The impact of prolonged strenuous endurance exercise on interleukin 18 and interleukin 18 binding protein in recreational cyclists

Interleukin 18 (IL-18) is an important pro-inflammatory cytokine in the early phase of human immune response to microbial infections. The influence of strenuous exercise on the intrinsic balance of IL-18 and its endogenous antagonist IL-18 binding protein (IL-18 BP) is unknown, but could be of major relevance for the athlete's immune function empirically and epidemiologically proven to be altered after exhaustive exertion. To study the effect of strenuous marathon cycling on the interaction of IL-18 and IL-18 BP we investigated 37 male, healthy, and well-trained amateur cyclists participating in the Otztaler Radmarathon in Tyrol (distance: 230 km; cumulative altitude difference: 5500 m). IL-18 was measured by a commercially available ELISA-Kit and IL-18 BP by a novel IL-18 BP ELISA method. Free, unbound IL-18 was calculated according to a standard equation. The mean plasma level of IL-18 was 142.27 +/- 21.85 pg/ml pre-race, remained nearly unchanged (124.35 +/- 13.16 pg/ml; p = 1.0) immediately after competition (mean race time 9 h 38 min), but declined significantly 24 h afterward (62.92 +/- 6.80 pg/ml; p = 0.002). The plasma levels of IL-18 BP increased considerably immediately after and kept on rising for the following 24 h (pre-race: 1.51 +/- 0.20 ng/ml; immediately post-race: 3.84 +/- 0.26 ng/ml, p < 0.001; 24 h post-race: 4.33 +/- 0.42 ng/ml, p < 0.001). Therefore, the calculated free IL-18 was 122.06 +/- 16.79 pg/ml pre-race, declined to 82.86 +/- 8.59 (p = 0.05) immediately post-race and to 39.17 +/- 3.76 pg/ml 24 h post-race (p < 0.001). The respective percentages of this post-exercise reduction in free IL-18 plasma levels were 32 % and 68 %. The present study reveals an exercise-induced significant decline in free IL-18 accompanied by an immediate up-regulation of IL-18 BP and decreased IL-18 in marathon cyclists. This down-regulation of free IL-18 may (i) limit the magnitude and duration of a too excessive inflammatory response to the exercise-induced tissue damage and (ii) on the other hand contribute to the elevated susceptibility to infection in athletes undergoing exhaustive exercise.     

Biochemical changes as a result of prolonged strenuous exercise

OBJECTIVE: To briefly review biochemical changes that may result from prolonged strenuous exercise and to relate these changes to health risk. METHODS: Medline and Sports Discus databases were searched for relevant articles. Additional articles were found using cross referencing and the authors' knowledge of the subject area. RESULTS: Prolonged strenuous exercise may result in a series of biochemical changes that are of concern from a health point of view. Generally, these changes are benign, but some, especially hyponatraemia, are potentially life threatening occurrences. CONCLUSION: Doctors and athletes should be aware of the potentially adverse biochemical changes, especially hyponatraemia, that may result from prolonged strenuous exercise.     

Effects of short-term strenuous endurance exercise upon corpus luteum function.

PURPOSE: The present study tested whether short-term, abruptly initiated training can cause corpus luteum dysfunction when exercise is limited to either the follicular or luteal phase of the cycle. METHODS: Reproductive hormone excretion and menstrual characteristics were studied in sedentary women who exercised only during the follicular (N = 5) or the luteal (N = 4) phase. Six women served as controls, three of whom exercised at a low volume and three who remained sedentary. Weekly progressive increments in exercise volume continued until either ovulation (follicular group) or menses (luteal group) occurred. Physical activity and nutrient intake were closely monitored with the intent to maintain body weight. RESULTS: No luteal phase disturbances occurred in any of the control subjects, whereas 40% of follicular and 50% of luteal exercisers experienced luteal defects. The proportion of menstrual cycles disrupted was not different between luteal and follicular exercisers (50% vs 30%, respectively) but was significantly greater than the proportion of cycles disrupted in control subjects (P < 0.05). CONCLUSIONS: These results suggest that exposure to abrupt onset of training can alter luteal function, regardless of the menstrual cycle phase in which exercise occurs. This study also demonstrates that a relatively low volume of exercise suffices to induce mild disturbances in luteal function.     

Impaired left ventricular diastolic function in athletes after utterly strenuous prolonged exercise

Digitized M mode echocardiography was used to evaluate the effect of a competitive 24-h run on the left ventricular diastolic function in 12 well-trained marathon runners who completed 146-227 km during the race. Mitral valve opening was delayed, early diastolic filling was decreased and prolonged, and posterior wall thinning was reduced, particularly among those athletes completing close to 200 km or more. Since the alterations were in part the opposite in those running 160 km or less, only the reductions in the peak rate of dimension increase (P less than 0.05) and posterior wall thinning (P less than 0.01) were significant in the group as a whole. The delay in mitral valve opening (r = 0.76), the decrease in the peak rate of dimension increase (r = -0.68), and the prolongation of the early diastolic filling period (r = 0.60) were correlated with the distance completed. The reductions in left ventricular end-diastolic dimension and fractional shortening were not in proportion to the distance run, however (r = 0.23 and 0.46, respectively). Measurements made on six athletes 2-3 days after the race showed reversal of the indices of left ventricular diastolic function. Extremely exhaustive prolonged exercise thus appears to result in a marked reversible impairment in left ventricular relaxation and filling. Since the effect of these abnormalities in cardiac filling during exercise is probably more important due to the shorter diastole, the prevention of hypohydration, which could otherwise further compromise left ventricular filling, becomes crucial.     

Cardiac fatigue following prolonged endurance exercise of differing distances

PURPOSE: Recent echocardiographic studies have reported cardiac dysfunction following ultra-endurance exercise in trained individuals. The duration of exercise required to elicit cardiac dysfunction and the mechanisms underlying this phenomenon have not been fully elucidated. The aim of the present study was to examine the presence of cardiac dysfunction following a half-Ironman and Ironman triathlon in trained individuals. METHODS: 14 male triathletes (age: 32 +/- 5 yr; height: 180 +/- 8 cm; body mass: 75 +/- 9 kg) completed a half-Ironman triathlon. Following a 4-wk period, 10 of the original 14 triathletes completed an Ironman triathlon. All triathletes were assessed using ECG, echocardiography, and blood analysis pre-, immediately post-, and 48 h postrace for both distances. RESULTS: Echocardiographic results indicated diastolic and systolic left ventricular dysfunction, for both race distances, which were associated with altered relaxation characteristics and a reduced inotropic contractility, respectively. Following 48-h recovery, all echocardiographic measures were similar to resting values. Creatine kinase MB (CKMB) was significantly elevated immediately postrace for both distances; however, it accounted for less than 5% of the total CK value and in the presence of an elevated total CK and CKMM implied that the elevated CKMB was noncardiac in origin. Troponin-T, however, was significantly elevated immediately postrace for both distances and returned to normal following 48-h recovery indicating myocardial damage. CONCLUSIONS: Ironman and half-Ironman competition resulted in reversible abnormalities in resting left ventricular diastolic and systolic function. Results suggest that myocardial damage may be, in part, responsible for cardiac dysfunction, although the mechanisms responsible for this cardiac damage remain to be fully elucidated.     

Oxidation of carbohydrate ingested during prolonged endurance exercise.

Classic studies conducted in the 1920s and 1930s established that the consumption of a high carbohydrate (CHO) diet before exercise and the ingestion of glucose during exercise delayed the onset of fatigue, in part by preventing the development of hypoglycaemia. For the next 30 to 40 years, however, interest in CHO ingestion during exercise waned. Indeed, it was not until the reintroduction of the muscle biopsy technique into exercise physiology in the 1960s that a series of studies on CHO utilisation during exercise appeared. Investigations by Scandinavian physiologists showed that muscle glycogen depletion during prolonged exercise coincided with the development of fatigue. Despite this finding, attempts to delay fatigue during prolonged exercise focused principally on techniques that would increase muscle glycogen storage before exercise. The possibility that CHO ingestion during exercise might also delay the development of muscle glycogen depletion and hence, at least potentially, fatigue, was not extensively investigated. This, in part, can be explained by the popular belief that water replacement to prevent dehydration and hyperthermia was of greater importance than CHO replacement during prolonged exercise. This position was strengthened by studies in the early 1970s which showed that the ingestion of CHO solutions delayed gastric emptying compared with water, and might therefore exacerbate dehydration. As a result, athletes were actively discouraged from ingesting even mildly concentrated (greater than 5 g/100ml) CHO solutions during exercise. Only in the early 1980s, when commercial interest in the sale of CHO products to athletes was aroused, did exercise physiologists again begin to study the effects of CHO ingestion during exercise. These studies soon established that CHO ingestion during prolonged exercise could delay fatigue; this finding added urgency to the search for the optimum CHO type for ingestion during exercise. Whereas in the earlier studies, estimates of CHO oxidation were made using respiratory gas exchange measurements, investigations since the early 1970s have employed stable 13C and radioactive 14C isotope techniques to determine the amount of ingested CHO that is oxidised during exercise. Most of the early interest was in glucose ingestion during exercise. These studies showed that significant quantities of ingested glucose can be oxidised during exercise. Peak rates of glucose oxidation occur approximately 75 to 90 minutes after ingestion and are unaffected by the time of glucose ingestion during exercise. Rates of oxidation also appear not to be influenced to a major extent by the use of different feeding schedules.(ABSTRACT TRUNCATED AT 400 WORDS)     

Reduction in LBNP tolerance following prolonged endurance exercise training.

Eight young men underwent an 8-month endurance exercise training program. Prior to and following the training program, the subjects' maximal oxygen uptake (VO2max), total blood volume (TBV) and plasma volume (PV), tolerance to lower body negative pressure (LBNP) assessed by the cumulative stress index (CSI) to presyncope, and their hemodynamic responses to 0 to -45 torr LBNP was determined. Hemodynamic measures included rebreathe carbon dioxide cardiac output (Qc), heart rate (HR), directly measured arterial blood pressures (ABP), and strain gauge determination of forearm blood flow (FBF) and leg volume changes (delta LgV). Calculated values of stroke volume (SV), forearm, vascular resistance (FVR), and peripheral vascular resistance (PVR) were made. Following training, each subject had an increased VO2max (mean = +27.4%, P < 0.001), TBV (mean = +15.8%, P < 0.02), and PV (mean = +16.5%, P < 0.02) and each subject had a decreased tolerance to LBNP (mean CSI = -24%, P < 0.001). Stepwise linear regression identified that the major factors to significantly predict the decreased CSI pre- to post-training were a reduced response of PVR to LBNP from -15 to -45 torr (Model R2 = 0.853), the delta TBV (model R2 = 0.981), and the greater post-training reduction in SBP to LBNP of 0 to -45 torr (model R2 = 1.0). These data suggest that physiologic adaptations associated with the increased VO2max and TBV resulting from a prolonged endurance exercise training program can alter the reflex control of vasomotion and cardiac output during LBNP and reduce the LBNP tolerance.     

Effect of glycerol feeding on endurance and metabolism during prolonged exercise in man

This study evaluated the effectiveness of pre-exercise glycerol feeding in protecting against development of hypoglycemia and sparing muscle glycogen during prolonged, intense exercise. Thirty minutes after ingesting either glycerol (1 gm X kg-1 body weight) or a placebo, 10 cyclists performed as much exercise on a cycle ergometer as they were able in 150 min. The average exercise intensity was 72% of VO2max during both trials. Glycerol ingestion increased blood glycerol concentration 100-fold, but did not alter the respiratory exchange ratio (R), plasma levels of insulin and free-fatty acids, or blood lactate and beta-hydroxybutyrate. The only significant effect of glycerol feeding was to postpone the decline in blood glucose by about 30 min. This suggests that glycerol served, to a limited extent, as a gluconeogenic substrate; however, glycerol ingestion did not spare muscle glycogen during 90 min of treadmill exercise at 71% VO2max. It appears that man cannot utilize glycerol as gluconeogenic substrate rapidly enough to serve as a major energy source during strenuous exercise.     

Salivary IgA response to prolonged exercise in a cold environment in trained cyclists

PURPOSE: The purpose of the present study was to determine the effect of a prolonged bout of exercise in freezing cold conditions on saliva immunoglobulin A (s-IgA) responses in endurance-trained males. METHODS: Using a randomized cross-over design, 15 trained male cyclists cycled for 2 h on a stationary ergometer at 70% VO(2max) in an environmental chamber on one occasion at a temperature of -6.4 +/- 0.1 degrees C (cold) and on another occasion at a temperature of 19.8 +/- 0.2 degrees C (control). Trials began at 12:30 h to avoid the fall in s-IgA concentration that occurs during the morning hours. Unstimulated whole-saliva samples were collected over a 2-min period at preexercise, postexercise, and 2-h postexercise. The s-IgA concentration was determined using a sandwich-type ELISA method. RESULTS: Saliva flow rate decreased postexercise by 31%, returning to preexercise levels by the 2-h postexercise collection (main effect of time: < 0.01). The decrease in saliva flow rate postexercise in the control trial (39% compared with 22% on cold trial) approached significance (interaction: = 0.08) and may have accounted for the corresponding increase in s-IgA concentration postexercise in the control trial (s-IgA concentration: control preexercise; 91 +/- 12; postexercise; 110 +/- 13 mg x L(-1); < 0.05). Saliva IgA secretion rate decreased postexercise by 19.5% returning to preexercise levels by 2-h postexercise measure (main effect of time: < 0.05). CONCLUSIONS: These data show that performing a bout of prolonged exercise results in a reduction in s-IgA secretion rate. Additionally, these data demonstrate that performing prolonged exercise in freezing cold conditions does not influence saliva flow rate or s-IgA secretion rate responses to prolonged exercise.     

The effects of exercise training intensification on glucose disposal in elite cyclists

To assess the effect of training on glucose disposal, we performed a longitudinal study of 11 elite cyclists before and after 4 months of intensive training compared to 11 sedentary subjects. Insulin sensitivity (SI) and glucose effectiveness (Sg) were measured using Bergman's minimal model. Sg includes basal insulin effectiveness (BIE) and a parameter termed glucose effectiveness at zero insulin (GEZI). After overnight fasting glucose was administered intravenously (0.5 g x kg(-1), 30% solution given over 3 min), and insulin (0.02 U x kg(-1), 1 -2U) was injected immediately after 19 min. Sg, SI and BIE, were significantly higher in elite cyclists both before and after training than in sedentary subjects (P < 0.01). However, the non-insulin-dependent component of Sg (GEZI) was higher only after the intensive training in the cyclists (3.31 +/- 0.67% x min(-1)) than in sedentary subjects (1.7 +/- 0.2% x min(-1), P < 0.02). We conclude that insulin sensitivity (SI) and glucose effectiveness (Sg) are higher in elite cyclists than in sedentary subjects and that these high and almost optimal values are not further improved by additional training. However, the improvement in GEZI, as reflected by the difference between post-training GEZI and sedentary control values, raises the possibility of an increase of the non-insulin-mediated mobilization of glucose transporters.     

Effects of strenuous exercise on haemostasis

OBJECTIVES: To review the effects of exercise on haemostasis and examine the possible clinical sequelae of these changes. METHODS: The search strategy included articles from 1966 to August 2002 using Medline and SportDiscus databases, and cross referencing the bibliographies of relevant papers. RESULTS: Exercise results in activation of both the coagulation and fibrinolytic cascades, as shown by a reduction in whole blood clotting time and activated partial thromboplastin time, an increase in the activity of several components of the cascades, and an increase in fibrin degradation products. In vitro tests suggest that coagulation remains activated after fibrinolysis has returned to baseline levels. CONCLUSIONS: Both the coagulation and fibrinolytic cascades are stimulated by strenuous exercise, but the temporal relation between the two and its clinical significance remains to be clarified. Doctors and athletes should be aware of the haemostatic changes induced by exercise, and further work is needed to clarify the possible role of these changes in sudden cardiac death.     

Caffeine effects on short-term performance during prolonged exercise in the heat

PURPOSE: To determine the effect of water, carbohydrate, and caffeine ingestion on fatigue during prolonged exercise in the heat. METHODS: Seven endurance-trained cyclists (V O2max = 61 +/- 8 mL.kg.min) pedaled for 120 min at 63% V O2max in a hot-dry environment (36 degrees C; 29% humidity), ingesting either no fluid (NF), water (WAT) to replace 97% fluid losses, the same volume of a 6% carbohydrate-electrolyte solution (CES), or each of these treatments along with ingestion of 6 mg of caffeine per kilogram of body weight (NF + CAFF, WAT + CAFF, and CES + CAFF). At regular intervals during exercise, maximal cycling power (PMAX) was measured. Before and after exercise, maximal voluntary contraction (MVC), voluntary activation (VA), and electrically evoked contractile properties of the quadriceps were determined. RESULTS: Without fluid replacement (NF and NF + CAFF), subjects were dehydrated by 3.8 +/- 0.3%, and rectal temperature reached 39.4 +/- 0.3 degrees C, while it was maintained at 38.7 +/- 0.3 degrees C in trials with rehydration (P < 0.05). Trials with caffeine ingestion increased PMAX by 3% above trials without caffeine (P < 0.05). MVC reductions after exercise were larger with NF (-11 +/- 5%) than for the rest of the trials (P < 0.05). MVC was reduced in WAT compared with CES + CAFF (-6 +/- 4 vs 2 +/- 4%; P < 0.05). However, NF + CAFF maintained MVC at the level of the CES trial. VA showed the same treatment response pattern as MVC. There were no differences in electrically evoked contractile properties among trials. CONCLUSION: During prolonged exercise in the heat, caffeine ingestion (6 mg.kg body weight) maintains MVC and increases PMAX despite dehydration and hyperthermia. When combined with water and carbohydrate, caffeine ingestion increases maximal leg force by increasing VA (i.e., reducing central fatigue).     

Effect of hyperoxic-supplemented interval training on endurance performance in trained cyclists

The aim of this study was to determine the effect of hyperoxic-supplemented interval training on endurance performance. Using a single-blind, randomised control-trial design, 16 well-trained cyclists were randomly assigned to either hyperoxic or normoxic training. Participants visited the laboratory twice per week, for 4 weeks, to perform high-intensity interval training sessions. A 20 km TT, incremental exercise test and 60s all-out test were conducted pre- and post-intervention. Smaller effects for most physiological measures, including VO 2peak (1.9 ± 4.3%) and lactate threshold (0.3 ± 8.3%), were observed after training in hyperoxia compared to normoxia. There was a small increase in mean power during the 20 km TT after hyperoxia [2.1 ± 3.7%; effect size (ES): - 0.30 ± 0.39] but this was less than that observed after normoxia (4.9 ± 3.9%; ES: - 0.44 ± 0.60). During the 60 s all-out test, the peak relative power was relatively unchanged, whereas mean relative power was increased in normoxia (2.3 ± 3.4%) but not hyperoxia (0.3 ± 1.2%; ES: - 0.34 ± 0.49). Hyperoxic-supplemented interval training in the competitive season had less effect on endurance and high-intensity performance and physiology in trained endurance cyclists compared to interval training in normoxia. Therefore hyperoxic-supplemented training at sea level appears to be not worthwhile for maximising performance in competitive endurance athletes.     

Effects of respiratory muscle endurance training on ventilatory and endurance performance of moderately trained cyclists

This study examined the effects of respiratory muscle endurance training (RMET) on ventilatory and endurance performance among moderately trained, male cyclists. Nine subjects initially completed two cycling VO2 max tests, two endurance cycling tests for time at 95% VO2 max, a 15-s MVV test, and an endurance breathing test for time at 100% MVV. Four subjects then underwent 3 weeks of strenuous RMET while five served as controls. Mean posttest 15-s MVV and endurance breathing time were significantly higher in the RMET group (243 +/- 14 l X min-1 and 804 +/- 94 s) than in the control group (205 +/- 6 l X min-1 and 48 +/- 8 s). No significant group differences in VO2 max or endurance cycling time at 95% VO2 max were observed following RMET. Results of this exploratory study indicated that RMET improved ventilatory power and endurance, but did not alter VO2 max or endurance cycling performance among moderately trained, male cyclists.     

Prolonged visual reaction time after strenuous endurance exercise: higher increment in male compared to female recreational runners

Purpose

This project aimed to evaluate the simple visual reaction time (SVRT) changes in runners of both sexes before and after a 21.1 km run.

Methods

20 male (age 35.3?±?17.1 years, BMI 23.5?±?3.3 kg/m²) and 20 female (age 32.2?±?14.3 years, BMI 24.8?±?4.2 kg/m²) amateur runners were evaluated 30 min before and after a half-marathon run under competing conditions. Subjects were asked to push an electronic switch at the lighting of a lamp for 11 trials randomly divided to one another between 1 and 10 s. Effort-perception data were collected through a Borg CR100 scale and SVRT data using an electronic chronometric device. A two-way RM ANOVA assessed the effects of exercise and biological sex on SVRT.

Results

Borg effort data were similar (M: 82.4?±?3.9 vs W: 84.7?±?4.9 AU, p?=?0.68). SVRT was lower in men than women before (M: 234.05?±?3.33 vs F: 239.47?±?6.1 ms, p?<?0.05) but not after the race (M: 249.9?±?7.18 vs F: 252.09?±?16.93 ms, p?=?0.7). Exercise lengthened the SVRT (M:?+?7%; F:?+?5%; p?<?0.05). Response accuracy was greater in men both before and after exercise.

Conclusion

Previous studies suggested exercise lengthened SVRT due to an exercise intensity-related reduced post-exercise cerebral oxygenation that decreases cognitive processes efficiency. In our results, this reduction seemed higher in men. The sex-related response accuracy might be due to different estrogen effects in brain areas implicated in information processing, motor performance, and attention and to different processing and attention focus strategies between the sexes or anticipatory strategies in females.

     

Effects of strenuous exercise on myocardial blood flow

Myocardial blood flow is the major determinant of oxygen delivery to the myocardium, since oxygen extraction by the myocardium is near maximum in the resting state. Regulation of flow during exercise depends on local metabolic factors and, to a small extent, on autonomic tone. Maximum flow of 5-6 times resting has been measured in reactive hyperemia experiments. In strenuous exercise, myocardial oxygen delivery appears to be adequate and flow reserve seems capable of handling the increased oxygen demand. No evidence of myocardial failure in normal hearts due to excess exercise has been presented. However, pulmonary hemorrhages found in horses after strenuous racing may be due to inadequate cardiac performance at maximal capacity. In humans, severe limitations to myocardial blood flow are imposed by coronary artery disease and by cardiac hypertrophy. In both cases regional myocardial ischemia may occur during the increased oxygen demands imposed by strenuous exercise. Individuals with coronary disease or cardiac hypertrophy are at risk for myocardial ischemia during exercise. Detection of myocardial blood flow abnormalities and ischemia during exercise has become an important goal in cardiac diagnosis. Prevention of serious or lethal consequence of strenuous exercise depends on a better understanding of the factors that regulate myocardial blood flow during ischemia.