Isometric torque and shortening velocity following fatigue and recovery of different voluntary tasks in the dorsiflexors

2009 ◽  
Vol 34 (5) ◽  
pp. 866-874 ◽  
Author(s):  
Arthur J. Cheng ◽  
Charles L. Rice
Keyword(s):  
Maximum Rate ◽  
Maximum Voluntary Contraction ◽  
Voluntary Contraction ◽  
Shortening Velocity ◽  
Related Factors ◽  
Task Failure ◽  
Young Males ◽  
Dynamic Task ◽  
Dynamic Contractions ◽  
Isometric Torque

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 fewer contractions to task failure than the isometric task, indicating a faster development of fatigue during the velocity-dependent dynamic contractions. Peripheral factors, rather than impairments in voluntary drive, were responsible for the equivalent decrease in MVC torque at task failure and its subsequent incomplete recovery. These included, for both tasks, similar changes during fatigue and recovery in voluntary isometric MVC torque, shortening velocity, stimulated twitch and 50 Hz torque, and 50 Hz maximum rate of relaxation. Irrespective of the task, however, the greater reduction in shortening velocity at task failure and its subsequent faster recovery than MVC torque suggest that changes in metabolites affect velocity to a greater extent than isometric torque.

scholarly journals “Just One More Rep!” – Ability to Predict Proximity to Task Failure in Resistance Trained Persons

2020 ◽  
Vol 11 ◽  
Author(s):  
Cedrik Armes ◽  
Henry Standish-Hunt ◽  
Patroklos Androulakis-Korakakis ◽  
Nick Michalopoulos ◽  
Tsvetelina Georgieva ◽  
...  
Keyword(s):  
Resistance Training ◽  
Maximum Voluntary Contraction ◽  
Voluntary Contraction ◽  
Separate Experiment ◽  
Training Experience ◽  
Repetition Maximum ◽  
Task Failure ◽  
Analytic Estimate ◽  
Maximum Effort ◽  
Single Repetition

In resistance training, the use of predicting proximity to momentary task failure (MF, i.e., maximum effort), and repetitions in reserve scales specifically, is a growing approach to monitoring and controlling effort. However, its validity is reliant upon accuracy in the ability to predict MF which may be affected by congruence of the perception of effort compared with the actual effort required. The present study examined participants with at least 1 year of resistance training experience predicting their proximity to MF in two different experiments using a deception design. Within each experiment participants performed four trials of knee extensions with single sets (i.e., bouts of repetitions) to their self-determined repetition maximum (sdRM; when they predicted they could not complete the next repetition if attempted and thus would reach MF if they did) and MF (i.e., where despite attempting to do so they could not complete the current repetition). For the first experiment (n = 14) participants used loads equal to 70% of a one repetition maximum (1RM; i.e., the heaviest load that could be lifted for a single repetition) performed in a separate baseline session. Aiming to minimize participants between day variability in repetition performances, in the second separate experiment (n = 24) they used loads equal to 70% of their daily isometric maximum voluntary contraction (MVC). Results suggested that participants typically under predicted the number of repetitions they could perform to MF with a meta-analytic estimate across experiments of 2.0 [95%CIs 0.0 to 4.0]. Participants with at least 1 year of resistance training experience are likely not adequately accurate at gauging effort in submaximal conditions. This suggests that perceptions of effort during resistance training task performance may not be congruent with the actual effort required. This has implications for controlling, programming, and manipulating the actual effort in resistance training and potentially on the magnitude of desired adaptations such as improvements in muscular hypertrophy and strength.

Activation varies among the knee extensor muscles during a submaximal fatiguing contraction in the seated and supine postures

2003 ◽  
Vol 95 (4) ◽  
pp. 1515-1522 ◽  
Author(s):  
L Rochette ◽  
S. K. Hunter ◽  
N Place ◽  
R Lepers
Keyword(s):  
Vastus Lateralis ◽  
Maximum Voluntary Contraction ◽  
Knee Extensor ◽  
Voluntary Contraction ◽  
Emg Activity ◽  
Task Failure ◽  
Rate Of Increase ◽  
Extensor Muscles ◽  
Seated Posture ◽  
Knee Extensor Muscles

Ten young men sustained an isometric contraction of the knee extensor muscles at 20% of the maximum voluntary contraction (MVC) torque on three separate occasions in a seated posture. Subjects performed an isometric knee extension contraction on a fourth occasion in a supine posture. The time to task failure for the seated posture was similar across sessions (291 ± 84 s; P > 0.05), and the MVC torque was similarly reduced across sessions after the fatiguing contraction (42 ± 12%). The rate of increase in electromyograph (EMG) activity (%MVC) and torque fluctuations during the fatiguing contractions were similar across sessions. However, the rate of increase in EMG differed among the knee extensor muscles: the rectus femoris began at a greater amplitude (31.5 ± 11.0%) compared with the vastus lateralis and vastus medialis muscles (18.8 ± 5.3%), but it ended at a similar value (45.4 ± 3.1%). The time to task failure and increase in EMG activity were similar for the seated and supine tasks; however, the reduction in MVC torque was greater for the seated posture. These findings indicate that the time to task failure for the knee extensor muscles that have a common tendon insertion did not alter over repeat sessions as had been observed for the elbow flexor muscles (Hunter SK and Enoka RM. J Appl Physiol 94: 108-118, 2003).

FORCE SUMMATION AND TWITCH POTENTIATION CAPACITY IN HUMAN ANKLE PLANTAR- AND DORSI-FLEXOR MUSCLES

2014 ◽  
Vol 17 (04) ◽  
pp. 1450015
Author(s):  
Yoichi Ohta ◽  
Kengo Yotani
Keyword(s):  
Muscle Function ◽  
Pulse Train ◽  
Maximum Voluntary Contraction ◽  
Voluntary Contraction ◽  
Twitch Potentiation ◽  
Flexor Muscles ◽  
Human Ankle ◽  
Before And After ◽  
Isometric Torque ◽  
Plantar Flexor Muscles

Purpose: The present study aimed to clarify inter-individual correlation between the magnitudes of force summation and the post-activation potentiation (PAP), in human ankle plantar- and dorsi-flexor muscles. Methods: We analyzed 10 male participants plantar-flexor muscles and the 12 male participants dorsi-flexor muscles using a database from a previous study. Before and after maximum voluntary contraction, we measured the amount of isometric torque evoked by a single, double- and triple-pulse train stimulus. Results: The magnitude of PAP was significantly positively correlated with the magnitude of force summation in both the plantar- and dorsi-flexor muscles. Conclusions: The present study confirmed the correlation between the magnitudes of force summation and PAP in human ankle plantar- and dorsi-flexor muscles. This suggests that muscle characteristics affecting the force summation capacity depend on the PAP, to some degree. These results suggest that the combination of both parameters might enhance the usefulness of evaluating changes in muscle function using intrinsic contractile properties.

scholarly journals An electromyographic assessment pilot study on the reliability of the forearm muscles during multi-planar maximum voluntary contraction grip and wrist articulation in young males

2021 ◽  
pp. 1-12
Author(s):  
Henry H. Hunter ◽  
Graeme G. Sorbie ◽  
Fergal M. Grace ◽  
Yaodong Gu ◽  
Wing-Kai Lam ◽  
...  
Keyword(s):  
Experimental Data ◽  
Clinical Practice ◽  
Pilot Study ◽  
Maximum Voluntary Contraction ◽  
Scientific Research ◽  
Voluntary Contraction ◽  
Young Males ◽  
Forearm Muscles

BACKGROUND: Electromyographic systems are widely used in scientific and clinical practice. The reproducibility and reliability of these measures are crucial when conducting scientific research and collecting experimental data.

Sweating response to passive stretch of the calf muscle during activation of forearm muscle metaboreceptors in heated humans

2014 ◽  
Vol 306 (10) ◽  
pp. R728-R734 ◽  
Author(s):  
Tatsuro Amano ◽  
Masashi Ichinose ◽  
Takeshi Nishiyasu ◽  
Yoshimitsu Inoue ◽  
Shunsaku Koga ◽  
...  
Keyword(s):  
Blood Pressure ◽  
Blood Pressure Response ◽  
Maximum Voluntary Contraction ◽  
Voluntary Contraction ◽  
Calf Muscle ◽  
Young Males ◽  
Arterial Blood ◽  
Muscle Receptors ◽  
Muscle Mechanoreceptor ◽  
Forearm Muscle

Activation of muscle metaboreceptors and mechanoreceptors has been shown to independently influence the sweating response, while their integrative control effects remain unclear. We examined the sweating response when the two muscle receptors are concurrently activated in different limbs, as well as the blood pressure response. In total, 27 young males performed passive calf muscle stretches (muscle mechanoreceptor activation) for 30 s in a semisupine position with and without postisometric handgrip exercise muscle ischemia (PEMI, muscle metaboreceptor activation) at exercise intensities of 35 and 50% of maximum voluntary contraction (MVC) under hot conditions (ambient temperature, 35°C, relative humidity, 50%). Passive calf muscle stretching alone increased the mean sweating rate significantly on the forehead, chest, and thigh (SRmean) and mean arterial blood pressure (MAP), but not the heart rate (HR), from prestretching levels by 0.04 ± 0.01 mg·cm2·min−1, 4.0 ± 1.3 mmHg ( P < 0.05), and −1.0 ± 0.5 beats/min ( P > 0.05), respectively. The SRmean and MAP during PEMI were significantly higher than those at rest. The passive calf muscle stretch during PEMI increased MAP significantly by 3.4 ± 1.0 and 2.0 ± 0.7 mmHg for 35 and 50% of MVC, respectively ( P < 0.05), but not that of SRmean or HR at either exercise intensity. These results suggest that sweating and blood pressure responses to concurrent activation of the two muscle receptors in different limbs differ and that the influence of calf muscle mechanoreceptor activation alone on the sweating response disappears during forearm muscle metaboreceptor activation.

Muscle sympathetic single-unit responses during rhythmic handgrip exercise and isocapnic hypoxia in males: the role of sympathoexcitation magnitude

2021 ◽  
Author(s):  
Anthony V. Incognito ◽  
André L. Teixeira ◽  
Brooke M. Shafer ◽  
Massimo Nardone ◽  
Tyler D. Vermeulen ◽  
...  
Keyword(s):  
Single Unit ◽  
Muscle Sympathetic Nerve Activity ◽  
Maximum Voluntary Contraction ◽  
Voluntary Contraction ◽  
Spike Frequency ◽  
Single Units ◽  
Response Patterns ◽  
Handgrip Exercise ◽  
Young Males ◽  
End Tidal

A small proportion of postganglionic muscle sympathetic single units can be inhibited during sympathoexcitatory stressors in humans. However, whether these responses are dependent on the specific stressor or the level of sympathoexcitation remains unclear. We hypothesize that, when matched by sympathoexcitatory magnitude, different stressors can evoke similar proportions of inhibited single units. Multiunit and single-unit muscle sympathetic nerve activity (MSNA) were recorded in seven healthy, young males at baseline and during: 1) rhythmic handgrip exercise (40% of maximum voluntary contraction) and 2) acute isocapnic hypoxia (partial pressure of end-tidal O2: 47±3 mmHg). Single units were classified as activated, nonresponsive, or inhibited if the spike frequency was above, within, or below the baseline variability, respectively. By design, rhythmic handgrip and isocapnic hypoxia similarly increased multiunit total MSNA (D273±208 vs. D254±193 AU, P=0.84) and single-unit spike frequency (D8±10 vs. D12±13 spikes/min, P=0.12). Among 19 identified single units, the proportion of activated (47% vs. 68%) non-responsive (32% vs. 16%) and inhibited (21% vs. 16%) single units were not different between rhythmic handgrip and isocapnic hypoxia (P=0.42). However, only 9 (47%) single units behaved with concordant response patterns across both stressors (7 activated, 1 non-responsive, and 1 inhibited during both stressors). During the 1-min epoch with the highest increase in total MSNA during hypoxia (D595±282 AU, P<0.01) only 1 single unit was inhibited. These findings suggest that the proportion of muscle sympathetic single units inhibited during stress are associated with the level of sympathoexcitation and not the stressor per se in healthy young males.

Fatigue and recovery of power and isometric torque following isotonic knee extensions

2005 ◽  
Vol 99 (4) ◽  
pp. 1446-1452 ◽  
Author(s):  
Arthur J. Cheng ◽  
Charles L. Rice
Keyword(s):  
Relaxation Time ◽  
Voluntary Contraction ◽  
Contractile Properties ◽  
Task Failure ◽  
Motor Unit Activation ◽  
Isometric Torque ◽  
Isotonic Function ◽  
Isotonic Contractions ◽  
Muscle Contractile ◽  
Isometric Muscle

The purpose of this study was to assess fatigue and recovery of isotonic power and isometric contractile properties after a series of maximal isotonic contractions. Using a Biodex dynamometer, 13 men [26 yr (SD 3)] performed isotonic [50% of isometric maximal voluntary contraction (MVC) every 1.2 s through 75° range of motion] single-limb knee extensions at the fastest velocity they could achieve until velocity was reduced by 35%. Time to task failure was 38 s, and, compared with baseline, power declined by ∼42% [741.0 (SD 106.0) vs. 426.5 W (SD 60.3) at task failure], and MVC declined by ∼26% [267.3 (SD 42.5) vs. 198.4 N·m (SD 45.7) at task failure]. Power recovered by 5 min, whereas MVC did not recover, and at 10 min was only ∼85% of baseline. Isometric MVC motor unit activation was ∼95% at rest and was unchanged at task failure (∼96%), but a small amount of failure was apparent between 1.5 and 10 min of recovery (∼87 to ∼91%). Half relaxation time measured from a 50-Hz isometric tetanus was significantly prolonged by ∼33% immediately after task failure but recovered by 1.5 min. A decline in the 10- to 50-Hz ratio of the evoked isometric contractions was observed at 5 and 10 min of recovery, which suggests excitation-contraction coupling impairment. Changes in velocity and half relaxation time during the protocol were strongly and negatively correlated ( r = −0.85). Thus mainly peripheral mechanisms were implicated in the substantial depression but relatively fast recovery of isotonic power. Furthermore, isometric muscle contractile properties were related to some, but not all, changes in isotonic function.

Laterality of Hand Grip and Elbow Flexion Power in Right Hand–Dominant Individuals

2009 ◽  
Vol 4 (3) ◽  
pp. 355-366 ◽  
Author(s):  
Hiroki Aoki ◽  
Shinichi Demura
Keyword(s):  
Gender Difference ◽  
Peak Power ◽  
Maximum Voluntary Contraction ◽  
Elbow Flexion ◽  
Voluntary Contraction ◽  
Power Ratio ◽  
Young Males ◽  
Left Hand ◽  
Hand Grip ◽  
Right Hand

Purpose:This study aimed to compare the laterality, and its gender difference, of hand grip and elbow flexion power according to load in right hand–dominant individuals.Results:The subjects were 15 healthy young males (age 22.1 ± 0.7 y, height 171.3 ± 3.4 cm, mass 64.5 ± 4.1 kg) and 15 healthy young females (age 22.4 ± 1.0 y, height 161.1 ± 3.0 cm, mass 55.4 ± 4.6 kg). Isotonic peak power was measured with 6 different loads ranging from 20% to 70% of maximum voluntary contraction (MVC) for grip and elbow flexion movements.Results:The peak power was significantly larger in males than in females in both movements (ratio, males:females was 58.1:49.4%). The dominant right hand had larger peak power in all loads for hand grip power (ratio, dominant:nondominant was 83.6:71.1%) and in loads of 20% to 50% MVC for elbow flexion power (88.7:85.7%) in both genders, confirming laterality in both movements. The peak power ratio of the dominant right hand to the nondomi-nant left hand was significantly larger in hand grip than in elbow flexion for all loads in females.Conclusion:Even though laterality was confirmed in both grip and elbow flexion, gender difference is more marked in hand grip.

Forearm blood flow follows work rate during submaximal dynamic forearm exercise independent of sex

2007 ◽  
Vol 103 (6) ◽  
pp. 1950-1957 ◽  
Author(s):  
Joaquin U. Gonzales ◽  
Benjamin C. Thompson ◽  
John R. Thistlethwaite ◽  
Allison J. Harper ◽  
Barry W. Scheuermann
Keyword(s):  
Blood Flow ◽  
Muscle Strength ◽  
Forearm Blood Flow ◽  
Handgrip Strength ◽  
Maximum Voluntary Contraction ◽  
Voluntary Contraction ◽  
Work Rate ◽  
Metabolic Demand ◽  
Task Failure ◽  
Forearm Exercise

To test the hypothesis that sex influences forearm blood flow (FBF) during exercise, 15 women and 16 men of similar age [women 24.3 ± 4.0 (SD) vs. men 24.9 ± 4.5 yr] but different forearm muscle strength (women 290.7 ± 44.4 vs. men 509.6 ± 97.8 N; P < 0.05) performed dynamic handgrip exercise as the same absolute workload was increased in a ramp function (0.25 W/min). Task failure was defined as the inability to maintain contraction rate. Blood pressure and FBF were measured on separate arms during exercise by auscultation and Doppler ultrasound, respectively. Muscle strength was positively correlated with endurance time ( r = 0.72, P < 0.01) such that women had a shorter time to task failure than men (450.5 ± 113.0 vs. 831.3 ± 272.9 s; P < 0.05). However, the percentage of maximal handgrip strength achieved at task failure was similar between sexes (14% maximum voluntary contraction). FBF was similar between women and men throughout exercise and at task failure (women 13.6 ± 5.3 vs. men 14.5 ± 4.9 ml·min−1·100 ml−1). Mean arterial pressure was lower in women at rest and during exercise; thus calculated forearm vascular conductance (FVC) was higher in women during exercise but similar between sexes at task failure (women 0.13 ± 0.05 vs. men 0.11 ± 0.04 ml·min−1·100 ml−1·mmHg−1). In conclusion, the similar FBF during exercise was achieved by a higher FVC in the presence of a lower MAP in women than men. Still, FBF remained coupled to work rate (and presumably metabolic demand) during exercise irrespective of sex.

scholarly journals “Just one more rep!” – Ability to predict proximity to task failure in resistance trained persons

2019 ◽  
Author(s):  
Cedrik Armes ◽  
Henry Standish-Hunt ◽  
Patroklos Androulakis-Korakakis ◽  
Nick Michalopoulos ◽  
Tsvetelina Georgieva ◽  
...  
Keyword(s):  
Resistance Training ◽  
Maximum Voluntary Contraction ◽  
Voluntary Contraction ◽  
Separate Experiment ◽  
Training Experience ◽  
Repetition Maximum ◽  
Task Failure ◽  
Analytic Estimate ◽  
Maximum Effort ◽  
One Year

In resistance training, the use of predicting proximity to momentary task failure (MF, i.e. maximum effort), and repetitions in reserve scales specifically, is a growing approach to monitoring and controlling effort. However, its validity is reliant upon accuracy in the ability to predict MF which may be affected by congruence of the perception of effort compared with the actual effort required. The present study examined participants with at least one year of resistance training experience predicting their proximity to MF in two different experiments using a deception design. Within each experiment participants performed four trials of knee extensions with single sets (i.e. bouts of repetitions) to their self-determined repetition maximum (sdRM; when they predicted they could not complete the next repetition if attempted and thus would reach MF if they did) and MF (i.e. where despite attempting to do so they could not complete the current repetition). For the first experiment (n = 14) participants used loads equal to 70% of a one repetition maximum (1RM; i.e. the heaviest load that could be lifted for a single repetition) performed in a separate baseline session. Aiming to minimize participants between day variability in repetition performances, in the second separate experiment (n = 24) they used loads equal to 70% of their daily isometric maximum voluntary contraction (MVC). Results suggested that participants typically under predicted the number of repetitions they could perform to MF with a meta-analytic estimate across experiments of 2.02 [95%CIs 0.0 to 4.04]. Participants with at least one year of resistance training experience are likely not adequately accurate at gauging effort in submaximal conditions. This suggests that perceptions of effort during resistance training task performance may not be congruent with the actual effort required. This has implications for controlling, programming, and manipulating the actual effort in resistance training and potentially on the magnitude of desired adaptations such as improvements in muscular hypertrophy and strength.

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