Low Doses Of Caffeine Research Articles

Use of an ATP-supplemented medium for the conservation of human semen and the effect of caffeine on the motility of preserved sperm. Results in artificial insemination.

Human semen can be preserved at 4 degrees C in an artificial medium containing 15% ATP-MgCl2 for up to 5 d. This method has been applied to samples from subjects with either normal or abnormal semen. After the conservation period the recovery of sperm motility observed was good when low doses of caffeine (3.5 or 7.0 mM) were added.

Early long-term exposure with caffeine induces cross-sensitization to methylphenidate with involvement of DARPP-32 in adulthood of rats

Chronic ingestion of caffeine causes dependence and sleep disturbance in children and adolescents. In rodents, the administration of caffeine may produce behavioral cross-sensitization to some psychostimulants, such as dopaminergic psychoactive drugs. Methylphenidate (MPH; Ritalin®) is a psychostimulant used in pediatric- and adult human populations to manage the symptoms associated with attention-deficit hyperactivity disorder (ADHD). Previous studies have suggested that dopamine- and cAMP-regulated phosphoproteins of 32kDa (DARPP-32) participate in the manifestation of behavioral activity following ingestion of caffeine or MPH. The aim of the present study was to evaluate whether long-term administration of low doses of caffeine in rodents during their adolescence induces cross-sensitization to MPH challenge in their adulthood and investigate the involvement of DARPP-32 in this model. Young rats (P25) consumed water or caffeine (0.3g/L; mean consumption was 7.5mg/day/kg) for 28 days. The caffeine consumption was then suspended for 14 days (washout period) when the animals received saline solution or MPH (1, 2, or 10mg/kg) (P67) intraperitoneally. The locomotor activity of these rats was assessed using the open-field test, following which the immunocontent of DARPP-32 was evaluated in samples of their prefrontal cortex, striatum, or hippocampus. Rats chronically exposed to caffeine in their adolescent period and to inactive doses of MPH (1mg/kg) in adulthood showed augmented locomotor activity. The behavioral effect observed was accompanied by increased levels of DARPP-32 in the striatum and prefrontal cortex compared to control groups (saline or caffeine). However, no alteration caused by these treatments was noted in the hippocampus. In conclusion, chronic caffeine exposure induces likely long-term cross-sensitization to MPH in a DARPP-32-dependent pathway.

Uncovering multiple molecular targets for caffeine using a drug target validation strategy combining A 2A receptor knockout mice with microarray profiling.

Caffeine is the most widely consumed psychoactive substance and has complex pharmacological actions in brain. In this study, we employed a novel drug target validation strategy to uncover the multiple molecular targets of caffeine using combined A(2A) receptor (A(2A)R) knockouts (KO) and microarray profiling. Caffeine (10 mg/kg) elicited a distinct profile of striatal gene expression in WT mice compared with that by A(2A)R gene deletion or by administering caffeine into A(2A)R KO mice. Thus, A(2A)Rs are required but not sufficient to elicit the striatal gene expression by caffeine (10 mg/kg). Caffeine (50 mg/kg) induced complex expression patterns with three distinct sets of striatal genes: 1) one subset overlapped with those elicited by genetic deletion of A(2A)Rs; 2) the second subset elicited by caffeine in WT as well as A(2A)R KO mice; and 3) the third subset elicited by caffeine only in A(2A)R KO mice. Furthermore, striatal gene sets elicited by the phosphodiesterase (PDE) inhibitor rolipram and the GABA(A) receptor antagonist bicucullin, overlapped with the distinct subsets of striatal genes elicited by caffeine (50 mg/kg) administered to A(2A)R KO mice. Finally, Gene Set Enrichment Analysis reveals that adipocyte differentiation/insulin signaling is highly enriched in the striatal gene sets elicited by both low and high doses of caffeine. The identification of these distinct striatal gene populations and their corresponding multiple molecular targets, including A(2A)R, non-A(2A)R (possibly A(1)Rs and pathways associated with PDE and GABA(A)R) and their interactions, and the cellular pathways affected by low and high doses of caffeine, provides molecular insights into the acute pharmacological effects of caffeine in the brain.

Ryanodine Receptor Sensitization Alters Local And Global Sarcoplasmic Reticulum Calcium Release Termination Threshold In Rabbit Ventricular Myocytes

Dynamic measurements of Ca within the sarcoplasmic reticulum ([Ca]SR) using low-affinity Ca indicators give critical insight into the role of [Ca]SR in Ca release termination. Here we used a low dose of caffeine to examine the effects of ryanodine receptor (RyR) sensitization on local and global SR Ca release in rabbit ventricular myocytes. In field stimulated myocytes (1 Hz), application of 250 μM caffeine caused an initial 44% increase in amplitude of action potential-induced [Ca]SR depletion. This resulted in unloading of the SR (27% decrease in steady state diastolic [Ca]SR) and a lowering of the termination level for global release (28% decrease in systolic [Ca]SR). A single stimulus protocol was used to examine the effects of caffeine on SR Ca release after varying [Ca]SR. At all [Ca]SR levels where release was observed, caffeine increased the [Ca]SR depletion amplitude by lowering the global termination level of release. We next studied the effects of caffeine on local SR Ca release events in permeabilized myocytes by simultaneously measuring cytosolic Ca sparks with associated local [Ca]SR depletions (Ca blinks). Under control conditions, Ca sparks terminated at a fixed [Ca]SR depletion threshold, irrespective of initial [Ca]SR. Application of 200 μM caffeine caused an immediate increase in Ca spark frequency (58%), amplitude (8%), duration (23%), and spatial width (13%), and decreased the Ca blink termination level below the control threshold level. Taken together, these data suggest that sensitization of the RyR produces an increase in SR Ca release by decreasing the [Ca]SR termination level for release at individual release junctions.

Early effects of caffeinated and decaffeinated coffee on subjective state and gender differences

Objectives Some previous studies have demonstrated an early effect of caffeine administration on subjective state, but none of them has explored its existence after the administration of decaffeinated coffee, or the possible differences depending on the gender and circadian typology of the subjects. The aim of the present work is to investigate the early effects (10–30 min post-consumption) of a single low dose of caffeine (100 mg) and decaffeinated coffee on sleepiness, subjective activation and affect using a realistic design. The influence of gender and circadian typology is also explored. Methods A randomized double-blind informed placebo controlled procedure was applied to 688 healthy undergraduate volunteers, mean age 22.03 ± 2.21 years, 238 men and 450 women. Measures were recorded before and after beverage consumption (10, 20 and 30 min), in two experimental sessions: morning 11:00–13:00 h or afternoon 16:00–18:00 h. Results Caffeine administration induced arousing effects (lesser somnolence and greater activation) in all post-consumption records, while the effects of decaffeinated drink were only apparent at 10 min. Caffeine effects were greater in men, and the decaffeinated beverage produced greater effects in women. Circadian typology only showed effects for time of day (morning/afternoon) related with rhythmic expression. Conclusion Future works should study more accurately the early effect of coffee beverages and the influence of gender, using other parameters which have proven to be sensitive to their administration. The effect of several caffeine doses should also be studied.

Ergogenic Effects of Low Doses of Caffeine on Cycling Performance

The purpose of this experiment was to learn whether low doses of caffeine have ergogenic, perceptual, and metabolic effects during cycling. To determine the effects of 1, 2, and 3 mg/kg caffeine on cycling performance, differentiated ratings of perceived exertion (D-RPE), quadriceps pain intensity, and metabolic responses to cycling exercise, 13 cyclists exercised on a stationary ergometer for 15 min at 80% VO, then, after 4 min of active recovery, completed a 15-min VO2peak performance ride 60 min after ingesting caffeine or placebo. Work done (kJ/kg) during the performance ride was used as a measure of performance. D-RPE, pain ratings, and expired-gas data were obtained every 3 min, and blood lactate concentrations were obtained at 15 and 30 min. Compared with placebo, caffeine doses of 2 and 3 mg/kg increased performance by 4% (95% CI: 1.0-6.8%, p = .02) and 3% (95% CI: -0.4% to 6.8%, p = .077), respectively. These effects were ergogenic, on average, but varied considerably in magnitude among individual cyclists. There were no effects of caffeine on D-RPE or pain throughout the cycling task. Selected metabolic variables were affected by caffeine, consistent with its known actions. The authors conclude that caffeine preparations of 2 and 3 mg/kg enhanced performance, but future work should aim to explain the considerable interindividual variability of the drug's ergogenic properties.

The Effect of Caffeine Supplementation on Performance in the Standing Shot Put Throw

BACKGROUND: Caffeine has been shown to have ergogenic effects on both aerobic and anaerobic activities. These ergogenic effects have been demonstrated in activities that range from distance running to sprint cycling. However, the possible ergogenic effects of caffeine on the shot put event have not been investigated. PURPOSE: The purpose of the present investigation was to determine if caffeine has ergogenic effects on performance in the shot put event. METHODS: A double-blinded, counterbalanced, within subjects design was used to investigate the ergogenic effects of caffeine on the shot put. Four male (age: 20.5±2.1 yrs, height: 1.82 ± 0.07m, weight: 115.68 ± 13.03kg) and five female (age: 19.6 ± 1.9yrs, height: 1.73 ± 0.07m, weight: 98.72 ± 28.47kg) college shot putters participated in the study. Prior to participating, participants were asked about caffeine usage. The participants reported an average daily caffeine intake of (73 ± 97mg). Prior to each series of measured throws, participants received either a piece of gum designed to deliver 100mg of caffeine in a buccal manner (CAFF), or a placebo gum (PL). The gum was chewed for 5 min then discarded. The participants then completed a series of 5 warm-up throws, followed by 6 attempts with a shot put (16lbs for males, 4kg for females) that were measured for distance. RESULTS: An ANOVA (treatment x throw) was also performed to compare performance between the CAFF and PL treatments over the six measured attempts. A significant difference (treatment x throw) was found (p<0.05) indicating that the CAFF treatment produced better performance over the course of the six attempts. Paired samples t-tests were performed to compare the first attempt between the CAFF treatment (9.63±1.69 meters) and the PL treatment (9.05±1.71 meters). A significant increase in performance was found in the CAFF treatment (p<0.05). CONCLUSIONS: Caffeine increased the performance of shot putters over the course of six attempts. This finding suggests to coaches and athletes involved in the event, that low dose caffeine (100mg) is an effective ergogenic aid.

1 – Is schizoaffective disorder more akin to mood disorders than schizophrenia

The objective of this study was to determine the effects of different doses of caffeine on appetite and anxiety-related behavior. Additionally, we sought to determine if withdrawal from chronic caffeine administration promotes anxiety. In this study, we utilized rodent open field testing and feeding behavior assays to determine the effects of caffeine on feeding and anxiety-related behavior (n = 8 mice; 4–8 weeks old). We also measured 2 h and 24 h food intake and body-weight during daily administration of caffeine (n = 12 mice; 4–8 weeks old). To test for caffeine withdrawal induced anxiety, anxiety-related behavior in rodents was quantified following withdrawal from four consecutive days of caffeine administration (n = 12 mice; 4–8 weeks old). We find that acute caffeine administration increases food intake in a dose-dependent manner with lower doses of caffeine more significantly increasing food intake than higher doses. Acute caffeine administration also reduced anxiety-related behaviors in mice without significantly altering locomotor activity. However, we did not observe any differences in 24 h food intake or body weight following chronic caffeine administration and there were no observable differences in anxiety-related behaviors during caffeine withdrawal. In conclusion, we find that caffeine can both increase appetite and decrease anxiety-related behaviors in a dose dependent fashion. Given the complex relationship between appetite and anxiety, the present study provides additional insights into potential caffeine-based pharmacological mechanisms governing appetite and anxiety disorders, such as bulimia nervosa.

Influence of caffeine ingestion on perceived mood states, concentration, and arousal levels during a 75-min university lecture

This investigation aimed to assess the effect of a caffeine supplement on perceived mood state, concentration, and arousal during a 75-min university lecture. Methods. This randomized, blind, cross-over design investigation ran over a course of 2 consecutive weeks. During week 1, 10 third-year Human Movement and Exercise Science students were assigned to either a caffeine- or placebo-supplemented group and were subsequently required to attend a 75-min exercise rehabilitation lecture. Seven days later, students were assigned to the opposite supplementation group before attending a second follow-on lecture, equal in duration to that of week 1. At the conclusion of each lecture, students were required to complete a mood perception questionnaire to assess the perceived level of mood state, concentration, and arousal during the lecture. The results showed that after caffeine consumption, students perceived themselves to be significantly more awake, clear minded, energetic, alert, and anxious (P < 0.05). Additionally, students also felt they were better able to concentrate and had a greater level of arousal than when the placebo was consumed (P < 0.05). In conclusion, the results of this investigation show that university students report enhanced perceptual feelings of behavior and mood state when a low dose of caffeine is consumed 60 min prior to a 75-min academic lecture.

Changes in sensitivity of response distributions to changing reinforcement ratios during exposure to ephedrine, caffeine, and ephedrine–caffeine combinations

Changes in the sensitivity of response distributions to changes in reward distribution (reinforcer distribution sensitivity) were examined when rats were exposed to low and moderate doses of caffeine, ephedrine, and caffeine-ephedrine combinations. The data show significant decreases in sensitivity in response distributions to changes in reward schedule values during exposure to caffeine and ephedrine/caffeine combinations, whereas ephedrine alone resulted in overmatching comparable with baseline and NaCl conditions. Rats treated either with 3.0-mg/kg or 10.0-mg/kg doses of caffeine and all combinations of ephedrine at doses of 1.8 or 5.6 mg/kg with caffeine at 3.0 or 10.0 mg/kg showed reduced sensitivity in response distributions to differences in reinforcement schedule ratios. In contrast, when rats were exposed to ephedrine at 1.8 or 5.6 mg/kg, they maintained or increased the degree of overmatching. Although reinforcer distribution sensitivity was altered, drug exposure did not significantly affect the absolute rates of responding. Bias varied after exposure to caffeine, ephedrine, and their combinations, but not systematically. Finally, whereas the estimates of goodness of fit (r2) to the matching equation showed some decreases during drug exposure, these were neither statistically significant nor correlated with drug dose. These results suggest differential effects of ephedrine and caffeine on the sensitivity of response distributions to changes in reinforcement ratio distributions, with deleterious effects of caffeine and ephedrine/caffeine combinations.

Voluntary exercise together with oral caffeine markedly stimulates UVB light-induced apoptosis and decreases tissue fat in SKH-1 mice.

Treatment of SKH-1 mice orally with caffeine (0.1 mg/ml in the drinking water), voluntary running wheel exercise, or a combination of caffeine and exercise for 2 weeks (i) decreased the weight of the parametrial fat pads by 35, 62, and 77%, respectively; (ii) decreased the thickness of the dermal fat layer by 38, 42, and 68%, respectively; (iii) stimulated the formation of UVB-induced apoptotic sunburn cells in the epidermis by 96, 120, and 376%, respectively; and (iv) stimulated the formation of UVB-induced caspase 3 (active form)-positive cells in the epidermis by 92, 120, and 389%, respectively (average of two experiments). Oral administration of caffeine (0.4 mg/ml in the drinking water) in combination with voluntary exercise was less effective than administration of the low dose of caffeine in combination with exercise in stimulating UVB-induced apoptosis. Although orally administrated caffeine (0.1 mg/ml in the drinking water) or voluntary exercise for 2 weeks caused only a small nonsignificant stimulation of UVB-induced increase in the percentage of phospho-p53 (Ser-15)-positive cells in the epidermis (27 or 18%, respectively), the combination of the two treatments enhanced the UVB-induced increase in phospho-p53 (Ser-15)-positive cells by 99%. The plasma concentration of caffeine in mice ingesting caffeine (0.1-0.4 mg/ml drinking water) is similar to that in the plasma of most coffee drinkers (one to four cups per day). Our studies indicate a greater than additive stimulatory effect of combined voluntary exercise and oral administration of a low dose of caffeine on UVB-induced apoptosis.

Low doses of caffeine reduce heart rate during submaximal cycle ergometry

BackgroundThe purpose of this study was to examine the cardiovascular effects of two low-levels of caffeine ingestion in non habitual caffeine users at various submaximal and maximal exercise intensities.MethodsNine male subjects (19–25 yr; 83.3 ± 3.1 kg; 184 ± 2 cm), underwent three testing sessions administered in a randomized and double-blind fashion. During each session, subjects were provided 4 oz of water and a gelatin capsule containing a placebo, 1.5 mg/kg caffeine, or 3.0 mg/kg caffeine. After thirty minutes of rest, a warm-up (30 Watts for 2 min) the pedal rate of 60 rpm was maintained at a steady-state output of 60 watts for five minutes; increased to 120 watts for five minutes and to 180 watts for five minutes. After a 2 min rest the workload was 180 watts for one minute and increased by 30 watts every minute until exhaustion. Heart rate (HR) was measured during the last 15-seconds of each minute of submaximal exercise. Systolic blood pressure (BP) was measured at rest and during each of the three sub-maximal steady state power outputs. Minute ventilation (VE), Tidal volume (VT), Breathing frequency (Bf), Rating of perceived exertion (RPE), Respiratory exchange ratio (RER), and Oxygen consumption (VO2) were measured at rest and during each minute of exercise.ResultsCaffeine at 1.5 and 3.0 mg/kg body weight significantly lowered (p < 0.05) HR during all three submaximal exercise intensities compared to placebo (range – 4 to 7 bpm lower) but not at rest or maximal exercise. BP was significantly higher (p < 0.05) at rest and after the 3 mg/kg caffeine vs placebo (116 ± 13 vs 123 ± 10 mm Hg). Neither dose of caffeine had any effect on BP during submaximal exercise. Caffeine had no effect on VE, VT, VO2, RPE, maximal power output or time to exhaustion.ConclusionIn non habitual caffeine users it appears that consuming a caffeine pill (1.5 & 3.0 mg/kg) at a dose comparable to 1–3 cups of coffee lowers heart rate during submaximal exercise but not at near maximal and maximal exercise. In addition, this caffeine dose also only appears to affect systolic blood pressure at rest but not during cycling exercise.

Dose Reponse Effects Of Caffeine During Exercise In Young Children

Only three studies have systematically investigated the effects of caffeine in children during exercise (Barta, Acta Paediatr.,1982; Turley, Med. Sci. Sports Exerc., 2005; Turley, Ped. Exerc. Sci., 2006) and all used relatively high doses of caffeine (4-5mg/ kg). No study has investigated the physiological dose response effects of caffeine in children during submaximal exercise. PURPOSE: Determine the influence of low (1mg/kg), moderate (3mg/kg), and high (5mg/kg) doses of caffeine on physiological responses to exercise in young children. METHODS: Forty children (20 boys and 20 girls) ages 7–9 years participated in a randomized, double-blind, counter-balanced, cross-over study. Over four separate visits each child consumed a placebo (PL-cherry flavored drink), 1.0 mg/kg (CAF-1), 3.0 mg/kg (CAF-3), and 5 mg/kg (CAF-5) of anhydrous caffeine mixed with PL, and then rested. After an hour wash-in period, resting measurements were taken (heart rate (HR) and blood pressure (BP)) and the children then rode at 25 W and 60% VO2max for eight minutes each. During exercise HR, VO2, and respiratory exchange ratio (RER) were measured continuously and BP was measured every two minutes. RESULTS: Resting HR was significantly (p<0.05) lower at 3 and 5 mg/kg vs PL (79.9±9.1 and79.0±6.8vs 84.8±10.4, respectively). HR was significantly lower in CAF-3 and CAF-5 vs PL at 25W (122.8±12.2 and 122.0±10.9 vs 128.4±12. respectively) and 60% VO2max (153.5±13.4 and 154.0±15.0 vs 158.9±13.9, respectively). Resting diastolic BP (DBP) was significantly higher in CAF-1, CAF-3, and CAF-5 vs PL (65.2±6.6, 66. 0±5.9, 66.6±7.8 vs 61.3±7.0, respectively). Resting systolic BP (SBP) was significantly higher at CAF-5 vs and PL (109.7±8.7 vs 104.9±9.0 respectively). RER, at 60% VO2max was significantly higher in CAF-5 vs andPL(1.02±0.04vs 1.00±0.04, respectively) CONCLUSIONS: In this study low, moderate, and high doses of caffeine were found to significantly increase DBP at rest. During rest and exercise, moderate and high doses of caffeine significantly lowered HR. Although there was a trend for CAF-5 to elevate BP during exercise, it was not significant.

Effects Of Caffeinated Sports Drinks On Physical/Mental Function During Team Sports Exercise

The ergogenic effects of caffeine ingestion (240–840 mg) on exercise performance is well established, albeit in some cases with negative side effects. However, recent evidence shows that much smaller doses can have beneficial effect on endurance performance as well as on mental function. Less is known about the possible synergistic effects of low dose of caffeine (CAF) and carbohydrate (CHO) feedings, especially as related to team sports performance. PURPOSE: To determine the effects of low dose (100 mg) CAF ingestion along with typically recommended CHO on physical and mental function during intermittent high intensity exercise that mimics the demands of competitive team sports. METHODS: Physically active male (N=6) and female (N=4) low to moderate caffeine users participated in this study. Experimental trials consisted of four ∼22-minute quarters (QTR) of shuttle running. Physical and mental function tests were administered throughout the experimental trial including (20-m sprint, vertical jump, gross motor skill test, force sensation, rating of perceived exertion, profile of mood states and psychomotor vigilance test).On four separate occasions, subjects received 20-oz of flavored water placebo (PLA), CHO, PLA+CAF and CHO+CAF prior to exercise. During exercise, subjects ingest PLA, CHO, PLA and CHO respectively (3.5 ml·kg-1). RESULTS: No difference was found in 20-m sprint time, vertical jump and gross motor skills performance between any treatments. However, both caffeine treatments (PLA+CAF and CHO+CAF) significantly improved psychomotor vigilance and reduced force sensation at HALFTIME (p<0.05). CHO+CAF also improved self-reported perception of fatigue, vigor and overall mood compared to PLA+CAF (p<0.05). Systolic blood pressure was increased with CHO+CAF compare to other three treatments. However, no difference was found in heart rate, core body temperature, plasma volume change, or hydration status between any treatments. CONCLUSION: The data suggest that ingestion of a low dose of caffeine prior to exercise did not add to the expected benefits of CHO feedings alone on physical tasks. However, all of the mental function tasks were significantly enhanced with the combination of CHO plus CAF, with little or no adverse side effects. Funded by Gatorade Sports Science Institute.

Ergogenic, Metabolic and Perceptual Effects of Low Doses of Caffeine

Ergogenic, Metabolic and Perceptual Effects of Low Doses of Caffeine

Pharmacokinetic and Pharmacodynamic Interactions Between Zolpidem and Caffeine

The kinetic and dynamic interaction of caffeine and zolpidem was evaluated in a double-blind, single-dose, six-way crossover study of 7.5 mg zolpidem (Z) or placebo (P) combined with low-dose caffeine (250 mg), high-dose caffeine (500 mg), or placebo. Caffeine coadministration modestly increased maximum plasma concentration (C(max)) and area under the plasma concentration-time curve of zolpidem by 30-40%, whereas zolpidem did not significantly affect the pharmacokinetics of caffeine or its metabolites. Compared to P+P, Z+P significantly increased sedation, impaired digit-symbol substitution test performance, slowed tapping speed and reaction time, increased EEG relative beta amplitude, and impaired delayed recall. Caffeine partially, but not completely, reversed most pharmacodynamic effects of zolpidem. Thus, caffeine only incompletely reverses zolpidem's sedative and performance-impairing effects, and cannot be considered as an antidote to benzodiazepine agonists.

Inhibitory effects of caffeine on hippocampal neurogenesis and function

Caffeine is one of the most extensively consumed psychostimulants in the world. However, compared to short-term effects of caffeine, the long-term effects of caffeine consumption on learning and memory are poorly characterized. The present study found that long-term consumption of low dose caffeine (0.3 g/L) slowed hippocampus-dependent learning and impaired long-term memory. Caffeine consumption for 4 weeks also significantly reduced hippocampal neurogenesis compared to controls. From these results, we concluded that long-term consumption of caffeine could inhibit hippocampus-dependent learning and memory partially through inhibition of hippocampal neurogenesis.

Low doses of caffeine late in exercise improve cycling time trial performance

Moderate and high doses of caffeine (>300 mg) have been shown to improve endurance exercise performance in a variety of laboratory and field tests. The present study investigated the effects of low caffeine doses given late in exercise on cycling time trial (TT) performance. Fifteen (11 male, 4 female) competitive cyclists (22.5 ± 0.9 yr, 69.3 ± 2.6 kg, 64.6 ± 1.9 ml/kg/min) completed three randomized cycling trials. Each trial consisted of 2 hr cycling at ~60% VO2peak with five simulated hill climbs (~85% VO2peak for 2 min) and descents (50 W for 40 s) followed by a TT where subjects completed 6 kJ of work/kg BW as quickly as possible (25–30 min). Subjects were given a carbohydrate-electrolyte solution (CES) (3ml/kg BW) prior to cycling and at 20, 40 and 60 min during exercise. At 80 min, subjects were given 350 ml CES with either, no caffeine (PL), 100 mg caffeine (CAF1) or 200 mg caffeine (CAF2). Body mass was maintained and heart rate, VO2, RER, and blood glucose responded similarly during all trials. The TT was completed in 1720 ± 38.2 s in PL and 65 s faster in CAF1 (1655 ± 32.8 s) and 124 s faster in CAF2 (1596 ± 22.5 s). Blood lactate was significantly higher following both CAF trials compared to the PL.

Sustained improvement of motor function in hemiparkinsonian rats chronically treated with low doses of caffeine or trihexyphenidyl

The effects of chronic oral treatment with low doses of caffeine (1–3 mg/kg) and trihexyphenidyl (0.1–0.2 mg/kg) were tested on hemiparkinsonian rats, which received the following treatments in a counterbalanced order: vehicle, caffeine, trihexyphenidyl, and caffeine plus trihexyphenidyl. Three preclinical models were used: the stepping test, the cylinder test, and the staircase test. Compared to pre-lesion values, the forepaw contralateral to the dopamine-denervated side showed impaired stepping, fewer wall contacts in the cylinder test, and fewer pellets retrieved in the staircase test. In the stepping test both doses of caffeine produced a complete recovery of motor function (100%), whereas the effect of trihexyphenidyl was less intense (77–80%). In this same test the maximal effect of drugs did not develop tolerance during 2–3 weeks, and was completely reversible after drug cessation. In the cylinder test only the wall contacts performed simultaneously with both forepaws were significantly increased by caffeine (3 mg/kg) and trihexyphenidyl (0.2 mg/kg), and this effect was also reversible. In the staircase test none of the treatments improved food pellet retrieval with the contralateral forepaw. Altogether, these results show that chronic treatment with caffeine, at doses similar to daily human consumption, produces a sustained improvement in the use of the contralateral forelimb in unilaterally 6-hydroxydopamine denervated rats, without the development of tolerance. Although the combined administration of caffeine plus trihexyphenidyl showed no synergism in these models, the results suggest that low doses of caffeine (1–3 mg/kg/day) could be of therapeutic value for the reversal of motor symptoms in parkinsonian patients.

Dietary supplements for football

Physical training and competition in football markedly increase the need for macro- and micronutrient intake. This requirement can generally be met by dietary management without the need for dietary supplemens. In fact, the efficacy of most supplements available on the market is unproven. In addition, players must be cautious of inadequate product labelling and supplement impurities that may cause a positive drug test. Nonetheless, a number of dietary supplements may beneficially affect football performance. A high endurance capacity is a prerequisite for optimal match performance, particularly if extra time is played. In this context, the potential of low-dose caffeine ingestion (2 – 5 mg · kg body mass−1) to enhance endurance performance is well established. However, in the case of football, care must be taken not to overdose because visual information processing might be impaired. Scoring and preventing goals as a rule requires production of high power output. Dietary creatine supplementation (loading dose: 15 – 20 g · day−1, 4 – 5 days; maintenance dose: 2 – 5 g g · day−1) has been found to increase muscle power output, especially during intermittent sprint exercises. Furthermore, creatine intake can augment muscle adaptations to resistance training. Team success and performance also depend on player availability, and thus injury prevention and health maintenance. Glucosamine or chondroitin may be useful in the treatment of joint pain and osteoarthritis, but there is no evidence to support the view that the administration of these supplements will be preventative. Ephedra-containing weight-loss cocktails should certainly be avoided due to reported adverse health effects and positive doping outcomes. Finally, the efficacy of antioxidant or vitamin C intake in excess of the normal recommended dietary dose is equivocal. Responses to dietary supplements can vary substantially between individuals, and therefore the ingestion of any supplement must be assessed in training before being used in competition. It is recommended that dietary supplements are only used based on the advice of a qualified sports nutrition professional.