Total blood volume in endurance-trained postmenopausal females: relation to exercise mode and maximal aerobic capacity

We have recently shown that postmenopausal female distance runners demonstrate elevated levels of blood volume compared with sedentary healthy peers. We also found a strong positive relation between blood volume and maximal oxygen consumption. In young adult males, endurance exercise training increases blood volume when performed in the upright, but not in the supine body position. Based on these observations, we hypothesized that among postmenopausal females, the elevation in blood volume would be absent or attenuated in women who train in the horizontal vs. upright body position, and that the lower blood volume in the former would be associated with lower maximal aerobic capacity. Thus, we measured supine resting plasma and total blood volumes (Evans blue dye) and maximal oxygen consumption in postmenopausal women: 10 sedentary controls, 10 swimmers and 10 runners matched for age (60 ± 2; 59 ± 2; 58 ± 2 years, mean ± SE) and hormone replacement use (5 per group). The swimmers and runners were further matched for training volume (4.5 ± 0.2 vs. 4.8 ± 0.6 h week^–1), relative performance (78 ± 5 vs. 75 ± 3% of age-group world record) and fat-free mass (45.5 ± 0.8 vs. 44.9 ± 1.5 kg). Total blood volume and maximal oxygen consumption were highest in the runners (81.2 ± 4; 52.4 ± 3 mL kg^–1, respectively) and progressively lower in the swimmers (68.8 ± 3; 44.2 ± 2) and controls (59.2 ± 2; 37.9 ± 2; all P < 0.05). In the pooled population, blood volume was positively related to maximal oxygen consumption (r= 0.72, P < 0.0001). We conclude that in endurance-trained postmenopausal females matched for training volume and competitive performance: (1) blood volume is lower in those who train in the horizontal (swimmers) compared with the upright position (runners); (2) the lower blood volume is associated with a lower maximal aerobic capacity. Nevertheless, blood volume and maximal oxygen consumption are higher in postmenopausal women who train in the horizontal position than in sedentary controls.     

Total muscle mitochondrial volume in relation to aerobic capacity of horses and steers

The relationship between maximal oxygen consumption rate ( ) and mitochondrial content of skeletal muscles was examined in horses and steers (n=3 each). Samples of the heart left ventricle, diaphragm,m. vastus medialis, m. semitendinosus, m. cutaneous thoracicus andm. masseter, as well as samples of muscles collected in a whole-body sampling procedure, were analyzed by electron microscopy. per kilogram body mass was 2.7× greater in horses than steers. This higher was in proportion to the higher total volume of mitochondria in horse versus steer muscle when analyzed from the whole-body samples and from the locomotor muscle samples. In non-locomotor muscles, total mitochondrial volume was greater in horses than steers, but not in proportion to their differences in . The of the mitochondria was estimated to be close to 4.5 ml O₂·ml^–1 mitochondria in both species. It is concluded that in a comparison of a highly aerobic to a less aerobic mammalian species of similar body size, a higher oxidative potential may be found in all muscles of the more aerobic species. This greater oxidative potential is achieved by a greater total volume of skeletal muscle mitochondria.     

Hypoxia and CO alter O2 extraction but not peripheral diffusing capacity during maximal aerobic exercise

Purpose

To determine if and how hypoxia combined with elevated carboxyhaemoglobin fraction (F _HbCO) affects peripheral diffusing capacity and O₂ extraction in animals exercising at their maximal aerobic capacity ( $ \dot{V}{\text{O}}_{ 2\hbox{max} } $ ).

Methods

Six goats ran on a treadmill at speeds eliciting $ \dot{V}{\text{O}}_{ 2\hbox{max} } $ while breathing inspired O₂ fractions (F _IO₂) of 0.21 or 0.12 with F _HbCO 0.02 or 0.30. We measured O₂ consumption and arterial and mixed-venous blood variables to assess how hypoxia and elevated F _HbCO individually, and in combination, alter O₂ transport and utilisation.

Results

Peripheral diffusing capacity did not differ among the four gas combinations (P = 0.867), whereas O₂ extraction fraction increased with hypoxia [0.920 ± 0.018 (SD)] and decreased with elevated F _HbCO (0.792 ± 0.038) compared to control (0.897 ± 0.032). Oxygen extraction increases with hypoxia due to the sigmoid relationship between O₂ saturation (SO₂) and O₂ partial pressures (PO₂) affecting low (hypoxia) and high (normoxia) PO₂ differently. Oxygen extraction decreases with elevated F _HbCO because elevated F _HbCO increases haemoglobin (Hb) affinity for O₂ and raises SO₂, especially at very low (mixed-venous) PO₂. Pulmonary gas exchange was impaired only with combined hypoxia and elevated F _HbCO due to hypoxia decreasing alveolar PO₂ and O₂ flux coupled with elevated F _HbCO increasing Hb affinity for O₂ and decreasing the rate of PO₂ increase for a given rise in SO₂.

Conclusion

This study quantifies the mechanisms by which O₂ delivery and peripheral diffusion interact to limit $ \dot{V}{\text{O}}_{ 2\hbox{max} } $ when O₂ delivery is reduced due to breathing hypoxic gas with elevated F _HbCO.     

Relationship between isocapnic buffering and maximal aerobic capacity in athletes

This study was performed to clarify the relationship between isocapnic buffering and maximal aerobic capacity (V˙O_{2 max} ) in athletes. A group of 15 trained athletes aged 21.1 (SD 2.6) years was studied. Incremental treadmill exercise was performed using a modified version of Bruce's protocol for determination of the anaerobic threshold (AT) and the respiratory compensation point (RC). Ventilatory and gas exchange responses were measured with an aeromonitor and expressed per unit of body mass. Heart rate and ratings of perceived exertion were recorded continuously during exercise. The mean V˙O_{2 max} , oxygen uptake (V˙O₂) at AT and RC were 58.2 (SD 5.8)?ml?·?kg^?1?·?min^?1, 28.0 (SD 3.3)?ml?·?kg^?1?·?min^?1 and 52.4 (SD 6.7)?ml?· kg^?1?·?min^?1, respectively. The mean values of AT and RC, expressed as percentages of V˙O_{2 max} , were 48.3 (SD 4.2)% and 90.0 (SD 5.2)%, respectively. The mean range of isocapnic buffering defined as V˙O₂ between AT and RC was 24.4 (SD 4.5) ml?·?kg^?1?·?min^?1, and the mean range of hypocapnic hyperventilation (HHV) defined as V˙O₂ between RC and the end of exercise was 5.8 (SD 3.0)?ml?·?kg^?1?·?min^?1. The V˙O_{2 max} per unit mass was significantly correlated with AT (r?=?0.683, P?V˙O_{2 max} /mass was closely correlated with both the range of isocapnic buffering (r?=?0.803, P?r?=?0.878, P?V˙O_{2 max} per unit mass and the range of HHV (r?=?0.011, NS.). These findings would suggest that the prominence of isocapnic buffering, in addition to the anaerobic threshold, may have been related to V˙O_{2 max} of the athletes. The precise mechanisms underlying this proposed relationship remain to be elucidated.     

Threshold increases in plasma growth hormone in relation to plasma catecholamine and blood lactate concentrations during progressive exercise in endurance-trained athletes

Plasma human growth hormone ([HGH]), adrenaline ([A]), noradrenaline ([NA]) and blood lactate ([La^–]_b) concentrations were measured during progressive, multistage exercise on a cycle ergometer in 12 endurance-trained athletes [aged 32.0 (SEM 2.0) years]. Exercise intensities (3 min each) were increased by 50 W until the subjects felt exhausted. Venous blood samples were taken after each intensity. The [HGH] and catecholamine concentrations increased negligibly during exercise of low to moderate intensities revealing an abrupt rise at the load corresponding to the lactate threshold ([La^–]-T). Close correlations (P < 0.001) were found between [La^–]_b and plasma [HGH] (r = 0.64), [A] (r = 0.71) and [NA] (r = 0.81). The mean threshold exercise intensities for [HGH], [A] and [NA], detected by log-log transformation, [154 (SEM 19) W, 162 (SEM 15) W and 160 (SEM 17) W, respectively] were not significantly different from the [La^–]-T [161 (SEM 12) W]. The results indicated that the threshold rise in plasma [HGH] followed the patterns of plasma catecholamine and blood lactate accumulation during progressive exercise in the endurancetrained athletes.     

Whole-body vibration exercise leads to alterations in muscle blood volume.

Occupationally used high-frequency vibration is supposed to have negative effects on blood flow and muscle strength. Conversely, low-frequency vibration used as a training tool appears to increase muscle strength, but nothing is known about its effects on peripheral circulation. The aim of this investigation was to quantify alterations in muscle blood volume after whole muscle vibration--after exercising on the training device Galileo 2000 (Novotec GmbH, Pforzheim, Germany). Twenty healthy adults performed a 9-min standing test. They stood with both feet on a platform, producing oscillating mechanical vibrations of 26 Hz. Alterations in muscle blood volume of the quadriceps and gastrocnemius muscles were assessed with power Doppler sonography and arterial blood flow of the popliteal artery with a Doppler ultrasound machine. Measurements were performed before and immediately after exercising. Power Doppler indices indicative of muscular blood circulation in the calf and thigh significantly increased after exercise. The mean blood flow velocity in the popliteal artery increased from 6.5 to 13.0 cm x s(-1) and its resistive index was significantly reduced. The results indicate that low-frequency vibration does not have the negative effects on peripheral circulation known from occupational high-frequency vibration.     

Low total haemoglobin mass, blood volume and aerobic capacity in men with type 1 diabetes

Blood O₂ carrying capacity affects aerobic capacity (VO_2max). Patients with type 1 diabetes have a risk for anaemia along with renal impairment, and they often have low VO_2max. We investigated whether total haemoglobin mass (tHb-mass) and blood volume (BV) differ in men with type 1 diabetes (T1D, n = 12) presently without complications and in healthy men (CON, n = 23) (age-, anthropometry-, physical activity-matched), to seek an explanation for low VO_2max. We determined tHb-mass, BV, haemoglobin concentration ([Hb]), and VO_2max in T1D and CON. With similar (mean ± SD) [Hb] (144 vs. 145 g l^?1), T1D had lower tHb-mass (10.1 ± 1.4 vs. 11.0 ± 1.1 g kg^?1, P < 0.05), BV (76.8 ± 9.5 vs. 83.5 ± 8.3 ml kg^?1, P < 0.05) and VO_2max (35.4 ± 4.8 vs. 44.9 ± 7.5 ml kg^?1 min^?1, P < 0.001) than CON. VO_2max correlated with tHb-mass and BV both in T1D (r = 0.71, P < 0.01 and 0.67, P < 0.05, respectively) and CON (r = 0.54, P < 0.01 and 0.66, P < 0.001, respectively), but not with [Hb]. Linear regression slopes were shallower in T1D than CON both between VO_2max and tHb-mass (2.4 and 3.6 ml kg^?1 min^?1 vs. g kg^?1, respectively) and VO_2max and BV (0.3 and 0.6 ml kg^?1 min^?1 vs. g kg^?1, respectively), indicating that T1D were unable to reach similar VO_2max than CON at a given tHb-mass and BV. In conclusion, low tHb-mass and BV partly explained low VO_2max in T1D and may provide early and more sensitive markers of blood O₂ carrying capacity than [Hb] alone.     

Plasma vasopressin,renin activity,and aldosterone responses to maximal exercise in active college females

Summary The effect of maximal treadmill exercise on plasma concentrations of vasopressin (AVP); renin activity (PRA); and aldosterone (ALDO) was studied in nine female college basketball players before and after a 5-month basketball season. Pre-season plasma AVP increased (p<0.05) from a pre-exercise concentration of 3.8±0.5 to 15.8±4.8 pg · ml⁻¹ following exercise. Post-season, the pre-exercise plasma AVP level averaged 1.5±0.5 pg · ml⁻¹ and increased to 16.7±5.9 pg · ml⁻¹ after the exercise test. PRA increased (p<0.05) from a pre-exercise value of 1.6±0.6 to 6.8±1.7 ngAI · ml⁻¹ · hr⁻¹ 5 min after the end of exercise during the pre-season test. In the post-season, the pre-exercise PRA was comparable (2.4±0.6 ngAI · ml⁻¹ · hr⁻¹), as was the elevation found after maximal exercise (8.3±1.9 ngAI · ml⁻¹ · hr⁻¹). Pre-season plasma ALDO increased (p<0.05) from 102.9±30.8 pg · ml⁻¹ in the pre-exercise period to 453.8±54.8 pg · ml⁻¹ after the exercise test. In the post-season the values were 108.9±19.4 and 365.9±64.4 pg · ml⁻¹, respectively. Thus, maximal exercise in females produced significant increases in plasma AVP, renin activity, and ALDO that are comparable to those reported previously for male subjects. Moreover, this response is remarkably reproducible as demonstrated by the results of the two tests performed 5 months apart.     

Central and peripheral cardiovascular adaptations to exercise in endurance-trained children

Stroke volume (SV) response to exercise depends on changes in cardiac filling, intrinsic myocardial contractility and left ventricular afterload. The aim of the present study was to identify whether these variables are influenced by endurance training in pre-pubertal children during a maximal cycle test. SV, cardiac output (Doppler echocardiography), left ventricular dimensions (time-movement echocardiography) as well as arterial pressure and systemic vascular resistances were assessed in 10 child cyclists (VO2max: 58.5 +/- 4.4 mL min-1 kg-1) and 13 untrained children (UTC) (VO2max: 45.9 +/- 6.7 mL min-1 kg-1). All variables were measured at the end of the resting period, during the final minute of each workload and during the last minute of the progressive maximal aerobic test. At rest and during exercise, stroke index was significantly higher in the child cyclists than in UTC. However, the SV patterns were strictly similar for both groups. Moreover, the patterns of diastolic and systolic left ventricular dimensions, and the pattern of systemic vascular resistance of the child cyclists mimicked those of the UTC. SV patterns, as well as their underlying mechanisms, were not altered by endurance training in children. This result implied that the higher maximal SV obtained in child cyclists depended on factors influencing resting SV, such as cardiac hypertrophy, augmented myocardium relaxation properties or expanded blood volume.     

Total haemoglobin mass and red blood cell profile in endurance-trained and non-endurance-trained adolescent athletes

To evaluate differences in total haemoglobin mass (tHb mass) and in red blood cell profile between elite endurance-trained (END) and non-endurance-trained (nEND) male and female adolescent athletes, tHb mass (CO rebreathing) and specific variables of red blood cell profile (haemoglobin concentration, haematocrit, erythrocyte indices) were determined in 59 elite junior athletes (29 END, 30 nEND). We hypothesized that at the age of 15–17 years, regular endurance training might induce a significant increase in tHb mass and changes in red blood cell profile. Therefore, all parameters were again determined after 6, 12 and 18 months in a subset of 27 subjects (17 END, 10 nEND). In END, tHb mass related to body weight was ~15% greater than in nEND (11.2 ± 1.6  vs. 9.7 ± 1.3 g kg⁻¹, P < 0.001), whereas no significant differences were observed for the red blood cell profile. In both groups, tHb mass related to body weight and the variables of red blood cell profile had not changed significantly after 6, 12 and 18 months of regular training. In conclusion, in elite junior athletes, differences in tHb mass between END and nEND were similar, however, smaller compared with previously in adult athletes reported values. At the age of 15–17 years, 18 months of regular training did not induce significant changes in tHb mass beyond alterations explained by physical growth and also variables of red blood cell profile did not change significantly.     

Allometric scaling of maximal metabolic rate in mammals: muscle aerobic capacity as determinant factor

Maximal metabolic rate (MMR) of mammals scales differently from basal metabolic rate (BMR). This is first shown by scrutinizing data reported on exercise-induced Vo2 max in 34 eutherian mammalian species covering a body mass range of 7 g-500 kg. Vo2 max was found to scale with the 0.872 (+/-0.029, 95% confidence limits 0.813-0.932) power of body mass which is significantly different from the 3/4 power reported for basal metabolic rate. The aerobic scope is higher in athletic than non-athletic species, and it is also higher in large than in small species. Integrated structure-function studies on a subset of 11 species (body mass 20 g-450 kg) show that the variation of Vo2 max with body size is tightly associated with the aerobic capacity of the locomotor musculature: the scaling exponents for Vo2 max, the total volume of mitochondria, and the volume of capillaries are nearly identical. The higher Vo2 max of athletic species is tightly linked to proportionally larger mitochondrial and capillary volumes in animals of the same size class. As a result Vo2 max is linearly related to both total mitochondrial and capillary erythrocyte volumes. We conclude that the scaling of maximal metabolic rate is explained by features and mechanisms different from those determining basal metabolic rate.     

Leukocyte telomere length is preserved with aging in endurance exercise-trained adults and related to maximal aerobic capacity

Telomere length (TL), a measure of replicative senescence, decreases with aging, but the factors involved are incompletely understood. To determine if age-associated reductions in TL are related to habitual endurance exercise and maximal aerobic exercise capacity (maximal oxygen consumption, VO₂max), we studied groups of young (18-32 years; n = 15, 7 male) and older (55-72 years; n = 15, 9 male) sedentary and young (n = 10, 7 male) and older (n = 17, 11 male) endurance exercise-trained healthy adults. Leukocyte TL (LTL) was shorter in the older (7059 ± 141 bp) vs. young (8407 ± 218) sedentary adults (P < 0.01). LTL of the older endurance-trained adults (7992 ± 169 bp) was ∼900 bp greater than their sedentary peers (P < 0.01) and was not significantly different (P = 0.12) from young exercise-trained adults (8579 ± 413). LTL was positively related to VO₂max as a result of a significant association in older adults (r = 0.44, P < 0.01). Stepwise multiple regression analysis revealed that VO₂max was the only independent predictor of LTL in the overall group. Our results indicate that LTL is preserved in healthy older adults who perform vigorous aerobic exercise and is positively related to maximal aerobic exercise capacity. This may represent a novel molecular mechanism underlying the “anti-aging” effects of maintaining high aerobic fitness.     

Effects of aerobic exercise on urinary estrogens and progestagens in pre and postmenopausal women

The purpose of this study was to elucidate the effect of 6 months of aerobic exercise on urinary excretion of female steroid hormones in pre and postmenopausal women and to check the basal values of urinary steroid. To this end, 20 premenopausal (age 45.56 ± 4.06 years) and 20 postmenopausal (age 52.27 ± 3.80 years) women, all sedentary, were studied before and after a supervised 6-month exercise training program (at 60–70% of maximal heart rate, 60 min/day, 3 days/week), based on aerobic dance. The exercise included standing on one leg, squatting, walking, and touching their heels. Before and after the program, anthropometric data and VO_2max were measured and urine samples were collected and analyzed by gas chromatography/mass spectrometry (GC/Q-MS). Both, pre and postmenopausal women, improved their VO_2max after the aerobic exercise program. Regarding the urinary steroids, on the one hand, important differences were observed between urinary estrogens and progestagens in pre and postmenopausal women in basal values. Estrone (P < 0.05), pregnanediol (P < 0.01), pregnanetriol (P < 0.05), and estriol (P < 0.01) levels were lower in postmenopausal women than in premenopausal women. On the other hand, the aerobic exercise program did not affect postmenopausal women in the same way as premenopausal women. After the exercise program, no changes in urinary steroid levels were observed in premenopausal women. However, the aerobic exercise program caused an increase in urinary excretion of pregnanediol (P < 0.05) and pregnanetriol (P < 0.05) in postmenopausal women.     

Anaerobic and aerobic urethral flora in healthy females.

We characterized the aerobic and anaerobic urethral flora of five healthy females by performing urethral and midstream urine cultures once weekly for 8 weeks. Aerobic cultures were performed monthly for an additional 3 months. Lactobacillus spp. were isolated from 52 of 57 samples, Staphylococcus epidermidis from 42 of 57, Corynebacterium spp. from 26 of 57, and alpha-hemolytic streptococci from 14 of 57. Two subjects had E. coli serogroup O6 and group B streptococci isolated on five occasions, respectively. Anaerobes were isolated from 32 of 35 urethral urines (91%). Bacteroides melaninogenicus accounted for 46% of these isolates. The anaerobic urethral flora varied slightly from week to week, and a similar anaerobic flora was isolated from the introitus, fourchette, and cutaneous perineum. In addition, anaerobes were isolated from 16 of 18 healthy females who had a urethral urine sample cultured once only, and B. melaninogenicus was the most frequent isolate. Of the 21 B. melaninogenicus isolates identified to subspecies, 14 were subsp. intermedius.     

A comparison of inspiratory muscle fatigue following maximal exercise in moderately trained males and females

Exercise-induced inspiratory muscle fatigue (IMF) has been reported in males but there are few reports of IMF in females. It is not known if a gender difference exists for inspiratory muscle strength following heavy exercise, as is reported in locomotor muscles. Therefore, the relationship between fatigue and subsequent recovery of maximal inspiratory pressure (MIP) following exercise to maximal oxygen consumption was examined in a group of moderately trained males and females. Eighteen males (23±3 years; mean ± SD) and 16 females (23±2 years) completed ten MIP and ten maximal handgrip (HG) strength maneuvers to establish baseline. Post-exercise MIP and HG were assessed successively immediately following a progressive intensity test on a cycle ergometer and at 1, 2, 3, 4, 5, 10, and 15 min. relative to fat-free mass was not statistically different between males (62±7 ml kg^–1 min^–1) and females (60±8 ml kg^–1 min^–1). Males had higher absolute MIP values than females at all time intervals (P<0.05). Immediately following exercise, MIP was significantly reduced in both genders (M=83±16%; F=78±15% of baseline) but HG values were not different than resting values. MIP values remained depressed for both males and females throughout the 15 min (P<0.05). Differences for MIP between males and females were not statistically significant at any measurement time (P>0.05). The findings in this study conclude that IMF, observed immediately following maximal exercise, demonstrated the same pattern of recovery for both genders.     

Changes in blood volume and potassium concentration during exercise in rats.

We measured the changes in circulating blood volume (BV), plasma sodium ([Na+]), and plasma potassium ([K+]) concentrations continuously, during and after exercise in euhydrated and dehydrated rats. Rats ran on a treadmill for 15 min at 600, 900, and 1,200 m/h, and the recovery period lasted 45 min. The BV decreased immediately after onset of exercise, and reached a plateau value in about 5 min of exercise. With 1,200 m/h exercise, a further decrease in blood volume was observed in both groups. The decline in BV was reversely related to the exercise intensity in both groups although the decrease was less in the dehydration group. During and after exercise, there were no significant changes in plasma [Na+] at any speed in either group. Plasma [K+] increased sharply at the onset of exercise and the magnitude of the increase was directly related to the exercise intensity. However, at all three exercise intensities the change in plasma [K+] in the dehydrated group was only about 60% of that measured in the euhydrated control group. These findings suggest that dehydration reduces the wash-out of K+ from the interstitial space of the exercising muscle.