Apnea or normal breathing during repeated high-intensity swimming enhance sprint efficiency and which metabolic disorder?

BACKGROUND: The aim of this study was to investigate the effect of normal breath and apnea swimming on acid-base balance, physiological responses and performance during high-intensity interval training in swimming. METHODS: Sixteen swimmers completed 6×50 m intervals of freestyle swimming with normal breath and apnea at maximum intensity, with 1 minute rest. Capillary blood gases (pH, PCO2, PO2, HCO3, Hct, Hb) were collected at four (4) measurement time points: 1) at rest once; 2) at rest just after the 3rd repetition; 3) at finish; and 4) at 10 min of recovery. Heart rate (HR) during swimming, lactate acid (La) concentration and swimming time (t50) were measured. RESULTS: Our study showed uncompensated metabolic acidosis due to increased lactic acidosis in both breathing conditions, more pronounced in apnea, and faster swimming times in apnea without different heart rate responses. CONCLUSIONS: Apnea during repetitive high intensity long distance interval 50 m freestyle swimming causes uncompensated metabolic acidosis but improves sprint performance.

Bone Mineral Content Distribution in Response to Long-term Training of Elite Rowers.

BACKGROUND/AIM: Bone response to exercise depends on the type and size of the mechanical stimulus. In rowing, athletes are exposed to low mechanical but large compression loads mainly on the trunk. Thus, this study aimed to investigate the impact of rowing on total and regional bone quality and bone turnover parameters in elite rowing athletes vs. control subjects. MATERIALS AND METHODS: Twenty world-class rowers and twenty active, but not athletic, men participated in the study. Bone mineral density (BMD) and body mineral content (BMC) were assessed by dual-energy X-ray absorptiometry (DXA). Bone turnover markers (OPG and RANKL) in serum were assessed by Elisa method. RESULTS: The current research revealed no statistical difference in total bone mineral density (TBMD) and total body mineral content (TBMC) between elite-level rowers and control subjects. Nevertheless, Trunk BMC (p=0.02) and Trunk BMC/TBMC ratio (p=0.01) were significantly higher in rowers than those in the control group. In contrast, in the control group, the Lower limbs BMC/TBMC ratio (p=0.007) was statistically higher. Furthermore, RANKL (p=0.011) and OPG (p=0.03) were statistically significantly higher in rowers, whereas the OPG/RANKL ratio (p=0.012) was statistically higher in the control group. CONCLUSION: Rowing, as a non-weight-bearing exercise, did not alter total bone density but induced a remarkable redistribution of bone density from the lower limbs to the trunk. In addition, the current evidence suggests that the underlying molecular mechanism is based on turnover of intermediates, rather than solely bone redistribution.

Antioxidant and Antibacterial Properties of a Functional Sports Beverage Formulation.

Athletes often consume functional beverages in order to improve performance and reduce oxidative stress caused by high-intensity exercise. The present study aimed to evaluate the antioxidant and antibacterial properties of a functional sports beverage formulation. The beverage's antioxidant effects were assessed on human mesenchymal stem cells (MSCs) by determining thiobarbituric acid reactive substances (TBARS; TBARS levels decreased significantly by 52.67% at 2.0 mg/mL), total antioxidant capacity (TAC; TAC levels increased significantly by 80.82% at 2.0 mg/mL) and reduced glutathione (GSH; GSH levels increased significantly by 24.13% at 2.0 mg/mL) levels. Furthermore, the beverage underwent simulated digestion following the INFOGEST protocol to assess its oxidative stability. The analysis of the total phenolic content (TPC) using the Folin-Ciocalteu assay revealed that the beverage contained a TPC of 7.58 ± 0.066 mg GAE/mL, while the phenolics identified by HPLC were catechin (2.149 mg/mL), epicatechin (0.024 mg/mL), protocatechuic acid (0.012 mg/mL), luteolin 7-glucoside (0.001 mg/mL), and kaempferol-3-O-ß-rutinoside (0.001 mg/mL). The beverage's TPC was strongly correlated with TAC (R2 = 896). Moreover, the beverage showcased inhibitory and bacteriostatic effects against Staphylococcus aureus and Pseudomonas aeruginosa. Lastly, the sensory acceptance test demonstrated that the functional sports beverage was well accepted by the assessors.

Birth Weight was Favorably Associated With Physical Fitness in Childhood After Adjustment for Several Perinatal Factors.

BACKGROUND: The purpose was to examine the potential associations of birth weight and infant growth with physical fitness (PF) components in childhood. METHOD: A random sample of 5125 dyads of children aged 8-9 years and their mothers were evaluated. Telephone interviews were carried out with the use of a standardized questionnaire for the collection of maternal lifestyle factors. Mothers were asked to provide information contained in their medical booklets and pregnancy ultrasound records. Data from 5 PF tests were used to assess cardiorespiratory fitness, speed, and body strength. Linear regression analysis was applied to assess the associations between birth weight and infant growth with PF test performances and logistic regression analysis to evaluate the associations of normal weight versus low birth weight and normal versus accelerated infant growth with PF tests performance categories (low vs high/average). RESULTS: Birth weight was favorably associated with cardiorespiratory fitness (b = 0.12 stage increase per SD increase in birth weight, P = .047), lower body strength (b = 1.07, P = .037), upper body strength (b = 0.10, P = .038), and speed (b = -0.04, P = .001), and infant growth was associated with upper body strength (b = 0.21 cm increase per SD increase in infant weight gain, P < .001) after adjusting for children's body mass index and several perinatal factors. Low birth weight children had 35% increased odds for low performances in PF tests compared with their normal birth weight counterparts. CONCLUSION: Low birth weight negatively affects childhood PF, and hence, it could play an unfavorable role in the future health of the offspring.

Resilience of the Hellenic navy seals assessed by heart rate variability during cognitive tasks.

OBJECTIVES: The interaction between high physical performance under extreme conditions in military and the simultaneous control of the cognitive executive functioning has been a subject of research in literature for the past few decades. Stroop test and Heart-rate variability (HRV), have been verified valuable clinical tools for the assessment of cerebral and autonomic/ cardiovascular stress responses respectively. METHODS: Thirty-four subjects were enrolled in this study. Of them, 18 were candidates under intense preparation for their enlistment in the Hellenic Navy SEALs (HN-SEALs) and 16 were healthy controls (HC). All subjects underwent stroop tasks, along with mental state and personality examination. HRV variables in time and frequency domains recordings were acquired, during each aforementioned cognitive testing procedure. RESULTS: Our results showed that HNS's performance on both cognitive and emotion stroop tasks were equivalent to controls (p≥.054); however, HNS exhibited statistically significant lower levels of HRV in different time and frequency domain variables, compared to HC (ranged from p<.01 to p<.05). Finally, in a between group comparison of the psychometric tools, HNS had significantly higher somatization, anxiety and neuroticism than HC. CONCLUSION: In conclusion, these findings indicate that HNS display flexibility in their autonomic regulation during cognitive and emotional tasks. This characteristic is closely related to problem solving or adaptability skills. Therefore, we support that HRV measurement turns out to be an invaluable tool for both scientific and clinical insights, promising to be an index regarding the psychophysiological resilience especially in the neurovisceral integration (NVI) model.

Assessment of Resilience of the Hellenic Navy Seals by Electrodermal Activity during Cognitive Tasks.

Stress resilience plays a key role in task performance during emergencies, especially in occupations like military special forces, with a routine consisting of unexpected events. Nevertheless, reliable and applicable measurements of resilience in predicting task performance in stressful conditions are still researched. This study aimed to explore the stress response in the Hellenic Navy SEALs (HN-SEALs), using a cognitive-physiological approach. Eighteen candidates under intense preparation for their enlistment in the HN-SEALs and 16 healthy controls (HCs) underwent Stroop tests, along with mental-state and personality examination. Simultaneously, electrodermal activity (EDA) was assessed during each one of cognitive testing procedures. Compared to healthy control values, multiple components of EDA values were found decreased (p < 0.05) in the HN-SEALs group. These results were associated with an increase in resilience level in the HN-SEALs group, since a restricted sympathetic reactivity according to the reduced EDA values was observed during the stressful cognitive testing. This is the first report providing physiological measurements of the sympathetic response of HN-SEALs to a stressful situation and suggests that EDA turns out to be a simple and objective tool of sympathetic activation and it may be used as a complementary index of resilience in HN-SEALs candidates.

The effect of prolonged intense physical exercise of special forces volunteers on their plasma protein denaturation profile examined by differential scanning calorimetry.

The human blood plasma proteome profile has been an area of intensive investigation and differential scanning calorimetry (DSC) has come forward as a novel tool in analyzing plasma heat capacity changes to monitor various physiological responses in health and disease. This study used DSC to assess potential alterations in the plasma heat capacity profile of albumin and globulins during extremely demanding physical exercise. We monitored the changes in denaturation profiles of those plasma proteins for five consecutive days of an extraordinary exercise training schedule in 14 young male Special Forces volunteers, as well as after a 30-day recovery period. The major effect of the prolonged intense exercise was the continuous upward shift of the albumin peak by 2°-3 °C on the initial days of exercise, with a tendency to plateau circa the 5th day of exercise. In addition, some redistribution of the denaturational enthalpy was observed upon exercise, where the globulins peak increased relative to the albumin peak. Noteworthy, the alterations in the plasma proteome denaturational profiles were not persistent, as virtually full recovery of the initial status was observed after 30 days of recovery. Our findings indicate that 5 days of exhaustive physical exercise of highly trained individuals enhanced the thermal stability of plasma albumin shifting its denaturational transition to higher temperatures. We surmise that these effects may be a result of increased blood oxygenation during the prolonged intense exercise and, consequently, of albumin oxidation as part of the overall adaptation mechanisms of the body to extreme physical and/or oxidative stress.

Endocannabinoids and Heart Rate Variability Alterations after Exposure to Prolonged Intensive Physical Exercise of the Hellenic Navy SEALs.

BACKGROUND: Recent research indicates that both endocannabinoids (eCB) and heart rate variability (HRV) are associated with stress-induced experiences. However, these underlying mechanisms are not elucidated. The present study aims to investigate whether exposure to acute and chronic stress conditions can give rise to measurable changes, both to the peripheral eCB ligands and HRV. METHODS: Thirteen candidates under intense preparation for their enlistment in the Hellenic Navy SEALs (HNS) participated in the study. All subjects underwent mental state examination, while HRV variables in time and frequency domain recordings were acquired. Furthermore, at baseline and 30 days after prolonged and intensive physical exercise, hair was collected to measure eCB ligands, such as anandamide (AEA), 2-arachidonoylglycerol (2-AG), and the N-acyl ethanolamine (NAE) molecules: palmitoylethanolamide (PEA) and oleoylethanolamide (OEA). RESULTS: Comparing basal hair concentrations of eCB ligands before and after intense physical exercise, we found that AEA, PEA, and OEA were notably increased, whereas no differences were observed regarding the ligand 2-AG. Furthermore, there were observed associations between the concentrations of peripheral eCB ligands, both at baseline and after the prolonged physical exercise and the time and frequency domains of HRV. CONCLUSIONS: These findings suggest that endocannabinoid-HRV interrelations might share a short-term, and long-term adaptability of the changes in self-regulation associated with stress. Further studies will be required to determine the validity of peripheral eCB signaling and HRV as a biomarker for different aspects of the stress response.

Associations of Maternal Prepregnancy Body Mass Index and Gestational Weight Gain With Physical Fitness in Childhood.

PURPOSE: To investigate the potential associations of maternal prepregnancy body mass index (mppBMI) and gestational weight gain (GWG) with physical fitness in children. METHODS: A random sample of 5125 children and their mothers was evaluated. The mothers provided data contained in their medical booklets and pregnancy ultrasound records. The data from 5 physical fitness tests (eg, 20-m shuttle run, 30-m sprint, vertical jump, standing long jump, and small ball throw) were used to assess children's cardiorespiratory fitness, speed, explosive power, and lower and upper body strength, respectively. RESULTS: MppBMI was inversely associated with cardiorespiratory fitness (b = -0.02), lower body strength (b = -1.01), upper body strength (b = -0.07), and speed (b = 0.04). Also, GWG was unfavorably associated with cardiorespiratory fitness (b = -0.02), lower body strength (b = -1.12), upper body strength (b = -0.03), and speed (b = 0.03), after adjusting for sex, birth weight, and children's BMI (all P values < .05). Children of mothers with an mppBMI ≥ 25 kg/m2 and excess GWG had almost 30% and 20% increased odds for low performances in physical fitness tests than those of mothers with an mppBMI < 25 kg/m2 and adequate GWG, respectively. CONCLUSIONS: Antenatal factors such as increased mppBMI and excess GWG could play an unfavorable role in the future health of the offspring.

Exclusive Breastfeeding Is Favorably Associated with Physical Fitness in Children.

Objective: To examine the potential association between exclusive breastfeeding and its duration on physical fitness (PF) components during childhood. Materials and Methods: A random sample of 5,125 dyads children and their mothers was evaluated. With the use of a standardized questionnaire, telephone interviews were carried out for the collection of maternal lifestyle factors (e.g., breastfeeding and its duration, etc.). Data from five PF tests (e.g., vertical jump, standing long jump, small ball throw, 30-m sprint, and 20-m shuttle run) were used to assess lower and upper body strength, speed, and cardiorespiratory fitness (CRF). Linear and logistic regression models were estimated and adjusted for children's body mass index (BMI) and birth weight, and parental factors (prepregnancy BMI, gestational weight gain, gestational age, pregnancy in vitro, parity before, and educational level). Results: Among boys, exclusive breastfeeding was favorably associated with CRF (b = 0.07), lower body strength (b = 0.41), upper body strength (b = 0.10), and speed (b = -0.11). Also, among girls, we found a favorable association between exclusive breastfeeding and CRF (b = 0.07), lower body strength (b = 0.47), upper body strength (b = 0.10), and speed (b = -0.11). All of the associations remained significant after adjusting for several potential confounders. With the exception of speed test in girls, children who were exclusively breastfed ≥6 months had 10-40% increased odds for average/high performances in PF tests in comparison with those who were breastfed <1 month. Conclusions: Exclusive breastfeeding ≥6 months had a favorable influence on PF test performances in childhood. It seems that exclusive breastfeeding could play a significant role in children's future health.

Association of Exclusive Breastfeeding with Risk of Obesity in Childhood and Early Adulthood.

OBJECTIVE: To explore the effects of exclusive breastfeeding and its duration on the development of childhood and early adulthood obesity. MATERIALS AND METHODS: A random sample of 5,125 dyad children and their mothers was extracted from a national database. With the use of a standardized questionnaire, telephone interviews were carried out for the collection of maternal lifestyle factors (e.g., breastfeeding). The body mass index was determined based on International Obesity Task Force criteria. Body weight and height of the offspring at the age of 8 was calculated from measurements derived from the national database, while the corresponding body measurements at early adulthood were self-reported. RESULTS: Mothers who had breastfed or exclusively breastfed ≥6 months were 22.4% and 15.2%, respectively. Exclusive breastfeeding ≥6 months (versus never) was associated with a lower risk of overweight in childhood (8 years old; odds ratio [OR] = 0.89; 95% confidence interval [95% CI], 0.82-0.96) and adolescence/adulthood (15-25 years old; OR = 0.83; 95% CI, 0.68-0.97). Also, exclusive breastfeeding ≥6 months (versus never) was associated with a decreased risk of childhood and adolescence obesity by 30% (95% CI, 0.54-0.91) and 38% (95% CI, 0.40-0.83), respectively. CONCLUSIONS: Exclusive breastfeeding had a favorable influence on offspring's overweight and obesity not only in childhood but also in adolescence/adulthood.

Maternal lifestyle characteristics during pregnancy, and the risk of obesity in the offspring: a study of 5,125 children.

BACKGROUND: To investigate the association between gestational weight gain, maternal age and lifestyle habits (e.g., physical activity, smoking, and alcohol consumption) during pregnancy, with Body Mass Index of the offspring at the age of 8. METHODS: Α random sample of 5,125 children was extracted from a national database and matched with their mothers. With the use of a standardised questionnaire, telephone interviews were carried out for the collection of information like: maternal age at pregnancy, gestational weight gain (GWG), exercise levels, smoking and alcohol consumption. The Body Mass Index (BMI) status of the offspring at the age of 8 was calculated from data retrieved from the national database (e.g., height and weight). RESULTS: The odds for being overweight/obese at the age of 8 for 1 kg GWG, for smoking, and for mild exercise during pregnancy compared to sedentary was 1.01 (95%CI: 1.00, 1.02), 1.23 (95%CI: 1.03, 1.47) and 0.77 (95%CI: 0.65, 0.91), respectively. Further analysis revealed that offspring of women who exceeded the Institute of Medicine (IOM) maternal weight gain recommendations were at an increased risk of obesity (OR: 1.45; 95%CI, 1.26, 1.67) compared with offspring of women with GWG within the recommended range. Maternal age and alcohol consumption were not associated with the outcome (p > 0.05). CONCLUSION: GWG, physical activity and smoking status during pregnancy were significantly associated with obesity for the offspring at the age of 8. Health care professionals should strongly advise women to not smoke and to perform moderate exercise during pregnancy to prevent obesity in the offspring in later life.

Fluid Balance During Training in Elite Young Athletes of Different Sports.

Although there are many studies demonstrating a high percentage of adult athletes who start exercise in suboptimal hydration state, limited data concerning hydration levels in athletic youth exist. The purpose of this study was to identify the hydration status of elite young athletes of different sports, during a typical day of training. Fifty-nine young elite male athletes from different sports (basketball, gymnastics, swimming, running, and canoeing) participated in the study (age: 15.2 ± 1.3 years; years of training: 7.7 ± 2.0). Hydration status was assessed in the morning, before and immediately after practice. Data collection took place at the same time of the day, with mean environmental temperature and humidity at the time of the measurements at 27.6 ± 0.9° C and 58 ± 8%, respectively. All athletes trained for approximately 90 minutes, and they were consuming fluids ad libitum throughout their practice. Over 89% of the athletes were hypohydrated (urine specific gravity [USG] ≥1.020 mg·dl) based on their first morning urine sample. Pretraining urine samples revealed that 76.3% of the athletes were hypohydrated, whereas a significant high percent remained hypohydrated even after training according to USG values ≥1.020 mg·dl (74.5%) and urine color scale: 5-6 (76.3%). Mean body weight loss during training was -1.1 ± 0.07%. We concluded that the prevalence of hypohydration among elite young athletes is very high, as indicated by the USG and urine color values. The majority of the athletes was hypohydrated throughout the day and dehydrated even more during practice despite fluid availability.