Effect of Isometric Hand-Grip Exercise on the Carotid Sinus Baroreceptor Reflex in Man

1978 ◽  
Vol 54 (1) ◽  
pp. 33-37 ◽  
Author(s):  
G. Mancia ◽  
J. Iannos ◽  
G. G. Jamieson ◽  
R. H. Lawrence ◽  
P. R. Sharman ◽  
...  
Keyword(s):  
Maximal Voluntary Contraction ◽  
Carotid Sinus ◽  
Voluntary Contraction ◽  
Baroreceptor Reflex ◽  
Transmural Pressure ◽  
Variable Pressure ◽  
Hand Grip ◽  
The Moment ◽  
Normal Men ◽  
Neck Chamber

1. The changes in R—R heart interval that result from step-increase and step-decrease in carotid sinus transmural pressure induced by a variable-pressure neck chamber were measured in seven normal men. Observations were made at rest, and during isometric hand-grip exercise at 24%, 44% and 64% of maximal voluntary contraction. 2. The response of heart interval to increase in carotid sinus transmural pressure was progressively and markedly diminished according to the strength of hand-grip. This effect was fully developed from the moment of onset of the exertion. 3. The response of heart interval to decrease in carotid sinus transmural pressure was much less consistently affected by hand-grip exercise.

The Variable-Pressure Neck-Chamber Method for Studying the Carotid Baroreflex in Man

1977 ◽  
Vol 53 (2) ◽  
pp. 165-171 ◽  
Author(s):  
J. Ludbrook ◽  
G. Mancia ◽  
A. Ferrari ◽  
A. Zanchetti
Keyword(s):  
Negative Pressure ◽  
Carotid Sinus ◽  
Venous Blood ◽  
Baroreceptor Reflex ◽  
Variable Pressure ◽  
Positive Pressure ◽  
Chamber Method ◽  
Carotid Baroreceptor ◽  
Pressure Changes ◽  
Neck Chamber

1. The variable-pressure neck-chamber method was analysed in ten healthy volunteer subjects to determine its suitability for the study of the carotid baroreceptor reflex in man. 2. Positive and negative pressures applied to the neck (range ± 60 mmHg) were always transmitted linearly to a tissue catheter outside the carotid sinus, but only 86% of positive pressure, and 64% of negative pressure. Tissue pressures were confirmed by simultaneous measurement in the internal jugular vein adjacent to the carotid sinus. 3. Positive and negative pressure changes within the above range did not alter Po2 of internal jugular venous blood, suggesting that cerebral blood flow was unaltered. 4. Positive pressure changes induced reflex pressor responses of similar magnitude at arterial Po2 12·8 and 70·1 kPa (96 and 527 mmHg), suggesting that the carotid chemoreceptors were not involved. 5. It is concluded that the variable-pressure neck chamber is a valid method for selectively studying the carotid baroreceptor reflex in man. However, transmission of external pneumatic pressure to the carotid sinus is imperfect and greater for positive than for negative pressure. This must be recognized to avoid underestimation of gain and distortion of shape of the reflex.

Lack of Effect of Isometric Handgrip Exercise on the Responses of the Carotid Sinus Baroreceptor Reflex in Man

1978 ◽  
Vol 55 (2) ◽  
pp. 189-194 ◽  
Author(s):  
J. Ludbrook ◽  
I. B. Faris ◽  
J. Iannos ◽  
G. G. Jamieson ◽  
W. J. Russell
Keyword(s):  
Blood Pressure ◽  
Heart Rate ◽  
Carotid Sinus ◽  
Maximum Voluntary Contraction ◽  
Isometric Exercise ◽  
Baroreceptor Reflex ◽  
Transmural Pressure ◽  
Variable Pressure ◽  
Isometric Handgrip ◽  
Arterial Blood

1. The change in arterial pressure and heart rate resulting from alteration of carotid sinus transmural pressure by a median −34 mmHg and +33 mmHg by means of a variable-pressure neck chamber was tested in seven male volunteer subjects, at rest and during exertion of 35, 45 and 65% of maximum voluntary handgrip. 2. During 60 s of 35 and 45%, and during 30 s of 65%, of maximal voluntary handgrip there was virtually no alteration of the response of blood pressure to alteration in carotid sinus transmural pressure. 3. The bradycardic response to increase in carotid sinus transmural pressure was reduced at various times after the commencement of handgrip at 45 and 65% of maximum voluntary contraction. 4. It is concluded that a reduction in arterial baroreceptor reflex sensitivity does not play an important role in the initiation of the increase in arterial blood pressure and heart rate caused by isometric exercise. 5. The hypothesis is advanced that some of the cardiovascular changes in exercise may result from elevation of the central ‘set point’ for blood pressure.

The Influence of Intermittent Fatigue Exercise on Early and Late Phases of Relaxation From Maximal Voluntary Contraction

1997 ◽  
Vol 22 (6) ◽  
pp. 573-584 ◽  
Author(s):  
Anna Jaskólska ◽  
Artur Jaskólski
Keyword(s):  
Relaxation Time ◽  
Relaxation Rate ◽  
Maximal Voluntary Contraction ◽  
Early Phase ◽  
Intermittent Exercise ◽  
Young Male ◽  
Voluntary Contraction ◽  
Hand Grip ◽  
Before And After ◽  
Late Relaxation Time

Twenty-two young male subjects were tested to estimate the behavior of the early and late phases of relaxation from a 3-s maximal voluntary contraction (MVC) under the influence of fatigue. Less demanding and more demanding protocols of intermittent hand grip exercise were used to fatigue muscle. Before and after fatigue, the early and late relaxation time, maximal relaxation rate, and half-relaxation time were measured. The results showed that during voluntary movement (a) the early phase of relaxation was independent of the mode of intermittent exercise and did not change significantly after fatigue; (b) the late relaxation time and absolute maximal relaxation rate were slower after both protocols, with the changes more pronounced following the more demanding protocol; and (c) the half-relaxation time and relative maximal relaxation rate were changed only in the more demanding protocol. It is concluded that unlike the relaxation following electrical stimulation of isolated muscle, the early phase of relaxation from voluntary contraction appears to be the most resistant to the type of intermittent fatiguing exercise used in the present study, whereas the late relaxation time was the most sensitive to this type of fatigue. Key words: hand grip exercise, late relaxation time, early relaxation time, half-relaxation time

Factors Influencing the Carotid Baroreceptor Response to Pressure Changes in a Neck Chamber

1976 ◽  
Vol 51 (s3) ◽  
pp. 347s-349s ◽  
Author(s):  
J. Ludbrook ◽  
G. Mancia ◽  
A. Ferrari ◽  
A. Zanchetti
Keyword(s):  
Carotid Sinus ◽  
Pressor Response ◽  
Baroreceptor Reflex ◽  
Chamber Pressure ◽  
Positive Pressure ◽  
Carotid Baroreceptor ◽  
Factors Influencing ◽  
Correct Analysis ◽  
Pressure Changes ◽  
Neck Chamber

1. Transmission of pneumatic pressure from a neck chamber to the region of the carotid sinus is imperfect and asymmetric (86% of positive pressure, 64% of negative pressure). This has to be taken into account in the correct analysis of the carotid baroreceptor reflex. 2. There is no evidence for a reduction in cerebral blood flow nor of carotid chemoreceptor stimulation in response to an increase in neck chamber pressure of about 45 mmHg. Thus it is likely that the pressor response to this manoeuvre is in fact due to reduction in carotid baroreceptor activity.

scholarly journals Repeated contractions alter the geometry of human skeletal muscle

2002 ◽  
Vol 93 (6) ◽  
pp. 2089-2094 ◽  
Author(s):  
Constantinos N. Maganaris ◽  
Vasilios Baltzopoulos ◽  
Anthony J. Sargeant
Keyword(s):  
Skeletal Muscle ◽  
Maximal Voluntary Contraction ◽  
Human Skeletal Muscle ◽  
Voluntary Contraction ◽  
Pennation Angle ◽  
Medial Gastrocnemius ◽  
Myotendinous Junction ◽  
Rest Interval ◽  
In Series ◽  
The Moment

The aim of this study was to investigate the effect of repeated contractions on the geometry of human skeletal muscle. Six men performed two sets ( sets Aand B) of 10 repeated isometric plantarflexion contractions at 80% of the moment generated during plantarflexion maximal voluntary contraction (MVC), with a rest interval of 15 min between sets. By use of ultrasound, the geometry of the medial gastrocnemius (MG) muscle was measured in the contractions of set A and the displacement of the MG tendon origin in the myotendinous junction was measured in the contractions of set B. In the transition from the 1st to the 10th contractions, the fascicular length at 80% of MVC decreased from 34 ± 4 (means ± SD) to 30 ± 3 mm ( P < 0.001), the pennation angle increased from 35 ± 3 to 42 ± 3° ( P < 0.001), the myotendinous junction displacement increased from 5 ± 3 to 10 ± 3 mm ( P < 0.001), and the average fascicular curvature remained constant ( P > 0.05) at ∼4.3 m−1. No changes ( P > 0.05) were found in fascicular length, pennation angle, and myotendinous junction displacement after the fifth contraction. Electrogoniometry showed that the ankle rotated by ∼6.5° during contraction, but no differences ( P > 0.05) were obtained between contractions. The present results show that repeated contractions induce tendon creep, which substantially affects the geometry of the in-series contracting muscles, thus altering their potential for force and joint moment generation.

The Performance of Female Young Adults in Perception of Efforts of Varied Nature and Magnitudes

1993 ◽  
Vol 37 (10) ◽  
pp. 793-797
Author(s):  
Shrawan Kumar ◽  
Maureen Simmonds ◽  
David Lechelt
Keyword(s):  
Young Adults ◽  
Statistical Analysis ◽  
Young Adult ◽  
Maximal Voluntary Contraction ◽  
Voluntary Contraction ◽  
Test Analysis ◽  
Hand Grip ◽  
Adult Females ◽  
Significant Difference ◽  
Entire Experiment

Ten normal young adult females performed maximal and graded exertions of the stoop lift, hand grip, and finger pinch. The levels of graded exertion required were 80%, 60%, 40% and 20% of maximal voluntary contraction (MVC). The sequence of all conditions were fully randomized. Each of the randomized conditions was tried three times in succession. The entire experiment was carried out on four different days at the same time of the day on Monday, Wednesday, Friday of one week and Friday of the next week. The data obtained were subjected to descriptive and statistical analysis with t-test, analysis of variance, and correlation and regression. There were significant differences in the efforts produced in three different activities (p<0.01). The levels of exertion from 20% to 80% were significantly different from each other (p<0.01). However, there were no significant differences between the three trials of any given condition and the exertions produced on four different days. The 80% and 60% of exertions were overestimated and 20% was underestimated compared to the objective values based on MVC (p<0.01). At 40% effort there was no significant difference between the objective level of exertion and subjectively gauged and produced effort. The reliability of perception among the female subjects was similar for finger pinch, hand grip, and stoop lift activities.

Sign in / Sign up

Export Citation Format

Share Document