Changes of white blood cell count during prolonged exercise

Leukocytosis was postulated to accompany short- and medium-length exercise; in this report, we have studied the changes in leukocyte count during and following prolonged exercise. White blood cell (WBC) counts were obtained in 15 endurance-trained subjects before, during, and at a recovery period after an ultralong exercise (120 km march), lasting 24 h. WBC counts increased after 16 h march from a baseline value of 8.5 +/- 0.3 10(9) l-1 to 11.3 +/- 0.8 10(9) l-1 (P less than 0.05) and then declined to 7.1 +/- 0.9 10(9) l-1 after 24 h march with no further significant changes during 64 h of recovery. These observations were supported by previous findings in three separate marches performed by a second group (40, 70, and 120 km). A parallel increase in plasma creatine phosphokinase activity from 127 +/- 4.4 ul-1 to 539 +/- 106.3 ul-1 was observed after 16 h march (P less than 0.01), indicating muscle cell damage. Our findings suggest that in extremely long marches, WBC counts return to baseline values before exercise is terminated. This phenomenon may reflect WBC infiltration to damaged muscle tissue.     

Catecholamines and fuels after an ultralong run: persistent changes after 24-h recovery

This study examined the alterations induced by an ultralong distance run (169 +/- 6 km in 24 h) and by prolonged postrace recovery (24 h) on blood fuel metabolites and catecholamines in seven trained subjects. Ten minutes after the race, plasma concentrations of glycerol and free fatty acids (FFA) were decreased twofold. Plasma glucose was unchanged. Plasma concentrations of free norepinephrine (NE) and free dopamine (DA) increased from 2.73 +/- 0.28 to 5.41 +/- 1.11 nmol.l-1 and from 0.45 +/- 0.13 to 0.62 +/- 0.18 nmol.l-1 whereas free epinephrine (E) and insulin were unchanged; 24 h after the race, plasma glycerol and FFA concentrations remained elevated (twofold) and TG decreased twofold compared with resting levels. Concomitantly, plasma NE and DA levels remained elevated, respectively, 6.23 +/- 0.41 and 0.77 +/- 0.13 nmol.l-1. These data show that the alterations in circulating fuel metabolites and NE induced by the ultralong race were still present 24 h later. The involvement of lipid metabolism and catecholamines in processes of post-exercise recovery is discussed.     

Oxidation and metabolic effects of fructose or glucose ingested before exercise

The aim of this study was to compare the effects of fructose (F) and glucose (G) intake before exercise on oxidation of the ingested substrate, glycogen utilization, work output, and metabolic changes. Ten trained subjects ingested F or G (1 g/kg), both of which were naturally enriched in 13C. After 1 h of rest, they exercised on an ergometer at 61% of their maximal oxygen uptake (VO2 max) for 45 min, which was immediately followed by 15 min at their maximal voluntary output. During the resting hour, blood insulin and glucose were lower (p less than 0.05) and respiratory quotient and blood lactate higher (p less than 0.01) after F. During exercise, the differences disappeared, apart from a transient but moderate (4.3 mmol/l) hypoglycemia after G compared to F. No difference between F and G was observed for uric acid, glycerol, FFA, and glucagon. Glycogen decrements in the vastus lateralis muscle were 67 +/- 9 (F) and 97 +/- 15 (G) mmol/kg, values not significantly different from each other (P greater than 0.05). The maximal voluntary work produced during the last 15 min did not differ between treatments. During the 2 h after sugar ingestion, 30 +/- 3 g of F and 26 +/- 3 g of G were oxidized to 13CO2. These findings indicate that fructose ingested before exercise was utilized at least as well as glucose, allowed a more stable glycemia, and did not modify performance.     

Effects of chromium supplementation on glycogen synthesis after high-intensity exercise

PURPOSE: Chromium enhances insulin signaling and insulin-mediated glucose uptake in cultured cells. We investigated the effect of chromium on glycogen synthesis and insulin signaling in humans. METHODS: Sixteen overweight men (BMI = 31.1 +/- 3.0 kg.m) were randomly assigned to supplement with 600 microg.d chromium as picolinate (Cr; N = 8) or a placebo (Pl; N = 8). After 4 wk of supplementation, subjects performed a supramaximal bout of cycling exercise to deplete muscle glycogen, which was followed by high-glycemic carbohydrate feedings for the next 24 h. Muscle biopsies were obtained at rest, immediately after exercise, and 2 and 24 h after exercise. RESULTS: Elevations in glucose and insulin during recovery were not different, but the lactate response was significantly higher in Cr. There was a significant depletion in glycogen immediately after exercise, an increase at 2 h, and a further increase above rest at 24 h (P < 0.05). The rate of glycogen synthesis during the 2 h after exercise was not different between groups (Cr: 25.8 +/- 8.0 and Pl: 17.1 +/- 4.7 mmol.kg.h). Glycogen synthase activity was significantly increased immediately after exercise in both groups. Muscle phosphatidylinositol 3-kinase (PI 3-kinase) activity decreased immediately after exercise and increased at 2 h (P < 0.05), with a trend for a lower PI 3-kinase response in Cr (P = 0.08). CONCLUSIONS: Chromium supplementation did not augment glycogen synthesis during recovery from high-intensity exercise and high-carbohydrate feeding, although there was a trend for lower PI 3-kinase activity.     

Insulin stimulates liver glucose uptake in humans: an 18F-FDG PET Study.

The liver is vital for the regulation of glucose metabolism, but inaccessibility of the organ for direct assessments has limited the study of its metabolic role in vivo. METHODS: The effect of insulin and insulin sensitivity (IS) on hepatic glucose uptake was investigated using PET, (18)F-FDG, and graphical analysis and 3-compartment modeling in humans. We studied 16 healthy sedentary men (normal IS), 8 athletes (high IS), and 7 patients with coronary artery disease (low IS) either during fasting (n = 14) or during euglycemic hyperinsulinemia (n = 24). RESULTS: Whole-body insulin-mediated glucose uptake was 35 +/- 7 micro mol/min/kg for normal-IS subjects, 65 +/- 8 micro mol/min/kg for high-IS subjects (P < 0.05 vs. normal IS), and 24 +/- 3 micro mol/min/kg for low-IS subjects (P < 0.05 vs. normal IS and high IS). Hyperinsulinemia enhanced hepatic glucose influx (2.3 +/- 0.9 vs. 1.5 +/- 0.7 micro mol x min(-1) x 100 mL(-1), P < 0.05) and phosphorylation rates (0.55 +/- 0.24 vs. 0.36 +/- 0.19 min(-1) x 10(-2), P < 0.05) similarly in insulin-sensitive and -resistant subjects. During hyperinsulinemia, however, the glucose phosphorylation-to-dephosphorylation ratio was significantly lower in the low-IS group than in normal-IS subjects (P < 0.05) or high-IS subjects (P < 0.01); correspondingly, whole-body insulin-mediated glucose disposal was directly related to this ratio (r = 0.45; P < 0.05). Furthermore, glucose influx rates were inversely correlated with fasting plasma free fatty acids (P < 0.05). Both compartmental modeling and the graphical approach accurately described the data, though the latter yielded slightly lower estimates of glucose influx rates during fasting. CONCLUSION: Our study provided evidence that physiologic hyperinsulinemia enhances hepatic glucose uptake and that IS is related to the glucose phosphorylation-to-dephosphorylation balance in the liver. Graphical analysis and modeling proved to be applicable and complementary tools for the investigation of glucose metabolism in the liver.     

Improved insulin sensitivity in carbohydrate and lipid metabolism after physical training

To estimate physical training effects quantitatively, the relationship between tissue sensitivity to exogenous insulin (glucose metabolism determined by euglycemic insulin-clamp technique) and maximal oxygen uptake (VO2 max) was defined in 9 well-trained athletes and 14 untrained subjects with normal glucose tolerance. Tissue sensitivity to exogenous insulin in the athletes was significantly higher than in the controls (P less than 0.001). Seven untrained subjects continued the physical exercise program. After physical training for 1 month, glucose metabolism increased from 40.3 +/- 3.9 mumol/kg/min to 42.2 +/- 4.4 mumol/kg/min (P less than 0.05) and VO2 max also increased significantly (P less than 0.05). During euglycemic hyperinsulinemia, both plasma FFA (P less than 0.001) and glycerol (P less than 0.05) decreased rapidly after physical training. Glucose metabolism directly correlated with VO2 max (P less than 0.001). These results suggest that the euglycemic insulin-clamp technique provides a reliable estimate of training effects, tissue sensitivity to physiologic hyperinsulinemia is 46% higher in trained athletes, and physical training improves insulin sensitivity not only in glucose metabolism but also in lipid metabolism.     

Exercise performance, core temperature, and metabolism after prolonged restricted activity and retraining in dogs.

To study physiological effects of restricted activity (RA) and subsequent retraining, 10 male mongrel dogs (1-5 years) performed a submaximal exercise endurance test on a treadmill (12 degrees slope, 1.6 m.s-1) during kennel control, after 8 weeks of cage (40 cm-w x 80 cm-h x 110 cm-l) confinement, and after 8 weeks of retraining using the same treadmill protocol 1 h/d for 6 d/week. Compared with control endurance (172 +/- 19 min), endurance decreased to 102 +/- 15 min (delta = -41%, p less than 0.05) after RA and increased to 223 +/- 24 min (delta = +30%, p less than 0.05) after training: the respective final levels and changes in rectal temperature were 41.25 and +2.15 degrees C, 41.60 and +2.70 degrees C (NS), and 41.35 and +2.40 degrees C (NS), respectively. Resting and post-exercise blood glucose and lactate concentrations were unchanged in the three experiments. After RA, resting muscle glycogen was reduced from a control level of 49.9 +/- 4.3 to 34.1 +/- 4.5 mmol.kg-1 (delta = 32%, p less than 0.05) which returned to the control level of 58.4 +/- 3.5 mmol.kg-1 after retraining. Resting plasma FFA levels were unchanged, but the RA post-exercise change was decreased from a control level of +0.400 +/- 0.099 to +0.226 +/- 0.039 mmol.L-1 (p less than 0.05). Neither restricted activity nor training affected glucose tolerance significantly. The results indicated that RA reduces exercise endurance, the effectiveness of exercise thermoregulation, muscle glycogen stores, and the lipolytic response to exercise and to noradrenaline stimulation. All these changes were reversed following 8 weeks of retraining.     

Tennis: a physiological profile during match play.

Heart rate (HR), hematocrit, hemoglobin, blood glucose, and plasma concentrations of lactate, cortisol, and testosterone were monitored in 10 male subjects (Division I, 20.3 +/- 2.5 yrs, VO2max: 58.5 +/- 9.4 ml.kg-1.min-1) during singles tennis and a treadmill test. During the on-court session, HR was 144.6 +/- 13.2 beats.min-1 for the 85 min of play. Plasma lactate rose 50% from a post-warmup value of 1.6 +/- 0.6 mmol.l-1 to 2.3 +/- 1.2 mmol.l-1 during play (p greater than 0.05). Blood glucose slightly decreased (8%, p greater than 0.05) from a pre-exercise value of 4.6 +/- 0.8 mmol.l-1 as a result of the 10-min warmup. This was followed by a 23% rise (p less than 0.05) from 4.2 +/- 1.0 mmol.l-1 to 5.2 +/- 0.6 mmol.l-1, measured after the first 30 min of play. Blood glucose subsequently remained steady at slightly above the pre-exercise value. Plasma cortisol rose (9%, p greater than 0.05) during the warmup and subsequently decreased (p less than 0.05) from a post-warmup value of 558.2 +/- 285.2 nmol.l-1 to 337.1 +/- 173.3 nmol.l-1 (a 40% decrease), and remained decreased during recovery. Plasma testosterone rose 22% (p less than 0.05) from pre-exercise to recovery (13.5 +/- 3.8 nmol.l-1 and 16.5 +/- 2.6 nmol.l-1, respectively). Although tennis is characterized by periods of high-intensity exercise, the overall metabolic response resembles prolonged moderate-intensity exercise.     

Effects of a moderate glycemic meal on exercise duration and substrate utilization

PURPOSE: To determine whether eating a breakfast cereal with a moderate glycemic index could alter substrate utilization and improve exercise duration. METHODS: Six active women (age, 24 +/- 2 yr; weight, 62.2 +/- 2.6 kg; VO(2peak), 46.6 +/- 3.8 mL x kg(-1) x min(-1)) ate 75 g of available carbohydrate in the form of regular whole grain rolled oats (RO) mixed with 300 mL of water or water alone (CON). The trials were performed in random order and the meal or water was ingested 45 min before performing cycling exercise to exhaustion (60% of VO(2peak)). Blood samples were drawn for glucose, glucose kinetics, free fatty acids (FFA), glycerol, insulin, epinephrine (EPI), and norepinephrine (NE) determination. A muscle biopsy was obtained from the vastus lateralis muscle before the trial and immediately after exercise for glycogen determination. Glucose kinetics (Ra) were determined using a [6,6-(2)H] glucose tracer. RESULTS: Compared with CON, plasma FFA and glycerol levels were suppressed (P < 0.05) during the first 120 min of exercise for the RO trial. Respiratory exchange ratios (RER) were also higher (P < 0.05) for the first 120 min of exercise for the RO trial. At exhaustion, glucose, insulin, FFA, glycerol, EPI, NE, RER, and muscle glycogen were not different between trials. Glucose Ra was greater (P < 0.05) during the RO trial compared with CON (2.36 +/- 0.22 and 1.92 +/- 0.27 mg x kg(-1) x min(-1), respectively). Exercise duration was 5% longer during RO, but the mean times were not significantly different (253.6 +/- 6 and 242.0 +/- 15 min, respectively). CONCLUSIONS: Increased hepatic glucose output before fatigue provides some evidence of glucose sparing after the breakfast cereal trial. However, exercise duration was not significantly altered, possibly because of the sustained suppression of lipid metabolism and increased carbohydrate utilization throughout much of the exercise period.     

Atropine: effects on glucose metabolism

We have employed the primed constant infusion technique to investigate the metabolic effects of the organophosphate antidote, atropine, on glucose homeostasis in rats. This method utilizes the radioisotopes 6-3H-glucose to measure production and uptake and U-14C-glucose to measure oxidation. Our data indicate that glucose production significantly (p less than 0.05) increased (24.0 +/- 2.0 vs. 30.9 +/- 2.6 mumoles.kg-1.min-1) following atropine administration. The elevated rate of glucose turnover was associated with concomitant increases in glucose oxidation (8.3 +/- 0.6 vs. 12.0 +/- 0.8, mumoles.kg-1.min-1), the percent of glucose uptake oxidized (37.2 +/- 2.0 vs. 44.6 +/- 2.6), and the percent carbon dioxide produced from glucose (8.4 +/- 0.7 vs. 12.0 +/- 1.8). Presumably, these glucokinetic changes were mediated by elevated plasma catecholamines (Epi: 166 +/- 19 vs. 271 +/- 50 pg/ml; Norepi: 262 +/- 24 vs. 525 +/- 63 pg/ml, p less than 0.05) since other glucoregulatory hormones (insulin, glucagon, and corticosterone) were not significantly affected by atropine administration. In addition, there was no change in VO2 associated with atropine administration. These data indicate that atropine enhances glucose production and utilization; such effects could be ergogenic during exercise in thermoneutral conditions.     

Effects of increasing insulin secretion on acute postexercise blood glucose disposal

BACKGROUND: Coingestion of protein and/or free amino acids with carbohydrate has been reported to accelerate postexercise muscle glycogen synthesis due to an increase in the insulin response. PURPOSE: To determine the extent to which the combined ingestion of carbohydrate and a casein protein hydrolysate with or without additional free leucine can increase insulin levels during postexercise recovery in endurance-trained athletes. To determine how this affects whole-body plasma glucose disposal during postexercise recovery. METHODS: Fourteen male athletes (age: 24.3 +/- 0.8 yr; VO2max: 62.9 +/- 1.4 mL.kg.min) were subjected to three randomized crossover trials in which they performed 2 h of exercise (55% Wmax). Thereafter, subjects were studied for 3.5 h during which they ingested carbohydrate (CHO: 0.8 g.kg.h), carbohydrate and a protein hydrolysate (CHO-PRO: 0.8 and 0.4 g.kg.h, respectively), or carbohydrate, a protein hydrolysate, and free leucine (CHO-PRO-LEU: 0.8, 0.4, and 0.1 g.kg.h, respectively) in a double-blind fashion. Continuous infusions with [6,6-H2] glucose were applied to quantify plasma glucose appearance (Ra) and disappearance rates (Rd). RESULTS: Plasma insulin responses were 108 +/- 17 and 190 +/- 33% greater in the CHO-PRO and CHO-PRO-LEU trial, respectively, compared with the CHO-trial (P < 0.01). Plasma glucose responses were lower in the CHO-PRO and CHO-PRO-LEU trial compared with the CHO-trial (35 +/- 5 and 42 +/- 11% lower, respectively; P < 0.01). Plasma glucose Ra and Rd were greater in the CHO versus the CHO-PRO and CHO-PRO-LEU trials (P < 0.05). Glucose Rd represented 100 +/- 0.03% of Ra in all trials. CONCLUSIONS: The combined ingestion of a protein hydrolysate and/or free leucine with carbohydrate (0.8 g.kg.h) substantially augments insulin secretion, but does not affect plasma glucose disposal during the first 3.5 h of postexercise recovery in trained athletes.     

Roux-en-Y胃转流术对GK大鼠炎症因子与胰岛素抵抗影响的实验研究

目的探讨Roux-en-Y胃转流术对自发糖尿病GK大鼠炎症因子与胰岛素抵抗的影响及其意义。方法 40只GK大鼠随机平均分为手术组与对照组。手术组行Roux-en-Y胃转流术,对照组行胃窦十二指肠离断后原位吻合术。分别于术前,术后1、2、4周动态检测两组大鼠血液中空腹血糖、口服葡萄糖耐量试验(OGTT)2 h血糖,空腹胰岛素;并于术前及术后4周测定大鼠血液中游离脂肪酸(free fatty acids,FFA)、肿瘤坏死因子α(TNF-α)、C-反应蛋白(CRP),计算胰岛素抵抗指数(HOMA-IR)。结果手术组术后空腹及OGTT2h血糖值均呈明显的下降趋势,至术后第4周时其血糖值显著低于术前(9.8±2.6)mmol/L降至(7.3±2.2)mmol/L及OGTT2h血糖(27.3±3.1)mmol/L降至(23.6±3.4)mmol/L(P<0.05);对照组手术前后空腹及OGTT2h血糖值无显著变化(P>0.05)。术后第4周,手术组大鼠血液FFA较术前显著降低(204.2±55.6)umol/L降至(179.4±32.54)umol/L(P<0.05);术后4周血中TNF-α的含量较术前显著降低(32.4±1.3)pg/ml降至(24.9±1.0)pg/ml(P<0.01);术后4周CRP的含量显著低于术前(648.5±36.23)ng/ml降至(32.9±37.8)ng/ml(P<0.01);而手术前后空腹胰岛素水平无显著变化(P>0.05),其HOMA-IR指数较术前显著降低(8.46±1.66降至5.20±0.79)(P<0.05);而对照组术后4周上述指标无显著差异(P>0.05)。结论 Roux-en-Y胃转流术能显著降低GK大鼠的血糖,其可能机制是手术后通过降低体内游离脂肪酸含量,导致炎症因子释放减少,从而使胰岛素抵抗得到缓解。     

Substrate and hormone responses to exercise following a marathon run

The aim of this study was to examine selected substrate and hormone responses to 30-min treadmill runs performed several days before and after a competitive marathon (42.2 km) to determine the time course for return of altered responses to pre-race levels. Six experienced male runners (30.8 +/- 9.1 years) ran at their predicted race pace (77.1% +/- 4.1% of VO2max) 8-7 days prior (S-1) to the Boston Marathon and 2-3 (S-2), 6-7 (S-3), and 13-14 days (S-4) post-marathon. All 30-min runs were performed in the morning at a constant time for each subject following a 12-h fast. Blood samples were drawn immediately before and immediately after (within 1 min) the 30-min runs. Post-exercise glucose responses were higher (P less than 0.05) during S-2 and S-3 compared with S-1 values. S-2 post-exercise lactate concentrations were also higher than the corresponding S-1 value. Pre-exercise free fatty acid (FFA) levels during S-4, and the post-exercise FFA values during S-2, S-3, and S-4, were lower (P less than 0.05) than the corresponding S-1 concentrations. Pre- and post-exercise alanine levels during S-2 were higher (P less than 0.05) than the S-1 values. Both pre- and post-exercise insulin levels during S-2, S-3, and S-4 were greater (P less than 0.05) than corresponding S-1 concentrations. Glucagon concentrations were unchanged across all sessions.(ABSTRACT TRUNCATED AT 250 WORDS)     

Oxidation of exogenous carbohydrate during prolonged exercise in fed and fasted conditions

The oxidation of glucose and fructose ingested during moderate exercise performed on a cycle ergometer (120 min, 52% VO2max) was compared in ten young males fasted (n = 5) or fed (n = 5) before exercise. The subjects ingested randomly 1.33 g/kg body weight (approximately 96 +/- 9 g) of either enriched 13C-glucose (G), 13C-fructose (F), or water only (W); the solutions were evenly distributed over the exercise period. The fasted subjects began the three exercises with a lower blood glucose (P less than or equal to 0.05 for F only) and insulin (P less than or equal to 0.05) levels and a higher free fatty acid (FFA) concentration (P less than or equal to 0.05) than the fed ones. Throughout the exercise period, blood glucose level was maintained in fasted as well as in fed group for G and F ingestions, while it decreased (P less than or equal to 0.05 at the 100th min in fasted subjects) with water ingestion. Insulin level was similar in both fed and fasted conditions with F and W ingestions and lower than G trials for the fed subjects. For the three ingestions, FFA was lower (P less than or equal to 0.05) in the fasted than in the fed group over the exercise period. Over the 2-h period of exercise, a greater (P less than or equal to 0.05) amount of exogenous F was oxidized in the fasted (49 +/- 6 g) than in the fed (36 +/- 5 g) group, which represent 31% and 20% of the total carbohydrate energy supply, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)     

The effect of a preexercise meal on time to fatigue during prolonged cycling exercise

PURPOSE AND METHODS: Seven subjects exercised to exhaustion on a bicycle ergometer at a workload corresponding to an intensity of 70% maximal oxygen uptake (VO2max). On one occasion (FED), subjects consumed a preexercise carbohydrate (CHO) containing breakfast (100 g CHO) 3 h before exercise. On the other occasion (FASTED), subjects exercised after an overnight fast. Exercise time to fatigue was significantly longer (P < 0.05) when subjects consumed the breakfast (136+/-14 min) compared with when they exercised in the fasted state (109+/-12 min). RESULTS: Pre- and post-exercise muscle glycogen concentrations, respiratory exchange ratio, carbohydrate and fat oxidation, and lactate and insulin concentrations were not significantly different between the two trials. Insulin concentrations decreased significantly (P < 0.05) from 4.7+/-0.05 microIU.mL(-1) to 2.8+/-0.4 microIU.mL(-1) in FED and from 6.6+/-0.6 microIU.mL(-1) to 3.7+/-0.6 microIU.mL(-1) in FASTED subjects and free fatty acid concentrations (FFA) increased significantly (P < 0.05) from 0.09+/-0.02 mmol.L(-1) to 1.4+/-0.6 mmol.L(-1) in FED and from 0.17+/-0.02 mmol.L(-) to 0.74+/-0.27 mmol.L(-1) in FASTED subjects over the duration of the trials. CONCLUSIONS: In conclusion, the important finding of this study is the increased time to fatigue when subjects ingested the CHO meal with no negative effects ascribed to increased insulin concentrations and decreased FFA concentrations after CHO ingestion.     

The influence of ubiquinone (Co Q10) on the metabolic response to work

Ubiquinone (Co Q10) is a natural substance suitable for therapeutic use in cardiology and in the treatment of some muscular diseases. It might therefore be used during strenuous exercise (as in athletic competitions), especially in the presence of metabolic modifications which may justify its use. For this purpose, we have evaluated the effect of prolonged treatment with Co Q10 (100 mg/day per os for one month) on the biological changes induced by prolonged work on an ergometer bicycle (equal to about 50% of the single VO2max per 60 m'), immediately followed by exhaustive work (25 watts increase every 2 m'). From the venous blood of 12 healthy untrained subjects (students, volunteers, mean age 25.7 and body mass index 23.3) we examined some biological parameters [free fatty acids (FFA), free glycerol, lactate, glucose, insulin, CK] before, at the end of aerobic work, at the end of exhaustive work, and after 30 and 60 m' of the recovery phase. The same indexes, measured after identical times and work, were evaluated after one month of treatment with Co Q10. The only relevant modifications observed were those concerning FFA: at the end of aerobic work and after the administration of the drug, lower levels were reached (before, 1011 +/- 329 microEq/l; after 790 +/- 392; p less than 0.05); the same trend was observed at the end of the exhaustive work (1031 +/- 320 microEq/l vs 826 +/- 387; p less than 0.05). At the subsequent times, as well as for the other biological parameters examined, we did not observe any variation before or after the period of treatment.(ABSTRACT TRUNCATED AT 250 WORDS)     

Influence of liquid and solid meals on muscle glycogen resynthesis, plasma fuel hormone response, and maximal physical working capacity

The effect of forced liquid (L) or solid (S) carbohydrate (CHO)-rich feedings on plasma glucose, insulin, and glycogenesis after glycogen depletion was investigated. The relationship between glycogen restoration and maximal physical working capacity (MPWC) was studied as well. Eight males performed two experiments, with 2 weeks interval, on a bicycle ergometer. In each experiment, MPWC was determined in a graded test, which was immediately followed by interval work until exhaustion. After exercise cessation (EC), the subjects started to consume a standardized amount of concentrated L or CHO-rich food. Insulin and glucose concentration in blood were determined. Muscle glycogen was determined before, immediately after, 5 h after, and 22 h after EC. MPWC was determined again 22 h after EC. Four subjects performed a third experiment, in which solid food consumption was left ad libitum (AL). A rapid glycogen repletion was found 5 h after EC, i.e., from 72 +/- 40 to 198 +/- 38 mmol/kg in the S, and from 69 +/- 39 to 192 +/- 40 mmol/kg in the L experiment. The higher plasma glucose and insulin levels (P less than 0.05) during the 5 h after EC in the S experiments did not elicit a difference in glycogen repletion. Glycogen synthesis rate in the AL experiment was lower (P less than 0.05) than in the L and S experiments. Glycogen restoration in the L and S experiments was complete 22 h after depletion. However, despite repletion of glycogen, MPWC was decreased (P less than 0.05) in both experiments.(ABSTRACT TRUNCATED AT 250 WORDS)     

Fat storage in athletes: metabolic and hormonal responses to swimming and running

Despite similar rates of energy expenditure during training, it has been suggested that swimmers store greater amounts of body fat than runners. To investigate these discrepancies, eight male swimmers (S) and runners (R) were monitored during 45 min of swimming or running (75% VO2max), respectively, and six triathletes were monitored during swimming (ST) and running (RT). Each group was also monitored during two hours of recovery. Venous blood samples were obtained before exercise, immediately after exercise (0 min) and at 15, 30, 60 and 120 min of recovery. These samples were analyzed for glucose, lactate, glycerol, free fatty acids (FFA), insulin, glucagon, norepinephrine (NE) and epinephrine (E). Expired gases and heart rates (HR) were obtained during exercise and also during recovery. The caloric cost of recovery was similar, but the RER results suggested increased fat oxidation during recovery for the S and the ST. Serum glucose was greater (P less than 0.05) immediately after exercise for R (6.71 +/- 0.29 mmol/l) and RT (6.40 +/- 0.26) compared to the S (4.97 +/- 0.19) and ST (4.87 +/- 0.18), and was significantly elevated for the initial 30 min of recovery. FFA were similar throughout the recovery period; however, blood glycerol was greater immediately after exercise (0 min) for R compared to S (NS) and was significantly elevated after exercise (0 min) for RT compared to ST. Differences in blood glucose or fat release were not explained by differences in NE or E; however, the glucacon-to-insulin ratio was significantly greater after exercise in the S and ST compared to the R and RT.(ABSTRACT TRUNCATED AT 250 WORDS)     

Atrial natriuretic factor during hypoxia and mild exercise

The effect of hypoxia on plasma atrial natriuretic factor (ANF), plasma renin activity (PRA), and plasma aldosterone concentration (PAC) was evaluated during 2 h of treadmill exercise at 2 km/h, 0 grade at sea level. Six male subjects exercised on 2 separate days during normoxia (21% O2) and hypoxia (13.3 +/- 0.3% O2). No significant changes in ANF or PRA occurred during either normoxic or hypoxic exercise. However, PAC fell significantly during normoxic exercise (17.5 +/- 3.6 vs. 12.7 +/- 2.6 ng/dl, p less than 0.05) but not during hypoxic exercise. Serum potassium concentration fell during hypoxic exercise (5.0 +/- 0.1 vs. 4.4 +/- 0.1 mmol/l, p less than 0.05) along with bicarbonate (27.8 +/- 0.7 vs. 25.8 +/- 0.6 mmol/l, p less than 0.01). Between normoxic and hypoxic studies there was a significantly higher heart rate during hypoxic exercise (78 +/- 5 vs. 90 +/- 6 b/min, p less than 0.01). The major conclusion of this study is that hypoxia resulting in arterial oxygen saturations of 81 +/- 0.7% does not affect plasma atrial natriuretic factor levels during mild exercise in normal male subjects.     

The effect of food matrix on carbohydrate utilization during moderate exercise.

The effect of food matrix on carbohydrate utilization during moderate exercise. Med. Sci. Sports Exerc., Vol. 24, No. 3, pp. 320-326, 1992. To determine the effect of food type and form on the rate of assimilation and utilization of a meal given before exercise, five physically active adult males walked for 4 h on a 10% uphill graded treadmill at 40% VO2max. After a 12-h fast, and 30 min before exercise, subjects ingested 70 g of liquid glucose (G), a refined "hot cereal" (R), a refined "hot cereal" with water-soluble fiber (R/F), an oat bar (O), or placebo (P). Meals R/F, R, and O had significantly lower (P less than 0.05) peak plasma glucose responses than meal G (0.8, 0.9, 1.0, and 2.4 mmol.l-1, respectively). Meals R, O, and R/F had significantly lower (P less than 0.01) peak insulin responses than meal G (135, 150, 190, and 340 pmol.l-1, respectively). All meals except P contained an extrinsic tracer of 200 mg UL-13C-glucose. Mean (+/- SD) total recovery of the administered dose of 13C for all meals was 81 +/- 2%. Both O (34 +/- 4% dose.h-1) and R/F (30 +/- 3% dose.h-1) had significantly lower peak recoveries than did meal G (41 +/- 5% dose.h-1). Meal R/F had a significantly lower (P less than 0.05) rate of exogenous glucose oxidation than meal G during the first hour of exercise. These data suggest that meal R/F slows the rate of assimilation and utilization of exogenous glucose, but does not alter the cumulative 4-h utilization.