Aging and the effect of increased after-load on left ventricular contractile state

Hemodynamic and contractile states were studied echocardiographically in 10 young (28 +/- 3 yr) and 10 elderly (67 +/- 4 yr) male subjects at rest and during upright isometric exercise which involved the hands, hips, legs, and lower back muscle groups (deadlift) at 30% of maximum voluntary contraction for 3 min. During deadlift, both groups showed similar and significant increases in blood pressure and heart rate, compared to the resting values. Ejection fraction at rest did not differ significantly between the two groups. During deadlift, it remained unchanged in the elderly white ejection fraction increased significantly in the younger subjects. No significant changes in left ventricular end-diastolic volume occurred in either group during deadlift. End-systolic volume remained unchanged in the elderly while it decreased significantly in the younger subjects. These data indicate that cardiovascular responses and contractile state in normal young men and normal exercise-trained elderly subjects were augmented during upright sub-maximal isometric deadlift exercise, utilizing large muscle mass. However, left ventricular contractility increased less in the elderly subjects compared to the younger subjects.     

Left ventricular volumes and hemodynamic responses to postexercise ischemia in healthy humans

PURPOSE: The purpose of this study was to determine the cardiac mechanisms involved in cardiovascular adjustments during postexercise circulatory occlusion (OCCL). METHOD: Heart rate (HR), mean arterial pressure (MAP), left ventricular end-diastolic (EDV) and end-systolic volumes (ESV), stroke volume (SV), cardiac output (CO), and total peripheral vascular resistance (total peripheral resistance (TPR)) were assessed in nine healthy volunteers during rest and static exercise at 30% of maximum voluntary contraction followed by either OCCL for 3 min or non-OCCL in a randomized crossover protocol. RESULTS: During handgrip, HR (+20%; P < 0.001), CO (+11%; P = 0.003), MAP (+18%; P = 0.001), and TPR (+6%; P = 0.004) increased, SV (-8%; P = 0.001) and EDV (-5%; P < 0.001) decreased, while ESV did not change (P > 0.05). These responses were similar between conditions (P > 0.05). During OCCL, HR, SV, and CO returned to baseline, whereas MAP (+19%; P < 0.001) and TPR (+9%; P = 0.004) remained elevated. EDV (+12%; P < 0.001) and ESV (+23%; P < 0.001) increased in parallel above resting values. CONCLUSION: Activation of muscle metaboreceptors during OCCL increased MAP by elevating TPR. Despite the higher afterload and increased ESV, CO and SV were kept similar to resting values because EDV also increased, implying the involvement of the Frank-Starling mechanism.     

Comparison of exercise responses of males and females during acute exposure to hypobaria

Seventeen male and 20 female college students were tested on a bicycle ergometer in a hypobaric chamber to determine whether both sexes had similar submax and max exercise responses to acute hypoxia. Initial testing was at a terrestrial altitude of 1576 m, to which the subjects were acclimated; subsequent tests were at simulated altitudes of 2743 m and 3962 m. Analysis of covariance showed that inspired V was the only variable during submaximal work (50% max) to exhibit a significant difference in altitude response between males and females; women had a smaller increase than men. During max work, V and O2 pulse increased less in women. At 2743 m, max VO2 decreased more in females whereas, at 3962 m, no difference was noted. It was concluded that during both submaximal and maximal work with acute altitude exposure, women would demonstrate smaller relative increases in ventilation than would men.     

Estrogen variation and resting left ventricular structure and function in young healthy females

PURPOSE: A potential confounding factor in the interpretation of left ventricular (LV) structural and functional data in female subjects could be menstrual phase or contraceptive use upon assessment. To date no study has addressed this issue. METHODS: Seventeen eumenorrheic (EU; mean +/- SD age = 21 +/- 3 yr) and 14 combined-oral contraceptive pill-using (COC: mean +/- SD age = 21 +/- 3 yr) females volunteered to participate. The EU had stable menstrual cycles and the COC had all been using the same pill preparation for a minimum of 6 months. Echocardiographic examinations occurred during the mid-follicular phase and mid-luteal phases in the EU and during mid-consumption and mid-end of withdrawal in the COC. LV structure and function were assessed using M-mode and pulsed-wave Doppler echocardiography. Data were compared via Student t-tests and limits of agreement (LoA) were calculated. RESULTS: Structure and function did not significantly differ between phases of the menstrual cycle or between consumption and withdrawal of oral contraception (P > 0.05). However, there was considerable variance in the LoA between variables. Smaller LoA were reported for those variables directly measured from echocardiograms compared with those from derived data. For example, in a measured variable such as LV internal dimension in diastole, the LoA data represented a variation of +/- 0.4 mm (+/- 1%) between phases. Conversely, data for LV mass, a derived variable, reported LoA values of +/- 15 g (10%) between phases. The LoA were consistent between EU and COC. Variation in both measured and derived variables were within, or close to, accepted limits of measurement or biological error. CONCLUSION: It would seem that in studies assessing LV structure and function in women the influence of menstrual phase or oral contraceptive use is of minor significance.     

Bilateral difference in hamstrings to quadriceps ratio in healthy males and females

ObjectiveTo compare the isometric and isokinetic hamstrings to quadriceps (H:Q) ratio 1) between the dominant (D) and non-dominant (ND) legs, and 2) between healthy males and females.DesignCross-sectional.SettingUniversity research laboratory. Quadriceps and hamstrings strength were assessed by maximum isometric contractions at six angles (40°, 50°, 60°, 70°, 80°, 90°) and concentric contractions at three angular velocities (60° s^?1, 180° s^?1, 300° s^?1).ParticipantsForty physically active adults (25 males).Main outcome measuresPeak isometric and isokinetic torques of the quadriceps and hamstrings, and the corresponding H:Q ratios.ResultsIsometric H:Q ratio increased with greater knee extension (P < 0.001), with overall a higher ratio in the D leg (P < 0.001). Isokinetic H:Q ratio increased with angular velocity (P < 0.001), with a higher ratio in the D leg (P < 0.05). Neither isometric nor isokinetic H:Q ratios differed between males and females.ConclusionsWhen setting rehabilitation goals, it may be appropriate to adjust the H:Q ratio and leg strength based on the uninvolved leg with consideration of leg dominance. Gender-related differences do not explain the discrepancy in the literature regarding bilateral differences in the H:Q ratio. Other subject characteristics such as age and training may be more relevant.     

Comparison of left ventricular performance in healthy young women and men during exercise

Background

Previous studies show sex-related differences in left ventricular (LV) response to exercise. It is not clear, however, whether these differences are also seen in younger healthy subjects.

Methods and Results

This study examined the changes in LV performance during dynamic upright exercise in 11 healthy men and 19 healthy young women according to the Bruce protocol and an individualized ramp protocol. There were no significant differences between the two protocols for either men or women in heart rate, blood pressure, LV ejection fraction (EF) (measured by ambulatory nuclear detector), and measured oxygen consumption. The peak oxygen consumption was higher in men than in women (44±13 vs 36±9 ml/kg/min; p<0.05), but the peak heart rate, systolic blood pressure, and EF were similar. The change in EF (from rest to exercise) was 19%±8% in men and 19%±11% in women with the Bruce protocol (difference not significant) and 26%±9% in men and 19%±6% in women with the ramp protocol (difference not significant). At peak exercise, both men and women showed an increase in end-diastolic volume (29%±14% vs 23%±11%; difference not significant) and a decrease in end-systolic volume (41%±15% vs 43%±21%) (difference not significant). The increase in cardiac output during exercise was due to an increase in heart rate and stroke volume in both men and women. At submaximal exercise, however, the decrease in end-systolic volume was less in women than in men (p<0.05).

Conclusions

There are no sex-related differences in compensatory mechanism during dynamic execise in healthy subjects. The changes in contractility and LV volume are not affected by the exercise protocol.     

Effects of blood withdrawal on cardiac,hemodynamic, and pulmonary responses to a moderate acute workload in healthy middle-aged and older females

ObjectivesTo investigate the effects of blood withdrawal on cardiac, hemodynamic, and pulmonary responses to submaximal exercise in females.Design and methods30 healthy females (63.8 ± 8.3 years) were recruited for this experimental study. Transthoracic echocardiography, non-invasive blood pressure monitoring, and oxygen uptake were assessed during a fixed submaximal workload (100 W) prior to (day 1) and immediately after (day 2) a 10% reduction of blood volume. Main measurements included left ventricular end-diastolic volume, stroke volume, cardiac output, mean arterial pressure, systolic blood pressure, diastolic blood pressure, and oxygen uptake. Blood volume was determined via carbon monoxide rebreathing.ResultsParticipant's blood volume ranged from 3.8 to 6.6 L. Following 10% reduction in blood volume (0.5 ± 0.1 L), left ventricular end-diastolic volume (p ≤ 0.030) and stroke volume (p < 0.019) were reduced during submaximal exercise while cardiac output was unchanged (p = 0.139) due to increased heart rate (p < 0.026). Hemodynamic variables including mean arterial pressure (p < 0.015), systolic blood pressure (p < 0.005), and diastolic blood pressure (p < 0.038) were reduced while oxygen uptake was unaltered (p = 0.250).ConclusionsBlood withdrawal results in marked reductions in cardiac filling with compensatory chronotropic responses that preserve cardiac output at a moderate submaximal workload in healthy females. Thus, blood volume determines the relative exercise intensity, as typically determined by heart rate, of submaximal efforts in this population.     

Endogenous anabolic hormonal and growth factor responses to heavy resistance exercise in males and females.

To examine endogenous anabolic hormonal responses to two different types of heavy resistance exercise protocols (HREPs), eight male and eight female subjects performed two randomly assigned protocols (i.e. P-1 and P-2) on separate days. Each protocol consisted of eight identically ordered exercises carefully designed to control for load, rest period length, and total work (J) effects. P-1 utilized a 5 RM load, 3-min rest periods and had lower total work than P-2. P-2 utilized a 10 RM load, 1-min rest periods and had a higher total work than P-1. Whole blood lactate and serum glucose, human growth hormone (hGH), testosterone (T), and somatomedin-C [SM-C] (i.e. insulin-like growth factor 1, IGF-1) were determined pre-exercise, mid-exercise (i.e. after 4 of the 8 exercises), and at 0, 5, 15, 30, and 60 min post-exercise. Males demonstrated significant (p less than 0.05) increases above rest in serum T values, and all serum concentrations were greater than corresponding female values. Growth hormone increases in both males and females following the P-2 HREP were significantly greater at all time points than corresponding P-1 values. Females exhibited significantly higher pre-exercise hGH levels compared to males. The P-1 exercise protocol did not result in any hGH increases in females. SM-C demonstrated random significant increases above rest in both males and females in response to both HREPs.(ABSTRACT TRUNCATED AT 250 WORDS)     

Comparison of outcomes between males and females after anterior cruciate ligament reconstruction

Few studies have specifically addressed the potential differences in outcome from ACL reconstruction between males and females. The present study compared patient-reported outcomes between the sexes after a minimum of 2 years following arthroscopic ACL reconstruction using bone-patellar tendon-bone autograft. Patients were also categorized as acute or chronic based on the time from injury to surgery. Outcome questionnaires were mailed to 638 patients, resulting in 151 eligible respondents included in the analysis. The outcome instruments used were the Cincinnati scale, the ACL-Quality of Life scale, and the Tegner activity rating scale. At an average of 5 years following ACL reconstruction no differences were found between males (n=74) and females (n=77) on the ACL-QOL scale. Females perceived a significantly higher activity level prior to surgery according to the Tegner scale. However, no other differences were identified by gender or stage based on prior, highest, or current Tegner activity levels. Results of the Cincinnati scale for the entire sample showed that females scored an average of 5.7 points lower than males. Analysis of this difference by patient age indicates a trend toward lower scores in females between 12-18 and over 24 years old. Chronicity was not a factor that affected outcome in either males or females. No differences were found in the number of patients who complained of anterior knee pain. We conclude that autogenous bone-patella tendon-bone ACL reconstruction is equally successful in well-matched populations of males and females.     

Ventilatory responses to exercise in patients with asymptomatic left ventricular dysfunction.

PURPOSE: Based on reports that patients with severe left ventricular (LV) dysfunction have a greater ventilatory response to effort than healthy people, we evaluated the ventilatory responses to effort of patients with coronary artery disease and various degrees of LV impairment before and after 6 months of exercise training in a community-based cardiac rehabilitation program. METHODS: Out of 171 patients consecutively referred for cardiac rehabilitation, 102 were enrolled in the study. Fifteen patients were excluded because of lung disease and 54 because of poor adherence to the exercise program. Patients were divided into three groups according to their ejection fraction (EF): Group 1 (G1) included 63 patients with EF > or = 50%, Group 2 (G2) included 21 patients with EF > or = 35 and < 50% and group 3 (G3) included 18 patients with EF < 35%. Peak oxygen uptake, minute ventilation (V(E)), and minute carbon dioxide production (VCO2) were measured before and after training in all participants. RESULTS: All groups showed a significant increase in peak oxygen uptake and treadmill time after training (G1: P = 0.0001 and P = 0.0001; G2: P = 0.0001 and P = 0.001; G3: P = 0.01 and P = 0.01; respectively). Patients in G3 had a significantly higher V(E)/VCO2 ratio than patients in G2 and G1 at 9 min and peak exercise, before (9 min: P = 0.046 and P = 0.025, peak: P = 0.024 and P = 0.002, respectively) and after training (9 min: P = 0.011 and P = 0.005, peak: P = 0.001 and P = 0.0001, respectively). The slope of the relation V(E) to VCO2 was significantly higher in G3 patients than in those in G2 and G1 (P = 0.0001, respectively) and was not reduced by exercise training in any group. CONCLUSIONS: Patients with severe LV dysfunction had a greater ventilatory response to exercise than those with moderately impaired or normal LV function. Exercise training increased the effort tolerance of all patients irrespective of their degree of LV dysfunction but failed to reduce the higher ventilatory responses to effort of patients with EF below 35%.     

Energetics of backstroke swimming in males and females.

The aims of this study were to compare the oxygen demand of back crawl in male and female competitive swimmers and to examine the effect of stroke mechanics on these costs. Twenty-two male and 16 female swimmers participated in the study. The VO2 increased with v2 to a peak of approximately 4.03 l.min-1 in males and of approximately 2.88 l.min-1 in females. Mean VO2 of the males at a given v was significantly higher than that of the female swimmers, but the slopes of the regression lines were identical. Increases of velocity in both groups were related to increases in f and a decrease in distance. Costs per stroke (ml O2.str-1) in males were significantly higher than in females at a v = 1.0, 1.1, and 1.2 m.s-1. The relationship between VO2 and body mass at v = 1.1 m.s-1 was evaluated by deriving the exponent b in the allometric equation VO2 = a Mb. The exponent b was found to be 0.55. These results indicate that submaximal VO2 in back crawl swimming does not increase in proportion to body mass and may explain why VO2 (l.min-1) has been found to be higher in males than in females.     

瑞芬太尼与舒芬太尼抑制患者气管插管血液动力学反应效果的比较

目的比较等效剂量的瑞芬太尼与舒芬太尼抑制患者气管插管血液动力学反应的效果。方法择期腹部手术患者166例,ASAⅠ级或Ⅱ级,年龄18～63岁。随机分为两组：瑞芬太尼组（R组,n=83）和舒芬太尼组（S组,n=83）。麻醉诱导：静脉注射咪达唑仑0．1mg／kg、异丙酚2．5mg／kg、瑞芬太尼1μg／kg（R组）或舒芬太尼0．1μg／kg（S组）、维库溴铵0．1mg／kg,气管插管后机械通气。于麻醉诱导前（基础值）、气管插管前后即刻、气管插管后lmin、3min、5min时记录SP、DP、MAP和HR．观察气管插管反应的发生情况。结果与基础值比较,两组其余时间点血液动力学指标均降低（P〈0．05）,且R组低于S组（P〈0．05）;S组BP和HR最大值较基础值升高,R组较基础值降低（P〈0．05）。结论在复合异丙酚一维库溴铵麻醉诱导时．等效剂量的瑞芬太尼较舒芬太尼抑制患者气管插管血液动力学反应的效果好。     

Muscle fiber-specific glycogen utilization in strength-trained males and females

This study evaluated the effect of strength training on glycogen utilization in slow twitch (ST) and fast twitch (FT) muscle fibers during repeated maximal unilateral isokinetic leg extensions at 180 degrees.s-1. Strength-trained (5 males, 4 females) and untrained (4 males, 6 females) subjects performed three sets of 50 maximum voluntary contractions (MVC) at this velocity with 10-min rest intervals between sets. Biopsies were taken from the vastus lateralis muscle before and after each exercise session. Glycogen content of the fibers was quantified as optical density (OD) using microspectrophotometric densitometry on serial cross-sections of muscle tissue stained with a periodic acid Schiff reagent stain after individual fibers were identified as ST or FT according to a stain for myofibrillar ATPase activity. Analysis of variance with repeated measures yielded the following results: OD, i.e., glycogen, was reduced similarly in both fiber types after exercise, but only in the males (P = 0.02); there was no significant main effect of training status per se (i.e., strength-trained vs untrained). These results indicate that years of strength training do not change the pattern of muscle fiber-specific glycogen utilization during repeated dynamic MVCs.     

Radionuclide ventriculographic quantitation of left ventricular dimensions. Comparison to echocardiography.

Left ventricular internal cavity dimensions (LVID) were determined from radionuclide ventriculographic (RNVG) studies using a spatial calibration algorithm and visually defined edges and were compared to the results from two-dimensional echocardiography. Routine clinical cases were used with no additional views and no attenuation or scatter correction. In an initial set of 21 patients, mean RNVG LVID was 5.7 +/- 1.1 (mean +/- 1 S.D.) cm compared to 5.3 +/- 1.0 cm for echocardiography. In a prospective validation of the regression equations derived in the initial set of patients, regression-corrected RNVG results were within 5 mm of those determined echocardiographically in 18/22 patients and the mean LVID values were the same. Quantitative estimation of LVID by RNVG is simple, rapid, and reproducible. Systematic overestimation of dimensions compared to echocardiography can be corrected using a regression equation.     

The calculation of blood ethanol concentrations in males and females

In German-speaking countries, blood ethanol concentrations (BECs) are usually calculated using Widmark’s equation. The distribution factor r of this equation is a correction factor needed to obtain a reduced body mass and corresponds to the ratio of total body water and blood water content. To enhance the reliability of Widmark’s model equation, the body weight, body height, blood water content and total body water of 256 women and 273 men were measured. The ratio of body water to blood water ranged from 0.44 to 0.80 in women and from 0.60 to 0.87 in men. For both sexes equations were developed by multiple regression analysis which allow the determination of the individual, more realistic distribution factors r_FI (for females) and r_MI (for males) even when only body height and body weight are known. Drinking experiments revealed a clearly higher congruence of calculated and measured blood ethanol concentrations when r_FI or r_MI were used instead of rigid distribution factors, i.e. 0.6 for women and 0.7 for men with or without the assumption of a 10% so-called resorption deficit. Additionally, Widmark’s equation in combination with r_FI or r_MI allows a more accurate prediction of blood ethanol concentrations than the equations of Watson and Ulrich. Received: 25 October 1999 / Accepted: 17 March 2000     

Measurement of right and left ventricular volumes in healthy individuals with cine MR imaging

Cine magnetic resonance (MR) imaging is a new, rapid MR pulse sequence that acquires up to 32 images per cardiac cycle at up to four levels of the heart within 4 minutes. In this study, the whole heart was encompassed by contiguous 10-mm transverse sections. Ventricular volumes were calculated by adding luminal areas determined in each section at end-diastole and end-systole. The left ventricular volume index was 57 ml/m2 +/- 9 at end-diastole and 17 ml/m2 +/- 4 at end-systole. The right ventricular volume index was 63 ml/m2 +/- 9 at end-diastole and 22 ml/m2 +/- 6 at end-systole. The left to right ventricular stroke volume ratio was 0.97 +/- 0.06, which was not statistically different from the theoretically expected ratio of 1. Interobserver and intraobserver measurements were closely correlated. Volume measurements were validated with two-dimensional echocardiography in five volunteers. Cine MR imaging allows reproducible three-dimensional measurement of right and left ventricular volumes with short imaging time and good temporal resolution.     

Comparison of iopromide and iopamidol in left ventricular angiography and in coronary angiography

A double blind randomized trial of two non-ionic contrast media--iopamidol and iopromide--was performed on 101 patients undergoing left ventriculography and coronary angiography. Both products performed well in the trial and there were no statistically significant differences in side effects, cardiovascular parameters, blood analysis or film quality between the two products.     

Physiologic responses to treadmill running in adult and prepubertal males

Little data are available directly comparing physiologic responses to endurance exercise in children and adults. To evaluate age related differences during maximal and submaximal treadmill exercise, physiologic parameters recorded during testing of 20 active prepubertal boys (aged 9-13 years) were compared with values obtained in nonathletic adult males aged 23-33 years. Maximum oxygen consumption (VO2 max) was 57.9 ml.kg-1.min-1 (6.9 SD) in the boys and 48.3 ml.kg-1.min-1 (4.9 SD) in the adults. Running economy examined both as VO2 at a treadmill speed of 9.6 kph and as the slope of linear regression of VO2 at four submaximal speeds was less in boys compared to men when values were expressed per kg body mass. Differences in running economy between the two groups disappeared, however, when related to body surface area. As expected, children had a higher stride frequency at a given treadmill speed, but running stride frequency was unrelated to economy with the two groups. Lower respiratory exchange ratios were observed at maximal and submaximal exercise in the children, which may reflect diminished anaerobic capacity or differences in substrate utilization. These results substantiate the high aerobic capacity previously observed in children and suggest that lower running economy in younger subjects may largely relate to a greater body surface are/mass ratio.