Effects of Intermittent Energy Restriction Alone and in Combination with Sprint Interval Training on Body Composition and Cardiometabolic Biomarkers in Individuals with Overweight and Obesity.

The popularity of intermittent fasting (IF) and high intensity (sprint) interval training (SIT) has increased in recent years amongst the general public due to their purported health benefits and feasibility of incorporation into daily life. The number of scientific studies investigating these strategies has also increased, however, very few have examined the combined effects, especially on body composition and cardiometabolic biomarkers, which is the primary aim of this investigation. A total of thirty-four male and female participants (age: 35.4 ± 8.4 y, body mass index (BMI): 31.3 ± 3.5 kg/m2, aerobic capacity (VO2peak) 27.7 ± 7.0 mL·kg−1·min−1) were randomized into one of three 16-week interventions: (1) 5:2 IF (2 non-consecutive days of fasting per week, 5 days on ad libitum eating), (2) supervised SIT (3 bouts per week of 20s cycling at 150% VO2peak followed by 40 s of active rest, total 10 min duration), and (3) a combination of both interventions. Body composition, haemodynamic and VO2peak were measured at 0, 8 and 16 weeks. Blood samples were also taken and analysed for lipid profiles and markers of glucose regulation. Both IF and IF/SIT significantly decreased body weight, fat mass and visceral fat compared to SIT only (p < 0.05), with no significant differences between diet and diet + exercise combined. The effects of diet and/or exercise on cardiometabolic biomarkers were mixed. Only exercise alone or with IF significantly increased cardiorespiratory fitness. The results suggest that energy restriction was the main driver of body composition enhancement, with little effect from the low volume SIT. Conversely, to achieve benefits in cardiorespiratory fitness, exercise is required.

Heat Acclimation with or without Normobaric Hypoxia Exposure Leads to Similar Improvements in Endurance Performance in the Heat.

BACKGROUND: Combining the key adaptation of plasma volume (PV) expansion with synergistic physiological effects of other acclimation interventions to maximise endurance performance in the heat has potential. The current study investigated the effects of heat acclimation alone (H), combined with normobaric hypoxia exposure (H+NH), on endurance athletic performance. METHODS: Well-trained participants completed a heat-stress trial (30 °C, 80% relative humidity (RH), 20.8% fraction of inspired oxygen (FiO2)) of a 75 min steady-state cycling (fixed workload) and a subsequent 15 min cycling time trial for distance before and after intervention. Participants completed 12 consecutive indoor training days with either heat acclimation (H; 60 min·day-1, 30 °C, 80% RH; 20.8% FiO2) or heat acclimation and overnight hypoxic environment (H+NH; ~12 h, 60% RH; 16% FiO2 simulating altitude of ~2500 m). Control (CON) group trained outdoors with average maximum daily temperature of 16.5 °C and 60% RH. RESULTS: Both H and H+NH significantly improved time trial cycling distance by ~5.5% compared to CON, with no difference between environmental exposures. PV increased (+3.8%) and decreased (-4.1%) following H and H+NH, respectively, whereas haemoglobin concentration decreased (-2%) and increased (+3%) in H and H+NH, respectively. CONCLUSION: Our results show that despite contrasting physiological adaptations to different environmental acclimation protocols, heat acclimation with or without hypoxic exposure demonstrated similar improvements in short-duration exercise performance in a hot environment.

High intensity exercise downregulates FTO mRNA expression during the early stages of recovery in young males and females.

BACKGROUND: Physical exercise and activity status may modify the effect of the fat mass- and obesity-associated (FTO) genotype on body weight and obesity risk. To understand the interaction between FTO's effect and physical activity, the present study investigated the effects of high and low intensity exercise on FTO mRNA and protein expression, and potential modifiers of exercise-induced changes in FTO in healthy-weighted individuals. METHODS: Twenty-eight untrained males and females (25.4 ± 1.1 years; 73.1 ± 2.0 kg; 178.8 ± 1.4 cm; 39.0 ± 1.2 ml.kg.min- 1 VO2peak) were genotyped for the FTO rs9939609 (T > A) polymorphism and performed isocaloric (400 kcal) cycle ergometer exercise on two separate occasions at different intensities: 80% (High Intensity (HI)) and 40% (Low Intensity (LO)) VO2peak. Skeletal muscle biopsies (vastus lateralis) and blood samples were taken pre-exercise and following 10 and 90 mins passive recovery. RESULTS: FTO mRNA expression was significantly decreased after HI intensity exercise (p = 0.003). No differences in basal and post-exercise FTO protein expression were evident between FTO genotypes. Phosphorylated adenosine monophosphate-activated protein kinase (AMPK) and Akt substrate of 160 kDa (AS160) were significantly increased following HI intensity exercise (p < 0.05). Multivariate models of metabolomic data (orthogonal two partial least squares discriminant analysis (O2PLS-DA)) were unable to detect any significant metabolic differences between genotypes with either exercise trial (p > 0.05). However, skeletal muscle glucose accumulation at 10 mins following HI (p = 0.021) and LO (p = 0.033) intensity exercise was greater in AA genotypes compared to TT genotypes. CONCLUSION: Our novel data provides preliminary evidence regarding the effects of exercise on FTO expression in skeletal muscle. Specifically, high intensity exercise downregulates expression of FTO mRNA and suggests that in addition to nutritional regulation, FTO could also be regulated by exercise. TRIAL REGISTRATION: ACTRN12612001230842. Registered 21 November 2012 - Prospectively registered, https://www.anzctr.org.au/.

Intermittent Fasting and High-Intensity Exercise Elicit Sexual-Dimorphic and Tissue-Specific Adaptations in Diet-Induced Obese Mice.

: The molecular adaptations that underpin body composition changes and health benefits of intermittent fasting (IF) and high-intensity interval training (HIIT) are unclear. The present study investigated these adaptations within the hypothalamus, white adipose and skeletal muscle tissue following 12 weeks of IF and/or HIIT in diet-induced obese mice. Mice (C57BL/6, 8-week-old, males/females) were fed high-fat (59%) and sugar (30%) water (HF/S) for 12 weeks followed by an additional 12 weeks of HF/S plus either IF, HIIT, combination (IF+HIIT) or HF/S only control (CON). Tissues were harvested at 12 and 24 weeks and analysed for various molecular markers. Hypothalamic NPY expression was significantly lower following IF+HIIT compared to CON in females. In adipose tissue, leptin expression was significantly lower following IF and IF+HIIT compared to CON in males and females. Males demonstrated increased markers of fat oxidation (HADH, FABP4) following IF+HIIT, whereas females demonstrated reduced markers of adipocyte differentiation/storage (CIDEC and FOXO1) following IF and/or IF+HIIT. In muscle, SIRT1, UCP3, PGC1α, and AS160 expression was significantly lower following IF compared to CON in males and/or females. This investigation suggests that males and females undertaking IF and HIIT may prevent weight gain via different mechanisms within the same tissue.

Adenylosuccinic acid therapy ameliorates murine Duchenne Muscular Dystrophy.

Arising from the ablation of the cytoskeletal protein dystrophin, Duchenne Muscular Dystrophy (DMD) is a debilitating and fatal skeletal muscle wasting disease underpinned by metabolic insufficiency. The inability to facilitate adequate energy production may impede calcium (Ca2+) buffering within, and the regenerative capacity of, dystrophic muscle. Therefore, increasing the metabogenic potential could represent an effective treatment avenue. The aim of our study was to determine the efficacy of adenylosuccinic acid (ASA), a purine nucleotide cycle metabolite, to stimulate metabolism and buffer skeletal muscle damage in the mdx mouse model of DMD. Dystrophin-positive control (C57BL/10) and dystrophin-deficient mdx mice were treated with ASA (3000 µg.mL-1) in drinking water. Following the 8-week treatment period, metabolism, mitochondrial density, viability and superoxide (O2-) production, as well as skeletal muscle histopathology, were assessed. ASA treatment significantly improved the histopathological features of murine DMD by reducing damage area, the number of centronucleated fibres, lipid accumulation, connective tissue infiltration and Ca2+ content of mdx tibialis anterior. These effects were independent of upregulated utrophin expression in the tibialis anterior. ASA treatment also increased mitochondrial viability in mdx flexor digitorum brevis fibres and concomitantly reduced O2- production, an effect that was also observed in cultured immortalised human DMD myoblasts. Our data indicates that ASA has a protective effect on mdx skeletal muscles.

Similarities in Metabolic Flexibility and Hunger Hormone Ghrelin Exist between FTO Gene Variants in Response to an Acute Dietary Challenge.

The rs9939609 polymorphism of the fat mass and obesity-associated (FTO) gene has been associated with obesity, and studies have also shown that environmental/lifestyle interaction such as dietary intake might mediate this effect. The current study investigates the postprandial hormonal regulators of hunger and indirect markers of substrate utilisation and metabolic flexibility following a dietary challenge to determine if suppression of circulating ghrelin levels and/or reduced metabolic flexibility exist between FTO genotypes. One hundred and forty seven healthy, sedentary males and females (29.0 ± 0.7 yrs; 70.2 ± 1.1 kg; 169.1 ± 0.8 cm; 24.5 ± 0.3 kg/m2) complete a single experimental session. Anthropometric measures, circulating levels of active ghrelin, insulin and glucose, and substrate oxidation via indirect calorimetry, are measured pre-prandial and/or post-prandial. The FTO rs9939609 variant is genotyped using a real-time polymerase chain reaction. Metabolic flexibility (∆RER) is similar between FTO genotypes of the rs9939609 (T > A) polymorphism (p > 0.05). No differences in pre-prandial and/or postprandial substrate oxidation, plasma glucose, serum insulin or ghrelin are observed between genotypes (p > 0.05). These observations are independent of body mass index and gender. Altered postprandial responses in hunger hormones and metabolic flexibility may not be a mechanism by which FTO is associated with higher BMI and obesity in healthy, normal-weighted individuals.

Myoprotective Potential of Creatine Is Greater than Whey Protein after Chemically-Induced Damage in Rat Skeletal Muscle.

The myoprotective effects of creatine monohydrate (CR) and whey protein (WP) are equivocal, with the use of proxy measures of muscle damage making interpretation of their effectiveness limited. The purpose of the study was to determine the effects of CR and WP supplementation on muscle damage and recovery following controlled, chemically-induced muscle damage. Degeneration of the extensor digitorum longus (EDL) muscle was induced by bupivacaine in rats supplemented with either CR, WP, or standard rat chow (CON). At day 7 and 14 post-myotoxic injury, injured EDL muscles were surgically removed and tested for isometric contractile properties, followed by the contralateral, non-injured EDL muscle. At the completion of testing, muscles were snap-frozen in liquid nitrogen and stored for later analysis. Data were analyzed using analysis of variance. Creatine-supplemented muscles displayed a greater proportion of non-damaged (intact) fibers (p = 0.002) and larger cross-sectional areas of regenerating and non-damaged fibers (p = 0.024) compared to CON muscles at day 7 post-injury. At day 14 post-injury, CR-supplemented muscles generated higher absolute forces concomitant with greater contractile protein levels compared to CON (p = 0.001, p = 0.008) and WP-supplemented muscles (p = 0.003, p = 0.006). Creatine supplementation appears to offer an element of myoprotection which was not observed following whey protein supplementation.

Intermittent Fasting with or without Exercise Prevents Weight Gain and Improves Lipids in Diet-Induced Obese Mice.

Intermittent fasting (IF) and high intensity interval training (HIIT) are effective lifestyle interventions for improving body composition and overall health. However, the long-term effects of IF and potential synergistic effects of combining IF with exercise are unclear. The purpose of the study was to investigate the long-term effects of IF, with or without HIIT, on body composition and markers of metabolic health in diet-induced obese mice. In a randosmised, controlled design, 8-week-old C57BL/6 mice (males (n = 39) and females (n = 49)) were fed a high fat (HF) and sugar (S) water diet (30% (w/v)) for 24-weeks but were separated into five groups at 12-weeks: (1) 'obese' baseline control (OBC); (2) no intervention (CON); (3) intermittent fasting (IF); (4) high intensity intermittent exercise (HIIT) and (5) combination of dietary and exercise intervention (IF + HIIT). Body composition, strength and blood variables were measured at 0, 10 and/or 12-weeks. Intermittent fasting with or without HIIT resulted in significantly less weight gain, fat mass accumulation and reduced serum low density lipoproteins (LDL) levels compared to HIIT and CON male mice (p < 0.05). The results suggest that IF, with or without HIIT, can be an effective strategy for weight gain prevention despite concurrently consuming a high fat and sugar diet.

Metabogenic and Nutriceutical Approaches to Address Energy Dysregulation and Skeletal Muscle Wasting in Duchenne Muscular Dystrophy.

Duchenne Muscular Dystrophy (DMD) is a fatal genetic muscle wasting disease with no current cure. A prominent, yet poorly treated feature of dystrophic muscle is the dysregulation of energy homeostasis which may be associated with intrinsic defects in key energy systems and promote muscle wasting. As such, supplementative nutriceuticals that target and augment the bioenergetical expansion of the metabolic pathways involved in cellular energy production have been widely investigated for their therapeutic efficacy in the treatment of DMD. We describe the metabolic nuances of dystrophin-deficient skeletal muscle and review the potential of various metabogenic and nutriceutical compounds to ameliorate the pathological and clinical progression of the disease.

The effect of ß-alanine and NaHCO3 co-ingestion on buffering capacity and exercise performance with high-intensity exercise in healthy males.

INTRODUCTION: ß-alanine (BAl) and NaHCO3 (SB) ingestion may provide performance benefits by enhancing concentrations of their respective physiochemical buffer counterparts, muscle carnosine and blood bicarbonate, counteracting acidosis during intense exercise. This study examined the effect of BAl and SB co-supplementation as an ergogenic strategy during high-intensity exercise. METHODS: Eight healthy males ingested either BAl (4.8 g day(-1) for 4 weeks, increased to 6.4 g day(-1) for 2 weeks) or placebo (Pl) (CaCO3) for 6 weeks, in a crossover design (6-week washout between supplements). After each chronic supplementation period participants performed two trials, each consisting of two intense exercise tests performed over consecutive days. Trials were separated by 1 week and consisted of a repeated sprint ability (RSA) test and cycling capacity test at 110 % Wmax (CCT110 %). Placebo (Pl) or SB (300 mg kgbw(-1)) was ingested prior to exercise in a crossover design to creating four supplement conditions (BAl-Pl, BAl-SB, Pl-Pl, Pl-SB). RESULTS: Carnosine increased in the gastrocnemius (n = 5) (p = 0.03) and soleus (n = 5) (p = 0.02) following BAl supplementation, and Pl-SB and BAl-SB ingestion elevated blood HCO3 (-) concentrations (p < 0.01). Although buffering capacity was elevated following both BAl and SB ingestion, performance improvement was only observed with BAl-Pl and BAl-SB increasing time to exhaustion of the CCT110 % test 14 and 16 %, respectively, compared to Pl-Pl (p < 0.01). CONCLUSION: Supplementation of BAl and SB elevated buffering potential by increasing muscle carnosine and blood bicarbonate levels, respectively. BAl ingestion improved performance during the CCT110 %, with no aggregating effect of SB supplementation (p > 0.05). Performance was not different between treatments during the RSA test.

A pilot study investigating the effect of Caralluma fimbriata extract on the risk factors of metabolic syndrome in overweight and obese subjects: a randomised controlled clinical trial.

OBJECTIVES: Central obesity is a key component of metabolic syndrome and it is often associated with other risk factors such as dyslipidemia, elevated plasma glucose levels and elevated blood pressure (BP). In this pilot study, the effect of Caralluma fimbriata (an edible succulent) extract in combination with controlled dietary intake and physical activity on these risk factors was assessed in overweight and obese Australian subjects. DESIGN: This was a randomised, double blind placebo controlled clinical trial. Forty-three adults aged 29-59 years were recruited. The eligibility criteria included a Body Mass Index (BMI) >25 kg/m(2), or a waist circumference >94 cm (male), >80 cm (female). Thirty-three participants completed the 12-week study at Victoria University Nutritional Therapy Clinic. Participants were randomly assigned into two groups. C. fimbriata extract and placebo were orally administered as 500 mg capsules twice daily (1 g/day) and dietary intake and exercise were monitored weekly. RESULTS: The results of thirty-three participants (experimental group, n = 17; placebo group n = 16) were analysed. The primary outcome measure was the decline in waist circumference. By week 9, the experimental group had lost 5.7 cm, compared to only 2.8 cm loss in the placebo group (Difference: -2.890; 95% CI; -5.802 to 0.023). Post intervention, the experimental group had lost 6.5 cm compared to 2.6 cm loss in the placebo group (Difference: -3.847; 95% CI; -7.466 to 0.228). Waist to hip ratio (WHR) also improved significantly after 12 weeks intervention in the experimental group, with a total reduction of 0.03 being recorded compared to 0.01 increase in the placebo group (Difference: -0.033; 95% CI; -0.064 to -0.002). There was also a significant decline in the palatability (visual appeal, smell, taste) of the test meal and sodium intake in the experimental group at week 12 (p < 0.05). In addition a significant reduction in body weight, BMI, hip circumference, systolic BP, HR, triglyceride levels, total fat and saturated fat intake within both groups was observed following the intervention period (p < 0.05). CONCLUSION: Supplementation with C. fimbriata extract whilst controlling overall dietary intake and physical activity may potentially play a role in curbing central obesity, the key component of metabolic syndrome. Controlling dietary intake and exercise improved body weight and favourably influenced the metabolic risk profile.

Co-ingestion of carbohydrate and whey protein isolates enhance PGC-1α mRNA expression: a randomised, single blind, cross over study.

BACKGROUND: Whey protein isolates (WPI) supplementation is known to improve resistance training adaptations. However, limited information is available on the effects of WPI plus carbohydrate (CHO) supplementation on endurance training adaptations. METHOD: Six endurance trained male cyclists and triathletes (age 29 ± 4 years, weight 74 ± 2 kg, VO2 max 63 ± 3 ml oxygen. kg-1. Min-1, height 183 ± 5 cm; mean ± SEM) were randomly assigned to one of two dietary interventions in a single blind cross over design; CHO or CHO + WPI. Each dietary intervention was followed for 16 days which included the last 2 days having increased CHO content, representing a CHO loading phase. The dietary interventions were iso-caloric and carbohydrate content matched. On completion of the dietary intervention, participants performed an exercise bout, consisting of cycling for 60 min at 70% VO2 max, followed by time trial to exhaustion at 90% VO2 max and recovered in the laboratory for 6 hours. Blood samples and muscle biopsies were taken at various time points at rest and through the exercise trial and recovery. RESULTS: Compared to CHO, CHO + WPI increased plasma insulin during recovery at 180 mins (P < 0.05) and peroxisome proliferator-activated receptor gamma coactivator-1 alpha (PGC-1α) mRNA expression at the end of 6 hours of recovery (P < 0.05). Muscle glycogen did not differ between the two trials. CONCLUSION: This study showed co-ingestion of CHO + WPI may have beneficial effects on recovery and adaptations to endurance exercise via, increased insulin response and up regulation of PGC-1α mRNA expression.

Can carbohydrate mouth rinse improve performance during exercise? A systematic review.

The purpose of this review was to identify studies that have investigated the effect of carbohydrate (CHO) mouth rinse on exercise performance, and to quantify the overall mean difference of this type of manipulation across the studies. The main mechanisms involving the potential benefit of CHO mouth rinse on performance was also explored. A systematic review was conducted in the following electronic databases: PubMed, SciELO, Science Direct, MEDLINE, and the Cochrane Library (Cochrane Central Register of Controlled Trials), without limit of searches. Eleven studies were classified as appropriate and their results were summarized and compared. In nine of them, CHO mouth rinse increased the performance (range from 1.50% to 11.59%) during moderate- to high-intensity exercise (~75% Wmax or 65% VO2max, ~1 h duration). A statistical analysis to quantify the individual and overall mean differences was performed in seven of the 11 eligible studies that reported power output (watts, W) as the main performance outcome. The overall mean difference was calculated using a random-effect model that accounts for true variation in effects occurring in each study, as well as random error within a single study. The overall effect of CHO mouth rinse on performance was significant (mean difference=5.05 W, 95% CI 0.90 to 9.2 W, z=2.39, p=0.02) but there was a large heterogeneity between the studies (I2=52%). An activation of the oral receptors and consequently brain areas involved with reward (insula/operculum frontal, orbitofrontal cortex, and striatum) is suggested as a possible physiological mechanism responsible for the improved performance with CHO mouth rinse. However, this positive effect seems to be accentuated when muscle and liver glycogen stores are reduced, possibly due to a greater sensitivity of the oral receptors, and require further investigation. Differences in duration of fasting before the trial, duration of mouth rinse, type of activity, exercise protocols, and sample size may account for the large variability between the studies.

Whey protein isolate attenuates strength decline after eccentrically-induced muscle damage in healthy individuals.

BACKGROUND: We examined the effects of short-term consumption of whey protein isolate on muscle proteins and force recovery after eccentrically-induced muscle damage in healthy individuals. METHODS: Seventeen untrained male participants (23 ± 5 yr, 180 ± 6 cm, 80 ± 11 kg) were randomly separated into two supplement groups: i) whey protein isolate (WPH; n = 9); or ii) carbohydrate (CHO; n = 8). Participants consumed 1.5 g/kg.bw/day supplement (~30 g consumed immediately, and then once with breakfast, lunch, in the afternoon and after the evening meal) for a period of 14 days following a unilateral eccentric contraction-based resistance exercise session, consisting of 4 sets of 10 repetitions at 120% of maximum voluntary contraction on the leg press, leg extension and leg flexion exercise machine. Plasma creatine kinase and lactate dehydrogenase (LDH) levels were assessed as blood markers of muscle damage. Muscle strength was examined by voluntary isokinetic knee extension using a Cybex dynamometer. Data were analyzed using repeated measures ANOVA with an alpha of 0.05. RESULTS: Isometric knee extension strength was significantly higher following WPH supplementation 3 (P < 0.05) and 7 (P < 0.01) days into recovery from exercise-induced muscle damage compared to CHO supplementation. In addition, strong tendencies for higher isokinetic forces (extension and flexion) were observed during the recovery period following WPH supplementation, with knee extension strength being significantly greater (P < 0.05) after 7 days recovery. Plasma LDH levels tended to be lower (P = 0.06) in the WPH supplemented group during recovery. CONCLUSIONS: The major finding of this investigation was that whey protein isolate supplementation attenuated the impairment in isometric and isokinetic muscle forces during recovery from exercise-induced muscle injury.

N-Acetylcysteine infusion does not affect glucose disposal during prolonged moderate-intensity exercise in humans.

There is evidence that reactive oxygen species (ROS) signalling is required for normal increases in glucose uptake during contraction of isolated mouse skeletal muscle, and that AMP-activated protein kinase (AMPK) is involved. The aim of this study was to determine whether ROS signalling is involved in the regulation of glucose disposal and AMPK activation during moderate-intensity exercise in humans. Nine healthy males completed 80 min of cycle ergometry at 62 +/- 1% of peak oxygen consumption ( V(O(2)peak).A 6,6-(2)H-glucose tracer was infused at rest and during exercise, and in a double-blind randomised cross-over design, N-acetylcysteine (NAC) or saline (CON) was co-infused. NAC was infused at 125 mg kg(1) h(1) for 15 min and then at 25 mg kg(1) h(1) for 20 min before and throughout exercise. NAC infusion elevated plasma NAC and cysteine, and muscle NAC and cysteine concentrations during exercise. Although neither NAC infusion nor exercise significantly affected muscle reduced or oxidised glutathione (GSH or GSSG) concentration (P > 0.05), S-glutathionylation (an indicator of oxidative stress) of a protein band of approximately 270 kDa was increased approximately 3-fold with contraction and this increase was prevented by NAC infusion. Despite this, exercised-induced increases in tracer determined glucose disposal, plasma lactate, plasma non-esterified fatty acids (NEFAs), and decreases in plasma insulin were not affected by NAC infusion. In addition, skeletal muscle AMPKalpha and acetyl-CoA carboxylase-beta (ACCbeta) phosphorylation increased during exercise by approximately 3- and approximately 6-fold (P < 0.05), respectively, and this was not affected by NAC infusion. Unlike findings in mouse muscle ex vivo, NAC does not attenuate skeletal muscle glucose disposal or AMPK activation during moderate-intensity exercise in humans.

Sprint training reduces urinary purine loss following intense exercise in humans.

The influence of sprint training on endogenous urinary purine loss was examined in 7 active male subjects (age, 23.1 +/- 1.8 y; body mass, 76.1 +/- 3.1 kg; VO2 peak, 56.3 +/- 4.0 mL.kg-1.min-1). Each subject performed a 30 s sprint performance test (PT), before and after 7 d of sprint training. Training consisted of 15 sprints, each lasting 10 s, on an air-braked cycle ergometer performed twice each day. A rest period of 50 s separated each sprint during training. Sprint training resulted in a 20% higher muscle ATP immediately after PT, a lower IMP (57% and 89%, immediately after and 10 min after PT, respectively), and inosine accumulation (53% and 56%, immediately after and 10 min after the PT, respectively). Sprint training also attenuated the exercise-induced increases in plasma inosine, hypoxanthine (Hx), and uric acid during the first 120 min of recovery and reduced the total urinary excretion of purines (inosine + Hx + uric acid) in the 24 h recovery period following intense exercise. These results show that intermittent sprint training reduces the total urinary purine excretion after a 30 s sprint bout.

Creatine supplementation reduces muscle inosine monophosphate during endurance exercise in humans.

INTRODUCTION: Creatine (Cr) supplementation has been shown to attenuate increases in plasma ammonia and hypoxanthine during intense endurance exercise lasting 1 h, suggesting that Cr supplementation may improve muscle energy balance (matching of ATP resynthesis to ATP demand) during such exercise. We hypothesized that Cr supplementation would improve muscle energy balance (as assessed by muscle inosine monophosphate (IMP) accumulation) during intense endurance exercise. METHODS: Seven well-trained men completed two experimental trials involving approximately 1 h of intense endurance exercise (cycling 45 min at 78+/-1% & OV0312;O2 peak followed by completion of 251+/-6 kJ as quickly as possible (performance ride)). Subjects ingested approximately 42 g.d dextrose for 5 d before the first experimental trial (CON), then approximately 21 g Cr monohydrate plus approximately 21 g.d dextrose for 5 d before the second experimental trial (CREAT). Trials were ordered because of the long washout time for Cr. Subjects were blinded to the order of the trials. RESULTS: Creatine supplementation significantly (P< 0.05) increased muscle total Cr (resting values: CREAT: 138.1+/-7.9; CON: 117.7+/- 6.5 mmol.kg dm). No difference was seen between treatments in any measured muscle or blood metabolite after the first 45 min of exercise. Despite the performance ride completion time being similar in the two treatments ( approximately 13.5 min, approximately 86% & OV0312;O2 peak), IMP at the end of the performance ride was significantly (P<0.05) lower in CREAT than in CON (CREAT: 1.2+/- 0.6; CON: 2.0+/- 0.7 mmol.kg dm). CONCLUSION: Raising muscle total Cr content before exercise appears to improve the ability of the muscle to maintain energy balance during intense aerobic exercise, but not during more moderate exercise intensities.

The influence of allopurinol on urinary purine loss after repeated sprint exercise in man.

The influence of allopurinol on urinary purine loss was examined in 7 active male subjects (age 24.9 +/- 3.0 years, weight 82.8 +/- 8.3 kg, V O2peak 48.1 +/- 6.9 mL.kg(-1).min(-1)). These subjects performed, in random order, a trial with 5 days of prior ingestion of a placebo or allopurinol. Each trial consisted of eight 10-second sprints on an air-braked cycle ergometer and was separated by at least a week. A rest period of 50 seconds separated each repeated sprint. Forearm venous plasma inosine, hypoxanthine (Hx) and uric acid concentrations were measured at rest and during 120 minutes of recovery from exercise. Urinary inosine, Hx, xanthine, and uric acid excretion were also measured before and for 24 hours after exercise. During the first 120 minutes of recovery, plasma Hx concentrations, as well as the urinary Hx and xanthine excretion rates, were higher (P < .05) with allopurinol compared with the placebo trial. In contrast, plasma uric acid concentration and urinary uric acid excretion rates were lower (P < .05) with allopurinol. The total urinary excretion of purines (inosine + Hx + xanthine + uric acid) above basal levels was higher in the allopurinol trial compared with placebo. These results indicate that the total urinary purine excretion after intermittent sprint exercise was enhanced with allopurinol treatment. Furthermore, the composition of urinary purines was markedly affected by this drug.