Glucose tolerance,plasma lipoproteins and tissue lipoprotein lipase activities in body builders

Summary Oral glucose tolerance, insulin binding to erythrocyte receptors, serum lipids, and lipoproteins, and lipoprotein lipase activities of adipose tissue and skeletal muscle were measured in nine body builders (relative body weight (RBW) 118±4%), eight weight-matched (RBW 120±5%) and seven normal-weight controls (RBW 111±3%). The body builders had 50% higher relative muscle mass of body weight (% muscle) and 50% smaller relative body fat content (% fat) than the two other groups (P<0.005). Maximal aerobic power was comparable in the three groups. In the oral glucose tolerance test (OGTT), blood glucose levels, and plasma insulin levels were lower (P<0.05) in the body builders than in weight-matched controls. Insulin binding to erythrocytes was similar in each group. On the basis of multiple linear regression analysis, 87% of the variation in plasma insulin response could be explained by body composition (% muscle and % fat) and .Plasma total cholesterol, low-density lipoprotein (LDL) cholesterol, and very low-density lipoprotein (VLDL) triglyceride concentrations were significantly lower in the body builders than in weight-matched controls. In comparison with the normal-weight group, the body builders had a lower total cholesterol level. High density lipoprotein (HDL) cholesterol, its subfractions (HDL₂ and HDL₃ cholesterol) and lipoprotein lipase (LPL) activities of adipose tissue and skeletal muscle were comparable in all three groups. Partial correlation analysis showed a positive relationship between plasma total triglyceride, total cholesterol and LDL cholesterol on the other hand and the % fat on the other.The results indicate that a shift in body composition from the adipose to the muscular type is associated with 1) lower glucose and insulin levels during the OGTT and 2) decrease in total and VLDL triglyceride and in total and LDL cholesterol levels but unchanged HDL cholesterol level. Thus, body builders are characterized by some metabolic features which decrease the risk of coronary heart disease. In contrast to aerobic training, body building does not influence HDL or its subfractions.     

Effect of intermittent hypoxia on oxygen uptake during submaximal exercise in endurance athletes

The purpose of the present study was to clarify the following: (1) whether steady state oxygen uptake (O₂) during exercise decreases after short-term intermittent hypoxia during a resting state in trained athletes and (2) whether the change in O₂ during submaximal exercise is correlated to the change in endurance performance after intermittent hypoxia. Fifteen trained male endurance runners volunteered to participate in this study. Each subject was assigned to either a hypoxic group (n=8) or a control group (n=7). The hypoxic group spent 3 h per day for 14 consecutive days in normobaric hypoxia [12.3 (0.2)% inspired oxygen]. The maximal and submaximal exercise tests, a 3,000-m time trial, and resting hematology assessments at sea level were conducted before and after intermittent normobaric hypoxia. The athletes in both groups continued their normal training in normoxia throughout the experiment. O₂ during submaximal exercise in the hypoxic group decreased significantly (P<0.05) following intermittent hypoxia. In the hypoxic group, the 3,000-m running time tended to improve (P=0.06) after intermittent hypoxia, but not in the control group. Neither peak O₂ nor resting hematological parameters were changed in either group. There were significant (P<0.05) relationships between the change in the 3,000-m running time and the change in O₂ during submaximal exercise after intermittent hypoxia. The results from the present study suggest that the enhanced running economy resulting from intermittent hypoxia could, in part, contribute to improved endurance performance in trained athletes.     

Variability in the response of different male subjects to the effect of marathon running on the increase in plasma high density lipoprotein

Summary The acute effects of running a 42.2 km marathon race on the concentration and composition of the plasma lipoproteins were studied in 56 men of varying fitness, training experience, age and physical characteristics. There was no change in the mean concentration of total serum cholesterol, but a 10.9% increase (P<0.001) in the mean concentrations of high-density lipoprotein cholesterol (HDL-TC), representing an 11.1% increase (P<0.001) in the cholesteryl ester (CE) and 9.9% increase (P<0.001) in the unesterified cholesterol (UC) moieties of HDL. The ratio of total serum cholesterol to HDL-TC decreased significantly (P<0.001) during the exercise. Changes in lipoprotein concentrations during the marathon varied considerably between individual subjects, with a small proportion of subjects exhibiting relatively large increases or decreases in HDL-TC, HDL-CE and HDL-UC. Small sub-populations of runners were identified who showed abnormally large decreases in HDL-UC and abnormally small increases in HDL-CE relative to HDL-UC. A correlation (P<0.05) was found between the average weekly mileage of training and the increase in HDL-TC, whilst faster runners (finishing time <3 h; n=13) had a significantly greater (P<0.02) increase in HDL-TC than slower runners (>4 h; n=14). The observed alterations in the lipoproteins are consistent with increased rates of lipolysis of triacylglycerol-rich lipoproteins and of cholesterol esterification during the marathon and suggest that the effect of exercise on the activities of the enzymes that catalyse these processes may vary considerably between different subjects and may be modulated by training and other factors.Abbreviations VLDL very low density lipoproteins - LDL low density lipoproteins - HDL high density lipoproteins - HDL-TC high-density lipoprotein-total cholesterol - HDL-CE cholesteryl ester - HDL-UC unesterified cholesterol     

Relationship of high-density lipoprotein subfractions and cholesteryl ester transfer protein in plasma to carotid artery wall thickness

High plasma concentrations of high-density lipoprotein (HDL) cholesterol are a powerful indicator of low vascular risk. By decreasing HDL cholesterol, cholesteryl ester transfer protein (CETP) could perhaps constitute an atherogenic protein. We measured HDL cholesterol and HDL subfractions and quantified CETP mass in fasting plasma in 21 asymptomatic probands, and related these variables to the mean intima media thickness of the extracranial carotid arteries. HDL₂ cholesterol, the less dense HDL subfraction, was inversely related to carotid wall thickness (r=–0.378; P<0.05), and CETP was directly related to carotid wall thickness (r=0.436; P<0.05). In plasma CETP is associated mostly with the HDL₃ subfraction. We therefore calculated from our measurements the relative CETP content of HDL₃, i.e., CETP/HDL₃ cholesterol. This ratio was correlated with carotid wall thickness stronger than any other variable measured (r=0.718, P<0.001). We conclude that variation in HDL subfractions and CETP may be more closely associated with carotid intima media thickness than the accepted strong risk factor of HDL cholesterol.Abbreviations HDL High-density lipoprotein - CETP Cholesteryl ester transfer protein - LDL Low-density lipoprotein     

Control of the rate of phosphocreatine resynthesis after exercise in trained and untrained human quadriceps muscles

We examined the effect of differences in exercise intensity on the time constant (t _c) of phosphocreatine (PCr) resynthesis after exercise and the relationships betweent _c and maximal oxygen uptake (VO_2max) in endurance-trained runners (n = 5) and untrained controls (n = 7) (average VO_2max = 66.2 and 52.0 ml · min^–1 · kg^–1, respectively). To measure the metabolism of the quadriceps muscle using phosphorus nuclear magnetic resonance spectroscopy, we developed a device which allowed knee extension exercise inside a magnet. All the subjects performed four types of exercise: light, moderate, severe and exhausting. The end-exercise PCr: [PCr + inorganic phosphate (P_i)] ratio decreased significantly with the increase in the exercise intensity (P < 0.01). Although there was little difference in the end-exercise pH, adenosine diphosphate concentration ([ADP]) and the lowest intracellular pH during recovery between light and moderate exercise, significant changes were found at the two higher intensities (P < 0.01). These changes for runners were smaller than those for the controls (P < 0.05). The _c remained constant after light and moderate exercise and then lengthened in proportion to the increase in intensity (P < 0.05). The runners had a lowert _c at the same PCr and pH than the controls, particularly at the higher intensity (P < 0.05). There was a significant correlation betweent _c and [ADP] in light exercise and betweent _c and both end-exercise PCr and pH in severe and exhausting exercise (P < 0.05). The threshold of changes in pH andt _c was a PCr: (PCr + P_i) ratio of 0.5. There was a significant negative correlation between the VO_2max andt _c after all levels of exercise (P<0.05).However, in the controls a significant correlation was found in only light and moderate exercise (P < 0.05). These findings suggest the validity of the use oft _c at an end-exercise PCr:(PCr + P_i) ratio of more than 0.5 as a stable index of muscle oxidative capacity and the correlation between local and general aerobic capacity. Moreover, endurance-trained runners are characterized by the faster PCr resynthesis at the same PCr and intracellular pH.     

Impact of hormone replacement therapy on postprandial lipoproteins and lipoprotein(a) in normolipidemic postmenopausal women

In 43 normolipidemic postmenopausal women we studied fasting and postprandial (oral fat load with 50 g fat per square meter; blood sampling for 5 h) lipoprotein components and lipoprotein(a) levels before and with the administration of conjugated equine estrogens opposed by medrogestone (on days 11–21). Data was compared intraindividually; the second testing was performed during the last 5 days of the combined estrogen/progestogen phase of the third cycle. Fasting low-density lipoprotein (LDL) and total cholesterol concentrations decreased significantly; high-density lipoprotein (HDL) cholesterol, including subfractions HDL₂ and HDL₃, was not changed. Fasting triglyceride concentrations increased. All lipoprotein fractions measured showed a postprandial elevation with the exception of chylomicron cholesterol concentrations. There was a significant effect of hormone replacement therapy on the postprandial course of total cholesterol (decrease; P < 0.001), VLDL cholesterol (increase; P = 0.025), and the triglyceride proportion in the LDL plus HDL fraction (increase; P < 0.001). With hormone replacement therapy the postprandial curve of total triglycerides was increased only 1 h after the fat load while chylomicron triglyceride concentrations were lowered after 5 h. VLDL triglycerides were not influenced. In all patients with lipoprotein(a) levels above 10 mg/dl, this parameter decreased (about 25%). Although increasing fasting triglyceride concentrations, hormone replacement therapy does not bring about an exaggerated postprandial increase in triglycerides. Postprandial chylomicron clearance is evidently promoted. Hormone replacement therapy leads to a small increase in triglycerides in the LDL plus HDL fraction by inhibiting hepatic lipase activity. Moreover, the decrease in lipoprotein(a) levels may contribute to the antiatherosclerotic effect.Abbreviations: CEE conjugated equine estrogens - HDL high-density lipoproteins - HRT hormone replacement therapy - LDL low-density lipoproteins - TG triglycerides - VLDL very low density lipoproteins Correspondence to: U. Julius     

Effects of exercise with varying energy expenditure on high-density lipoprotein-cholesterol

To investigate the effect of varying energy expenditure on acute high-density lipoprotein-cholesterol (HDL-C) changes, 12 healthy endurance-trained men completed three- counterbalanced running trials at different energy expenditures: trial 1, 1690.3 (24.4) kJ [mean (SD)]; trial 2, 2529.1 (24.0) kJ; trial 3, 3384.3 (36.6) kJ, with exercise intensity at 75% of maximal oxygen consumption. For each trial, blood samples were collected at 24 h pre-exercise (24 h Pre), immediately post-exercise, 1 h post-exercise, 6 h post-exercise (6 h PE), and 24 h post-exercise (24 h PE). Plasma samples were analyzed for HDL-C, HDL₂-C and HDL₃-C subfractions, and triglycerides (TG). In addition, post-heparin plasma samples were analyzed at 24 h Pre, 6 h PE and 24 h PE for lipoprotein lipase activity (LPLA) and hepatic triglyceride lipase activity. All samples were corrected for plasma volume changes and compared to 24 h Pre (baseline). When trials were combined, an increase (P < 0.05) in HDL-C was observed 24 h PE, via an increase (P < 0.05) in HDL₃-C. An increase (P < 0.05) in LPLA and decrease (P < 0.05) in TG at 24 h PE is suggested to be responsible for the increase in HDL₃-C. In conclusion, no difference in HDL-C was observed among trials. However, when trials were combined, an increase in HDL-C was observed, suggesting that an energy expenditure of no greater than 3384 J is needed to promote favorable changes in HDL-C.     

Metabolic consequences of repeated exercise in long distance runners

Summary To assess the rates of change in muscle metabolites such as phosphocreatine (PCr) and inorganic phosphate (P_i) during repeated exercise sessions with rest periods, 31-phosphorus nuclear magnetic resonance spectroscopy was used for continuous and noninvasive measurements. Five long-distance runners and six healthy male subjects as controls performed a 2-min femoral flexion exercise at 20 kg · m · min^–1 in a 2.1 T superconducting magnet with a 67-cm bore; they repeated this exercise four times with a 2-min rest period. At the beginning of exercise, PCr decreased exponentially; at the end, it increased. During exercise and in the early phase of the recovery in every exercise session, the PCr values were significantly higher in the long-distance runners than in the control subjects (P<0.05). The Pi increases and decreases involved with exercise also revealed exponential changes. The P_i values did not significantly differ during exercise; however, P_i recovery was faster in the long-distance runners than in the control subjects (P < 0.05). The P_i: PCr ratio during exercise increased linearly with exercise; and P_i:PCr during recovery was smaller in the long-distance runners than in the control subjects (P < 0.05). In conclusion, the long-distance runners revealed faster PCr and P_i kinetics after exercise and a smaller P_i:PCr during exercise than did the control subjects. It is suggested that these results were attributable to a greater oxidative capacity of muscles in the long-distance runners.     

Apolipoprotein(a) phenotypes and lipoprotein(a) concentrations in patients with hyperthyroidism

Lipoprotein(a) [Lp(a)] is a low-density lipoprotein (LDL) particle in which apolipoprotein B-100 (apoB) is attached to a glycoprotein called apolipoprotein(a) [apo(a)]. Apo(a) has several genetically determined phenotypes differing in molecular weight, to which Lp(a) concentrations in plasma are inversely correlated. High plasma levels of Lp(a) are associated with atherosclerotic diseases. It is therefore of interest to study whether factors other than the apo(a) gene locus are involved in the regulation of Lp(a) concentrations. We measured plasma concentrations of Lp(a) and other lipoproteins and determined apo(a) phenotypes in 31 patients with hyperthyroidism, before and after the patients had become euthyroid by treatment. The mean concentration of LDL cholesterol rose from 2.67 to 3.88 mmol/l (P<0.01), apoB rose from 0.79 to 1.03 g/l (P<0.01), and the median Lp(a) concentration increased from 9.74 to 18.97 mg/dl (P<0.01) on treatment. Lp(a) concentrations were inversely associated to the size of the apo(a) molecule both before (P< 0.01) and after treatment (P<0.01). The increase in Lp(a) was significant patients with high molecular weight apo(a) phenotypes (n = 9; P<0.01) and in patients with low molecular weight apo(a) phenotypes (n=16; P< 0.01), but not in those with apo(a) null types (n = 6; P = 0.5). The low levels LDL cholesterol and apoB in untreated hyperthyroidism may result from increased LDL receptor activity. The increase in Lp(a) levels were not correlated with the increase in LDL cholesterol or apoB. Most other clinical evidence indicates that the LDL receptor is not important in Lp(a) catabolism, and we suggest that the low Lp(a) levels seen in thyroid hormone excess are caused by an inhibition of Lp(a) synthesis.Abbreviations Lp(a) lipoprotein(a) - apo(a) apolipoprotein(a) - apoB apolipoprotein B-100 - LDL low-density lipoprotein - HDL high-density lipoprotein - TG triglycerides - T ₄ thyroxine - T ₃ triiodothyronine - TSH thyrotropin     

Changes in lipid profile variables in response to submaximal and maximal exercise in trained cyclists

This study examined the effect of prolonged submaximal exercise followed by a self-paced maximal performance test on cholesterol (T-Chol), triglycerides (TG), and high-density lipoprotein cholesterol (HDLC). Nine trained male athletes cycled at 70% of maximal oxygen consumption for 60 min, followed by a selfpaced maximal ride for 10 min. Venous blood samples were obtained at rest, at 30 and 60 min during submaximal exercise, and immediately after the performance test. Lactic acid, haematocrit (Hct), haemoglobin (Hb), T-Chol and TG were measured in the blood, while plasma was assayed for HDL-C. Plasma volume changes in response to exercise were calculated from Hct and Hb values and all lipid measurements were corrected accordingly. In order to ascertain the repeatability of lipid responses to exercise, all subjects were re-tested under identical testing conditions and experimental protocols. When data obtained during the two exercise trials were analysed by two-way ANOVA no significant differences (P > 0.05) between tests were observed. Consequently the data obtained during the two testing trials were pooled and analysed by one-way ANOVA. Blood lactic acid increased non-significantly (P > 0.05) during the prolonged submaximal test, but rose markedly (P < 0.05) following the performance ride. Lipid variables ascertained at rest were within the normal range for healthy subjects. ANOVA showed that blood T-Chol and TG were unchanged (P > 0.05), whereas HDL-C rose significantly (P < 0.05) in response to exercise. Post hoc analyses indicated that the latter change was due to a significant rise in HDL-C after the performance ride. It is concluded that apparent favourable changes in lipid profile variables occur in response to prolonged submaximal exercise followed by maximal effort, and these changes showed a good level of agreement over the two testing occasions.     

The effect of maximal exercise on the activity of neutrophil granulocytes in highly trained athletes in a moderate training period

Summary Leucocyte cell counts and the phagocytic and chemotactic activities of neutrophil granulocytes were investigated in highly endurance-trained long-distance runners (n = 10) and triathletes (n = 10) during a moderate training period and compared with untrained subjects (n= 0) before and up to 24 h after a graded exercise to exhaustion on a treadmill. After exercise a leucocytosis was noted with a significant increase in lymphocyte (P0.01) and neutrophil (P0.01) counts in all groups. In neutrophils the number of ingested inert latex beads was significantly increased (P 0.01) from 0.21 (SD 0.09) to 0.45 (SD 0.22) in controls, from 0.20 (SD 0.12) to 0.56 (SD 0.16) in long-distance runners and from 0.25 (SD 0.08) to 1.03 (SD 0.42) particles per cell in triathletes 24 h after exercise, compared with resting values. The capability of neutrophils to produce microbicidal reactive oxygen species fell (P:_ 0.05) immediately after exercise in all subjects and then increased by 36 (SD 8) %, 31 (SD 6) % and 19 (SD 9) % in controls, runners and triathletes respectively up to 24 h after exercise (P 0.05) compared with pre-start values. With respect to the absolute number of neutrophils, ingestion capacity, production of superoxide anions and chemotactic activity, no significant differences were found between athletes and control subjects at rest and after exercise. These data indicate, on the one hand, no impairment of the granulocyte system during a moderate training period in long-distance runners and triathletes but, on the other, that the prolonged activation of the phagocytosis reaction after exercise might impair the granulocyte system in periods of intensive training with high training frequency.     

Evidence of dependence of lipoprotein(a) on triglyceride and high-density lipoprotein metabolism

Lipoprotein(a) [Lp(a)] is a complex lipoprotein consisting of a low-density lipoprotein (LDL)-like ApoB₁₀₀-containing core particle covalently bound to apo(a), a large functionally complex glycoprotein. The mechanisms of Lp(a) metabolism and its interactions with cell-surface lipoprotein receptors are incompletely understood. In this study, we investigated the relationship of Lp(a) to other lipoproteins at high and normal levels of serum triglycerides (TGs). We measured serum lipid and Lp(a) particle concentrations in 148 unselected primary- and secondary-prevention patients. Subjects with TG > 200 mg/dL were classified as having high TG in accordance with National Cholesterol Education Program Adult Treatment Panel III guidelines. Our analysis revealed mean TG levels of 100 and 270 mg/dL in the normal and high TG groups, respectively. Lp(a)-C, Lp(a)-P, and Lp(a) cholesterol content per particle [Lp(a)-C/Lp(a)-P] did not differ between groups. At normal TG levels, stepwise multiple linear regression revealed that Lp(a)-P correlated with Lp(a)-C (P < 10^?6), ApoAI (P = .0001), the high-density lipoprotein cholesterol subfraction ratio (HDL₂-C/HDL₃-C; P = .002), and dense very-low-density lipoprotein cholesterol (VLDL₃-C; P = .04), overall model R = 0.74. At high TG levels, Lp(a)-P very strongly correlated primarily with HDL₂-C/HDL₃-C and TG-related variables with minimal dependence on Lp(a)-C (P = .09), overall model R = 0.96. These findings provide evidence of shared metabolic mechanisms for Lp(a), HDL, TG, and very low-density lipoprotein at high serum TG. Future studies are needed to elucidate common mechanisms, enzymes, and receptors involved in Lp(a) and HDL/TG metabolism with a focus on how these mechanisms are modified in the setting of hypertriglyceridemia.     

Does glutamine have a role in reducing infections in athletes?

There is an increased risk of infections in athletes undertaking prolonged, strenuous exercise. There is also some evidence that cells of the immune system are less able to mount a defence against infections after such exercise. The level of plasma glutamine, an important fuel for cells of the immune system, is decreased in athletes after endurance exercise: this may be partly responsible for the apparent immunosuppression which occurs in these individuals. We monitored levels of infection in more than 200 runners and rowers. The levels of infection were lowest in middle-distance runners, and highest in runners after a full or ultra-marathon and in elite rowers after intensive training. In the present study, athletes participating in different types of exercise consumed two drinks, containing either glutamine (Group G) or placebo (Group P) immediately after and 2 h after exercise. They subsequently completed questionnaires (n = 151) about the incidence of infections during the 7 days following the exercise. The percentage of athletes reporting no infections was considerably higher in Group G (81%,n= 72) than in Group P (49%,n = 79,p<0.001).     

Effects of biosynthetic human proinsulin on plasma lipids in type 2 diabetes mellitus

Summary Plasma cholesterol, triglycerides, HDL₂-cholesterol, and HDL₃-cholesterol were studied in 18 patients with Type 2 diabetes. Prior to entering the clinical trial, the study subjects were in stable control under a fixed mixture of 20% regular and 80% NPH (isophane) biosynthetic human insulin twice daily. The patients were randomized to treatment with either biosynthetic human proinsulin or biosynthetic human NPH insulin (controls) twice daily. Glucose control was kept constant in both groups throughout the study. Of the nine patients treated with proinsulin, eight exhibited a decrease of plasma triglycerides (median decrease by 0.13 mmol/l). In contrast, all nine controls showed a rise (median increase by 0.69 mmol/l) of plasma triglycerides (p<0.001). In keeping with the fall of plasma triglycerides, HDL₂-cholesterol rose in all but one proinsulin-treated patients. Both treatment modalities reduced HDL₃-cholesterol with a median decrease of 0.20 mmol/l (p<0.01) with proinsulin and 0.26 mmol/l with NPH insulin (p<0.05).We conclude that human proinsulin is able to reduce plasma triglycerides and to increase HDL₂-cholesterol in the majority of patients with Type 2 diabetes and thus appears to alter favourably risk factors for coronary heart disease.Abbreviations HDL High density lipoproteins - NPH insulin Neutral Protamine Hagedorn (isophane) insulin     

Effect of treatment on the concentration of lipoproteins and the postheparin-lipolytic activity in the plasma of noninsulin-dependent diabetics

Summary To study the effect of treatment on plasma lipid and lipoprotein concentration and on postheparin-lipolytic activity (PHLA) in plasma, 26 noninsulin-dependent diabetics were investigated who were treated with maximally effective doses of glibenclamide. The patients were randomly divided into two groups: In group I, glibenclamide was replaced by a long-acting insulin preparation given once daily at variable doses until satisfactory metabolic control was achieved. In group II, glibenclamide was replaced by placebo. At weeks 0, 1, 3, 7, and 12 after change of treatment, the following parameters were determined: Blood glucose, plasma concentrations of cholesterol, triglycerides, phospholipids, HDL cholesterol, very-low-density lipoproteins, intermediate-density lipoporteins, low density lipoproteins, high-density lipoproteins₂ (HDL₂), HDL₃, and PHLA. At week 0, no statistically significant differences existed between group I and group II with respect to all parameters mentioned above. The replacement of glibenclamide by insulin resulted in a continous decrease of blood glucose (p<0.01) with a concomitant increase in HDL₂ (p<0.01) and in PHLA (p<0.01) during the period of investigation. In contrast, replacement of glibenclamide by placebo exerted no significant influence on all determined parameters during 12 weeks. These data suggest that in noninsulin-dependent diabetics, who are inadequately controlled by sulfonylureas, an adequate insulin substitution is necessary to correct, apart from glucose metabolism, the impaired lipoprotein metabolism of diabetes mellitus. Sulfonylureas per se seem not to decrease the HDL₂ fraction nor the PHLA.     

Short-term exercise training improves diaphragm antioxidant capacity and endurance

These experiments tested the hypothesis that short-term endurance exercise training would rapidly improve (within 5 days) the diaphragm oxidative/antioxidant capacity and protect the diaphragm against contraction-induced oxidative stress. To test this postulate, male Sprague-Dawley rats (6 weeks old) ran on a motorized treadmill for 5 consecutive days (40–60 min · day⁻¹) at approximately 65% maximal oxygen uptake. Costal diaphragm strips were excised from both sedentary control (CON, n=14) and trained (TR, n=13) animals 24 h after the last exercise session, for measurement of in vitro contraction properties and selected biochemical parameters of oxidative/antioxidant capacity. Training did not alter diaphragm force-frequency characteristics over a full range of submaximal and maximal stimulation frequencies (P > 0.05). In contrast, training improved diaphragm resistance to fatigue as contraction forces were better-maintained by the diaphragms of the TR animals during a submaximal 60-min fatigue protocol (P < 0.05). Following the fatigue protocol, diaphragm strips from the TR animals contained 30% lower concentrations of lipid hydroperoxides compared to CON (P < 0.05). Biochemical analysis revealed that exercise training increased diaphragm oxidative and antioxidant capacity (citrate synthase activity +18%, catalase activity +24%, total superoxide dismutase activity +20%, glutathione concentration +10%) (P < 0.05). These data indicate that short-term exercise training can rapidly elevate oxidative capacity as well as enzymatic and non-enzymatic antioxidant defenses in the diaphragm. Furthermore, this up-regulation in antioxidant defenses would be accompanied by a reduction in contraction-induced lipid peroxidation and an increased fatigue resistance. Accepted: 6 August 1999     

Red cell 2,3-DPG,ATP, and mean cell volume in highly trained athletes

Summary 20 male elite long distance runners were compared to a control group of blood donors to determine the effect of training on red blood cells. The acute effects of exercise on red cells were investigated in 11 of the runners following a race of 15–30 km. The runners had elevated resting values of red cell 2,3-DPG (P<0.05) and mean cell volume (P<0.01); blood Hb and ATP were not different from concentrations in the control group. The red cell status of the athletes may be explained by an increased proportion of young erythrocytes in runners. No statistically significant changes in red cell 2,3-DPG, ATP, mean cell volume or blood Hb were found post exercise.     

The influence of the intensity of treadmill walking upon changes in lipid and lipoprotein variables in healthy adults

The purpose of the present study was to compare the acute and delayed effects of low- and moderate-intensity exercise on serum lipoprotein concentrations. Twelve healthy volunteers (five men, seven women), aged 28 (2) years [mean (SEM)], maximal oxygen uptake (O_2max) 48 (3) ml · kg^–1 · min^–1 walked on a treadmill for 90 min, on two separate occasions, in a balanced design. On one occasion walking was at a grade which elicited 32.1 (0.8)% of O_2max, i.e. low intensity, while on the other it elicited 60.1 (1.6)% of O_2max, i.e. moderate intensity (MI). Serum concentrations of total cholesterol (TC), triacylglycerol (TAG), high density lipoprotein cholesterol (HDL-C) and the subfraction HDL₂-C free fatty acids (FFA) and free glycerol were measured in venous blood samples drawn before exercise (after a 12-h fast), during walking and after 1 h and 24 h of recovery. Serum TAG concentrations decreased as a result of the exercise bout over the period of observation (P < 0.05), but this decrease was not different between the two intensities. Changes in serum TC concentrations over time differed between trials (P < 0.05). Serum free glycerol and FFA concentrations increased during exercise bouts, these increases being (P < 0.05) greater with MI. The decrease in serum TAG concentrations during and after a single episode of either prolonged low or moderate intensity exercise may be associated with an increased clearance and/or a decreased secretion of TAG-rich lipoproteins.     

Renal and cardiovascular responses to water immersion in trained runners and swimmers

The purpose of this study was to determine if fluid-electrolyte, renal, hormonal, and cardiovascular responses during and after multi-hour water immersion were associated with aerobic training. Additionally, we compared these responses in those who trained in a hypogravic versus a 1-g environment. Seventeen men comprised three similarly aged groups: six long-distance runners, five competitive swimmers, and six untrained control subjects. Each subject underwent 5 h of immersion in water [mean (SE)] 36.0 (0.5)°C to the neck. Immediately before and at each hour of immersion, blood and urine samples were collected and analyzed for sodium (Na), potassium, osmolality, and creatinine (Cr). Plasma antidiuretic hormone and aldosterone were also measured. Hematocrits were used to calculate relative changes in plasma volume (%V _pl). Heart rate response to submaximal cycle ergometer exercise (35% peak oxygen uptake) was measured before and after water immersion. Water immersion induced significant increases in urine flow, Na clearance (C _Na), and a 3–5% decrease in V _pl. Urine flow during immersion was greater (P < 0.05) in runners [2.4 (0.4) ml · min^–1] compared to controls [1.3 (0.1) ml · min ^–1]. However, %A V _pl, C _Cr, C _Na and during immersion were not different (P > 0.05) between runners, swimmers, and controls. After 5 h of immersion, there was an increase (P < 0.05) in submaximal exercise heart rate of 9 (3) and 10 (3) beats · min^–1 in both runners and controls, respectively, but no change (P > 0.05) was observed in swimmers. Since swimmers did not experience elevated exercise tachycardia following water immersion compared to runners and sedentary controls, we conclude that exercise training in a hypogravic environment attenuates the acute cardiovascular adaption to microgravity. This effect of hypogravic aerobic training was not associated with the degree of hypovolemia and associated diuresis and natriuresis.     

Plasma lecithin: cholesterol acyltransferase activity in elite athletes from selected sports

Summary The activity of lecithin: cholesterol acyltransferase (LCAT) and the plasma lipoprotein concentrations of elite athletes from 8 selected sports (volleyball, judo, sprinting, wrestling, throwing, cycling, water polo and tennis) were determined and compared with those of a sedentary control group. Plasma LCAT activity levels in the athletes were significantly 2.2–7.0 times higher than in the controls in most sports (p<0.01). Judo, sprinting, wrestling and throwing had comparable LCAT values while tennis, volleyball and cycling were considerably higher. HDL-C concentration was significantly higher than controls in the water polo (p<0.05), cycling and volleyball (P<0.01) groups. Percentage lipoprotein distribution in the athletes in all sports except tennis, throwing and wrestling were similar to the controls. The differences among groups in LCAT activity may be related to the effect of physical exercise and training adaptations to lipid metabolism. This may be of importance when judging the benefit of exercise for atherosclerosis protection.