Slowing of carotid-cardiac baroreflex with standing and with isometric and dynamic muscle activity

1996 ◽  
Vol 271 (4) ◽  
pp. H1363-H1369 ◽  
Author(s):  
P. Sundblad ◽  
D. Linnarsson
Keyword(s):  
Muscle Activity ◽  
Sympathetic Activity ◽  
Maximum Voluntary Contraction ◽  
Voluntary Contraction ◽  
The Other ◽  
Sitting Position ◽  
Arm Exercise ◽  
Mean Values ◽  
Leg Exercise ◽  
Male Subjects

We hypothesized that the carotid-cardiac baroreflex becomes slowed in conditions with increased sympathetic activity. Changes in heart rate (HR) and blood pressure in response to 10-s trains of 50-mmHg pulses of neck suction (NS) were studied in six male subjects during supine rest, upright rest, isometric arm exercise at 30% of maximum voluntary contraction, and dynamic leg exercise at 100 W in the sitting position. Estimated mean carotid distending pressure increased by approximately 20 mmHg with 50-mmHg, QRS-triggered, pulsatile NS. Repeated NS sequences were performed in each condition. The amplitude of the bradycardic response was highly variable among the subjects and did not differ significantly between conditions, mean values ranging from 0.3 to 0.6 beats.min-1.mmHg-1. In supine rest, the full bradycardic response appeared within < 1 s, i.e., during or immediately after the R-R interval of the first NS pulse. In the other conditions it took significantly longer, 2-3 s or three to seven R-R intervals, for the full HR responses to develop. Our results support the notion that the carotid-cardiac baroreflex in humans becomes slowed under conditions of concurrent sympathetic stimulation.

Upper extremity muscle activity during household floor vacuuming with upright cleaners

2018 ◽  
Vol 62 (1) ◽  
pp. 1018-1021
Author(s):  
Haerim Bak ◽  
Clive D’Souza ◽  
Gwanseob Shin
Keyword(s):  
Upper Extremity ◽  
Muscle Activity ◽  
Maximum Voluntary Contraction ◽  
Voluntary Contraction ◽  
Activity Levels ◽  
Physical Demands ◽  
Study Results ◽  
Musculoskeletal Problems ◽  
Muscle Groups ◽  
Intensive Work

Physical demands of household carpet vacuuming and associated risks for musculoskeletal problems have received little attention although the level of muscle exertions is often assumed to be similar to that of occupational vacuuming. The aim of this study was to quantitatively assess the level of muscle activities of the upper extremity during carpeted floor vacuuming with household upright vacuum cleaners. Eighteen participants conducted four different carpet vacuuming tasks with two different cleaner models. Electromyography data from seven upper extremity muscles were collected. Median muscle activity ranged from 4.5% to 47.5% of the maximum voluntary contraction capacity for female participants and from 2.7% to 23.6% for male participants. Normalized muscle activity levels were significantly higher in women compared to men across tasks and muscle groups. Study results suggest that home vacuuming with upright vacuum cleaners is physically intensive work, especially for female users who are less physically capable.

Wrist and Shoulder Muscle Activity Changes Across Computer Tasks

2002 ◽  
Vol 46 (13) ◽  
pp. 1129-1132 ◽  
Author(s):  
Jack Dennerlein ◽  
Maria-Helena DiMarino ◽  
Ted Becker ◽  
Peter Johnson
Keyword(s):  
Muscle Activity ◽  
Maximum Voluntary Contraction ◽  
Trapezius Muscle ◽  
Surface Emg ◽  
Voluntary Contraction ◽  
Office Work ◽  
Shoulder Muscle ◽  
Physical Risk Factors ◽  
Computer Workstation ◽  
Muscle Groups

The computer workstation is a ubiquitous tool in the office work environment; however, its use varies across many different tasks from surfing the Internet to typing. The question, therefore, is how does exposure to different physical risk factors for musculoskeletal disorders vary across tasks? Fifteen adults (10 females, 5 males) completed tasks simulating work at a computer workstation. The tasks were typing text, completing an html-based form, editing a document, a graphics task, and finally navigating through a series of web pages. During these tasks the muscle activity of the wrist prime movers and three shoulder muscle groups were recorded using surface EMG. For the wrist, the extensors were the most active ranging on average from 8 to 25 percent of Maximum Voluntary Contraction amplitude, with the greatest activity occurring in the typing task. The wrist activity decreased when the work changed from a keyboard-based activity to predominantly mouse-based activity. For the shoulder, the greatest activity was in the Trapezius muscle. The shoulder muscles were most active when both the mouse and the keyboard were required by the task. in summary, wrist and shoulder muscle activities at a computer workstation depend upon the type of task at hand.

scholarly journals Motor planning perturbation: muscle activation and reaction time

2018 ◽  
Vol 120 (4) ◽  
pp. 2059-2065
Author(s):  
Stefan Delmas ◽  
Agostina Casamento-Moran ◽  
Seoung Hoon Park ◽  
Basma Yacoubi ◽  
Evangelos A. Christou
Keyword(s):  
Reaction Time ◽  
Muscle Activity ◽  
Muscle Activation ◽  
Maximum Voluntary Contraction ◽  
Motor Planning ◽  
Reaction Time Task ◽  
Voluntary Contraction ◽  
Voluntary Activation ◽  
Time Interval ◽  
Voluntary Activity

Reaction time (RT) is the time interval between the appearance of a stimulus and initiation of a motor response. Within RT, two processes occur, selection of motor goals and motor planning. An unresolved question is whether perturbation to the motor planning component of RT slows the response and alters the voluntary activation of muscle. The purpose of this study was to determine how the modulation of muscle activity during an RT response changes with motor plan perturbation. Twenty-four young adults (20.5 ±1.1 yr, 13 women) performed 15 trials of an isometric RT task with ankle dorsiflexion using a sinusoidal anticipatory strategy (10–20% maximum voluntary contraction). We compared the processing part of the RT and modulation of muscle activity from 10 to 60 Hz of the tibialis anterior (primary agonist) when the stimulus appeared at the trough or at the peak of the sinusoidal task. We found that RT ( P = 0.003) was longer when the stimulus occurred at the peak compared with the trough. During the time of the reaction, the electromyography (EMG) power from 10 to 35 Hz was less at the peak than the trough ( P = 0.019), whereas the EMG power from 35 to 60 Hz was similar between the peak and trough ( P = 0.92). These results suggest that perturbation to motor planning lengthens the processing part of RT and alters the voluntary activation of the muscle by decreasing the relative amount of power from 10 to 35 Hz. NEW & NOTEWORTHY We aimed to determine whether perturbation to motor planning would alter the speed and muscle activity of the response. We compared trials when a stimulus appeared at the peak or trough of an oscillatory reaction time task. When the stimulus occurred at the trough, participants responded faster, with greater force, and less EMG power from 10-35 Hz. We provide evidence that motor planning perturbation slows the response and alters the voluntary activity of the muscle.

scholarly journals Pallidotomy Increases Cortical Inhibition in Parkinson's Disease

1997 ◽  
Vol 24 (2) ◽  
pp. 133-136 ◽  
Author(s):  
A. Strafella ◽  
P. Ashby ◽  
A. Lozano ◽  
A.E. Lang
Keyword(s):  
Motor Cortex ◽  
Muscle Activity ◽  
Magnetic Stimulation ◽  
Maximum Voluntary Contraction ◽  
Voluntary Contraction ◽  
Short Latency ◽  
Cortical Inhibition ◽  
First Dorsal Interosseus ◽  
Before And After ◽  
Posteroventral Pallidotomy

ABSTRACT:Background:Pallidotomy helps parkinsonian symptoms. We tested the hypothesis that this might be due to changes in inhibition in the motor cortex.Methods:We examined 15 patients with parkinsonism before and after posteroventral pallidotomy. Magnetic stimuli were delivered over the motor cortex, while subjects maintained a 30% maximum voluntary contraction of the contralateral first dorsal interosseus (FDI).Results:Weak stimuli inhibited voluntary muscle activity, while slightly stronger stimuli caused short latency facilitation from activation of the corticospinal neurons. After pallidotomy magnetic stimulation, at the threshold for the short latency facilitation, resulted in more inhibition than before.Conclusions:Pallidotomy increases cortical inhibition. This may be associated with improved control of movements.

Muscle Strength Assessment from the EMG Frequency Spectrum

1987 ◽  
Vol 31 (3) ◽  
pp. 310-314 ◽  
Author(s):  
Eui S. Jung
Keyword(s):  
Biceps Brachii ◽  
Muscle Tension ◽  
Maximum Voluntary Contraction ◽  
Power Spectra ◽  
Voluntary Contraction ◽  
The Other ◽  
Mean Power ◽  
Mean Power Frequency ◽  
Strength Assessment ◽  
The Right

Assessment of a worker's strength is of great interest when evaluating the worker's ability to safely perform a job. Many previous studies have shown that surface electromyogram EMG amplitudes correlate well with muscle force. The present study furthered this concept by using EMG power spectra to achieve a quantified representation of true strength capability. Two groups of male subjects performed isometric elbow flexions while EMG was obtained from the right belly of biceps brachii. One group exercised their arms regularly while the other not. Six different levels of graded maximum voluntary contraction (%MVC) were selected to examine the relations between muscle tension and the mean power frequency (MPF) resulting from EMG power spectra. Resultant MPF's ranged between 50Hz and 70Hz in agreement with previous research results. Two-way ANOVA showed that, in the trained group, a significant increase in the MPF was found at near maximum contractions, whereas the other group failed to show any difference. Further analysis revealed that this increase in MPF was mainly caused by the power increase in the higher bandwidth (70—100Hz). A significant variation between subjects in both groups was also observed.

scholarly journals The Electrical Activity of the Temporal and Masseter Muscles in Patients with TMD and Unilateral Posterior Crossbite

2015 ◽  
Vol 2015 ◽  
pp. 1-7 ◽  
Author(s):  
Krzysztof Woźniak ◽  
Liliana Szyszka-Sommerfeld ◽  
Damian Lichota
Keyword(s):  
Electrical Activity ◽  
Muscle Activity ◽  
Maximum Voluntary Contraction ◽  
Voluntary Contraction ◽  
Asymmetry Index ◽  
Subjective Symptoms ◽  
Posterior Crossbite ◽  
Rest Position ◽  
Torque Coefficient ◽  
Masseter Muscles

The aim of this study was to assess the influence of unilateral posterior crossbite on the electrical activity of the temporal and masseter muscles in patients with subjective symptoms of temporomandibular dysfunctions (TMD). The sample consisted of 50 patients (22 female and 28 male) aged 18.4 to 26.3 years (mean 20.84, SD 1.14) with subjective symptoms of TMD and unilateral posterior crossbite malocclusion and 100 patients without subjective symptoms of TMD and malocclusion (54 female and 46 male) aged between 18.4 and 28.7 years (mean 21.42, SD 1.06). The anamnestic interviews were conducted according to a three-point anamnestic index of temporomandibular dysfunction (Ai). Electromyographical (EMG) recordings were performed using a DAB-Bluetooth Instrument (Zebris Medical GmbH, Germany). Recordings were carried out in the mandibular rest position and during maximum voluntary contraction (MVC). Analysis of the results of the EMG recordings confirmed the influence of unilateral posterior crossbite on variations in spontaneous muscle activity in the mandibular rest position and maximum voluntary contraction. In addition, there was a significant increase in the Asymmetry Index (As) and Torque Coefficient (Tc), responsible for a laterodeviating effect on the mandible caused by unbalanced right and left masseter and temporal muscles.

scholarly journals The Influence of Customized Mouthguards on the Muscular Activity of the Masticatory Muscles at Maximum Bite and Motor Performance During Static and Dynamic Exercises

2021 ◽  
Vol 7 (1) ◽  
Author(s):  
Johannes Lässing ◽  
Christoph Pökel ◽  
Lennart Lingener ◽  
Roberto Falz ◽  
Stefan Kwast ◽  
...  
Keyword(s):  
Muscle Activity ◽  
Motor Performance ◽  
Force Measurement ◽  
Muscular Activity ◽  
Masticatory Muscles ◽  
Voluntary Contraction ◽  
Bite Force ◽  
Erector Spinae ◽  
Mean Values ◽  
Jump Test

Abstract Background Some studies have suggested that a mouthguard is a performance-enhancing device due to a remote voluntary contraction. The extent to which a mouthguard can induce this phenomenon, e.g., by potentially increasing biting, has not been clarified. This study’s aim was to investigate the muscular activity of the maxillary and peripheral musculature and motor performance during a rest and exercise test. Methods Our study comprised 12 active, male, professional young handball players (age 18.83 ± 0.39 years). Their performance, electromyographic (EMG) muscle activity (Σ), and lateral deviation (Δ) of the masticatory and peripheral musculature were measured during rest in a maximum bite force measurement, one-legged stand, a kettlebell swing exercise and a jump test while wearing a customized mouthguard (CMG) or not wearing one (Co). Results Maximum bite force measurements did not differ significantly in their mean values of muscle activity (Σ) for the masseter and temporalis muscles (Co 647.6 ± 212.8 µV vs. CMG 724.3 ± 257.1 µV p = 0.08) (Co 457.2 ± 135.5 µV vs. CMG 426.6 ± 169.3 µV p = 0.38) with versus without CMG. We found no differences in the mean activation values during a one-legged stand, the kettlebell swing, and jump test (Σ) in any of the muscles tested. Lateral deviations (Δ) wearing a CMG were significantly less in the erector spinae during the kettlebell swing (Co 5.33 ± 3.4 µV vs. CMG 2.53 ± 1.8 µV p = 0.01) and countermovement jump (Co 37.90 ± 30.6 µV vs. CMG 17.83 ± 22.3 µV p = 0.03) compared to the performance without a CMG. Jump height, rotation moment, and balance were unchanged with versus without CMG. Conclusion Our results at rest and during specific motor stress show no differences with or without a CMG. The improved peripheral muscular balance while wearing a CMG indicates improved muscular stabilization.

Force Capacity of Back Extensor Muscles in Healthy Males: Effects of Age and Recovery Time

2014 ◽  
Vol 30 (6) ◽  
pp. 713-721 ◽  
Author(s):  
Eduard Kurz ◽  
Christoph Anders ◽  
Mario Walther ◽  
Philipp Schenk ◽  
Hans-Christoph Scholle
Keyword(s):  
Recovery Time ◽  
Maximum Voluntary Contraction ◽  
Age Groups ◽  
Voluntary Contraction ◽  
Upper Body ◽  
Normative Values ◽  
Mean Values ◽  
The Impact ◽  
Back Extensor ◽  
Healthy Males

To judge a person’s maximum trunk extension performance as either age-appropriate or deconditioned is challenging. The current study aimed at determining age and anthropometrically adjusted maximum voluntary contraction (MVC) of back extensors considering the number and recovery time between trials. Thirty-one younger (20–30 years) and 33 older (50–60 years) healthy males performed five repetitions of maximal isometric trunk extensions in an upright standing position with randomized recovery times ranging between one to five minutes at one minute intervals. Torque values were normalized according to the individual’s upper body mass resulting in upper body torque ratios (UBTR). To evaluate the impact of age, recovery time, and fatigue on UBTR we applied a linear mixed-effects model. Based on surface EMG data muscular fatigue could be excluded for both groups. For all MVC trials, UBTR levels differed significantly between age groups (range of mean values: younger: 2.26–2.28, older: 1.78–1.87, effect size: 1.00) but were independent from recovery time. However, the older males tended to exert higher UBTR values after shorter recovery periods. The study provides normative values of anthropometrically and age-group adjusted maximum back extensor forces. For the investigated groups, only two MVC trials with a recovery time of about one minute seem appropriate.

Psychophysical Measures of Exertion. Are They Muscle Group Dependent?

1995 ◽  
Vol 39 (10) ◽  
pp. 694-698
Author(s):  
Anpin ‘Max» Chin ◽  
Ram R. Bishu ◽  
Susan Hallbeck
Keyword(s):  
Upper Limb ◽  
Perceived Exertion ◽  
Maximum Voluntary Contraction ◽  
Subjective Assessment ◽  
Voluntary Contraction ◽  
Muscle Group ◽  
Muscle Groups ◽  
Male Subjects ◽  
Female Subjects

The purpose of the present study was to evaluate the applicability of the RPE (CR-10) scale for a number of physical exertions which employ only the upper limb with a variety of muscle group sizes and exertion levels. Ten female and ten male subjects performed pinch and pulling tasks in which four different muscle groups were engaged employing the finger, wrist, forearm and the whole arm. MVC (maximum voluntary contraction) exertion levels, RPE (Borg's CR-10 scale) value, and accuracy of the subjective assessment were measured. The results indicate that the accuracy of psychophysical measures are not muscle dependent although force generating capability is dependent on the muscle group involved. Female subjects were found more accurate in their perception of perceived exertion at lower levels of exertion than male subjects. It also appears that the RPE rating can be used to assess a variety of exertion levels accurately for a range of tasks, involving a range of muscle group sizes and location.

scholarly journals Why do arms extract less oxygen than legs during exercise?

2005 ◽  
Vol 289 (5) ◽  
pp. R1448-R1458 ◽  
Author(s):  
J. A. L. Calbet ◽  
H.-C. Holmberg ◽  
H. Rosdahl ◽  
G. van Hall ◽  
M. Jensen-Urstad ◽  
...  
Keyword(s):  
Blood Flow ◽  
Maximal Exercise ◽  
Mean Transit Time ◽  
Flow Distribution ◽  
Arm Exercise ◽  
Mean Values ◽  
Double Poling ◽  
Leg Exercise ◽  
Arm Muscles ◽  
Cross Country

To determine whether conditions for O2 utilization and O2 off-loading from the hemoglobin are different in exercising arms and legs, six cross-country skiers participated in this study. Femoral and subclavian vein blood flow and gases were determined during skiing on a treadmill at ∼76% maximal O2 uptake (V̇o2 max) and at V̇o2 max with different techniques: diagonal stride (combined arm and leg exercise), double poling (predominantly arm exercise), and leg skiing (predominantly leg exercise). The percentage of O2 extraction was always higher for the legs than for the arms. At maximal exercise (diagonal stride), the corresponding mean values were 93 and 85% ( n = 3; P < 0.05). During exercise, mean arm O2 extraction correlated with the Po2 value that causes hemoglobin to be 50% saturated (P50: r = 0.93, P < 0.05), but for a given value of P50, O2 extraction was always higher in the legs than in the arms. Mean capillary muscle O2 conductance of the arm during double poling was 14.5 (SD 2.6) ml·min−1·mmHg−1, and mean capillary Po2 was 47.7 (SD 2.6) mmHg. Corresponding values for the legs during maximal exercise were 48.3 (SD 13.0) ml·min−1·mmHg−1 and 33.8 (SD 2.6) mmHg, respectively. Because conditions for O2 off-loading from the hemoglobin are similar in leg and arm muscles, the observed differences in maximal arm and leg O2 extraction should be attributed to other factors, such as a higher heterogeneity in blood flow distribution, shorter mean transit time, smaller diffusing area, and larger diffusing distance, in arms than in legs.

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