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The Influence of a High Carbohydrate Intake during Recovery from Prolonged, Constant-Pace Running

Joanne L. Fallowfield and Clyde Williams

The present study examined the influence of ingesting 3.0 g CHO · kg 1 body mass ⋅ 2  hr 1 after prolonged exercise on recovery and running capacity 4 hr later. Nine men and 8 women completed two trials in a counterbalanced design. Each trial consisted of a 90-min run on a level treadmill at 70% VO 2 max ( R t ) followed by 4 hr recovery (REC) and a further exhaustive run at 70% VO 2 max (R2). During REC, subjects ingested either two feedings of a 6.9% glucose-polymer (GP) solution (D trial) or two feedings of a 19.3% GP solution (C trial). There were no differences in mean (±SE) R 2 run times between the C and D trials or between the male and female subjects. More stable blood glucose concentrations were maintained during REC in the C trial, such that blood glucose was elevated in the C trial in comparison with the D trial after 210 min of REC. It was concluded that increasing postexercise carbohydrate intake from 1.0 to 3.0 g CHO ⋅ Kg 1 body mass 2  hr 1 does not improve endurance capacity 1 hr later.

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Hematological Status of Male Runners in Relation to the Extent of Physical Training

John D. Robertson, Ronald J. Maughan, Ann C. Milne, and Ronald J.L. Davidson

Blood biochemical indices of iron status were measured in venous blood from 20 runners and 6 control subjects. All subjects were.male, ages 20 to 40 years, and stable with regard to body weight and degree of physical activity. Dietary analysis was undertaken using a 7-day weighed food intake. There was no evidence of iron deficiency: hemoglobin concentrations and serum femtin levels were within the normal population range for all individuals. However, serum ferritin was negatively correlated with the amount of training. Daily iron intake appeared to be adequate; iron intake was correlated with protein intake but not related to training or energy intake. Serum ferritin, an indicator of iron status, was significantly correlated with vitamin C intake but not iron intake. Serum transferrin concentration was higher in the group of athletes undertaking a high weekly training load compared with the control subjects, suggesting an alteration in iron metabolism although there was no evidence of increased erythropoiesis. The biological significance of this is unclear.

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Carbohydrate Intake and Recovery from Prolonged Exercise

Joanne L. Fallowfield and Clyde Williams

The influence of increased carbohydrate intake on endurance capacity was investigated following a bout of prolonged exercise and 22.5 hrs of recovery. Sixteen male subjects were divided into two matched groups, which were then randomly assigned to either a control (C) or a carbohydrate (CHO) condition. Both groups ran at 70% VO2max on a level treadmill for 90 min or until volitional fatigue, whichever came first (T1), and 22.5 hours later they ran at the same % VO2max for as long as possible to assess endurance capacity (T2). During the recovery, the carbohydrate intake of the CHO group was increased from 5.8 (±0.5) to 8.8 (±0.1) g kg-1 BW. This was achieved by supplementing their normal diet with a 16.5% glucose-polymer solution. An isocaloric diet was prescribed for the C group, in which additional energy was provided in the form of fat and protein. Run times over T1 did not differ between the groups. However, over T2 the run time of the C group was reduced by 15.57 min (p<0.05), whereas those in the CHO group were able to match their T1 performance. Blood glucose remained stable throughout Tl and T2 in both groups. In contrast, blood lactate, plasma FFA, glycerol, ammonia, and urea increased. Thus, a high carbohydrate diet restored endurance capacity within 22.5 hrs whereas an isocaloric diet without additional carbohydrate did not.

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The Assessment of Total Energy Expenditure During a 14-Day In-Season Period of Professional Rugby League Players Using the Doubly Labelled Water Method

James Cameron Morehen, Warren Jeremy Bradley, Jon Clarke, Craig Twist, Catherine Hambly, John Roger Speakman, James Peter Morton, and Graeme Leonard Close

Rugby League is a high-intensity collision sport competed over 80 min. Training loads are monitored to maximize recovery and assist in the design of nutritional strategies although no data are available on the total energy expenditure (TEE) of players. We therefore assessed resting metabolic rate (RMR) and TEE in six Super League players over 2 consecutive weeks in-season including one game per week. Fasted RMR was assessed followed by a baseline urine sample before oral administration of a bolus dose of hydrogen (deuterium 2H) and oxygen (18O) stable isotopes in the form of water (2H2 18O). Every 24 hr thereafter, players provided urine for analysis of TEE via DLW method. Individual training load was quantified using session rating of perceived exertion (sRPE) and data were analyzed using magnitude-based inferences. There were unclear differences in RMR between forwards and backs (7.7 ± 0.5 cf. 8.0 ± 0.3 MJ, respectively). Indirect calorimetry produced RMR values most likely lower than predictive equations (7.9 ± 0.4 cf. 9.2 ± 0.4 MJ, respectively). A most likely increase in TEE from Week 1 to 2 was observed (17.9 ± 2.1 cf. 24.2 ± 3.4 MJ) explained by a most likelyincrease in weekly sRPE (432 ± 19 cf. 555 ± 22 AU), respectively. The difference in TEE between forward and backs was unclear (21.6 ± 4.2 cf. 20.5 ± 4.9 MJ, respectively). We report greater TEE than previously reported in rugby that could be explained by the ability of DLW to account for all match and training-related activities that contributes to TEE.

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Short-Term Stability of Urine Electrolytes: Effect of Time and Storage Conditions

J.D. Adams, Miranda Badolato, Ethan Pierce, Abbie Cantrell, Zac Parker, and Donya Farzam

.) are being affected the most to cause a change in osmolality in such a short time. The report of specimen storage and stability written by the World Health Organization states urine Na + is stable for 1 year at −20 °C, 45 days at 4–8 °C, and 45 days at 20–25 °C. Similarly, urine K + is stable for 1

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Effect of Preexercise Ingestion of Modified Amylomaize Starch on Glycemic Response While Cycling

Rachel B. Parks, Hector F. Angus, Douglas S. King, and Rick L. Sharp

stable serum glucose and insulin concentrations during and after exercise. In contrast, ingestion of dextrose caused a rapid preexercise increase in serum glucose and insulin, subsequent decline in serum glucose to below-baseline levels during exercise despite normalization of insulin concentration

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Methodological Considerations for Investigating Iron Status and Regulation in Exercise and Sport Science Studies

Alannah K.A. McKay, Marc Sim, Diego Moretti, Rebecca Hall, Trent Stellingwerff, Richard J. Burden, and Peter Peeling

investigations on iron metabolism in active, and athlete populations, addressing key factors such as the measurement of iron status, hepcidin and exercise interactions, dietary intake, female-specific considerations, and the use of stable iron isotope tracer methodologies. It is intended that this review can be

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The Effect of Storing Temperature and Duration on Urinary Hydration Markers

J.D. Adams, Stavros A. Kavouras, Evan C. Johnson, Lisa T. Jansen, Catalina Capitan-Jimenez, Joseph I. Robillard, and Andy Mauromoustakos

The purpose of this investigation was to quantify the effects of storage temperature, duration, and the urinary sediment on urinary hydration markers. Thirty-six human urine samples were analyzed fresh and then the remaining sample was separated into 24 separate vials, six in each of the following four temperatures: 22 °C, 7 °C, -20 °C, and -80 °C. Two of each sample stored in any given temperature, were analyzed after 1, 2, and 7 days either following vortexing or centrifugation. Each urine sample was analyzed for osmolality (UOsm), urine specific gravity (USG), and urine color (UC). UOsm was stable at 22 °C, for 1 day (+5–9 mmol∙kg-1, p > .05) and at 7 °C, UOsm up to 7 days (+8–8 mmol∙kg-1, p > .05). At -20 and -80 °C, UOsm decreased after 1, 2, and 7 days (9–61 mmol∙kg-1, p < .05). Vortexing the sample before analysis further decreased only UOsm in the -20 °C and -80 °C storage. USG remained stable up to 7 days when samples were stored in 22 °C or 7 °C (p > .05) but declined significantly when stored in -20 °C, and -80 °C (p < .001). UC was not stable in any of the storing conditions for 1, 2, and 7 days. In conclusion, these data indicate that urine specimens analyzed for UOsm or USG remained stable in refrigerated (7 °C) environment for up to 7 days, and in room temperature for 1 day. However, freezing (-20 and -80 °C) samples significantly decreased the values of hydration markers.

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For Flux Sake: Isotopic Tracer Methods of Monitoring Human Carbohydrate Metabolism During Exercise

Javier T. Gonzalez and Andy J. King

). Approximately 1.1% of carbon on earth is 13 C which has an extra neutron, and therefore, greater mass than 12 C. However, as neutrons are chargeless particles, the chemical properties and interactions are assumed to be identical. 13 C is a stable isotope since it is not radioactive. Carbon-14 ( 14 C

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Retraction: Medeiros et al. (2022)

James A. Betts

interventions and, moreover, is mathematically incompatible with the completely stable relative V ˙ O 2 max (mL·kg −1 ·min −1 ) values reported in the same paper (unless body mass changed by circa 18 kg). The authors of the original article were asked to provide an explanation for the apparent