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1.
Chronic hormone replacement therapy alters thermoregulatory and vasomotor function in postmenopausal women 总被引:2,自引:0,他引:2
Brooks E. M.; Morgan A. L.; Pierzga J. M.; Wladkowski S. L.; O'Gorman J. T.; Derr J. A.; Kenney W. L. 《Journal of applied physiology》1997,83(2):477-484
Brooks, E. M., A. L. Morgan, J. M. Pierzga, S. L. Wladkowski, J. T. O'Gorman, J. A. Derr, and W. L. Kenney. Chronic hormone replacement therapy alters thermoregulatory and vasomotor function in postmenopausal women. J. Appl.Physiol. 83(2): 477-484, 1997.This investigationexamined effects of chronic (2 yr) hormone replacement therapy (HRT),both estrogen replacement therapy (ERT) and estrogen plus progesteronetherapy (E+P), on core temperature and skin blood flow responses ofpostmenopausal women. Twenty-five postmenopausal women [9 not onHRT (NO), 8 on ERT, 8 on E+P] exercised on a cycle ergometer for1 h at an ambient temperature of 36°C. Cutaneous vascularconductance (CVC) was monitored by laser-Doppler flowmetry, and forearmvascular conductance (FVC) was measured by using venous occlusionplethysmography. Iontophoresis of bretylium tosylate was performedbefore exercise to block local vasoconstrictor (VC) activity at oneskin site on the forearm. Rectal temperature (Tre) was ~0.5°C lower forthe ERT group (P < 0.01) comparedwith E+P and NO groups at rest and throughout exercise. FVC: mean body temperature (Tb) and CVC:Tb curves were shifted~0.5°C leftward for the ERT group(P < 0.0001). Baseline CVC wassignificantly higher in the ERT group(P < 0.05), but there was nointeraction between bretylium treatment and groups once exercise wasinitiated. These results suggest that1) chronic ERT likely acts centrally to decrease Tre,2) ERT lowers theTre at which heat-loss effector mechanisms are initiated, primarily by actions on active cutaneous vasodilation, and 3) addition ofexogenous progestins in HRT effectively blocks these effects. 相似文献
2.
D L Kellogg Y Liu K McAllister C Friel P E Pérgola 《Journal of applied physiology》2002,93(4):1215-1221
To test the hypothesis that bradykinin effects cutaneous active vasodilation during hyperthermia, we examined whether the increase in skin blood flow (SkBF) during heat stress was affected by blockade of bradykinin B(2) receptors with the receptor antagonist HOE-140. Two adjacent sites on the forearm were instrumented with intradermal microdialysis probes for local delivery of drugs in eight healthy subjects. HOE-140 was dissolved in Ringer solution (40 microM) and perfused at one site, whereas the second site was perfused with Ringer alone. SkBF was monitored by laser-Doppler flowmetry (LDF) at both sites. Mean arterial pressure (MAP) was monitored from a finger, and cutaneous vascular conductance (CVC) was calculated (CVC = LDF/MAP). Water-perfused suits were used to control body temperature and evoke hyperthermia. After hyperthermia, both microdialysis sites were perfused with 28 mM nitroprusside to effect maximal vasodilation. During hyperthermia, CVC increased at HOE-140 (69 +/- 2% maximal CVC, P < 0.01) and untreated sites (65 +/- 2% maximal CVC, P < 0.01). These responses did not differ between sites (P > 0.05). Because the bradykinin B(2)-receptor antagonist HOE-140 did not alter SkBF responses to heat stress, we conclude that bradykinin does not mediate cutaneous active vasodilation. 相似文献
3.
Effects of caffeine on blood pressure, heart rate, and forearm blood flow during dynamic leg exercise 总被引:3,自引:0,他引:3
Daniels Jason W.; Mole Paul A.; Shaffrath James D.; Stebbins Charles L. 《Journal of applied physiology》1998,85(1):154-159
This study examined the acute effects of caffeine on thecardiovascular system during dynamic leg exercise. Ten trained,caffeine-naive cyclists (7 women and 3 men) were studied at rest andduring bicycle ergometry before and after the ingestion of 6 mg/kgcaffeine or 6 mg/kg fructose (placebo) with 250 ml of water. Afterconsumption of caffeine or placebo, subjects either rested for 100 min(rest protocol) or rested for 45 min followed by 55 min of cycleergometry at 65% of maximal oxygen consumption (exercise protocol).Measurement of mean arterial pressure (MAP), forearm blood flow (FBF),heart rate, skin temperature, and rectal temperature and calculation offorearm vascular conductance (FVC) were made at baseline and at 20-minintervals. Plasma ANG II was measured at baseline and at 60 minpostingestion in the two exercise protocols. Before exercise, caffeineincreased both systolic blood pressure (17%) and MAP (11%) withoutaffecting FBF or FVC. During dynamic exercise, caffeine attenuated theincrease in FBF (53%) and FVC (50%) and accentuated exercise-inducedincreases in ANG II (44%). Systolic blood pressure and MAP were alsohigher during exercise plus caffeine; however, these increases weresecondary to the effects of caffeine on resting bloodpressure. No significant differences were observed inheart rate, skin temperature, or rectal temperature. These findingsindicate that caffeine can alter the cardiovascular response to dynamicexercise in a manner that may modify regional blood flow andconductance. 相似文献
4.
Nagashima Kei; Nose Hiroshi; Takamata Akira; Morimoto Taketoshi 《Journal of applied physiology》1998,84(6):1845-1851
To assessthe impact of continuous negative-pressure breathing (CNPB) on theregulation of skin blood flow, we measured forearm blood flow (FBF) byvenous-occlusion plethysmography and laser-Doppler flow (LDF) at theanterior chest during exercise in a hot environment (ambienttemperature = 30°C, relative humidity = ~30%). Seven malesubjects exercised in the upright position at an intensity of 60% peakoxygen consumption rate for 40 min with and without CNPB after 20 minof exercise. The esophageal temperature(Tes) in both conditionsincreased to 38.1°C by the end of exercise, without any significantdifferences between the two trials. Mean arterial pressure (MAP)increased by ~15 mmHg by 8 min of exercise, without any significantdifference between the two trials before CNPB. However, CNPB reducedMAP by ~10 mmHg after 24 min of exercise (P < 0.05). The increasein FBF and LDF in the control condition leveled off after 18 min ofexercise above a Tes of37.7°C, whereas in the CNPB trial the increase continued, with arise in Tes despite the decreasein MAP. These results suggest that CNPB enhances vasodilation of skinabove a Tes of ~38°C bystretching intrathoracic baroreceptors such as cardiopulmonarybaroreceptors. 相似文献
5.
Kellogg DL Zhao JL Wu Y 《American journal of physiology. Heart and circulatory physiology》2008,295(1):H123-H129
Nitric oxide (NO) participates in locally mediated vasodilation induced by increased local skin temperature (T(loc)) and in sympathetically mediated vasodilation during whole body heat stress. We hypothesized that endothelial NOS (eNOS) participates in the former, but not the latter, response. We tested this hypothesis by examining the effects of the eNOS antagonist N(G)-amino-l-arginine (l-NAA) on skin blood flow (SkBF) responses to increased T(loc) and whole body heat stress. Microdialysis probes were inserted into forearm skin for drug delivery. One microdialysis site was perfused with l-NAA in Ringer solution and a second site with Ringer solution alone. SkBF [laser-Doppler flowmetry (LDF)] and blood pressure [mean arterial pressure (MAP)] were monitored, and cutaneous vascular conductance (CVC) was calculated (CVC = LDF / MAP). In protocol 1, T(loc) was controlled with LDF/local heating units. T(loc) initially was held at 34 degrees C and then increased to 41.5 degrees C. In protocol 2, after a normothermic period, whole body heat stress was induced (water-perfused suits). At the end of both protocols, 58 mM sodium nitroprusside was perfused at both microdialysis sites to cause maximal vasodilation for data normalization. In protocol 1, CVC at 34 degrees C T(loc) did not differ between l-NAA-treated and untreated sites (P > 0.05). Local skin warming to 41.5 degrees C T(loc) increased CVC at both sites. This response was attenuated at l-NAA-treated sites (P < 0.05). In protocol 2, during normothermia, CVC did not differ between l-NAA-treated and untreated sites (P > 0.05). During heat stress, CVC rose to similar levels at l-NAA-treated and untreated sites (P > 0.05). We conclude that eNOS is predominantly responsible for NO generation in skin during responses to increased T(loc), but not during reflex responses to whole body heat stress. 相似文献
6.
D L Kellogg G J Hodges C R Orozco T M Phillips J L Zhao J M Johnson 《Journal of applied physiology》2007,103(3):963-968
To test the hypothesis that cutaneous active vasodilation in heat stress is mediated by a redundant cholinergic cotransmitter system, we examined the effects of atropine on skin blood flow (SkBF) increases during heat stress in persons with (CF) and without cystic fibrosis (non-CF). Vasoactive intestinal peptide (VIP) has been implicated as a mediator of cutaneous vasodilation in heat stress. VIP-containing cutaneous neurons are sparse in CF, yet SkBF increases during heat stress are normal. In CF, augmented ACh release or muscarinic receptor sensitivity could compensate for decreased VIP; if so, active vasodilation would be attenuated by atropine in CF relative to non-CF. Atropine was administered into skin by iontophoresis in seven CF and seven matched non-CF subjects. SkBF was monitored by laser-Doppler flowmetry (LDF) at atropine treated and untreated sites. Blood pressure [mean arterial pressure (MAP)] was monitored (Finapres), and cutaneous vascular conductance was calculated (CVC = LDF/MAP). The protocol began with a normothermic period followed by a 3-min cold stress and 30-45 min of heat stress. Finally, LDF sites were warmed to 42 degrees C to effect maximal vasodilation. CVC was normalized to its site-specific maximum. During heat stress, CVC increased in both CF and non-CF (P < 0.01). CVC increases were attenuated by atropine in both groups (P < 0.01); however, the responses did not differ between groups (P = 0.99). We conclude that in CF there is not greater dependence on redundant cholinergic mechanisms for cutaneous active vasodilation than in non-CF. 相似文献
7.
Acetylcholine (ACh) can effect vasodilation by several mechanisms, including activation of endothelial nitric oxide (NO) synthase and prostaglandin (PG) production. In human skin, exogenous ACh increases both skin blood flow (SkBF) and bioavailable NO levels, but the relative increase is much greater in SkBF than NO. This led us to speculate ACh may dilate cutaneous blood vessels through PGs, as well as NO. To test this hypothesis, we performed a study in 11 healthy people. We measured SkBF by laser-Doppler flowmetry (LDF) at four skin sites instrumented for intradermal microdialysis. One site was treated with ketorolac (Keto), a nonselective cyclooxygenase antagonist. A second site was treated with NG-nitro-L-arginine methyl ester (L-NAME) to inhibit NO synthase. A third site was treated with a combination of Keto and L-NAME. The fourth site was an untreated control site. After the three treated sites received the different inhibiting agents, ACh was administered to all four sites by intradermal microdialysis. Finally, sodium nitroprusside (SNP) was administered to all four sites. Mean arterial pressure (MAP) was monitored by Finapres, and cutaneous vascular conductance (CVC) was calculated (CVC = LDF/MAP). For data analysis, CVC values for each site were normalized to their respective maxima as effected by SNP. The results showed that both Keto and L-NAME each attenuated the vasodilation induced by exogenous ACh (ACh control = 79 +/- 4% maximal CVC, Keto = 55 +/- 7% maximal CVC, L-NAME = 46 +/- 6% maximal CVC; P < 0.05, ACh vs. Keto or L-NAME). The combination of the two agents produced an even greater attenuation of ACh-induced vasodilation (31 +/- 5% maximal CVC; P < 0.05 vs. all other sites). We conclude that a portion of the vasodilation effected by exogenous ACh in skin is due to NO; however, a significant portion is also mediated by PGs. 相似文献
8.
A R Saad D P Stephens L A Bennett N Charkoudian W A Kosiba J M Johnson 《Journal of applied physiology》2001,91(6):2487-2492
The distribution of the reflex effects of isometric exercise on cutaneous vasomotor and sudomotor function is not clear. We examined the effects of isometric exercise by different muscle masses on skin blood flow (SkBF) and sweat rate (SR) in nonglabrous skin and in glabrous skin. The latter contains arteriovenous anastomoses (AVAs), which cause large fluctuations in SkBF. SkBF was measured by laser-Doppler flowmetry (LDF) and reported as cutaneous vascular conductance (CVC; LDF/mean arterial pressure). SR was measured by capacitance hygrometry. LDF and SR were measured at the sole, palm, forearm, and ventral leg during separate bouts of isometric handgrip (IHG) and isometric leg extension (ILE). CVC and its standard deviation decreased significantly during IHG and ILE in the palm and sole (P < 0.05) but not in the forearm or leg (P > 0.05). Only palmar SR increased significantly during IHG and ILE (P < 0.05). We conclude that the major reflex influences of isometric exercise on the skin include AVAs and palmar sweat glands and that this is true for both arm and leg exercise. 相似文献
9.
Saumet J. L.; Kellogg D. L. Jr; Taylor W. F.; Johnson J. M. 《Journal of applied physiology》1988,65(1):478-481
To find whether the measurement of skin blood flow (SkBF) by laser-Doppler flowmetry (LDF) is influenced by blood flow to underlying skeletal muscle, five subjects performed mild forearm exercise to induce a metabolic hyperemia in muscle in both forearms. This exercise consisted of alternative opening and closing of both hands at a frequency of approximately 1/s for a duration of 3 min. This exercise was performed twice by each subject. Forearm blood flow (FBF) by plethysmography increased from 2.64 +/- 0.49 (rest) to 31.11 +/- 9.95 ml.100 ml-1.min-1 (immediately after exercise) (P less than 0.001). No statistically significant postexercise increase was observed in LDF measured on the dorsal (110 +/- 21 to 105 +/- 21 mV) or ventral surface (266 +/- 113 to 246 +/- 77 mV) of the forearm. LDF measured from the chest also showed no significant change, indicating that the exercise was too mild to have reflex effects on SkBF. Moreover, the slope of the logarithmic linear regression and the half-time for recovery during the postexercise period for FBF were not reflected in LDF measurements from any of the three sites. We conclude that LDF measured from the skin surface is not influenced by blood flow to underlying skeletal muscle. 相似文献
10.
Joaquin U Gonzales Benjamin C Thompson John R Thistlethwaite Allison J Harper Barry W Scheuermann 《Journal of applied physiology》2007,103(6):1950-1957
To test the hypothesis that sex influences forearm blood flow (FBF) during exercise, 15 women and 16 men of similar age [women 24.3 +/- 4.0 (SD) vs. men 24.9 +/- 4.5 yr] but different forearm muscle strength (women 290.7 +/- 44.4 vs. men 509.6 +/- 97.8 N; P < 0.05) performed dynamic handgrip exercise as the same absolute workload was increased in a ramp function (0.25 W/min). Task failure was defined as the inability to maintain contraction rate. Blood pressure and FBF were measured on separate arms during exercise by auscultation and Doppler ultrasound, respectively. Muscle strength was positively correlated with endurance time (r = 0.72, P < 0.01) such that women had a shorter time to task failure than men (450.5 +/- 113.0 vs. 831.3 +/- 272.9 s; P < 0.05). However, the percentage of maximal handgrip strength achieved at task failure was similar between sexes (14% maximum voluntary contraction). FBF was similar between women and men throughout exercise and at task failure (women 13.6 +/- 5.3 vs. men 14.5 +/- 4.9 ml.min(-1).100 ml(-1)). Mean arterial pressure was lower in women at rest and during exercise; thus calculated forearm vascular conductance (FVC) was higher in women during exercise but similar between sexes at task failure (women 0.13 +/- 0.05 vs. men 0.11 +/- 0.04 ml.min(-1).100 ml(-1).mmHg(-1)). In conclusion, the similar FBF during exercise was achieved by a higher FVC in the presence of a lower MAP in women than men. Still, FBF remained coupled to work rate (and presumably metabolic demand) during exercise irrespective of sex. 相似文献
11.
Aging and the skin blood flow response to the unloading of baroreceptors during heat and cold stress. 总被引:2,自引:0,他引:2
Control of skin blood flow (SkBF) is on the efferent arm of both thermoregulatory and nonthermoregulatory reflexes. To what extent aging may affect the SkBF response when these two reflex systems interact is unknown. To determine the response of aged skin to the unloading of baroreceptors in thermoneutral, cold stress, and heat stress conditions, sequential bouts of nonhypotensive lower body negative pressure (LBNP) were applied at -10, -20, and -30 mmHg in 14 young (18-25 yr) and 14 older (63-78 yr) men. SkBF was measured by laser-Doppler velocimetry (averaged over 2 forearm sites), and data are expressed as percentage of maximal cutaneous vascular conductance (%CVC(max)). Total forearm blood flow was measured by venous occlusion plethysmography, and forearm vascular conductance (FVC) was calculated as the ratio of forearm blood flow to mean arterial pressure. In young men, all three intensities of LBNP in thermoneutrality decreased FVC significantly (P < 0.05), but FVC at -10 mmHg did not change in the older men. There were no significant LBNP effects on %CVC(max). Application of LBNP during cold stress did not significantly change %CVC(max) or FVC in either age group. During heat stress, -10 to -30 mmHg of LBNP decreased FVC significantly (P < 0.05) in both age groups, but these decreases were attenuated in the older men (P < 0.05). %CVC(max) decreased at -30 mmHg in the younger men only. These results suggest that older men have an attenuated skin vasoconstrictor response to the unloading of baroreceptors in heat stress conditions. Furthermore, the forearm vasoconstriction elicited by LBNP in older men reflects that of underlying tissue (i.e., muscle) rather than that of skin, whereas -30 mmHg LBNP also decreases SkBF in young hyperthermic men. 相似文献
12.
Christopher T Minson Lacy A Holowatz Brett J Wong W Larry Kenney Brad W Wilkins 《Journal of applied physiology》2002,93(5):1644-1649
Cutaneous vasodilation is reduced in healthy older vs. young subjects; however, the mechanisms that underlie these age-related changes are unclear. Our goal in the present study was to determine the role of nitric oxide (NO) and the axon reflexes in the skin blood flow (SkBF) response to local heating with advanced age. We placed two microdialysis fibers in the forearm skin of 10 young (Y; 22 +/- 2 yr) and 10 older (O; 77 +/- 5 yr) men and women. SkBF over each site was measured by laser-Doppler flowmetry (LDF; Moor DRT4). Both sites were heated to 42 degrees C for ~60 min while 10 mM N(G)-nitro-L-arginine methyl ester (L-NAME) was infused throughout the protocol to inhibit NO synthase (NOS) in one site and 10 mM L-NAME was infused after 40 min of local heating in the second site. Data were expressed as a percentage of maximal vasodilation (%CVC(max); 28 mM nitroprusside infusion). Local heating before L-NAME infusion resulted in a significantly reduced initial peak (Y: 61 +/- 2%CVC(max) vs. O: 46 +/- 4%CVC(max)) and plateau (Y: 93 +/- 2%CVC(max) vs. O: 82 +/- 5%CVC(max)) CVC values in older subjects (P < 0.05). When NOS was inhibited after 40 min of heating, CVC declined to the same value in the young and older groups. Thus the overall contribution of NO to the plateau phase of the SkBF response to local heating was less in the older subjects. The initial peak response was significantly lower in the older subjects in both microdialysis sites (Y: 52 +/- 4%CVC(max) vs. O: 38 +/- 5%CVCmax; P < 0.05). These data suggest that age-related changes in both axon reflex-mediated and NO-mediated vasodilation contribute to attenuated cutaneous vasodilator responses in the elderly. 相似文献
13.
Local warming of skin induces vasodilation by unknown mechanisms. To test whether nitric oxide (NO) is involved, we examined effects of NO synthase (NOS) inhibition with NG-nitro-L-arginine methyl ester (L-NAME) on vasodilation induced by local warming of skin in six subjects. Two adjacent sites on the forearm were instrumented with intradermal microdialysis probes for delivery of L-NAME and sodium nitroprusside. Skin blood flow was monitored by laser-Doppler flowmetry (LDF) at microdialysis sites. Local temperature (Tloc) of the skin at both sites was controlled with special LDF probe holders. Mean arterial pressure (MAP; Finapres) was measured and cutaneous vascular conductance calculated (CVC = LDF/MAP = mV/mmHg). Data collection began with a control period (Tloc at both sites = 34 degrees C). One site was then warmed to 41 degrees C while the second was maintained at 34 degrees C. Local warming increased CVC from 1.44 +/- 0.41 to 4.28 +/- 0.60 mV/mmHg (P < 0.05). Subsequent L-NAME administration reduced CVC to 2.28 +/- 0.47 mV/mmHg (P < 0.05 vs. heating), despite the continued elevation of Tloc. At a Tloc of 34 degrees C, L-NAME reduced CVC from 1.17 +/- 0.23 to 0.75 +/- 0.11 mV/mmHg (P < 0.05). Administration of sodium nitroprusside increased CVC to levels no different from those induced by local warming. Thus NOS inhibition attenuated, and sodium nitroprusside restored, the cutaneous vasodilation induced by elevation of Tloc; therefore, the mechanism of cutaneous vasodilation by local warming requires NOS generation of NO. 相似文献
14.
Walker KL Saunders NR Jensen D Kuk JL Wong SL Pyke KE Dwyer EM Tschakovsky ME 《American journal of physiology. Heart and circulatory physiology》2007,293(5):H2928-H2936
We tested the hypothesis that vasoregulatory mechanisms completely counteract the effects of sudden changes in arterial perfusion pressure on exercising muscle blood flow. Twelve healthy young subjects (7 female, 5 male) lay supine and performed rhythmic isometric handgrip contractions (2 s contraction/ 2 s relaxation 30% maximal voluntary contraction). Forearm blood flow (FBF; echo and Doppler ultrasound), mean arterial blood pressure (arterial tonometry), and heart rate (ECG) were measured. Moving the arm between above the heart (AH) and below the heart (BH) level during contraction in steady-state exercise achieved sudden approximately 30 mmHg changes in forearm arterial perfusion pressure (FAPP). We analyzed cardiac cycles during relaxation (FBF(relax)). In an AH-to-BH transition, FBF(relax) increased immediately, in excess of the increase in FAPP (approximately 69% vs. approximately 41%). This was accounted for by pressure-related distension of forearm resistance vasculature [forearm vascular conductance (FVC(relax)) increased by approximately 19%]. FVC(relax) was restored by the second relaxation. Continued slow decreases in FVC(relax) stabilized by 2 min without restoring FBF(relax). In a BH-to-AH transition, FBF(relax) decreased immediately, in excess of the decrease in FAPP (approximately 37% vs. approximately 29%). FVC(relax) decreased by approximately 14%, suggesting pressure-related passive recoil of resistance vessels. The pattern of FVC(relax) was similar to that in the AH-to-BH transition, and FBF(relax) was not restored. These data support rapid myogenic regulation of vascular conductance in exercising human muscle but incomplete flow restoration via slower-acting mechanisms. Local arterial perfusion pressure is an important determinant of steady-state blood flow in the exercising human forearm. 相似文献
15.
Effects of hormone replacement on growth hormone and prolactin exercise responses in postmenopausal women 总被引:1,自引:0,他引:1
Kraemer R. R.; Johnson L. G.; Haltom R.; Kraemer G. R.; Gaines H.; Drapcho M.; Gimple T.; Castracane V. Daniel 《Journal of applied physiology》1998,84(2):703-708
Kraemer, R. R., L. G. Johnson, R. Haltom, G. R. Kraemer, H. Gaines, M. Drapcho, T. Gimple, and V. Daniel Castracane. Effects of hormone replacement on growth hormone and prolactin exercise responses in postmenopausal women. J. Appl.Physiol. 84(2): 703-708, 1998.Exercise elevatesgrowth hormone (GH) and prolactin (PRL) blood concentrations inpremenopausal women. Postmenopausal women taking hormone replacementtherapy (HRT) maintain higher estrogen levels that could affect GH andPRL. The purpose of the study was to determine the effects of HRT on GHand PRL responses to treadmill exercise. Seventeen healthy women whowere postmenopausal (naturally or surgically) [8 on HRT; 9 not onHRT (NHRT)], completed 30 min of treadmill exercise at 79.16 ± 1.2% maximal O2 consumption (HRT group) and 80.19 ± 0.91% maximalO2 consumption (NHRT group). Bloodsamples were collected from an intravenous catheter during an exercisesession and during a control session without exercise. GH and PRLconcentrations were significantly higher in the exercise trial than inthe nonexercise trial, whereas resting concentrations were similar forboth trials. GH and PRL peaked at 10.8 ± 1.60 and 12.67 ± 2.58 ng/ml, respectively, for HRT subjects and at 4.90 ± 1.18 and 9.04 ± 2.17 ng/ml, respectively, for NHRT subjects. GH concentrations inthe exercise trial were significantly higher for HRT than for NHRTsubjects. This is the first study to demonstrate that HRT enhancestreadmill-exercise-induced GH release and that similar PRL responses totreadmill exercise occur in postmenopausal women regardless of HRTstatus. 相似文献
16.
Increasing maximal heart rate increases maximal O2 uptake in rats acclimatized to simulated altitude
Gonzalez Norberto C.; Clancy Richard L.; Moue Yoshihiro; Richalet Jean-Paul 《Journal of applied physiology》1998,84(1):164-168
Gonzalez, Norberto C., Richard L. Clancy, Yoshihiro Moue,and Jean-Paul Richalet. Increasing maximal heart rate increases maximal O2 uptake in ratsacclimatized to simulated altitude. J. Appl.Physiol. 84(1): 164-168, 1998.Maximal exerciseheart rate (HRmax) is reducedafter acclimatization to hypobaric hypoxia. The lowHRmax contributes to reducemaximal cardiac output(max) andmay limit maximal O2 uptake(O2 max). Theobjective of these experiments was to test the hypothesisthat the reduction inmax afteracclimatization to hypoxia, due, in part, to the lowHRmax, limitsO2 max. Ifthis hypothesis is correct, an increase in max wouldresult in a proportionate increase inO2 max. Rats acclimatized to hypobaric hypoxia [inspiredPO2(PIO2) = 69.8 ± 3 Torr for 3 wk] exercised on a treadmill in hypoxic (PIO2 = 71.7 ± 1.1 Torr) or normoxic conditions(PIO2 = 142.1 ± 1.1 Torr). Each rat ran twice: in one bout the rat was allowed to reach itsspontaneous HRmax, which was 505 ± 7 and 501 ± 5 beats/min in hypoxic and normoxic exercise,respectively; in the other exercise bout,HRmax was increased by 20% to the preacclimatization value of 600 beats/min by atrial pacing. This resulted in an ~10% increase inmax, since theincrease in HRmax was offset by a10% decrease in stroke volume, probably due to shortening of diastolicfilling time. The increase inmax was accompanied by a proportionate increase in maximal rate of convective O2 delivery(max × arterial O2 content), maximal workrate, and O2 max inhypoxic and normoxic exercise. The data show that increasingHRmax topreacclimatization levels increasesO2 max, supportingthe hypothesis that the lowHRmax tends to limitO2 max after acclimatization to hypoxia. 相似文献
17.
Graded cutaneous vascular responses to dynamic leg exercise 总被引:2,自引:0,他引:2
Taylor W. F.; Johnson J. M.; Kosiba W. A.; Kwan C. M. 《Journal of applied physiology》1988,64(5):1803-1809
The cutaneous vascular conductance-esophageal temperature (CVC-Tes) relationship was examined at five work loads (75-200 W) in each of four men to find whether there is a role for exercise intensity in the control of skin blood flow (SkBF). Several factors contributed to our evaluation of the CVC-Tes relationship during work. Laser-Doppler velocimetry (LDF) provided a continuous measure of SkBF that is not influenced by underlying muscle blood flow. Local warming to 39 degrees C at the site of measurement of SkBF provided a consistent skin temperature and facilitated observation of changes in LDF. Mean arterial pressure was measured noninvasively once per minute to calculate CVC. Supine exercise minimized baroreceptor-induced cutaneous vasoconstriction. Our major finding was that the internal temperature at which CVC began to rise during exercise (CVC threshold) was graded with work load beyond 125 W (P less than 0.05). In that range the CVC threshold increased by 0.16 degrees C for every increment of 25 W. The CVC threshold was never reached at the highest work load in three of the four subjects. There was no consistent effect of work load on the slope of the CVC-Tes relationship or on the internal temperature at which sweating began during exercise (sweat rate threshold). We conclude that the level of work beyond 125 W affects the CVC-Tes relationship in a graded fashion, principally through shifts in threshold. 相似文献
18.
VO2 max is associated with ACE genotype in postmenopausal women 总被引:6,自引:0,他引:6
Hagberg James M.; Ferrell Robert E.; McCole Steve D.; Wilund Kenneth R.; Moore Geoffrey E. 《Journal of applied physiology》1998,85(5):1842-1846
Relationships have frequently been found betweenangiotensin-converting enzyme (ACE) genotype and various pathologicaland physiological cardiovascular outcomes and functions. Thuswe sought to determine whether ACE genotype affected maximalO2 consumption (O2 max) and maximalexercise hemodynamics in postmenopausal women with different habitualphysical activity levels. Age, body composition, and habitual physicalactivity levels did not differ among ACE genotype groups. However, ACEinsertion/insertion (II) genotype carriers had a 6.3 ml · kg1 · min1higher O2 max(P < 0.05) than the ACEdeletion/deletion (DD) genotype group after accounting for the effectof physical activity levels. The ACE II genotype group also had a 3.3 ml · kg1 · min1higher O2 max(P < 0.05) than the ACEinsertion/deletion (ID) genotype group. The ACE ID group tended to havea higher O2 max thanthe DD genotype group, but the difference was not significant. ACEgenotype accounted for 12% of the variation inO2 max among womenafter accounting for the effect of habitual physical activity levels.The entire difference inO2 max among ACEgenotype groups was the result of differences in maximal arteriovenousO2 difference (a-vDO2).ACE genotype accounted for 17% of the variation in maximal a-vDO2 inthese women. Maximal cardiac output index did not differ whatsoeveramong ACE genotype groups. Thus it appears that ACE genotype accountsfor a significant portion of the interindividual differences inO2 max among thesewomen. However, this difference is the result of genotype-dependentdifferences in maximala-vDO2 andnot of maximal stroke volume and maximal cardiac output. 相似文献
19.
Effect of luteal phase elevation in core temperature on forearm blood flow during exercise 总被引:1,自引:0,他引:1
Kolka, Margaret A., and Lou A. Stephenson. Effect ofluteal phase elevation in core temperature on forearm blood flow duringexercise. J. Appl. Physiol. 82(4):1079-1083, 1997.Forearm blood flow (FBF) as an index of skinblood flow in the forearm was measured in five healthy women by venousocclusion plethysmography during leg exercise at 80% peak aerobicpower and ambient temperature of 35°C (relative humidity 22%;dew-point temperature 10°C). Resting esophagealtemperature (Tes) was 0.3 ± 0.1°C higher in the midluteal than in the early follicular phase ofthe menstrual cycle (P < 0.05).Resting FBF was not different between menstrual cycle phases. TheTes threshold for onset of skinvasodilation was higher (37.4 ± 0.2°C) in midluteal than inearly follicular phase (37.0 ± 0.1°C; P < 0.05). The slope of the FBF toTes relationship was not different between menstrual cycle phases (14.0 ± 4.2 ml · 100 ml1 · min1 · °C1for early follicular and 16.3 ± 3.2 ml · 100 ml1 · min1 · °C1for midluteal phase). Plateau FBF was higher during exercise inmidluteal (14.6 ± 2.2 ml · 100 ml1 · min1 · °C1)compared with early follicular phase (10.9 ± 2.4 ml · 100 ml1 · min1 · °C1;P < 0.05). The attenuation of theincrease in FBF to Tes occurred when Tes was 0.6°C higher andat higher FBF in midluteal than in early follicular experiments(P < 0.05). In summary, the FBF response is different during exercise in the two menstrual cycle phasesstudied. After the attenuation of the increase in FBF and whileTes was still increasing, thegreater FBF in the midluteal phase may have been due to the effects ofincreased endogenous reproductive endocrines on the cutaneousvasculature. 相似文献
20.
Regional deposition of inhaled particles in human lungs: comparison between men and women 总被引:3,自引:0,他引:3
We measured detailed regional depositionpatterns of inhaled particles in healthy adult male(n = 11; 25 ± 4 yr of age) and female (n = 11; 25 ± 3 yr of age)subjects by means of a serial bolus aerosol delivery technique formonodisperse fine [particle diameter(Dp) = 1 µm] and coarse aerosols(Dp = 3 and 5 µm). The bolus aerosol (40 ml half-width) was delivered to a specificvolumetric depth (Vp) of the lung ranging from 100 to 500 ml with a50-ml increment, and local deposition fraction (LDF) was assessed for each of the 10 local volumetric regions. In all subjects, the deposition distribution pattern was very uneven with respect to Vp,showing characteristic unimodal curves with respect to particle sizeand flow rate. However, the unevenness was more pronounced in women.LDF tended to be greater in all regions of the lung in women than inmen for Dp = 1 µm. For Dp = 3 and 5 µm, LDF showed a marked enhancement in the shallow region of Vp 200 ml in women compared with men(P < 0.05). LDF in women wascomparable to or smaller than those of men in deep lung regions of Vp > 200 ml. Total lung deposition was comparable between men and womenfor fine particles but was consistently greater in women than men forcoarse particles regardless of flow rates used: the difference rangedfrom 9 to 31% and was greater with higher flow rates(P < 0.05). The results indicatethat 1) particledeposition characteristics differ between healthy men and women undercontrolled breathing conditions and2) deposition in women is greaterthan that in men. 相似文献