Response of Appetite and Appetite Regulating Hormones to Acute Hypoxia

AIM: To determine the acute response of appetite and appetite regulating hormones after exposure to simulated altitude. METHODS: Seven males and five females (height: 178.9 ± 2.3 cm; weight: 77.3 ± 7.2 kg; body fat: 18.4 ± 1.7%) participated in two, three-hour trials in a hypoxic (5000 m) and normoxic (350 m) environment. Blood samples were collected prior to and immediately following three hours of exposure for the measurement of leptin, adiponectin, and acylated ghrelin. Appetite, acute mountain sickness, heart rate, blood oxygenation, tissue oxygenation, respiration rate, and whole body gases were also measured. RESULTS: Leptin was not different between hypoxic (5.8 ± 1.8 ng ml-1) and normoxic trials (6.2 ± 2.0 ng ml-1; p = 0.603). Adiponectin was not different between hypoxic (9.0 ± 0.2 µg ml-1) and normoxic trials (8.4 ± 0.7 µg ml-1; p = 0.216). Acylated ghrelin was not different between hypoxic (15.0 ± 3.8 pg ml-1) and normoxic trials (16.3 ± 4.6 pg ml-1; p = 0.285). Appetite scores were not different between trials (p \u3e 0.05) with the exception of fullness which was greater in the hypoxic condition (p = 0.027). Heart rate and symptoms of acute mountain sickness were higher while blood and tissue oxygenation were lower in the hypoxic trial (p \u3c 0.05). No differences were noted in other metabolic parameters (p \u3e 0.05). CONCLUSION: Appetite and appetite regulating hormones are not affected by three hours of hypoxic exposure, and thus some of these negative consequences of hypoxic exposure may not be evident with short exposure times

Higher Muscle Tissue Oxygenation When Exposed to Hypobaric Hypoxia Than Normobaric Hypoxia

There has been recent debate on the potential difference in physiological response between exposure to simulated altitude (normobaric hypoxia) and terrestrial altitude (hypobaric hypoxia). Purpose: To determine the difference in the physiological response to normobaric and hypobaric hypoxia during exercise. Methods: Eight recreationally active subjects (27 ± 5 y old, 73.1 ± 7.4 kg body weight, 170.6 ± 6.7 cm height, and 19.3 ± 9.2 % body fat) completed incremental cycling exercise to volitional fatigue in three separate environments: normobaric normoxia (NN; 350 m), normobaric hypoxia (NH; simulated 3094 m), and hypobaric hypoxia (HH; 3094 m). Heart rate, blood oxygen saturation, and muscle tissue oxygenation were measured at rest and continuously throughout the exercise trials. Results: Blood oxygen saturation (SpO2) was ~10% higher in NN compared to the two hypoxic conditions (p \u3c 0.001) at rest and all exercise stages, with no difference between NH and HH (p \u3e 0.05). Heart rate was higher at rest in HH (98 ± 13 bpm) compared to NN (83 ± 15 bpm, p = 0.011) and NH (84 ± 14 bpm, p = 0.001) which persisted until 165 watts at which point no difference was observed (p \u3e 0.05). Muscle tissue oxygenation was 17% higher in HH compared to NN and 19% higher than NH throughout exposure (p \u3c 0.05). Conclusion: This data indicates that the hypoxic stress resulting from normobaric and hypobaric hypoxia are not the sameand that hypobaric hypoxia may not result in hypoxia at the level of the tissue

Acute High Intensity Anaerobic Training and Rhabdomyolysis Risk

International Journal of Exercise Science 8(1) : 65-74, 2015. The current popularity of high intensity anaerobic training has caused concerns over the safety and prevalence of conditions such as rhabdomyolysis; thus it is important to understand the possible risks of participating in this type of activity. The purpose of this study was to determine the magnitude of muscle damage associated with a single high intensity anaerobic training session, and the relationship of this response to markers of fitness. Fifteen recreationally trained male participants (age 22.9 ± 4.3 y, mass 87.3 ± 15.6 kg, body fat 16.8 ± 6.4%, VO2 peak 50.1 ± 7.2 ml · kg-1 · min-1 ) completed a single anaerobic training session consisting of high intensity plyometrics and calisthenics. Prior to the exercise session, participants completed a maximal aerobic capacity test, body composition analysis, and a military physical fitness test (1 min push-ups, 54 ± 14; 1 min sit-ups, 45 ± 11; 1.5 mile run, 12:17 ± 0.067 min). Serum creatine kinase (CK) was measured prior to and 48 h following the exercise session. CK at 48 h (126.3 ± 68.9 U· L-1) did not reach the limits indicating rhabdomyolysis (~881-1479 U/L) but was elevated above resting (CK resting 90.5 ± 53.4). VO2 peak (L · m-1) had a positive correlation with CK levels (r = .51; p \u3c 0.05) but body mass or any other indicator of fitness did not correlate. An increase in serum CK levels occurred, but did not reach levels of rhabdomyolysis, suggesting that a single high intensity exercise session is safe for healthy individuals who exercise regularly

The Effects of 3-Weeks of Aerobic Exercise in Heat on Fitness and PGC1a in Females

The effects of exercise training in the heat are well documented in men. However, the effects of exercise training in the heat in women have not received as much attention. We have previously reported a blunted rise in PGC1α in men after acute aerobic exercise in the heat. Purpose: To determine the impact of three weeks of aerobic exercise training in the heat compared to training in room temperature on thermoregulation, PGC1α mRNA response, and aerobic capacity in women. Methods: Twenty-three untrained college aged females (24±4 yoa, 168±5 cm, and 67.3±11.2 kg) were randomly assigned to 3 weeks of aerobic exercise training in either 20°C (n=12) or 33°C (n=11). Results: VO2max in room temperature conditions increased with training (2.57±0.35 to 2.71±0.32 L·min-1, p=0.01), but independent of temperature condition (p=0.821). HR decreased with training (152±16 to 140±0.13 bpm, p\u3c0.001), but was independent of temperature condition (p=0.341). Sweat rate increased with training (0.655±0.192 to 0.775±0.212 L·hr-1, p=0.006) and was higher in 33°C (0.835±0.144 L·hr-1) than 20°C (0.605±0.132 L·hr-1, p\u3c0.001). PGC1α mRNA increased with an acute exercise bout before (1.01±0.10 to 4.96±2.08 fold, p\u3c0.001) and after training (1.07±0.10 to 3.21±1.39 fold, p\u3c0.001) and had a smaller response after training than before training (p=0.005), but there were no differences between temperature groups (p=0.661). Conclusions: Women can increase aerobic fitness and maintain their exercise induced PGC1α mRNA response in the heat equally to that of room temperature conditions. This response contrasts with the blunted PGC1α mRNA response and VO2 max alterations previously observed in men

Substrate Use and Biochemical Response to a 3,211-km Bicycle Tour in Trained Cyclists

The purpose of this study was to assess the physiological adaptations in physically fit individuals to a period of intensified training. Ten trained males cycled outdoors ~170 km day−1 on 19 out of 21 days. Expired gas was collected on days 1 and 21 during maximal graded exercise and used for the determination of gross efficiency and whole body substrate use. Muscle biopsies were obtained before and after exercise on days 2 and 22 for the determination of mtDNA/gDNA ratio, gene expression, metabolic enzyme activity and glycogen use. Muscle glycogen before and after exercise, fat oxidation, and gross efficiency increased, carbohydrate oxidation decreased (p \u3c 0.05), and VO2max did not change over the 21 days of training. Citrate synthase (CS), β-hydroxyacyl CoA dehydrogenase (β-HAD) and cytochrome c oxidase (COX) enzyme activity did not change with training. CS and β-HAD mRNA did not change with acute exercise or training. COX (subunit IV) mRNA increased with acute exercise (p \u3c 0.05) but did not change over the 21 days. PGC-1α mRNA increased with acute exercise, but did not increase to the same degree on day 22 as it did on day 2 (p \u3c 0.05). UCP3 mRNA decreased with training (p \u3c 0.05). Acute exercise caused an increase in mitofusin2 (MFN2) mRNA (p \u3c 0.05) and a trend for an increase in mtDNA/gDNA ratio (p = 0.057). However, training did not affect MFN2 mRNA or mtDNA/gDNA ratio. In response to 3,211 km of cycling, changes in substrate use and gross efficiency appear to be more profound than mitochondrial adaptations in trained individuals

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 (2)H(2)(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

Validity of the iHealth-BP7 and Withings-BP800 Self Measurement Blood Pressure Monitor

PURPOSE: The purpose of this study is to validate the iHealth-BP7 and Withings-BP800 monitors according to the European Society of Hypertension (ESH) International Protocol revision 2010. METHODS: Data from 11 participants (31.6 ± 2.2 years) were initially examined according to the ESH International Protocol for the validation of BP measuring devices. Participants were asked to sit and relax for 10-15 mins with legs uncrossed, and back supported prior to the test. In all participants, sequential left arm measurements were performed by two trained observers using a mercury sphygmomanometer and one supervisor using the device. Collected data were screened according to the ESH protocol RESULTS: The mean differences between the monitor and sphygmomanometer readings were -0.55±3.75 (SBP) and 0.54±3.62 (DBP) for iHealth-BP7 and 3.18±4.37 (SBP) and - 0.35±5.42 (DBP) for Withings-BP800. The iHealth-BP7 monitor passed all of the modified requirements, however the WithingsBP800 did not meet the last phase of the modified protocol. CONCLUSION: The iHealth-BP7 monitor is recommended as a valid home BP monitoring device, however the Withings-BP800 fails to meet the ESH criteria in this study potentially due to the small sample size. Since the ESH protocol requires 33 subjects, further study with additional participants is warranted to determine validation of both devices

Effects of passive and active leg movements to interrupt sitting in mild hypercapnia on cardiovascular function in healthy adults

Prolonged sitting in a mild hypercapnic environment impairs peripheral vascular function. The effects of sitting interruptions using passive or active skeletal muscle contractions are still unclear. Therefore, we sought to examine the vascular effects of brief periods (2 min every half hour) of passive and active lower limb movement to interrupt prolonged sitting with mild hypercapnia in adults. Fourteen healthy adults (24 ± 2 yr) participated in three experimental visits sitting for 2.5 h in a mild hypercapnic environment (CO2 = 1,500 ppm): control (CON, no limb movement), passive lower limb movement (PASS), and active lower limb movement (ACT) during sitting. At all visits, brachial and popliteal artery flow-mediated dilation (FMD), microvascular function, plasmatic levels of nitrate/nitrite and endothelin-1, and heart rate variability were assessed before and after sitting. Brachial and popliteal artery FMDs were reduced in CON and PASS (P \u3c 0.05) but were preserved (P \u3e 0.05) in ACT. Microvascular function was blunted in CON (P \u3c 0.05) but was preserved in PASS and ACT (P \u3e 0.05). In addition, total plasma nitrate/nitrite was preserved in ACT (P \u3e 0.05) but was reduced in CON and PASS (P \u3c 0.05), and endothelin-1 levels were decreased in ACT (P \u3c 0.05). Both passive and active movement induced a greater ratio between the low-frequency and high-frequency bands for heart rate variability (P \u3c 0.05). For the first time, to our knowledge, we found that brief periods of passive leg movement can preserve microvascular function, but that an intervention that elicits larger increases in shear rate, such as low-intensity exercise, is required to fully protect both macrovascular and microvascular function and circulating vasoactive substance balance

Effects on Oxygen Consumption and Metabolic Gene Expression when Determining Experimental Exercise Intensity Based on Exercise Capacity Tests Conducted in Hypoxic and Normoxic Environments

Abstract: Exercise intensity can be set relative to VO2 max measured during hypoxic or control conditions in studies investigating exercise in hypoxic environments. It currently is not clear which is the most appropriate method. Objective: The objective of this brief report is to determine the response to 1 hour of cycling at 60% of peak power when measured in either normoxic or hypoxic conditions. Methods: Eleven recreationally active male participants (24 ± 4 yrs, 173 ± 20 cm, 82 ± 12 kg, 15.2 ± 7.1% fat, 4.0 ± 0.6 L x min-1 VO2 max) completed two 1 hour cycling exercise trials at 60% of peak power followed by 4 hours of recovery in ambient environmental conditions (975 m) and at normobaric hypoxic conditions simulating 3000 m in a randomized counter balanced order. Results: VO2 max was not different between trials in relative (p=0.272) or absolute terms (p=0.105) but peak power at VO2 max was higher in the 975 m trial (288 ± 17 watts) than the 3000 m trial (262 ± 12 watts, p=0.003) corresponding to differences at 60% of VO2 max power. Gene expression of HIF-1α, COX, PGC-1α, HK, and PFK increased with exercise (p\u3c0.05) but did not differ between trials. There was a trend (p=0.072) toward increased muscle glycogen use in 975m. Conclusions: Although there were not statistical differences for muscle markers in the current study, these data should be considered when determining exercise intensity in hypoxia related research