Cold habituation does not improve manual dexterity during rest and exercise in 5 °C.

When exposed to a cold environment, a barehanded person experiences pain, cold sensation, and reduced manual dexterity. Both acute (e.g. exercise) and chronic (e.g. cold acclimatization or habituation) processes might lessen these negative effects. The purpose of this experiment was to determine the effect of cold habituation on physiology, perception, and manual dexterity during rest, exercise, and recovery in 5 °C. Six cold weather athletes (CWA) and eight non habituated men (NON) volunteered to participate in a repeated measures cross-over design. The protocol was conducted in 5 °C and was 90 min of resting cold exposure, 30 min of cycle ergometry exercise (50 % VO2 peak), and 60 min of seated recovery. Core and finger skin temperature, metabolic rate, Purdue Pegboard dexterity performance, hand pain, thermal sensation, and mood were quantified. Exercise-induced finger rewarming (EIFRW) was calculated for each hand. During 90 min of resting exposure to 5 °C, the CWA had a smaller reduction in finger temperature, a lower metabolic rate, less hand pain, and less negative mood. Despite this cold habituation, dexterity performance was not different between groups. In response to cycle ergometry, EIFRW was greater in CWA (~12 versus 7 °C) and occurred at lower core temperatures (37.02 versus 37.31 °C) relative to NON but dexterity was not greater during post-exercise recovery. The current data indicate that cold habituated men (i.e., CWA) do not perform better on the Purdue Pegboard during acute cold exposure. Furthermore, despite augmented EIFRW in CWA, dexterity during post-exercise recovery was similar between groups.

Caffeine gum and cycling performance: a timing study.

The purpose of this study was to determine the most efficacious time to administer caffeine (CAF) in chewing gum to enhance cycling performance. Eight male cyclists participated in 5 separate laboratory sessions. During the first visit, the subjects underwent a graded exercise test to determine maximal oxygen consumption (V[Combining Dot Above]O(2)max). During the next 4 visits, 3 pieces of chewing gum were administered at 3 time points (120-minute precycling, 60-minute precycling, and 5-minute precycling). In 3 of the 4 visits, at 1 of the time points mentioned previously, 300 mg of CAF was administered. During the fourth visit, placebo gum was administered at all 3 time points. The experimental trials were defined as follows: trial A (-120), trial B (-60), trial C (-5), and trial D (Placebo). After baseline measurements, time allotted for gum administration, and a standard warm-up, the participants cycled at 75% V[Combining Dot Above]O(2)max for 15 minutes then completed a 7-kJ·kg(-1) cycling time trial. Data were analyzed using a repeated measures analysis of variance. Cycling performance was improved in trial C (-5), but not in trial A (-120) or trial B (-60), relative to trial D (Placebo). CAF administered in chewing gum enhanced cycling performance when administered immediately prior, but not when administered 1 or 2 hours before cycling.

Cognitive function during lower body water immersion and post-immersion afterdrop.

INTRODUCTION: The physiological effects of immersion hypothermia and afterdrop are well-characterized, but the psychological effects are less clear. The purpose of this study was to quantify changes in cognitive function during and after lower body water immersion. METHODS: On separate mornings, nine young healthy men participated in both neutral (35 +/- 1 degree C) and cold (13 +/- 1 degree C) water immersion. Subjects rested in neutral air for 30 min followed by 60 min water immersion to the iliac crest and 15 min of recovery in neutral air. Rectal temperature and mean skin temperature were continuously monitored. Metabolic rate, the Stroop Color Word Test (SCWT), and the Profile of Mood State (POMS) were quantified at predetermined intervals. RESULTS: During immersion in cold water, rectal temperature was reduced, but SCWT and POMS scores were unchanged relative to baseline. Despite the reduced rectal temperature, little to no shivering was observed during immersion and metabolic rate did not change. During recovery from cold immersion, rectal temperature was further reduced by approximately 0.5 degree C, shivering was noted, and metabolic rate increased. Coincident with this acute afterdrop, SCWT Color-Word performance (delta = -4 +/- 8 vs. 7 +/- 6 correct responses) and Interference score (delta = -2 +/- 7 vs. 4 +/- 8) was impaired relative to recovery from neutral immersion (i.e., when core temperature and metabolic rate did not change). CONCLUSION: These results suggest that recovery from lower body cold water immersion elicits the afterdrop phenomenon and shivering, which together impair selective attention as measured by the SCWT.

Effect of cold acclimatization on exercise economy in the cold.

We sought to determine if cold acclimatized men display higher economy (i.e. lower oxygen consumption at a given workload) during graded cycle ergometry in the cold (5°C). After completing a familiarization trial 1 week prior, five cold weather athletes (CWA) and eight physically active men (NON) underwent graded exercise tests to volitional fatigue in 5°C. The protocol always started at 60 W and increased by 20 W each minute. Oxygen consumption (VO(2)), respiration rate (RR), tidal volume (TV), and respiratory exchange ratio (RER) were determined via open circuit spirometry. Individuals were matched for body size and minutes of weekly physical activity. Repeated measures analyses of variance were conducted across time (workload) and cold acclimatization was entered as a between subjects factor. VO(2) peak was not different between groups but CWA had lower VO(2) at 60 and 240 W. CWA also had lower RR at 180 and 260 W as well as lower RER at 240 and 260 W. At submaximal workloads, cold acclimatized men have higher exercise economy than non-acclimatized men. This could have implications for those who work in this context.

Low-dose caffeine administered in chewing gum does not enhance cycling to exhaustion.

Low-dose caffeine administered in chewing gum does not enhance cycling to exhaustion. The purpose of the current investigation was to examine the effect of low-dose caffeine (CAF) administered in chewing gum at 3 different time points during submaximal cycling exercise to exhaustion. Eight college-aged (26 ± 4 years), physically active (45.5 ± 5.7 ml·kg(-1)·min(-1)) volunteers participated in 4 experimental trials. Two pieces of caffeinated chewing gum (100 mg per piece, total quantity of 200 mg) were administered in a double-blind manner at 1 of 3 time points (-35, -5, and +15 minutes) with placebo at the other 2 points and at all 3 points in the control trial. The participants cycled at 85% of maximal oxygen consumption until volitional fatigue and time to exhaustion (TTE) were recorded in minutes. Venous blood samples were obtained at -40, -10, and immediately postexercise and analyzed for serum-free fatty acid and plasma catecholamine concentrations. Oxygen consumption, respiratory exchange ratio, heart rate, glucose, lactate, ratings of perceived exertion, and perceived leg pain measures were obtained at baseline and every 10 minutes during cycling. The results showed that there were no significant differences between the trials for any of the parameters measured including TTE. These findings suggest that low-dose CAF administered in chewing gum has no effect on TTE during cycling in recreational athletes and is, therefore, not recommended.

Hemodynamic and thermoregulatory responses to lower body water immersion.

INTRODUCTION: Lower body water immersion (LBWI) is experienced in the marine industry but the physiological responses to LBWI are unclear. The purpose of the current experiment was to test the effects of water temperature and immersion duration on rectal temperature, heart rate, stroke volume, blood pressure, metabolic rate, and thermal sensation in healthy subjects. METHODS: Nine young men underwent two 60-min trials of seated LBWI to the iliac crest in a counterbalanced fashion. On one occasion, the water was 35 degrees C (LBWI-Neutral) and on the other it was 13 degrees C (LBWI-Cold); the upper body remained thermoneutral and dry throughout. RESULTS: As expected, exposure to cold water reduced mean skin temperature and individuals reported cold thermal sensation. Mean arterial pressure was significantly higher at 60 min of LBWI-Cold (86 +/- 7 mmHg) compared to LBWI-Neutral (76 +/- 5 mmHg) while heart rate tended to be lower. The change in rectal temperature from baseline to 30 min of LBWI-Cold (delta = -0.01 +/- 0.21degrees C) was significantly smaller than the change in T(re) from 30 to 60 min of LBWI-Cold (delta = -0.46 +/- 0.16 degrees C). Despite this accelerated drop in core temperature during minutes 30-60, metabolic rate did not increase significantly. CONCLUSION: LBWI-Cold reduces core temperature and increases arterial blood pressure via an increase in total peripheral resistance. This experimental model may help scientists better understand the body during cold stress. Further, people who are occupationally exposed to cold water (when the torso, hands, and arms remain thermoneutral) may be at increased risk for hypothermia.

The Relationship between the Frequency and Duration of Physical Activity and Depression in Older Adults with Multiple Chronic Diseases.

Research has demonstrated that older adults with multiple chronic diseases (CD) are particularly vulnerable to depression. Meeting current recommendations for physical activity (PA) may help ameliorate the impact of depression on this population. Nonetheless, the impact of frequency versus duration of PA on depression in older adults remains to be explored. Therefore, the purpose of the present study was to determine the combined effect of PA and multiple CD on depression and the combined effect of the frequency, duration, and multiple CD on depression in older adults. Methods: The present study utilized data from the 2017 and 2020 Living Profiles of Older People Surveys. Data from a total of 19,907 older adults (10,042 older adults from 2017 and 9865 older adults from 2020) were included in the present study. Depression was assessed using the Korean version of the Short Form of Geriatric Depression Scale (K-SGDS) and CD included cardiovascular disease, respiratory diseases, thyroid syndromes, orthopedic complications, and diabetes. Participants who participated in PA ≥ 150 min/week were categorized as the high PA group, and those who participated in PA < 150 min/week were categorized as the low PA group. Furthermore, the frequency of PA (FRE) was divided into high FRE (≥5 times/week) and low FRE (<5 times/week), and duration (DUR) was divided into DUR30 (≥30 min/bout) and DUR0 (<30 min/bout). Results: The high PA group exhibited a lower risk of depression relative to the low PA group (p < 0.001). Furthermore, the risk of depression was consistently lower at DUR30 than DUR0 regardless of FRE in all CD categories and this result was maintained after adjusting for age, gender, BMI, height, weight, income, education levels, smoking status, and cognitive function. Conclusion: These results interestingly demonstrated that it is important for older adults to participate in a longer duration of PA to impact and prevent depression symptoms regardless of FRE.

Effects of Low Dose Caffeine on Post-Exercise Heart Rate Variability: A Double-Blind Placebo-Controlled Trial.

Caffeine may impact post-exercise heart rate variability (HRV); although, studies have yielded inconsistent findings. We examined the effects of low dose caffeine on post-exercise HRV. Healthy, college-aged adults [n = 18; age: 22.1 ± 2.6 years; BMI: 26.9 ± 4.3 kg/m2; estimated maximal oxygen consumption (VO2max): 45.1 ± 8.3 ml·kg-1·min-1] participated in a repeated-measures, double-blind, placebo-controlled trial. During the experimental trials, participants were fitted with a heart rate monitor and a mouthpiece with a one-way nonrebreathing valve and then rested for 10 min during baseline HRV and expired gas assessments. Participants chewed either caffeine (~170mg) or placebo gum for 5 min. Following expectoration and a 5 min warmup, participants walked on a treadmill for 20 min at 60% of estimated VO2max and then rested for 30 min. HRV indices were calculated from 10 min measurements during baseline and post-exercise (post 1, 2, and 3). A main effect of treatment was found for standard deviation of RR intervals (SDNN), absolute power of low frequency band (LF), absolute power of high frequency band (HF), and the standard deviation perpendicular to the line-of-identity in Poincaré plot (SD1) (p < 0.05). Further, a trend for higher root mean square of successive RR interval differences (RMSSD) with caffeine was observed (p = 0.066). Post hoc t-tests revealed that post-exercise SDNN, LF, HF, and SD1 were higher with caffeine compared to placebo (p ≤ 0.012). Results demonstrated that low dose caffeine did not delay the recovery of HRV indices reflective of parasympathetic nervous system activity following an acute bout of moderate exercise.

Mood and selective attention in the cold: the effect of interval versus continuous exercise.

Both mood and cognitive function are altered in cold environments. Body warming through exercise may improve Stroop interference score and lessen total negative mood. The purpose of this study was to determine the effect of equal caloric bouts of interval (INT) and continuous (CONT) exercise on mood and selective attention in the cold. Eleven young men underwent two experimental trials in 5°C air. Both trials consisted of 90 min acute cold exposure (ACE), 30 min exercise (INT vs. CONT), and 60 min recovery (REC). The Profile of Mood States (POMS) and Stroop Color Word Test (SCWT) were administered at four time points. Mean body temperature decreased during ACE, increased during exercise, and decreased during REC. Repeated measures analysis of variance revealed a main effect for time for several of the POMS sub scores. In particular, negative mood was significantly decreased after exercise relative to ACE and then significantly increased during REC. Further, CONT appears to be more effective than INT at decreasing negative mood. Components of the SCWT supported both the arousal and distraction theories for simple perception, but no significant effects were shown for the interference score. In the cold, exercise decreases negative mood but does not appear to affect selective attention. Further mechanistic studies could determine the best mode and intensity of exercise for improving cognitive function in the cold.

Pain and thermal sensation in the cold: the effect of interval versus continuous exercise.

Military and factory work often involves exposure to cold temperatures. With prolonged exposure, individuals report feeling cold and develop pain in their hands, both of which might be alleviated by endogenous heat production via exercise. The purpose of this study was to evaluate how interval (INT) and continuous (CONT) cycle ergometry alter thermal sensation, hand pain, mean finger temperature, and skin surface temperature gradient (forearm-finger) following immobility in moderate cold. Fourteen young men underwent two trials (each was three total hours in 5°C) consisting of a 90-min period of acute cold exposure (ACE), 30 min of exercise (INT or CONT), and a 60-min recovery period (REC). INT and CONT were isoenergetic, reflecting 50 ± 1% of each individual's VO(2) peak. All perceptual scales were significantly correlated during ACE (i.e., test-retest reliability). As expected, individuals felt colder and reported more hand pain during ACE, as compared to thermoneutral conditions. Relative to ACE, both INT and CONT increased mean finger temperature, which was associated with warmer thermal sensation and less hand pain. During REC in 5°C, individuals felt colder and reported more hand pain than during exercise. Although there were no perceptual differences between INT and CONT, moderate exercise in general can cause subjective feelings of warmth and less hand pain in people acutely exposed to moderate cold.

The effects of combined elastic- and free-weight tension vs. free-weight tension on one-repetition maximum strength in the bench press.

The present study investigated the effects of training combining elastic tension, free weights, and the bench press. Eleven college-aged men (untrained) in the bench press participated in the 13-week study. The participants were first given instructions and then practiced the bench press, followed by a one-repetition maximum (1RM) test of baseline strength. Subjects were then trained in the bench press for 3 weeks to allow for the beginning of neural adaptation. After another 1RM test, participants were assigned to 1 of 2 conditions for the next 3 weeks of training: 85% Free-Weight Tension, 15% Elastic Tension (BAND), or 100% Free-Weight Tension (STAND). After 3 weeks of training and a third 1RM max test, participants switched treatments, under which they completed the final 3 weeks of training and the fourth 1RM test. Analysis via analysis of covariance revealed a significant (p ≤ 0.05) main effect for time and interaction effect for Treatment (BAND vs. STAND). Subsequent analysis via paired-samples t-test revealed the BAND condition was significantly better (p = 0.05) at producing raw gains in 1RM strength. (BAND 9.95 ± 3.7 kg vs. STAND 7.56 ± 2.8 kg). These results suggest that the addition of elastic tension to the bench press may be an effective method of increasing strength.

Test-retest reliability of Purdue Pegboard performance in thermoneutral and cold ambient conditions.

In the cold, Purdue Pegboard (PP) performance declines. The purpose of this study was to determine if this cold-induced impairment is consistent across days (i.e. test-retest reliability) in 5°C. In thermoneutral air (25°C), 14 men were familiarised to the dominant hand (PPa) and bimanual (PPb) PP tasks. They then experienced two 90-min cold exposures (Day 1, Day 2) while wearing ∼1 clo. Bare hands were maintained throughout. Performance on both tasks showed high reliability from day to day (intraclass correlations >0.700) in both thermoneutral and cold conditions. However for both tasks, room temperature performance did not predict performance in the cold (intraclass correlations <0.450). When screening applicants for manual labour in the cold, one must consider that room temperature dexterity does not correlate with dexterity in the cold. It is recommended that a 60-min period of cold exposure be employed to assess manual dexterity in these workers. STATEMENT OF RELEVANCE: This study shows that PP performance in room temperature does not predict performance in the cold but performance in the cold is consistent from day to day. When screening applicants for manual labour in the cold, it is recommended that dexterity tests be conducted in the same ambient conditions.

A Short-Term Paleolithic Dietary Intervention Does Not Alter Adipokines Linked to Adiposity.

The Paleolithic diet, characterized by an emphasis on hunter-gatherer type foods accompanied by an exclusion of grains, dairy products, and highly processed food items, is often promoted for weight loss and a reduction in cardiometabolic disease risk factors. Specific adipokines, such as adiponectin, omentin, nesfatin, and vaspin are reported to be dysregulated with obesity and may respond favorably to diet-induced fat loss. We aimed to evaluate the effects of an eight-week Paleolithic dietary intervention on circulating adiponectin, omentin, nesfatin, and vaspin in a cohort of physically inactive, but otherwise healthy adults. METHODS: Seven inactive adults participated in eight weeks of adherence to the Paleolithic Diet. Fasting blood samples, anthropometric, and body composition data were collected from each participant pre-and post-intervention. Serum adiponectin, omentin, nesfatin, and vaspin were measured. RESULTS: After eight weeks of following the Paleolithic diet, there were reductions (p<0.05) in relative body fat (-4.4%), waist circumference (- 5.9 cm), and sum of skinfolds (-36.8 mm). No changes were observed in waist to hip ratio (WHR), or in adiponectin, omentin, and nesfatin (p>0.05), while serum vaspin levels for all participants were undetectable. CONCLUSIONS: It is possible that although eight weeks resulted in modest body composition changes, short-term fat loss will not induce changes in adiponectin, omentin, and nesfatin in apparently healthy adults. Larger, long-term intervention studies that examine Paleolithic diet-induced changes across sex, body composition, and in populations with metabolic dysregulation are warranted.

Single-Arm 8-Week Ad Libitum Self-Prepared Paleo Diet Reduces Cardiometabolic Disease Risk Factors in Overweight Adults.

The paleo diet is popular among the general population due to promoted weight loss and disease prevention benefits. We examined the effectiveness of a self-administered paleo diet in improving cardiometabolic disease risk factors. Overweight, physically inactive but otherwise healthy adults (males = 4, females = 3, age 32.7 ± 4.9 years, body mass index [BMI] 29.4 ± 2.4 kg/m2) habitually eating a traditional Western diet (1853.4 ± 441.2 kcal; 34.0% carbohydrate; 41.4% fat; 19.2% protein) completed an ad libitum self-administered paleo diet for 8 weeks. Height, weight, blood pressure, and a fasting blood sample were collected pre- and post-paleo dietary intervention. Blood samples were analyzed for fasting cardiometabolic disease biomarkers-including brain-derived neurotropic factor (BDNF), fibroblast growth factor (FGF) 21, and leptin. After 8 weeks, body mass (-5.3 kg, P = .008), BMI (-1.7 kg/m2, P = .002), serum leptin (-56.2%, P = .012), serum FGF21 (-26.7%, P = .002), and serum BDNF (-25.8%, P = .045) significantly decreased. Systolic and diastolic blood pressure were unchanged following the paleo dietary intervention (P > .05). Average energy intake (-412.6 kcal, P = .016) significantly decreased with the paleo dietary intervention mostly due to a reduction in carbohydrate consumption (-69.2 g; P = .003). An 8-week self-administered paleo dietary intervention was effective in improving cardiometabolic disease risk factors in a healthy, physically inactive overweight adult population.

The influence of interval versus continuous exercise on thermoregulation, torso hemodynamics, and finger dexterity in the cold.

The purpose of this study was to evaluate how interval (INT) and continuous (CONT) exercise alter body temperatures and manual dexterity in the cold (5 degrees C). Fourteen young men underwent two trials consisting of a 90-min period of acute cold exposure (ACE), 30 min of exercise (INT or CONT), and a 60-min recovery period (REC). Participants donned approximately 1 clo but the hands remained bare for the entire protocol so that a steep decline in dexterity performance occurred prior to the initiation of exercise. INT and CONT were isoenergetic, reflecting 50 +/- 1% of each individual's VO(2) peak. Rectal (Tre) and skin temperatures were monitored continuously and dexterity testing was conducted at ten time points throughout each 3-h trial. In addition, oxygen consumption (VO(2)) and torso hemodynamics were assessed via indirect calorimetry and impedance cardiography (ICG), respectively. As expected, finger temperature and dexterity declined during ACE, relative to baseline. Both modes of exercise increased finger temperature and dexterity, relative to ACE. However, CONT was more effective than INT at increasing finger temperature on the dominant hand, which was associated with better dexterity scores during REC. Tre was not different between trials but a significant increase in stroke volume was found following CONT. Perhaps elevated stroke volume during post-exercise REC plays a role in finger rewarming and dexterity performance. Further mechanistic studies are needed to confirm the role of cardiovascular function in the enhancement of manual performance in the cold.

Reliability of the measurement of stroke volume using impedance cardiography during acute cold exposure.

INTRODUCTION: It is well documented that cardiovascular alterations occur during acute cold exposure (ACE). Interindividual variability is present, due mainly to body size differences, gender, and age. However, no study has evaluated stroke volume in the same individual twice in the same ambient conditions (i.e., test-retest reliability). Impedance cardiography (ICG) has become a popular method to acquire hemodynamic data in both clinical and applied physiology settings. Further, ICG does not interfere with other dependent variables such as oxygen consumption. Therefore, based on the uniqueness of the methodology, we sought to test reliability in this technology at 5 degrees C for 65 min on two separate occasions. METHODS: Nine young men underwent two 65-min trials of resting ACE, separated by at least 72 h. Volunteers were clothed in approximately one layer of clothing. Core and skin temperatures, oxygen consumption, and central hemodynamics were measured. RESULTS: As expected, core and skin temperature decreased while oxygen consumption showed a modest increase over time. In both trials, stroke volume significantly increased over time as heart rate decreased. There was similarity within subjects and between trials for all variables, as assessed via bivariate correlations. CONCLUSION: Cold increased stroke volume and decreased heart rate when subjects were pooled together, but each subject retained his individuality (minimal interindividual differences). Results suggest that impedance cardiography may be a reliable technique to use during acute cold exposure.

Effects of Nutrition/Diet on Brown Adipose Tissue in Humans: A Systematic Review and Meta-Analysis.

BACKGROUND: Brown adipose tissue (BAT) provides a minor contribution to diet-induced thermogenesis (DIT)-the metabolic response to food consumption. Increased BAT activity is generally considered beneficial for mammalian metabolism and has been associated with favorable health outcomes. The aim of the current systematic review was to explore whether nutritional factors and/or diet affect human BAT activity. METHODS: We searched PubMed Central, Embase and Cochrane Library (trials) to conduct this systematic review (PROSPERO protocol: CRD42018082323). RESULTS: We included 24 eligible papers that studied a total of 2785 participants. We found no mean differences in standardized uptake value of BAT following a single meal or after 6 weeks of L-Arginine supplementation. Resting energy expenditure (REE), however, was increased following a single meal and after supplementation of capsinoid and catechin when compared to a control condition (Z = 2.41, p = 0.02; mean difference = 102.47 (95% CI = 19.28-185.67)). CONCLUSIONS: Human BAT activity was not significantly affected by nutrition/diet. Moreover, REE was only increased in response to a single meal, but it is unlikely that this was due to increased BAT activity. BAT activity assessments in response to the chronic effect of food should be considered along with other factors such as body composition and/or environmental temperature.

Effects of an Exogenous Ketone Supplement on Five-Kilometer Running Performance.

Numerous oral ketone supplements are marketed with the claim that they will rapidly induce ketosis and improve exercise performance. The purpose of this study was to assess exercise performance time and related physiological, metabolic and perceptual responses of recreational endurance runners after ingestion of a commercially available oral ketone supplement. Recreational endurance runners (n = 10; age: 20.8 ± 1.0 years; body mass: 68.9 ± 5.6 kg; height: 175.6 ± 4.9 cm) participated in a double-blind, crossover, repeated-measures study where they were randomized to 300 mg.kg-1 body weight of an oral ß-hydroxybutyrate-salt + Medium Chain Triglyceride (ßHB-salt+MCT) ketone supplement or a flavor matched placebo (PLA) 60 min prior to performing a 5-km running time trial (5KTT) on a treadmill. Time, HR, RPE, affect, RER, VO2, VCO2, and VE were measured during the 5-km run. The Session RPE and affect (Feeling Scale) were obtained post-5KTT. Plasma glucose, lactate and ketones were measured at baseline, 60-min post-supplement, and immediately post-5KTT. Plasma R-ßHB (endogenous isomer) was elevated from baseline and throughout the entire protocol under the ßHB-salt+MCT condition (p < 0.05). No significant difference (58.3 ± 100.40 s; 95% CI: -130.12 - 13.52; p = 0.100) was observed between the ßHB-salt+MCT supplement (1430.0 ± 187.7 s) and the PLA (1488.3 ± 243.8 s) in time to complete the 5KTT. No other differences (p > 0.05) were noted in any of the other physiological, metabolic or perceptual measures.

Catecholamine levels in hypoxia-lnduced acute mountain sickness.

UNLABELLED: Enhanced sympathoadrenal activity has been implicated in the pathogenesis of acute mountain sickness (AMS). This study was designed to examine the time course of circulating catecholamines in individuals with and without AMS. METHODS: Subjects were low-altitude residents (10 men, 8 women) who had not been exposed to altitude within the previous 2 mo. They breathed 12% O2 (hypoxia equivalent to 4600 m altitude) for 8 h while seated at rest. AMS was evaluated using Lake Louise scores (LLS) at 0, 1, 3, 5, and 7 h of exposure using a threshold of 3 to define AMS. Blood samples were collected to measure arterial blood gases and oxygen saturation as well as arterial and venous epinephrine (A-EPI and V-EPI) and norepinephrine (A-NE and V-NE). RESULTS: Eight subjects (44%) developed AMS at some time during the experiment. Blood gases showed no significant difference between subjects with or without symptoms (AMS+ and AMS-, respectively). However, AMS+ subjects showed significantly greater concentrations of A-EPI over the 8 h without any between-group difference in V-EPI. Levels of A-NE were significantly higher at baseline and during the first hour of hypoxia in subjects who later developed AMS. V-NE increased significantly over time among all participants with no difference between groups. CONCLUSIONS: These findings suggest a possible physiological marker for individuals who may be relatively susceptible to AMS and provide additional insight into the sympathoadrenal response to acute hypoxia.

Impact of Genetic Variability on Physiological Responses to Caffeine in Humans: A Systematic Review.

Emerging research has demonstrated that genetic variation may impact physiological responses to caffeine consumption. The purpose of the present review was to systematically recognize how select single nucleotide polymorphisms (SNPs) impact habitual use of caffeine as well as the ergogenic and anxiogenic consequences of caffeine. Two databases (PubMed and EBSCO) were independently searched using the same algorithm. Selected studies involved human participants and met at least one of the following inclusion criteria: (a) genetic analysis of individuals who habitually consume caffeine; (b) genetic analysis of individuals who underwent measurements of physical performance with the consumption of caffeine; (c) genetic analysis of individuals who underwent measurements of mood with the consumption of caffeine. We included 26 studies (10 randomized controlled trials, five controlled trials, seven cross-sectional studies, three single-group interventional studies and one case-control study). Single nucleotide polymorphisms in or near the cytochrome P450 (CYP1A2) and aryl hydrocarbon receptor (AHR) genes were consistently associated with caffeine consumption. Several studies demonstrated that the anxiogenic consequences of caffeine differed across adenosine 2a receptor (ADORA2A) genotypes, and the studies that investigated the effects of genetic variation on the ergogenic benefit of caffeine reported equivocal findings (CYP1A2) or warrant replication (ADORA2A).