Effect of muscle tension on the cardiovascular responses to lower body negative pressure in man

Smith, Michael L.; Hudson, Donna L.; Raven, Peter B.

doi:10.1249/00005768-198710000-00003

Cited by 38 publications

(24 citation statements)

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“…Therefore it is possible that the protocol used in the present study closely resembled head-up suspension, and this may provide some explanation for the insignificant changes in EMG activity during the orthostatic challenge. The present results do not discount an influence of intentional muscle contractions and muscle tension on HR and AP responses during orthostasis [13]. However, these findings demonstrate that, during 90 m HUT, healthy young and older men have distinct HR and finger AP responses in the absence of significant differences in lower-limb antigravity muscle activity.…”

Section: Discussioncontrasting

confidence: 96%

Cardiovascular regulation during head-up tilt in healthy 20–30-year-old and 70–75-year-old men

et al. 2001

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This study compared the heart rate, finger arterial pressure (AP) and electromyographic (EMG) activity of selected anti-gravity muscles during the initial and prolonged phases of orthostatic stress in healthy young and older men. Beat-by-beat recordings of heart rate, finger systolic pressure, diastolic pressure and mean AP were made during supine rest and 5 min of 90 degrees head-up tilt (HUT) in 18 young (23+/-1 years) and 15 older (73+/-1 years) men. The EMG activity of the soleus, tibialis anterior and vastus medialis muscles was recorded. During the first 30 s following 90 degrees HUT (immediate response), the young men exhibited significant (P<0.05) decreases in finger systolic pressure, diastolic pressure and mean AP, followed by a sustained increase in finger AP during the 5 min following 90 degrees HUT (prolonged response). The immediate and prolonged finger AP and diastolic pressure responses were not significantly different (P>0.05) from the values at supine rest for the older men. The mean root mean square EMG activity of the soleus, tibialis anterior and vastus medialis muscles during 90 degrees HUT was not significantly different (P>0.05) from that at supine rest for either group. These results demonstrate that, when compared with healthy older men, young men show larger reductions in finger AP during the initial phase of orthostatic stress. However, during the prolonged phase of orthostatic stress, older men maintain resting finger AP, whereas young men demonstrate a reflex overshoot in finger AP. Finally, differences in lower-limb anti-gravity muscle activation do not account for the contrasting finger AP responses of healthy young and older men.

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Section: Discussioncontrasting

confidence: 96%

Cardiovascular regulation during head-up tilt in healthy 20–30-year-old and 70–75-year-old men

et al. 2001

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“…They underwent an orientation session to LBNP and, except for the subject who finished both trials, stopped the test due to presyncopal symptoms. They were frequently reminded to relax their lower limbs to avoid the effects of muscle contractions on caudal displacement of blood volume (Smith et al 1987). The trials were held at the same time of the day to avoid the influence of circadian rhythms.…”

Section: Discussionmentioning

confidence: 99%

Reproducibility of the heart rate variability responses to graded lower body negative pressure

Lee

Buchanan

Flatau

et al. 2004

European Journal of Applied Physiology

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The reproducibility of heart rate variability (HRV) measures during graded lower body negative pressure (LBNP) have not been studied in sufficient detail. Active college age men (n=14) underwent an orientation exposure and two trials of graded LBNP to presyncope or -100 mmHg, separated by 1 week. Heart rate, stroke volume (impedance cardiography), blood pressure (Finapres), and forearm blood flow were assessed, as was HRV in both time and frequency domains. The trial-to-trial responses to LBNP common to all subjects (LBNP< or =-60 mmHg and at test termination) showed parallel changes, suggesting similar responses between both trials. Good reproducibility estimates were found for the resting HRV data (lowest: R=0.62 for low frequency/high frequency ratio; highest: R=0.94 for standard deviation of normal R-R intervals). During LBNP, reproducibility estimates varied but were generally similar to that seen at rest. At test termination, they were unacceptably low (R<0.41) for the HRV data assessed in the frequency domain and expressed in absolute units. LBNP tolerance was lower in the first trial [LBNP tolerance index: 404 (21) versus 437 (15) mmHg min(-1); P<0.05] but the intraclass correlation coefficient was high (R=0.87). These data suggest that (1) HRV responses to submaximal LBNP up to -60 mmHg are consistent across trials, (2) the considerable variability seen in the HRV parameters at maximal LBNP can be reduced by expressing these data in either the time domain or using normalized units in the frequency domain, and (3) cardiovascular responses to sub- and maximal LBNP are reproducible. Data are presented as mean (SEM) unless otherwise stated.

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“…In our study Female donors had a statistically significant higher rate of VVR, which supports findings of previous studies [13][14][15] . On the other hand many other authors reported that there is no significant difference between men and women donors for VVR [16][17][18] . We found that 71.2% of donors suffered with VVR were new donor and 28.8% were repeat donor.…”

Section: Discussionmentioning

confidence: 87%

The Incidence of Vaso-vagal Reactions Among Whole Blood Donors During or Immediately After Donation

Rahman

Biswas

Islam

et al. 2011

Bangabandhu Sheikh Mujib Medical Univ J

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Effect of muscle tension on the cardiovascular responses to lower body negative pressure in man

Cited by 38 publications

References 0 publications

Cardiovascular regulation during head-up tilt in healthy 20–30-year-old and 70–75-year-old men

Cardiovascular regulation during head-up tilt in healthy 20–30-year-old and 70–75-year-old men

Reproducibility of the heart rate variability responses to graded lower body negative pressure

The Incidence of Vaso-vagal Reactions Among Whole Blood Donors During or Immediately After Donation

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