Interactions between fatiguing and nonfatiguing isometric contractions

1981 ◽  
Vol 51 (2) ◽  
pp. 399-404 ◽  
Author(s):  
D. E. Stafford ◽  
J. S. Petrofsky
Keyword(s):  
Isometric Contraction ◽  
Maximum Strength ◽  
Isometric Contractions ◽  
Recovery Interval ◽  
Static Effort ◽  
Series Of Experiments ◽  
Age Range ◽  
The Relationship ◽  
Male Subjects ◽  
Fatiguing Contractions

Isometric contractions of the handgrip muscles were exerted by eight male subjects (age range 19-24 yr) to determine the relationship between fatiguing and nonfatiguing isometric contractions. In a first series of experiments, subjects exerted fatiguing isometric contractions at tensions of 25, 40, or 70% of the maximum strength of the subjects (MVC) following a contraction at a nonfatiguing tension of 5 or 10% MVC for 3, 7, or 20 min. In a second series of experiments, subjects exerted pairs of fatiguing isometric contractions at the same tensions; however, during the 3-, 7-, or 20-min interval between the contractions the subjects either rested or exerted a contraction at 5 or 10% MVC. Nonfatiguing isometric contractions exerted prior to fatiguing contractions had little influence on the endurance for the fatiguing static effort. In contrast, when contractions at nonfatiguing tensions were exerted in the recovery interval following an isometric contraction at a fatiguing tension, the recovery of endurance was dramatically reduced.

scholarly journals Fatiguing effects of indirect vibration stimulation in upper limb muscles: pre, post and during isometric contractions superimposed on upper limb vibration

2019 ◽  
Vol 6 (10) ◽  
pp. 190019
Author(s):  
Amit N. Pujari ◽  
Richard D. Neilson ◽  
Marco Cardinale
Keyword(s):  
Upper Limb ◽  
Isometric Contraction ◽  
Exercise Intervention ◽  
Biceps Brachii ◽  
Whole Body ◽  
Emg Activity ◽  
Isometric Contractions ◽  
Fatigue Development ◽  
Limb Muscles ◽  
Fatiguing Contractions

Whole-body vibration and upper limb vibration (ULV) continue to gain popularity as exercise intervention for rehabilitation and sports applications. However, the fatiguing effects of indirect vibration stimulation are not yet fully understood. We investigated the effects of ULV stimulation superimposed on fatiguing isometric contractions using a purpose developed upper limb stimulation device. Thirteen healthy volunteers were exposed to both ULV superimposed to fatiguing isometric contractions (V) and isometric contractions alone Control (C). Both Vibration (V) and Control (C) exercises were performed at 80% of the maximum voluntary contractions. The stimulation used was 30 Hz frequency of 0.4 mm amplitude. Surface-electromyographic (EMG) activity of the Biceps Brachii, Triceps Brachii and Flexor Carpi Radialis were measured. EMG amplitude (EMGrms) and mean frequency (MEF) were computed to quantify muscle activity and fatigue levels. All muscles displayed significantly higher reduction in MEFs and a corresponding significant increase in EMGrms with the V than the Control, during fatiguing contractions ( p < 0.05). Post vibration, all muscles showed higher levels of MEFs after recovery compared to the control. Our results show that near-maximal isometric fatiguing contractions superimposed on vibration stimulation lead to a higher rate of fatigue development compared to the isometric contraction alone in the upper limb muscles. Results also show higher manifestation of mechanical fatigue post treatment with vibration compared to the control. Vibration superimposed on isometric contraction not only seems to alter the neuromuscular function during fatiguing efforts by inducing higher neuromuscular load but also post vibration treatment.

scholarly journals Fatiguing Effects of Indirect Vibration Stimulation in Upper Limb Muscles- pre, post and during Isometric Contractions Superimposed on Upper Limb Vibration

2018 ◽  
Author(s):  
Amit N. Pujari ◽  
Richard D. Neilson ◽  
Marco Cardinale
Keyword(s):  
Upper Limb ◽  
Isometric Contraction ◽  
Exercise Intervention ◽  
Whole Body ◽  
Emg Activity ◽  
Isometric Contractions ◽  
Vibration Treatment ◽  
Fatigue Development ◽  
Limb Muscles ◽  
Fatiguing Contractions

AbstractBackgroundIndirect vibration stimulation i.e. whole body vibration and upper limb vibration (ULV), are gaining popularity as exercise intervention for sports and rehabilitation applications. However, the fatiguing effects of indirect vibration stimulation are not yet fully understood. In addition, current vibration stimulation devices have a series of limitations. For this scope, we investigated the effects of ULV superimposed on fatiguing graded isometric contractions using a newly, purpose developed upper limb stimulation device. Twelve healthy volunteers were exposed to both ULV superimposed to fatiguing isometric contractions, at 80% of the maximum voluntary contractions (V) and just isometric contractions performed on a custom designed arm curl/flexion device- Control (C). The stimulation used consisted of 30Hz frequency of 0.4mm amplitude. Surface electromyographic (EMG) activity of the Biceps Brachii (BB), Triceps Brachii (TB), and Flexor Carpi Radialis (Forearm- FCR) were measured during both V and C conditions. EMG amplitude (EMGrms) and mean frequency (MEF) were computed to quantify muscle activity and fatigue levels respectively.ResultsAll three muscles BB, TB and FCR displayed significantly higher reduction in MEFs and corresponding significant increase in EMGrms with the V than the C, during fatiguing contractions (P < 0.05). Post vibration treatment, all muscles showed higher levels of MEFs after recovery compared to the control.ConclusionsOur results show that near maximal (80% of MVC) isometric fatiguing contractions superimposed on vibration stimulation lead to a higher rate of fatigue development compared to the isometric contraction alone in the upper limb muscles. Results also show, higher manifestation of mechanical fatigue post treatment with vibration compared to the control. Vibration superimposed on isometric contraction not only seems to alter the neuromuscular function during fatiguing efforts by inducing higher neuromuscular load but also post vibration treatment, potentially through the augmentation of stretch reflex and/or higher central motor command excitability.

Ultrastructural Study of Human Testicular Biopsies in Infertility

1976 ◽  
Vol 34 ◽  
pp. 156-157
Author(s):  
Shirley Siew ◽  
Philip Troen ◽  
Howard R. Nankin
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Basement Membrane ◽  
Leydig Cells ◽  
Clinical Evidence ◽  
Young Male ◽  
Germinal Epithelium ◽  
Transmission Electron ◽  
Age Range ◽  
Male Subjects

Testicular biopsies were obtained from six young male subjects (age range 24-33) who complained of infertility and who had clinical evidence of oligospermia. This was confirmed on histological examination which showed a broad spectrum from profound hypospermatogenesis to relatively normal appearing germinal epithelium. Thickening of the tubular walls was noted in half of the cases and slight peritubular fibrosis in one. The Leydig cells were reported as normal or unremarkable.Transmission electron microscopy showed that the thickening of the supporting tissue of the germinal epithelium was caused more by an increase in the thickness of the layers of the lamina propria than of the tubular wall itself. The changes in the basement membrane of the tubular wall consisted mostly of a greater degree of infolding into the tubule and some reduplication which gave rise to a multilayered appearance.

scholarly journals Possible Selves Across the Lifespan

2020 ◽  
Vol 4 (Supplement_1) ◽  
pp. 449-449
Author(s):  
Victoria Chen ◽  
Alysson Light
Keyword(s):  
Possible Selves ◽  
Well Being ◽  
Self Concept ◽  
Life Stages ◽  
Cross Sectional Survey ◽  
Cross Sectional ◽  
Younger Adults ◽  
Midlife Adults ◽  
Age Range ◽  
The Relationship

Abstract Possible selves are defined as “personalized representations of one’s self in future states” (Cross & Markus, 1991). Research has also found that thinking frequently about possible selves predicts lower well-being, whereas thinking clearly about possible selves is associated with higher well-being (McElwee & Haugh, 2010). However, possible selves differ across the lifespan (Hooker & Kaus, 1994; Cross & Markus, 1991) and life stages can impact exploration of possible identities (Arnett, 2000). Thus we hypothesize that the relationship between thought about possible selves and well-being differs across the lifespan. In a cross-sectional survey, 240 participants (age range: 18-92) reported on frequency and clarity of possible selves, as well as general self-clarity (Campbell et al., 1996). Results indicate curvilinear moderation by age of the link between possible self-clarity and well-being, with the association being stronger among midlife adults than among younger adults and older adults. Also, as clarity of feared possible selves increases, self-concept clarity decreases. Similarly, frequency of thinking about feared possible selves was negatively correlated with self-concept clarity. However, clarity and frequency of thought about hoped-for positive possible selves had no correlation with self-concept clarity.

Influence of submaximal isometric contractions of the hamstrings on electromyography activity and force while functioning as hip extensors

2020 ◽  
pp. 1-8
Author(s):  
Dasom Oh ◽  
Wootaek Lim
Keyword(s):  
Prone Position ◽  
Supine Position ◽  
Isometric Contraction ◽  
Muscle Length ◽  
Biceps Femoris ◽  
Emg Activity ◽  
Isometric Contractions ◽  
Significant Difference ◽  
Extension Force ◽  
Long Head

BACKGROUND: Although the medial and lateral hamstrings are clearly distinct anatomically and have different functions in the transverse plane, they are often considered as one muscle during rehabilitation. OBJECTIVE: The purpose of the study was to compare the electromyographic (EMG) activity between the prone position and the supine position during maximal isometric contraction and to additionally confirm the effect of submaximal isometric contractions on EMG activity of medial and lateral hamstrings, and force. METHODS: In the prone position, EMG activities of the long head of biceps femoris (BFLH) and semitendinosus (ST) were measured during the maximal isometric contraction. In the supine position, hip extension force with EMG activity were measured during the maximal and the submaximal isometric contractions. RESULTS: EMG activity in the prone position was significantly decreased in the supine position. In the supine position, there was a significant difference between the BFLH and ST during the maximal isometric contraction, but not during the submaximal isometric contractions. CONCLUSIONS: The dependence on the hamstrings could be relatively lower during hip extensions. When the medial and lateral hamstrings are considered separately, the lateral hamstrings may show a more active response, with increased muscle length, in clinical practice.

A controlled family study of late-onset non-affective psychosis (late paraphrenia)

1997 ◽  
Vol 170 (6) ◽  
pp. 511-514 ◽  
Author(s):  
R. J. Howard ◽  
C. Graham ◽  
P. Sham ◽  
J. Dennehey ◽  
D. J. Castle ◽  
...  
Keyword(s):  
At Risk ◽  
Late Onset ◽  
Psychiatric Morbidity ◽  
Late Life ◽  
Lifetime Risk ◽  
First Degree Relatives ◽  
Healthy Elderly ◽  
Increased Risk ◽  
Age Range ◽  
The Relationship

BackgroundThe relationship between those schizophrenia-like conditions that have their onset in late life and early-onset schizophrenia is unclear. Very few family history studies of patients with late-onset psychosis have been reported, and it is not known whether their relatives have an increased risk of psychosis.MethodInformation was collected on the psychiatric morbidity of 269 first-degree relatives of patients with schizophrenia or delusional disorder with an onset after the age of 60 (late paraphrenia), and 272 first-degree relatives of healthy elderly control subjects, using a research diagnostic instrument.ResultsWith a narrow age range (15–50 years) at risk, the estimated lifetime risk of schizophrenia was 1.3% in the relatives of both cases and controls. With a wider age range (15–90 years) at risk, estimated lifetime risk of schizophrenia was 2.3% for the relatives of cases, and 2.2% for the relatives of controls. However, depression was significantly more common among the relatives of cases than controls.ConclusionThose schizophrenia-like psychoses with onset in late life are not genetically associated with schizophrenia.

Parents’ and Siblings’ Influence On One’s Self Esteem

2017 ◽  
Vol 4 (4) ◽  
Author(s):  
Dr. Seena M. Mathai ◽  
Debolina Chatterjee ◽  
Bhuvaneswari Mohanraj
Keyword(s):  
Academic Performance ◽  
Parenting Styles ◽  
Online Survey ◽  
Self Esteem ◽  
Research Data ◽  
The Self ◽  
Native Place ◽  
Age Range ◽  
As Relationship ◽  
The Relationship

Parents and siblings play a major role in influencing the self-esteem of an individual. The parents’ relationship with the child, their responses to the child’s academic performance which includes motivation as well as encouragement plays a huge role in building up a positive self-esteem which further helps them to develop a better personality; better career along with that self-esteem also helps one to solve their problems in life. In this research, data from 112 participants were collected through an online survey focusing on the relationship between parenting styles and self-esteem across a specific age range. Parenting styles were assessed using 20 question model(What questions, while self-esteem was evaluated using Rosenberg self-esteem scale. Through this research the effect of native place on one’s self esteem was determined along with the effect of other factors such as relationship with siblings, academic performance on self-esteem was analysed

scholarly journals Effect of ingested sodium bicarbonate on muscle force, fatigue, and recovery

1997 ◽  
Vol 83 (2) ◽  
pp. 333-337 ◽  
Author(s):  
O. Verbitsky ◽  
J. Mizrahi ◽  
M. Levin ◽  
E. Isakov
Keyword(s):  
Sodium Bicarbonate ◽  
Isometric Contraction ◽  
Muscle Force ◽  
Enhanced Recovery ◽  
Maximal Oxygen Consumption ◽  
Bicycle Ergometer ◽  
Quadriceps Femoris ◽  
Acute Ingestion ◽  
Male Subjects ◽  
Femoris Muscle

Verbitsky, O., J. Mizrahi, M. Levin, and E. Isakov.Effect of ingested sodium bicarbonate on muscle force, fatigue, and recovery. J. Appl. Physiol. 83(2): 333–337, 1997.—The influence of acute ingestion of NaHCO3 on fatigue and recovery of the quadriceps femoris muscle after exercise was studied in six healthy male subjects. A bicycle ergometer was used for exercising under three loading conditions: test A, load corresponding to maximal oxygen consumption; test B, load in test A + 17%; test C, load in test B but performed 1 h after acute ingestion of NaHCO3. Functional electrical stimulation (FES) was applied to provoke isometric contraction of the quadriceps femoris. The resulting knee torque was monitored during fatigue (2-min chronic FES) and recovery (10-s FES every 10 min, for 40 min). Quadriceps torques were higher in the presence of NaHCO3( P < 0.05): with NaHCO3 the peak, residual, and recovery (after 40 min) normalized torques were, respectively, 0.68 ± 0.05 (SD), 0.58 ± 0.05, and 0.73 ± 0.05; without NaHCO3 the values were 0.45 ± 0.04, 0.30 ± 0.06, and 0.63 ± 0.06. The increased torques obtained after acute ingestion of NaHCO3 indicate the possible existence of improved nonoxidative glycolysis in isometric contraction, resulting in reduced fatigue and enhanced recovery.

Neuromuscular drive and force production are not altered during bilateral contractions

1998 ◽  
Vol 84 (1) ◽  
pp. 200-206 ◽  
Author(s):  
J. M. Jakobi ◽  
E. Cafarelli
Keyword(s):  
Motor Unit ◽  
Force Production ◽  
Young Male ◽  
Neuromuscular Control ◽  
Force Generation ◽  
Isometric Contractions ◽  
Firing Rates ◽  
Significant Limitation ◽  
Motor Unit Firing ◽  
Male Subjects

Jakobi, J. M., and E. Cafarelli. Neuromuscular drive and force production are not altered during bilateral contractions. J. Appl. Physiol. 84(1): 200–206, 1998.—Several investigators have studied the deficit in maximal voluntary force that is said to occur when bilateral muscle groups contract simultaneously. A true bilateral deficit (BLD) would suggest a significant limitation of neuromuscular control; however, some of the data from studies in the literature are equivocal. Our purpose was to determine whether there is a BLD in the knee extensors of untrained young male subjects during isometric contractions and whether this deficit is associated with a decreased activation of the quadriceps, increased activation of the antagonist muscle, or an alteration in motor unit firing rates. Twenty subjects performed unilateral (UL) and bilateral (BL) isometric knee extensions at 25, 50, 75, and 100% maximal voluntary contraction. Total UL and BL force (Δ3%) and maximal rate of force generation (Δ2.5%) were not significantly different. Total UL and BL maximal vastus lateralis electromyographic activity (EMG; 2.7 ± 0.28 vs. 2.6 ± 0.24 mV) and coactivation (0.17 ± 0.02 vs. 0.20 ± 0.02 mV) were also not different. Similarly, the ratio of force to EMG during submaximal UL and BL contractions was not different. Analysis of force production by each leg in UL and BL conditions showed no differences in force, rate of force generation, EMG, motor unit firing rates, and coactivation. Finally, assessment of quadriceps activity with the twitch interpolation technique indicated no differences in the degree of voluntary muscle activation (UL: 93.6 ± 2.51 Hz, BL: 90.1 ± 2.43 Hz). These results provide no evidence of a significant limitation in neuromuscular control between BL and UL isometric contractions of the knee extensor muscles in young male subjects.

Blood flow response of human calf muscles to static contractions at various percentages of MVC

1981 ◽  
Vol 51 (4) ◽  
pp. 929-933 ◽  
Author(s):  
D. Richardson
Keyword(s):  
Blood Flow ◽  
Muscle Blood Flow ◽  
Plantar Flexion ◽  
Muscle Contractions ◽  
Calf Muscle ◽  
Flow Response ◽  
Steady State Levels ◽  
Age Range ◽  
Static Contractions ◽  
Male Subjects

Six male subjects within the age range of 20–35 yr consented to perform static calf muscle contractions at 7.5, 15, and 30% of their maximum voluntary contractile strength (MVC) for a period of 2 min each. Isometric contractions were performed in a sitting position by pressing the knee against a solid support plate via plantar flexion. Calf muscle blood flow (BF) was measured periodically before, during, and after each contraction by a Whitney gauge. Average resting BF was 3.9 ml . min-1 . 100 ml-1 of calf volume. During the 7.5, 15, and 30% MVC contractions, BF increased to steady-state levels of 7.2, 7.9, and 5.3 ml . min-1 . 100 ml-1, respectively. The values for 7.5 and 15% MVC were significantly higher than resting BF (P less than or equal to 0.05). The postcontraction hyperemia, measured as the area under the postcontraction BF curve, averaged 4.4, 10.1, and 23.2 ml/100 ml, respectively, for the 7.5, 15, and 30% MVC efforts. Comparison of these values with corresponding hyperemic volumes during contraction showed that the portions of the total BF response that occurred in the postcontraction periods were 41, 57, and 88%, respectively, for the 7.5, 15, and 30% efforts. These results demonstrate that during static calf muscle contractions BF increases by only a modest amount, and at even small forces of contraction a sizable portion of the total flow response occurs in the postcontraction period.

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