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.

Preliminary Evaluation of a Weibull Function for Fitting Slow-Component Eye Velocity over the Time Course of Caloric-Induced Nystagmus

1989 ◽  
Vol 32 (3) ◽  
pp. 681-687 ◽  
Author(s):  
C. Formby ◽  
B. Albritton ◽  
I. M. Rivera
Keyword(s):  
Time Course ◽  
Slow Component ◽  
Weibull Function ◽  
Preliminary Evaluation ◽  
Mathematical Function ◽  
Before And After ◽  
Best Fitting ◽  
Eye Velocity ◽  
Fitting Parameters ◽  
Weibull Equation

We describe preliminary attempts to fit a mathematical function to the slow-component eye velocity (SCV) over the time course of caloric-induced nystagmus. Initially, we consider a Weibull equation with three parameters. These parameters are estimated by a least-squares procedure to fit digitized SCV data. We present examples of SCV data and fitted curves to show how adjustments in the parameters of the model affect the fitted curve. The best fitting parameters are presented for curves fit to 120 warm caloric responses. The fitting parameters and the efficacy of the fitted curves are compared before and after the SCV data were smoothed to reduce response variability. We also consider a more flexible four-parameter Weibull equation that, for 98% of the smoothed caloric responses, yields fits that describe the data more precisely than a line through the mean. Finally, we consider advantages and problems in fitting the Weibull function to caloric data.

The Effect of Heating and Cooling on Time Course of Voluntary and Electrically Induced Muscle Force Variation

Medicina ◽  
2011 ◽  
Vol 47 (1) ◽  
pp. 6 ◽  
Author(s):  
◽  
◽  
◽  
◽  
Keyword(s):  
Muscle Fatigue ◽  
Time Course ◽  
Muscle Force ◽  
Peak Torque ◽  
Voluntary Contraction ◽  
Knee Extensors ◽  
Lower Body ◽  
Heating And Cooling ◽  
Force Variation ◽  
Voluntary Contractions

The aim of this study was to investigate the effect of heating and cooling on time course of voluntary and electrically induced muscle force variation. Material and Methods. Ten volunteers performed 50 maximal voluntary and electrically induced contractions of the knee extensors at an angle of 120 degrees under the control conditions and after passive lower body heating and cooling in the control, heating, and cooling experiments. Peak torque, torque variation, and half-relaxation time were assessed during the exercise. Results. Passive lower body heating increased muscle and core temperatures, while cooling lowered muscle temperature, but did not affect core temperature. We observed significantly lower muscle fatigue during voluntary contraction compared with electrically induced contractions. Body heating (opposite to cooling) increased involuntarily induced muscle force, but caused greater electrically induced muscle fatigue. In the middle of the exercise, the coefficient of correlation for electrically induced muscle torque decreased significantly as compared with the beginning of the exercise, while during maximal voluntary contractions, this relation for torque remained significant until the end of the exercise. Conclusion. It was shown that time course of voluntary contraction was more stable than in electrically induced contractions.

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.

Sources of activator calcium in rabbit basilar artery

1981 ◽  
Vol 241 (2) ◽  
pp. H129-H133 ◽  
Author(s):  
T. A. McCalden ◽  
J. A. Bevan
Keyword(s):  
Basilar Artery ◽  
Time Course ◽  
Slow Component ◽  
Krebs Solution ◽  
Phasic Contraction ◽  
Intracellular Pool ◽  
Ear Artery ◽  
High K ◽  
Before And After ◽  
K Response

The responses of segments of rabbit basilar and ear arteries to high K+ (K+, 45 mM), norepinephrine (NE, 10(-5) and 10(-7) M), and 5-hydroxytryptamine (5-HT, 10(-7) M) were tested before and after their incubation in calcium (Ca2+)-free Krebs solution for times varying from 2.5 to 60 min. The time course of evolution of the responses to K+ with Ca2+-free conditions in both vessels could be represented by a monoexponential curve. The rates of decline of the responses of amines in the ear artery were similar to K+ at first but then fell off at a slower rate. The decline in K+ contraction and the fast initial decline of the NE contraction may relate to the speed of removal of extracellular calcium, whereas the final slower NE decline reflects depletion of an intracellular pool. In the basilar artery, the NE and K+ response declined in a similar manner, whereas the 5-HT contraction showed a fast and a slow component of decline. These results for the maintained agonist response were confirmed using the Ca2+ influx antagonist, 3-methoxyverapamil (D 600). In addition, a D 600-insensitive phasic contraction was observed in both arteries. These results suggest that the steady-state NE contraction in the basilar artery is almost entirely dependent on loosely bound extracellular Ca2+. This is in contrast to the ear artery, where an additional tightly bound or intracellular Ca2+ pool is used. This source is present in the basilar artery but contributes only to a D 600-insensitive phasic component.

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.

scholarly journals Skeletal muscle fatigue precedes the slow component of oxygen uptake kinetics during exercise in humans

2011 ◽  
Vol 589 (3) ◽  
pp. 727-739 ◽  
Author(s):  
Daniel T. Cannon ◽  
Ailish C. White ◽  
Melina F. Andriano ◽  
Fred W. Kolkhorst ◽  
Harry B. Rossiter
Keyword(s):  
Skeletal Muscle ◽  
Oxygen Uptake ◽  
Muscle Fatigue ◽  
Slow Component ◽  
Oxygen Uptake Kinetics ◽  
Uptake Kinetics ◽  
Skeletal Muscle Fatigue ◽  
Exercise In Humans

The Effect of Muscle Fatigue on Muscle Force-Couple Activation of the Shoulder

2001 ◽  
Vol 10 (4) ◽  
pp. 246-256 ◽  
Author(s):  
Timothy J. Henry ◽  
Scott M. Lephart ◽  
Jorge Giraldo ◽  
David Stone ◽  
Freddie H. Fu
Keyword(s):  
Muscle Fatigue ◽  
Outcome Measures ◽  
Muscle Force ◽  
Glenohumeral Joint ◽  
Previous History ◽  
Type Design ◽  
Before And After ◽  
History Of ◽  
Male Subjects ◽  
Force Couple

Context:Muscle fatigue is an important concept in regard to the muscle function of the shoulder joint. Its effect on the muscle force couples of the glenohumeral joint has not been fully identified.Objective:To examine the effects of muscle fatigue on muscle force-couple activation in the normal shoulder.Design:Pretest, posttest.Patients:Ten male subjects, age 18–30 years, with no previous history of shoulder problems.Main Outcome Measures:EMG (area) values were assessed for the anterior and middle deltoid, subscapularis, and infraspinatus muscles during 4 dynamic stabilizing exercises before and after muscle fatigue. The exercises examined were a push-up, horizontal abduction, segmental stabilization, and rotational movement on a slide board.Results:No significant differences were observed for any of the muscles tested.Conclusions:The results of our study indicate that force-couple coactivation of the glenohumeral joint is not significantly altered after muscle fatigue.

scholarly journals Measuring phenotypic flexibility by transcriptome time‐course analyses during challenge tests before and after energy restriction

2019 ◽  
Vol 33 (9) ◽  
pp. 10280-10290 ◽  
Author(s):  
Inge P. G. Bussel ◽  
Parastoo Fazelzadeh ◽  
Gary S. Frost ◽  
Milena Rundle ◽  
Lydia A. Afman
Keyword(s):  
Time Course ◽  
Energy Restriction ◽  
Phenotypic Flexibility ◽  
Before And After ◽  
Challenge Tests

Failure of prostaglandins to modulate the time course of blood flow during dynamic forearm exercise in humans

1996 ◽  
Vol 81 (4) ◽  
pp. 1516-1521 ◽  
Author(s):  
J. K. Shoemaker ◽  
H. L. Naylor ◽  
Z. I. Pozeg ◽  
R. L. Hughson
Keyword(s):  
Blood Flow ◽  
Brachial Artery ◽  
Time Course ◽  
Forearm Blood Flow ◽  
Voluntary Contraction ◽  
Double Blind ◽  
Rate Of Increase ◽  
Forearm Exercise ◽  
Blind Manner ◽  
Exercise In Humans

Shoemaker, J. K., H. L. Naylor, Z. I. Pozeg, and R. L. Hughson. Failure of prostaglandins to modulate the time course of blood flow during dynamic forearm exercise in humans. J. Appl. Physiol. 81(4): 1516–1521, 1996.—The time course and magnitude of increases in brachial artery mean blood velocity (MBV; pulsed Doppler), diameter ( D; echo Doppler), mean perfusion pressure (MPP; Finapres), shear rate (γ˙ = 8 ⋅ MBV/ D), and forearm blood flow (FBF = MBV ⋅ π r 2) were assessed to investigate the effect that prostaglandins (PGs) have on the hyperemic response on going from rest to rhythmic exercise in humans. While supine, eight healthy men performed 5 min of dynamic handgrip exercise by alternately raising and lowering a 4.4-kg weight (∼10% maximal voluntary contraction) with a work-to-rest cycle of 1:1 (s/s). When the exercise was performed with the arm positioned below the heart, the rate of increase in MBV and γ˙ was faster compared with the same exercise performed above the heart. Ibuprofen (Ibu; 1,200 mg/day, to reduce PG-induced vasodilation) and placebo were administered orally for 2 days before two separate testing sessions in a double-blind manner. Resting heart rate was reduced in Ibu (52 ± 3 beats/min) compared with placebo (57 ± 3 beats/min) ( P < 0.05) without change to MPP. With placebo, D increased in both arm positions from ∼4.3 mm at rest to ∼4.5 mm at 5 min of exercise ( P < 0.05). This response was not altered with Ibu ( P > 0.05). Ibu did not alter the time course of MBV or forearm blood flow ( P > 0.05) in either arm position. The γ˙ was significantly greater in Ibu vs. placebo at 30 and 40 s of above the heart exercise and for all time points after 25 s of below the heart exercise ( P < 0.05). Because PG inhibition altered the time course ofγ˙ at the brachial artery, but not FBF, it was concluded that PGs are not essential in regulating the blood flow responses to dynamic exercise in humans.

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