The acute effect of marathon running on plasma lipoproteins in female subjects

The acute effect of running a 42.2 km marathon race on plasma lipoproteins was investigated in 12 female subjects (aged 21 to 41 years). During the race there was a significant increase (P less than 0.01) in the concentration of total plasma cholesterol. The mean post-race concentration of high density lipoprotein cholesterol (HDL-C) was 64.0 +/- 16.2 (SD) mg 100 ml-1, compared with 52.1 +/- 14.0 mg 100 ml-1 before the race, representing a significant increase (P less than 0.002). There was no significant difference in the concentration of very low density lipoprotein (VLDL) or low density lipoprotein (LDL) before and after the exercise. The mean concentration of the cholesteryl ester moiety of the HDL increased from 43.7 +/- 12.3 to 54.3 +/- 15.7 mg 100 ml-1 (P less than 0.002), while there was no significant changes in the concentration of the unesterified cholesterol, phospholipid, triacylglycerol or protein moieties of the HDL. The relative proportions of apolipoproteins A-I, A-II, C and E remained unchanged during the exercise. The changes in the concentration of each of the lipoprotein fractions observed during the marathon varied considerably between subjects. The individual increases in the concentration of HDL-C ranged from 4.1 to 28.4 mg 100 ml-1, while both increases and decreases in individual concentrations of VLDL and LDL as well as of total plasma cholesterol were observed. These observations suggest that women undergo greater changes in HDL-C concentration that men during acute exercise, while considerable variation between individuals occurs.     

Creatine kinase-MB isoenzyme adaptations in stressed human skeletal muscle of marathon runners

The creatine kinase (CK) isoenzyme composition was determined in serial gastrocnemius muscle biopsies obtained from 12 male marathon runners. The mean muscle CK-MB composition significantly increased after chronic exercise (training) from 5.3% (pretraining) to 7.7% (premarathon) as well as after acute exercise (postmarathon) to 10.5% of the total CK activity (P less than 0.05). However, no significant differences in total CK activities were detected. Additionally, mitochondrial CK and CK-BB isoenzymes were present in muscle homogenates. A significant correlation was observed in the increase in mean serum total CK (3,322 U/l) and CK-MB (174 U/l) activities 24 h after the race (r = 0.98, P less than 0.05). These results show that gastrocnemius muscle adapts to long-distance training and racing with increased CK-MB activities and imply that skeletal muscle is the major source of elevated serum CK-MB activities in marathon runners.     

Skeletal muscle lactate dehydrogenase isozyme alterations in men and women marathon runners

Total lactate dehydrogenase (LD) and LD isozyme activities in gastrocnemius muscle from trained men and women runners were measured in response to the chronic stress of training for a marathon race (42.2 km). Following 9 wk of training, total LD activity in skeletal muscle from men and women runners significantly (P less than 0.02) decreased 2.26 and 2.25 U/mg protein, respectively. However, men's total LD activities were significantly (P less than 0.001) less than the women's both before and after training. Significant (P less than 0.05) increases in LD1 activities in skeletal muscle in men and women runners were also observed after training. No significant correlations were detected between percent fiber type composition in men or women vs. the changes in total LD activity, changes in LD1 activity, maximal O2 consumption or training distance averaged per week after the training period. The biochemical adaptations in skeletal muscle that occurred in the LD isozyme composition in both men and women runners make the runners skeletal muscle appear similar to heart muscle in LD1 and LD2 activities.     

Skeletal muscle creatine kinase MB alterations in women marathon runners

Total creatine kinase (CK) and CK MB activities were determined in gastrocnemius muscle and serum obtained from 14 female marathon runners. The level of CK MB in muscle increased significantly (p less than 0.05) after chronic exercise training from 5.3% to 10.5% of the total CK activity, but not after acute exercise (post-marathon 8.9%). No significant differences in total CK activities were detected. However, the total CK activity in the muscles were significantly (p less than 0.05) less than those previously reported from the muscle of men runners (1800 U/g, 3000 U/g respectively). No significant correlation existed between fiber type and muscle CK MB activity. Additionally, trace amounts of mitochondrial CK and CK BB were present in muscle homogenates. A significant correlation was observed in the increase in mean serum total CK (597 UL-1) and CK MB (23 UL-1) activities 24 h after the race (r = 0.97, p less than 0.05). These results suggest that gastrocnemius muscle in women adapts to training with increased CK MB activities and imply that skeletal muscle is the major source of elevated serum CK MB activities in women marathon runners.     

Airway inflammation in nonasthmatic amateur runners

Elite athletes show a high prevalence of symptoms and signs of asthma, but no study has assessed the acute effects of endurance exercise on airway cells in nonasthmatic athletes. We measured exhaled nitric oxide (NO) and collected samples of induced sputum after 3% NaCl aerosol administration for 20 min in nonasthmatic middle-aged amateur runners after the Fourth Palermo International Marathon and 6--9 wk later (habitual training period) at baseline. After the marathon, exhaled NO (n = 9 subjects) was higher [27 +/- 9 parts/billion (ppb)] than at baseline (12 +/- 4 ppb; P < 0.0005). Polymorphonuclear neutrophil (PMN) counts in induced sputum were much higher in runners (91.2 +/- 3.6% of total cells postmarathon and 78.7 +/- 9.1% at baseline) than in sedentary control subjects (9.9 +/- 5.9%; P < 0.001). Expression of L-selectin and CD11b/CD18 in sputum PMNs was lower after the race than at baseline and inversely related to the amount of exhaled NO (r = -0.66 and -0.69, respectively; P < 0.05). Our data indicate that sputum PMNs are increased in nonasthmatic runners both after a marathon and at baseline and suggest that NO may modulate exercise-associated inflammatory airway changes.     

Beta-endorphin activity and hypercapnic ventilatory responsiveness after marathon running

To investigate the hypothesis that endurance exercise may lead to a decrease in ventilatory chemosensitivity as possibly mediated by an increase in endogenous beta-endorphins, we measured hypercapnic ventilatory responsiveness (HCVR) and circulating beta-endorphin immunoreactivity in six runners before and after a marathon (42.2 km) race and after administration of 10 mg iv naloxone. Similar testing was performed at identical time periods on the day before the marathon as control data. On each occasion, HCVR was measured twice 15 min apart, and the mean value was used for analysis. Six active (training distance 50-104 km/wk) and experienced (no. of marathons completed, 1-25) runners participated in the study. There were no significant changes in beta-endorphin activity or HCVR on the control day. All runners experienced a rise in beta-endorphin activity from premarathon (21.3 +/- 16.0 pg/ml) to immediate postmarathon (89.6 +/- 84.9 pg/ml) values (P less than 0.05). However, HCVR showed no significant change at any of the three testing periods on the marathon day. To investigate whether a time delay may have affected the lack of response to naloxone, additional testing was performed in five subjects, except that 10 mg iv naloxone was given within 10 min after completion of the marathon, and then HCVR was measured. Although there was a greater than fourfold increase in beta-endorphin immunoreactivity after the marathon, there was no significant change in HCVR after naloxone administration. We conclude that natural increases in endogenous beta-endorphin activity associated with marathon running do not modulate central chemosensitivity.     

Changes in adrenal and testicular activity monitored by salivary sampling in males throughout marathon runs

Measurement of cortisol and testosterone in saliva samples provided by marathon runners at 6.4 km (4-mile) intervals has been used for monitoring acute changes in adrenal and testicular activity, and the changes compared with mean values in timed samples on five rest days. The collection of mixed whole saliva was well accepted; the missed sample rate in the 8 runners in the Cardiff marathon was less than 10%. On rest days, salivary cortisol and testosterone were within the normal male range and showed a circadian rhythm; mean values at 08.00 h (23.5 nmol L-1; 258 pmol L-1, p less than 0.001, p less than 0.001 respectively) were higher than at 22.00 h (2.8 nmol L-1; 130 pmol L-1). In samples collected at 09.00 h, immediately prior to the Cardiff marathon, cortisol (25.1 nmol L-1) and testosterone (304 pmol L-1) were higher than the mean values (14.9 nmol L-1; 209 pmol L-1) on non-run days. Concentrations of both steroids increased during the marathon; testosterone peaked (442 pmol L-1) at 21 miles, whereas cortisol continued to increase, being maximal (87.9 nmol L-1) at 30 min after completion of the run. Four of the runners in the Cardiff marathon also participated in the Bristol marathon and the changing patterns in salivary hormones were strictly comparable. Salivary sampling would appear to be of value in monitoring acute and rhythmic changes in endocrine function in marathon runners. The temporal relationship between changes in salivary cortisol and testosterone are consistent with direct inhibition of testicular secretion by high cortisol concentrations.     

Erythropoietic adaptations to endurance training

Erythropoietic adaptations involving the oxygen dissociation curve (ODC) and erythropoietin production have been implicated in the etiology of reduced blood haemoglobin concentrations in sportspersons (known as sports anaemia). A significant increase in the half-saturation pressure indicating a right-shift in the ODC was measured in 34 male [25.8-27.4 mmHg (3.44-3.65 kPa)] and 16 female (25.8-27.7 mmHg (3.44-3.69 kPa)] trained distance runners (P less than 0.01 for both genders) after completing a standard 42-km marathon. Erythrocyte 2,3-diphosphoglycerate concentrations measured concurrently were unaltered by exercise, although consistently higher in the female compared to the male athletes (P less than 0.05). The serum erythropoietin (EPO) concentrations of 15 male triathletes (26.3 U.ml-1) were significantly lower than those of 45 male distance runners (31.6 U.ml-1; P less than 0.05). However, the mean serum EPO concentrations of male and female athletes engaged in a variety of sports were not different from those of sedentary control subjects of both sexes (26.5-35.3 U.ml-1). Furthermore, the serum EPO concentrations were unaltered after prolonged strenuous exercise in 20 male marathon runners. These data suggest that the haematological status of these endurance athletes is in fact normal and that the observed shift in the ODC, while providing a physiological advantage during exercise, has no measurable effect on the erythropoietic drive.     

Alterations in plasma-volume-corrected blood components of marathon runners and concomitant relationship to performance

The study was undertaken to determine the effects of running a marathon on concentration of various blood components resulting from phenomena other than fluid loss, and these were related to performance times. Twenty male marathon runners ranging from 20 to 50 years of age participated in the study. Blood samples were collected before and after the subjects ran in a marathon. Blood samples were analyzed for sodium, potassium, glucose, lactate dehydrogenase, creatinine, creatine phosphokinase, triglycerides, cholesterol, hematocrit, hemoglobin, protein, white blood cell number, uric acid, carbon dioxide, and iron. All of the blood parameters increased significantly in concentration with the exceptions of glucose and carbon dioxide which decreased. After accounting for plasma-volume loss (COR), there remained significant increases in blood serum lactate dehydrogenase, creatinine, creatine phosphokinase, uric acid, iron, and whole-blood white blood cell number. Significant decreases in COR serum sodium, protein, glucose, and carbon dioxide were found. Lactate dehydrogenase and creatine phosphokinase concentration changes support the concept of acute damage to muscle tissue resulting from marathon running. No strong relationship between performance time and other measured variables was found. COR measures were more representative of marathon induced blood changes from physiological dynamics other than plasma volume change than presently reported findings.     

Effect of physical training in humans on the response of isolated fat cells to epinephrine

Endurance training helps muscle tissue oxidize lipids and therefore helps conserve glycogen. It was thought interesting to find out if, in addition to this preferential use of fatty acids by muscle tissue, there is an increase in the capacity of adipose tissue to mobilize lipids. So the response to epinephrine of collagenase-isolated fat cells obtained after biopsies of fat performed in the periumbilical region of 10 trained marathon runners (T) and 10 sedentary subjects (S), all males, was studied in vitro. Glycerol release, chosen as adipocyte lipolysis indicator, was measured by bioluminescence. Lipolysis was studied with increased epinephrine concentration. This caused a significant increase in lipolysis only in the T subjects. The dose-response curves were significantly different for T and S subjects at 10(-6) M and above (P less than 0.05). To determine the modification mechanisms observed, lipolysis with isoproterenol and epinephrine plus propranolol were studied. Isoproterenol significantly increased lipolysis in both groups. The dose-response curves were significantly different at 10(-7) M (P less than 0.01) and above. In both groups, epinephrine plus propranolol significantly decreased lipolysis without distinction between T and S. It is concluded that in male subjects endurance training increases the sensitivity of subcutaneous abdominal adipose tissue to the lipolytic action of epinephrine; this effect seems to be related to an increased response of the beta-adrenergic pathways.     

Plasma noncholesterol sterols in male distance runners and sedentary men

Plasma lathosterol concentration is taken to be an index of the rate of cholesterol synthesis and plasma concentrations of plant sterols just as campesterol and betasitosterol are taken to be indeces of cholesterol absorption efficiency. These noncholesterol sterols were measured in plasma from 14 male distance runners and 10 sedentary men. Plasma lathosterol concentration was 30% lower (P less than 0.02) and plasma betasitosterol concentration was 33% higher (P less than 0.02) in the runners compared to the sedentary men. Plasma concentrations of lathosterol and plant sterols were inversely and significantly (P less than 0.05) correlated in both the runners and the sedentary men. Plasma plant sterol concentrations were correlated positively and significantly (P less than 0.01) with plasma high density lipoprotein cholesterol (HDL-C) concentrations in the runners and sedentary men combined. These findings suggest that more efficient cholesterol absorption may lead to higher plasma plant sterol concentrations and may contribute to lower cholesterol synthesis rates, reduced concentrations of plasma lathosterol and higher plasma HDL-C concentration in distance runners.     

Serum sterols during stanol ester feeding in a mildly hypercholesterolemic population

We investigated the changes of cholesterol and non-cholesterol sterol metabolism during plant stanol ester margarine feeding in 153 hypercholesterolemic subjects. Rapeseed oil (canola oil) margarine without (n = 51) and with (n = 102) stanol (2 or 3 g/day) ester was used for 1 year. Serum sterols were analyzed with gas-liquid chromatography. The latter showed a small increase in sitostanol peak during stanol ester margarine eating. Cholestanol, campesterol, and sitosterol proportions to cholesterol were significantly reduced by 5-39% (P < 0.05 or less for all) by stanol esters; the higher their baseline proportions the higher were their reductions. The precursor sterol proportions were significantly increased by 10- 46%, and their high baseline levels predicted low reduction of serum cholesterol. The decrease of the scheduled stanol dose from 3 to 2 g/day after 6-month feeding increased serum cholesterol by 5% (P < 0. 001) and serum plant sterol proportions by 8-13% (P < 0.001), but had no consistent effect on precursor sterols. In twelve subjects, the 12-month level of LDL cholesterol exceeded that of baseline; the non-cholesterol sterol proportions suggested that stimulated synthesis with relatively weak absorption inhibition contributed to the non-responsiveness of these subjects. In conclusion, plant stanol ester feeding lowers serum cholesterol in about 88% of subjects, decreases the non-cholesterol sterols that reflect cholesterol absorption, increases the sterols that reflect cholesterol synthesis, but also slightly increases serum plant stanols. Low synthesis and high absorption efficiency of cholesterol results in the greatest benefit from stanol ester consumption.     

Postheparin plasma lipoprotein and hepatic lipase are determinants of hypo- and hyperalphalipoproteinemia

To study the role of the two postheparin plasma lipolytic enzymes, lipoprotein lipase (LPL) and hepatic lipase (HL) in high density lipoprotein (HDL) metabolism at a population level, we determined serum lipoproteins, apoproteins A-I, A-II, B, and E, and postheparin plasma LPL and HL activities in 65 subjects with a mean HDL-cholesterol of 34 mg/dl and in 62 subjects with a mean HDL-cholesterol of 87 mg/dl. These two groups represented the highest and lowest 1.4 percentile of a random sample consisting 4,970 subjects. The variation in HDL level was due to a 4.1-fold difference in the HDL2 cholesterol (P less than 0.001) whereas the HDL3 cholesterol level was increased only by 32% (P less than 0.001) in the group with high HDL-cholesterol. Serum apoA-levels were 128 +/- 2.2 mg/dl and 210 +/- 2.8 mg/dl (mean +/- SEM) in hypo- and hyper-HDL cholesterolemia, respectively. Serum apoA-II concentration was elevated by 28% (P less than 0.001) in hyperalphalipoproteinemia. The apoA-I/A-II ratio was elevated only in women with high HDL-cholesterol but not in men, suggesting that elevation of apoA-I is involved in hyperalphalipoproteinemia in females, whereas both apoA proteins are elevated in men with high HDL cholesterol. Serum concentration of apoE and its phenotype distribution were similar in the two groups. The HL activity was reduced in the high HDL-cholesterol group (21.2 +/- 1.5 vs. 38.5 +/- 1.8 mumol/h/ml, P less than 0.001), whereas the LPL activity was elevated in the group with high HDL-cholesterol compared to subjects with low HDL-cholesterol (27.8 +/- 1.3 vs. 19.9 +/- 0.8 mumol/h/ml, P less than 0.001). The HL and LPL activities correlated in opposing ways with the HDL2 cholesterol (r = 0.57, P less than 0.001 and r = 0.51, P less than 0.001, respectively), and this appeared to be independent of the relative ponderosity by multiple correlation analysis. The results demonstrate major influence of both HL and LPL on serum HDL cholesterol concentration at a population level.     

Effects of high dose progestin on serum lipids and lipid metabolizing enzymes in patients with endometrial cancer

The effect of high dose medroxyprogesterone acetate (MPA) on serum lipids, on adipose tissue lipoprotein lipase (LPL) and serum lecithin cholesterol acyltransferase activities were studied in 15 postmenopausal patients with endometrial cancer. After 2 weeks of MPA treatment total cholesterol decreased by 14% (P less than 0.001) and HDL cholesterol by 33% (P less than 0.01) from the respective pretreatment values; correspondingly the ratio of HDL to total cholesterol decreased (P less than 0.05). The decrease of HDL2 cholesterol was 35% (P less than 0.01) and that of HDL3 cholesterol 15% (P less than 0.01). The levels of serum triglycerides decreased significantly (P less than 0.05) during the treatment period. Serum LCAT activity was significantly lower (P less than 0.05) after treatment than before, but adipose tissue LPL activity was not altered. The mean serum testosterone level decreased significantly (P less than 0.001) from the pretreatment values. Significant positive correlations were present between LPL activity and MPA concentrations and between LPL activity and testosterone concentrations after the drug treatment.     

Contraceptive steroids increase cholesterol in bile: mechanisms of action

Contraceptive steroids increase the risk of acquiring cholesterol gallstones. The factors responsible include an increase in cholesterol saturation of bile and an increase in rate of secretion of cholesterol into bile. The goal of this study was to investigate the mechanism(s) of these increases in biliary cholesterol. During the use of contraceptive steroids, cholesterol saturation of gallbladder bile and the amount of cholesterol secreted per mole of bile acid increased (P less than 0.05 and P less than 0.02, respectively). Cholesterol absorption, cholesterol synthesis, chylomicron remnant clearance, and the concentration of plasma and lipoprotein lipids were not altered by contraceptive steroids. Despite this apparent lack of effect, important correlations were present during steroid use. LDL (low density lipoprotein) cholesterol increased as dietary cholesterol increased (r = 0.58, P less than 0.025). Cholesterol synthesis correlated directly with VLDL cholesterol concentration (r = 0.64, P less than 0.01), biliary cholesterol secretion (r = 0.68, P less than 0.01) and with molar percent cholesterol in bile (r = 0.49, P = 0.06). Chylomicron remnant clearance also correlated with cholesterol secretion (r = 0.85, P less than 0.001). As either remnant uptake or synthesis increased, the effect of the other source of hepatic cholesterol on biliary cholesterol secretion diminished. These relationships were not observed in the same subjects when they were not taking the hormones. The findings suggest that both newly synthesized and dietary cholesterol contribute to the cholesterol secreted in bile. This is consistent with the hypothesis that cholesterol for secretion into bile and VLDL is derived from a common metabolic pool of free cholesterol. It is proposed that contraceptive steroids exert their effect on biliary cholesterol by increasing cholesterol entering the pool and/or by inhibiting hepatic ACAT (acylcoenzyme A:cholesterol acyltransferase) activity, a known effect of progesterone, so that an increase in free cholesterol entering the pool leads to an increase in output.     

Effect of prolonged physical exercise on intra-erythrocyte and plasma potassium

The intracellular concentrations of sodium [Na+] and potassium [K+] and the water content in human erythrocytes were investigated in 21 male runners before and after a marathon. From 2 to 5 min after the race, the intra-erythrocyte [K+] was significantly decreased (p less than 0.001) by 7% whereas the plasma [K+], intra-erythrocyte [Na+] and the erythrocyte water content were unchanged. The change in the intra-erythrocyte [K+] observed immediately after the marathon, was negatively correlated with the race time (r = -0.44; p less than 0.05). Furthermore, the change in the plasma [K+] (r = -0.64; p less than 0.001) and the amount of K+ excreted in the urine during the race (r = 0.54; p less than 0.05) were also, respectively, negatively and positively correlated with the race time. It is concluded that during prolonged physical exercise the erythrocytes could serve as a kind of K+ reservoir that is drained with increasing magnitude of body K+ loss. This might explain why in the faster marathon runners, in whom the urinary K+ loss is smaller and the K+ intake is greater than in the slower runners during race, the intra-erythrocyte [K+] is unchanged after a marathon whereas in the slower runners it is decreased.     

Cytokine changes after a marathon race.

The influence of carbohydrate (1 l/h of a 6% carbohydrate beverage), gender, and age on pro- and anti-inflammatory plasma cytokine and hormone changes was studied in 98 runners for 1.5 h after two competitive marathon races. The marathoner runners were randomly assigned to carbohydrate (C, n = 48) and placebo (P, n = 50) groups, with beverages administered during the races in a double-blind fashion using color codes. Plasma glucose was higher and cortisol was lower in the C than in the P group after the race (P < 0.001). For all subjects combined, plasma levels of interleukin (IL)-10, IL-1 receptor antagonist (IL-1ra), IL-6, and IL-8 rose significantly immediately after the race and remained above prerace levels 1.5 h later. The pattern of change in all cytokines did not differ significantly between the 12 women and 86 men in the study and the 23 subjects > or =50 yr of age and the 75 subjects <50 yr of age. The pattern of change in IL-10, IL-1ra, and IL-8, but not IL-6, differed significantly between the C and the P group, with higher postrace values measured for IL-10 (109% higher) and IL-1ra (212%) in the P group and for IL-8 (42%) in the C group. In conclusion, plasma levels of IL-10, IL-1ra, IL-6, and IL-8 rose strongly in runners after a competitive marathon, and this was not influenced by age or gender. Carbohydrate ingestion, however, had a major effect in attenuating increases in cortisol and two anti-inflammatory cytokines, IL-10 and IL-1ra.     

High density lipoprotein subfractions and physical activity: changes after moderate and heavy exercise training.

The changes in high density lipoprotein (HDL) subfractions have been studied in 106 young healthy men after two months of physical training at a military base. Forty subjects were placed on a heavy intensity training program (HITP) with a daily average energy expenditure estimated as 3,504 Kcal, and 66 subjects followed a moderate intensity training program (MITP) with an average energy expenditure estimated as 2,942 Kcal/day. The HITP group reduced their body fat while HDL-cholesterol, HDL2-cholesterol and apoprotein (apo) A-I increased by 8.4%, 30% and 16.9% respectively (p less than 0.001). Body fat of MITP subjects did not change and HDL-cholesterol, HDL2-cholesterol and apo A-I increased by 5.6% (p less than 0.05), 17.1% (p less than 0.001) and 5.6% (p less than 0.05), respectively. The increase in serum apo A-I level was significantly higher (p less than 0.005) in the heavy intensity training group. The apo A-I/A-II ratio increased significantly in both groups (p less than 0.001), reflecting an increase in the HDL2/HDL3 ratio. This is in agreement with the significant increase in HDL2-cholesterol in both groups (p less than 0.001) with no change or decrease in HDL3-cholesterol.     

Exaggerated ANF response to exercise in middle-aged vs. young runners

Hormonal, electrolyte, and renal responses were measured before, during, and after a marathon (42.2 km) in 14 runners: 8 young (Y) (mean age 27.8 yr) and 6 middle aged (MA) (mean aged 46.7 yr). No differences between groups in prerun values for heart rate (HR), plasma osmolality (OSM), antidiuretic hormone (ADH), aldosterone (ALDO), atrial natriuretic factor (ANF), or plasma renin activity (PRA) were found. Renal and urinary measurements were also similar between groups before the marathon. After 10 km of running, both groups had significant increases in HR, ALDO, ANF, and PRA, while OSM, Na+, and ADH remained unchanged from prerun values. The increase in plasma ANF concentrations at this point was significantly greater in the MA subjects compared with the Y (mean increase 104.1 vs. 42.8 pg/ml, respectively; P less than 0.01). Immediate postmarathon values for OSM, ADH, and Na+ were significantly higher than initial values in both groups, while HR, PRA, and ALDO continued to increase above the elevated levels found at 10 km. ANF values immediately postmarathon remained higher than prerun concentrations but were significantly reduced from those obtained at 10 km. In contrast, HR continued to rise until the completion of the run. These data are consistent with recent reports of an exaggerated ANF response in older subjects in response to central blood volume expansion.     

Dehydration and serum biochemical changes in marathon runners

The effects of a competitive marathon race on serum biochemical and haematological parameters have been evaluated. Blood samples were obtained shortly before and immediately after the race; urine samples were also obtained before and after the race. Body weight was recorded pre- and post-race. During the race subjects consumed a total of 1.41 of either water or a dilute glucose-electrolyte solution. The average weight loss of the runners was 2.09 +/- 0.77 kg (mean +/- SD), corresponding to 2.9 +/- 0.8% of body weight. Small but significant increases in both haematocrit and haemoglobin concentration occurred; plasma volume was calculated to decrease by 4.7%. Serum potassium concentration showed no change, but the response was highly variable; serum sodium concentration increased in line with the decrease in plasma volume. In the group of subjects drinking water during the race, the pre-race plasma glucose concentration was 5.3 +/- 1.2 mmol . l-1, this was unchanged after the race (5.0 +/- 1.2 mmol . l-1). A significant increase (P less than 0.01) in the plasma glucose concentration, from 5.2 +/- 0.6 to 6.0 +/- 1.5 mmol . l-1 occurred in the group of subjects drinking the glucose-electrolyte solution. Apart from this, there were no significant differences between the two groups.