The study was designed to determine what type of potentiation,.if any, occurred between caffeine and acetazolamide. Caffeine (75 mg/kg) and/or acetazolamide (200, 1000, or 1500 mg/kg) were administered to pregnant C57BL/6J dams on day 9 of gestation. Fetuses were removed on the eighteenth day of gestation via cesarean section and examined for gross morphological malformations using a Bausch & Lomb SKV1070P dissecting microscope. Treatment with HD-ACZM and HD+CAFF resulted in a reduction of fetal weight. Maternal exposure to MD-ACZM and HD-ACZM caused a statistically significant (P < .001) and dose-dependent increase in the percent of C57BL/6J fetuses with ectrodactyly along with increased severity of the defects displayed (relative to controls). An increase in the number of ectrodactylous fetuses and the severity of defects was also observed in all groups administered caffeine and acetazolamide, reaching statistical significance in the MD+CAFF and HD+CAFF groups (P < .001). Because potentiation of the teratogenic effects of acetazolamide was exhibited only in the MD+CAFF vs. MD-ACZM groups, the type of potentiation occurring between caffeine and acetazolamide can not be determined. / Department of Physiology and Health Science

The influence of caffeine on the metabolic and catecholamine responses to mild exercise in a cold and a warm environment was studied in eight healthy males. The subjects performed 60 minutes of cycling at 50% VO2max in a cold environment (5°C and 70% relative humidity) and a warm environment (28°C and 50% relative humidity) 30 minutes after ingesting caffeine (5mg/kg body weight) or placebo (dextrose). Caffeine ingestion prior to exercise in the warm environment resulted in increased plasma epinephrine, with no effect on plasma norepinephrine. Neither lipid nor carbohydrate metabolism was altered by caffeine in the warm trial. Exercise in the cold environment (placebo) produced increased oxygen consumption and carbohydrate metabolism, decreased lipid metabolism, and no difference in plasma catecholamines compared with the warm-placebo trial. Responses to the combination of caffeine ingestion and the cold environment did not differ from cold-placebo responses in oxygen consumption or respiratory exchange ratio during the cycling bout. However, in the cold-caffeine trial plasma epinephrine was elevated. In addition, fat oxidation, serum free fatty acids, and serum glycerol were elevated in the cold-caffeine condition. Carbohydrate oxidation was depressed, while serum glucose and blood lactate were elevated in this trial. The results of this study indicate that caffeine increases plasma epinephrine; cold increases oxygen consumption and carbohydrate metabolism, while decreasing lipid metabolism; and the combination of caffeine and cold during exercise increases plasma epinephrine and lipid metabolism, but decreases carbohydrate metabolism. / Human Performance Laboratory

This study was designed to determine if highly caffeine sensitive (HS) and less caffeine sensitive (LS) individuals differ in metabolic substrate use and endurance performance following caffeine ingestion. Twenty subjects were placed into HS and LS groups based on a series of 6 isokinetic cycle ergometer rides in which perceived exertion was held constant and work output was measured. Subjects who performed significantly more work following caffeine ingestion were classified as HS while those who did not were classified as LS. Seven subjects were selected from each of these groups to perform the experimental trials. These trials were conducted 60 min after ingestion of 6 mg-kg-1 caffeine or a placebo and consisted of a 30 min ride at70% VO2max followed by a 60 min isokinetic performance ride. The HS group achieved a higher accumulated workload over the last 30 min of the ride following caffeine ingestion compared to the placebo condition. No increase in work output was observed in the LS group following caffeine ingestion. There were no significant differences between treatments in either the HS or LS group in amount of muscle glycogen utilized during the first 30 min of the ride. During the caffeine trials serum glucose was elevated at 20, 30, and 50 min, free fatty acid concentration was elevated at the zero time point, and glycerol concentration was elevated at 60 and 90 min compared to the placebo trials. However, there were no differences between the HS and LS groups in these parameters. These data suggest that the ergogenic effects of caffeine in some individuals are not due to an alteration in substrate utilization, but may be related to an alteration in neural perception of effort. / School of Physical Education

This study was designed to determine the effect of caffeine on the teratogenicity of acetazolamide in susceptible and resistant strains of inbred mice. The highly susceptible C57BL/6J and more resistant SWV strain were used. Pregnant C57BL/6J and SWV mice were treated with caffeine, low or high dose acetazolamide, or a combination of both agents during the sensitive period of development. Untreated and vehicle-treated groups served as controls. Individual fetuses were examined for gross morphological abnormalities and skeletal variations.Findings1. A highly significant (P<.001) increase in fetal malformations, especially right forelimb ectrodactyly, was evident in C57BL/6J litters exposed on day 9 of gestation to both agents when contrasted with those exposed to either agent alone. Both frequency and severity of ectrodactyly was potentiated by caffeine.2. The SWV strain was resistant to the interaction of caffeine and acetazolamide when treated on day 9 of gestation. However, a highly significant (P<.001) increase in the rate of fetal malformation was found in litters whose dams were treated with high dose acetazolamide and caffeine on day 8 of gestation. The most common malformations observed were exencephaly and umbilical hernia.3. No differences in maternal mortality, fetal weight, litter size, or embryo mortality could be attributed to treatment in either strain.4. Skeletal examination of the number of ossified cervical and caudal vertebral centra revealed a reduction in ossification among C57BL/6J litters exposed to high dose acetazolamide or acetazolamide plus caffeine. These same centers of ossification were mildly affected by treatment in the SWV strain. In both strains the first cervical vertebrae (Cl) appeared to provide the most sensitive index of teratogenic exposure.ConclusionsThis study provides evidence that a subteratogenic dose of caffeine can potentiate the teratogenic effect of acetazolamide in both C57BL/6J and SWV mice. However, strain associated, and therefore genetically based, differences in sensitivity were confirmed. Skeletal examinations provided evidence that treatment with both agents delayed fetal development in the more susceptible C57BL/6J strain, while reduction of ossification was less evident in the SWV strain. Thus, this parameter also reflects the greater resistance of the SWV strain to the interaction of acetazolamide and caffeine. Finally, these experiments support the idea that chemical interactions may, in part, be responsible for many birth defects of unknown etiology--a claim worthy of further investigation. / Department of Biology

The improvement of physical performance has long been a problem of great importance to athletes, coaches, and physical educators. Many different methods and techniques of coaching, conditioning, and motivation have been utilized in an effort to push the participant to his top or ultimate performance. There is much conjecture as to whether this optimum or top level of performance can be raised by artificial stimulation after peak condition has been reached and the skills involved in the performance have been mastered. According to Boke, stimulants are widely used today by athletes in all types of competition. He groups the substances used into four classes: (a Food preparations, including the sugars, vitamins, phosphates, and salts; (b) Oxygen; (c) Artificial sunshine; and (d) Pharmaceutical substances, including the ‘dopes’ which influence the nervous system, heart, and circulation.

No description available.

Several studies have shown that the loss in tension during fatigue can be virtually reversed by exposure of the muscle to agents which evoke Ca²⁺ release from the SR. The purpose of this study was to determine whether the SR Ca²⁺ release mechanism of fatigued muscle is less sensitive to caffeine than that of rested muscle. Following a fatigue bout of electrically evoked tetanic pulses, the functioning of the SR of chemically skinned muscle fibers was determined by the sensitivity of the SR to increasing concentrations of caffeine. Measurements of tension and rate of tension development were made at the maximal Ca²⁺ activated contracture(pCa4.5), the maximal caffeine(25mM) activated contracture and at the caffeine threshold for contraction. All tension and rate values were normalized per cross sectional area and expressed as percents of the maximal calcium activated values. Results of the maximal Ca²⁺ and caffeine data suggest that the both control and fatigue fibers are similar in maximal tension and Ca²⁺ loading characteristics. While no differences were found between rested or fatigued maximal Ca²⁺ or caffeine contractures, significant difference was found at the caffeine threshold (p<.05) with the fatigued muscle tending to contract at a higher caffeine concentration. This suggests that fatigued muscle is less sensitive to the caffeine stimulus for Ca²⁺ release from the SR. / Master of Science

Caffeine's effect on the visual system was investigated. Twelve male and twelve female subjects (aged 18 - 25 years) were measured for Critical Flicker Frequency (CFF) thresholds at 15 levels of retinal illuminance (-1.0 to 3.0 log trolands) in each of four caffeine dosage conditions (0, 200mg, 400mg, 600mg). Variables of interest included dosage, gender, left and right eye differences, and time after ingestion. Significant results were found for dosage (p=.000), gender (p=.001), and eye differences (p=.000). Interactions were found for gender and dosage (p=.000), and gender and eye differences (p=.043). Implications of these findings are discussed in terms of caffeine's effect on the Central Nervous System (CNS) and corresponding effects on the visual system. It is concluded that ingestion of caffeine causes increased sensitivity of the visual system as displayed through lower Critical Flicker Frequency thresholds. / Master of Science

Call number: LD2668 .T4 1984 W43 / Master of Science

Thesis (PhD)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: Background: Abundant evidence supporting the ergogenic effect of caffeine during endurance exercise exists. Single sporting events, laboratory based studies and inappropriate research design questions the applicability of these studies to triathlon performance. Objectives: The main aims of this study were to i) investigate the ergogenic effect of caffeine supplementation during a triathlon; ii) evaluate parameters that could in part explain why caffeine supplementation is ergogenic, iii) investigate possible factors influencing the ergogenicity of caffeine supplementation and iv) investigate possible confounding factors influencing triathlon performance. Methods: A double-blind, randomized, crossover, controlled, clinical field trial was conducted. Performance data (time to complete (TTC), rating of perceived exertion (RPE) and mood state), parameters explaining the mechanism of action (endocrine-stress response, oxidative stress and plasma lactate), factors influencing ergogenicity (lifestyle, gender and genetics) and triathlon performance (general health, energy- and nutrient intake, body composition, training regime, side-effects of caffeine withdrawal- and supplementation and hydration status) was collected during two Olympic-distance triathlons (T1 and T2). Results: Twenty six Caucasian triathletes (Nm=14, Nf=12) participated (age: 37.8±10.6 years, habitual caffeine intake: 412.7±504.8 mg/day, percentage body fat: 14.5±7.2 %, training/week: 12.8±4.5 hours). There was a 3.7% reduction in swim time (33.5±7.0 vs. 34.8±8.1 minutes) (p=0.05*) and a 1.3% reduction in the overall time to complete the triathlon (149.6±19.8 vs. 151.5±18.6 minutes) (p=0.02*) in the caffeine group. Caffeine did not statistically influence mood state (p=0.72) or RPE (p=0.87), however, a trend was observed for decreased RPE values in the caffeine group. Caffeine supplementation made no difference to markers of endocrine-stress, except for cortisol, which increased beyond the effect observed from exercise (p=0.00*). Oxidative stress was more pronounced in the caffeine group, as seen with elevated leukocyte (p=0.05*), lymphocyte (p=0.05*) and monocyte (p = 0.05*) counts. Caffeine facilitated greater blood lactate accumulation (p=0.04*). Lifestyle, menstrual cycle, menopause, oral contraceptive use and CYP1A2 gene polymorphisms did not statistically influence the effect of caffeine supplementation on triathlon performance. The mean energy- and nutrient intake two days before T1 and T2 was low for energy (36.5±17.6 and 38.9±18.2 kcal/kg BW), estimated energy availability (estEA) (27.9±28.0 and 28.8±25.6 kcal/kg fat free mass) and carbohydrate (CHO) intake (4.1±1.6 and 4.6±2.5 g/kg body weight (BW)) compared to recommendations. The pre-event meal was low in CHO (0.7±0.4 and 0.7±0.5 g/kg BW) and only 62% (N=16) ingested a carbohydrate-electrolyte solution during T1 (CHO: 1.6±2.3 g/kg BW) and T2 (CHO: 0.7±0.4 g/kg BW). Eighty-five percent (N=22) used supplements. Seventy-two percent of pre-menopausal (Nf pre-men=5) and 40% of post-menopausal (Nf post-men=2) females were osteopenic. Of the males, 18% (Nm<50 = 2) had low anterior-posterior spine BMD and 33% (Nm>50 = 1) were osteopenic. Caffeine withdrawal presented as headaches (46%, N=12) and flu-like symptoms (38%, N=10). Side effects of caffeine experienced included shakiness (42%, N=11), heart palpitations (38%, N=10) and gastrointestinal disturbances (38%, N=10). Plasma volume and hydration was not influenced (p=0.70). Conclusion: Caffeine enhanced triathlon performance, but the effect was not as pronounced as seen in previous laboratory trials and did not affect RPE or mood state. Caffeine supplementation augments the endocrine-stress response by further increasing cortisol levels beyond that resulting from endurance exercise and it induces leukocytosis, neutrophillia and lymphocytosis, suggesting the primary ergogenic effect of caffeine may result due to stimulation of both the central and autonomic nervous systems. Lifestyle, gender and genetics did not significantly influence caffeine’s effect on triathlon performance in this cohort. The subjects had low energy, estEA and carbohydrate intake and a high prevalence of osteopenia. / AFRIKAANSE OPSOMMING: Agtergrond: Voldoende bewyse rakende die ergogeniese effek van kaffeïen gedurende uithouvermoë oefening bestaan. Enkel sportsoorte, laboratorium studies en ongeskikte navorsingsontwerpe bevraagteken die toepaslikheid van hierdie studies op driekamp prestasie. Doelwitte: Die hoofdoelwitte van die studie was om i) die verbetering van prestasie of ergogeniese effek van kaffeïen supplementasie tydens ‘n driekamp kompetisie waar te neem; ii) om verskeie parameters wat die ergogeniese effek van kaffeïen supplementasie deels te verduidelik te ondersoek, iii) om moontlike faktore wat die ergogeniese effek van kaffeïen supplementasie kan beïnvloed te ondersoek en iv) om moontlike faktore wat Olimpiese-afstand driekamp prestasie kan beïnvloed te ondersoek. Metodes: ‘n Dubbel-blinde, lukrake, oorkruis, gekontroleerde, kliniese veldproef is uitgevoer. Prestasie data (tyd om die driekampe te voltooi, waargenome inspanning en gemoedstoestand), parameters wat moontlik die aksie van kaffeïen kan verduidelik (endokrien-stress respons, oksidatiewe stress en plasma laktaat), faktore wat die ergogeniese effek van kaffeïen kan beïnvloed (lewensstyl, geslag en genetika) en faktore wat moontlik driekamp prestasie kan beïnvloed (algemene gesondheid, energie- en nutriëntinname twee dae voor en op die dag van die driekampe, liggaamsamestelling en beendigtheid, oefening twee dae voord die driekampe, newe-effekte van kaffeïen ontrekking- en supplementasie en hidrasie status) is ingesamel tydens twee Olimpiese afstand driekampe (T1 en T2). Resultate: Ses-en-twintig Kaukasiese driekamp atlete (Nm=14, Nf=12) is ingesluit (ouderdom: 37.8±10.6, daaglikse kaffeïen inname: 412.7±504.8 mg/dag, % liggaamsvet: 14.5±7.2%, oefening/week: 12.8±4.5 uur). Daar was 'n 3.7% afname in swem tyd (33.5±7.0 teenoor 34.8±8.1) (p=0.05*) en 'n 1.3% afname in totale tyd om die driekampe te voltooi (149.6±19.8 teenoor 151.5±18.6) (p=0.02*) in die kaffeïen groep. Kaffeïen het nie ‘n statisties beduidende effek op die gemoedstoestand (p=0.72) of die waargenome inspanning (p=0.87) gehad nie, maar 'n tendens is waargeneem vir laer waargenome inspannings-waardes in die kaffeïen groep. Kaffeïen het geen verskil gemaak aan parameters van die stres respons nie, behalwe vir kortisol, wat verhoog het bo- en behalwe die effek van oefening (p=0.00*). Oksitdatiewe stres was meer uitgesproke in die kaffeïen groep, soos waargeneem deur verhoogde witbloedsel (p=0.05*), limfosiet (p=0.05*) en neutrofiel (p = 0.05*) tellings. Kaffeïen fasiliteer die verhoging in bloedlaktaat vlakke (p=0.04*). Lewensstyl, menstruele siklus, menopause, orale voorbehoedmiddel gebruik en CYP1A2 geen polimorfismes het geen beduidende effek op die vermoë van kaffeïen om driekamp prestasie te beïnvloed gehad nie. Die gemiddelde energie- en nutriëntinname twee dae voor T1 en T2 was laer as die aanbevelings vir energie (36.5±17.6 en 38.9±18.2 kcal/kg LG), geskatte energie beskikbaarheid (29.9±28.0 en 28.8±25.6 kcal/kg vetvrye massa) en koolhidraat (CHO) inname (4.1±1.6 en 4.6±2.5 g/kg LG). Die voor-driekamp ete was laag in CHO (0.7±0,4 en 0.7±0.5 g / kg LG) en slegs 62% (N=16) het ‘n koolhidraat-elektroliet oplossing tydens T1 (CHO: 1.6±2.3 g/kg LG) en T2 (CHO: 0.7±0.4 g/kg LG) ingeneem. Vyf-en-tagtig persent (N=22) gebruik dieetaanvullings. Twee-en-sewentig persent van die pre-menopausale (Nf pre-men=5) en 40% van die post-menopausale (Nf post-men=2) vroue het osteopenie volgens die totale liggaams been mineraal digtheid. Van die mans, het 18% (Nm<50 = 2) met lae beendigtheid van die anterior-posterior spina en 33% (Nm>50 = 1) met osteopenie gepresenteer. Waargenome ontrekkingsimptome van kaffeïen was hoofpyn (46%, N=12) en griepagtige simptome (38%, N=10) en newe-effekte was bewerigheid (42%, N=11), hartkloppings (38%, N=10) en spysverteringskanaal versteurings (38%, N=10). Plasma volume en hidrasie was nie beïnvloed nie (p=0.70). Gevolgtrekking: Kaffeïen verbeter driekamp prestasie, maar die effek is nie so uitgesproke soos waargeneem tydens laboratorium studies nie en het nie ‘n beduidende effek op waargenome inspanning of gemoedstoestand getoon nie. Kaffeïen verhoog die stres respons deur die verdere verhoging van kortisol vlakke, bo- en behalwe vlakke waargeneem tydens uithouvermoë oefening en verhoog witbloedsel, limfosiet en neutrofiel tellings. Dit dui daarop dat die primêre ergogeniese effek van kaffeïen supplementasie moontlik as gevolg van stimulasie van beide die sentrale en autonome senuweestelsel voorkom. Lewensstyl, geslag en genetika het nie ‘n beduidende effek op die ergogeniese vermoë van kaffeïen getoon in hierdie studiepopulasie nie. Die deelnemers het ‘n lae energie, geskatte energie beskikbaarheid en koolhidraatinname gehad. Die studiegroep het ‘n hoë prevalensie van osteopenie.