Quadriceps Muscle Postactivation Potentiation and Twitch Contraction Time in Elderly Men with and Without COPD

The ferret has become a popular model for physiological and neurodevelopmental research in the visual system. We believed it important, therefore, to study extraocular whole muscle as well as single motor unit physiology in the ferret. Using extracellular stimulation, 62 individual motor units in the ferret abducens nucleus were evaluated for their contractile characteristics. Of these motor units, 56 innervated the lateral rectus (LR) muscle alone, while 6 were split between the LR and retractor bulbi (RB) muscle slips. In addition to individual motor units, the whole LR muscle was evaluated for twitch, tetanic peak force, and fatigue. The abducens nucleus motor units showed a twitch contraction time of 15.4 ms, a mean twitch tension of 30.2 mg, and an average fusion frequency of 154 Hz. Single-unit fatigue index averaged 0.634. Whole muscle twitch contraction time was 16.7 ms with a mean twitch tension of 3.32 g. The average fatigue index of whole muscle was 0.408. The abducens nucleus was examined with horseradish peroxidase conjugated with the subunit B of cholera toxin histochemistry and found to contain an average of 183 motoneurons. Samples of LR were found to contain an average of 4,687 fibers, indicating an LR innervation ratio of 25.6:1. Compared with cat and squirrel monkeys, the ferret LR motor units contract more slowly yet more powerfully. The functional visual requirements of the ferret may explain these fundamental differences.

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Velocity of shortening of single motor units from rat soleus

Journal of Neurophysiology ◽

10.1152/jn.1992.67.5.1133 ◽

1992 ◽

Vol 67 (5) ◽

pp. 1133-1145 ◽

Cited By ~ 5

Author(s):

S. R. Devasahayam ◽

T. G. Sandercock

Keyword(s):

Motor Unit ◽

Motor Units ◽

Surrounding Tissue ◽

Passive Tension ◽

Contraction Time ◽

Single Motor ◽

Twitch Contraction ◽

Single Motor Units ◽

Velocity Of Shortening ◽

Force Velocity

1. The force-velocity relationship of a motor unit can provide insight into the contractile proteins of its constituent fibers as well as fundamental information about the function and use of the motor unit. Although the force-velocity profiles of whole muscle and skinned mammalian fibers have been studied, technical difficulties have prevented similar studies on motor units. A technique is presented to directly measure the velocity of shortening of individual motor units from in vivo rat soleus muscle. 2. The soleus muscles of anesthetized rats were dissected free of surrounding tissue while their nerve and blood supplies were preserved. Both tendons were cut, and the distal tendon was attached to a servomechanism to control muscle length, whereas the proximal tendon was attached to a force transducer. Single motor units were stimulated via the ventral roots. 3. The major problem encountered in measuring the force-velocity profile of a motor unit was that the force from the large number of passive fibers and connective tissue in the soleus confounded the force produced by the small number of active fibers in the motor unit. This problem was minimized by measuring active motor unit tension during an isovelocity ramp. This allowed experimental measurement of the passive tension by shortening the muscle with an identical isovelocity ramp without, however, stimulating the motor unit. Active tension was estimated by subtracting the passive tension waveform from the waveform recorded when the motor unit was active. 4. The method substantially reduced the noise from the passive fibers; however, problems remained. The probable sources of error are discussed, with the most significant being the elasticity associated with the blood and nerve connections to surrounding tissue. The elasticity prevents uniform shortening velocities along the length of the active fibers, thereby introducing a systematic bias to measurements made at high velocities. These errors are most pronounced when the data are extrapolated to determine the maximum velocity of shortening (Vmax). Determination of velocity at peak power (Vpp) is a more robust measure; however, of the 34 motor units studied, only 19 exhibited a distinct peak in the power-force curve, indicating residual noise. 5. To assess the validity of using twitch contraction time as an index of the velocity of shortening, when possible, Vmax and Vpp of each motor unit were correlated with the inverse of its twitch contraction time. The correlation was poor (r less than 0.2), indicating that, although widely used, twitch contraction time is a poor index of contractile speed.

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Contractile adaptations in the human triceps surae after isometric exercise

Journal of Applied Physiology ◽

10.1152/jappl.1989.66.6.2725 ◽

1989 ◽

Vol 66 (6) ◽

pp. 2725-2732 ◽

Cited By ~ 32

Author(s):

S. E. Alway ◽

J. D. MacDougall ◽

D. G. Sale

Keyword(s):

Volume Density ◽

Voluntary Contraction ◽

Triceps Surae ◽

Type I ◽

Type Ii ◽

Contraction Time ◽

Twitch Contraction ◽

Human Triceps Surae ◽

Before And After ◽

Type Ii Fibers

Ultrastructural and twitch contractile characteristics of the human triceps surae were determined in seven healthy but very sedentary subjects before and after 16 wk of unilateral isometric training at 100% maximal voluntary contraction. After training, twitch contraction time decreased by approximately 20%. One-half relaxation time, peak twitch torque, and percent fiber type in any of the muscles of the triceps surae complex were not changed by training. Type I and type II fiber areas increased in the soleus by approximately 30%, but only type II fibers showed an increased in area in the lateral gastrocnemius (40%). Despite such changes in fiber area, the volume density of the sarcoplasmic reticulum-transverse tubular (SR) network averaged 3.2 +/- 0.6 and 5.9 +/- 0.9% in type I and type II fibers, respectively, before and after training in the two heads of the gastrocnemius. Type I SR fraction increased to 3.5 +/- 1.2% after training in the soleus; however, correlations were not significant between the change in the volume density of SR and the change in twitch contraction time (R = 0.46, P = 0.45) or the change in one-half relaxation time (R = -0.68, P = 0.08). The results demonstrate that isometric training at 100% maximal voluntary contraction induced changes in twitch contraction time that were not directly related to changes in the volume density of SR in fibers of the triceps surae.

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Nonlinear summation of contractions in cat muscles. II. Later facilitation and stiffness changes.

The Journal of General Physiology ◽

10.1085/jgp.78.3.295 ◽

1981 ◽

Vol 78 (3) ◽

pp. 295-311 ◽

Cited By ~ 153

Author(s):

F Parmiggiani ◽

R B Stein

Keyword(s):

Soleus Muscle ◽

Time Course ◽

Short Interval ◽

Force Production ◽

Muscle Stiffness ◽

Contraction Time ◽

Plantaris Muscle ◽

Twitch Contraction ◽

Slow Twitch ◽

Fast Twitch

The force produced by cat muscles over time with two stimuli separated by a short interval is approximately three times that produced by a twitch of cat muscles. This facilitation of force production by a second stimulus involves both increases in magnitude and duration of the contraction. Increased magnitude is relatively more important in the fast-twitch plantaris muscle, whereas increased duration is more important in the slow-twitch soleus muscle. The facilitation decays in an approximately exponential manner with the interval between stimuli, having a time constant between one and two times the twitch contraction time in different muscles. If a third stimulus is added, the greatest facilitation is seen at intervals longer than the twitch contraction time. The drug Dantrolene, which specifically reduces Ca++ release from the sarcoplasmic reticulum, eliminates the delayed peak in facilitation with three stimuli. Associated with the increases in force with one or more stimuli are increases in muscle stiffness, which can be measured with small, brief stretches and releases that do not alter the time-course of contraction. The stiffness of soleus muscle reaches a peak after the peak in force. The increasing stiffness of the muscle can considerably facilitate transmission of force generated internally, in addition to any facilitation arising from Ca++-release mechanisms.

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

Baltic Journal of Sport and Health Sciences ◽

10.33607/bjshs.v4i67.533 ◽

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.

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

Baltic Journal of Sport and Health Sciences ◽

10.33607/bjshs.v4i63.573 ◽

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.

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Postactivation potentiation, fiber type, and twitch contraction time in human knee extensor muscles

Journal of Applied Physiology ◽

10.1152/jappl.2000.88.6.2131 ◽

2000 ◽

Vol 88 (6) ◽

pp. 2131-2137 ◽

Cited By ~ 205

Author(s):

Taku Hamada ◽

Digby G. Sale ◽

J. Duncan MacDougall ◽

Mark A. Tarnopolsky

Keyword(s):

Small Mammals ◽

Fiber Type ◽

Knee Extensors ◽

Type I ◽

Type Ii ◽

Postactivation Potentiation ◽

Maximum Voluntary Isometric Contraction ◽

Twitch Contraction ◽

Contraction Times ◽

Type Ii Fibers

In small mammals, muscles with shorter twitch contraction times and a predominance of fast-twitch, type II fibers exhibit greater posttetanic twitch force potentiation than muscles with longer twitch contraction times and a predominance of slow-twitch, type I fibers. In humans, the correlation between potentiation and fiber-type distribution has not been found consistently. In the present study, postactivation potentiation (PAP) was induced in the knee extensors of 20 young men by a 10-s maximum voluntary isometric contraction (MVC). Maximal twitch contractions of the knee extensors were evoked before and after the MVC. A negative correlation ( r = −0.73, P < 0.001) was found between PAP and pre-MVC twitch time to peak torque (TPT). The four men with the highest (HPAP, 104 ± 11%) and lowest (LPAP, 43 ± 7%) PAP values ( P < 0.0001) underwent needle biopsies of vastus lateralis. HPAP had a greater percentage of type II fibers (72 ± 9 vs. 39 ± 7%, P < 0.001) and shorter pre-MVC twitch TPT (61 ± 12 vs. 86 ± 7 ms, P < 0.05) than LPAP. These data indicate that, similar to the muscles of small mammals, human muscles with shorter twitch contraction times and a higher percentage of type II fibers exhibit greater PAP.

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Relation between isometric force and stimulus rate in cat's hindlimb motor units of different twitch contraction time

Experimental Brain Research ◽

10.1007/bf00239186 ◽

1983 ◽

Vol 50-50 (2-3) ◽

Cited By ~ 35

Author(s):

D. Kernell ◽

O. Eerbeek ◽

B.A. Verhey

Keyword(s):

Isometric Force ◽

Motor Units ◽

Contraction Time ◽

Stimulus Rate ◽

Twitch Contraction

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Mechanical responses of human hypothenar and calf muscles in normal and pathological states

Arquivos de Neuro-Psiquiatria ◽

10.1590/s0004-282x1977000200004 ◽

1977 ◽

Vol 35 (2) ◽

pp. 119-128

Author(s):

Roberto E. P. Sica

Keyword(s):

Neuromuscular Disorders ◽

Contraction Time ◽

Twitch Contraction ◽

Mechanical Responses ◽

Slow Group ◽

Calf Muscles

A study has been made of the isometric twitches of hypothenar and calf muscles in man. The twitch contraction time for hypothenar muscles ranged between 55 and 78 ms, while for the calf muscles it ranged between 90 and 125 ms. According to their speed of contractions the hypothenar muscles were considered belonging to the so called intermedious group while the calf muscles integrate the slow group. It has been also demonstrated that these techniques can successfully be applied to the investigation of several neuromuscular disorders.

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