Impact of insulin resistance on subclinical left ventricular dysfunction in normal weight and overweight/obese japanese subjects in a general community.

BACKGROUND: Insulin resistance carries increased risk of heart failure, although the pathophysiological mechanisms remain unclear. LV global longitudinal strain (LVGLS) assessed by speckle-tracking echocardiography has emerged as an important tool to detect early LV systolic abnormalities. This study aimed to investigate the association between insulin resistance and subclinical left ventricular (LV) dysfunction in a sample of the general population without overt cardiac disease. METHODS: We investigated 539 participants who voluntarily underwent extensive cardiovascular health check including laboratory test and speckle-tracking echocardiography. Glycemic profiles were categorized into 3 groups according to homeostatic model assessment of insulin resistance (HOMA-IR): absence of insulin resistance (HOMA-IR < 1.5), presence of insulin resistance (HOMA-IR ≥ 1.5) and diabetes mellitus (DM). Multivariable logistic regression models were conducted to evaluate the association between abnormal glucose metabolism and impaired LVGLS (> - 16.65%). RESULTS: Forty-five (8.3%) participants had DM and 66 (12.2%) had abnormal HOMA-IR. LV mass index and E/e' ratio did not differ between participants with and without abnormal HOMA-IR, whereas abnormal HOMA-IR group had significantly decreased LVGLS (- 17.6 ± 2.6% vs. - 19.7 ± 3.1%, p < 0.05). The prevalence of impaired LVGLS was higher in abnormal HOMA-IR group compared with normal HOMA-IR group (42.4% vs. 14.0%) and similar to that of DM (48.9%). In multivariable analyses, glycemic abnormalities were significantly associated with impaired LVGLS, independent of traditional cardiovascular risk factors and pertinent laboratory and echocardiographic parameters [adjusted odds ratio (OR) 2.38, p = 0.007 for abnormal HOMA-IR; adjusted OR 3.02, p = 0.003 for DM]. The independent association persisted even after adjustment for waist circumference as a marker of abdominal adiposity. Sub-group analyses stratified by body mass index showed significant association between abnormal HOMA-IR and impaired LVGLS in normal weight individuals (adjusted OR 4.59, p = 0.001), but not in overweight/obese individuals (adjusted OR 1.62, p = 0.300). CONCLUSIONS: In the general population without overt cardiac disease, insulin resistance carries independent risk for subclinical LV dysfunction, especially in normal weight individuals.

Independent effect of visceral fat on left atrial phasic function in the general population.

BACKGROUND AND AIMS: Obesity increases the risk for atrial fibrillation (AF), although the impact of abdominal fat distribution on left atrial (LA) morphology and functional remodeling remains unclear. This study aimed to investigate whether increased abdominal adiposity is independently associated with impaired LA function and/or LA enlargement in a sample of the general population and to evaluate the role of adipokines in this association. METHODS AND RESULTS: The study cohort consisted of 527 participants (362 men; 57 ± 10 years) without overt cardiac disease who underwent laboratory testing, abdominal computed tomographic examination and echocardiography. Abdominal adiposity was quantitatively assessed as visceral fat area (VFA) and subcutaneous fat area (SFA) at the level of the umbilicus. Speckle-tracking echocardiography was performed to assess LA phasic function including reservoir, conduit and pump strain. LA reservoir and conduit strain decreased with increasing VFA quartiles (both p < 0.05), whereas no significant differences were observed in LA volume index and pump strain. When stratified by SFA, there were no significant differences in LA size and function across the quartiles. In multivariable analysis, VFA was significantly associated with LA conduit strain independent of cardiovascular risk factors, and pertinent laboratory and echocardiographic parameters (standardized ß = -0.136, p = 0.019). VFA was correlated with serum adiponectin level (r = -0.51, p < 0.001), but there was no association between adiponectin level and three LA phasic strains. CONCLUSION: In a sample of the general population, VFA accumulation was independently associated with worse LA conduit strain, which may be involved in the pathophysiological mechanism of obesity-related AF.

Effect of progressive normobaric hypoxia on dynamic cerebral autoregulation.

NEW FINDINGS: What is the central question of this study? Acute hypoxia reduces dynamic cerebral autoregulation (dCA); however, it is unclear what level of hypoxia is necessary to exert this effect. We sought to investigate whether dCA would be reduced during progressive periods of normobaric hypoxia using a duplex Doppler ultrasound technique to evaluate the volumetric blood flow. What is the main finding and its importance? We showed that dCA decreased linearly as inspired O2 decreased from 21 to 12%. Additionally, symptoms of acute mountain sickness were related to changes in dCA. Our results may provide a sensitive and clinically relevant test to evaluate the risk of acute mountain sickness. Cerebral blood flow is maintained at relatively constant levels over a wide range of perfusion pressures via cerebral autoregulation (CA). Although acute hypoxia reduces dynamic CA, it is unclear what level of hypoxia is necessary to exert this effect. We evaluated dynamic CA during progressive normobaric hypoxia (∼1 h at each of 21, 18, 15 and 12% O2 ) using duplex ultrasonography to measure volumetric changes in common carotid artery blood flow of 11 healthy young men. Dynamic CA was evaluated by the thigh-cuff method and represented as the rate of regulation of vascular conductance. On a separate occasion, symptoms of acute mountain sickness were evaluated during 6 h of prolonged hypoxia (fractional inspired O2 of 14.1%) using the Lake Louise Questionnaire. Repeated-measures ANOVA with linear trend analysis indicated that dynamic CA decreased progressively as fractional inspired O2 was reduced (P < 0.001). Spearman rank order analysis revealed that symptoms of acute mountain sickness were related to changes in the rate of regulation of vascular conductance from 21 to 15% (r = -0.869, P = 0.006) and from 21 to 12% O2 (r = -0.648, P = 0.040), respectively. These results suggest that dynamic CA worsens with progressive hypoxia and that reductions in dynamic CA during moderate to severe hypoxia (<15% O2 ) may be related to the severity of acute mountain sickness.

Reduction in Cerebral Oxygenation After Prolonged Exercise in Hypoxia is Related to Changes in Blood Pressure.

We investigated the relation between blood pressure and cerebral oxygenation (COX) immediately after exercise in ten healthy males. Subjects completed an exercise and recovery protocol while breathing either 21% (normoxia) or 14.1% (hypoxia) O2 in a randomized order. Each exercise session included four sets of cycling (30 min/set, 15 min rest) at 50% of altitude-adjusted peak oxygen uptake, followed by 60 min of recovery. After exercise, mean arterial pressure (MAP; 87±1 vs. 84±1 mmHg, average values across the recovery period) and COX (68±1% vs. 58±1%) were lower in hypoxia compared to normoxia (P<0.001). Changes in MAP and COX were correlated during the recovery period in hypoxia (r=0.568, P<0.001) but not during normoxia (r=0.028, not significant). These results demonstrate that reductions in blood pressure following exercise in hypoxia are (1) more pronounced than in normoxia, and (2) associated with reductions in COX. Together, these results suggest an impairment in cerebral autoregulation as COX followed changes in MAP more passively in hypoxia than in normoxia. These findings could help explain the increased risk for postexercise syncope at high altitude.

Reference range of blood biomarkers for oxidative stress in Thoroughbred racehorses (2-5 years old).

The oxidant and antioxidant equilibrium is known to play an important role in equine medicine and equine exercise physiology. There are abundant findings in this field; however, not many studies have been conducted for reference ranges of oxidative stress biomarkers in horses. This study was conducted to determine the reference values of reactive oxygen metabolites (d-ROMs) and biological antioxidant potential (BAP) using blood samples from 372 (191 males, 181 females) Thoroughbred racehorse aged 2 to 5 (3.43 ± 1.10 (mean ± SD)) years old. There were obvious gender differences in oxidative biomarkers, and growth/age-related changes were observed especially in females. Gender and age must be considered when interpreting obtained oxidative stress biomarkers for diagnosis of disease or fitness alterations in Thoroughbred racehorses.

High-intensity exercise causes greater irisin response compared with low-intensity exercise under similar energy consumption.

Irisin is mainly released from skeletal muscle (myocytes) and promotes thermogenesis by browning of the white adipose tissue. Although exercise has been shown to increase irisin concentration in blood and myocytes via up-regulation peroxisome proliferator receptor γ coactivator-1α (PGC-1α) expression, the influence of exercise intensity on irisin secretion remains unclear. Therefore, we determined circulating irisin responses following a single bout of running at different intensities. Six sedentary males underwent treadmill running under two different conditions: a low-intensity (40% of VO2max) exercise trial (LIE) or a high-intensity (80% of VO2max) exercise trial (HIE). The exercises in LIE and HIE were lasted for 20 and 40 min, respectively. All subjects underwent the two trials on separate days, and a randomized cross-over design was used. Blood samples were collected before (Pre) and immediately after exercise, at 3, 6, and 19 h after exercise. Energy consumption during exercise did not significantly differ between the two trials. HIE significantly increased blood lactate and serum lactate dehydrogenase levels (P < 0.05). Compared with pre-exercise levels, the irisin concentrations were elevated at 6 h (18% increase) and 19 h (23% increase) after HIE, but significantly decreased after LIE. The relative irisin concentrations (compared with pre-exercise levels) were significantly greater in HIE than in LIE immediately after exercise, and at 6 and 19 h after exercise (P < 0.05). These findings suggest that irisin secretion after acute running exercise is affected by exercise intensity, independent of energy consumption.

Influence of short-term hypoxic exposure on spatial learning and memory function and brain-derived neurotrophic factor in rats-A practical implication to human's lost way.

The present study aimed to investigate the effects of a short period of normobaric hypoxic exposure on spatial learning and memory, and brain-derived neurotrophic factor (BDNF) levels in the rat hippocampus. Hypoxic conditions were set at 12.5% O2. We compared all variables between normoxic trials (Norm), after 24 h (Hypo-24 h), and after 72 h of hypoxic exposure (Hypo-72 h). Spatial learning and memory were evaluated by using a water-finding task in an open field. Time to find water drinking fountains was significantly extended in Hypo 24 h (36.2 ± 21.9 s) compared to those in Norm (17.9 ± 12.8 s; P < 0.05), whereas no statistical differences between Norm and Hypo-72 h (22.7 ± 12.3 s). Moreover, hippocampal BDNF level in Hypo-24 h was significantly lower compared to Norm (189.4 ± 28.4 vs. 224.9 ± 47.7 ng/g wet tissue, P < 0.05), whereas no statistically differences in those between Norm and Hypo-72 h (228.1 ± 39.8 ng/g wet tissue). No significant differences in the changes in corticosterone and adrenocorticotropic hormone levels were observed across the three conditions. When data from Hypo-24 h and Hypo-72 h of hypoxia were pooled, there was a marginal negative relationship between the time to find drinking fountains and BDNF (P < 0.1), and was a significant negative relationship between the locomotor activities and BDNF (P < 0.05). These results suggest that acute hypoxic exposure (24 h) may impair spatial learning and memory; however, it recovered after 72 h of hypoxic exposure. These changes in spatial learning and memory may be associated with changes in the hippocampal BDNF levels in rats.

[The effects of age, period, and birth cohorts on the rates of overweight and underweight students in 1977-2006 and a prediction of the rates in 2007-2016].

OBJECTIVES: The increase in the overweight or underweight student population in Japanese schools is an important health issue. To assess the independent effects of age, period, and birth cohorts, we analyzed trends in the rates of overweight and underweight students from 1977 to 2006 using a Bayesian age-period-cohort (APC) analysis. Additionally, we predicted the rates overweight and underweight students in 2007-2016. METHODS: We created a data set of the rates of overweight and underweight students aged 6-14 years using the annual school health survey report data. We then analyzed a cohort table that plotted age against calendar time using a Bayesian APC model. We also made a prediction of the rates of overweight and underweight students in 2007-2016. RESULTS: For overweight students, the age effect increased from 6 to 11 years of age for male students and from 6 to 12 years of age for female students; thereafter, the effects decreased. The period effects consistently increased until late 1990, and decreased thereafter for both male and female students. The cohort effects increased for male students born between 1963 and 1969, and later decreased for those born in 1981. However, this trend for male students later increased. For female students, the cohort effects decreased for those born between 1963 and 1975, and later increased for those born in 1990, indicating a plateau or slight increase in the trend. For underweight students, the age effect in male students increased from 7 to 10 years of age, and then plateaued; whereas, the age effect increased from 7 to 12 years of age for female students before reaching a plateau. The period effects increased consistently by 2000 and decreased slightly in both male and female students. The birth cohort effect in male students increased for those born after the mid-1980s, and then plateaued in the early 1990s. The cohort effect increased for female students born after 1984, and then plateaued in 1993. The projections for the rates of overweight and underweight student population indicated a steady trend until 2016. CONCLUSION: The rate of overweight and underweight students was strongly influenced by age; however, period and birth cohort also played a role. The projections for the rates of overweight and underweight students indicated a steady trend until 2016. These results suggest that strategies based on age-, period-, and cohort-specific measures may be required for future interventions for preventing overweight and underweight among students.

Five Days of Tart Cherry Supplementation Improves Exercise Performance in Normobaric Hypoxia.

Previous studies have shown tart cherry (TC) to improve exercise performance in normoxia. The effect of TC on hypoxic exercise performance is unknown. This study investigated the effects of 5 days of tart cherry (TC) or placebo (PL) supplementation on hypoxic exercise performance. Thirteen healthy participants completed an incremental cycle exercise test to exhaustion (TTE) under two conditions: (i) hypoxia (13% O2) with PL and (ii) hypoxia with TC (200 mg anthocyanin per day for 4 days and 100 mg on day 5). Pulmonary gas exchange variables, peripheral arterial oxygen saturation (SpO2), deoxygenated hemoglobin (HHb), and tissue oxygen saturation (StO2) assessed by near-infrared spectroscopy in the vastus lateralis muscle were measured at rest and during exercise. Urinary 8-hydro-2' deoxyguanosine (8-OHdG) excretion was evaluated pre-exercise and 1 and 5 h post-exercise. The TTE after TC (940 ± 84 s, mean ± standard deviation) was longer than after PL (912 ± 63 s, p < 0.05). During submaximal hypoxic exercise, HHb was lower and StO2 and SpO2 were higher after TC than PL. Moreover, a significant interaction (supplements × time) in urinary 8-OHdG excretion was found (p < 0.05), whereby 1 h post-exercise increases in urinary 8-OHdG excretion tended to be attenuated after TC. These findings indicate that short-term dietary TC supplementation improved hypoxic exercise tolerance, perhaps due to lower HHb and higher StO2 in the working muscles during submaximal exercise.

Association between non-alcoholic fatty liver disease and subclinical left ventricular dysfunction in the general population.

Aims: Emerging evidence suggests an association between non-alcoholic fatty liver disease (NAFLD) and heart failure (HF). We investigated the relationship between NAFLD and left ventricular (LV) functional remodelling in a general population sample without overt cardiac and liver disease. Methods and results: We included 481 individuals without significant alcohol consumption who voluntarily underwent an extensive cardiovascular health check. The fatty liver index (FLI) was calculated for each participant, and NAFLD was defined as FLI ≥ 60. All participants underwent 2D transthoracic echocardiography; LV global longitudinal strain (LVGLS) was assessed with speckle-tracking analysis. Univariable and multivariable linear regression models were constructed to investigate the possible association between NAFLD and LVGLS. Seventy-one (14.8%) participants were diagnosed with NAFLD. Individuals with NAFLD exhibited larger LV size and LV mass index than those without NAFLD, although left atrial size and E/e' ratio did not differ between groups. Left ventricular global longitudinal strain was significantly reduced in participants with vs. without NAFLD (17.1% ± 2.4% vs. 19.5% ± 3.1%, respectively; P < 0.001). The NAFLD group had a significantly higher frequency of abnormal LVGLS (<16%) than the non-NAFLD group (31.0% vs. 10.7%, respectively; P < 0.001). Multivariable linear regression analysis demonstrated that higher FLI score was significantly associated with impaired LVGLS independent of age, sex, conventional cardiovascular risk factors, and echocardiographic parameters (standardized ß -0.11, P = 0.031). Conclusion: In the general population without overt cardiac and liver disease, the presence of NAFLD was significantly associated with subclinical LV dysfunction, which may partly explain the elevated risk of HF in individuals with NAFLD.

Comparisons Between Normobaric Normoxic and Hypoxic Recovery on Post-exercise Hemodynamics After Sprint Interval Cycling in Hypoxia.

The aim of this study was to investigate the effects of either normoxic or hypoxic recovery condition on post-exercise hemodynamics after sprint interval leg cycling exercise rather than hemodynamics during exercise. The participants performed five sets of leg cycling with a maximal effort (30 s exercise for each set) with a 4-min recovery of unloaded cycling between the sets in hypoxia [fraction of inspired oxygen (FiO2) = 0.145]. The load during pedaling corresponded to 7.5% of the individual's body weight at the first set, and it gradually reduced from 6.5 to 5.5%, 4.5, and 3.5% for the second to fifth sets. After exercise, the participants rested in a sitting position for 30 min under normoxia (room-air) or hypoxia. Mean arterial pressure decreased over time during recovery (p < 0.001) with no condition and interaction effects (p > 0.05). Compared to pre-exercise values, at 30 min after exercise, mean arterial pressure decreased by 5.6 ± 4.8 mmHg (mean ± standard deviation) during hypoxic recovery, and by 5.3 ± 4.6 mmHg during normoxic recovery. Peripheral arterial oxygen saturation (SpO2) at all time points (5, 10, 20, and 30 min) during hypoxic recovery was lower than during normoxic recovery (all p < 0.05). The area under the hyperemic curve of tissue oxygen saturation (StO2) at vastus lateralis defined as reperfusion curve above the baseline values during hypoxic recovery was lower than during normoxic recovery (p < 0.05). Collectively, post-exercise hypotension after sprint interval leg cycling exercise was not affected by either normoxic or hypoxic recovery despite marked differences in SpO2 and StO2 during recovery between the two conditions.

Hypoxic-induced resting ventilatory and circulatory responses under multistep hypoxia is related to decline in peak aerobic capacity in hypoxia.

BACKGROUND: Several factors have been shown to contribute to hypoxic-induced declined in aerobic capacity. In the present study, we investigated the effects of resting hypoxic ventilatory and cardiac responses (HVR and HCR) on hypoxic-induced declines in peak oxygen uptake ([Formula: see text]O2peak). METHODS: Peak oxygen uptakes was measured in normobaric normoxia (room air) and hypoxia (14.1% O2) for 10 young healthy men. The resting HVR and HCR were evaluated at multiple steps of hypoxia (1 h at each of 21, 18, 15 and 12% O2). Arterial desaturation (ΔSaO2) was calculate by the difference between SaO2 at normoxia-at each level of hypoxia (%). HVR was calculate by differences in pulmonary ventilation between normoxia and each level of hypoxia against ΔSaO2 (L min-1 %-1 kg-1). Similarly, HCR was calculated by differences in heart rate between normoxia and each level of hypoxia against ΔSaO2 (beats min-1 %-1). RESULTS: [Formula: see text]O2peak significantly decreased in hypoxia by 21% on average (P < 0.001). HVR was not associated with changes in [Formula: see text]O2peak. ΔSaO2 from normoxia to 18% or 15% O2 and HCR between normoxia and 12% O2 were associated with changes in [Formula: see text]O2peak (P < 0.05, respectively). The most optimal model using multiple linear regression analysis found that ΔHCR at 12% O2 and ΔSaO2 at 15% O2 were explanatory variables (adjusted R2 = 0.580, P = 0.02). CONCLUSION: These results suggest that arterial desaturation at moderate hypoxia and heart rate responses at severe hypoxia may account for hypoxic-induced declines in peak aerobic capacity, but ventilatory responses may be unrelated.

Effects of carbohydrate-electrolyte dissolved alkaline electrolyzed water on physiological responses during exercise under heat stress in physically active men.

Purpose: This study investigated the effects of 1400 mL intake of alkaline electrolyzed water (AEW) or purified water (PW) into which carbohydrate-electrolyte (CE) was dissolved on improving physiological responses during exercise under heat stress. Methods: This double-blinded, crossover randomized controlled trial included 10 male participants who completed two exercise trials in a hot environment (35 °C, ambient temperature, and 50% relative humidity) after consuming CE-dissolved PW (P-CE) or CE-dissolved AEW (A-CE). The exercise trial consisted of running for 30 min on a treadmill (at an intensity corresponding to 65% of heart rate reserve adjusted for heat stress conditions) and repeated sprint cycling (10 × 7-s maximal sprint cycling), with a 35-min rest interval between the two exercises, followed by a 30-min post-exercise recovery period. Before and after running, and after cycling, the participants drank P-CE (hydrogen concentration of 0 ppm, pH 3.8) or A-CE (0.3 ppm, pH 4.1). Blood samples were obtained before, during (rest interval between running and cycling), and post-exercise. Results: Repeated sprint performance and oxidative stress response did not differ between the P-CE and A-CE trials. A-CE consumption significantly attenuated the increase in blood lactate concentration during the running exercise but not during repeated sprint cycling under heat stress conditions. Conclusion: Our findings suggested that A-CE did not significantly affect repeated sprint performance; however, the attenuated elevation in blood lactate by A-CE ingestion implies a partial enhancement of endurance performance during submaximal exercise under heat stress.

Association of arterial properties with left ventricular morphology and function in the community.

OBJECTIVES: Arterial structural and functional remodeling is recognized as a key determinant of incident heart failure, although the contribution of arterial properties on left ventricular (LV) remodeling is not fully studied. Aortic dilatation is an early manifestation of arterial remodeling and estimated pulse wave velocity (ePWV) is emerging as a simple measure of arterial stiffness. This study aimed to characterize the association of aortic size and ePWV with LV morphology and function. METHODS: The study cohort consisted of 539 participants without overt cardiac disease who underwent extensive cardiovascular examination. Aortic root diameter was measured by two-dimensional echocardiography and ePWV was calculated from a regression equation using age and mean blood pressure. LV global longitudinal strain (LVGLS) was obtained by speckle-tracking echocardiography. RESULTS: Aortic root diameter and ePWV were correlated with LV mass index and LVGLS, while only ePWV was related to E / e' ratio. In multivariable analysis, aortic root diameter and ePWV were significantly related to LV mass index and LVGLS (all P  < 0.05), and the association of aortic root size and ePWV with LVGLS was independent of LV mass index and E / e' ratio. Individuals with both aortic root enlargement and increased ePWV had significantly larger LV mass index and reduced LVGLS compared with those either or those with normal aortic size and ePWV (both P  < 0.05). CONCLUSION: Aortic root size and ePWV were independently associated with unfavorable LV remodeling in individuals free of cardiac disease, which might provide useful information into the pathogenesis-linking arterial remodeling and heart failure.

Alternating work posture improves postprandial glucose response without reducing computer task performance in the early afternoon.

In the workplace, sit-stand workstations are being installed to reduce excessive sitting time and the consequent risk factors for cardiovascular ailments (e.g., postprandial hyperglycemia). However, a prolonged standing posture also has detrimental effects in terms of musculoskeletal symptoms and work efficiency. We thus investigated whether alternating between a sitting and standing work posture improves postprandial glucose response and computer task performance. Nine healthy young males completed 4 × 20-min computer tasks in the early afternoon (i.e., 30 min after eating lunch) under three different work conditions, had no change in posture (only sitting=the control trial, CON), and engaged in two styles of alternating between sitting and standing every 20 min (sitting â†’ standing â†’ sitting â†’ standing, SIT-STAND; standing â†’ sitting â†’ standing â†’ sitting, STAND-SIT). For the computer tasks, all participants had to subtract a two-digit number from a four-digit number and to input the answer in the answer column on the computer. Task performance was evaluated as the number of achievements and accuracy rate every 20 min. Blood glucose concentration was assessed before, immediately after, 30 min, 52 min, 74 min, 96 min, and 118 min after eating lunch. The number of achievements and accuracy rate did not differ among the three trials. The total area under the curve (AUC) for blood glucose concentration was significantly lower in the SIT-STAND and STAND-SIT trials compared with CON, whereas no significant difference was observed between the SIT-STAND and STAND-SIT trials. In conclusion, alternating between a sitting and standing work posture attenuated postprandial blood glucose accumulation without reducing task performance, irrespective of the order of changes in work posture.

Cardiorespiratory Response and Power Output During Submaximal Exercise in Normobaric Versus Hypobaric Hypoxia: A Pilot Study Using a Specific Chamber that Controls Environmental Factors.

Takezawa, Toshihiro, Shohei Dobashi, and Katsuhiro Koyama. Cardiorespiratory response and power output during submaximal exercise in normobaric versus hypobaric hypoxia: a pilot study using a specific chamber that controls environmental factors. High Alt Med Biol. 22: 201-208, 2021. Background: Many previous studies have examined hypoxia-induced physiological responses using various conditions, e.g., artificially reduced atmospheric oxygen concentration [normobaric hypoxia (NH) condition] or low barometric pressure at a mountain [hypobaric hypoxia (HH) condition]. However, when comparing the results from these previous studies conducted in artificial NH and HH including real high altitude, we must consider the possibility that environmental factors, such as temperature, humidity, and fraction of inspired carbon dioxide, might affect the physiological responses. Therefore, we examined cardiorespiratory responses and exercise performances during low- to high-intensity exercise at a fixed heart rate (HR) in both NH and HH using a specific chamber where atmospheric oxygen concentration and barometric pressure as well as the abovementioned environmental factors were precisely controlled. Methods: Ten well-trained university students (eight males and two females) performed the exercise test consisting of two 20-minute submaximal pedaling at the intensity corresponding to 50% (low) and 70% (high) of their HR reserve, under three conditions [NH (fraction of inspired oxygen, 0.135; barometric pressure, 754 mmHg), HH (fraction of inspired oxygen, 0.209; barometric pressure, 504 mmHg), and normobaric normoxia (NN; fraction of inspired oxygen, 0.209; barometric pressure, 754 mmHg)]. Peripheral oxygen saturation (SpO2) to estimate arterial oxygen saturation and partial pressure of end-tidal carbon dioxide (PETCO2) were monitored throughout the experiment. Results: SpO2, PETCO2, and power output at fixed HRs (i.e., pedaling efficiency) in NH and HH were all significantly lower than those in NN. Moreover, high-intensity exercise in HH induced greater decreases in SpO2 and power output than did high-intensity exercise in NH (NH vs. HH; SpO2, 78.2% ± 5.0% vs. 75.1% ± 7.1%; power output, 120.7 ± 24.9 W vs. 112.4 ± 23.2 W, both p < 0.05). However, high-intensity exercise in HH induced greater increases in PETCO2 than did high-intensity exercise in NH (NH vs. HH; 54.2 ± 5.9 mmHg vs. 57.2 ± 3.4 mmHg, p < 0.01). Conclusions: These results suggest that physiological responses and power output at a fixed HR during hypoxic exposure might depend on the method used to generate the hypoxic condition.

The effects of ingestion of hydrogen-dissolved alkaline electrolyzed water on stool consistency and gut microbiota: a double-blind randomized trial.

A relationship between Bifidobacterium and defecation has previously been reported. Our hypothesis on the effectiveness of alkaline electrolyzed water (AEW) proposes that ingestion of AEW, considered possessing antioxidative properties, increases the number of Bifidobacteria and improves stool hardness and gastrointestinal symptoms. A double-blind, randomized study was conducted to evaluate the connection between stool consistency and change in gut microbiota composition induced by drinking hydrogen-dissolved AEW. The participants drank 500 mL of purified tap water or AEW every day for 2 weeks. In this study, drinking AEW did not drastically change gut microbiota, but it appeared to act on a specific bacterial species. Drinking AEW was confirmed to cause an increase in Bifidobacterium. The AEW group also saw stool consistency significantly converge to Bristol stool scale Type 4 ("normal"). Therefore, it is highly likely that the gut microbiota will be changed by drinking AEW. This study was retrospectively registered in University Hospital Medical Information Network (UMIN) Clinical Trials Registry (UMIN ID: UMIN000039507) on February 18, 2020, and was approved by the Ethics Committee of University of Yamanashi (approval No. H30-25) on January 9, 2018.

Biomechanical Analysis of Serious Neck Injuries Resulting from Judo.

To establish a basis for initial diagnosis and for proposing preventive measures for the serious neck injuries occasionally experienced by judo practitioners, the biomechanical mechanisms of these injuries were analyzed. Two male judo experts repeatedly threw an anthropomorphic test device (POLAR dummy) using three throwing techniques (Seoi-nage, Osoto-gari, and Ouchi-gari). The dummy's kinematic data were captured using a high-speed digital camera, and the load and moment of the neck were measured with load cells. The neck injury criterion (Nij) and beam criterion were also calculated. In Seoi-nage, the anterior and parietal regions of the dummy's head contacted the tatami (judo mat). Subsequently, most of the body weight was applied, with the neck experiencing the highest compression. However, in Osoto-gari and Ouchi-gari, the occipital region of the dummy's head contacted the tatami. Significantly higher values of both Nij (median 0.68) and beam criterion (median 0.90) corresponding to a 34.7% to 37.1% risk of neck injury with an abbreviated injury scale score ≥2 were shown in Seoi-nage than in either Ouchi-gari or Osoto-gari. In judo, when thrown by the Seoi-nage technique, serious neck injuries can occur as a result of neck compression that occurs when the head contacts the ground.

Exogenous parathyroid hormone attenuates ovariectomy-induced skeletal muscle weakness in vivo.

Osteoporosis commonly affects the elderly and is associated with significant morbidity and mortality. Loss of bone mineral density induces muscle atrophy and increases fracture risk. However, muscle lipid content and droplet size are increased by aging and mobility impairments, inversely correlated with muscle function, and a cause of reduced motor function. Teriparatide, the synthetic form of human parathyroid hormone (PTH) 1-34, has been widely used to treat osteoporosis. Although PTH positively affects muscle differentiation in vitro, the precise function and mechanisms of muscle mass and power preservation are still poorly understood, especially in vivo. In this study, we investigated the effect of PTH on skeletal muscle atrophy and dysfunction using an ovariectomized murine model. Eight-week-old female C57BL/6J mice were ovariectomized or sham-operated. Within each surgical group, the mice were divided into PTH injection or control subgroups. Motor function was evaluated based on grip strength, treadmill running, and lactic acid concentration. PTH receptor was expressed in skeletal muscle cells and myoblasts. PTH inhibited ovariectomy-induced bone loss but not uterine atrophy or increased body weight; PTH not only abolished ovariectomy-induced reduction in grip strength and maximum running speed, but also significantly reduced the ovariectomy-induced increase in lactic acid concentration (compared with that observed in the vehicle control). PTH also abrogated the ovariectomy-induced reduction in the oxidative capacity of muscle fibers, their cross-sectional area, and intramyocellular lipid content, and induced cell proliferation, cell migration, and muscle differentiation, while reducing lipid secretion by C2C12 myoblasts via the Wnt/ß-catenin pathway. PTH significantly ameliorated muscle weakness and attenuated exercise-induced lactate levels in ovariectomized mice. Our in vitro study demonstrated that PTH/Wnt signaling regulated the proliferation, migration, and differentiation of myoblasts and also reduced lipid secretion in myoblasts. Thus, PTH could regulate several aspects of muscle function and physiology, and may represent a novel therapeutic strategy for patients with osteoporosis.

Hydrogen-rich water suppresses the reduction in blood total antioxidant capacity induced by 3 consecutive days of severe exercise in physically active males.

Repeated sprint exercise can interfere with intramuscular redox balance and cause systemic oxidative stress and muscle damage. There is growing evidence that molecular hydrogen counteracts oxidative and/or inflammatory responses. Therefore, we investigated the effects of molecular hydrogen-rich water (HW) on muscle performance and oxidative stress markers induced by strenuous exercise. A single-blind, crossover, randomized controlled trial has been designed. Eight male volunteers completed two 3-day consecutive exercise tests under two conditions: HW and placebo water (PW). The exercise test included a countermovement jump, maximal voluntary isometric contraction of knee extensors, and sprint cycling. The sprint cycling exercise was comprised three repetitions of 10-second maximal pedaling against a resistance of 7.5% body mass and 110-second active rest (no-load pedaling). Before and after the exercise test, participants drank the 500 mL of HW (5.14 ± 0.03 ppm in H2 concentration) or PW (0.00 ± 0.00 ppm). At 7 hours before the first exercise test (Day 1), as baseline, and 16 hours after the exercise test on each day, blood samples were obtained. Exercise performances in both conditions were not significantly different over 3 consecutive days. In PW trial, relative changes in biological antioxidant potential/diacron-reactive oxygen metabolites, as an index of systemic antioxidant potential, from baseline gradually decreased as the day passed. However, HW suppressed the reduction in biological antioxidant potential/diacron-reactive oxygen metabolites observed in PW. Drinking HW contributed to the maintenance of the redox status during consecutive days of strenuous exercise and might help prevent accumulative muscular fatigue. The study was approved by the Human Research Ethics Committee of the University of Yamanashi, Japan (approval No. H26-008) on December 17, 2014.