Follow-up studies on glycosylated flavonoids and their complexes with vanadium: their anti-hyperglycemic potential role in diabetes

The present study sought to evaluate the hypoglycemic activities of free glycosylated flavonoids and flavonoid complexes with vanadium(IV), (VO(IV)), on glycemia in experimental diabetic rats. Besides free kaempferol-3,7-O-(alpha)-dirhamnoside and kaempferol-3-neohesperidoside, complexes of these flavonoids with VO(IV) were administered by different routes in order to compare the potency of the compounds as well as the efficacy of insulin or VO(IV) in lowering serum glucose. Wistar rats were made diabetic by alloxan. The glycemia was assessed at different times after the administering of compounds. The equilibrium constants were determined by potentiometric study and two species with VO(IV) are proposed at physiological pH, VOH(2)L(2) for kaempferitrin and VOHL for kaempferol-3-neohesperidoside. The latter exhibited hypoglycemic activity at all times examined with 50 and 100 mg/kg and the former reduced the glycemia from 0 to 6h by i.p. route. The administering of the complexes or 0.0146 mmol/kg VO(IV) resulted in a serum glucose-lowering effect over time in the case of i.p. treatment. A marked hypoglycemic effect was observed for 0.5IU of insulin (67.5%); 0.0146 mmol VO(IV) (16.8%); 0.0294 mmol kaempferitrin-VO(IV) (17.8%) and 0.0286 mmol kaempferol-3-neohesperidoside-VO(IV) (56.0%) at 3h after i.p. treatment when compared with respective zero time in diabetic groups. Kaempferol-3-neohesperidoside-VO(IV) was 2.5 times more effective than VO(IV), twice as effective as the free compound and three times more effective than kaempferitrin-VO(IV). This is of particular interest since kaempferol-3-neohesperidoside appears to represent a suitable ligand for VO(IV) to mimic the efficacy of insulin in lowering serum glucose levels.     

Pregnancy-induced changes in the maximal physiological responses during swimming.

The effect of pregnancy on peak O2 uptake (VO2 peak) during tethered swimming was evaluated in 10 women during their 25th and 35th wk of pregnancy, as well as 9-11 wk postpartum. The swim results were compared with cycle ergometry results obtained at similar times. The results indicated that exercise-induced maximal heart rates remained the same and were similar for the swim and cycle trials, approximately 184 +/- 4 beats/min. Cycling VO2 peak was not affected by pregnancy, averaging 1.94 +/- 0.11 l/min. Postpartum swim VO2 peak was similar to the cycle results; however, during pregnancy it was significantly lower than cycling VO2 peak (P less than 0.05; postpartum, 1.78 +/- 0.14 l/min; 25th wk, 1.64 +/- 0.12; 35th wk, 1.48 +/- 0.11). Hemoglobin concentrations and hematocrits were lower during pregnancy; however, changes in plasma volume (based on hematocrit and hemoglobin) were found to be significantly greater during cycling than during swimming and also greater during pregnancy for both modes of exercise. It was concluded that, unlike cycling, the VO2 peak of pregnant women during swimming is reduced. This reduction in VO2 peak was associated with a decreased peak ventilation (r = 0.864) but was not correlated to exercise-induced hemoconcentration (r = -0.29). Furthermore, pregnancy results in a greater-than-normal exercise-induced hemoconcentration, which may be related to pregnancy-induced changes in capillary dynamics.     

Modeling: optimal marathon performance on the basis of physiological factors

This paper examines current concepts concerning "limiting" factors in human endurance performance by modeling marathon running times on the basis of various combinations of previously reported values of maximal O2 uptake (VO2max), lactate threshold, and running economy in elite distance runners. The current concept is that VO2max sets the upper limit for aerobic metabolism while the blood lactate threshold is related to the fraction of VO2max that can be sustained in competitive events greater than approximately 3,000 m. Running economy then appears to interact with VO2max and blood lactate threshold to determine the actual running speed at lactate threshold, which is generally a speed similar to (or slightly slower than) that sustained by individual runners in the marathon. A variety of combinations of these variables from elite runners results in estimated running times that are significantly faster than the current world record (2:06:50). The fastest time for the marathon predicted by this model is 1:57:58 in a hypothetical subject with a VO2max of 84 ml.kg-1.min-1, a lactate threshold of 85% of VO2max, and exceptional running economy. This analysis suggests that substantial improvements in marathon performance are "physiologically" possible or that current concepts regarding limiting factors in endurance running need additional refinement and empirical testing.     

Energetics of hibernating yellow-bellied marmots (Marmota flaviventris)

Yellow-bellied marmots (Rodentia: Sciuridae) typically hibernate for eight months. This study explored energetic costs of hibernation in young and adults at 10 and 6 degrees C. Age significantly affected the percent time torpid, total and mass-specific VO(2), use of energy during torpor, and daily mass loss at 6 degrees C. Thus young had a higher mass-specific VO(2) during a torpor bout, which was attributed to higher metabolism during deep torpor. Total VO(2) during a bout was higher in young and there were significant temperature/age interactions; young had a higher VO(2) during torpor and deep torpor at 6 degrees C than at 10 degrees C. VO(2) increased at T(E)s below 6 degrees C. Young had a higher daily mass loss than adults at 6 degrees C. Euthermy increased energetic costs 19.3 times over those of torpor and 23.5 times over those of deep torpor. Energy costs are minimized by spending 88.6% of the hibernation period in torpor, by the rapid decline of VO(2) from euthermy to torpor and by allowing T(B) to decline at low T(E). Torpidity results in average energy savings during winter of 83.3% of the costs of maintaining euthermy. Energy savings are greater than those reported for Marmota marmota and M. monax.     

Synergistic induction of ovulation and prostaglandin synthesis in goldfish (Carassius auratus) follicles by sodium orthovanadate and hydrogen peroxide.

The effects of hydrogen peroxide (H2O2) and sodium orthovanadate (Na3VO4) on ovulation and prostaglandin (PG) production were investigated in goldfish (Carassius auratus) follicles. H2O2, at levels that did not stimulate ovulation, significantly increased the ability of Na3VO4 to induce ovulation. The enhancing effect of H2O2 on Na3VO4-induced (10 microM) ovulation was observed over a wide range of concentrations (0.3-19.2 ppm) but was maximal at 1.2-4.8 ppm. The H2O2 effect on ovulation diminished at concentrations greater than 4.8 ppm. Na3VO4 and H2O2 also stimulated prostaglandin E (PGE) and prostaglandin F (PGF) levels in incubates. An interactive effect of the two agents was significant only on PGE production. However, optimal H2O2/Na3VO4 concentrations for the stimulation of PG production were much higher than those for stimulating ovulation. In most incubations, Na3VO4-induced or Na3VO4/H2O2-induced ovulation was not inhibited by the cyclooxygenase inhibitor indomethacin (IM), but was blocked by the lipoxygenase inhibitor nordihydroguaiaretic acid (NDGA). Treatment of an Na3VO4/H2O2 mixture with catalase before the start of incubation totally abolished the enhancing effect of H2O2 on ovulation. This suggests that the enhancing effect of H2O2 on ovulation may not be a result of a chemical metabolite(s) produced by the two agents in mixture but rather is due to some direct effect of H2O2. This may have physiological significance in light of the published effects of H2O2 on various processes known to be involved in ovulation.     

Aerobic performance of female marathon and male ultramarathon athletes.

The aerobic performance of thirteen male ultramarathon and nine female marathon runners were studied in the laboratory and their results were related to their times in events ranging in distance from 5 km to 84.64 km. The mean maximal aerobic power output (VO2 max) of the men was 72.5 ml/kg . min compared with 58.2 ml/kg . min (p less than 0.001) in the women but the O2 cost (VO2) for a given speed or distance of running was the same in both sexes. The 5 km time of the male athletes was closely related to their VO2 max (r = -0.85) during uphill running but was independent of relative power output (%VO2 max). However, with increasing distance the association of VO2 max with male athletic performance diminished (but nevertheless remained significant even at 84.64 km), and the relationship between %VO2 max and time increased. Thus, using multiple regression analysis of the form: 42.2 km (marathon) time (h) = 7.445 - 0.0338 VO2 max (ml/kg . min) - 0.0303% VO2 max (r = 0.993) and 84.64 km (London-Brighton) time (h) = 16.998 - 0.0735 VO2 max (ml/kg . min) - 0.0844% VO2 max (r = 0.996) approximately 98% of the total variance of performance times could be accounted for in the marathon and ultramarathon events. This suggests that other factors such as footwear, clothing, and running technique (Costill, 1972) play a relatively minor role in this group of male distance runners. In the female athletes the intermediate times were not available and they did not compete beyond 42.2 km (marathon) distance but for this event a similar association though less in magnitude was found with VO2 max (r = -0.43) and %VO2 max (= -0.49). The male athletes were able to sustain 82% VO2 max (range 80--87%) in 42.2 km and 67% VO2 max (range 53--76%) in 84.64 km event. The comparable figure for the firls in the marathon was 79% VO2 max (ranges 68--86%). Our data suggests that success at the marathon and ultramarathon distances is crucially and (possibly) solely dependent on the development and utilisation of a large VO2 max.     

Oxygen transport during exercise in large mammals. I. Adaptive variation in oxygen demand

This study investigated mechanisms used by horses and steers to increase O2 uptake and delivery (VO2) from resting to maximal rates and identified the mechanisms that enable horses to achieve higher maximal rates of O2 consumption (VO2max) than steers. VO2 and circulatory variables were measured while Standardbred trotting horses and steers (450-kg body mass) stood quietly and ran on a treadmill at speeds up to those eliciting VO2max. As VO2 increased in both species, heart rate and circulating hemoglobin (Hb) concentration increased, thereby increasing O2 delivery by the circulation, while cardiac stroke volume remained unchanged. At VO2max arterial PCO2 increased from its resting value in horses but was unchanged in steers, and arterial PO2 decreased in both species. Although the horses hypoventilated and were hypoxemic at VO2max, no significant decrease in arterial Hb saturation occurred. VO2max of the horses was 2.6 times higher than that of the steers and was associated with a 100% larger cardiac output, 100% larger stroke volume, and 40% higher Hb concentration, whereas heart rates at VO2max were identical in the two species. The higher cardiac output of the horses at VO2max resulted from a 1.2-fold higher mean arterial pressure and 1.6-fold lower peripheral tissue resistance (associated with a larger skeletal muscle capillary bed). Both the magnitude of the difference in VO2max between horses and steers and the mechanisms used to achieve it are the same as observed in smaller pairs of mammalian species with large variation in aerobic capacity.     

Evidence for liver as the major site of the diet-induced thermogenesis of rats fed a "cafeteria" diet

The resting metabolic rates (VO2) of rats fed chow (CH) or a "cafeteria" (CAF) diet of highly palatable human foods were measured at thermoneutrality (28 degrees C) before and shortly after two-thirds hepatectomy or sham operation, and again after administration of propranolol (5 mg/kg). CAF rats initially had a 17% and 1.2 mL/min higher mean resting VO2 than CH rats, a difference usually considered to represent the diet-induced thermogenesis (DIT) that CAF rats develop during overconsumption of the diet. Sham operation did not significantly affect resting VO2 in either diet group. Two-thirds hepatectomy decreased VO2 by about 1.0 mL/min more (125% more) in CAF rats than in CH rats, from which it may be estimated that the CAF rats initially had a liver VO2 about 1.6 mL/min higher than that of the CH rats, a difference more than sufficient to fully account for their apparent DIT. Propranolol did not significantly affect the VO2 of CH rats. It reduced the VO2 of sham-operated CAF rats by 0.94 +/- 0.08 mL/min (12%), but had a significantly smaller effect (delta VO2 = -0.50 +/- 0.05 mL/min) in partially hepatectomized CAF rats. This difference suggests that about 70% of the propranolol-inhibitable fraction of the elevated VO2 of the CAF rats, presumably a measure of sympathetically mediated DIT, resided in the liver. This study thus points to the liver as the major (70-100%) effector of the DIT of CAF rats.     

Quantitative determination of the rate of superoxide radical formation in mitochondrial membranes by electron paramagnetic resonance

The reaction of hydroxylamine (1-hydroxy-2,2,6,6-tetramethyl-4-oxopiperidine) with O2-. resulting in the stable nitroxyl radical formation recorded by ESR-technique was applied to estimate quantitatively the rate of O2-. superoxide radical generation (VO2.-) by submitochondrial particles (SMP) of liver (of mice and rats). The VO2.- dependence on concentrations of NADH, succinate and protein of SMP was established. The method allows detecting VO2.- greater than 0.05 nmol.min-1.ml-1. It has been shown that in the NADH-dependent site of the chain VO2.- is 3-4 times that in the succinate-dependent site. In the presence of rhotenone and antimycin A VO2.- increases by 30-35%, while cyanide retards VO2.- by about 30%. The data comparison with regard to VO2.- and O2 absorption rate polarographically determined has indicated that about 2% of the absorbed O2 is consumed to form O2-.     

Determination of the surface area and viscosity of membranes in T- and B-lymphocytes by means of fluorescent probes

The surface area of lymphocyte membranes was measured by registering F?rster's energy transfer on fluorescent probes. Pyrene served as donor, 4-(n-hydroxystyryl)-N-tetradecylpiridinium (HSP) was the acceptor. The surface area B-lymphocyte membranes was shown to be 1,2 times larger than that of T-lymphocytes. The mean value of lymphocyte membranes viscosity was measured using the excimerization effect of pyrene. This value was the same in all the cells investigated Fluorescence of the probe 3-methoxybenzanthrone (MBA) was 2-2.5 times higher in B-lymphocytes and was not proportional to the surface area of T- and B-cells membranes. MBA fluorescence may imply some differences in physical structures of these cells which are not connected with the viscosity of their membrane lipid phase.     

Effects of training on the physiological responses to one- and two-leg work.

The effects of training resulting from one-leg exercise on a stationary bicycle ergometer have been studied. Seven subjects were habituated to one- and two-leg progressive exercise tests on 11 successive days and were then trained for 60 min-day-1 (30 min each leg) 3 times per wk for 5-6 wk at approximately 80% of their one-leg VO2 max. VE max increased (P less than 0.05) by approximately 14 1-min-1 and VO2 max by approximately 0.34 1-min-1 (+14%; P less than 0.05) in one-leg exercise. This latter increase was not, however, reflected in the two-leg VO2 max which only increased 145 ml-min-1 (4.7%). It was concluded that training is specific and in one-leg work the phenomenon is mainly peripheral in origin, but in two-leg work the limitation to maximal exercise is still provided by the capacity of the central cardiovascular system to transport oxygen to a given effective muscle mass.     

Hydrophobic carriers of vanadyl ions augment the insulinomimetic actions of vanadyl ions in rat adipocytes.

A novel family of vanadyl ion (VO2+, oxidation state +4) carriers is introduced. These carriers possess C2 symmetry, utilize two hydroxamate groups as ion binding sites, and optionally possess asymmetric carbons. Binding efficiencies and hydrophobicities are regulated by the use of a modular assembly. When applied to rat adipocytes, these carriers augment the potency of vanadyl ions to stimulate glucose metabolism. The complexes shift the dose-response curve to the left. Also, the maximal effect of vanadyl ions which is in the order of 20-30% of that of insulin is shifted toward maximal (100-115%) stimulation. Among several chelators studied, the order of synergistic potency was RL-252 greater than or equal to RL-262 greater than 1367. RL-239, RL-280, and RL-261 had smaller effects, whereas RL-282 had a negligible effect. The synergistic action of RL-252 (and other chelators as well) on VO2+ was already observed at a molar ratio of 1:0.01 of VO2+ to RL-252, respectively, and maximal augmentation occurred at a molar ratio of 1:0.1. The superiority of the hydrophobic chelators relative to the hydrophilic ones, together with the low molar ratio of chelator to VO2+ to achieve maximal effect, strongly suggests that these chelators act as vanadyl ionophores. This notion was confirmed by carrier-facilitated extraction of VO2+ from water into CHCl3 with the following order of decreasing efficacy: RL-262 greater than RL-252 greater than 1367 greater than RL-261. The chelators' potentiating effect may therefore be related to facilitated transport of VO2+ ions into the cells' interiors.(ABSTRACT TRUNCATED AT 250 WORDS)     

Oxygen transport during exercise in large mammals. II. Oxygen uptake by the pulmonary gas exchanger

Because the maximal rate of O2 consumption (VO2max) of the horse is 2.6 times larger than that of steers of equal size, we wondered whether their pulmonary gas exchanger is proportionately larger. Three Standardbred racehorses [body mass (Mb) = 447 kg] and three domestic steers (Mb = 474 kg) whose cardiovascular function at VO2max had been thoroughly studied (Jones et al. J. Appl. Physiol. 67: 862-870, 1989) were used to study their lungs by morphometry. The basic morphometric parameters were similar in both species. The nearly 2 times larger lung volumes of the horses caused the gas exchange surfaces and capillary blood volume to be 1.6 to 1.8 times larger. Morphometric pulmonary diffusing capacity was 2 times larger in the horse than in the steer; the 2.6-fold greater rate of O2 uptake thus required the alveolar-capillary PO2 difference to be 1.3 times larger in the horse than in the steer. Combining physiological and morphometric data, we calculated capillary transit time at VO2max to be 0.4-0.5 s. Bohr integration showed capillary blood to be equilibrated with alveolar air after 75 and 58% of transit time in horses and steers, respectively; horses maintain a smaller degree of redundancy in their pulmonary gas exchanger.     

The effect of exercise intensity and duration on the oxygen deficit and excess post-exercise oxygen consumption

Nine males with mean maximal oxygen consumption (VO2max) = 63.0 ml.kg-1.min-1, SD 5.7 and mean body fat = 10.6%, SD 3.1 each completed nine counterbalanced treatments comprising 20, 50 and 80 min of treadmill exercise at 30, 50 and 70% VO2max. The O2 deficit, 8 h excess post-exercise oxygen consumption (EPOC) and EPOC:O2 deficit ratio were calculated for all subjects relative to mean values obtained from 2 control days each lasting 9.3 h. The O2 deficit, which was essentially independent of exercise duration, increased significantly (P less than 0.05) with intensity such that the overall mean values for the three 30%, 50% and 70% VO2max workloads were 0.83, 1.89 and 3.09 l, respectively. While there were no significant differences (P greater than 0.05) between the three EPOCs after walking at 30% VO2max for 20 (1.01 l), 50 (1.43 l) and 80 min (1.04 l), respectively, the EPOC thereafter increased (P less than 0.05) with both intensity and duration such that the increments were much greater for the three 70% VO2max workloads (EPOC: 20 min = 5.68 l; 50 min = 10.04 l; 80 min = 14.59 l) than for the three 50% VO2max workloads (EPOC: 20 min = 3.14 l; 50 min = 5.19 l; 80 min = 6.10 l). An analysis of variance indicated that exercise intensity was the major determinant of the EPOC since it explained five times more of the EPOC variance than either exercise duration or the intensity times duration interaction. The mean EPOC:O2 deficit ratio ranged from 0.8 to 4.5 and generally increased with both exercise intensity and duration.(ABSTRACT TRUNCATED AT 250 WORDS)     

The effects of dietary manipulation upon the respiratory exchange ratio as a predictor of maximum oxygen uptake during fixed term maximal incremental exercise in man

This study examined the effects of dietary manipulation upon the respiratory exchange ratio (R = VCO2/VO2) as a predictor of maximum oxygen uptake (VO2max). Seven healthy males performed fixed term maximal incremental treadmill exercise after an overnight fast on three separate occasions. The first test took place after the subjects had consumed their normal mixed diet (45 +/- 5% carbohydrate (CHO] for a period of three days. This test protocol was then repeated after three days of a low CHO diet (3 +/- 2% CHO), and again after three days of a high CHO diet (61 +/- 5% CHO). Respiratory gases were continuously monitored during each test using an on-line system. No significant changes in mean exercise oxygen uptake (VO2), VO2max or maximum functional heart rate (FHRmax) were found between tests. Mean exercise carbon dioxide output (VCO2) and R were significantly lower than normal after the low CHO diet (both p less than 0.001) and significantly higher than normal after the high CHO diet (both p less than 0.05). Moreover, compared with the normal CHO diet, the R-time relationship during exercise was at all times significantly (p less than 0.001) shifted to the right after the low CHO diet, and shifted to the left, being significantly so (p less than 0.05) over the final 5 min of exercise, after the high CHO diet.(ABSTRACT TRUNCATED AT 250 WORDS)     

In vitro study of the insulin-like action of vanadyl-pyrone and -pyridinone complexes with a VO(O4) coordination mode

The insulin-like action of a novel class of potential insulin-mimetic complexes was investigated in terms of free fatty acid (FFA) release from isolated rat adipocytes. Vanadyl complexes such as VO(ema)2 [(bis(2-ethyl-3-hydroxy-4-pyrone)VO], VO(mpp)2 [bis (3-hydroxy-2-methyl-4(1H)-pyridinone)VO], VO(dmpp)2 [bis(1,2-dimethyl-3-hydroxy-4(1H)-pyridinone)VO] and VO(empp)2 [bis(2-ethyl-3-hydroxy-1-methyl-4(1H)-pyridinone)VO] were tested together with vanadyl sulfate for comparison. The inhibitory effect of the vanadium complexes on FFA release, from rat adipocytes treated with epinephrine, is dependent on concentration and for that reason the results are reported in terms of the IC50 value, the 50% inhibition concentration. The results show that all the complexes have an inhibitory effect on FFA release and that two pyridinone complexes, VO(mpp)2 and VO(empp)2, have a significantly better insulin-mimetic activity than that of vanadyl sulfate.     

Relation between maximal oxygen consumption and the record time in the 1500-meter run. Analysis of Lloyd's model

Lloyd's equation (Lloyd, 1967 b) has been applied to the calculation of record time in the 1 500 meters foot race from VO2 max. Twenty-eight healthy male subjects participated in this investigation. Record times decrease with increasing VO2 max. The theoretical curve plotted from Lloyd's equation is consistent with this trend. Moreover, the relationship between calculated record times (TRc) and measured record times (TRm) is highly significant (TRc = 74.3 + 0.7 TRm; r = 0.883; P less than 0.001). These results validate Lloyd's equation and hypothesis.     

Exercise intensity: effect on postexercise O2 uptake in trained and untrained women

Despite many reports of long-lasting elevation of metabolism after exercise, little is known regarding the effects of exercise intensity and duration on this phenomenon. This study examined the effect of a constant duration (30 min) of cycle ergometer exercise at varied intensity levels [50 and 70% of maximal O2 consumption (VO2max)] on 3-h recovery of oxygen uptake (VO2). VO2 and respiratory exchange ratios were measured by open-circuit spirometry in five trained female cyclists (age 25 +/- 1.7 yr) and five untrained females (age 27 +/- 0.8 yr). Postexercise VO2 measured at intervals for 3 h after exercise was greater (P less than 0.01) after exercise at 50% VO2max in trained (0.40 +/- 0.01 l/min) and untrained subjects (0.39 +/- 0.01 l/min) than after 70% VO2max in (0.31 +/- 0.02 l/min) and untrained subjects (0.29 +/- 0.02 l/min). The lower respiratory exchange ratio values (P less than 0.01) after 50% VO2max in trained (0.78 +/- 0.01) and untrained subjects (0.80 +/- 0.01) compared with 70% VO2max in trained (0.81 +/- 0.01) and untrained subjects (0.83 +/- 0.01) suggest that an increase in fat metabolism may be implicated in the long-term elevation of metabolism after exercise. This was supported by the greater estimated fatty acid oxidation (P less than 0.05) after 50% VO2max in trained (147 +/- 4 mg/min) and untrained subjects (133 +/- 9 mg/min) compared with 70% VO2max in trained (101 +/- 6 mg/min) and untrained subjects (85 +/- 7 mg/min).     

Effect of wearing clothes on oxygen uptake and ratings of perceived exertion while swimming

For a comparative study between swimming in swimwear (control-sw) and swimming in clothes (clothes-sw), oxygen uptake (VO2) and ratings of perceived exertion (RPE) were measured. The subjects were six male members of a university swimming team. Three swimming strokes--the breaststroke, the front crawl stroke and the elementary backstroke--were applied. With regards to clothes-sw, swimmers wore T-shirts, sportswear (shirt and pants) over swimwear and running shoes. In both cases of control-sw and clothes-sw, the VO2 was increased exponentially with increased swimming speed. The VO2 of the subjects during the clothed tests did not exceed 1.4 times of that in the case of control-sw at swimming speeds below 0.3 m/s. As swimming speeds increased, VO2 difference in both cases increased. Consequently, VO2 in the clothed tests was equal to 1.5-1.6 times and 1.5-1.8 times of that in the swimwear tests at speeds of 0.5 and 0.7 m/s, respectively. At speeds below 0.6 m/s in clothes-sw, the breaststroke showed lower VO2 than the front crawl stroke, and the elementary backstroke showed higher VO2 than the other two swimming strokes. RPE increased linearly with %peak VO2. In addition, any RPE differences among the three swimming strokes were not shown in the control-sw tests. At an exercise intensity above 60 %peak VO2, clothed swimmers showed slightly higher RPE in the front crawl stroke compared to that in the two other swimming strokes.     

Familial aggregation of VO(2max) response to exercise training: results from the HERITAGE Family Study.

The aim of this study was to test the hypothesis that individual differences in the response of maximal O(2) uptake (VO(2max)) to a standardized training program are characterized by familial aggregation. A total of 481 sedentary adult Caucasians from 98 two-generation families was exercise trained for 20 wk and was tested for VO(2max) on a cycle ergometer twice before and twice after the training program. The mean increase in VO(2max) reached approximately 400 ml/min, but there was considerable heterogeneity in responsiveness, with some individuals experiencing little or no gain, whereas others gained >1.0 l/min. An ANOVA revealed that there was 2.5 times more variance between families than within families in the VO(2max) response variance. With the use of a model-fitting procedure, the most parsimonious models yielded a maximal heritability estimate of 47% for the VO(2max) response, which was adjusted for age and sex with a maternal transmission of 28% in one of the models. We conclude that the trainability of VO(2max) is highly familial and includes a significant genetic component.