Effect of caffeine and ephedrine ingestion on anaerobic exercise performance

PURPOSE: Ingestion of a combination of caffeine (C) and ephedrine (E) prolongs time to exhaustion during high-intensity aerobic exercise. CNS stimulation by C and E was proposed as part of the mechanism for the improvement. It was thought that this arousal might also be of benefit during anaerobic exercise. The purpose of this study was to investigate the effect of C, E, and C+E ingestion on performance of anaerobic exercise. METHODS: Two groups were used to evaluate the effect of C and E on anaerobic performance. Group 1 (WIN) consisted of 16 healthy untrained male subjects who performed a 30-s Wingate test. Group 2 (MAOD) consisted of 8 healthy untrained male subjects who performed a supramaximal (125%VO(2peak)) cycle exercise trial to exhaustion to determine maximum accumulated oxygen deficit. The trials commenced 1.5 h after ingesting either C (5 mg x kg(-1)), E (1 mg x kg(-1)), a combination of C+E, or a placebo (P). All trials were randomized and double blind. Blood samples were assayed for lactate and glucose post drug ingestion just before exercise, and again 3, 5, and 10 min post exercise. Catecholamines were measured in the preexercise and 10-min postexercise blood samples. RESULTS: Ephedrine increased power output during the early phase of the Wingate test, whereas C increased time to exhaustion and O(2) deficit during the MAOD test. C, E, and C+E increased blood lactate, glucose, and catecholamine levels. CONCLUSION: The improvement in anaerobic exercise performance is likely a result of both stimulation of the CNS by E and skeletal muscle by C.     

Effect of caffeine on glycogenolysis during exercise in endurance trained rats

Caffeine has been reported to enhance performance by increasing lipid oxidation and sparing liver and muscle glycogen in human subjects during prolonged endurance exercise. In the present study, the effects of intravenous caffeine on the liver and muscle glycogenolysis during exercise in endurance trained rats were investigated. Male endurance trained rats (2 h.d-1 for 6-7 wk) were given injections of 5 mg.kg-1 caffeine (5 CAF), 25 mg.kg-1 caffeine (25 CAF), or 0.9% sodium chloride (SAL) and were run on the treadmill for 45 min, 90 min, or until exhaustion at 26 m.min-1 up a 15% grade. Intravenous caffeine did not enhance the endurance run time: 5 CAF = 149 +/- 14 min, 25 CAF = 152 +/- 10 min, and SAL = 176 +/- 10 min. Caffeine did not influence the rate of liver glycogenolysis during exercise [liver glycogen (mmol glucose units.g-1) after 90 min: 5 CAF = 139 +/- 26, 25 CAF = 133 +/- 25, and SAL = 120 +/- 32]. Liver cAMP, muscle glycogen, plasma free fatty acids, blood glucose, and lactate were likewise not affected by caffeine [plasma free fatty acids (mM) after 90 min: 5 CAF = 0.42 +/- 0.04, 25 CAF = 0.45 +/- 0.07, and SAL = 0.41 +/- 0.05]. These data indicate that intravenous caffeine does not enhance the endurance run time or alter the plasma free fatty acids or liver and muscle glycogen utilization in endurance trained rats.     

Effects of repeated exhaustive exercise on myocardial subcellular membrane structures

The effects of a single vs repeated bouts of exhaustive exercise on myocardial integrity were evaluated in the rodent. Rats were randomly divided into three groups: a sedentary control, single swim-to-exhaustion, and seven consecutive daily swims-to-exhaustion groups (n = 5 in each group). Overall morphology was evaluated histologically and sarcolemmal (SL), sarcotubular (ST), and mitochondrial (MITO) membranes were examined ultrastructurally using transmission electron microscopy. Neither single nor repeated bouts of exhaustive exercise produced myocardial hypoxia, as assessed by MITO morphology. However, increased interstitial space as well as significant swelling (P less than 0.01) was observed in ST from both 1- and 7-day exhausted animals. These findings were not observed at all in control myocardium. Higher magnification (x 45,000) in some instances revealed whole disruption of sarcotubular membranes in myocardium from swim-exhausted animals. The incidence of membrane disruption was higher (P less than 0.01) in 7-day vs 1-day swim-exhausted groups and not observed at all in control rats. Although in no instance did we observe disruption of SL membranes, their convoluted nature in myocardium from both exercised groups indicated exhaustion-induced fluid and/or ionic shifts within the left ventricle. These findings provide a structural basis for the reduction in myocardial sarcoplasmic reticulum and MITO Ca++ uptake previously observed following repeated bouts of exhaustive exercise.     

Reproductive profile of physically active men after exhaustive endurance exercise

The purpose of this study on non-professional (recreational) athletes was two-fold: 1) to determine if endurance exercise (EE) routinely used by professional athletes would produce reproductive changes in the general population, and 2) to assess reversion. Short-term exhaustive endurance exercise (EEE) can produce alterations in the hypothalamic-pituitary-gonadal (HPG) axis with subsequent fertility changes. Sixteen healthy adult male volunteers were divided into experimental (8) and control (8) groups for the exercise period. A cycloergometer provided EEE for a period of 2 weeks. The experimental group exercised four times a week; controls were without EEE. The hormonal and seminological profiles of all subjects were evaluated. Two weeks of EEE produced hormonal and seminological values in the experimental group that were statistically different from their own pre-treatment values (FSH: 3.33 +/- 1.7; LH: 3.73 +/- 1.36; sperm concentration/ml: 42.50 +/- 29.46; type a velocity: 25.23 +/- 10.9; type d velocity: 46.18 +/- 15.81; % of normal forms: 10.42 +/- 1.97) as well as from the pre- and post-treatment control group values. The measured parameters almost returned to pre-treatment levels in the experimental group 2 - 3 days after EEE ended. From this study we concluded that when subjected to EEE, individuals drawn from a recreational exercising life style experienced changes similar to those observed in studies done with athletes, and short-term EEE induced a reversible alteration to the HPG axis.     

Beta-endorphin, catecholamines, and cortisol during exhaustive endurance exercise

To assess changes of beta-endorphin during intense endurance exercise, ten nonspecifically trained volunteers (aged 25.7 +/- 2.9 years) were subjected to an exhaustive endurance test on a cycle ergometer at the work load of the individual anaerobic threshold (IAT) determined in a preparatory graded exercise test. Prior to, in 25-min intervals during, and repeatedly subsequent to exercise venous blood samples were drawn to measure the levels of beta-endorphin (beta-E), cortisol (C), adrenaline (A), and noradrenaline (NA). In addition, lactate, heart rate, and rate of perceived exertion were determined. The levels of beta-E remained unchanged during the first 50 min; between the 50th and 75th min beta-E increased by 82% (p less than 0.01). At the end of the exercise (mean exercise time: 89 min), a beta-E level three times the resting level was measured. The maximum exercise-induced increase of beta-E showed a positive correlation to endurance capacity (W.kg-1 of IAT): r = 0.74; p less than 0.05. C exhibited similar changes to beta-E, but the onset of increase was delayed if compared with beta-E; there was a close correlation between these two stress hormones (75th min of exercise: r = 0.91; p less than 0.001). The catecholamines A and NA increased linearly during exercise, without a correlation with the behavior of beta-E being established.     

Little effect of caffeine ingestion on repeated sprints in team-sport athletes

PURPOSE: The effect of caffeine ingestion on sprint performance is unclear. We have therefore investigated its effect on performance in a test that simulates the repeated sprints of team sports. METHODS: In a randomized double-blind crossover experiment, 16 male team-sport athletes ingested either caffeine (6 mg.kg-1 of body mass) or a placebo 60 min before performing a repeated 20-m sprint test. The test consisted of 10 sprints, each performed within 10 s and followed by rest for the remainder of each 10 s. The caffeine and placebo trials followed a familiarization trial, and the time between consecutive trials was 2-3 d. To allow estimation of variation in treatment effects between individuals, nine subjects performed three more trials without a supplement 7-14 d later. We estimated the smallest worthwhile effect on sprint time in a team sport to be approximately 0.8%. RESULTS: Mean time to complete 10 sprints increased by 0.1% (95% likely range -1.5 to 1.7%) with caffeine ingestion relative to placebo. Individual variation in this effect was a standard deviation of 0.7% (-2.7 to 2.9%). Time to complete the 10th sprint was 14.4% longer than the first; caffeine increased this time by 0.7% (-1.8 to 3.2%) relative to placebo, and individual variation in this effect was 2.4% (-3.4 to 4.9%). CONCLUSION: The observed effect of caffeine ingestion on mean sprint performance and fatigue over 10 sprints was negligible. The true effect on mean performance could be small at most, although the true effects on fatigue and on the performance of individuals could be somewhat larger. Pending confirmatory research, team-sport athletes should not expect caffeine to enhance sprint performance.     

Effect of carbohydrate ingestion on exercise endurance and metabolism after a 1-day fast

Fasting before an exercise event has been demonstrated to decrease endurance. The purpose of this study was to investigate whether this decrement in performance after fasting could be reversed by ingestion of a carbohydrate solution before and during exercise. Nine fit male subjects ran to exhaustion at approximately 70% VO2max in two counterbalanced trials. The subjects were fasted for 21 h before both trials, and the trials were arranged so that the subjects ingested either a carbohydrate (CHO) or placebo (PL) solution. Although ratings of perceived exertion were significantly lower in the CHO trial, there were no differences in endurance time to exhaustion in the two trials (102 +/- 8 min in the PL trial and 106 +/- 8 min in the CHO trial). There were no differences between trials for the VO2, heart rate, and blood lactate concentrations. As expected, the blood glucose and insulin concentrations were higher in the CHO trial. The respiratory exchange ratio was significantly higher in the CHO trial at 40 min of exercise and tended to be higher at all other times, suggesting a greater reliance on carbohydrate and less on fat as an energy source. This seemed to be confirmed by the significantly lower plasma glycerol concentration, which suggested less fat mobilization in the CHO trial. Ingestion of a glucose polymer solution increased carbohydrate utilization in fasted subjects, but exercise performance was not improved.     

The effect of ad libitum ingestion of a caffeinated carbohydrate-electrolyte solution on urinary caffeine concentration after 4 hours of endurance exercise

The purpose of the present study was to examine the effect of ad libitum ingestion of a carbohydrate-electrolyte solution (CES) with 150 mg x L (-1) caffeine (CAF) on urinary CAF concentration after 4 h of endurance exercise. Fifty-eight healthy and well-trained male subjects ingested ad libitum a 7 % CES with 150 mg x L (-1) CAF during 4 h cycling at 50 % of maximal work capacity. Total fluid consumption (mean +/- SE) was 2799 +/- 72 mL and CAF intake was 420 +/- 11 mg (5.7 +/- 0.2 mg x kg (-1) body weight). The post-exercise urinary CAF concentration (4.53 +/- 0.25 microg x mL (-1)) was below the doping level of the International Olympic Committee (12 microg x mL (-1)) in all subjects (range 1.20 - 10.84 microg x mL (-1)). A highly positive correlation was observed between CAF intake and post-exercise urinary CAF concentration (r = 0.68, p < 0.001). It is concluded that ad libitum ingestion of a CES with 150 mg x L (-1) CAF during 4 h cycling resulted in post-exercise urinary concentration below the doping level in all subjects.     

The effect of glucose ingestion on endurance upper-body exercise and performance

The physiological responses to glucose supplementation during arm crank exercise were investigated. Ten subjects of mean age 28 +/- 8 years; stature 180.8 +/- 6.5 cm; mass 82.7 +/- 11.5 kg, .VO(2) peak 3.10 +/- 0.50 l x min(-1) were tested on two occasions separated by a week. A 7.6% glucose drink or placebo was administered in a blind crossover design 20 min prior to exercise. Subject's arm cranked for 60 min at an exercise intensity of 65% .VO(2)peak followed by a 20 min performance test. Rate of ventilation, oxygen uptake, RER, heart rate and blood lactate demonstrated similar responses between trials throughout the course of the hour. The blood glucose concentrations at rest were similar between trials increasing after glucose ingestion to show a significant difference (p < 0.05) to the placebo trial at the onset of exercise, then returning to resting values after 20 min. The 20 min performance tests revealed that after glucose ingestion athletes achieved a greater mean distance of 12.55 +/- 1.29 km than in the placebo trial of 11.50 +/- 1.68 km (p < 0.05). In conclusion, the results showed that after one-hour of arm crank exercise, performance over a further twenty minutes was improved when glucose was ingested twenty minutes prior to exercise.     

Effects of salbutamol and caffeine ingestion on exercise metabolism and performance

This study was designed to assess the effects of acute oral salbutamol and caffeine intake on performance and metabolism during short-term endurance exercise. Eight healthy volunteers participated in the double-blind placebo-controlled randomized cross-over study. Two 10 min cycling trials were performed at a power corresponding to 90 % VO 2 max for the first and a mock test for the second, separated by 10 min of passive recovery after ingestion of placebo (Pla), salbutamol (Sal, 6 mg) and caffeine (Caf, 250 mg). Performance (mean power during the mock test) was not statistically significant between the 3 treatments. Blood lactate was significantly increased after Sal compared to Pla at rest and until the end of the mock test whereas it appeared significantly increased after Caf compared to Pla at the end of the two exercises. Sal increased basal blood glucose and both Sal and Caf induced significant higher plasma insulin concentrations at rest, at the end of the mock test and during the recovery compared to Pla. No significant changes were found in these three variables between the Sal and the Caf treatments. Plasma growth hormone was significantly decreased after Sal after the mock test compared to the two other treatments. In conclusion, under the conditions of this study, neither oral salbutamol nor caffeine intake produce enhancement of short-term performance in non-specific trained subjects despite the substantial shifts in metabolic and hormonal parameters which were found.     

Effects of sucrose or caffeine ingestion on running performance and biochemical responses to endurance running

To elucidate the effects of sucrose or caffeine ingestion on metabolic responses to prolonged exercise and on performance of a finishing spurt after the prolonged exercise, seven male physical education students performed four sets of 30 min running (62%-67% VO2 max) followed by progressive exhaustive running on a treadmill. Before each set, they took 350 ml solution containing either sucrose 23.8 g (97.5 kcal), caffeine 200 mg, or a placebo. The duration of the exhaustive running after sucrose, caffeine, or placebo ingestion was not significantly different. Exhaustion would possibly be attained not by depletion of muscle glycogen but by a decrease in the capacity of muscle cells to produce high tension for anaerobic metabolism. Total energy and energy from carbohydrate combusted during four sets of running were estimated at 1255 kcal and 810 kcal in the sucrose trial, 1271 kcal and 624 kcal in the caffeine trial, and 1248 kcal and 649 kcal in the placebo trial. Judging from the figures above, glycogen sparing during prolonged running seemed to be attained by sucrose ingestion but not by caffeine ingestion. The latter finding would be caused by lower intensity and a larger amount of ingested caffeine. In conclusion, performance of progressive exhaustive running following endurance running for 2 h could not be improved either by sucrose or caffeine ingestion. Glycogen sparing in the muscle, however, was suggested by sucrose ingestion but not by caffeine ingestion.     

Salivary IgA responses to prolonged intensive exercise following caffeine ingestion

PURPOSE: Prolonged, intensive exercise is associated with a reduction in concentration and secretion of salivary IgA (s-IgA). Saliva composition and secretion are under autonomic nervous system control, and caffeine ingestion, a widespread practice among athletes for its ergogenic properties, is associated with increased sympathetic nervous system activation. Therefore, this study investigated the influence of caffeine ingestion on s-IgA responses to prolonged, intensive exercise. METHODS: In a randomized crossover design, 11 endurance-trained males cycled for 90 min at 70% VO2peak on two occasions, having ingested 6 mg x kg(-1) body mass of caffeine (CAF) or placebo (PLA) 1 h before exercise. Whole, unstimulated saliva samples were collected before treatment (baseline), preexercise, after 45 min of exercise (midexercise), immediately postexercise, and 1 h postexercise. Venous blood samples were collected from a subset of six of these subjects at baseline, preexercise, postexercise, and 1 h postexercise. RESULTS: An initial pilot study found that caffeine ingestion had no effect on s-IgA concentration, secretion rate, or saliva flow rate at rest. Serum caffeine concentration was higher on CAF than PLA at preexercise, postexercise, and 1 h postexercise (P < 0.001). Plasma epinephrine concentration was higher on CAF than PLA at pre- and postexercise (P < 0.05). s-IgA concentration was higher on CAF than PLA at mid- and postexercise (P < 0.01), and s-IgA secretion rate was higher on CAF than PLA at midexercise only (P < 0.02). Caffeine ingestion did not affect saliva flow rate. Saliva alpha-amylase activity and secretion rate were higher on CAF than PLA (main effect for trial, P < 0.05). CONCLUSIONS: These findings suggest that caffeine ingestion before intensive exercise is associated with elevated s-IgA responses during exercise, which may be related to increases in sympathetic activation.     

Increased neuroendocrine response to a repeated bout of endurance exercise

This study was designed to compare a first bout of high-intensity endurance exercise with a second bout of similar exercise on the same day, and thereby test the hypothesis that the endocrine response elicited by a second bout is more pronounced compared with a single bout of exercise. Nine male, elite endurance athletes participated in three trials of 24-h duration: 1) complete bed rest (REST), 2) one bout of exercise (ONE), and 3) two bouts of exercise separated by a 3-h rest period (TWO). Each exercise bout consisted of a 10-min warm-up at 50% of VO(2max) followed by 65 min at 75% of VO(2max) on a cycle ergometer. Exercise was performed between 11:00 a.m. and 12:15 a.m. (only in TWO) and 3:15 and 4:30 p.m. (both ONE and TWO). The subjects rested in bed at all hours except when exercising. Blood was sampled 11 times at identical time-points until 7:30 a.m. the next morning. We observed significantly increased levels of epinephrine, norepinephrine, ACTH, cortisol, and growth hormone, and decreased levels of testosterone during and/or after the second bout of exercise compared with the first bout. No difference was observed for insulin, follicle stimulating hormone, luteinizing hormone, thyroid stimulating hormone, free fraction of thyroxin or insulin-like growth factor 1. Thus, this study demonstrates a more pronounced neuroendocrine response to a second bout of exercise on the same day compared with a first/single bout, involving both the sympatho-adrenal system and the hypothalamo-pituitary-adrenal axes.     

Caffeine in sport. Influence of endurance exercise on the urinary caffeine concentration.

This study was conducted to evaluate the influence of excessive sweating during long-distance running on the urinary concentration of caffeine after the intake of a large amount of caffeine. Nine endurance-trained athletes participated in a randomised cross-over study in which 450 mg caffeine were taken with and without exercise. Exercise consisted of running for 30 min on a treadmill at 75% of maximum heart rate, one hour after intake of caffeine. This endurance exercise caused a decrease in the urine flow as well as in the amount of caffeine excreted in urine. The combined effect of both these decreases is that the concentrations of caffeine detected in urine were similar with and without exercise. The maximum caffeine concentration detected in any urine sample was 11.9 micrograms/ml without exercise and 10.4 micrograms/ml with exercise. It can be concluded that excessive sweating during long-distance running did not enhance the urinary caffeine concentration.     

Effects of repeated endurance exercise on serum enzyme activities in well-conditioned males.

Daily fluctuations in serum enzyme activities during distance running in 3 well-conditioned males were measured for 8 consecutive days. During the study the exercise regimen comprised 8 mile runs on days 1, 2 and 5; a 10.5 mile run on day 3; a 15 mile run on day 4 and resting on days 6-8. Heart rate, rectal temperature, hematocrit, plasma hemoglobin, creatine phosphokinase (CPK, glutamic-oxaloacetic and glutamic-pyruvic transaminases, lactate dehydrogenase (LDH), adenylate kinase (AK), and lactate and pyruvate were measured before and after exercise and during the resting days. Significant increases occurred in heart rate and rectal temperature with each run but were unrelated to enzyme levels. Pre-exercise CPK levels, 49 plus or minus 1 mIU/ml on day 1, rose progressively to 123 plus or minus 25 mIU/ml on day 5, and returned to initial control levels by day 8. Post-exercise CPK levels were significantly greater than pre-exercise levels on each running day but were unrelated to the severity of the exercise. LDH and AK levels did not significantly change with the exercise stress, but pre-exercise AK levels in these trained males were higher than values in non-trained males (10-20 vs. 0-5 mIU/ml) (3). Post-exercise enzyme levels appeared unrelated to final heart rate, rectal temperature or plasma hemoglobin. These results suggest that (1) CPK, unlike the other enzymes studied, is a sensitive index of exercise stress in well-conditioned runners and (2) elevated CPK and AK levels in such runners represent physiologic responses. Appropriate caution should be used in making clinical judgements from these enzyme assays in trained individuals.     

Effect of pre-exercise fructose ingestion on endurance performance in fed men

Twelve trained males, in a fed state, were studied to examine the effect of pre-exercise fructose ingestion on endurance capacity during prolonged cycling exercise. Sixty minutes prior to exercise, subjects ingested either 60 or 85 g fructose or a sweet placebo. Mean exercise intensity initially required 62% of the maximal aerobic power and thereafter increased to elicit 72 and 81% of maximal aerobic power at 90 and 120 min of exercise, respectively. Exercise time (mean +/- SE) to exhaustion was significantly increased after fructose ingestion, as compared to placebo ingestion (145 +/- 4 vs 132 +/- 3 min, P less than 0.01). During the exercise, no differences were observed between both trials for oxygen uptake, heart rate, or perceived exertion. Serum glucose and insulin levels between both trials were not significantly different throughout the experiment. There were also no significant differences in serum-free fatty acids and glycerol levels as well as respiratory exchange ratio between fructose and placebo trials during the exercise. The results suggest that fructose ingestion is of benefit before prolonged exercise, because it provides a carbohydrate source to contracting muscles without transient hypoglycemia and a depression of fat utilization, and thereby delays the fatigue.