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The Science Behind Marathon

Marathon has been formulated to provide the energy and nutrient requirements for athletes training and racing for prolonged durations (>2hrs) and during stage racing.

To understand the science behind this formulation, we must first understand the requirements of prolonged endurance exercise.

Energy

Most athletes are under the mistaken impression that they should drink during exercise to avoid dehydration. However, humans are well adapted to withstand dehydration and the evidence for an impairment of exercise performance as a result of dehydration is not convincing. The primary requirement of an energy drink is to provide energy in the form of carbohydrates.

At the start of exercise, the body contains a limited store of carbohydrate energy. The liver contains approximately 100g of glycogen and muscle stores of glycogen add approximately 500g depending on body size and training status. During moderate and high intensity exercise, carbohydrates provide the majority of energy to working muscle. As exercise intensity increases above the lactate turnpoint, carbohydrates use increases exponentially.

Without additional carbohydrate supplementation, the available energy stored would last for only 60-90min during high intensity exercise.

Consuming carbohydrates in the form of a drink, gel or energy bar provides extra carbohydrate, delaying the depletion of liver and muscle glycogen stores and preventing the onset of fatigue.

The key factor in designing an energy supplement is therefore providing the most rapidly digestable and absorbable form of carbohydrate energy.

Getting the right mix is quite a complex exercise. The first factor is the rate at which the stomach delivers any ingested substance to the small intestine for absorption. At low carbohydrate concentrations (3g/100ml or 3%) gastric emptying and fluid absorption are the greatest but as the carbohydrate content increases, the gastric emptying rate gets progressively lower. Although the emptying rate is slower with higher carbohydrate concentrations, the increased carbohydrate concentration will deliver more carbohydrate to the small intestine. This reaches a peak at about 8-10% solutions (8-10g of carbohydrate per 100ml), which is the concentration of most commercial drinks and why Marathon should be mixed according to the recommended number of servings per 500ml of water.

Fluid absorption and gastric emptying peak at approximately 500ml of fluid per hour. Any more than that and the remainder will just pool in the gut, weighing you down and making you nauseous.

Things get even more complicated when we start to examine the different types of carbohydrates in the various commercial drinks and energy gels. Working muscles can only utilise glucose as a fuel. However, solutions that contain only glucose are both very sweet tasting and too thick (each glucose molecule increases the osmolality). This slows gastric emptying and makes them unpalatable in very hot and dry conditions. Solutions which contain maltodextrin (nearly tasteless chains of glucose molecules) are therefore easier to drink and get absorbed more rapidly.

More recently, research has focused on fructose.

Fructose is absorbed from the gastro-intestinal tract by a separate transporter molecule to the other carbohydrates such as glucose and galactose. Ingestion of a mix of glucose and fructose can therefore increase the rate of carbohydrate absorption in comparison to drinking sugars containing only glucose or a mix of other sugars. An energy drink that contains 2/3 maltodextrose and 1/3 fructose at a concentration of 8% will result in the greatest delivery of carbohydrate to working muscle. This improves exercise performance, delays fatigue and reduces GIT distress.

Protein

During prolonged endurance exercise (>90 minutes), increasing amounts of protein are used as an energy source. These proteins are primarily provided from the breakdown of muscle proteins. This is a concern to the athlete who has trained hard to build this muscle in the first place.

Early studies which investigated the effects of protein ingestion during exercise performance were largely conducted by adding protein to a standard carbohydrate mixture. Nearly all of these studies demonstrated an ergogenic (improved performance) benefit with added protein. Subsequent studies which have balanced the total caloric content of either a carbohydrate only or a mixed protein / carbohydrate drink have not been able to demonstrate a performance benefit conclusively. Therefore, the ergogenic effect of protein was assumed to be because of a generic effect of adding calories (fuel) as opposed to a unique benefit of protein.

However, the ingestion of protein both during and after exercise has been shown unequivocally to improve protein balance, reduce markers of muscle damage and improve the rate of recovery. These factors are important to the endurance athlete in considering the longer-term adaptations to training and not just the short-term performance effects. The addition of protein to a carbohydrate based supplement provides a more practical approach to optimizing the training and recovery of athletes, particularly those who train or compete in multiple sessions on the same or consecutive days.

Summary

Marathon is therefore formulated to provide the optimal carbohydrate constituents for endurance exercise as well as containing protein to reduce muscle damage, improve recovery and improve performance.

In addition, Marathon contains electrolytes, tuarine, phosphates and magnesium. The science behind all of the constituents is provided in the section below:

STATEMENT

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.

SCIENCE

Scand J Med Sci Sports. 2008 Nov 3. [Epub ahead of print]

Multiple transportable carbohydrates enhance gastric emptying and fluid delivery.

Jeukendrup AE, Moseley L.

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.

Rowlands DS, Thorburn MS, Thorp RM, Broadbent S, Shi X.

Institute of Food, Nutrition, and Human Health, Massey Univ., Wellington, New Zealand. d.s.rowlands@massey.ac.nz

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.

Currell K, Jeukendrup AE.

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.

Jeukendrup AE, Moseley L, Mainwaring GI, Samuels S, Perry S, Mann CH.

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.

STATEMENT

Optimal carbohydrate / protein ratio (5 / 1). Numerous studies have proven the efficacy of mixed protein and carbohydrate ingestion in comparison to carbohydrate alone. Mixed carbohydrate / protein drinks reduce exercise related muscle damage and catabolism, improving subsequent exercise performance.

SCIENCE

Med Sci Sports Exerc. 2004 Jul;36(7):1233-8.

Effects of a carbohydrate-protein beverage on cycling endurance and muscle damage.

Saunders MJ, Kane MD, Todd MK.

School of Kinesiology and Recreation Studies, James Madison University, Harrisonburg, VA 22807, USA. saundemj@jmu.edu

Med Sci Sports Exerc. 2005 Jan;37(1):166; author reply 167.

INTRODUCTION: The purpose of this study was to determine whether endurance cycling performance and postexercise muscle damage were altered when consuming a carbohydrate and protein beverage (CHO+P; 7.3% and 1.8% concentrations) versus a carbohydrate-only (CHO; 7.3%) beverage. METHODS: Fifteen male cyclists (mean (.-)VO(2peak) = 52.6 +/- 10.3 mL x kg x min) rode a cycle ergometer at 75% (.-)VO(2peak) to volitional exhaustion, followed 12 – 15 h later by a second ride to exhaustion at 85% (.-)VO(2peak). Subjects consumed 1.8 mL x kg BW of randomly assigned CHO or CHO+P beverage every 15 min of exercise, and 10 mL x kg BW immediately after exercise. Beverages were matched for carbohydrate content, resulting in 20% lower total caloric content per administration of CHO beverage. Subjects were blinded to treatment beverage and repeated the same protocol seven to 14 d later with the other beverage. RESULTS: In the first ride (75% (.-)VO(2peak)), subjects rode 29% longer (P < 0.05) when consuming the CHO+P beverage (106.3 +/- 45.2 min) than the CHO beverage (82.3 +/- 32.6 min). In the second ride (85% (.-)VO(2peak)), subjects performed 40% longer when consuming the CHO+P beverage (43.6 +/- 12.5 min) than when consuming the CHO beverage (31.2 +/- 8.7 min). Peak postexercise plasma CPK levels, indicative of muscle damage, were 83% lower after the CHO+P trial (216.3 +/- 122.0 U x L) than the CHO trial (1318.1 +/- 1935.6 U x L). There were no significant differences in exercising levels of (.-)VO(2), ventilation, heart rate, RPE, blood glucose, or blood lactate between treatments in either trial. CONCLUSION: A carbohydrate beverage with additional protein calories produced significant improvements in time to fatigue and reductions in muscle damage in endurance athletes. Further research is necessary to determine whether these effects were the result of higher total caloric content of the CHO+P beverage or due to specific protein-mediated mechanisms.

Int J Sport Nutr Exerc Metab. 2008 Aug;18(4):363-78.

Influence of carbohydrate-protein beverage on cycling endurance and indices of muscle disruption.

Valentine RJ, Saunders MJ, Todd MK, St Laurent TG.

Department of Kinesiology, James Madison University, Harrisonburg, VA 22807, USA.

Carbohydrate-protein (CHO+Pro) beverages reportedly improve endurance and indices of muscle disruption, but it is unclear whether these effects are related to total energy intake or specific effects of protein. Purpose: The authors examined effects of CHO+Pro on time to exhaustion and markers of muscle disruption compared with placebo (PLA) and carbohydrate beverages matched for carbohydrate (CHO) and total calories (CHO+CHO). Methods: Eleven male cyclists completed 4 rides to exhaustion at 75% VO2peak. Participants consumed 250 ml of PLA, CHO (7.75%), CHO+CHO (9.69%), or CHO+Pro (7.75%/1.94%) every 15 min until fatigue, in a double-blind design. Results: Time to exhaustion was significantly longer (p<.05) in CHO+Pro (126.2+/-25.4 min) and CHO+CHO (121.3+/-36.8) than PLA (107.1+/-30.3). CHO (117.5+/-24.2) and PLA were not significantly different. Similarly, CHO+Pro was not significantly different from CHO and CHO+CHO. Postexercise plasma creatine kinase was lower after CHO+Pro (197.2+/-149.2 IU/L) than PLA (407.4+/-391.3), CHO (373.2+/-416.6), and CHO+CHO (412.3+/-410.2). Postexercise serum myoglobin was lower in CHO+Pro (47.0+/-27.4 ng/mL) than all other treatments (168.8+/-217.3, 82.6+/-71.3, and 72.0+/-75.8). Postexercise leg extensions at 70% 1RM were significantly greater 24 hr after CHO+Pro (11.3+/-4.1) than PLA (8.8+/-3.7), CHO (9.7+/-4.3), and CHO+CHO (9.5+/-3.6). Conclusion: These findings suggest that at least some of the reported improvements in endurance with CHO+Pro beverages might be related to caloric differences between treatments. Postexercise improvements in markers of muscle disruption with CHO+Pro ingestion appear to be independent of carbohydrate and caloric content and were elicited with beverages consumed only during exercise.

Am J Physiol Endocrinol Metab. 2004 Oct;287(4):E712-20. Epub 2004 May 27.

Combined ingestion of protein and carbohydrate improves protein balance during ultra-endurance exercise.

Koopman R, Pannemans DL, Jeukendrup AE, Gijsen AP, Senden JM, Halliday D, Saris WH, van Loon LJ, Wagenmakers AJ.

Department of Human Biology, Maastricht University, PO Box 616, 6200 MD, The Netherlands. R.Koopman@HB.unimaas.nl

The aims of this study were to compare different tracer methods to assess whole body protein turnover during 6 h of prolonged endurance exercise when carbohydrate was ingested throughout the exercise period and to investigate whether addition of protein can improve protein balance. Eight endurance-trained athletes were studied on two different occasions at rest (4 h), during 6 h of exercise at 50% of maximal O2 uptake (in sequential order: 2.5 h of cycling, 1 h of running, and 2.5 h of cycling), and during subsequent recovery (4 h). Subjects ingested carbohydrate (CHO trial; 0.7 g CHO.kg(-1.)h(-1)) or carbohydrate/protein beverages (CHO + PRO trial; 0.7 g CHO.kg(-1).h(-1) and 0.25 g PRO.kg(-1).h(-1)) at 30-min intervals during the entire study. Whole body protein metabolism was determined by infusion of L-[1-13C]leucine, L-[2H5]phenylalanine, and [15N2]urea tracers with sampling of blood and expired breath. Leucine oxidation increased from rest to exercise [27 +/- 2.5 vs. 74 +/- 8.8 (CHO) and 85 +/- 9.5 vs. 200 +/- 16.3 mg protein.kg(-1).h(-1) (CHO + PRO), P < 0.05], whereas phenylalanine oxidation and urea production did not increase with exercise. Whole body protein balance during exercise with carbohydrate ingestion was negative (-74 +/- 8.8, -17 +/- 1.1, and -72 +/- 5.7 mg protein.kg(-1).h(-1)) when L-[1-13C]leucine, L-[2H5]phenylalanine, and [15N2]urea, respectively, were used as tracers. Addition of protein to the carbohydrate drinks resulted in a positive or less-negative protein balance (-32 +/- 16.3, 165 +/- 4.6, and 151 +/- 13.4 mg protein.kg(-1).h(-1)) when L-[1-13C]leucine, L-[2H5]phenylalanine, and [15N2]urea, respectively, were used as tracers. We conclude that, even during 6 h of exhaustive exercise in trained athletes using carbohydrate supplements, net protein oxidation does not increase compared with the resting state and/or postexercise recovery. Combined ingestion of protein and carbohydrate improves net protein balance at rest as well as during exercise and postexercise recovery.

J Strength Cond Res. 2007 Aug;21(3):678-84.

Consumption of an oral carbohydrate-protein gel improves cycling endurance and prevents postexercise muscle damage.

Saunders MJ, Luden ND, Herrick JE.

Human Performance Laboratory, Department of Kinesiology, James Madison University, Harrisonburg, Virginia 22807, USA. saundemj@jmu.edu

Investigators have reported improved endurance performance and attenuated post-exercise muscle damage with carbohydrate-protein beverages (CHO+P) versus carbohydrate-only beverages (CHO). However, these benefits have been demonstrated only when CHO+P was administered in beverage-form, and exclusively in male subjects. Thus, the purposes of this study were to determine if an oral CHO+P gel improved endurance performance and post-exercise muscle damage compared to a CHO gel, and determine if responses were similar between genders. Thirteen cyclists (8 men, 5 women; VO(2)peak = 57.9 +/- 7.0 ml x kg(-1) x min(-1)) completed two timed cycle-trials to volitional exhaustion at 75% of VO(2)peak. At 15-minute intervals throughout these rides, subjects received CHO or CHO+P gels, which were matched for carbohydrate content (CHO = 0.15 g CHO x kg BW(-1); CHO+P = 0.15 g CHO + 0.038 g protein x kg BW(-1)). Trials were performed using a randomly counterbalanced, double-blind design. Subjects rode 13% longer (p < 0.05) when utilizing the CHO+P gel (116.6 +/- 28.5 minutes) versus the CHO gel (102.8 +/- 25.0 minutes). In addition, men (101.8 +/- 24.6; 114.8 +/- 26.2) and women (104.4 +/- 28.6; 119.6 +/- 34.9) responded similarly to the CHO and CHO+P trials, with no significant treatment-by-gender effect. Postexercise creatine kinease (CK) was not significantly different between treatments. However, CK increased significantly following exercise in the CHO trial (183 +/- 116; 267 +/- 214 U x L(-1)), but not the CHO+P trial (180 +/- 133; 222 +/- 141 U x L(-1)). Therefore, to prolong endurance performance and prevent increases in muscle damage, it is recommended that male and female cyclists consume CHO+P gels rather than CHO gels during and immediately following exercise.

STATEMENT

Taurine supplementation improves exercise performance and reduces exercise induced muscle damage.

SCIENCE

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.

Zhang M, Izumi I, Kagamimori S, Sokejima S, Yamagami T, Liu Z, Qi B.

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.

Dawson R Jr, Biasetti M, Messina S, Dominy J.

Department of Pharmacodynamics, College of Pharmacy, JHMHC Box 100487, University of Florida, Gainesville, FL 32610, U.S.A. dawson@cop.ufl.edu

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.

Imagawa TF, Hirano I, Utsuki K, Horie M, Naka A, Matsumoto K, Imagawa S.

Doctoral Program of Sports Medicine, University of Tsukuba, GSCHS, 1-1-1 D507, Tennoudai, Ibaraki, Tsukuba 305-8577, Japan. ima3sytag8sr@md.tsukuba.ac.jp

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.

STATEMENT

Phosphate supplementation and loading enhance myocardial function, improve exercise performance and increase exercise oxidative capacity.

SCIENCE

Int J Sport Nutr. 1992 Mar;2(1):20-47.

Effects of phosphate loading on metabolic and myocardial responses to maximal and endurance exercise.

Kreider RB, Miller GW, Schenck D, Cortes CW, Miriel V, Somma CT, Rowland P, Turner C, Hill D.

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.

Folland JP, Stern R, Brickley G.

School of Sport and Exercise Sciences, Loughborough University, UK. j.p.folland@lboro.ac.uk

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.

STATEMENT

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.

SCIENCE

Crit Rev Food Sci Nutr. 2002;42(6):533-63.

Magnesium and exercise.

Bohl CH, Volpe SL.

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.

Nielsen FH, Lukaski HC.

U.S. Department ofAgriculture, Agricultural Research Service, Grand Forks Human Nutrition Research Center, Grand Forks, ND 58202-9034, USA. fnielsen@gfhnrc.ars.usda.gov

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).

STATEMENT

Balanced electrolyte formula to optimise performance

SCIENCE

Int J Sports Med. 1994 Oct;15(7):392-8.

Impaired high-intensity cycling performance time at low levels of dehydration.

Walsh RM, Noakes TD, Hawley JA, Dennis SC.

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)

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