Cold Ambient Temperature Does Not Alter Subcutaneous Abdominal Adipose Tissue Lipolysis and Blood Flow in Endurance-Trained Cyclists.

This study sought to investigate the effect of cold ambient temperature on subcutaneous abdominal adipose tissue (SCAAT) lipolysis and blood flow during steady-state endurance exercise in endurance-trained cyclists. Ten males (age: 23 ± 3 years; peak oxygen consumption: 60.60 ± 4.84 ml·kg-1·min-1; body fat: 18.4% ± 3.5%) participated in baseline lactate threshold (LT) and peak oxygen consumption testing, two familiarization trials, and two experimental trials. Experimental trials consisted of cycling in COLD (3 °C; 42% relative humidity) and neutral (NEU; 19 °C; 39% relative humidity) temperatures. Exercise consisted of 25 min cycling at 70% LT and 25 min at 90% LT. In situ SCAAT lipolysis and blood flow were measured via microdialysis. Heart rate, core temperature, carbohydrate and fat oxidation, blood glucose, and blood lactate were also measured. Heart rate, core temperature, oxygen consumption, and blood lactate increased with exercise but were not different between COLD and NEU. SCAAT blood flow did not change from rest to exercise or between COLD and NEU. Interstitial glycerol increased during exercise (p < .001) with no difference between COLD and NEU. Fat oxidation increased (p < .001) at the onset of exercise and remained elevated thereafter with no difference between COLD and NEU. Carbohydrate oxidation increased with increasing exercise intensity and was greater at 70% LT in COLD compared to NEU (p = .030). No differences were observed between conditions for any other variable. Cycling exercise increased SCAAT lipolysis but not blood flow. Ambient temperature did not alter SCAAT metabolism, SCAAT blood flow, or fat oxidation in well-trained cyclists, though cold exposure increased whole-body carbohydrate oxidation at lower exercise intensities.

Alaska Backcountry Expeditionary Hunting Promotes Sustained Muscle Protein Synthesis.

INTRODUCTION: We have previously described negative energy balance (ie, -9.7±3.4 MJ/d) and weight loss (Δ-1.5 ± 0.7 kg) influenced by high levels of energy expenditure (ie, 17.4±2.6 MJ/d) during remote expeditionary hunting in Alaska. Despite negative energy balance, participants retained skeletal muscle. The purpose of this pilot study was to measure skeletal muscle protein synthesis and examine molecular markers of skeletal muscle protein metabolism under similar conditions of physical and nutrient stress. METHODS: The "virtual biopsy method" was used to evaluate integrated fractional synthetic rates (FSRs) of muscle protein from blood samples in 4 participants. Muscle biopsies were taken to measure molecular markers of muscle protein kinetics (ie, FSTL1, MEF2, MYOD1, B2M, and miR-1-3p, -206, -208b, 23a, and 499a) using real-time polymerase chain reaction. RESULTS: Our findings in 4 participants (2 females [28 and 62 y of age; 66.2 and 71.8 kg body weight; 25.5 and 26.7 kg/m2 body mass index] and 2 males [47 and 56 y of age; 87.5 and 91.4 kg body weight; 26.1 and 28.3 kg/m2 body mass index]) describe mean muscle FSRs of serum carbonic anhydrase (2.4%) and creatine kinase M-type (4.0%) and positive increments in molecular regulation. CONCLUSIONS: Preservation of skeletal muscle under conditions of physical and nutrient stress seems to be supported by positive inflection of skeletal muscle FSR and molecular activation.

Independent effects of acute normobaric hypoxia and hypobaric hypoxia on human physiology.

The purpose of this study was to examine the effects of acute normobaric (NH, decreased FiO2) and hypobaric (HH, 4200 m ascent) hypoxia exposures compared to sea level (normobaric normoxia, NN). Tissue oxygenation, cardiovascular, and body fluid variables measured during rest and a 3-min step-test following 90-min exposures (NH, HH, NN). Muscle oxygenated hemoglobin (O2Hb) decreased, and muscle deoxygenated hemoglobin (HHb) increased environmentally independent from rest to exercise (p < 0.001). During exercise, brain O2Hb was lower at HH compared to NN (p = 0.007), trending similarly with NH (p = 0.066), but no difference between NN and NH (p = 0.158). During exercise, HR at NH (141 ± 4 beats·min-1) and HH (141 ± 3 beats·min-1) were higher than NN (127 ± 44 beats·min-1, p = 0.002), but not each other (p = 0.208). During exercise, stroke volume at HH (109.6 ± 4.1 mL·beat-1) was higher than NH (97.8 ± 3.3 mL·beat-1) and NN (99.8 ± 3.9 mL·beat-1, p ≤ 0.010) with no difference between NH and NN (p = 0.481). During exercise, cardiac output at NH (13.8 ± 0.6 L) and HH (15.5 ± 0.7 L) were higher than NN (12.6 ± 0.5 L, p ≤ 0.006) with HH also higher than NH (p = 0.001). During acute hypoxic stimuli, skeletal muscle maintains oxygenation whereas the brain does not. These differences may be mediated by environmentally specific cardiovascular compensation. Thus, caution is advised when equating NH and HH.

Skeletal Muscle mRNA Response to Hypobaric and Normobaric Hypoxia After Normoxic Endurance Exercise.

Background: The physiological effects of hypoxia may be influenced by how hypoxia is achieved. The purpose of this study was to determine the effects of recovery in hypobaric hypoxia (HH), normobaric hypoxia (NH), and normobaric normoxia (NN) after endurance exercise on gene expression related to mitochondrial biogenesis, myogenesis, and proteolysis. Methods: Fifteen recreationally trained subjects each cycled for 1 hour before recovering for 4 hours in NN (laboratory atmospheric conditions, 975 m), HH (depressurized to simulate 4420 m), and NH (fraction of O2 reduced to simulate 4420 m). Muscle biopsy samples were obtained before exercise and after 4 hours of recovery. Results: Blood oxygenation (SpO2) was lower in HH (76.02 ± 0.58%) than NH (79.45 ± 0.56, p < 0.001), which were both lower than in NN (96.3 ± 0.17, p < 0.001). Heart rate was higher in HH (82 ± 2 bpm) than NH (77 ± 1 bpm, p < 0.001), which were both higher than in NN (67 ± 1 bpm, p < 0.001). Mitochondrial transcription factor A (TFAM) mRNA was lower after NN than HH (p = 0.034) or NH (p = 0.005), but was not different between HH and NH (p = 0.460). Myostatin (MSTN) mRNA decreased from pre- to postexercise (p < 0.001) in all conditions and was lower in HH compared with NH (p = 0.035) and NN (p = 0.017). No other differences were noted in genes related to mitochondrial biogenesis, myogenesis, or proteolysis (p > 0.05). Conclusion:TFAM mRNA is lower with hypoxia exposure, but effected by the type of hypoxia. MSTN gene expression is lower after exposure to HH than NH or NN. These data support previous work and caution the translation of NH data obtained in a NH environment to a HH environment.

Effect of Plyometrics on the Energy Cost of Running and MHC and Titin Isoforms.

UNLABELLED: Several training strategies such as plyometrics have been shown to improve running economy; however, its physiological basis remains elusive. PURPOSE: To examine the effect of plyometric training on the energy cost of running (ECR, J · kg(-1) · min(-1)), titin, and myosin heavy chain (MHC) isoforms. METHODS: Subjects were randomly assigned to a 6-wk plyometric treatment (P; n = 11) or control group (C; n = 11). Preintervention and postintervention outcomes included body composition, vertical jump, sit-and-reach, maximal oxygen consumption (VO2max), speed at onset of blood lactate, 3-km time trial performance, ECR, and a vastus lateralis muscle biopsy for protein analysis. RESULTS: Plyometric intervention resulted in improved time trial (P, 2.6% faster, P = 0.04; C, 1.6%, P = 0.17). VO2max improved in the P group (5.2%, P = 0.03), whereas the C group increased by 3.1% (P = 0.20). The ECR decreased in the P group as the result of 6 wk of plyometric training (P = 0.02 for stage 3), whereas it increased in the C group (P = 0.02 for stage 3). The ECR correlated strongly with performance at stages 2, 3, and 4 (r > 0.8, P < 0.001) independent of group. There was no significant main effect of group, time, or interaction on any of the protein isoforms analyzed. A negative correlation was found between the ECR at stage 7 and MHC IIa (r = -0.96, P < 0.001), and the ECR at stage 6 with titin isoform 1 (T1)/T2 ratio (r = -0.69, P = 0.007) independent of group. CONCLUSION: Six weeks of plyometric training improved running performance and the ECR despite no measurable changes in MHC and titin isoforms. However, higher MHC IIa and lower T1/T2 isoform ratios correlated to lower ECR.

Postexercise Glycogen Recovery and Exercise Performance is Not Significantly Different Between Fast Food and Sport Supplements.

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.

Skeletal muscle metabolic gene response to carbohydrate feeding during exercise in the heat.

BACKGROUND: Heat stress down-regulates mitochondrial function, while carbohydrate supplementation attenuates the exercise induced stimulation of mitochondrial biogenesis in humans. The effects of exogenous carbohydrate during exercise in the heat on metabolic mRNA have not been investigated in humans. The purpose of this study was to determine the impact of exercise with and without carbohydrate supplementation on skeletal muscle metabolic response in the heat. METHODS: Eight recreationally active males (4.05 ± 0.2 L.min-1) completed 2 trials which included 1 hr of cycling at 70% workload max and 3 hr recovery in a hot environment. Both trials were conducted in a climate controlled environmental chamber (38°C and 40% RH). The trials differed by the consumption of either a 6% carbohydrate (CHO) containing beverage (8 ml.kg-1.hr-1) or placebo (P) during exercise in random order. Muscle biopsies were obtained from the vastus lateralis before exercise, immediately post-exercise and at the end of the 3 hr recovery period. Muscle was analyzed for muscle glycogen and mRNA related to metabolic and mitochondrial development (MFN2, PGC-1α, GLUT4, UCP3). Expired gases were measured to determine whole body substrate use during exercise. RESULTS: Carbohydrate oxidation and muscle glycogen utilization did not differ between trials, whereas fat oxidation was elevated during exercise in P. Exercise caused an increase in PGC-1α, and GLUT4 (P < 0.05) independent of exogenous carbohydrate provision. Carbohydrate consumption attenuated the mRNA response in UCP3 (P < 0.05). CONCLUSIONS: This study indicates that the provision of exogenous carbohydrate attenuates the stimulation of mRNA expression of UCP3 following exercise in the heat.

Fatigue biomarker index: an objective salivary measure of fatigue level.

Fatigue changed the composition of the small-molecular weight (sMW) proteome of saliva during a 10h session of moderate (70% of maximum ventilatory threshold) physical exertion. Saliva samples were collected from nine recreationally trained cyclists participating in a cross-over study designed to simulate prolonged manual labor, a military operation or wildfire-suppression work. During each hour of the study, participants performed an exercise program that included upper and lower body exercises separated by short periods of recovery. Over the course of the study, fatigue level increased as suggested by a significant increase in the participants' relative perceived exertion. The composition of the sMW proteome was investigated using reversed-phase liquid chromatography with mass-spectrometric detection. Isotopes of acetic anhydride were used for mass-specific labeling of samples and subsequent identification of ions with significant changes in intensity. Cluster analysis was used to identify a pair of peptides with concentrations that changed in opposite directions with fatigue level, i.e. concentration of one peptide increased while concentration of the other decreased. The sequences of the two peptides were determined by high-resolution mass spectrometry. The ratio of the ion intensities of these two peptides, referred to as the fatigue biomarker index, was calculated for subjects throughout the study. The FBI values from the start of the study likely arose from a different distribution than the FBI values measured at the end of the study (Mann-Whitney test, P<.05). While this study is restricted to a small population of recreationally trained cyclists performing exercise under controlled conditions, it holds promise for the development of an objective salivary measurement of fatigue that is applicable to a much broader population performing in uncontrolled environments.

Metabolic profile of the Ironman World Championships: a case study.

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 field measures to estimate energy expenditure and substrate utilization. The subject was provided with an oral dose of ²H2(18)O 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.

Efficacy of eat-on-move ration for sustaining physical activity, reaction time, and mood.

UNLABELLED: Repeated carbohydrate feedings and caffeine have been shown to increase self-paced physical activity. Whether a field ration pack that promotes snacking of these items would enhance physical activity remains unclear. PURPOSE: Evaluate the effectiveness of a ration pack consisting of eat-on-move items to promote snacking, as well as caffeine items, as a nutritional strategy to improve performance. METHODS: Twenty-eight wildland firefighters consumed both an eat-on-move ration (first strike ration (FSR): 13.2 MJ, 420 g CHO, 665 mg caffeine daily) and entrée-based ration (meals, ready-to-eat (MRE): 11.9 MJ, 373 g CHO, 100 mg caffeine daily) for 2 d separated by 1 d. Diet order was counterbalanced. Outcome measurements included self-paced physical activity determined by actimetry, reaction time, number of eating occasions using dietary recall, and dietary intake from food wrapper collection. RESULTS: Total eating episodes were higher with FSR compared with MRE (P = 0.013; mean +/- SD: 8.2 +/- 1.3 vs 7.6 +/- 1.1 episodes x 2 d(-1)), as were 2-d energy intake (22.0 +/- 2.4 vs 18.4 +/- 2.5 MJ; P < 0.01), carbohydrate intake (698 +/- 76 vs 546 +/- 82 mg; P < 0.01), self-reported caffeine intake (347 +/- 262 vs 55 +/- 65 mg; P < 0.01), and average end-shift salivary caffeine (1.6 +/- 1.9 vs 0.7 +/- 1.0 microg x mL(-1); P < 0.01). Total activity counts were higher (P = 0.046) when consuming FSR (507,833 +/- 129,130 counts per shift) compared with MRE (443,095 +/- 142,208 counts per shift). This was accomplished by spending a greater percentage of work shift with activity counts >1000 counts x min(-1) (21 +/- 8% vs 18 +/- 6%; P = 0.01) and less percent of work shift <50 counts x min(-1) (33 +/- 10% vs 38 +/- 10%; P = 0.01). CONCLUSIONS: Delivery of energy and caffeine in a manner that promotes snacking behavior is advantageous for increasing self-selected physical activity during arduous labor.

Muscle glycogenolysis and resynthesis in response to a half Ironman triathlon: a case study.

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.

Estradiol effects on the growth hormone/insulin-like growth factor-1 axis in amenorrheic athletes.

Disruption of the growth hormone/insulin-like growth factor-1 (GH/IGF-1) axis has been reported and studied in menopause, hypothalamic amenorrhea, and anorexia nervosa, but not in weight-stable amenorrheic athletes. We investigated the effects of short-term transdermal estradiol on basal and exercise-stimulated serum GH, IGF-1, and associated binding proteins (IGFBP-1 and IGFBP-3) in seven weight-stable female amenorrheic athletes with percentage body fats greater that 12%. Each subject received a 72 h placebo patch followed by 144 h of transdermal estradiol. Serum samples for GH, IGF-1, IGFBP-1, and IGFBP-3 were obtained at baseline (t1), 72 hr (t2), 144 hr (t3), and during three 90-minute trials of aerobic exercise. Basal, and exercise GH, IGF-1, and IGFBP-1 were not different between trials. Baseline IGFBP-3 decreased from t1 to t2 (p = 0.04) and serum free fatty acids increased from t1 to t2, and t1 to t3 (p = 0.04, and 0.02 respectively). These findings differ from postmenopausal women, and women having weightloss-associated amenorrhea, suggesting that estrogen, exercise, and nutritional deficiencies may have independent effects on the GH/IGF-1 axis.

Regulation of exercise carbohydrate metabolism by estrogen and progesterone in women.

To assess the roles of endogenous estrogen (E2) and progesterone (P4) in regulating exercise carbohydrate use, we used pharmacological suppression and replacement to create three distinct hormonal environments: baseline (B), with E2 and P4 low; estrogen only (E), with E2 high and P4 low; and estrogen/progesterone (E + P), with E2 and P4 high. Blood glucose uptake (R(d)), total carbohydrate oxidation (CHO(ox)), and estimated muscle glycogen utilization (EMGU) were assessed during 60 min of submaximal exercise by use of stable isotope dilution and indirect calorimetry in eight eumenorrheic women. Compared with B (1.26 +/- 0.04 g/min) and E + P (1.27 +/- 0.04 g/min), CHO(ox) was lower with E (1.05 +/- 0.02 g/min). Glucose R(d) tended to be lower with E and E + P relative to B. EMGU was 25% lower with E than with B or E + P. Plasma free fatty acids (FFA) were inversely related to EMGU (r(2) = 0.49). The data suggest that estrogen lowers CHO(ox) by reducing EMGU and glucose R(d). Progesterone increases EMGU but not glucose R(d). The opposing actions of E(2) and P(4) on EMGU may be mediated by their impact on FFA availability or vice versa.