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N.D. Clarke, B. Drust, D.P.M. MacLaren and T. Reilly

The aim of the present study was to investigate the effect of manipulating the provision of sports drink during soccer-specific exercise on metabolism and performance. Soccer players (N = 12) performed a soccer-specific protocol on three occasions. On two, 7 mL/kg carbohydrate-electrolyte (CHOv) or placebo (PLA) solutions were ingested at 0 and 45 min. On a third, the same total volume of carbohydrate-electrolyte was consumed (CHOf) in smaller volumes at 0, 15, 30, 45, 60, and 75 min. Plasma glucose, glycerol, non-esterified free fatty acids (NEFA), cortisol, and CHO oxidation were not significantly different between CHOv and CHOf (P > 0.05). Sprint power was not significantly affected (P > 0.05) by the experimental trials. This study demonstrates when the total volume of carbohydrate consumed is equal, manipulating the timing and volume of ingestion elicits similar metabolic responses without affecting exercise performance.

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Marcus Smith, Rosemary Dyson, Tudor Hale, Matthew Hamilton, John Kelly and Peggy Wellington

This study examined the effects of serial reductions in energy and fluid intake on two simulated boxing performances separated by 2 days recovery. Eight amateur boxers (age: 23.6 ± 3.2 years; height 175 ± 5 cm; body mass [BM] 73.3 ± 8.3 kg [Mean ± SD]) performed two simulated boxing bouts (BB) under normal (N-trial) and restricted (R-trial) diets in a counterbalanced design over 5 days. The trials were separated by a 9-day period of normal dietary behavior (X-trial). BM was recorded on days 1, 3, and 5 of each trial. Simulated bouts of three, 3-min rounds with 1-min recovery were completed on days 3 (BB1) and 5 (BB2) of each 5-day trial. Punching force (N) was recorded from 8 sets of 7 punches by a purpose-built boxing ergometer. Heart rate (fC) was monitored continuously (PE3000 Polar Sports Tester, Kempele, Finland), and blood lactate (BLa) and glucose (BG) were determined 4-min post-performance (2300 StaPlus, YSI, Ohio). Energy and fluid intakes were significantly lower in the R-trial (p < .05). Body mass was maintained during the N-trial but fell 3% (p < .05) during the R-trial. There were no significant differences in end-of-bout fC or post-bout BG, but BLa was higher in the N- than the R-trial (p < .05). R-trial punching forces were 3.2% and 4.6% lower, respectively, compared to the corresponding N-trial bouts, but the differences did not reach statistical significance. These results suggest that energy and fluid restrictions in weight-governed sports do not always lead to a significant decrease in performance, but because of the small sample size and big variations in individual performances, these findings should be interpreted with care.

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Hamish A.B. Reid, Nicholas C. Dennison, Jonathan Quayle and Tom Preston

Meeting the energy demands of prolonged arduous expeditions and endurance sport may be a significant barrier to success. Expedition rowing is associated with high levels of body-mass loss, reflecting the challenge of meeting energy expenditure in this exacting environment.

Purpose:

To use the doubly labeled water (DLW) technique to calculate the total energy expenditure (TEE) and body-composition changes of two 28-y-old healthy male athletes during a 50-d continuous and unsupported row around Great Britain.

Methods:

A measured dose of DLW was taken at the start of 2 separate study periods (days 5–19 and 34–48) followed by sequential urine collection, which was analyzed on return to land.

Results:

Mean TEE was 15.3 MJ/d: athlete 1, 16.4 MJ/d; athlete 2, 14.9 MJ/d. Athlete 1 lost 11.2 kg and athlete 2 lost 14.9 kg of body mass during the row. Average energy provision was 19.1 MJ per 24-h ration pack.

Conclusions:

These results highlight the difficulty of maintaining energy balance during expedition rowing. A starvation state was observed despite dietary provision in excess of estimated energy expenditure, indicating that nutritional strategy rather than caloric availability was at fault. The authors recommend that future expeditions prioritize thorough testing and the individualization of rations to ensure that they are both palatable and practical during the weeks to months at sea.

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Abbass Ghanbari-Niaki, Rozita Fathi, Sayed Alireza Hossaini Kakhak, Zhara Farshidi, Sara Barmaki, Fatemeh Rahbarizadeh and Robert R. Kraemer

Agouti-related protein (AGRP) is an orexigenic peptide secreted from the arcuate nucleus (ARC) of the hypothalamus. AGRP increases food intake and plays a role in energy balance, adiposity, weight gain, and growth-hormone release. The objective of the current study was to examine the effects of running exercise on resting hepatic, fundus, and pancreas AGRP mRNA expression, as well as liver glycogen and ATP contents, using a rat model. Twenty adult male Wistar rats (12–14 wk old, 200–220 g) were randomly assigned to control (n = 10) and training (n = 10) groups. The training group was exercised for 8 wk on a motor-driven treadmill (26 m/min, 0% grade, 60 min, 5 d/wk). Twenty-four hours before sacrifice the rats were further divided into fed control (FEC), fed trained (FET), fasted control (FAC), and fasted trained (FAT) groups. The liver, fundus, and pancreas were excised and frozen in liquid nitrogen for later analysis. Results demonstrated that 8 wk of treadmill exercise reduced hepatic but not fundus and pancreatic AGRP expression and enhanced glycogen and ATP concentrations (p < .001) in trained-rat liver, whereas fasting lowered liver glycogen and ATP levels and increased hepatic AGRP mRNA expression in nonexercising controls. Data indicate that both treadmill-exercise-induced decrease and fast-induced increase in rat liver AGRP expression might depend on liver glycogen content as an important source for energy provision.

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Martin J. Gibala

The contribution of amino acid oxidation to total energy expenditure is negligible during short-term intense exercise and accounts for 3–6% of the total adenosine triphosphate supplied during prolonged exercise in humans. While not quantitatively important in terms of energy supply, the intermediary metabolism of several amino acids—notably glutamate, alanine, and the branched-chain amino acids—afreets other metabolites .including the intermediates within the tricarboxylic acid (TCA) cycle. Glutamate appears to be a key substrate for the rapid increase in muscle TCA cycle intermediates (TCAI) that occurs at the onset of moderate to intense exercise, due to a rightward shift of the reaction catalyzed by alanine aminotransferase (glutamate + pyruvate <-> alanine + 2-oxoglutarate). The pool of muscle TCAI declines during prolonged exercise, and this has been attributed to an increase in leucine oxidation that relies on one of the TCAI. However, this mechanism does not appear to be quantitatively important due of the relatively low maximal activity of branched-chain oxoacid dehydrogenase, the key enzyme involved. It has been suggested that an increase in TCAI is necessary to attain high rates of aerobic energy production and that a decline in TCAI may be a causative factor in local muscle fatigue. These topics remain controversial, but recent evidence suggests that changes in TCAI during exercise are unrelated to oxidative energy provision in skeletal muscle.

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. Warren * Leah Moore Thomas * J. Andrew Doyle * Teresa Snow * Kristen Hitchcock * 12 2005 15 15 6 6 610 610 624 624 10.1123/ijsnem.15.6.610 Strategies for Hydration and Energy Provision during Soccer-Specific Exercise N.D. Clarke * B. Drust * D.P.M. MacLaren * T. Reilly * 12 2005 15 15 6 6

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Ben Desbrow, Katelyn Barnes, Gregory R. Cox, Elizaveta Iudakhina, Danielle McCartney, Sierra Skepper, Caroline Young and Chris Irwin

acute energy provision provided by caloric beverages is not typically offset by a subsequent reduction in food/fluid intake over the remainder of a day ( Campagnolo et al., 2017 ; McCartney et al., 2019 ). Collectively, our two investigations into recovery areas following mass participation

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Naroa Etxebarria, Megan L. Ross, Brad Clark and Louise M. Burke

receptors to CHO and the central nervous system was springboarded. There is now robust evidence that the exposure (5–10 s) of these receptors to CHO activates areas in the brain that control perceptions of effort and pacing decisions. This activation creates a cascade of events that signal energy provision

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Petros G. Botonis, Ioannis Malliaros, Gavriil G. Arsoniadis, Theodoros I. Platanou and Argyris G. Toubekis

suggesting that aerobic metabolism dominates the energy delivery throughout a match-play. In addition, the high occurrence of high-intensity efforts such as dynamic body contacts and swimming sprints 3 , 4 implies that in addition to aerobic, anaerobic metabolism appears to play a decisive role in energy

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Iñigo Mujika

et al., 2006 ) and 37.2–42.0 MJ ( Cuddy et al., 2010 ; Kimber et al., 2002 ), respectively. In terms of energy provision, there is a major reliance on oxidation of both endogenous glycogen and exogenous carbohydrate (CHO) ( Cuddy et al., 2010 ; Kimber et al., 2002 ), particularly in the half