The effect of an inverted body position on lower limb muscle force and activation

2009 ◽  
Vol 34 (4) ◽  
pp. 673-680 ◽  
Author(s):  
Natasha Paddock ◽  
David Behm
Keyword(s):  
Heart Rate ◽  
Body Position ◽  
Vastus Lateralis ◽  
Voluntary Contraction ◽  
Upright Position ◽  
The Body ◽  
Contractile Properties ◽  
Emg Activity ◽  
Nervous Stimulation ◽  
Inverted Position

Complete inversion of the body in a seated position may occur in exceptional circumstances such as in overturned vehicles and during military maneuvers, with direct consequences on health and fatalities. However, the physiological responses to this condition have not been published previously. The purpose of this study was to compare neuromuscular responses to upright and inverted seated positions. Sixteen subjects performed maximal voluntary contraction (MVC) and submaximal voluntary contraction knee extensions (25%, 50%, and 75% of MVC) under upright and inverted seated positions. Force, quadriceps activation as measured by the interpolated twitch technique, electromyographic (EMG) activity of the vastus lateralis, and semitendenosis and evoked contractile properties of the quadriceps were measured. Results demonstrated that MVC force (p = 0.01, ↓6.1%) and vastus lateralis EMG (p = 0.009, ↓29.6%) decreased in the inverted compared with the upright position. Instantaneous strength in the inverted position was 19.3% lower than in the upright position (p = 0.005). Heart rate and diastolic and systolic blood pressures were 12.4%, 9.2%, and 10.7% lower (p < 0.0001), respectively, in the inverted position. In conclusion, a seated inverted position impaired MVC force and EMG activity, which could not be attributed to evoked contractile properties. The changes in heart rate and blood pressure may suggest inversion-induced alterations to the sympathetic nervous stimulation.

scholarly journals Electrical Stimulation Frequency and Skeletal Muscle Characteristics: Effects on Force and Fatigue

2017 ◽  
Vol 27 (4) ◽  
Author(s):  
Maria Vromans ◽  
Pouran Faghri
Keyword(s):  
Electrical Stimulation ◽  
Vastus Lateralis ◽  
Voluntary Contraction ◽  
Current Intensity ◽  
Muscle Size ◽  
Emg Activity ◽  
Abductor Pollicis Brevis ◽  
Fiber Composition ◽  
Initial Drop ◽  
Initial Force

This investigation aimed to determine the force and muscle surface electromyography (EMG) responses to different frequencies of electrical stimulation (ES) in two groups of muscles with different size and fiber composition (fast- and slow-twitch fiber proportions) during a fatigue-inducing protocol. Progression towards fatigue was evaluated in the abductor pollicis brevis (APB) and vastus lateralis (VL) when activated by ES at three frequencies (10, 35, and 50Hz). Ten healthy adults (mean age: 23.2 ± 3.0 years) were recruited; participants signed an IRB approved consent form prior to participation. Protocols were developed to 1) identify initial ES current intensity required to generate the 25% maximal voluntary contraction (MVC) at each ES frequency and 2) evaluate changes in force and EMG activity during ES-induced contraction at each frequency while progressing towards fatigue. For both muscles, stimulation at 10Hz required higher current intensity of ES to generate the initial force. There was a significant decline in force in response to ES-induced fatigue for all frequencies and for both muscles (p<0.05). However, the EMG response was not consistent between muscles. During the progression towards fatigue, the APB displayed an initial drop in force followed by an increase in EMG activity and the VL displayed a decrease in EMG activity for all frequencies. Overall, it appeared that there were some significant interactions between muscle size and fiber composition during progression towards fatigue for different ES frequencies. It could be postulated that muscle characteristics (size and fiber composition) should be considered when evaluating progression towards fatigue as EMG and force responses are not consistent between muscles.

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).

Body Position Influences Cardiovascular Disgust Reactivity

2015 ◽  
Vol 29 (2) ◽  
pp. 73-79 ◽  
Author(s):  
Anne Schienle ◽  
Sonja Übel ◽  
Andreas Rössler ◽  
Andreas Schwerdtfeger ◽  
Helmut Karl Lackner
Keyword(s):  
Blood Pressure ◽  
Heart Rate ◽  
Body Position ◽  
Vasovagal Syncope ◽  
Upright Position ◽  
Compensatory Mechanism ◽  
Tilt Table ◽  
Increased Risk ◽  
Disgust Proneness

It has been suggested that elevated trait disgust constitutes a vulnerability factor for fainting episodes. We tested the hypothesis that disgust-prone individuals are susceptible to vasovagal syncope by means of a tilt table experiment, during which 30 women were presented with disgusting pictures in a supine and a 70° upright position. The results showed that relative to disgust elicitation in the supine position, tilting reduced diastolic blood pressure during disgust elicitation, which could indicate increased risk for presyncope. Moreover, self-reported disgust proneness was positively correlated with heart rate during disgust induction in the tilted position. This association may point to a compensatory mechanism that aims at stabilizing mean arterial pressure. Disgust-prone individuals possibly utilized this mechanism more extensively to prevent fainting. Future investigations with a longer duration should follow up on this finding and compare the onset of presyncope between high and low disgust-prone individuals.

scholarly journals Physiological Changes in Cardiovascular System during Normal Pregnancy: A Review

2018 ◽  
Vol 03 (02/03) ◽  
pp. 062-067
Author(s):  
Madhuri Taranikanti
Keyword(s):  
Heart Rate ◽  
Cardiac Output ◽  
Cardiac Disease ◽  
Biological Process ◽  
Body Position ◽  
Normal Pregnancy ◽  
Specific Pattern ◽  
The Body ◽  
Physiological Changes ◽  
Complex Biological Process

AbstractPregnancy is a complex biological process associated with changes in physiologic functions of the body. Dramatic changes take place in the cardiovascular physiology leading to gradual adaptation of these changes by the body of the pregnant woman. Cardiac output increases during pregnancy to 30 to 50% above the prepregnant levels. The increase in cardiac output occurs due to increase in stroke volume initially during gestation and later by increase in heart rate. These changes in cardiac output are attributed to either neurohumoral factors such as estrogen and progesterone or placental factors. Maternal body position affects cardiac output with highest in kneel-chest and left lateral positions. Along with these changes, variations in heart rate, blood pressure, and blood volume are observed following a specific pattern of change during pregnancy. Hence, it is necessary to understand the cardiovascular changes during pregnancy to interpret, predict, and diagnose any cardiac disease efficiently.

Behavior of coactive muscles during fatigue

1993 ◽  
Vol 74 (1) ◽  
pp. 170-175 ◽  
Author(s):  
J. A. Psek ◽  
E. Cafarelli
Keyword(s):  
Time Course ◽  
Vastus Lateralis ◽  
Biceps Femoris ◽  
Close Correlation ◽  
Voluntary Contraction ◽  
Knee Extensors ◽  
Emg Activity ◽  
Short Period ◽  
Force Time ◽  
Knee Flexors

Coactivation is antagonist muscle activity that occurs during voluntary contraction. Recently, we showed that the extent of coactivity in the knee flexors decreases after a short period of resistance training of the knee extensors (8). The purpose of the present experiment was to study the time course of coactivation in the knee flexors during fatigue of the knee extensors. Ten male subjects performed repeated submaximal static leg extensions in a low-intensity long-duration and a high-intensity short-duration fatigue protocol until they could no longer produce the required force [time limit of endurance (Tlim)]. Maximal voluntary contraction (MVC), submaximal force, and surface electromyographic (EMG) activity were measured periodically. Vastus lateralis EMG increased progressively during fatigue of the extensor muscles (P < 0.05), resulting in a 38% change from control at Tlim. Biceps femoris EMG, which was our measure of coactivation, also increased by approximately 60% at Tlim in each protocol (P < 0.05). These observations lead us to conclude that a small but significant force loss during repeated static contractions to Tlim is due to an increase in antagonist activity. Moreover, the close correlation between the antagonist and agonist EMG supports the notion of a "common drive" to both motoneuron pools (10).

scholarly journals Acute effect of aerobic and resistance exercises on cardiovascular and neuromuscular responses in normotensive

2020 ◽  
pp. 1-6
Author(s):  
Roberto José Ruiz ◽  
Paulo Fernandes Pires ◽  
Elisa Bizetti Pelai ◽  
Ester Moreira de Castro ◽  
Fabiana Foltran Mescollotto ◽  
...  
Keyword(s):  
Heart Rate ◽  
Muscle Strength ◽  
Aerobic Exercise ◽  
Vastus Lateralis ◽  
Recovery Period ◽  
Acute Effect ◽  
Exercise Session ◽  
Emg Activity ◽  
Myoelectric Activity ◽  
Literature Report

Introduction: the literature report the effect of different types of exercise (aerobic and resisted) on cardiovascular and neuromuscular behavior after exercise. Objective: the objective of this study was to verify the acute effect after a resisted or aerobic exercise session on arterial pressure (BP), heart rate (HR), muscular strength and electromyography (EMG) activity of the rectus femoris (RF), vastus lateralis (VL) and vastus medialis (MV) in normotensive individuals. Method: the study included eight men (27.3 ± 3.1 years, 76.4 ± 9.7 kg, 1.80 ± 0.10 m, 24.3 ± 1.6 kg/m2 ), physically active individuals who randomly performed an aerobic exercise session (treadmill, 30 min, 60-70% of the reserve heart rate), or a resisted exercise session (nine exercises, three sets, 70% 1RM, 8 -12 repetitions). The BP, HR, EMG and muscle strength, were analyzed at rest before exercise and for 60 min after exercise. Results: as a result, systolic BP after the exercises (aerobic and resisted) remained lower than the pre-exercise rest values, with 30, 45 and 60 min (p<0.05) of recovery. On the other hand, the diastolic BP was lower after resistive exercise in all periods of recovery (p <0.01) in relation to pre-exercise. HR values remained elevated after aerobic and resisted exercise, in all recovery periods (p <0.05). Muscle strength and electromyography activity did not show significant differences after exercise. Conclusion: independently of the exercise type, occurs post-exercise hypotension (PEH), increase the HR during the recovery period and reestablishment of muscle strength and myoelectric activity of muscles compared to pre-exercise.

Abdominal muscle activity during speech production

1988 ◽  
Vol 65 (6) ◽  
pp. 2656-2664 ◽  
Author(s):  
J. D. Hoit ◽  
B. L. Plassman ◽  
R. W. Lansing ◽  
T. J. Hixon
Keyword(s):  
Speech Production ◽  
Supine Position ◽  
Muscle Activity ◽  
Neural Control ◽  
Current Knowledge ◽  
Body Position ◽  
Abdominal Muscle ◽  
Upright Position ◽  
Emg Activity ◽  
Tidal Breathing

Abdominal muscle activity was investigated during resting tidal breathing and speech production in upright and supine body positions in five male and five female young adult subjects. Results showed that patterns of abdominal electromyographic (EMG) activity were highly dependent on body position. Data for resting tidal breathing resembled those of previous investigations and revealed one sex-related finding. Data for speech production indicated that the lateral region of the abdomen was highly active in the upright position and occasionally active in the supine position. In the upright position, lateral EMG levels during speech production were characterized by generally higher levels in the lower than upper lateral sites and were almost always higher than during resting tidal breathing. In the supine position, EMG levels during speech production occasionally exceeded those associated with resting tidal breathing but were substantially lower than those associated with upright speech production. Abdominal EMG activity was most prevalent during loud speech production and during speech produced at low lung volumes. Findings are discussed in relation to current knowledge of respiratory mechanics and neural control.

scholarly journals Co-contraction training: myoelectric activity and recruitment strategies in an unorthodox resistance training technique.

2021 ◽  
Author(s):  
Nilson Ribeiro dos Santos Silva ◽  
Matheus Pacheco ◽  
Rafael Akira Fujita ◽  
Marina Mello Villalba ◽  
MATHEUS MACHADO GOMES
Keyword(s):  
Vastus Lateralis ◽  
Rectus Femoris ◽  
Biceps Femoris ◽  
Voluntary Contraction ◽  
Lower Limbs ◽  
Emg Activity ◽  
Myoelectric Activity ◽  
Muscle Recruitment ◽  
Recruitment Pattern ◽  
Recruitment Patterns

Objective To elucidate the muscle recruitment patterns and interindividual variability during co-contraction training sessions for lower limbs. Methods Ten active male young adults underwent two days of tests, in which they performed, for each leg, a maximal isometric voluntary contraction protocol followed by a co-contraction training set. We acquired myoelectric (EMG) activity from the sartorius, biceps femoris long and short heads, semitendinosus, semimembranosus, rectus femoris, vastus lateralis and vastus medialis and tensor facia latae during both protocols. We used iterative HLM analyses and bootstrap ANOVAs to explain within and between participant variances. Results On average, participants started recruiting 36% of their maximum EMG amplitude, showing decays of 0.41% per repetition and increasing 7.45% from day 1 to day 2. Participants who started with higher recruitment showed greater decays over repetitions and vice-versa. The training stimulated similarly the ratio of participants’ flexors and extensors. However, participants demonstrated different average muscle recruitment patterns with some individuals modifying, largely, their recruitment over repetitions/days. Between and within-variability in recruitment pattern was maintained throughout repetitions and days. We found no consistent similarity in terms of pairs of participants as to find common types of recruitment. Conclusion Co-contraction training seems to be effective to recruit thigh muscles of both legs along an entire set of repetitions and days. Despite the accounted variations in intramuscular recruitment, co-contraction training evokes similar muscular in flexor’s and extensor’s recruitment among participants.

The influence of osteopathic correction on the rate of various rhythms of the body

2019 ◽  
pp. 64-71 ◽  
Author(s):  
A. E. Chernikova ◽  
Yu. P. Potekhina
Keyword(s):  
Heart Rate ◽  
Respiratory Rate ◽  
Age Groups ◽  
Biomechanical Properties ◽  
Dispersion Analysis ◽  
The Body ◽  
Body Tissues ◽  
Age Related ◽  
Significant Difference ◽  
Before And After

Introduction. An osteopathic examination determines the rate, the amplitude and the strength of the main rhythms (cardiac, respiratory and cranial). However, there are relatively few studies in the available literature dedicated to the influence of osteopathic correction (OC) on the characteristics of these rhythms.Goal of research — to study the influence of OC on the rate characteristics of various rhythms of the human body.Materials and methods. 88 adult osteopathic patients aged from 18 to 81 years were examined, among them 30 men and 58 women. All patients received general osteopathic examination. The rate of the cranial rhythm (RCR), respiratory rate (RR) heart rate (HR), the mobility of the nervous processes (MNP) and the connective tissue mobility (CTM) were assessed before and after the OC session.Results. Since age varied greatly in the examined group, a correlation analysis of age-related changes of the assessed rhythms was carried out. Only the CTM correlated with age (r=–0,28; p<0,05) in a statistically significant way. The rank dispersion analysis of Kruskal–Wallis also showed statistically significant difference in this indicator in different age groups (p=0,043). With the increase of years, the CTM decreases gradually. After the OC, the CTM, increased in a statistically significant way (p<0,0001). The RCR varied from 5 to 12 cycles/min in the examined group, which corresponded to the norm. After the OC, the RCR has increased in a statistically significant way (p<0,0001), the MNP has also increased (p<0,0001). The initial heart rate in the subjects varied from 56 to 94 beats/min, and in 15 % it exceeded the norm. After the OC the heart rate corresponded to the norm in all patients. The heart rate and the respiratory rate significantly decreased after the OC (р<0,0001).Conclusion. The described biorhythm changes after the OC session may be indicative of the improvement of the nervous regulation, of the normalization of the autonomic balance, of the improvement of the biomechanical properties of body tissues and of the increase of their mobility. The assessed parameters can be measured quickly without any additional equipment and can be used in order to study the results of the OC.

Ideal body position for epinephrine autoinjector administration

2020 ◽  
Author(s):  
Qing Wang ◽  
Luke Pittman ◽  
Andrew Healey ◽  
James Chang ◽  
T. Ted Song
Keyword(s):  
Body Position ◽  
Vastus Lateralis ◽  
The United States ◽  
Thigh Muscle ◽  
First Line ◽  
Medical Treatment Facility ◽  
First Line Therapy ◽  
Epinephrine Autoinjector ◽  
Ideal Body ◽  
The Ideal

Background: Epinephrine is the first-line therapy for patients with anaphylaxis, and intramuscular (IM) delivery is shownto be superior to subcutaneous (SC) delivery. There currently is no consensus on the ideal body position for epinephrine autoinjector (EAI) administration.Objective: We designed this study to investigate whether SC tissue depth (SCTD) is affected by body position (e.g., standing, sitting, supine), which can potentially impact delivery of EAI into the IM space.Methods: Volunteer adults (ages >/= 18 years) from a military medical treatment facility in the United States were recruitedto participate in this study. SCTD of the vastus lateralis was measured via ultrasound at standing, sitting, and supine bodypositions. Subjects’ age, sex, and body mass index (BMI) were collected. Statistical analysis was performed to compare averageSCTD between body positions, sex, and BMI.Results: An analysis of variance of 51 participants (33 men and 18 women) did not reveal statistically significant differencein SCTD among standing, sitting, and supine body positions. It did show a significantly greater SCTD in women than in men (2.72 +/- 1.36 cm versus 1.10 +/- 0.38 cm; p < 0.001). There was no significant association observed between BMI and SCTD in this study.Conclusion: Body position did not seem to significantly change the distance between skin and thigh muscle in adults. Thiswould suggest that there might not be an ideal body position for EAI administration. Therefore, in case of anaphylaxis, promptadministration of epinephrine is recommended at any position.

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