Preliminary comparisons between a point-of-care ketometer and reference method using Steller sea lion pup whole blood and plasma.

We evaluated the Precision Xtra™ ketometer as part of a larger study categorizing fasting status of free-ranging Steller sea lion (Eumetopias jubatus; SSL) pups which necessitated the identification of plasma ß-hydroxybutyrate concentrations ([ß-HBA]) around a threshold of <0.3 and ≥0.3 mmol/l. Whole blood samples mixed with sodium heparin (NaHep) or ethylenediaminetetraacetic acid liquid anticoagulants were tested <10 minutes after collection (n = 14; triplicate technical replicates). Plasma (stored at -80°C, NaHep, Thaw1) measured via our laboratory's Reference Assay (Sigma Aldrich, St. Louis, MO, Kit #MAK041) served as the standard [ß-HBA] for ketometer comparisons. Our observed ß-HBA range (0.0-1.6 mmol/l), consistent with published [ß-HBA] of free-ranging Otariid pups, represented the lower 20% of the ketometer's range (0.0-8.0 mmol/l). The maximal coefficient of variation (%CV) of ketometer technical replicates was 9.1% (NaHep, whole blood). The majority of ketometer technical replicate sets (84%, including all matrices, anticoagulants and thawings) were identical (CV = 0%). We found linear relationships and agreement of ketometer [ß-HBA] between whole blood preserved with different anticoagulants and between whole blood and plasma (Thaw1) measurements. The ketometer produced results with linearity to the Reference Assay for both whole blood and plasma (Thaw1). We identified a non-linear relationship between plasma at Thaw1 and Thaw2 (tested four months apart, NaHep), as only samples with higher SSL [ß-HBA] decreased in concentration, and all others remained the same. With respect to categorizing SSL pup fasting in our larger study, the ketometer's %Accuracy, %Sensitivity and %Specificity for samples with Reference Assay ß-HBA <0.2 and >0.4 mmol/l were 100%. We adopted a modified procedure: plasma samples with mean ketometer concentrations ±0.1 mmol/l of 0.3 mmol/l ß-HBA were re-evaluated using the Reference Assay, improving measurement precision from tenths (ketometer) to thousandths (assay) mmol/l. The Precision Xtra™ ketometer was valuable to our application over the range of [ß-HBA] observed in SSL pup plasma and whole blood samples.

Fasting durations of Steller sea lion pups vary among subpopulations-evidence from two plasma metabolites.

Geographic differences in population growth trends are well-documented in Steller sea lions (Eumetopias jubatus), a species of North Pacific pinniped listed under the U.S. Endangered Species Act in 1990 following a marked decline in population abundance that began during the 1970s. As population growth is intrinsically linked to pup production and survival, examining factors related to pup physiological condition provides useful information to management authorities regarding potential drivers of regional differences. During dam foraging trips, pups predictably transition among three fasting phases, distinguished by the changes in the predominant metabolic byproduct. We used standardized ranges of two plasma metabolites (blood urea nitrogen and ß-hydroxybutyrate) to assign pups to fasting categories (n = 1528, 1990-2016, 12 subpopulations): Recently Fed-Phase I (digestion/assimilation-expected hepatic/muscle glycogen usage), Phase II (expected lipid utilization), transitioning between Phases II-III (expected lipid utilization with increased protein reliance), or Phase III (expected protein catabolism). As anticipated, the majority of pups were classified as Recently Fed-Phase I (overall mean proportion = 0.72) and few pups as Phase III (overall mean proportion = 0.04). By further comparing pups in Short (Recently Fed-Phase II) and Long (all other pups) duration fasts, we identified three subpopulations with significantly (P < 0.03) greater proportions of pups dependent upon endogenous sources of energy for extended periods, during a life stage of somatic growth and development: the 1) central (0.27 ± 0.09) and 2) western (0.36 ± 0.13) Aleutian Island (declining population trend) and 3) southern Southeast Alaska (0.32 ± 0.06; increasing population trend) subpopulations had greater Long fast proportions than the eastern Aleutian Islands (0.10 ± 0.05; stabilized population). Due to contrasting population growth trends among these highlighted subpopulations over the past 50+ years, both density-independent and density-dependent factors likely influence the dam foraging trip duration, contributing to longer fasting durations for pups at some rookeries.

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.

Physiology of the Wildland Firefighter: Managing Extreme Energy Demands in Hostile, Smoky, Mountainous Environments.

Wildland firefighters (WLFFs) are inserted as the front-line defense to minimize loss of natural resources, property, and human life when fires erupt in forested regions of the world. The WLFF occupation is physically demanding as exemplified by total daily energy expenditures that can exceed 25 MJ/day (6000 calories). WLFFs must also cope with complex physical and environmental situations (i.e., heat, altitude, smoke, compromised sleep, elevated stress) which challenge thermoregulatory responses, impair recovery, and increase short- and long-term injury/health risks while presenting logistical obstacles to nutrient and fluid replenishment. The occupation also imposes emotional strain on both the firefighter and their families. The long-term implications of wildfire management and suppression on the physical and mental health of WLFFs are significant, as the frequency and intensity of wildland fire outbreaks as well as the duration of the fire season is lengthening and expected to continue to expand over the next three decades. This article details the physical demands and emerging health concerns facing WLFFs, in addition to the challenges that the U.S. Forest Service and other international agencies must address to protect the health and performance of WLFFs and their ability to endure the strain of an increasingly dangerous work environment. © 2023 American Physiological Society. Compr Physiol 13:4587-4615, 2023.

Adiponectin, leptin, cortisol, neuropeptide Y and profile of mood states in athletes participating in an ultramarathon during winter: An observational study.

Background: The Montane® Yukon Arctic Ultra (YAU) is one of the longest (690 km) and coldest (+10.6°C-43.9°C) ultramarathons worldwide. Taking part in an ultramarathon is associated with great physiological and psychological stress, which can affect one's mood, level of hormones, and peptides. The current study aimed to identify relationships between peptides, hormones, and mood states in participants during this ultramarathon. Methods: The study cohort consisted of 36 participants (19 men, 17 women, 38.64 ± 9.12 years) split into a finisher (n = 10), non-finisher (n = 19), and control group (n = 7). Data were collected at four time points: baseline (PRE), during (D1 after 277 km, D2 after 383 km), and after the race (POST). Questionnaires were used to assess ratings of perceived exertion (RPE), total quality of recovery (TQR), and profile of mood states (POMS-SF). Serum NPY, leptin, adiponectin, and cortisol were measured. Results: Among non-finishers, scores for confusion, anger, depression, and tension-anxiety (PRE vs. D2, p < 0.05) increased, while vigor decreased (PRE vs. D1, p < 0.05). In contrast, finishers' tension-anxiety scores decreased (PRE vs. D1, p < 0.05). Fatigue increased in finishers (PRE vs. POST, p < 0.05) and non-finishers (PRE vs. D1, p < 0.05). In non-finishers, depressive mood correlated positively with leptin, anger, and confusion at several time points (p < 0.001). In finishers, NPY correlated with TQR at PRE (p < 0.05), while leptin correlated negatively with TQR at POST (p < 0.05). Tension-anxiety correlated highly with perceived exertion in non-finishers (p < 0.001) and with cortisol in finishers (p < 0.05) and non-finishers (p < 0.001). In finishers, confusion correlated negatively with NPY (p < 0.01). Conclusion: The study reveals an essential interplay between hormones and mood states affecting performance: Leptin was associated with anger and a depressive mood state in non-finishers and worse recovery in finishers. In contrast, NPY appeared linked to a lower confusion score and heightened recovery in finishers. A simultaneous increase in depressed mood, anger, tension-anxiety, and confusion might harm performance and lead to race failure.

Essential amino acid enriched meal replacement improves body composition and physical function in obese older adults: A randomized controlled trial.

BACKGROUND: Older adults are threatened by the risk of muscle atrophy and excess accumulation of adipose tissue. The objective of this study was to determine whether an essential amino acid enriched meal replacement would reduce excess fat and foster skeletal muscle retention, potentially improving physical function in this cohort. METHODS: Using a double blind, randomized controlled trial, we compared the influence of an experimental meal replacement enriched with essential amino acids (EMR) to a commercially available, widely used meal replacement (Optifast®) provided once/day (q.d.) for four weeks on body composition, skeletal muscle and physical function in obese older participants. Twenty-eight individuals completed either EMR (n = 13) or Optifast® (n = 15) supplementation protocols. Measurements of body composition, thigh skeletal muscle cross-sectional area (CSA), blood panels, intrahepatic lipid, and physical function were completed pre- and post-supplementation. RESULTS: Body fat mass, visceral fat mass and volume, and intrahepatic lipid were reduced with EMR but not with Optifast®. Thigh muscle CSA increased (Δ 2.4 ± 3.0 cm2) with EMR but not Optifast® (Δ -1.8 ± 6.0 cm2). There was a significant increase in the distance covered during the 6-min walk test with EMR (Δ 23 ± 27 m) but no change in Optifast® (Δ 11 ± 37 m). CONCLUSIONS: Beneficial alterations in fat and muscle support the use of EMR-based meal replacements in obese older adults. CLINICAL TRIAL REGISTRATION: ISRCTN registry under Reference Number ISRCTN15814848.

Influences on glycocalyx shedding during the Yukon Arctic Ultra: the longest and the coldest ultramarathon.

The endothelial glycocalyx maintains vascular structure and may be subject to shedding during inflammation and also during high-intensive exercise. There are no studies on shedding during ultra-endurance exercise. The "Yukon Arctic Ultra" (YAU) is one of the longest and coldest ultramarathons and its impact on glycocalyx shedding was investigated. Thirteen adults (38.92 ± 8.67 yr, 6 females) of YAU editions 2015-2019 completed 657.03 ± 71.65 km at a moving velocity of 4.17 ± 0.62 km/h. Mean daily temperatures ranged from -12.6°C to -30.5°C. Glycocalyx elements heparan sulfate, hyaluronan, and syndecan CD-138 were quantified from serum at start, 277 km, 383 km, and 690 km. Cortisol, C-reactive protein, creatine kinase, and N-terminal-prohormone of brain natriuretic peptide were also quantified. Seven YAU volunteers (36.14 ± 11.04 yr, 5 females) served as control. There were no time-changes among the control. Among finishers, there was a significant increase for hyaluronan and a significant decrease for syndecan CD-138. Values were greater among female finishers for heparan sulfate at start, 383 km, and 690 km, and among male finishers for hyaluronan at 277 km. Values for syndecan CD-138 were greater among older finishers at all timepoints. There were weak significant correlations (R2 < 0.215) between hyaluronan and distance, creatine kinase, and NT-Pro BNP, respectively. Shedding of glycocalyx elements is shown among participants of the YAU. Greater shedding of heparan sulfate among female, greater increases of hyaluronan among male, and greater shedding of syndecan CD-138 among older athletes indicate complex glycocalyx shedding during ultra-endurance exercise.NEW & NOTEWORTHY This is the first study to investigate changes in glycocalyx elements in an endurance footrace and first study to investigate exercise-induced shedding in both sexes. This study comprised of an athlete group who finished the ultra-long distance of up to 690 km during the Yukon Arctic Ultra as well as a control group. Results indicate relevant and different shedding of glycocalyx elements heparan sulfate, hyaluronan, and syndecan CD-138. Sex, age, BMI, and covered distance appear to have an influence on the shedding. Other serum parameters indicative of stress appear to be associated with shedding.

Deterioration of Lipid Metabolism Despite Fitness Improvements in Wildland Firefighters.

OBJECTIVE: Determine serum lipid and general health/fitness alterations following a 5-month wildfire suppression season. METHODS: We recruited 100 wildland firefighters (WLFFs) to a 5-month pre- to post-season observational study. Nude body mass, blood pressure (BP), grip strength, and steptest heart rate (HR) were recorded. Blood samples were collected for lipid panel analysis (total cholesterol, high density lipoproteins (HDL)-cholesterol, low density lipoproteins-cholesterol, very low density lipoproteinscholesterol, triglycerides, triglyceride:HDL-cholesterol ratio). Two-tailed dependent t tests determined statistical significance (P < 0.05). RESULTS: There were pre- to post-season changes in nude body mass (+2 ±â€Š4%, P  = 0.001), systolic BP (-2 ±â€Š10%, P  = 0.01), step-test HR (-5 ±â€Š10%, P  < 0.001), and all serum lipids (total cholesterol: +5 ±â€Š14%, P  = 0.02, HDL-cholesterol: = 1 ±â€Š17%, P  = 0.04, low density lipoproteins-cholesterol: +8 ±â€Š22%, P  = 0.02, very low density lipoproteins-cholesterol: +31 ±â€Š49%, P  < 0.001, triglycerides: +30 ±â€Š49%, P  < 0.001, triglyceride:HDL-cholesterol ratio: +37 ±â€Š58%, P  < 0.001). Pre- to post-season diastolic BP (P = 0.12) and grip strength (P = 0.60) remained stable. CONCLUSIONS: WLFFs demonstrate maladaptive serum lipids and body mass alterations despite subtle aerobic fitness improvements.

Equivalent servings of free-range reindeer promote greater net protein balance compared to commercial beef.

Wild game consumption has been associated with health benefits but the acute influence on human protein metabolism remains unknown. We compared feeding-induced responses of equivalent amounts of free-range reindeer (FR) and commercial beef (CB) on protein kinetics using stable isotope methodology. Seven participants (age: 40 ± 14 years; body mass index: 24 ± 3 kg/m2) completed two randomised studies, ingesting 2 oz of FR or CB. L-[ring 2H5]phenylalanine & L-[ring 2H2]tyrosine were delivered via primed, continuous intravenous infusion. Blood samples were collected during the basal period and following consumption of FR or CB. Feeding-induced changes in whole-body protein synthesis (PS), protein breakdown (PB), and net protein balance (NB) were determined via plasma sample isotope enrichment analysis by gas chromatography-mass spectrometry; plasma essential amino acid (EAA) concentrations were determined by liquid chromatography-electrospray ionisation-mass spectrometry. Plasma post-prandial EAA concentrations were higher with FR compared to CB (P < 0.05). The acute feeding-induced PS response was not different, but PB was reduced and contributed to a superior level of NB (P < 0.00001) in FR compared to CB. Our results demonstrate that FR may influence more favourable protein metabolism than CB. These data support potential health benefits of wild game onf whole-body protein.Abbreviations: BMI: body mass index; DIAAS: digestible indispensable amino acid score; CB: commercial beef; EAA: essential amino acids; FR: free-range reindeer; Ra: rate of appearance; UAF: University of Alaska Fairbanks; USDA: USA Department of Agriculture.

Alaska backcountry expeditionary hunting promotes rapid improvements in metabolic biomarkers in healthy males and females.

We have previously reported negative energy balance and health benefits during an Alaska backcountry expeditionary hunting (ABEH) immersion in two males. The purpose of our present study was to increase the number of participants, include females, and evaluate macronutrient intake and serum lipids. Four men (age: 46 ± 6 year, BMI: 26 ± 1 kg/m2 ) and three women (age: 46 ± 11 year, BMI: 25 ± 3 kg/m2 ) were recruited. Doubly labeled water methodology and dietary recall were utilized to assess energy expenditure and energy intake, respectively. Data were collected during pre- and post-ABEH visits. Body composition was measured using dual-energy x-ray absorptiometry and the cross-sectional area of skeletal muscle in the upper leg (XT), and intrahepatic lipid (IHL) was determined using magnetic resonance imaging and/or spectroscopy (MRI/MRS). Blood parameters were measured by LabCorp. Paired T-tests were used for statistical analysis. Data are reported as mean ± SD and considered significant at p < 0.05. Total energy intake was 7.7 ± 3.4 MJ/day and total energy expenditure was 17.4 ± 2.6 MJ/day, resulting in a negative energy balance of -9.7 ± 3.4 MJ/day. Protein intake(grams)/body weight(kilograms)/day was 1.0 ± 0.4. There were reductions in body weight (Δ-1.5 ± 0.7 kg), BMI (Δ-0.3 ± 0.2 kg/m2 ), fat mass (Δ-1.7 ± 0.9 kg), and IHL (Δ-0.3 ± 0.3% water peak). There were no changes in lean tissue mass (Δ0.6 ± 1.4 kg) or XT (Δ-1.3 ± 3.3 cm2 ). There were significant reductions in total cholesterol (Δ-44 ± 35 mg/dl), LDL-cholesterol (Δ-25 ± 14 mg/dl), VLDL-cholesterol (Δ-7 ± 7 mg/dl), and triglycerides (Δ-35 ± 33 mg/dl). The ABEH immersion resulted in considerable negative energy balance and provided comprehensive benefits in metabolic health without any reduction in skeletal muscle.

Nitrogen recycling buffers against ammonia toxicity from skeletal muscle breakdown in hibernating arctic ground squirrels.

Hibernation is a state of extraordinary metabolic plasticity. The pathways of amino acid metabolism as they relate to nitrogen homeostasis in hibernating mammals in vivo are unknown. Here we show, using pulse isotopic tracing, evidence of increased myofibrillar (skeletal muscle) protein breakdown and suppressed whole-body production of metabolites in vivo throughout deep torpor. As whole-body production of metabolites is suppressed, amino acids with nitrogenous side chains accumulate during torpor, while urea cycle intermediates do not. Using 15N stable isotope methodology in arctic ground squirrels (Urocitellus parryii), we provide evidence that free nitrogen is buffered and recycled into essential amino acids, non-essential amino acids and the gamma-glutamyl system during the inter-bout arousal period of hibernation. In the absence of nutrient intake or physical activity, our data illustrate the orchestration of metabolic pathways that sustain the provision of essential and non-essential amino acids and prevent ammonia toxicity during hibernation.

Feasibility of connecting regional research programs to national multisite trials emanating from the CTSA Trial Innovation Network.

A collaborative research model was developed and tested to enable regional healthcare systems to join multisite clinical trials emanating from the Clinical and Translational Science Award (CTSA) Trial Innovation Network (TIN) by the Institute of Translational Health Sciences at the University of Washington and the Northwest Participant and Clinical Interactions (NW PCI) Network. The NW PCI is a collaborative group of regional research programs located at medical centers, healthcare systems, and universities across Washington, Wyoming, Alaska, Montana, and Idaho. This article describes the purpose, development, barriers, and initial experience with feasibility assessment for TIN-supported studies in the NW PCI. The tools and processes of the NW PCI Network were adapted to enable network sites to assess studies for clinical relevance and feasibility. Seven of seventeen TIN-supported studies were reviewed for consideration; three of which resulted in successful completion of study documentation for site selection by NW PCI sites. The NW PCI/TIN model can be adapted by other CTSAs to increase involvement of regional research programs in national multisite clinical research studies. Barriers to expanding TIN-supported trials to regional networks include short timelines for study document submissions, insufficient site reimbursement rates, and non-feasible study designs.

Essential Amino Acid Supplement Lowers Intrahepatic Lipid despite Excess Alcohol Consumption.

Excess alcohol consumption is a top risk factor for death and disability. Fatty liver will likely develop and the risk of liver disease increases. We have previously demonstrated that an essential amino acid supplement (EAAS) improved protein synthesis and reduced intrahepatic lipid in the elderly. The purpose of this exploratory pilot study was to initiate the evaluation of EAAS on intrahepatic lipid (IHL), body composition, and blood lipids in individuals with mild to moderate alcohol use disorder (AUD). Following consent, determination of eligibility, and medical screening, 25 participants (18 males at 38 ± 15 years/age and 7 females at 34 ± 18 years/age) were enrolled and randomly assigned to one of two dosages: a low dose (LD: 8 g of EAAS twice/day (BID)) or high dose (HD: 13 g of EAAS BID). Five of the twenty-five enrolled participants dropped out of the intervention. Both groups consumed the supplement BID for 4 weeks. Pre- and post-EAAS administration, IHL was determined using magnetic resonance imaging/spectroscopy, body composition was analyzed using dual-energy X-ray absorptiometry, and blood parameters were measured by LabCorp. T-tests were used for statistical analysis and considered significant at p < 0.05. While there was no significant change in IHL in the LD group, there was a significant 23% reduction in IHL in the HD group (p = 0.02). Fat mass, lean tissue mass, bone mineral content, and blood lipids were not altered. Post-EAAS phosphatidylethanol was elevated and remained unchanged in LD at 407 ± 141 ng/mL and HD at 429 ± 196 ng/mL, indicating chronic and excess alcohol consumption. The HD of the proprietary EAAS formulation consumed BID seemed to lower IHL in individuals with mild to moderate AUD. We suggest that further studies in a larger cohort be conducted to more completely address this important area of investigation.

Essential amino acid-enriched meal replacement promotes superior net protein balance in older, overweight adults.

BACKGROUND & AIMS: Older individuals are susceptible to the loss of muscle and accumulation of fat. To address this problem, we have compared protein kinetics following consumption of an essential amino acid (EAA)-enriched meal replacement (EMR) to consumption of a high-protein meal replacement beverage (Bariatric Advantage, BA) using stable isotope methodology. METHODS: Eight older (67 ± 2), obese (35 ± 2 kg/m2) female and male participants completed two studies using a randomized, crossover design in which they ingested each meal replacement. The isotopic tracers L-[2H5]phenylalanine & L-[2H2]tyrosine were delivered via primed, continuous intravenous infusion throughout a basal period and following consumption of EMR or BA. We determined changes in whole body protein synthesis (PS), protein breakdown (PB), and net protein balance (NB) from fasted states via analysis of plasma samples by LC-ESI-MS. RESULTS: PS was higher (P = 0.03) and PB was less (P = 0.005) with EMR in comparison to BA. As a result, NB was much greater (P = 0.00003) following the ingestion of EMR as compared to BA. CONCLUSIONS: In comparison with BA, which has a higher amount of intact protein that any other meal replacement, EMR promoted a greater increment in NB. These data support the potential efficacy of EMR as a meal replacement for the preservation of lean tissue mass during weight loss in older, overweight individuals.

Wildland Firefighting: Adverse Influence on Indices of Metabolic and Cardiovascular Health.

OBJECTIVE: The purpose of this study was to evaluate pre- and postseason measures of body composition, skeletal muscle, and blood parameters/liver lipid in wildland firefighters (WLFF) over the fire season. METHODS: Alaskan WLFF (N = 27) crews were evaluated pre- and postwildfire season, which included 63 ±â€Š10 operational days. Body composition, thigh muscle area, and liver lipid were quantified using dual-energy radiograph absorptiometry and magnetic resonance imaging, respectively. Blood metabolic and lipid panels were also collected and analyzed. RESULTS: Total body, fat, and visceral fat mass increased from pre- to postseason (P < 0.05). Total cholesterol, LDL, and total globulin also increased (P < 0.05). There was a trend (P = 0.06) towards an increase in intrahepatic lipid. CONCLUSIONS: The observed maladaptive changes in adipose tissue, blood lipids, and hepatic function may reflect adaptations/consequences to occupational demands/conditions and warrant evaluation of appropriate countermeasures.

The energy requirements and metabolic benefits of wilderness hunting in Alaska.

The purported healthy aspects of subsistence foods have led to the popularity of the Paleo diet. There has been very little focus, surprisingly, on health benefits derived from the nomadic nature of humans during the Paleolithic era. The purpose of our study was to examine total energy expenditure (TEE), total energy intake (TEI), body composition, blood lipids, and intrahepatic lipid in humans during a 12-day Alaskan backcountry expeditionary hunting (ABEH) immersion. Four healthy men (age: 42 ± 3 year, BMI: 27 ± 1 kg/m2 ) were recruited for the study. TEE was measured using the doubly labeled water method and a food diary was utilized to assess TEI. Body composition was measured using dual energy X-ray absorptiometry (DXA); cross-sectional area of the thigh (XT) and intrahepatic lipid (IHL) were measured using molecular imaging. Blood samples were collected for the measurement of blood lipids. DXA, XT, IHL, and blood data were collected pre- and immediately post-ABEH. Results were analyzed using paired t-tests and considered significant at P < 0.05. TEE and TEI averaged 18.1 ± 1.2 and 9.1 ± 2.5 MJ/day, respectively, indicating substantial negative energy balance (-9.0 ± 1.3 MJ/day). There was a reduction in percent body fat (∆-3.3 ± 0.2%), total fat mass (∆-3.3 ± 0.4 kg), and visceral fat volume (Δ-261 ± 188 cm3 ). Lean tissue mass and XT was unchanged. There was a decrease in IHL (Δ-0.5 ± 0.1% water peak), and a trend (P = 0.055) toward reduction in LDL-cholesterol. We conclude that constancy of physical activity during negative energy balance may provide metabolic benefits above and beyond variations in diet that exist with the hunter-gatherer lifestyle.

Alaska Mountain Wilderness Ski Classic: Alterations in Caloric Expenditure and Body Composition.

INTRODUCTION: The Alaska Mountain Wilderness Ski Classic is a self-supported ultramarathon cross-country skiing event that traverses one of the mountain ranges of Alaska each winter. Unique aspects of this event challenge athletes with a significant amount of physical and mental stress while in the chronically cold conditions of the Arctic. Assessment of energy requirements or body composition has never been performed during this event. The objective of the study was to evaluate the influence of the 2016 Alaska Mountain Wilderness Ski Classic on caloric expenditure and body composition. METHODS: Caloric expenditure was estimated using GT3x+ Actigraph accelerometers and ActiLife software. Lean tissue mass, total fat mass, visceral fat mass, and bone mineral density were measured using a General Electric iDXA before and after the event. Data are presented as mean±SD. Differences were analyzed using paired t tests with significance at P<0.05. RESULTS: Fifteen participants (age=32.7±6.6 years, body mass index=23.7±2.3 kg·m2) completed the study, 8 males and 7 females. Caloric expenditure was 6238±1390 kcal·day-1, and 37,163±8425 kcal for the entire event. Fat mass was reduced from pre-event (∆1.3±0.7 kg, P=0.00003). There was an increase in lean tissue mass (∆1.7±1.3 kg, P=0.0003) and relative skeletal muscle index (∆0.2±0.2 kg·m², P=0.001). There was no change in bone mineral density (∆0±0 g·cm3, P=0.4). CONCLUSIONS: Despite the metabolic demands, fat mass was reduced and lean tissue mass was preserved. Future studies of this event should be directed toward assessment of the nutritional provisions utilized and the mechanisms responsible for the preservation of lean tissue mass.

Cardiac Autonomic Modulations and Psychological Correlates in the Yukon Arctic Ultra: The Longest and the Coldest Ultramarathon.

Studies on human physical performance in extreme environments have effectively approached the investigation of adaptation mechanisms and their physiological limits. As scientific interest in the interplay between physiological and psychological aspects of performance is growing, we aimed to investigate cardiac autonomic control, by means of heart rate variability, and psychological correlates, in competitors of a subarctic ultramarathon, taking place over a 690 km course (temperatures between +5 and -47°C). At baseline (PRE), after 277 km (D1), 383 km (D2), and post-race (POST, 690 km), heart rate (HR) recordings (supine, 15 min), psychometric measurements (Profile of Mood States/POMS, Borg fatigue, and Karolinska Sleepiness Scale scores both upon arrival and departure) were obtained in 16 competitors (12 men, 4 women, 38.6 ± 9.5 years). As not all participants reached the finish line, comparison of finishers (FIN, n = 10) and non-finishers (NON, n = 6), allowed differential assessment of performance. Resting HR increased overall significantly at D1 (FIN +15.9; NON +14.0 bpm), due to a significant decrease in parasympathetic drive. This decrease was in FIN only partially recovered toward POST. In FIN only, baseline HR was negatively correlated with mean velocity [r -0.63 (P.04)] and parasympathetic drive [pNN50+: r -0.67 (P.03)], a lower HR and a higher vagal tone predicting a better performance. Moreover, in FIN, a persistent increase of the long-term self-similarity coefficient, assessed by detrended fluctuation analysis (DFAα2), was retrieved, possibly due to higher alertness. As for psychometrics, at D1, POMS Vigor decreased (FIN: -7.0; NON: -3.8), while Fatigue augmented (FIN: +6.9; NON: +5.0). Sleepiness increased only in NON, while Borg scales did not exhibit changes. Baseline comparison of mood states with normative data for athletes displayed significantly higher positive mood in our athletes. Results show that: the race conditions induced early decreases in parasympathetic drive; the extent of vagal withdrawal, associated to the timing of its recovery, is crucial for success; pre-competition lower resting HR predicts a better performance; psychological profile is reliably depicted by POMS, but not by Borg fatigue scales. Therefore, assessment of heart rate variability and psychological profile may monitor and partly predict performance in long-duration ultramarathon in extreme cold environment.

Negative Energy Balance Does Not Alter Fat-Free Mass During the Yukon Arctic Ultra-The Longest and the Coldest Ultramarathon.

Purpose: The objective of this study was to determine alterations in caloric balance, body composition, metabolites, and cytokines in athletes participating in the Yukon Arctic Ultra. Methods: Ten participants traveling on foot in the 2017 692-km event were recruited for the study. Measurements and samples were obtained at pre-event, 278 km (C1), 384 km (C2), and post-event. Body composition measurements were obtained using bioelectrical impedance analysis. Accelerometer devices were utilized to provide an estimation of caloric expenditure and dietary recalls provided assessments of caloric intake. Blood serum samples were collected, processed, and analyzed using enzyme-linked immunosorbent assays or nuclear magnetic resonance. Results were analyzed using linear mixed model, presented as means ± SD, and considered significant at p < 0.05. Results: Participants (8 males, 2 females; age: 37 ± 10 years; body mass index: 24.4 ± 2.5 kg/m2) were recruited. Four males and one female completed the entire event in 260 ± 19 h. Caloric intake/expenditure was 4,126 ± 1,115 kcal/day and 6,387 ± 781 kcal/day, respectively, indicating a caloric deficit of 2,261 ± 1,543 kcal/day. Total mass, body mass index, and fat mass were reduced at each time point of the event. Fat-free mass (FFM) was unchanged throughout the event. Follistatin was increased at C1 (1,715 ± 876 pg/ml) in comparison to baseline. Acetoacetate increased significantly at post-event (6.1 ± 1.5 mg/ml). Conclusions: Despite a pronounced caloric deficit and sustained activity under extreme cold conditions, FFM was preserved with an increase in serum follistatin and acetoacetate. Future studies should be directed at the role of nutrient strategies and/or training methods on the retention of FFM under these conditions.

Weight Loss Strategies in the Elderly: A Clinical Conundrum.

The age-related concomitant loss of skeletal muscle and accumulation of excess adipose tissue have been commonly referred to as sarcopenic obesity. While weight loss may help mitigate the metabolic abnormalities linked to obesity, low fitness levels and muscle atrophy complicate the effectiveness of lifestyle interventions. Because of low levels of compliance, suboptimal economic efficiency, and low functional capacity, there has been no consensus on optimal therapy. This includes the use of high-protein diets that do not ensure muscle preservation during weight loss in this segment of the population. The primary objectives of this review are to discuss the relevance of sarcopenic obesity, examine the feasibility of weight loss in the elderly, and highlight new approaches to the problem.