Posttetanic potentiation of human dorsiflexors

1997 ◽  
Vol 83 (6) ◽  
pp. 2131-2138 ◽  
Author(s):  
Deborah D. O’Leary ◽  
Karen Hope ◽  
Digby G. Sale
Keyword(s):  
Relaxation Time ◽  
Rise Time ◽  
Time Course ◽  
Compound Action Potential ◽  
Peak Torque ◽  
Posttetanic Potentiation ◽  
M Wave ◽  
Time To Peak ◽  
Before And After ◽  
Compound Action

O’Leary, Deborah D., Karen Hope, and Digby G. Sale.Posttetanic potentiation of human dorsiflexors. J. Appl. Physiol. 83(6): 2131–2138, 1997.—Twitch contractions of the ankle dorsiflexors were evoked before and after applied 7-s tetanic stimulation at 100 Hz in 20 young adults. Torque decreased 15% during the tetanus. At 5 s after tetanus, twitch peak torque had potentiated 45%. Potentiation declined to 28% after 1 min, rose slightly to 33% at 2 min, and declined slowly with potentiation still 25% after 5 min. There was large intersubject variation in the amount of potentiation (5–140%) and its persistence (5 to ≥20 min). The muscle compound action potential (M wave) did not change significantly (from pretetanic value) at 5 s after tetanus but increased sharply (26%) at 2 min and then subsided. Twitch half relaxation time (23%) decreased significantly more than twitch rise time (13%) 5 s after tetanus and recovered more slowly. Twitch rates of torque development (75%) and relaxation (71%) increased similarly 5 s after tetanus and were still elevated (∼25%) at 5 min. The extent of twitch torque potentiation was significantly inversely correlated with pretetanic twitch rise time ( r = −0.69), half relaxation time ( r = −0.61), and twitch-to-tetanus ratio ( r = −0.66). The data indicate that posttetanic potentiation has a greater effect on twitch half relaxation time than on time to peak torque and is more prominent in muscles with a short twitch time course and small twitch-to-tetanus ratio.

M wave potentiation during and after muscle activity

1989 ◽  
Vol 66 (6) ◽  
pp. 2606-2610 ◽  
Author(s):  
A. Hicks ◽  
J. Fenton ◽  
S. Garner ◽  
A. J. McComas
Keyword(s):  
Time Course ◽  
Compound Action Potential ◽  
Mean Amplitude ◽  
Voluntary Contraction ◽  
Maximum Increase ◽  
Maximal Increase ◽  
M Wave ◽  
Control Value ◽  
Voluntary Contractions ◽  
Compound Action

The M wave (muscle compound action potential) has been shown to enlarge between successive 3-s voluntary contractions of the human thenar and extensor digitorum brevis (EDB) muscles. The changes, which affected both the amplitude and the area of the M wave, were more obvious in the thenar than in the EDB muscles. In the thenar muscles the mean amplitude was already significantly enlarged after the first voluntary contraction and close to the maximal value by the third (mean maximal increase 23.6 +/- 12.6% of control). The increase in mean M wave area was more gradual, reaching a maximum of 29.3 +/- 14.1% at 100 s. After the voluntary thenar contractions ceased, the amplitude of the M wave subsided more rapidly than the area and had regained the control value within 50 s. The magnitude and time course of the increase in EDB M wave area (maximum change 25.9 +/- 15.2%) were similar to those of the thenar muscles; however, the subsequent decline was slower. The amplitude of the EDB M wave showed the least change, and the maximum increase (11.4 +/- 9.6%) occurred early in the postcontraction period. In both muscles the changes in M wave amplitude and area were significantly different from the control values.

Effect of temperature on post-tetanic potentiation in human dorsiflexor muscles

2001 ◽  
Vol 79 (1) ◽  
pp. 49-58 ◽  
Author(s):  
E Roderich Gossen ◽  
Kerry Allingham ◽  
Digby G Sale
Keyword(s):  
Relaxation Time ◽  
Rise Time ◽  
Wave Amplitude ◽  
Test Period ◽  
Warm Water ◽  
Effect Of Temperature ◽  
Type I ◽  
M Wave ◽  
Exposure To Cold ◽  
Post Tetanic Potentiation

The effect of temperature on post-tetanic potentiation (PTP) has been examined in the muscles of small mammals but not in human skeletal muscle. We examined PTP in the ankle dorsiflexor muscles of 10 young men by evoking twitches before and after a 7-second tetanus at 100 Hz in a control (room air ~21°C) condition and after immersion of the lower leg in warm (45°C) and cold (10°C) water baths for 30 min. Exposure to cold decreased tetanus and pre-tetanus twitch peak torque, but increased rise time, half-relaxation time, and muscle action potential (M-wave) amplitude; exposure to warm water had little effect. PTP was smallest in cold exposure 5 s post-tetanus, but persisted throughout the 12 min test period, whereas PTP had subsided by 6 min post-tetanus in control and warm exposures. M-wave amplitude initially decreased after exposure to warm water, recovered, then decreased again by 11 min post-tetanus. In contrast, exposure to cold had no initial effect but did increase the M-wave amplitude during the last half of the 12 min test period, similar to that seen in the control. The greatest immediate decrease in rise time and half-relaxation time was observed in the control; however, by 12 min post-tetanus warm exposure showed the greatest increase in rise time and half-relaxation time above pre-tetanus values. The decrease in the unpotentiated twitch torque with cooling in human dorsiflexors is typical for muscles with a predominance of type I (slow) fibres. The effect of cold on PTP is similar to that seen previously in mammalian muscles with a predominance of type II (fast) fibres, although the underlying mechanism of the cooling effect appears to differ.Key words: contraction, muscle, twitch.

The effects of priming exercise on the V̇O2 slow component and the time-course of muscle fatigue during very-heavy-intensity exercise in humans

2018 ◽  
Vol 43 (9) ◽  
pp. 909-919 ◽  
Author(s):  
Paulo Cesar do Nascimento Salvador ◽  
Kristopher Mendes de Souza ◽  
Ricardo Dantas De Lucas ◽  
Luiz Guilherme Antonacci Guglielmo ◽  
Benedito Sérgio Denadai
Keyword(s):  
Muscle Fatigue ◽  
Time Course ◽  
Slow Component ◽  
Peak Torque ◽  
Fixed Amount ◽  
Prior Exercise ◽  
Before And After ◽  
Priming Exercise ◽  
Male Subjects ◽  
Exercise In Humans

We hypothesized that prior exercise would attenuate the muscle fatigue accompanied by oxygen uptake slow-component (V̇O2SC) behavior during a subsequent very-heavy (VH)-intensity cycling exercise. Thirteen healthy male subjects performed tests to determine the critical power (CP) and the fixed amount of work above CP ([Formula: see text]) and performed 6 square-wave bouts until 3 or 8 min, each at a work rate set to deplete 70% [Formula: see text] in 8 min, with a maximal isokinetic effort before and after the conditions without (VHCON) and with prior exercise (VHEXP), to measure the cycling peak torque decrement. The V̇O2SC magnitude at 3 min (VHCON = 0.280 ± 0.234, VHEXP = 0.116 ± 0.109 L·min−1; p = 0.04) and the V̇O2SC trajectory were significantly lower for VHEXP (VHCON = 0.108 ± 0.042, VHEXP = 0.063 ± 0.031 L·min−2; p < 0.01), leading to a V̇O2SC magnitude at the eighth minute that was significantly lower than VHCON (VHCON = 0.626 ± 0.296 L·min−1, VHEXP = 0.337 ± 0.179; p < 0.01). Conversely, peak torque progressively decreased from pre-exercise to 3 min (Δtorque = 21.5 ± 7.7 vs. 19.6 ± 9.2 Nm) and to 8 min (Δtorque = 29.4 ± 15.8 vs. 27.5 ± 12.0 Nm) at VHCON and VHEXP, respectively, without significant differences between conditions. Regardless of the condition, there was a significant relationship between Δtorque and the V̇O2SC (R2: VHCON = 0.23, VHEXP = 0.25; p = 0.01). Considering that “priming” effects on the V̇O2SC were not accompanied by the muscle force behavior, these findings do not support the hypothesis of a “causal” relationship between the time-course of muscle fatigue and V̇O2SC.

scholarly journals Musculoskeletal Outcomes from Chronic High-Speed High-Impact Resistive Exercise

2019 ◽  
Vol 7 (1) ◽  
pp. 22-32 ◽  
Author(s):  
L. Chen ◽  
E.A. Selimovic ◽  
M. Daunis ◽  
T.A. Bayers T ◽  
L.J. Vargas ◽  
...  
Keyword(s):  
Repeated Measures ◽  
High Speed ◽  
Time Course ◽  
Exercise Intervention ◽  
Knee Extensor ◽  
Peak Torque ◽  
Resistive Exercise ◽  
Before And After ◽  
Independent Variable ◽  
Over Time

AbstractSubjects (n=13) did 30 workouts with their left leg on an Inertial Exercise Trainer (IET), while their right leg served as an untreated control. Before and after the 30 workouts, they underwent isokinetic strength tests (knee and ankle extensors of both legs) whose peak torque (PT), time to PT (TTPT), and rate of torque development (RTD) values were each analyzed with 2(leg)×2(time)×3(velocity) analysis of variances (ANOVAs), with repeated measures per independent variable. Peak force (PF) and total work (TW) data were measured from each IET workout, and they represent time course strength changes produced by our exercise intervention. PF and TW values for the three IET exercises that comprised each workout were each analyzed with one-way ANOVAs with time as the independent variable. Results included significant ankle and knee extensor PT increases, whereby the left leg achieved higher values at posttesting, but there were no significant TTPT changes and a time effect for ankle extensor RTD. Our data show that PF and TW each had significant increases over time, with the latter exhibiting greater gains over the 30-workout intervention. Our results imply that the IET yields strength gains over time comparable to standard resistive exercise hardware.

scholarly journals Passive Stiffness and Maximal and Explosive Strength Responses After an Acute Bout of Constant-Tension Stretching

2019 ◽  
Vol 54 (5) ◽  
pp. 519-526 ◽  
Author(s):  
Ty B. Palmer ◽  
Ryan M. Thiele
Keyword(s):  
Time Course ◽  
Outcome Measurement ◽  
Peak Torque ◽  
Passive Stiffness ◽  
Explosive Strength ◽  
Rate Of Torque Development ◽  
Short Bout ◽  
Constant Tension ◽  
Before And After ◽  
Torque Development

Context Constant-tension (CT) stretching has been used to reduce hamstrings passive stiffness; however, the time course of hamstrings stiffness responses during a short bout of this type of stretching and the effects on maximal and explosive strength remain unclear. Objective To examine the time course of hamstrings passive-stiffness responses during a short, practical bout of manual straight-legged–raise (SLR) CT passive stretches and their effects on maximal and explosive strength in healthy young women. Design Descriptive laboratory study. Setting Research laboratory. Patients or Other Participants Eleven healthy women (age = 24 ± 4 years, height = 167 ± 4 cm, mass = 65 ± 8 kg) participated. Intervention(s) Participants underwent four 15-second SLR CT passive stretches of the hamstrings. Main Outcome Measurement(s) Hamstrings passive stiffness was calculated from the slopes of the initial (phase 1) and final (phase 2) portions of the angle-torque curves generated before and after the stretching intervention and at the beginning of each 15-second stretch. Hamstrings peak torque and rate of torque development were derived from maximal voluntary isometric contractions performed before and after the stretching intervention. Results The slope coefficients (collapsed across phase) for the third and fourth stretches and the poststretching assessment were lower than the prestretching assessment (P range = .004–.04), but they were not different from each other (P &gt; .99). In addition, no differences in peak torque (t10 = −0.375, P = .72) or rate of torque development (t10 = −0.423, P = .68) were observed between prestretching and poststretching. Conclusions A short bout of SLR CT passive stretching may effectively reduce hamstrings stiffness without negatively influencing maximal and explosive strength.

Influence of argon laser stapedotomy on inner ear function and temperature

1983 ◽  
Vol 91 (5) ◽  
pp. 521-526 ◽  
Author(s):  
Michael Vollrath ◽  
Christoph Schreiner
Keyword(s):  
Action Potential ◽  
Inner Ear ◽  
Guinea Pigs ◽  
Time Course ◽  
Argon Laser ◽  
Compound Action Potential ◽  
Clinical Use ◽  
Cochlear Microphonics ◽  
Temperature Changes ◽  
Compound Action

The influence of argon laser stapedotomy on inner ear function was investigated in guinea pigs. The cochlear microphonics (CM) and the compound action potential (CAP) served as parameters for the functional status of the cochlear. Transitory depression of both potentials was found during and after laser stapedotomy. The time course of CM and CAP depression and recovery is compared to endocochlear temperature changes. Possible implications for clinical use are discussed.

Quinine Affects the Response Properties of Compound Action Potentials Elicited by Periodic Click Trains

2002 ◽  
Vol 111 (5) ◽  
pp. 423-429 ◽  
Author(s):  
Kentaro Ochi ◽  
Mutsumi Kenmochi ◽  
Toru Ohashi ◽  
Hitoshi Kikuchi ◽  
Hirotsugu Kinoshita ◽  
...  
Keyword(s):  
Body Weight ◽  
Action Potentials ◽  
Round Window ◽  
Compound Action Potential ◽  
Experimental Session ◽  
Quinine Hydrochloride ◽  
Before And After ◽  
Compound Action Potentials ◽  
Click Train ◽  
Compound Action

The effects of systemically applied quinine on the compound action potential (CAP) were investigated in 5 guinea pigs. A dose of 200 mg/kg body weight of quinine hydrochloride was administered intramuscularly, and CAPs were recorded at the round window before and after administration. The CAP thresholds of the animals were elevated by 5 to 25 dB approximately 30 minutes after administration, and thresholds recovered in some animals during the experimental session. The CAP waveform elicited by the click train stimulus was abnormal after administration of quinine. The amplitude of the CAPs elicited by the second click was larger than that of those elicited by the first click. These changes may be induced by an abnormally broadened N1 response to the first click in the click train following quinine administration. In contrast, the CAP waveforms elicited by the second click and by the following clicks in the click train appeared normal.

Influence of gender on post-tetanic potentiation in human dorsiflexors

1998 ◽  
Vol 76 (7-8) ◽  
pp. 772-779 ◽  
Author(s):  
Deborah D O'Leary ◽  
Karen Hope ◽  
Digby G Sale
Keyword(s):  
Gender Difference ◽  
Young Women ◽  
Rise Time ◽  
Peak Torque ◽  
Similar Amount ◽  
Muscle Twitch ◽  
Rate Of Torque Development ◽  
Before And After ◽  
Post Tetanic Potentiation ◽  
Torque Development

Twitch contractions of the ankle dorsiflexors were evoked before and after 7 s of tetanic stimulation at 100 Hz in young women and men. Torque decreased more in men (18%) than in women (12%) during the tetanus. There was no gender difference in twitch peak torque potentiation over the 5-min post-tetanus. Potentiation was 42% (women) and 45% (men) at 5 s post-tetanus, and still present at 5 min (women 24%, men 25%). The immediate (5 s) shortening of twitch rise time was similar in women (14%) and men (13%), but during the 5-min men's rise time came to exceed whereas women's only approached pretetanus values (e.g., +9% vs. -1% at 5 min). The immediate decrease in half-relaxation time was also similar in women (24%) and men (22%); however, women's but not men's values remained less than pretetanus values for most of the 5-min period. Twitch rate of torque development increased similarly (75%) in women and men at 5 s, with no gender difference over 5 min. In contrast, rate of torque relaxation increased significantly only in men. Rate of torque development normalized to peak torque was similar in women and men pretetanus and increased similarly 5 s post-tetanus, but women had greater values through most of the 5-min post-tetanus. Normalized rate of torque relaxation was similar in women and men and not affected by tetanus. In the dorsiflexor muscles, young women and men show a similar amount and pattern of twitch force potentiation, but there are gender differences in time-related twitch contractile properties in the first 5 min after tetanus.Key words: contraction, muscle, twitch.

Reliability of Measuring Voluntary Strength and Isometric Twitch Properties in the Ankle Muscles of Very Old Adults

1998 ◽  
Vol 6 (3) ◽  
pp. 222-231 ◽  
Author(s):  
Karen J. Winegard ◽  
Audrey L. Hicks ◽  
Anthony A. Vandervoort
Keyword(s):  
Relaxation Time ◽  
Intraclass Correlation ◽  
Peak Torque ◽  
Very Old ◽  
Old Adults ◽  
Time To Peak ◽  
Ankle Muscle ◽  
Muscle Groups ◽  
Isometric Twitch ◽  
Voluntary Strength

The purpose of this study was to assess the reliability of measuring voluntary isometric strength, evoked isometric twitch properties (peak torque, time to peak torque, half-relaxation time), M-wave amplitude, and passive tension in very old adults (73-92 years). Five male and 5 female subjects were tested on two different test occasions that were 1 week apart. Using the intraclass correlation coefficient (ICC) method, the mean reliability coefficient of all measurements on the dorsiflexor (DF) and plantar flexor (PF) muscle groups was .91 ± .05. Similar ICC values were found for DF and PF muscles (.92 ± .04 and .90 ± .05, respectively). Resting PF half-relaxation time was the least reliable measure, with an ICC value of .80, while maximum voluntary strength was the most reliable with ICC values of .98 for DF and .97 for PF. The variation ranged from 0.2 to 12.3%. It was concluded that ankle muscle function (both voluntary and evoked) can be reliably assessed in this very old age group.

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