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Trevor L. Gillum, Charles L. Dumke and Brent C. Ruby

Purpose:

To describe the degrees of muscle-glycogen depletion and resynthesis in response to a half Ironman triathlon.

Methods:

One male subject (38 years of age) completed the Grand Columbian half Ironman triathlon (1.9-km swim, 90-km bike, 21.1-km run, Coulee City, Wash). Three muscle biopsies were obtained from his right vastus lateralis (prerace, immediately postrace, and 4 hours postrace). Prerace and postrace body weight were recorded, in addition to macronutrient consumption before, during, and after the race. Energy expenditure and whole-body substrate oxidation were estimated from linear regression established from laboratory trials (watts and run pace relative to VO2 and VCO2).

Results:

Body weight decreased 3.8 kg from prerace to postrace. Estimated CHO energy expenditure was 10,003 kJ for the bike segment and 5759 kJ for the run segment of the race. The athlete consumed 308 g of exogenous CHO (liquid and gel; 1.21 g CHO/min) during the race. Muscle glycogen decreased from 227.1 prerace to 38.6 mmol · kg wet weight−1 · h−1 postrace. During the 4 hours postrace, the athlete consumed a mixed diet (471 g CHO, 15 g fat, 64 g protein), which included liquid CHO sources and a meal. The calculated rate of muscle-glycogen resynthesis was 4.1 mmol · kg wet weight−1 · h−1.

Conclusion:

Completing a half Ironman triathlon depends on a high rate of muscle glycogenolysis, which demonstrates the importance of exogenous carbohydrate intake during the race. In addition, rates of muscle-glycogen resynthesis might be dampened by the eccentric damage resulting from the run portion of the race.

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Michael J. Cramer, Charles L. Dumke, Walter S. Hailes, John S. Cuddy and Brent C. Ruby

A variety of dietary choices are marketed to enhance glycogen recovery after physical activity. Past research informs recommendations regarding the timing, dose, and nutrient compositions to facilitate glycogen recovery. This study examined the effects of isoenergetic sport supplements (SS) vs. fast food (FF) on glycogen recovery and exercise performance. Eleven males completed two experimental trials in a randomized, counterbalanced order. Each trial included a 90-min glycogen depletion ride followed by a 4-hr recovery period. Absolute amounts of macronutrients (1.54 ± 0.27 g·kg-1 carbohydrate, 0.24 ± 0.04 g·kg fat-1, and 0.18 ± 0.03g·kg protein-1) as either SS or FF were provided at 0 and 2 hr. Muscle biopsies were collected from the vastus lateralis at 0 and 4 hr post exercise. Blood samples were analyzed at 0, 30, 60, 120, 150, 180, and 240 min post exercise for insulin and glucose, with blood lipids analyzed at 0 and 240 min. A 20k time-trial (TT) was completed following the final muscle biopsy. There were no differences in the blood glucose and insulin responses. Similarly, rates of glycogen recovery were not different across the diets (6.9 ± 1.7 and 7.9 ± 2.4 mmol·kg wet weight- 1·hr-1 for SS and FF, respectively). There was also no difference across the diets for TT performance (34.1 ± 1.8 and 34.3 ± 1.7 min for SS and FF, respectively. These data indicate that short-term food options to initiate glycogen resynthesis can include dietary options not typically marketed as sports nutrition products such as fast food menu items.

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John S. Cuddy, Dustin R. Slivka, Walter S. Hailes, Charles L. Dumke and Brent C. Ruby

Purpose:

The purpose of this study was to determine the metabolic profile during the 2006 Ironman World Championship in Kailua-Kona, Hawaii.

Methods:

One recreational male triathlete completed the race in 10:40:16. Before the race, linear regression models were established from both laboratory and feld measures to estimate energy expenditure and substrate utilization. The subject was provided with an oral dose of 2H2 18O approximately 64 h before the race to calculate total energy expenditure (TEE) and water turnover with the doubly labeled water (DLW) technique. Body weight, blood sodium and hematocrit, and muscle glycogen (via muscle biopsy) were analyzed pre- and postrace.

Results:

The TEE from DLW and indirect calorimetry was similar: 37.3 MJ (8,926 kcal) and 37.8 MJ (9,029 kcal), respectively. Total body water turnover was 16.6 L, and body weight decreased 5.9 kg. Hematocrit increased from 46 to 51% PCV. Muscle glycogen decreased from 152 to 48 mmoL/kg wet weight pre- to postrace.

Conclusion:

These data demonstrate the unique physiological demands of the Ironman World Championship and should be considered by athletes and coaches to prepare sufficient nutritional and hydration plans.

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Lindsey E. Miller, Graham R. McGinnis, Brian Kliszczewicz, Dustin Slivka, Walter Hailes, John Cuddy, Charles Dumke, Brent Ruby and John C. Quindry

Oxidative stress occurs as a result of altitude-induced hypobaric hypoxia and physical exercise. The effect of exercise on oxidative stress under hypobaric hypoxia is not well understood.

Purpose:

To determine the effect of high-altitude exercise on blood oxidative stress. Nine male participants completed a 2-d trek up and down Mt Rainer, in North America, at a peak altitude of 4,393 m. Day 1 consisted of steady-pace climbing for 6.25 hr to a final elevation of 3,000 m. The 4,393-m summit was reached on Day 2 in approximately 5 hr. Climb–rest intervals varied but were consistent between participants, with approximately 14 hr of total time including rest periods. Blood samples were assayed for biomarkers of oxidative stress and antioxidant potential at the following time points: Pre (before the trek), 3Kup (at ascent to 3,000 m), 3Kdown (at 3,000 m on the descent), and Post (posttrek at base elevation). Blood serum variables included ferric-reducing antioxidant potential (FRAP), Trolox equivalent antioxidant capacity (TEAC), protein carbonyls (PC), and lipid hydroperoxides. Serum FRAP was elevated at 3Kup and 3Kdown compared with Pre and Post values (p = .004, 8% and 11% increase from Pre). Serum TEAC values were increased at 3Kdown and Post (p = .032, 10% and 18% increase from Pre). Serum PC were elevated at 3Kup and 3Kdown time points (p = .034, 194% and 138% increase from Pre), while lipid hydroperoxides were elevated Post only (p = .004, 257% increase from Pre).

Conclusions:

Findings indicate that high-altitude trekking is associated with increased blood oxidative stress.