Splenic constriction during isometric handgrip exercise in humans

2008 ◽  
Vol 33 (5) ◽  
pp. 990-996 ◽  
Author(s):  
Maria F. Frances ◽  
Zeljko Dujic ◽  
J. Kevin Shoemaker
Keyword(s):  
Lower Body Negative Pressure ◽  
Maximum Voluntary Contraction ◽  
Voluntary Contraction ◽  
Moderate Intensity ◽  
Isometric Handgrip ◽  
Human Spleen ◽  
Splenic Volume ◽  
Isometric Handgrip Exercise ◽  
Valsalva's Manoeuvre ◽  
Prolonged Apnea

During the first minute of a moderate-intensity isometric handgrip (HG) exercise, there is an increase in stroke volume and cardiac output that occurs without any change in systemic vascular conductance. Although the mechanism of increased venous return is not yet known, current focus has been placed on the constriction of visceral organs. The human spleen represents a compliant organ with high perfusion that constricts during the rather severe stresses of maximal exercise, a diving reflex, or prolonged apnea. This study tested the hypothesis that spleen constriction occurs during isometric HG exercise. Eight participants performed a 1 min isometric HG test at 40% maximum voluntary contraction. Splenic length and width were measured (with ultrasound imaging) after 1 min of exercise, and volume was calculated. To investigate the reflex specificity of this response, spleen dimensions were also measured during 4 min of lower-body negative pressure (LBNP; –20 mm Hg). To test the additional impact of altered breathing and intra-abdominal pressures during the HG, measures were also taken during Valsalva’s manoeuvre (VM) at 30 mm Hg. Compared with baseline, both length and width of the spleen were reduced by 0.20 to 0.55 cm (or 4.44%–6.09%; p < 0.05) during each test. This resulted in relative reductions in splenic volume of 13 ± 1% (HG), 9% ± 7% (LBNP) and 18% ± 7% (VM) (p < 0.05; all mean ± SD). It was concluded that the spleen can constrict during the first minute of isometric HG exercise.

Cutaneous vascular responses to isometric handgrip exercise

1989 ◽  
Vol 66 (4) ◽  
pp. 1586-1592 ◽  
Author(s):  
W. F. Taylor ◽  
J. M. Johnson ◽  
W. A. Kosiba ◽  
C. M. Kwan
Keyword(s):  
Maximum Voluntary Contraction ◽  
Voluntary Contraction ◽  
Dynamic Exercise ◽  
Laser Doppler ◽  
Handgrip Exercise ◽  
Isometric Handgrip ◽  
Local Skin ◽  
Vascular Responses ◽  
Arterial Blood ◽  
Isometric Handgrip Exercise

Cutaneous vascular responses to dynamic exercise have been well characterized, but it is not known whether that response pattern applies to isometric handgrip exercise. We examined cutaneous vascular responses to isometric handgrip and dynamic leg exercise in five supine men. Skin blood flow was measured by laser-Doppler velocimetry and expressed as laser-Doppler flow (LDF). Arterial blood pressure was measured noninvasively once each minute. Cutaneous vascular conductance (CVC) was calculated as LDF/mean arterial pressure. LDF and CVC responses were measured at the forearm and chest during two 3-min periods of isometric handgrip at 30% of maximum voluntary contraction and expressed as percent changes from the preexercise levels. The skin was normothermic (32 degrees C) for the first period of handgrip and was locally warmed to 39 degrees C for the second handgrip. Finally, responses were observed during 5 min of dynamic two-leg bicycle exercise (150–175 W) at a local skin temperature of 39 degrees C. Arm LDF increased 24.5 +/- 18.9% during isometric handgrip in normothermia and 64.8 +/- 14.1% during isometric handgrip at 39 degrees C (P less than 0.05). Arm CVC did not significantly change at 32 degrees C but significantly increased 18.1 +/- 6.5% during isometric handgrip at 39 degrees C (P less than 0.05). Arm LDF decreased 12.2 +/- 7.9% during dynamic exercise at 39 degrees C, whereas arm CVC fell by 35.3 +/- 4.6% (in each case P less than 0.05). Chest LDF and CVC showed similar responses.(ABSTRACT TRUNCATED AT 250 WORDS)

Cardiopulmonary baroreflexes do not modulate exercise-induced sympathoexcitation

1988 ◽  
Vol 64 (5) ◽  
pp. 2197-2203 ◽  
Author(s):  
D. R. Seals
Keyword(s):  
Lower Body Negative Pressure ◽  
Voluntary Contraction ◽  
Voluntary Exercise ◽  
Sympathetic Outflow ◽  
Isometric Handgrip ◽  
General Hypothesis ◽  
Isometric Handgrip Exercise ◽  
Exercise Induced ◽  
The Right ◽  
Exercise In Humans

The purpose of this study was to test the general hypothesis that sympathoinhibitory cardiopulmonary baroreflexes modulate sympathetic outflow during voluntary exercise in humans. Direct (microneurographic) measurements of postganglionic sympathetic nerve activity to noncontracting muscle (MSNA) were made from the right peroneal nerve in the leg, and arterial pressure (AP) and heart rate (HR) were recorded in 10 healthy subjects before (control) and for 2.5 min during each of five interventions: 1) lower-body negative pressure at -10 mmHg (LBNP) alone, 2 and 3) isometric handgrip exercise at 15 and 30% of maximal voluntary contraction (MVC) alone, and 4 and 5) handgrip at 15 and 30% MVC performed during LBNP. During LBNP alone, which should have reduced cardiopulmonary baroreflex sympathoinhibition, AP and HR did not change from control, but MSNA increased 93 +/- 24% (P less than 0.05). Handgrip elicited contraction intensity-dependent increases in AP and HR (P less than 0.05), but MSNA increased above control only at the 30% MVC level (165 +/- 30%, P less than 0.05). The HR, AP, and MSNA responses to either level of handgrip performed during LBNP were not different from the algebraic sums of the corresponding responses to handgrip and LBNP performed separately (P greater than 0.05). Since there was no facilitation of the MSNA response to handgrip when performed during LBNP compared with algebraic sums of the separate responses, our results do not support the hypothesis that cardiopulmonary baroreflexes modulate (inhibit) sympathetic outflow during exercise in humans.

scholarly journals Long-Term Microgravity Effects on Isometric Handgrip and Precision Pinch Force with Visual and Proprioceptive Feedback

2018 ◽  
Vol 2018 ◽  
pp. 1-11
Author(s):  
Ilario Puglia ◽  
Michele Balsamo ◽  
Marco Vukich ◽  
Valfredo Zolesi
Keyword(s):  
Maximum Voluntary Contraction ◽  
Space Station ◽  
Voluntary Contraction ◽  
Force Output ◽  
Isometric Handgrip ◽  
Short Term ◽  
Space Flights ◽  
Pinch Force ◽  
Long Duration

The study and analysis of human physiology during short- and long-duration space flights are the most valuable approach in order to evaluate the effect of microgravity on the human body and to develop possible countermeasures in prevision of future exploratory missions and Mars expeditions. Hand performances such as force output and manipulation capacity are fundamental for astronauts’ intra- and extravehicular activities. Previous studies on upper limb conducted on astronauts during short-term missions (10 days) indicated a temporary partial reduction in the handgrip maximum voluntary contraction (MVC) followed by a prompt recovery and adaptation to weightlessness during the last days of the mission. In the present study, we report on the “Crew’s Health: Investigation on Reduced Operability” (CHIRO) protocol, developed for handgrip and pinch force investigations, performed during the six months increment 7 and increment 8 (2003-2004) onboard International Space Station (ISS). We found that handgrip and pinch force performance are reduced during long-term increments in space and are not followed by adaptation during the mission, as conversely reported during short-term increment experiments. The application of protocols developed in space will be eligible to astronauts during long-term space missions and to patients affected by muscle atrophy diseases or nervous system injury on Earth.

Effect of isometric handgrip exercise on intraocular pressure among healthy adult males

2020 ◽  
pp. 1-6
Author(s):  
S. Ezhilnila ◽  
S. Brinda ◽  
A. Meena ◽  
P.J. Samuel
Keyword(s):  
Intraocular Pressure ◽  
Healthy Adult ◽  
Lifestyle Modification ◽  
Maximum Voluntary Contraction ◽  
South Indian Population ◽  
Adult Males ◽  
Handgrip Exercise ◽  
Isometric Handgrip ◽  
South Indian ◽  
Isometric Handgrip Exercise

Glaucoma is the main cause for irreversible blindness in India. The main determinant of glaucoma is raised intraocular pressure (IOP) which is influenced by many factors. One of the main factors is physical exercise. Objective of this study is to exhibit the effect of isometric handgrip exercise using Smedley’s handgrip dynamometer on IOP among young adult males in the south Indian population. In this quasi experimental study, 150 young healthy adult male subjects with ages between 15 to 40 years were selected on the basis of fulfilling our inclusion and exclusion criteria with the help of a questionnaire. Baseline IOP and maximum voluntary contraction (MVC) of the subjects were measured using non-contact tonometer and Smedley’s Handgrip Dynamometer, respectively. The subjects were instructed to hold the handgrip dynamometer with 20% of MVC in sustained manner for minimum 2 min or until fatigue sets in. IOP were measured on both eyes immediately and 15 min following exercise and IOP variation was analysed using paired t-test. A small but significant decrease in IOP was noted immediately as well as 15 min following exercise. Average fall in right eye was 1.75 mm Hg immediately and 2.14 mm Hg 15 min following exercise (P<0.01). The average fall in the left eye was 1.62 mm Hg immediately and 1.91 mm Hg after 15 min (P<0.01). Isometric handgrip exercise of the single upper limb showed significant reduction of IOP on both eyes following exercise and the decrease was much higher 15 min after exercise. This result can be extrapolated and clinically applied for glaucoma prevention and supplemented as lifestyle modification during glaucoma treatment.

scholarly journals Muscle metaboreceptors modulate postexercise sweating, but not cutaneous blood flow, independent of baroreceptor loading status

2015 ◽  
Vol 309 (11) ◽  
pp. R1415-R1424 ◽  
Author(s):  
Gabrielle Paull ◽  
Sheila Dervis ◽  
Ryan McGinn ◽  
Baies Haqani ◽  
Andreas D. Flouris ◽  
...  
Keyword(s):  
Sweat Rate ◽  
Pressure Control ◽  
Voluntary Contraction ◽  
Treadmill Running ◽  
Maximal Heart Rate ◽  
Isometric Handgrip ◽  
Young Males ◽  
Isometric Handgrip Exercise ◽  
Postexercise Recovery ◽  
Cutaneous Vascular Conductance

We examined whether sustained changes in baroreceptor loading status during prolonged postexercise recovery can alter the metaboreceptors' influence on heat loss. Thirteen young males performed a 1-min isometric handgrip exercise (IHG) at 60% maximal voluntary contraction followed by 2 min of forearm ischemia (to activate metaboreceptors) before and 15, 30, 45, and 60 min after a 15-min intense treadmill running exercise (>90% maximal heart rate) in the heat (35°C). This was repeated on three separate days with continuous lower body positive (LBPP, +40 mmHg), negative (LBNP, −20 mmHg), or no pressure (Control) from 13- to 65-min postexercise. Sweat rate (ventilated capsule; forearm, chest, upper back) and cutaneous vascular conductance (CVC; forearm, upper back) were measured. Relative to pre-IHG levels, sweating at all sites increased during IHG and remained elevated during ischemia at baseline and similarly at 30, 45, and 60 min postexercise (site average sweat rate increase during ischemia: Control, 0.13 ± 0.02; LBPP, 0.12 ± 0.02; LBNP, 0.15 ± 0.02 mg·min−1·cm−2; all P < 0.01), but not at 15 min (all P > 0.10). LBPP and LBNP did not modulate the pattern of sweating to IHG and ischemia (all P > 0.05). At 15-min postexercise, forearm CVC was reduced from pre-IHG levels during both IHG and ischemia under LBNP only (ischemia: 3.9 ± 0.8% CVCmax; P < 0.02). Therefore, we show metaboreceptors increase postexercise sweating in the middle to late stages of recovery (30–60 min), independent of baroreceptor loading status and similarly between skin sites. In contrast, metaboreflex modulation of forearm but not upper back CVC occurs only in the early stages of recovery (15 min) and is dependent upon baroreceptor unloading.

Individual differences in cardiac and vascular components of the pressor response to isometric handgrip exercise in humans

2014 ◽  
Vol 306 (2) ◽  
pp. H251-H260 ◽  
Author(s):  
Kazuhito Watanabe ◽  
Masashi Ichinose ◽  
Rei Tahara ◽  
Takeshi Nishiyasu
Keyword(s):  
Individual Differences ◽  
Arterial Pressure ◽  
Pressor Response ◽  
Voluntary Contraction ◽  
Handgrip Exercise ◽  
Isometric Handgrip ◽  
Muscle Metaboreflex ◽  
Coefficients Of Variation ◽  
Isometric Handgrip Exercise ◽  
Induced Changes

We tested the hypotheses that, in humans, changes in cardiac output (CO) and total peripheral vascular resistance (TPR) occurring in response to isometric handgrip exercise vary considerably among individuals and that those individual differences are related to differences in muscle metaboreflex and arterial baroreflex function. Thirty-nine healthy subjects performed a 1-min isometric handgrip exercise at 50% of maximal voluntary contraction. This was followed by a 4-min postexercise muscle ischemia (PEMI) period to selectively maintain activation of the muscle metaboreflex. All subjects showed increases in arterial pressure during exercise. Interindividual coefficients of variation (CVs) for the changes in CO and TPR between rest and exercise periods (CO: 95.1% and TPR: 87.8%) were more than twofold greater than CVs for changes in mean arterial pressure (39.7%). There was a negative correlation between CO and TPR responses during exercise ( r = −0.751, P < 0.01), but these CO and TPR responses correlated positively with the corresponding responses during PEMI ( r = 0.568 and 0.512, respectively, P < 0.01). The CO response during exercise did not correlate with PEMI-induced changes in an index of cardiac parasympathetic tone and cardiac baroreflex sensitivity. These findings demonstrate that the changes in CO and TPR that occur in response to isometric handgrip exercise vary considerably among individuals and that the two responses have an inverse relationship. They also suggest that individual differences in components of the pressor response are attributable in part to variations in muscle metaboreflex-mediated cardioaccelerator and vasoconstrictor responses.

scholarly journals Impaired dynamic cerebral autoregulation at rest and during isometric exercise in type 2 diabetes patients

2015 ◽  
Vol 308 (7) ◽  
pp. H681-H687 ◽  
Author(s):  
Lauro C. Vianna ◽  
Shekhar H. Deo ◽  
Areum K. Jensen ◽  
Seth W. Holwerda ◽  
Matthew C. Zimmerman ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Type 2 Diabetes ◽  
High Intensity ◽  
Cerebral Autoregulation ◽  
Maximum Voluntary Contraction ◽  
Voluntary Contraction ◽  
Isometric Handgrip ◽  
Systemic Oxidative Stress ◽  
Dynamic Cerebral Autoregulation

Type 2 diabetes mellitus patients (T2D) have elevated risk of stroke, suggesting that cerebrovascular function is impaired. Herein, we examined dynamic cerebral autoregulation (CA) at rest and during exercise in T2D patients and determined whether underlying systemic oxidative stress is associated with impairments in CA. Middle cerebral artery blood velocity and arterial blood pressure (BP) were measured at rest and during 2-min bouts of low- and high-intensity isometric handgrip performed at 20% and 40% maximum voluntary contraction, respectively, in seven normotensive and eight hypertensive T2D patients and eight healthy controls. Dynamic CA was estimated using the rate of regulation (RoR). Total reactive oxygen species (ROS) and superoxide levels were measured at rest. There were no differences in RoR at rest or during exercise between normotensive and hypertensive T2D patients. However, when compared with controls, T2D patients exhibited lower RoR at rest and during low-intensity handgrip indicating impaired dynamic CA. Moreover, the RoR was further reduced by 29 ± 4% during high-intensity handgrip in T2D patients (0.307 ± 0.012/s rest vs. 0.220 ± 0.014/s high intensity; P < 0.01), although well maintained in controls. T2D patients demonstrated greater baseline total ROS and superoxide compared with controls, both of which were negatively related to RoR during handgrip (e.g., total ROS: r = −0.71, P < 0.05; 40% maximum voluntary contraction). Collectively, these data demonstrate impaired dynamic CA at rest and during isometric handgrip in T2D patients, which may be, in part, related to greater underlying systemic oxidative stress. Additionally, dynamic CA is blunted further with high intensity isometric contractions potentially placing T2D patients at greater risk for cerebral events during such activities.

Baroreflex responsiveness is maintained during isometric exercise in humans

1986 ◽  
Vol 61 (2) ◽  
pp. 797-803 ◽  
Author(s):  
T. J. Ebert
Keyword(s):  
Mean Arterial Pressure ◽  
Arterial Pressure ◽  
Carotid Sinus ◽  
Maximum Voluntary Contraction ◽  
Transmural Pressure ◽  
Handgrip Exercise ◽  
Isometric Handgrip ◽  
Baroreflex Control ◽  
Baroreflex Function ◽  
Isometric Handgrip Exercise

The simultaneous rise in heart rate and arterial pressure during isometric handgrip exercise suggests that arterial baroreflex control may be altered. We applied incremental intensities of neck suction and pressure to nine healthy young men to alter carotid sinus transmural pressure. Carotid stimuli were delivered during 1) supine control, 2) “anticipation” of beginning exercise, and 3) handgrip (20% of maximum voluntary contraction). Anticipation was a quiet period, immediately preceding the beginning of handgrip, when no muscular work was being performed. Compared with control, the R-R interval prolongation and mean arterial pressure decline provoked by carotid stimuli were decreased during the anticipation period. These data suggest that influences from higher central neural locations may alter baroreflex function. Furthermore, we derived stimulus-response curves relating carotid sinus transmural pressure to changes in R-R interval and mean arterial pressure. These curves were shifted during handgrip; however, calculated regression slopes were not changed from control. The data indicate that isometric handgrip exercise has a specific influence on human carotid baroreflex control of arterial pressure and heart period: baroreflex function curves are shifted rightward during handgrip, whereas baroreflex sensitivity is unchanged. Furthermore, central neural influences may be partially involved in these alterations.

scholarly journals Functional sympatholysis is preserved in healthy young Black men during rhythmic handgrip exercise

2020 ◽  
Vol 319 (3) ◽  
pp. R323-R328
Author(s):  
Thales C. Barbosa ◽  
Benjamin E. Young ◽  
Brandi Y. Stephens ◽  
Damsara Nandadeva ◽  
Jasdeep Kaur ◽  
...  
Keyword(s):  
Black Men ◽  
Lower Body Negative Pressure ◽  
White Men ◽  
Voluntary Contraction ◽  
Moderate Intensity ◽  
Handgrip Exercise ◽  
Sympathetic Vasoconstriction ◽  
Functional Sympatholysis ◽  
Forearm Vascular Conductance ◽  
Underlying Mechanisms

Black men have attenuated increases in forearm vascular conductance (FVC) and forearm blood flow (FBF) during moderate- and high-intensity rhythmic handgrip exercise compared with White men, but the underlying mechanisms are unclear. Here, we tested for the first time the hypothesis that functional sympatholysis (i.e., attenuation of sympathetic vasoconstriction in the exercising muscles) is impaired in Black men compared with White men. Thirteen White and 14 Black healthy young men were studied. FBF (duplex Doppler ultrasound) and mean arterial pressure (MAP; Finometer) were measured at rest and during rhythmic handgrip exercise at 30% maximal voluntary contraction. FVC was calculated as FBF/MAP. Sympathetic activation was induced via lower body negative pressure (LBNP) at −20 Torr for 2 min at rest and from the 3rd to the 5th min of handgrip. Sympathetic vasoconstriction was assessed as percent reductions in FVC during LBNP. The groups presented similar resting FVC, FBF, and MAP. During LBNP at rest, reductions in FVC were not different between White (−35 ± 10%) and Black men (−32 ± 14%, P = 0.616), indicating similar reflex-induced sympathetic vasoconstriction. During handgrip exercise, there were minimal reductions in FVC with LBNP in either group (White: −1 ± 7%; Black: +1 ± 8%; P = 0.523), indicating functional sympatholysis in both groups. Thus, contrary to our hypothesis, our findings indicate a preserved functional sympatholysis in healthy young Black men compared with White men, suggesting that this mechanism does not appear to contribute to reduced exercise hyperemia during moderate-intensity rhythmic handgrip in this population.

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