Cadence Classic Energy Gel has been formulated to provide the energy and nutrient requirements for athletes training and racing over a variety of distances.
Carbohydrate and fat are the two primary fuel sources used by muscle tissue during prolonged (endurance-type) exercise. The relative contribution of these fuel sources largely depends on the exercise intensity and duration, with a greater contribution from carbohydrate as exercise intensity is increased. Consequently, endurance performance and endurance capacity are largely dictated by endogenous (ingested) carbohydrate availability. As such, improving carbohydrate availability during prolonged exercise through carbohydrate ingestion has dominated the field of sports nutrition research. As a result, it has been well-established that carbohydrate ingestion during prolonged (>2 h) moderate-to-high intensity exercise can significantly improve endurance performance. Although the precise mechanisms responsible for the ergogenic effects are still unclear, they are most likely related to the sparing of skeletal muscle glycogen, prevention of liver glycogen depletion and subsequent development of hypoglycemia. Currently, for prolonged exercise lasting 2 3 h, athletes are advised to ingest carbohydrates at a rate of 60 gh-1 (1.0 1.1 gmin-1) to allow for maximal exogenous glucose oxidation rates. However, well-trained endurance athletes competing longer than 2.5 h can metabolize carbohydrate up to 90 gh-1 (1.5 1.8 gmin-1) provided that multiple transportable carbohydrates are ingested (e.g. 1.2 gmin-1 glucose plus 0.6 gmin-1 of fructose). Surprisingly, small amounts of carbohydrate ingestion during exercise may also enhance the performance of shorter (45 60 min), more intense (>75 % peak oxygen uptake; VO2peak) exercise bouts, despite the fact that endogenous carbohydrate stores are unlikely to be limiting. The mechanism(s) responsible for such ergogenic properties of carbohydrate ingestion during short, more intense exercise bouts has been suggested to reside in the central nervous system. Carbohydrate ingestion during exercise also benefits athletes involved in intermittent/team sports. These athletes are advised to follow similar carbohydrate feeding strategies as the endurance athletes, but need to modify exogenous carbohydrate intake based upon the intensity and duration of the game and the available endogenous carbohydrate stores
Optimal balance of maltodextrin and fructose (2:1). Numerous studies show that combining fructose with maltodextrin improves exercise performance, maximises gastric emptying rate and increases fluid absorption rate, delaying fatigue and delaying the onset of dehydration.
Am J Physiol Gastrointest Liver Physiol. 2011 Jan;300(1):G181-9
Fructose-maltodextrin ratio in a carbohydrate-electrolyte solution differentially affects exogenous carbohydrate oxidation rate, gut comfort, and performance.
School of Sport and Exercise, Massey University, Wellington, New Zealand.
Solutions containing multiple carbohydrates utilizing different intestinal transporters (glucose and fructose) show enhanced absorption, oxidation, and performance compared with single-carbohydrate solutions, but the impact of the ratio of these carbohydrates on outcomes is unknown. In a randomized double-blind crossover, 10 cyclists rode 150 min at 50% peak power, then performed an incremental test to exhaustion, while ingesting artificially sweetened water or one of three carbohydrate-salt solutions comprising fructose and maltodextrin in the respective following concentrations: 4.5 and 9% (0.5-Ratio), 6 and 7.5% (0.8-Ratio), and 7.5 and 6% (1.25-Ratio). The carbohydrates were ingested at 1.8 g/min and naturally (13)C-enriched to permit evaluation of oxidation rate by mass spectrometry and indirect calorimetry. Mean exogenous carbohydrate oxidation rates were 1.04, 1.14, and 1.05 g/min (coefficient of variation 20%) in 0.5-, 0.8-, and 1.25-Ratios, respectively, representing likely small increases in 0.8-Ratio of 11% (90% confidence limits; +/- 4%) and 10% (+/- 4%) relative to 0.5- and 1.25-Ratios, respectively. Comparisons of fat and total and endogenous carbohydrate oxidation rates between solutions were unclear. Relative to 0.5-Ratio, there were moderate improvements to peak power with 0.8- (3.6%; 99% confidence limits +/- 3.5%) and 1.25-Ratio (3.0%; +/- 3.7%) but unclear with water (0.4%; +/- 4.4%). Increases in stomach fullness, abdominal cramping, and nausea were lowest with the 0.8- followed by the 1.25-Ratio solution. At high carbohydrate-ingestion rate, greater benefits to endurance performance may result from ingestion of 0.8- to 1.25-Ratio fructose-maltodextrin solutions. Small perceptible improvements in gut comfort favor the 0.8-Ratio and provide a clearer suggestion of mechanism than the relationship with exogenous carbohydrate oxidation.
Scand J Med Sci Sports. 2010 Feb;20(1):112-21
Multiple transportable carbohydrates enhance gastric emptying and fluid delivery.
Human Performance Laboratory, Department of Exercise Metabolism, School of Sport and Exercise Sciences, The University of Birmingham, Edgbaston, Birmingham, UK.
This study compared the effects of ingesting water (WATER), an 8.6% glucose solution (GLU) and an 8.6% glucose+fructose solution (2:1 ratio, GLU+FRU) on gastric emptying (GE), fluid delivery, and markers of hydration status during moderate intensity exercise. Eight male subjects (age=24 +/- 2 years, weight=74.5 +/- 1.2 kg, VO(2max)=62.6 +/- 2.5 mL/kg/min) performed three 120 min cycling bouts at 61% VO(2max)). Subjects ingested GLU, GLU+FRU (both delivering 1.5 g/min carbohydrate), or WATER throughout exercise, ingesting 2.1 L. Serial dye dilution measurements of GE were made throughout exercise and subjects ingested 5.00 g of D(2)O and 150 mg of (13)C-acetate at 60 min to obtain measures of fluid uptake and GE, respectively. GLU+FRU resulted in faster rates of deuterium accumulation, an earlier time to peak in the (13)C enrichment of expired air and a faster rate of GE compared with GLU. GLU+FRU also attenuated the rise in heart rate that occurred in GLU and WATER and resulted in lower ratings of perceived exertion. There was a greater loss in body weight with GLU corrected for fluid intake. These data suggest that ingestion of a combined GLU+FRU solution increases GE and “fluid delivery” compared with a glucose only solution.
J Appl Physiol. 2008 Jun;104(6):1709-19. Epub 2008 Mar 27.
Effect of graded fructose coingestion with maltodextrin on exogenous 14C-fructose and 13C-glucose oxidation efficiency and high-intensity cycling performance.
Institute of Food, Nutrition, and Human Health, Massey Univ., Wellington, New Zealand.
The ingestion of solutions containing carbohydrates with different intestinal transport mechanisms (e.g., fructose and glucose) produce greater carbohydrate and water absorption compared with single-carbohydrate solutions. However, the fructose-ingestion rate that results in the most efficient use of exogenous carbohydrate when glucose is ingested below absorption-oxidation saturation rates is unknown. Ten cyclists rode 2 h at 50% of peak power then performed 10 maximal sprints while ingesting solutions containing (13)C-maltodextrin at 0.6 g/min combined with (14)C-fructose at 0.0 (No-Fructose), 0.3 (Low-Fructose), 0.5 (Medium-Fructose), or 0.7 (High-Fructose) g/min, giving fructose:maltodextrin ratios of 0.5, 0. 8, and 1.2. Mean (percent coefficient of variation) exogenous-fructose oxidation rates during the 2-h rides were 0.18 (19), 0.27 (27), 0.36 (27) g/min in Low-Fructose, Medium-Fructose, and High-Fructose, respectively, with oxidation efficiencies (=oxidation/ingestion rate) of 62-52%. Exogenous-glucose oxidation was highest in Medium-Fructose at 0.57 (28) g/min (98% efficiency) compared with 0.54 (28), 0.48 (29), and 0.49 (19) in Low-Fructose, High-Fructose, No-Fructose, respectively; relative to No-Fructose, only the substantial 16% increase (95% confidence limits +/-16%) in Medium-Fructose was clear. Total exogenous-carbohydrate oxidation was highest in Medium-Fructose at 0.84 (26) g/min. Although the effect of fructose quantity on overall sprint power was unclear, the metabolic responses were associated with lower perceptions of muscle tiredness and physical exertion, and attenuated fatigue (power slope) in the Medium-Fructose and High-Fructose conditions. With the present solutions, low-medium fructose-ingestion rates produced the most efficient use of exogenous carbohydrate, but fatigue and the perception of exercise stress and nausea are reduced with moderate-high fructose doses.
Med Sci Sports Exerc. 2008 Feb;40(2):275-81.
Superior endurance performance with ingestion of multiple transportable carbohydrates.
Human Performance Laboratory, School of Sport and Exercise Sciences, University of Birmingham, Birmingham, UK.
INTRODUCTION: The aim of the present study was to investigate the effect of ingesting a glucose plus fructose drink compared with a glucose-only drink (both delivering carbohydrate at a rate of 1.8 g.min(-1)) and a water placebo on endurance performance. METHODS: Eight male trained cyclists were recruited (age 32 +/- 7 yr, weight 84.4 +/- 6.9 kg, .VO(2max) 64.7 +/- 3.9 mL.kg(-1).min(-1), Wmax 364 +/- 31 W). Subjects ingested either a water placebo (P), a glucose (G)-only beverage (1.8 g.min(-1)), or a glucose and fructose (GF) beverage in a 2:1 ratio (1.8 g.min(-1)) during 120 min of cycling exercise at 55% Wmax followed by a time trial in which subjects had to complete a set amount of work as quickly as possible (approximately 1 h). Every 15 min, expired gases were analyzed and blood samples were collected. RESULTS: Ingestion of GF resulted in an 8% quicker time to completion during the time trial (4022 s) compared with G (3641 s) and a 19% improvement compared with W (3367 s). Total carbohydrate (CHO) oxidation was not different between GF (2.54 +/- 0.25 g.min(-1)) and G (2.50 g.min(-1)), suggesting that GF led to a sparing of endogenous CHO stores, because GF has been shown to have a greater exogenous CHO oxidation than G. CONCLUSION: Ingestion of GF led to an 8% improvement in cycling time-trial performance compared with ingestion of G.
J Appl Physiol. 2006 Apr;100(4):1134-41. Epub 2005 Dec 1.
Exogenous carbohydrate oxidation during ultraendurance exercise.
Human Performance Laboratory, School of Sport and Exercise Sciences, University of Birmingham, Edgbaston, Birmingham B15 2TT, United Kingdom. A.E.Jeukendrup@bham.ac.uk
The purposes of this study were: 1) to obtain a measure of exogenous carbohydrate (CHO(Exo)) oxidation and plasma glucose kinetics during 5 h of exercise; and 2) to compare CHO(Exo) following the ingestion of a glucose solution (Glu) or a glucose + fructose solution (2:1 ratio, Glu+Fru) during ultraendurance exercise. Eight well-trained subjects exercised three times for 5 h at 58% maximum O2 consumption while ingesting either Glu or Glu+Fru (both delivering 1.5 g/min CHO) or water. The CHO used had a naturally high 13C enrichment, and five subjects received a primed continuous intravenous [6,6-2H2]glucose infusion. CHO(Exo) rates following the ingestion of Glu leveled off after 120 min and peaked at 1.24 +/- 0.04 g/min. The ingestion of Glu+Fru resulted in a significantly higher peak rate of CHO(Exo) (1.40 +/- 0.08 g/min), a faster rate of increase in CHO(Exo), and an increase in the percentage of CHO(Exo) oxidized (65-77%). However, the rate of appearance and disappearance of Glu continued to increase during exercise, with no differences between trials. These data suggest an important role for gluconeogenesis during the later stages of exercise. Following the ingestion of Glu+Fru, cadence (rpm) was maintained, and the perception of stomach fullness was reduced relative to Glu. The ingestion of Glu+Fru increases CHO(Exo) compared with the ingestion of Glu alone, potentially through the oxidation of CHO(Exo) in the liver or through the conversion to, and oxidation of, lactate.
Taurine supplementation improves exercise performance and reduces exercise induced muscle damage.
Amino Acids. 2004 Mar;26(2):203-7. Epub 2003 May 9.
Role of taurine supplementation to prevent exercise-induced oxidative stress in healthy young men.
Department of Welfare Promotion and Epidemiology, Faculty of Medicine, Toyama Medical and Pharmaceutical University, Toyama, Japan.
To evaluate the protective effects of taurine supplementation on exercise-induced oxidative stress and exercise performance, eleven men aged 18-20 years were selected to participate in two identical bicycle ergometer exercises until exhaustion. Single cell gel assay (SCG assay) was used to study DNA damage in white blood cells (WBC). Pre-supplementation of taurine, a significant negative correlation was found between plasma taurine concentration before exercise and plasma thiobaribituric-acid reactive substance (TBARS) 6 hr after exercise (r = -0.642, p<0.05). WBC showed a significant increase in DNA strand breakage 6 hr and 24 hr after exercise. Seven-day taurine supplementation reduced serum TBARS before exercise ( p<0.05) and resulted in a significantly reduced DNA migration 24 hr after exercise ( p<0.01). Significant increases were also found in VO(2)max, exercise time to exhaustion and maximal workload in test with taurine supplementation ( p<0.05). After supplementation, the change in taurine concentration showed positive correlations with the changes in exercise time to exhaustion and maximal workload. The results suggest that taurine may attenuate exercise-induced DNA damage and enhance the capacity of exercise due to its cellular protective properties.
Amino Acids. 2002 Jun;22(4):309-24
The cytoprotective role of taurine in exercise-induced muscle injury.
Department of Pharmacodynamics, College of Pharmacy, JHMHC Box 100487, University of Florida, Gainesville, FL 32610, U.S.A. firstname.lastname@example.org
Intense exercise is thought to increase oxidative stress and damage muscle tissue. Taurine is present in high concentration in skeletal muscle and may play a role in cellular defenses against free radical-mediated damage. The aim of this study was to determine if manipulating muscle levels of taurine would alter markers of free radical damage after exercise-induced injury. Adult male Sprague-Dawley rats were supplemented via the drinking water with either 3% (w/v) taurine (n = 10) or the competitive taurine transport inhibitor, beta-alanine (n = 10), for one month. Controls (n = 20) drank tap water containing 0.02% taurine and all rats were placed on a taurine free diet. All the rats except one group of sedentary controls (n = 10) were subjected to 90 minutes of downhill treadmill running. Markers of cellular injury and free radical damage were determined along with tissue amino acid content. The 3% taurine treatment raised plasma levels about 2-fold and 3% beta-alanine reduced plasma taurine levels about 50%. Taurine supplementation (TS) significantly increased plasma glutamate levels in exercised rats. Exercise reduced plasma methionine levels and taurine prevented its decline. Taurine supplementation increased muscle taurine content significantly in all muscles except the soleus. beta-alanine decreased muscle taurine content about 50% in all the muscles examined. Lipid peroxidation (TBARS) was significantly increased by exercise in the extensor digitorium longus (EDL) and gastrocnemius (GAST) muscles. Both taurine and beta-alanine completely blocked the increase in TBARs in the EDL, but had no effect in the GAST. Muscle content of the cytosolic enzyme, lactate dehydrogenase (LDH) was significantly decreased by exercise in the GAST muscle and this effect was attenuated by both taurine and beta-alanine. Muscle myeloperoxidase (MPO) activity was significantly elevated in the gastrocnemius muscle, but diet had no effect. MPO activity was significantly increased by exercise in the liver and both taurine and beta-alanine blocked this effect. There was no effect of either exercise or the diets on MPO activity in the lung or spleen. Running performance as assessed by a subjective rating scale was improved by taurine supplementation and there was a significant loss in body weight in the beta-alanine-treated rats 24 hours after exercise. In summary, taurine supplementation or taurine depletion had measurable cytoprotective actions to attenuate exercise-induced injury.
Int J Sports Med. 2009 Jul;30(7):485-8. Epub 2009 May 19.
Caffeine and taurine enhance endurance performance.
Doctoral Program of Sports Medicine, University of Tsukuba, GSCHS, 1-1-1 D507, Tennoudai, Ibaraki, Tsukuba 305-8577, Japan. email@example.com
Caffeine enhances endurance performance; however, its effect on accumulated lactate remains unclear. Conversely, taurine, which also enhances endurance performance, decreases accumulated lactate. In this study, the effect of combination of caffeine and taurine on endurance performance was assessed. Mice ran on a treadmill, and the accumulated lactate was measured. In addition, muscle fibers from the gastrocnemius muscle of the mice were stained with ATPase and analyzed. The use of caffeine and taurine over a 2 week period enhanced endurance performance. Moreover, taurine significantly decreased the accumulated concentration of lactate over long running distances. However, the diameter of the cross-sections and ratios of Types I, IIA, and IIB muscle fibers were not affected.
Phosphate supplementation and loading enhance myocardial function, improve exercise performance and increase exercise oxidative capacity.
Int J Sport Nutr. 1992 Mar;2(1):20-47
Effects of phosphate loading on metabolic and myocardial responses to maximal and endurance exercise.
Dept. of HPER, Old Dominion University, Norfolk, VA 23529-0196.
Six trained male cyclists and triathletes participated in a double blind study to determine the effects of phosphate loading on maximal and endurance exercise performance. Subjects ingested either 1 gm of tribasic sodium phosphate or a glucose placebo four times daily for 3 days prior to performing either an incremental maximal cycling test or a simulated 40-km time trial on a computerized race simulator. They continued the supplementation protocol for an additional day and then performed the remaining maximal or performance exercise test. Subjects observed a 17-day washout period between testing sessions and repeated the experiment with the alternate supplement regimen in identical fashion. Metabolic data were collected at 15-sec intervals while venous blood samples and 2D-echocardiographic data were collected during each stage of exercise during the maximal exercise test and at 8-km intervals during the 40-km time trial. Results indicate that phosphate loading attenuated anaerobic threshold, increased myocardial ejection fraction and fractional shortening, increased maximal oxidative capacity, and enhanced endurance performance in competitive cyclists and triathletes.
J Sci Med Sport. 2008 Sep;11(5):464-8. Epub 2007 Jun 14.
Sodium phosphate loading improves laboratory cycling time-trial performance in trained cyclists.
School of Sport and Exercise Sciences, Loughborough University, UK. firstname.lastname@example.org
Sodium phosphate loading has been reported to increase maximal oxygen uptake (6-12%), however its influence on endurance performance has been ambiguous. The aim of this study was to examine the influence of sodium phosphate loading on laboratory 16.1 km cycling time-trial performance. Six trained male cyclists (V O(2) peak, 64.1+/-2.8 ml kg(-1)min(-1); mean+/-S.D.) took part in a randomised double-blind crossover study. Upon completion of a control trial (C), participants ingested either 1g of tribasic dodecahydrate sodium phosphate (SP) or lactose placebo (P) four times daily for 6 days prior to performing a 16.1 km (10 mile) cycling time-trial under laboratory conditions. Power output and heart rate were continually recorded throughout each test, and at two points during each time-trial expired air samples and capillary blood samples were taken. There was a 14-day period between each of the supplemented time-trials. After SP loading mean power was greater than for P and C (C, 322+/-15 W; P, 317+/-16 W; SP, 347+/-19 W; ANOVA, P<0.05) and time to complete the 16.1 km was shorter than P, but not C (ANOVA, P<0.05). During the SP trial, relative to the P, mean changes were mean power output +9.8+/-8.0% (+/-95% confidence interval); time -3.0+/-2.9%. There was a tendency towards higher V O(2) after SP loading (ANOVA, P = 0.07). Heart rate, V (E), RER and blood lactate concentration were not significantly affected by SP loading. Sodium phosphate loading significantly improved mean power output and 16.1 km time-trial performance of trained cyclists under laboratory conditions with functional increases in oxygen uptake.
Magnesium is an essential element is energy metabolism and cell function. Dietary intake of magnesium is often insufficient in athletic populations. Physical exercise may deplete magnesium, which, together with a marginal dietary magnesium intake, may impair energy metabolism efficiency and the capacity for physical work as well as increasing immunosupression and oxidative damage caused by exercise.
Crit Rev Food Sci Nutr. 2002;42(6):533-63.
Magnesium and exercise.
University of Massachusetts, Department of Nutrition, Amherst 01003, USA.
Magnesium is an essential element that regulates membrane stability and neuromuscular, cardiovascular, immune, and hormonal functions and is a critical cofactor in many metabolic reactions. The Dietary Reference Intake for magnesium for adults is 310 to 420 mg/day. However, the intake of magnesium in humans is often suboptimal. Magnesium deficiency may lead to changes in gastrointestinal, cardiovascular, and neuromuscular function. Physical exercise may deplete magnesium, which, together with a marginal dietary magnesium intake, may impair energy metabolism efficiency and the capacity for physical work. Magnesium assessment has been a challenge because of the absence of an accurate and convenient assessment method. Recently, magnesium has been touted as an agent for increasing athletic performance. This article reviews the various studies that have been conducted to investigate the relationship of magnesium and exercise.
Magnes Res. 2006 Sep;19(3):180-9.
Update on the relationship between magnesium and exercise.
U.S. Department of Agriculture, Agricultural Research Service, Grand Forks Human Nutrition Research Center, Grand Forks, ND 58202-9034, USA. email@example.com
Magnesium is involved in numerous processes that affect muscle function including oxygen uptake, energy production and electrolyte balance. Thus, the relationship between magnesium status and exercise has received significant research attention. This research has shown that exercise induces a redistribution of magnesium in the body to accommodate metabolic needs. There is evidence that marginal magnesium deficiency impairs exercise performance and amplifies the negative consequences of strenuous exercise (e.g., oxidative stress). Strenuous exercise apparently increases urinary and sweat losses that may increase magnesium requirements by 10-20%. Based on dietary surveys and recent human experiments, a magnesium intake less than 260 mg/day for male and 220 mg/day for female athletes may result in a magnesium-deficient status. Recent surveys also indicate that a significant number of individuals routinely have magnesium intakes that may result in a deficient status. Athletes participating in sports requiring weight control (e.g., wrestling, gymnastics) are apparently especially vulnerable to an inadequate magnesium status. Magnesium supplementation or increased dietary intake of magnesium will have beneficial effects on exercise performance in magnesium-deficient individuals. Magnesium supplementation of physically active individuals with adequate magnesium status has not been shown to enhance physical performance. An activity-linked RNI or RDA based on long-term balance data from well-controlled human experiments should be determined so that physically active individuals can ascertain whether they have a magnesium intake that may affect their performance or enhance their risk to adverse health consequences (e.g., immunosuppression, oxidative damage, arrhythmias).
Balanced electrolyte formula to optimise performance
Int J Sports Med. 1994 Oct;15(7):392-8.
Impaired high-intensity cycling performance time at low levels of dehydration.
Medical Research Council/University of Cape Town Medical School, Department of Physiology, Observatory, South Africa.
On two separate occasions six trained subjects (peak oxygen consumption [VO2peak] 4.41/min) rode for 60 min at 70% of VO2peak and then to exhaustion at 90% of VO2peak to determine the effects of mild dehydration on high-intensity cycling performance time in the heat (32 degrees C, 60% relative humidity, wind speed 3 km/h). In one trial (F) subjects ingested a 400 ml bolus of 20 mmol/l NaCl immediately before, and then as repetitive 120 ml feedings every 10 min during the first 50 min of exercise. In the other trial they did not ingest fluid (NF) either before or during exercise. The order of testing was in a counter-balanced random sequence. For the first 60 min of exercise mean (+/- SD) VO2 (2.90 +/- 0.39 vs 2.93 +/- 0.38 l/min) and respiratory exchange ratio (RER; 0.95 +/- 0.03 vs 0.94 +/- 0.04) values were similar between F and NF trials. However, weight loss was significantly reduced during F compared to NF (0.16 +/- 0.39 vs 1.30 +/- 0.22 kg; p < 0.005) and high-intensity cycling time to exhaustion was significantly increased (9.8 +/- 3.9 vs 6.8 +/- 3.0 min; p < 0.005). Increased cycling times to exhaustion in the F trial were not associated with any measurable differences in heart rate (HR), body temperature, respiratory gas exchange, leg muscle power over 5 sec, or the degree to which fluid ingestion reduced the level of dehydration within the group. Only the ratings of perceived exertion (RPE) and plasma anti diuretic hormone (ADH) concentrations were significantly increased in the NF trial compared to the F trial.(ABSTRACT TRUNCATED AT 250 WORDS)
J Physiol Pharmacol. 2009 Jun;60(2):139-43.
Assessment of the antioxidant effectiveness of alpha-lipoic acid in healthy men exposed to muscle-damaging exercise.
Department of Biochemistry and Sports Medicine, University of Physical Education Poznan, Faculty of Physical Culture, Gorzow Wlkp., Poland. firstname.lastname@example.org
The aim of this study was to compare the indices of glutathione antioxidant system and oxidative damage level in resistance trained and untrained subjects and to assess the antioxidant action of alpha-lipoic acid in trained men exposed to muscle-damaging exercise. Thirteen trained and twenty untrained men (NT) participated in the comparative study. Then trained men were randomly assigned to T(CON) group (control) or T(ALA) group (alpha-lipoic acid, 600 mg . day(-1), for 8 days) and performed isometric/isokinetic effort of quadriceps muscles. The study has shown the significantly higher erythrocyte levels of glutathione (GSH), glutathione reductase (GR) and glutathione peroxidase (GPx) in T(CON) than NT but no differences in plasma lipid peroxidation (TBARS) and protein carbonylation (PC). However, total thiol (TT) concentration was two-fold lower in T(CON) than NT group. alpha-Lipoic acid variously influenced the post-exercise levels of GSH (+40%), GR (-24%) and GPx (+29%), but markedly reduced by over 30% the resting and post-exercise TBARS and PC in T(ALA) compared with T(CON). TT concentration significantly increased in T(ALA) but it did not reach the high level which was found in untrained group. It is concluded that alpha-lipoic acid supplementation diminishes oxidative damage. It does not abolish differences in glutathione antioxidant system between untrained and trained subjects but modulates a pro-antioxidant response to the muscle-damaging exercise.
Eur J Appl Physiol. 2010 Dec;110(6):1243-50. Epub 2010 Aug 25.
Caffeinated chewing gum increases repeated sprint performance and augments increases in testosterone in competitive cyclists.
Health and Sport Science, Eastern Institute of Technology, Private Bag 1201, Taradale, Hawkes Bay, Napier, New Zealand. CPaton@eit.ac.nz
This investigation reports the effects of caffeinated chewing gum on fatigue and hormone response during repeated sprint performance with competitive cyclists. Nine male cyclists (mean +/- SD, age 24 +/- 7 years, VO(2max) 62.5 +/- 5.4 mL kg(-1) min(-1)) completed four high-intensity experimental sessions, consisting of four sets of 30 s sprints (5 sprints each set). Caffeine (240 mg) or placebo was administered via chewing gum following the second set of each experimental session. Testosterone and cortisol concentrations were assayed in saliva samples collected at rest and after each set of sprints. Mean power output in the first 10 sprints relative to the last 10 sprints declined by 5.8 +/- 4.0% in the placebo and 0.4 +/- 7.7% in the caffeine trials, respectively. The reduced fatigue in the caffeine trials equated to a 5.4% (90% confidence limit +/-3.6%, effect size 0.25; +/-0.16) performance enhancement in favour of caffeine. Salivary testosterone increased rapidly from rest (53%) and prior to treatments in all trials. Following caffeine treatment, testosterone increased by a further 12 +/- 14% (ES 0.50; +/- 0.56) relative to the placebo condition. In contrast, cortisol concentrations were not elevated until after the third exercise set; following the caffeine treatment cortisol was reduced by 21 +/- 31% (ES -0.30; +/- 0.34) relative to placebo. The acute ingestion of caffeine via chewing gum attenuated fatigue during repeated, high-intensity sprint exercise in competitive cyclists. Furthermore, the delayed fatigue was associated with substantially elevated testosterone concentrations and decreased cortisol in the caffeine trials.
Caffeine improves sprint, time trial and endurance exercise, increases fatty acid oxidation and spares muscle glycogen. Caffeine increases exercise performance by reducing sensations of fatigue.
Dodd SL, Herb RA, Powers SK.
Caffeine and exercise performance. An update.
Department of Exercise and Sport Sciences, University of Florida, Gainesville.
Three principal cellular mechanisms have been proposed to explain the ergogenic potential of caffeine during exercise: (a) increased myofilament affinity for calcium and/or increased release of calcium from the sarcoplasmic reticulum in skeletal muscle; (b) cellular actions caused by accumulation of cyclic-3′,5′-adenosine monophosphate (cAMP) in various tissues including skeletal muscle and adipocytes; and (c) cellular actions mediated by competitive inhibition of adenosine receptors in the central nervous system and somatic cells. The relative importance of each of the above mechanisms in explaining in vivo physiological effects of caffeine during exercise continues to be debated. However, growing evidence suggests that inhibition of adenosine receptors is one of the most important, if not the most important, mechanism to explain the physiological effects of caffeine at nontoxic plasma concentrations. Numerous animal studies using high caffeine doses have reported increased force development in isolated skeletal muscle in both in vitro and in situ preparations. In contrast, in vivo human studies have not consistently shown caffeine to enhance muscular performance during high intensity, short term exercise. Further, recent evidence supports previous work that shows caffeine does not improve performance during short term incremental exercise. Although controversy exists, the major part of published evidence evaluating performance supports the notion that caffeine is ergogenic during prolonged (> 30 min), moderate intensity (approximately 75 to 80% VO2max) exercise. The mechanism to explain these findings may be linked to a caffeine-mediated glycogen sparing effect secondary to an increased rate of lipolysis.
J Appl Physiol. 2008 Jul;105(1):7-13. Epub 2008 May 8.
High rates of muscle glycogen resynthesis after exhaustive exercise when carbohydrate is coingested with caffeine.
School of Medical Sciences, RMIT University, Bundoora 3083, Victoria, Australia.
We determined the effect of coingestion of caffeine (Caff) with carbohydrate (CHO) on rates of muscle glycogen resynthesis during recovery from exhaustive exercise in seven trained subjects who completed two experimental trials in a randomized, double-blind crossover design. The evening before an experiment subjects performed intermittent exhaustive cycling and then consumed a low-CHO meal. The next morning subjects rode until volitional fatigue. On completion of this ride subjects consumed either CHO [4 g/kg body mass (BM)] or the same amount of CHO + Caff (8 mg/kg BM) during 4 h of passive recovery. Muscle biopsies and blood samples were taken at regular intervals throughout recovery. Muscle glycogen levels were similar at exhaustion [ approximately 75 mmol/kg dry wt (dw)] and increased by a similar amount ( approximately 80%) after 1 h of recovery (133 +/- 37.8 vs. 149 +/- 48 mmol/kg dw for CHO and Caff, respectively). After 4 h of recovery Caff resulted in higher glycogen accumulation (313 +/- 69 vs. 234 +/- 50 mmol/kg dw, P < 0.001). Accordingly, the overall rate of resynthesis for the 4-h recovery period was 66% higher in Caff compared with CHO (57.7 +/- 18.5 vs. 38.0 +/- 7.7 mmol x kg dw(-1) x h(-1), P < 0.05). After 1 h of recovery plasma Caff levels had increased to 31 +/- 11 microM (P < 0.001) and at the end of the recovery reached 77 +/- 11 microM (P < 0.001) with Caff. Phosphorylation of CaMK(Thr286) was similar after exercise and after 1 h of recovery, but after 4 h CaMK(Thr286) phosphorylation was higher in Caff than CHO (P < 0.05). Phosphorylation of AMP-activated protein kinase (AMPK)(Thr172) and Akt(Ser473) was similar for both treatments at all time points. We provide the first evidence that in trained subjects coingestion of large amounts of Caff (8 mg/kg BM) with CHO has an additive effect on rates of postexercise muscle glycogen accumulation compared with consumption of CHO alone.
Int J Sports Physiol Perform. 2008 Jun;3(2):157-63.
The effects of caffeine ingestion on time trial cycling performance.
Applied Physiology Laboratory, University of Hull, UK.
The purpose of this work was to determine the effects of caffeine on high intensity time trial (TT) cycling performance in well-trained subjects.Six male cyclists with the following physical characteristics (mean +/- SD) age 30.7 +/- 12, height 179.3 +/- 7.5 cm, mass 70.0 +/- 7.5 kg, VO2max 65.0 +/- 6.3 mL.kg-1.min-1 undertook three 1-h TT performances, control (C), placebo (P) and caffeine (CAF), on a Velotron cycle ergometer conducted in a double-blind, random fashion. Subjects rested for 60 min and were then given CAF or P in a dose of 6 mg.kg-1 body mass and then commenced exercise after another 60 min of rest. Before ingestion, 60 min postingestion, and at the end of the TT, finger-prick blood samples were analyzed for lactate.The cyclists rode significantly further in the CAF trial (28.0 +/- 1.3 km) than they did in the C (26.3 +/- 1.5 km, P < .01) or P (26.4 +/- 1.5 km, P < .02) trials. No differences were seen in heart rate data throughout the TT (P > .05). Blood lactate levels were significantly higher at the end of the trials than either at rest or postingestion (P < .0001), but there were no differences between the three trial groups.On the basis of the data, we concluded that performance was improved with the use of a caffeine supplement.
Eur J Appl Physiol. 2010 May;109(2):287-95. Epub 2010 Jan 16.
Caffeine improves supramaximal cycling but not the rate of anaerobic energy release.
School of Physiotherapy and Exercise Science, Gold Coast campus, Griffith University, Southport, QLD 4215, Australia.
The purpose of this study was to determine if improved supramaximal exercise performance in trained cyclists following caffeine ingestion was associated with enhanced O(2) uptake (VO2 kinetics), increased anaerobic energy provision (accumulated O(2)-AO(2)-deficit), or a reduction in the accumulation of metabolites (for example, K(+)) associated with muscular fatigue. Six highly trained male cyclists (VO2peak 68 +/- 8 mL kg(-1) min(-1)) performed supramaximal (120% VO2peak) exercise bouts to exhaustion on an electronically braked cycle ergometer, following double-blind and randomized ingestion of caffeine/placebo (5 mg kg(-1)). Time to exhaustion (TE), VO2 kinetics, AO(2) deficit, blood lactate (La(-)), plasma potassium (K(+)), caffeine and paraxanthine concentrations were measured. Caffeine ingestion elicited significant increases in TE (14.8%, p < 0.01) and AO(2) deficit (6.5%, p < 0.05). In contrast, no changes were observed in AO(2) deficit at isotime, VO2 kinetics, blood [La(-)] at exhaustion or peak [K(+)] following caffeine ingestion. However, [K(+)] was significantly reduced (13.4%, p < 0.01) during warm-up cycling immediately prior to the onset of the supramaximal bout for the caffeine trials, compared with placebo. It appears that caffeine ingestion is beneficial to supramaximal cycling performance in highly trained men. The reduced plasma [K(+)] during submaximal warm-up cycling may prolong the time taken to reach critical [K(+)] at exhaustion, thus delaying fatigue. Considering caffeine ingestion did not change VO2 kinetics or isotime AO(2) deficit, increases in absolute AO(2) deficit may be a consequence of prolonged TE, rather than causal.