolic function was associated with less augmentation in systolic indices during exercise compared with resting values in young and elderly hypertensive patients, and to a lesser degree in the normotensive elderly when compared with young normotensives. These data indicate that at rest, left ventricular systolic function may be compromised in hypertensive patients with left ventricular hypertrophy and, to a lesser extent, in the normotensive elderly. However, other factors in chronic hypertension may contribute to abnormal systolic function and override the effects of aging alone.

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