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Journal articles on the topic 'Contraction's velocitie'

Author: Grafiati

Published: 11 March 2023

Last updated: 31 July 2025

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1

Siegle, M. L., S. Buhner, M. Schemann, H. R. Schmid, and H. J. Ehrlein. "Propagation velocities and frequencies of contractions along canine small intestine." American Journal of Physiology-Gastrointestinal and Liver Physiology 258, no. 5 (1990): G738—G744. http://dx.doi.org/10.1152/ajpgi.1990.258.5.g738.

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This study was performed to clarify in detail the behavior of the propagation velocities and frequencies of contractions along the canine small intestine. In conscious dogs, duodenal, jejunal, and ileal contractions were recorded by multiple, closely spaced strain gauges and analyzed by a computerized method. During both the interdigestive and postprandial states, the propagation velocity increased from the duodenal bulb to the distal duodenum and declined aborally within the jejunum, reaching rather constant values in the ileum. The decrease was steepest in the proximal part of the jejunum. I

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2

Yapıcı, Ayşegül. "Factors effecting hamstrings to quadriceps peak torque ratio in volleyball players." Journal of Human Sciences 13, no. 3 (2016): 5282. http://dx.doi.org/10.14687/jhs.v13i3.4149.

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The aim of this study was to analyze of hamstring to quadriceps peak torque ratio (H:Q) measured in isokinetic testing with respect to different angular velocities (60, 180, 300°/s), gender, dominant side and mode of contraction (concentric, eccentric) in volleyball players. Twenty male and ten female healthy volleyball players participated in this study. An independent t-test was used to compare the differences between gender. One-way analysis of variance test was conducted to test for differences by effecting factors. There was a statistically significant difference between dominant and non-

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3

Reeves, Neil D., and Marco V. Narici. "Behavior of human muscle fascicles during shortening and lengthening contractions in vivo." Journal of Applied Physiology 95, no. 3 (2003): 1090–96. http://dx.doi.org/10.1152/japplphysiol.01046.2002.

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The aim of the present study was to investigate the behavior of human muscle fascicles during dynamic contractions. Eight subjects performed maximal isometric dorsiflexion contractions at six ankle joint angles and maximal isokinetic concentric and eccentric contractions at five angular velocities. Tibialis anterior muscle architecture was measured in vivo by use of B-mode ultrasonography. During maximal isometric contraction, fascicle length was shorter and pennation angle larger compared with values at rest ( P < 0.01). During isokinetic concentric contractions from 0 to 4.36 rad/s, fasci

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4

Ducros, Laurent, Philippe Bonnin, Bernard P. Cholley, et al. "Increasing Maternal Blood Pressure with Ephedrine Increases Uterine Artery Blood Flow Velocity during Uterine Contraction." Anesthesiology 96, no. 3 (2002): 612–16. http://dx.doi.org/10.1097/00000542-200203000-00017.

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Background During labor, ephedrine is widely used to prevent or to treat maternal arterial hypotension and restore uterine perfusion pressure to avoid intrapartum fetal asphyxia. However, the effects of ephedrine on uterine blood flow have not been studied during uterine contractions. The purpose of the study was to assess the effects of ephedrine on uterine artery velocities and resistance index using the Doppler technique during the active phase of labor. Methods Ten normotensive, healthy parturients with uncomplicated pregnancies at term received intravenous ephedrine during labor to increa

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5

Chaouachi, Anis, Monoem Haddad, Carlo Castagna, et al. "Potentiation and Recovery Following Low- and High-Speed Isokinetic Contractions in Boys." Pediatric Exercise Science 23, no. 1 (2011): 136–50. http://dx.doi.org/10.1123/pes.23.1.136.

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The objective of this study was to examine the response and recovery to a single set of maximal, low and high angular velocity isokinetic leg extension-flexion contractions with boys. Sixteen boys (11–14 yrs) performed 10 isokinetic contractions at 60°.s−1 (Isok60) and 300°.s−1 (Isok300). Three contractions at both velocities, blood lactate and ratings of perceived exertion were monitored pretest and at 2, 3, 4, and 5 min of recovery (RI). Participants were tested in a random counterbalanced order for each velocity and recovery period. Only a single contraction velocity (300°.s−1 or 60°.s−1) w

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6

Livingston, E. H., T. J. Howard, T. R. Garrick, E. P. Passaro, and P. H. Guth. "Strong gastric contractions cause mucosal ischemia." American Journal of Physiology-Gastrointestinal and Liver Physiology 260, no. 3 (1991): G524—G530. http://dx.doi.org/10.1152/ajpgi.1991.260.3.g524.

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Contractions of a segment of bowel result in alterations of its blood flow. However, the precise temporal and spacial relationships between contractions and mucosal blood flow are unknown. Rats were fitted with strain gauge force transducers and implanted with silver wire electrodes into the muscularis externa of the stomach. In vivo microscopic observation of motility and of the gastric mucosal blood flow was performed during electrical field-stimulated contractions. Contractions originated in the midcorpus, were 0.237 +/- 0.018 cm wide, traveled along the corpus at 0.133 +/- 0.024 cm/s, and

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7

Christou, Evangelos A., Minoru Shinohara, and Roger M. Enoka. "Fluctuations in acceleration during voluntary contractions lead to greater impairment of movement accuracy in old adults." Journal of Applied Physiology 95, no. 1 (2003): 373–84. http://dx.doi.org/10.1152/japplphysiol.00060.2003.

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The purpose of the study was to assess the effect of movement velocity on the relation between fluctuations in acceleration and the ability to achieve a target velocity during voluntary contractions performed by young (29.5 ± 4.3 yr) and old (74.9 ± 6.2 yr) adults. Subjects performed concentric and eccentric contractions with the first dorsal interosseus muscle while lifting a submaximal load (15% of maximum) at six movement velocities (0.03–1.16 rad/s). Fluctuations in acceleration, the accuracy of matching the target velocity, and electromyographic (EMG) activity were determined from three t

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8

Siegle, M. L., and H. J. Ehrlein. "Interdigestive contractile patterns of the ileum in dogs." American Journal of Physiology-Gastrointestinal and Liver Physiology 253, no. 4 (1987): G452—G460. http://dx.doi.org/10.1152/ajpgi.1987.253.4.g452.

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The aim of this study is to elucidate the nature of ileal interdigestive contractile patterns by the computerized analysis of the contraction spread and by videofluoroscopy. Conscious dogs equipped with closely spaced strain-gauge force transducers were used. Two patterns of repetitive, phasic contractions were recorded, migrating clusters and phase IIIs; both patterns consisted of repetitive, propagated contractions. Both patterns migrated aborad by sequential movement of contraction waves down the bowel. Consequently, the rate of migration of either of the entire patterns was slower than the

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9

Forrester, Stephanie E., and Matthew T. G. Pain. "A Combined Muscle Model and Wavelet Approach to Interpreting the Surface EMG Signals from Maximal Dynamic Knee Extensions." Journal of Applied Biomechanics 26, no. 1 (2010): 62–72. http://dx.doi.org/10.1123/jab.26.1.62.

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This study aimed to identify areas of reduced surface EMG amplitude and changed frequency across the phase space of a maximal dynamic knee extension task. The hypotheses were that (1) amplitude would be lower for eccentric contractions compared with concentric contractions and unaffected by fiber length and (2) mean frequency would also be lower for eccentric contractions and unaffected by fiber length. Joint torque and EMG signals from the vasti and rectus femoris were recorded for eight athletic subjects performing maximum knee extensions at 13 preset crank velocities spanning ±300°⋅s−1. The

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10

Harwood, B., and C. L. Rice. "Short interspike intervals and double discharges of anconeus motor unit action potentials for the production of dynamic elbow extensions." Journal of Neurophysiology 111, no. 10 (2014): 2039–46. http://dx.doi.org/10.1152/jn.00412.2013.

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Incidence of double discharges (DDs; >100 Hz) and short interspike intervals (ISIs; >50 to <100 Hz) is reported to vary widely among different muscles and tasks, with a higher incidence in motor unit (MU) trains of fast muscles and for the production of fast contractions in humans. However, it is unclear whether human muscles with a large composition of slower motor units exhibit DDs or short ISIs when activated with maximal synaptic drive, such as those required for maximal velocity dynamic contractions. Thus the purpose of this study was to determine the effect of increasing peak co

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11

Baudry, Stéphane, and Jacques Duchateau. "Postactivation potentiation in a human muscle: effect on the load-velocity relation of tetanic and voluntary shortening contractions." Journal of Applied Physiology 103, no. 4 (2007): 1318–25. http://dx.doi.org/10.1152/japplphysiol.00403.2007.

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Recently it was demonstrated that postactivation potentiation (PAP), which refers to the enhancement of the muscle twitch torque as a result of a prior conditioning contraction, increased the maximal rate of torque development of tetanic and voluntary isometric contractions ( 3 ). In this study, we investigated the effects of PAP and its decay over time on the load-velocity relation. To that purpose, angular velocity of thumb adduction in response to a single electrical stimulus (twitch), a high-frequency train of 15 pulses at 250 Hz (HFT250), and during ballistic voluntary shortening contract

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12

Behm, D. G., and D. G. Sale. "Intended rather than actual movement velocity determines velocity-specific training response." Journal of Applied Physiology 74, no. 1 (1993): 359–68. http://dx.doi.org/10.1152/jappl.1993.74.1.359.

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Eight men and eight women trained 3 days/wk for 16 wk by doing attempted ballistic unilateral ankle dorsiflexions against resistance that either rendered the resultant contractions isometric (one limb) or allowed a relatively high-velocity (5.23 rad/s on an isokinetic dynamometer) movement (other limb). Training sessions consisted of five sets of 10 contractions of each type. Training produced the same high-velocity-specific training response in both limbs (P < 0.001). Peak torque increased most at 5.23 rad/s (38%) in comparison to lower velocities (0, 0.26, 0.52, 1.04, 1.55, 3.02, and 4.19

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13

Boels, P. J., V. A. Claes, and D. L. Brutsaert. "Mechanics of K(+)-induced isotonic and isometric contractions in isolated canine coronary microarteries." American Journal of Physiology-Cell Physiology 258, no. 3 (1990): C512—C523. http://dx.doi.org/10.1152/ajpcell.1990.258.3.c512.

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The effects of shortening in isotonic contractions on the mechanics of microvascular smooth muscle were investigated. Intramyocardial canine coronary microarteries (in situ diameter 60 +/- 3 microns) were mounted as rings, connected to a newly developed photoelectromagnetic force-length transducer, and activated with 125 mM K+. Shortening during isotonic contractions depressed the length-force relation (shortening deactivation) compared with the length-force relation obtained from isometric contractions; the effect was present at the earliest moments after activation, suggesting that a fundame

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14

Lange, Fiete, Tiemen W. Van Weerden, and Johannes H. Van Der Hoeven. "A new surface electromyography analysis method to determine spread of muscle fiber conduction velocities." Journal of Applied Physiology 93, no. 2 (2002): 759–64. http://dx.doi.org/10.1152/japplphysiol.00594.2001.

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Muscle fiber conduction velocity (MFCV) estimation from surface signals is widely used to study muscle function, e.g., in neuromuscular disease and in fatigue studies. However, most analysis methods do not yield information about the velocity distribution of the various motor unit action potentials. We have developed a new method–the interpeak latency method (IPL)–to calculate both the mean MFCV and the spread of conduction velocities in vivo, from bipolar surface electromyogram (sEMG) during isometric contractions. sEMG was analyzed in the biceps brachii muscle in 15 young male volunteers. Th

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15

Jager, Franc, Ksenija Geršak, Paula Vouk, et al. "Assessing Velocity and Directionality of Uterine Electrical Activity for Preterm Birth Prediction Using EHG Surface Records." Sensors 20, no. 24 (2020): 7328. http://dx.doi.org/10.3390/s20247328.

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The aim of the present study was to assess the capability of conduction velocity amplitudes and directions of propagation of electrohysterogram (EHG) waves to better distinguish between preterm and term EHG surface records. Using short-time cross-correlation between pairs of bipolar EHG signals (upper and lower, left and right), the conduction velocities and their directions were estimated using preterm and term EHG records of the publicly available Term–Preterm EHG DataSet with Tocogram (TPEHGT DS) and for different frequency bands below and above 1.0 Hz, where contractions and the influence

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16

Brooks, S. V., J. A. Faulkner, and D. A. McCubbrey. "Power outputs of slow and fast skeletal muscles of mice." Journal of Applied Physiology 68, no. 3 (1990): 1282–85. http://dx.doi.org/10.1152/jappl.1990.68.3.1282.

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The purpose of this study was to contrast the frequency-power relationship of slow soleus and fast extensor digitorum longus (EDL) muscles to their frequency-force relationships and to investigate factors involved in the development of maximum power during a single contraction. Stimulation frequency-force and stimulation frequency-power relationships were determined for soleus and EDL muscles of the mouse for single contractions in situ at 35 degrees C. Power was measured during isovelocity shortening contractions with displacement through 10% of fiber length at the optimum velocity. Optimum v

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17

Gazzoni, Marco, Federico Camelia, and Dario Farina. "Conduction Velocity of Quiescent Muscle Fibers Decreases During Sustained Contraction." Journal of Neurophysiology 94, no. 1 (2005): 387–94. http://dx.doi.org/10.1152/jn.01182.2004.

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We tested the hypothesis that conduction velocity of quiescent muscle fibers decreases during sustained contraction due to the activity of the active motor units in the muscle. Ten subjects trained for the identification of a target motor unit in the abductor pollicis brevis with feedback on surface EMG signals detected with a two-dimensional array of 61 electrodes. The subjects activated the target motor unit in two 10-s long contractions, before (contraction C1) and after (C3) a 3-min contraction (C2), all in ischemic condition. The target motor unit was not activated during C2. Eight of the

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18

Cheng, Arthur J., and Charles L. Rice. "Isometric torque and shortening velocity following fatigue and recovery of different voluntary tasks in the dorsiflexors." Applied Physiology, Nutrition, and Metabolism 34, no. 5 (2009): 866–74. http://dx.doi.org/10.1139/h09-085.

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The present study was designed to compare the relative influence of various fatigue-related factors involved in isometric and dynamic task failure following an equivalent decrease in isometric maximum voluntary contraction (MVC) torque. Using a similar duty cycle (∼1-s contraction per 2 s) and contraction load (50% of MVC), 9 young males performed in the dorsiflexors a dynamic task, and on a separate occasion an intermittent isometric task, to an equal decrease in isometric MVC torque. Dynamic contractions had greater motor unit activation and maximum rate of torque development, and required f

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19

Farina, Dario, Lars Arendt-Nielsen, and Thomas Graven-Nielsen. "Experimental muscle pain reduces initial motor unit discharge rates during sustained submaximal contractions." Journal of Applied Physiology 98, no. 3 (2005): 999–1005. http://dx.doi.org/10.1152/japplphysiol.01059.2004.

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The aim of this human study was to investigate the effect of experimentally induced muscle pain on the modifications of motor unit discharge rate during sustained, constant-force contractions. Intramuscular and multichannel surface electromyographic (EMG) signals were collected from the right and left tibialis anterior muscle of 11 volunteers. The subjects performed two 4-min-long isometric contractions at 25% of the maximal dorsiflexion torque, separated by a 20-min rest. Before the beginning of the second contraction, hypertonic (painful; right leg) or isotonic (nonpainful; left leg) saline

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20

Harwood, B., and C. L. Rice. "Changes in motor unit recruitment thresholds of the human anconeus muscle during torque development preceding shortening elbow extensions." Journal of Neurophysiology 107, no. 10 (2012): 2876–84. http://dx.doi.org/10.1152/jn.00902.2011.

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Rate of torque development and the subsequent movement velocity are modulated by motor unit (MU) properties, primarily MU discharge rate and MU recruitment threshold (MURT). In isometric conditions, MURTs have been shown to decrease with increased rates of torque development. It is unclear whether this relationship is similar in the production of dynamic shortening contractions. Using fast joint velocities to drive the system, we aimed to determine how anconeus MURTs recorded during the torque production phase preceding movement were affected in relation to the resultant peak elbow extension v

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21

Ryschon, T. W., M. D. Fowler, A. A. Arai, et al. "A multimode dynamometer for in vivo MRS studies of human skeletal muscle." Journal of Applied Physiology 79, no. 6 (1995): 2139–47. http://dx.doi.org/10.1152/jappl.1995.79.6.2139.

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The implementation of muscle ergometry during magnetic resonance spectroscopy and imaging is complicated by the restrictive dimensions of the magnet bore and the presence of a strong static magnetic field. We have developed a dynamometer that is compatible with these constraints. This device can provide resistance to voluntary muscle contraction during isometric, isokinetic concentric, and isokinetic eccentric muscle contractions. While controlling muscle contraction speed, the dynamometer simultaneously records muscle torque production at a 10-Hz sampling frequency to allow assessment of comp

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22

Ren, J., and K. Schulze-Delrieu. "Movement of wax particles by contractions in the isolated opossum esophagus." American Journal of Physiology-Gastrointestinal and Liver Physiology 258, no. 1 (1990): G164—G170. http://dx.doi.org/10.1152/ajpgi.1990.258.1.g164.

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We investigated whether the contractions of the isolated smooth muscle opossum esophagus can propel luminal contents. Wax particles were placed into the esophagus in vitro, and esophageal contractions were evoked by stimulating either primarily the intrinsic esophageal nerves (using electrical pulses of 0.5 ms) or the esophageal muscle directly (using pulses of 0.5 s). Direct muscle stimulation and neural stimulation produced circular muscle contractions of similar amplitude, but only neural stimulation was associated with a propagating ring contraction and longitudinal muscle contraction. Mov

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23

De Haan, A., G. J. Van Ingen Schenau, G. J. Ettema, P. A. Huijing, and M. A. Lodder. "Efficiency of rat medial gastrocnemius muscle in contractions with and without an active prestretch." Journal of Experimental Biology 141, no. 1 (1989): 327–41. http://dx.doi.org/10.1242/jeb.141.1.327.

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The efficiency of positive work was measured for rat medial gastrocnemius muscle at 25 degrees C during repeated contractions. Six muscles were stimulated to perform concentric contractions preceded by an active prestretch (PS contractions) and six muscles made to give concentric contractions from an isometric state (PI contractions). Both lengthening and shortening of the muscles (distance: 6 mm) occurred at a constant velocity of 20 mm s-1 (1.5 fibre lengths s-1). Stimulation was started 150 ms prior to the onset of concentric contraction for both types of contraction. For the PS contraction

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24

Grabiner, M. D. "Maximum rate of force development is increased by antagonist conditioning contraction." Journal of Applied Physiology 77, no. 2 (1994): 807–11. http://dx.doi.org/10.1152/jappl.1994.77.2.807.

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Nine subjects performed maximum contractions with the knee extensor muscles on an isokinetic device set at 4.36 rad/s. The knee extensions were preceded by isometric conditioning contractions of the antagonist knee flexor muscles. The conditioning contraction forces were 0, 25, 50, 75, and 100% of the maximum isometric force. The purpose of the study was to determine 1) the effects of graded conditioning contractions with the knee flexor muscles on the maximum performance of the quadriceps femoris and 2) whether the effects of the conditioning contractions are similarly distributed to componen

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25

Miyagawa, Taimei, Yohsuke Imai, Shunichi Ishida, and Takuji Ishikawa. "Relationship between gastric motility and liquid mixing in the stomach." American Journal of Physiology-Gastrointestinal and Liver Physiology 311, no. 6 (2016): G1114—G1121. http://dx.doi.org/10.1152/ajpgi.00346.2016.

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The relationship between gastric motility and the mixing of liquid food in the stomach was investigated with a numerical analysis. Three parameters of gastric motility were considered: the propagation velocity, frequency, and terminal acceleration of peristaltic contractions. We simulated gastric flow with an anatomically realistic geometric model of the stomach, considering free surface flow and moving boundaries. When a peristaltic contraction approaches the pylorus, retropulsive flow is generated in the antrum. Flow separation then occurs behind the contraction. The extent of flow separatio

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26

Hellstrand, P., and I. Nordstrom. "Cross-bridge kinetics during shortening in early and sustained contraction of intestinal smooth muscle." American Journal of Physiology-Cell Physiology 265, no. 3 (1993): C695—C703. http://dx.doi.org/10.1152/ajpcell.1993.265.3.c695.

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Mechanisms responsible for the decrease in shortening velocity after prolonged contraction ("latch" state) were investigated at identical force during early (20 s, "phasic") and sustained (5 min, "tonic") phases of high-K+ (25-30 mM) contractions in smooth muscle of guinea pig taenia coli. Cytoplasmic Ca2+ concentration, myosin light-chain phosphorylation, and maximum shortening velocity all declined from 20 s to 5 min of contraction. The time course of shortening following isotonic quick release was biexponential, with a fastest rate constant of approximately 80 s-1 in both phasic and tonic c

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27

Devrome, Andrea N., and Brian R. MacIntosh. "Force-velocity relationship during isometric and isotonic fatiguing contractions." Journal of Applied Physiology 125, no. 3 (2018): 706–14. http://dx.doi.org/10.1152/japplphysiol.01119.2017.

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Fatiguing contractions change the force-velocity relationship, but assessment of this relationship in fatigue has usually been obtained after isometric contractions. We studied fatigue caused by isometric or isotonic contractions, by assessment of the force-velocity relationship while the contractions maintaining fatigue were continued. This approach allowed determination of the force-velocity relationship during a steady condition of fatigue. We used the in situ rat medial gastrocnemius muscle, a physiologically relevant preparation. Intermittent (1/s) stimulation at 170 Hz for 100 ms resulte

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28

Munkvik, Morten, Per Kristian Lunde, and Ole M. Sejersted. "Causes of fatigue in slow-twitch rat skeletal muscle during dynamic activity." American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 297, no. 3 (2009): R900—R910. http://dx.doi.org/10.1152/ajpregu.91043.2008.

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Skeletal muscle fatigue is most often studied in vitro at room temperature and is classically defined as a decline in maximum force production or power output, exclusively linked to repeated isometric contractions. However, most muscles shorten during normal use, and we propose that both the functional correlate of fatigue, as well as the fatigue mechanism, will be different during dynamic contractions compared with static contractions. Under isoflurane anesthesia, fatigue was induced in rat soleus muscles in situ by isotonic shortening contractions at 37°C. Muscles were stimulated repeatedly

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29

Khezzar, L., and J. H. Whitelaw. "Flows Through Round Sudden Contractions." Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 202, no. 4 (1988): 295–300. http://dx.doi.org/10.1243/pime_proc_1988_202_122_02.

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Measurements of the mean axial and radial components of velocity, the r.m.s. of the corresponding fluctuations and the wall static pressure are reported for flows through round sudden axi- and asymmetric contractions with an area ratio of 2.5 and were obtained at a Reynolds number of 40 000 based on the bulk velocity in the upstream pipe. In the axisymmetric case, the main changes in the approach velocity profiles occurred within a distance of one-half diameter upstream of the contraction, and the velocity profiles suggested that the flow separates at the entrance to the smaller diameter pipe.

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Abbate, F., A. J. Sargeant, P. W. L. Verdijk, and A. de Haan. "Effects of high-frequency initial pulses and posttetanic potentiation on power output of skeletal muscle." Journal of Applied Physiology 88, no. 1 (2000): 35–40. http://dx.doi.org/10.1152/jappl.2000.88.1.35.

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The effects of high-frequency initial pulses (HFIP) and posttetanic potentiation on mechanical power output during concentric contractions were examined in the in situ medial gastrocnemius of the rat with an intact origin on the femur and blood supply. Stimulation of the muscle was performed via the severed sciatic nerve. In the experiments, HFIP or the potentiating tetanus was followed by a stimulation of 80, 120, or 200 Hz. The results showed that both HFIP and the tetanus increased power output at high contraction velocities (>75 mm/s) when followed by a train of 80 or 120 Hz (200 Hz res

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Santos, Rute, Maria João Valamatos, Pedro Mil-Homens, and Paulo A. S. Armada-da-Silva. "Effect of Knee Angle, Contractile Activity, and Intensity of Force Production on Vastus Lateralis Stiffness: A Supersonic Shear Wave Elastography Pilot Study." Sports 12, no. 8 (2024): 211. http://dx.doi.org/10.3390/sports12080211.

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Supersonic shear image (SSI) ultrasound elastography provides a quantitative assessment of tissue stiffness using the velocity of shear waves. SSI’s great potential has allowed researchers in fields like biomechanics and muscle physiology to study the function of complex muscle groups in different conditions. The aim of this study is to use SSI to investigate changes in the stiffness of the vastus lateralis (VL) muscle as a consequence of passive elongation, isometric contraction, and repeated muscle activity. In a single session, 15 volunteers performed a series of isometric, concentric, and

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32

Farina, Dario, Marco Gazzoni, and Federico Camelia. "Conduction velocity of low-threshold motor units during ischemic contractions performed with surface EMG feedback." Journal of Applied Physiology 98, no. 4 (2005): 1487–94. http://dx.doi.org/10.1152/japplphysiol.01032.2004.

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The aim of this study was to analyze the effect of ischemia on low-threshold motor unit conduction velocity. Nine subjects were trained to isolate the activity of a single motor unit (target motor unit) in the abductor pollicis brevis muscle with feedback on surface EMG signals recorded with a 16-electrode linear array. After training, the subjects activated the target motor unit at ∼8 pulses per second (pps) for five 3-min-long contractions. During the third and fourth contractions, a cuff inflated at 180 mmHg around the forearm induced ischemia of the hand. The exerted force (mean ± SE, 4.6

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Broman, H., G. Bilotto, and C. J. De Luca. "Myoelectric signal conduction velocity and spectral parameters: influence of force and time." Journal of Applied Physiology 58, no. 5 (1985): 1428–37. http://dx.doi.org/10.1152/jappl.1985.58.5.1428.

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Reports on measurement of muscle fiber conduction velocity in humans are scarce. Inferences on the behavior of conduction velocity have been drawn from the behavior of myoelectric spectral parameters. The present report contains information on conduction velocity and spectral parameters studied at various muscle contraction levels and during and after sustained contractions. The following results have been obtained from measurements on the tibialis anterior muscle. Conduction velocity demonstrated a positive correlation with limb circumference and with muscle force output. Thus we conclude tha

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Tulapurkara, E. G., and V. V. K. Bhalla. "Experimental Investigation of Morel’s Method for Wind Tunnel Contractions." Journal of Fluids Engineering 110, no. 1 (1988): 45–47. http://dx.doi.org/10.1115/1.3243508.

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Based on a numerical study of the potential flow through contractions of chosen geometry, Morel (1975) has given a method to obtain the shape of contraction which gives small adverse pressure gradients and low nonuniformity in the velocity distribution at the exit. Two contractions with area ratios of 12 and 3.464 designed using this method are investigated experimentally. It is found that there is no separation of flow, the thickness of the boundary layer at the exit is small and the nonuniformity in velocity at the exit is smaller than the predicted value.

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Vollestad, N. K., J. Wesche, and O. M. Sejersted. "Gradual increase in leg oxygen uptake during repeated submaximal contractions in humans." Journal of Applied Physiology 68, no. 3 (1990): 1150–56. http://dx.doi.org/10.1152/jappl.1990.68.3.1150.

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We examine whether muscle oxygen consumption (VO2) increases gradually during repeated submaximal isometric contractions. Six subjects made two-legged isometric quadriceps contractions at 30% maximal voluntary contraction for 6 s with 4 s of rest between until exhaustion (58 +/- 8 min). Blood samples were taken from the femoral vein and artery, and blood velocity was recorded by ultrasound-Doppler technique in the femoral artery. Blood flow was calculated from velocity and artery diameter values. Leg VO2 increased sixfold within the 1st min of exercise. A further doubling of the VO2 was seen d

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Willems, Mark E. T., and William T. Stauber. "Effect of Contraction History on Torque Deficits by Stretches of Active Rat Skeletal Muscles." Canadian Journal of Applied Physiology 27, no. 4 (2002): 323–35. http://dx.doi.org/10.1139/h02-018.

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Effects of contraction history on torque deficits by stretches of active skeletal muscles were examined. After three contractions using maximal and submaximal activation (80 and 20 Hz) at an ankle position of 40° (i.e., long muscle length) and with maximal activation at 120° (i.e., short muscle length), the isometric and stretch torques (15 stretches) of rat plantar flexor muscles (bout 1) were measured. Controls were unconditioned. Stretches (i.e., ankle rotation from 90° to 40°, velocity: 50°•s−1) were imposed on maximal isometric contractions at 90° (i.e. preloaded stretches). All groups pe

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Seerden, T. C., W. J. E. P. Lammers, B. Y. De Winter, J. G. De Man, and P. A. Pelckmans. "Spatiotemporal electrical and motility mapping of distension-induced propagating oscillations in the murine small intestine." American Journal of Physiology-Gastrointestinal and Liver Physiology 289, no. 6 (2005): G1043—G1051. http://dx.doi.org/10.1152/ajpgi.00205.2005.

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Since the development of knockout animals, the mouse has become an important model to study gastrointestinal motility. However, little information is available on the electrical and contractile activities induced by distension in the murine small intestine. Spatiotemporal electrical mapping and mechanical recordings were made from isolated intestinal segments from different regions of the murine small intestine during distension. The electrical activity was recorded with 16 extracellular electrodes while motility was assessed simultaneously by tracking the border movements with a digital camer

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Moreland, R. S., and S. Moreland. "Characterization of magnesium-induced contractions in detergent-skinned swine carotid media." American Journal of Physiology-Cell Physiology 260, no. 6 (1991): C1224—C1232. http://dx.doi.org/10.1152/ajpcell.1991.260.6.c1224.

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Ca(2+)-calmodulin-dependent phosphorylation of the 20-kDa smooth muscle myosin light chain (MLC) results in high shortening velocities and rapid stress development. The stress maintained after a reduction in Ca2+ is associated with a decrease in MLC phosphorylation and velocity of shortening. This Ca(2+)-dependent stress without proportional MLC phosphorylation has been termed “latch” and has been postulated to reflect a population of dephosphorylated noncycling cross bridges or “latch bridges.” Mg2+ is necessary for contraction of smooth muscle, and in high concentrations, Mg2+ elicits contra

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Rosler, K., K. E. Conley, H. Howald, C. Gerber, and H. Hoppeler. "Specificity of leg power changes to velocities used in bicycle endurance training." Journal of Applied Physiology 61, no. 1 (1986): 30–36. http://dx.doi.org/10.1152/jappl.1986.61.1.30.

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Increases in leg power production resulting from 8 wk of bicycle endurance training (30 min/day, 5 times/wk) were studied using an isokinetic dynamometer. In addition, biopsies of vastus lateralis were analyzed to characterize muscle ultrastructural changes. Performance increased on the dynamometer specifically near the estimated average knee angular velocity used during the bicycle training (200 degrees/s). Power measurements were made during the first 5 contractions (maximal power: Pmax) and last 5 contractions (final power: Pend) of 25 and 50 consecutive contractions (at 60 and 240 degrees/

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Merletti R, Lo Conte LR. "Age related changes in surface myoelectric signals." Journal of Rehabilitation Medicine 24, no. 1 (1992): 25–36. http://dx.doi.org/10.2340/16501977922536.

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The initial values and the time course of muscle fiber conduction velocity and of surface myoelectric signal spectral variables were studied during voluntary or electrically elicited contractions of the tibialis anterior muscle of 15 healthy elderly human subjects. Age ranged from 65 to 84 years. Isometric voluntary contractions were performed at 20% MVC (Maximal Voluntary Contraction) and 80% MVC for 20 s. Tetanic electrical stimulation was then applied to the main muscle motor point for 20 s with surface electrodes. Two stimulation rates (20 Hz and 40 Hz) and two stimulation amplitudes were

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Merletti, R., LR Lo Conte, C. Cisari, and MV Actis. "Age related changes in surface myoelectric signals." Journal of Rehabilitation Medicine 24, no. 1 (2020): 25–36. http://dx.doi.org/10.2340/1650197792242536.

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The initial values and the time course of muscle fiber conduction velocity and of surface myoelectric signal spectral variables were studied during voluntary or electrically elicited contractions of the tibialis anterior muscle of 15 healthy elderly human subjects. Age ranged from 65 to 84 years. Isometric voluntary contractions were performed at 20% MVC (Maximal Voluntary Contraction) and 80% MVC for 20 s. Tetanic electrical stimulation was then applied to the main muscle motor point for 20 s with surface electrodes. Two stimulation rates (20 Hz and 40 Hz) and two stimulation amplitudes were

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42

Farina, Dario, Lars Arendt-Nielsen, and Thomas Graven-Nielsen. "Spike-triggered average torque and muscle fiber conduction velocity of low-threshold motor units following submaximal endurance contractions." Journal of Applied Physiology 98, no. 4 (2005): 1495–502. http://dx.doi.org/10.1152/japplphysiol.01127.2004.

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The motor unit twitch torque is modified by sustained contraction, but the association to changes in muscle fiber electrophysiological properties is not fully known. Thus twitch torque, muscle fiber conduction velocity, and action potential properties of single motor units were assessed in 11 subjects following an isometric submaximal contraction of the tibialis anterior muscle until endurance. The volunteers activated a target motor unit at the minimum discharge rate in eight 3-min-long contractions, three before and five after an isometric contraction at 40% of the maximal torque, sustained

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Oliveira, Anderson Souza, and Francesco Negro. "Neural control of matched motor units during muscle shortening and lengthening at increasing velocities." Journal of Applied Physiology 130, no. 6 (2021): 1798–813. http://dx.doi.org/10.1152/japplphysiol.00043.2021.

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The control of movement velocity is accomplished by the modulation of the neural drive to muscle and its variation over time. In this study, we tracked motor units decomposed from HD-sEMG across shortening and lengthening contractions at increasing velocities in two submaximal load levels. We demonstrate that concentric and eccentric contractions of the tibialis anterior muscle at slow velocities are achieved by specific motor unit rate coding strategies rather than distinct recruitment schemes.

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Gilbert, R. J., and W. J. Dodds. "Effect of selective muscarinic antagonists on peristaltic contractions in opossum smooth muscle." American Journal of Physiology-Gastrointestinal and Liver Physiology 250, no. 1 (1986): G50—G59. http://dx.doi.org/10.1152/ajpgi.1986.250.1.g50.

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In this study we examined the role of M1- and M2-muscarinic receptors in the mediation of circular smooth muscle esophageal contractions elicited by pharmacological cholinergic stimulation and during peristalsis in anesthetized opossums. Esophageal-body contractions were induced by bethanechol administration, whereas peristalsis was elicited by pharyngeal stroking or cervical vagal stimulation. Contractions were measured by a low-compliance manometric recording system. The incidence and amplitude of bethanechol-induced contractions were antagonized by 4-diphenylacetoxy-n-methylpiperidine (4-DA

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Knaflitz, M., R. Merletti, and C. J. De Luca. "Inference of motor unit recruitment order in voluntary and electrically elicited contractions." Journal of Applied Physiology 68, no. 4 (1990): 1657–67. http://dx.doi.org/10.1152/jappl.1990.68.4.1657.

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The relationship between surface myoelectric signal parameters and the level of voluntary or electrically elicited contractions was studied in 32 experiments on the tibialis anterior muscle of 22 healthy human subjects. Contractions were performed at 20 and 80% of the maximum voluntary contraction torque. Two levels of stimulation current were used, yielding, respectively, a maximum M wave and an M wave approximately 30% of the maximum. A four-bar electrode probe was used to detect single- and double-differential signals from which mean and median frequency of the power spectrum and average mu

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Bullen, P. R., D. J. Cheeseman, and L. A. Hussain. "A study of Turbulent Flow in Pipe Contractions." Proceedings of the Institution of Mechanical Engineers, Part E: Journal of Process Mechanical Engineering 210, no. 3 (1996): 171–80. http://dx.doi.org/10.1243/pime_proc_1996_210_312_02.

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An experimental study of turbulent water flow through abrupt contractions was carried out in order to determine the detailed flow field. Wall static pressure measurements enabled the calculation of pressure loss coefficients for a range of contraction area ratios from 0.13 to 0.67 over a Reynolds number range of 40000–200000. The effect of variations in contraction sharpness was also established. Measurements of mean velocities and turbulence intensities were made using a two-component laser Doppler anemometer for one area ratio of 0.332 to establish the detailed flow features.

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Pedersen, SW, and B. Oberg. "Stretch-shortening contraction in Parkinson patients: evidence of normal muscle contraction execution with low efficiency." Journal of Rehabilitation Medicine 29, no. 4 (1997): 251–55. http://dx.doi.org/10.2340/165019771997251255.

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The aim of this study was to compare different muscle contraction types in Parkinson patients and controls. Ten patients with mild to moderate Parkinsonism (7 men, 3 women, mean age 62.3) and 11 controls (7 men, 4 women, mean age 66.0) were investigated. Measurements in eccentric, concentric contraction and stretch-shortening contraction were made using modified Cybex 11 equipment. The torque areas in ankle dorsiflexors at 30 degrees/second, 120 degrees/second and 180 degrees/second were measured. The power (Nm/second) was calculated in a defined range of motion. The power at different angular

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Warren, Gordon L., John M. Fennessy, and Melinda L. Millard-Stafford. "Strength loss after eccentric contractions is unaffected by creatine supplementation." Journal of Applied Physiology 89, no. 2 (2000): 557–62. http://dx.doi.org/10.1152/jappl.2000.89.2.557.

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This study's objective was to determine whether 14 days of dietary creatine supplementation preceding an injurious bout of eccentric contractions affect the in vivo strength loss of mouse anterior crural muscles. Three groups of nine mice each were fed a meal diet for 14 days, one group at each of three levels of creatine supplementation (i.e., 0, 0.5, and 1% creatine). Electrically stimulated concentric, isometric, and eccentric contraction torques produced about the ankle were measured both before and after a bout of 150 eccentric contractions. Tibialis anterior muscle creatine concentration

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Murphy, Richard A., and Christopher M. Rembold. "The latch-bridge hypothesis of smooth muscle contraction." Canadian Journal of Physiology and Pharmacology 83, no. 10 (2005): 857–64. http://dx.doi.org/10.1139/y05-090.

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In contrast to striated muscle, both normalized force and shortening velocities are regulated functions of cross-bridge phosphorylation in smooth muscle. Physiologically this is manifested as relatively fast rates of contraction associated with transiently high levels of cross-bridge phosphorylation. In sustained contractions, Ca2+, cross-bridge phosphorylation, and ATP consumption rates fall, a phenomenon termed "latch". This review focuses on the Hai and Murphy (1988a) model that predicted the highly non-linear dependence of force on phosphorylation and a directly proportional dependence of

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Zehr, E. Paul, and Digby G. Sale. "Ballistic Movement: Muscle Activation and Neuromuscular Adaptation." Canadian Journal of Applied Physiology 19, no. 4 (1994): 363–78. http://dx.doi.org/10.1139/h94-030.

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Movements that are performed with maximal velocity and acceleration can be considered ballistic actions. Ballistic actions are characterized by high firing rates, brief contraction times, and high rates of force development. A characteristic triphasic agonist/antagonist/agonist electromyographic (EMG) burst pattern occurs during ballistic movement, wherein the amount and intensity of antagonist coactivation is variable. In conditions of low-grade tonic muscular activity, a premovement EMG depression (PMD; or silent period, PMS) can occur in agonist muscles prior to ballistic contraction. The a

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