Acute effects of caffeine supplementation on kinematics and kinetics of sprinting.

We investigated the acute effects of caffeine supplementation (6 mgï½¥kg-1 ) on 60-m sprint performance and underlying components with a step-to-step ground reaction force measurement in 13 male sprinters. After the first round sprint as a control, caffeine supplementation-induced improvement in 60-m sprint times (7.811 s at the first versus 7.648 s at the second round, 2.05%) were greater compared with the placebo condition (7.769 s at the first versus 7.768 s at the second round, 0.02%). Using average values for every four steps, in the caffeine condition, higher running speed (all six step groups), higher step frequency (5th-16th and 21st-24th step groups), shorter support time (all the step groups except for 13th-16th step) and shorter braking time (9th-24th step groups) were found. Regarding ground reaction forces variables, greater braking mean force (13th-19th step group), propulsive mean force (1st-12th and 17th-20th step groups), and effective vertical mean force (9th-12th step group) were found in the caffeine condition. For the block clearance phase at the sprint start, push-off and reaction times did not change, while higher total anteroposterior mean force, average horizontal external power, and ratio of force were found in the caffeine condition. These results indicate that, compared with placebo, acute caffeine supplementation improved sprint performance regardless of sprint sections during the entire acceleration phase from the start through increases in step frequency with decreases in support time. Moreover, acute caffeine supplementation promoted increases in the propulsive mean force, resulting in the improvement of sprint performance.

Influence of Smoking and Alcohol Habits on Symptoms of Acute Mountain Sickness on Mount Fuji: A Questionnaire Survey-Based Pilot Study.

Horiuchi, Masahiro, Satomi Mitsui, and Tadashi Uno. Influence of smoking and alcohol habits on symptoms of acute mountain sickness on Mount Fuji: a questionnaire survey-based pilot study. High Alt Med Biol 00:000-000, 2024. Background: Acute cigarette smoking or alcohol intake would cause opposing vasculature effects that may influence acute mountain sickness (AMS). The present study aimed to investigate the effects of smoking and alcohol consumption behaviors, and acute smoking and consuming alcohol during ascent on AMS on Mount Fuji. Methods: This questionnaire survey study included 887 participants who climbed Mount Fuji and obtained information regarding sex, age, and smoking and alcohol habits, including behavior during ascent. Results: AMS prevalence was 45% for all participants. A univariate analysis revealed that younger participants (20-29 years) were associated with increased AMS prevalence (effect size [ES] = 0.102, p = 0.057) and severity (ES = 0.18, p = 0.01). A prediction model using multiple logistic regression indicated that several factors influenced AMS risk: younger age (p = 0.001), daily smoking habits (p = 0.021), no smoking (p = 0.033), or alcohol consumption during ascent (p = 0.096). Alcohol consumption during ascent had no effect on the increased AMS risk in younger participants (20-29 years), while alcohol consumption during ascent increased AMS risk for middle-age participants (50-59 years). Conclusion: Younger individuals are more likely to experience AMS. Smoking habits are associated with an increased AMS risk. It may be recommended that middle-aged climbers should ascend without consuming alcohol.

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.

Effects of intermittent exercise during prolonged sitting on executive function, cerebrovascular, and psychological response: a randomized crossover trial.

Emerging evidence indicates that acute bouts of uninterrupted prolonged sitting decrease cerebral blood flow and impair executive function. Few studies have investigated the use of feasible sedentary behavior interruptions to attenuate these effects. This study aimed to investigate the effects of intermittent half-squat exercises during prolonged sitting on executive function. Twenty participants (45% women, 21 ± 1 yr) were randomized to sit for 3 h 1) without any interruptions (control) or 2) with 1 min half-squats every 20 min (exercise). Executive function was determined using the Color Word Stroop Test (CWST) and Trail Making Test-B (TMT-B). Subjective feelings of arousal and measures of fatigue, concentration, and motivation were evaluated. Internal carotid artery (ICA) blood flow was measured using Doppler ultrasound. There was a significant interaction effect for correct response times with the incongruent CWST (P < 0.01), which were 3.5% faster in the exercise and 4.2% slower in the control over 3 h of sitting. There was also a significant interaction effect for TMT-B completion times (P < 0.01), which were 10.0% faster in the exercise and 8.8% slower in the control. Exercise suppressed decreases in concentration with a significant interaction effect (-28.7% vs. -9.2% for control vs. exercise, P = 0.048) and increases in mental fatigue with a significant interaction effect (285% vs. 157% for control vs. exercise, P < 0.04). These changes may have been related to changes in ICA blood flow, which had a significant interaction effect (P = 0.087). These results suggest that a simple strategy like intermittent squat exercises could help to maintain executive function during prolonged sitting.NEW & NOTEWORTHY We assessed executive function, cardiovascular, and cerebrovascular responses during 3-h prolonged sitting, with or without an exercise interruption (1 min squats every 20 min). Compared to uninterrupted sitting, exercise interruption suppressed sitting-induced reductions in cerebral blood flow and impairments in executive function. These results demonstrated the efficacy of a half-squat intervention for individuals seeking to preserve cognition during prolonged sitting, which may be useful in environments with limited resources such as the workplace.

Normalized economical speed is influenced by aging and not by exercise habituation.

OBJECTIVE: A U-shaped relationship between energy cost of walking (Cw) and walking speed indicates that there is a specific speed minimizing the Cw, called economical speed (ES). It is mostly slower in older adults than young adults; however, effects of leg length on the ES have been ignored. We investigated effects of aging and exercise habituation on the normalized ES by leg length (ESnormalized). We quantified time delay of stride length and step frequency in sedentary young (SY), active young (AY), and active elderly (AE) adults in response to sinusoidal gait speed change at 30-s and 180-s periods with an amplitude of ± 0.56 mï½¥s- 1. RESULTS: The ES was significantly slower in the following sequence: AE, SY, and AY, whereas ESnormalized was slower in the AE than in other young groups, with no difference between AY and SY. AE and SY showed greater step variabilities at the 180-s period, whereas AY showed relatively smaller step variabilities at both periods. Collectively, the ESnormalized slowed due to aging, not due to exercise habituation. When optimizing the appropriate SL-SF combination for sinusoidal speed changes, young and elderly adults may adopt different strategies. Exercise habituation may reduce step variabilities in young adults.

Alterations in step frequency and muscle activities using body weight support influence the ventilatory response to sinusoidal walking in humans.

The use of body weight support (BWS) can reveal important insights into the relationship between lower-limb muscle activities and the ventilatory response during sinusoidal walking. Here, healthy participants (n = 15) walked on a treadmill while 0%, 30%, and 50% of their body weight was supported with BWS. The walking speed was varied sinusoidally between 3 and 6 km h-1, and three different frequencies, and periods ranging from 2 to 10 min were used. Breath-by-breath ventilation ([Formula: see text]) and CO2 output ([Formula: see text]) were measured. The tibialis anterior (TA) muscle activity was measured by electromyography throughout the walking. The amplitude (Amp), normalized Amp [Amp ratio (%)], and phase shift (PS) of the sinusoidal variations in measurement variables were calculated using a Fourier analysis. The results revealed that the Amp ratio in [Formula: see text] increased with the increase in BWS. A steeper slope of the [Formula: see text]-[Formula: see text] relationship and greater [Formula: see text]/[Formula: see text] values were observed under reduced body weight conditions. The Amp ratio in TA muscle was significantly positively associated with the Amp ratio in the [Formula: see text] (p < 0.001). These findings indicate that the greater amplitude in the TA muscle under BWS may have been a potent stimulus for the greater response of ventilation during sinusoidal walking.

Gait variability of interlimb coordination in high-heeled shoes with detachable base sockets under conditions of sinusoidal speed change.

BACKGROUND: This study aimed to investigate the effects of wearing high-heeled shoes (HHS) on gait variability of the lower limbs when the treadmill speed was sinusoidally changed. METHODS: A total of 17 young females walked on a treadmill with HHS, HHS with detachable base sockets (HHS-Sockets), and low-heeled shoes (LHS) under sinusoidal speed-changing protocol of 60-s and 30-s periods with an amplitude of ± 0.56 m·s-1. The time course of the joint elevation angles of the thigh, shank, and foot in one gait cycle can be well approximated like a plane in a triaxial space, so-called intersegmental coordination (IC). Standard deviation of the plane (IC thickness) was considered as the anteroposterior gait variability when the best-fitting plane of the angular covariation was obtained. The lateral gait variability was the coefficient of variance of step width (CVSW). To examine whether the gait parameters was associated with IC thickness, a sum of the time delay of the stride length and step frequency (TDSL+SF) against sinusoidal speed change was calculated. RESULTS: The IC thickness was not different across shoe conditions and periods. The CVSW was greater in the HHS and HHS-Sockets conditions than in the LHS condition. TDSL+SF was greater in the HHS condition than in the LHS and HHS-Sockets conditions at both periods; however, it was not correlated with IC thickness. SIGNIFICANCE: Walking with HHS increased lateral gait variability at faster speed-changing situation, but not anteroposterior gait variability. Detachable sockets expanding the base area ten times greater than that of HHS could reduce TDSL+SF; however, TDSL+SF could not explain the IC thickness.

Greater post-exercise hypotension in healthy young untrained men after exercising in a hot compared to a temperate environment.

This research examined the effects of exercising in a hot compared to a temperate environment on post-exercise hemodynamics in untrained men. We hypothesized exercise in a hot compared to a temperate environment would elicit greater post-exercise hypotension, and this would be attributable to higher cutaneous vascular conductance and sweat loss, and lower heart rate variability (HRV) and cardiac baroreflex sensitivity (cBRS). In a randomized counterbalanced order, 12 untrained healthy men completed two trials involving 40-min leg-cycling exercise at either 23 °C (CON) or 35 °C (HOT). Post-exercise participants rested supine for 60 min at 23 °C whilst hemodynamic and thermoregulatory measurements were assessed. Post-exercise hypotension was greater after exercising in a hot than a temperate environment as indicated by a lower mean arterial pressure at 60 min recovery (CON 83 ± 5 mmHg, HOT 78 ± 5 mmHg, Mean difference [95% confidence interval], -5 [-8, -3] mmHg). Throughout recovery, cutaneous vascular conductance was higher, and cBRS and HRV were lower after exercising in a hot than in a temperate environment (P < 0.05). Sweat loss was greater on HOT than on CON (P < 0.001). Post-exercise hypotension after exercising in the hot environment was associated with sweat loss (r = 0.66, P = 0.02), and changes in cutaneous vascular conductance (r = 0.64, P = 0.03), and HRV (Root mean square of the successive difference in R-R interval [RMSSD]) r=0.75, P = 0.01 and and log high frequency [HF] r=0.66, P = 0.02), but not cBRS (all, r ≤ 0.2, P > 0.05). Post-exercise hypotension was greater after exercise in a hot compared to a temperate environment and may be partially explained by greater sweat loss and cutaneous vascular conductance, and lower HRV.

Effects of processing methods on the aroma constituents of hihatsumodoki (Piper retrofractum Vahl).

Hihatsumodoki (Piper retrofractum Vahl) is a traditional spice from Okinawa (Japan) that can be processed in different ways to create the desired flavor. Herein, we examined the effects of processing (sun-drying, oven-drying, roasting, and steaming) on the volatile aroma constituents of hihatsumodoki fruits. Among the 106 chromatographic peaks observed in total, 58 were assigned to known aroma compounds. The relative contents of terpenes, for example, linalool, ß-caryophyllene, α-caryophyllene, and germacrene D, ranged from 57.6% to 88.1%. Sun-drying decreased the content of aldehydes such as hexanal and trans-2-hexenal but did not significantly affect the total content of aroma compounds. The amount of aroma compounds released during oven-drying and roasting increased with temperature up to a certain point (90°C) and decreased at an excessively high temperature of 180°C. High-temperature roasting generated Maillard reaction products such as furans and furanones, which could impart sweet caramel odors. Steamed fruits had the lowest content of aroma compounds, which was ascribed to the loss of these compounds to vapor. Meanwhile, drying steamed fruits resulted in an approximately 3.6-fold increase in their aroma compound content, and the content of sesquiterpenes in the steamed-dried fruits was similar to that in fruits exposed to high temperatures. The effects of processing on aroma quality were visualized using multivariate statistical analysis. The aroma characteristics of roasted (180°C), steamed, and steamed-dried fruits were different from those of the control. The combined findings provide useful information for the selection of processing methods to achieve the desired flavor of hihatsumodoki. Practical Application: This study reveals the effects of different processing methods on the aroma profile of hihatsumodoki (Piper retrofractum Vahl), a subtropical spice from Okinawa (Japan). The results facilitate the selection of preferred hihatsumodoki flavors for household and industrial applications in foods and beverages. In addition, they inspire research on the processing-induced flavor changes of other tropical or subtropical spices.

The effect of four weeks blood flow restricted resistance training on macro- and micro-vascular function in healthy, young men.

PURPOSE: To determine the macrovascular and microvascular function responses to resistance training with blood flow restriction (BFR) compared to high-load resistance training (HLRT) control group. METHODS: Twenty-four young, healthy men were randomly assigned to BFR or HLRT. Participants performed bilateral knee extensions and leg presses 4 days per week, for 4 weeks. For each exercise, BFR completed 3 X 10 repetitions/day at 30% of 1-repetition max (RM). The occlusive pressure was applied at 1.3 times of individual systolic blood pressure. The exercise prescription was identical for HLRT, except the intensity was set at 75% of one repetition maximum. Outcomes were measured pre-, at 2- and 4-weeks during the training period. The primary macrovascular function outcome was heart-ankle pulse wave velocity (haPWV), and the primary microvascular function outcome was tissue oxygen saturation (StO2) area under the curve (AUC) response to reactive hyperemia. RESULTS: Knee extension and leg press 1-RM increased by 14% for both groups. There was a significant interaction effect for haPWV, decreasing - 5% (Δ-0.32 m/s, 95% confidential interval [CI] - 0.51 to - 0.12, effect size [ES] = - 0.53) for BFR and increasing 1% (Δ0.03 m/s, 95%CI - 0.17 to 0.23, ES = 0.05) for HLRT. Similarly, there was an interaction effect for StO2 AUC, increasing 5% (Δ47%ï½¥s, 95%CI - 3.07 to 98.1, ES = 0.28) for HLRT and 17% (Δ159%ï½¥s, 95%CI 108.23-209.37, ES = 0.93) for BFR group. CONCLUSION: The current findings suggest that BFR may improve macro- and microvascular function compared to HLRT.

Different Influencing Factors for Risk of Falls Between Men and Women while Descending from Mount Fuji.

INTRODUCTION: Annually, approximately 250,000 people climb Mount Fuji in Japan. Nonetheless, only few studies have examined the prevalence of falls and related factors on Mount Fuji. METHODS: We conducted a questionnaire survey of 1061 participants (703 men and 358 women) who had climbed Mount Fuji. The following information was collected: age, height, body weight, luggage weight, experience on Mount Fuji, experience on other mountains, presence or absence of a tour guide, single-day climber or overnight-stay lodger, information on the downhill trail (volcanic gravel, long distance, and the risk of falls), presence or absence of trekking poles, shoe type, shoe sole condition, and fatigue feeling. RESULTS: The fall rate in women (174/358; 49%) was greater than that in men (246/703; 35%). A prediction model using multiple logistic regression (no fall, 0; fall, 1) indicated that the following factors decreased the risk of falls: male sex, younger age, previous experience on Mount Fuji, having information about long-distance downhill trails, wearing hiking shoes or mountaineering boots rather than other types of shoes (eg, running shoes, sneakers) or worn-out shoes, and not feeling fatigued. Additionally, the following factors may decrease the risk of falls in women only: experience hiking on any other mountains, not being part of a guided tour, and using trekking poles. CONCLUSIONS: Women had a higher risk of falls on Mount Fuji than men. Specifically, having less experience on any other mountains, being part of a guided tour, and nonuse of trekking poles may relate to higher risks of falls in women. These results suggest that different precautionary measures for men and women are useful.

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.

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.

How emotional changes affect skin odor and its impact on others.

The gas emanating from human skin is known to vary depending on one's physical condition and diet. Thus, skin gas has been gaining substantial scholarly attention as an effective noninvasive biomarker for understanding different physical conditions. This study focuses on the relationship between psychological stress and skin gas, which has remained unclear to date. It has been deduced that when participants were subjected to interviews confirmed as stressful by physiological indicators, their skin emitted an odor similar to stir-fried leeks containing allyl mercaptan and dimethyl trisulfide. This characteristic, recognizable odor appeared reproducibly during the stress-inducing situations. Furthermore, the study deduced that individuals who perceive this stress odor experience subjective tension, confusion, and fatigue (Profile of Mood States scale). Thus, the study findings indicate the possibility of human nonverbal communication through odor, which could enhance our understanding of human interaction.

Effects of exercise habituation and aging on the intersegmental coordination of lower limbs during walking with sinusoidal speed change.

BACKGROUND: The time courses of the joint elevation angles of the thigh, shank, and foot in one stride during walking can be well approximated by a "plane" in a triaxial space. This intersegmental coordination (IC) of the lower limb elevation angles is referred to as the planar covariation law. We examined the effects of exercise habituation and aging on the thickness of the IC plane of the lower limbs under sinusoidal speed changing conditions. METHODS: Seventeen sedentary young (SY), 16 active young (AY), and 16 active elderly (AE) adults walked on a treadmill in accordance with a sinusoidal speed changing protocol at 120, 60, and 30 s periods with an amplitude of ± 0.56 m·s-1. Motion of the lower limbs from the sagittal direction was recorded to calculate the elevation angles of the lower limbs. When the best-fit IC plane was determined, the smallest standard deviation of the IC plane was considered as the anteroposterior gait variability of the lower limbs. The coefficient of variance of the step width was also quantified to evaluate the lateral step variability (CVSW). RESULTS: The standard deviation of the IC plane was significantly greater in the order of SY, AY, and AE, regardless of the sinusoidal wave periods of the changing speed. The CVSW was not significantly different among the three groups. CONCLUSIONS: Exercise habituation influences anteroposterior gait variability of the lower limbs, but not lateral step variability, even in young adults. Given these, gait adaptability for sinusoidal speed changes does not always decline with aging. TRIAL REGISTRATION: UMIN000031456 ( R000035911 ; registered February 23, 2018).

Blood glucose responses are associated with prolonged sitting-induced changes in arterial stiffness: a randomized crossover trial.

OBJECTIVE: To determine whether the vascular dysfunction response to prolonged sitting combined with hyperglycemia can be mitigated with simple and feasible sitting interruption exercises. METHODS: Twenty healthy young adults [50% women, 21 (2) years, BMI of 21.5 (1.6) kg/m 2 ; (SD)] were enrolled in this study. This study included two 3-h prolonged sitting conditions: uninterrupted sitting (CON) and interruptions with 1-min light half-squat exercises every 20 min (EX). In both conditions, participants ingested 75-g glucose before sitting. The primary outcome was brachial-ankle pulse wave velocity (baPWV). RESULTS: Linear mixed-effects model analysis revealed a significant interaction effect for baPWV, with a 25% (4.7 m/s) increase for CON and a 1.3% (0.22 m/s) increase for EX. There was also an interaction effect for glucose, with a 60% (57 mg/dl) for CON and a 41% (39 mg/dl) increase for EX. Repeated measures correlation revealed a negligible association between glucose and baPWV for CON ( r = -0.04) and a small association for EX ( r = 0.32). CONCLUSION: Vascular dysfunction occurred for the control but not the exercise condition, suggesting interrupting prolonged sitting with regular, short bouts of exercise may be an effective strategy to protect vascular health.

Influence of Step Frequency on the Dynamic Characteristics of Ventilation and Gas Exchange During Sinusoidal Walking in humans.

We tested the hypothesis that restricting either step frequency (SF) or stride length (SL) causes a decrease in ventilatory response with limited breath frequency during sinusoidal walking. In this study, 13 healthy male and female volunteers (mean ± SD; age: 21.5 ± 1.8 years, height: 168 ± 7 cm, weight: 61.5 ± 8.3 kg) participated. The walking speed was sinusoidally changed between 50 and 100 m⋅min-1 with periods from 10 to 1 min. Using a customized sound system, we fixed the SF at 120 steps⋅min-1 with SL variation (0.83-0.41 m) (SF fix ) or fixed the SL at 0.7 m with SF variation (143-71 steps⋅min-1) (SL fix ) during the subjects' sinusoidal walking. Both the subjects' preferred locomotion pattern without a sound system (Free) and the unprompted spontaneous locomotor pattern for each subject (Free) served as the control condition. We measured breath-by-breath ventilation [tidal volume (VT) and breathing frequency (Bf)] and gas exchange [CO2 output ( V . CO2), O2 uptake ( V . O2)]. The amplitude (Amp) and the phase shift (PS) of the fundamental component of the ventilatory and gas exchange variables were calculated. The results revealed that the SF fix condition decreased the Amp of the Bf response compared with SL fix and Free conditions. Notably, the Amp of the Bf response under SF fix was reduced by less than one breath at the periods of 5 and 10 min. In contrast, the SL fix condition resulted in larger Amps of Bf and V . E responses as well as Free. We thus speculate that the steeper slope of the V . E - V . CO2 relationship observed under the SL fix might be attributable to the central feed-forward command or upward information from afferent neural activity by sinusoidal locomotive cadence. The PSs of the V . E , V . O2, and V . CO2 responses were unaffected by any locomotion patterns. Such a sinusoidal wave manipulation of locomotion variables may offer new insights into the dynamics of exercise hyperpnea.

Production of Hydroxy Fatty Acids, Precursors of γ-Hexalactone, Contributes to the Characteristic Sweet Aroma of Beef.

Aroma is an essential factor for meat quality. The meat of Japanese Black cattle exhibits fine marbling and a rich and sweet aroma with a characteristic lactone composition. The mechanism of lactone formation associated with beef aroma has not been elucidated. In this study, we examined the precursors of γ-hexalactone, an indicator of the sweet aroma of beef and identified the mechanism underlying γ-hexalactone production. A low-temperature vacuum system was used to prepare beef tallow from Japanese Black cattle and Holstein cattle. The odor components were identified using headspace-gas chromatography. The analysis revealed that γ-hexalactone, γ-dodecalactone, δ-tetradecalactone, and δ-hexadecalactone were present as sweet aroma components of beef tallow prepared from marbling and muscle. Since we previously reported that γ-hexalactone formation correlates with linoleic acid content in beef, we analyzed ten oxidized fatty acids derived from linoleic acid by liquid chromatography-triple quadrupole mass spectrometry and detected two hydroxy-octadecadienoic acids (9S-HODE and 13S-HODE) in beef tallow. Significant differences in arachidonic acid 15-lipoxygenase and cyclooxygenase protein expression levels among subcutaneous fat, intramuscular fat, and muscle tissue were observed. Our results suggest that the combination of linoleic acid and the expression of lipid oxidase derived from beef muscle and intramuscular fat produce hydroxy fatty acids that result in a sweet aroma.

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.

Dietary nitrate supplementation effect on dynamic cerebral autoregulation in normoxia and acute hypoxia.

We tested the hypothesis that increasing the nitric oxide (NO) bioavailability by dietary nitrate would recover the hypoxia-induced reduction in dynamic cerebral autoregulation (CA). Twelve healthy males (age 21 ± 2 years) completed four days of dietary supplementation with a placebo or inorganic nitrate drink (140-ml beetroot juice per day) followed by 60-min of normoxia or hypoxia (fraction of inspired oxygen [FiO2] = 13%). Duplex ultrasonography was used to perform volumetric change-based assessment of dynamic CA in the internal carotid artery (ICA). Dynamic CA was assessed by rate of regulation (RoR) of vascular conductance using the thigh-cuff method. Four days of beetroot supplementation increased circulating nitrate by 208 [171,245] µM (mean difference [95% confidence interval]) compared with placebo. Dynamic CA was lower in hypoxia than normoxia (RoR Δ-0.085 [-0.116, -0.054]). Compared with placebo, nitrate did not alter dynamic CA in normoxia (RoR Δ-0.022 [-0.060, 0.016]) or hypoxia (RoR Δ0.017 [-0.019, 0.053]). Further, nitrate did not affect ICA vessel diameter, blood velocity or flow in either normoxia or hypoxia. Increased bioavailability of NO through dietary nitrate supplementation did not recover the hypoxia-induced reduction in dynamic CA. This suggests the mechanism of hypoxia-induced reduction in dynamic CA does not relate to the availability of NO.