Effects of Short-Term Nighttime Carbohydrate Restriction Method on Exercise Performance and Fat Metabolism.

BACKGROUND: The sleep-low method has been proposed as a way to sleep in a low-glycogen state, increase the duration of low glycogen availability and sleep and temporarily restrict carbohydrates to improve exercise performance. However, long-term dietary restriction may induce mental stress in athletes. Therefore, if it can be shown that the effects of the sleep-low method can be achieved by restricting the carbohydrate intake at night (the nighttime carbohydrate restriction method), innovative methods could be developed to reduce weight in individuals with obesity and enhance athletes' performance with reduced stress and in a shorter duration when compared with those of previous studies. With this background, we conducted a study with the purpose of examining the intervention effects of a short-term intensive nighttime carbohydrate restriction method. METHODS: A total of 22 participants were recruited among university students participating in sports club activities. The participants were assigned at random to groups, including a nighttime carbohydrate restriction group of 11 participants (6 males, 5 females; age 22.3 ± 1.23) who started a carbohydrate-restricted diet and a group of 11 participants (5 males, 6 females; age 21.9 ± 7.9) who continued with their usual diet. The present study had a two-group parallel design. In the first week, no dietary restrictions were imposed on either group, and the participants consumed their own habitual diets. In the second week, the total amount of calories and carbohydrate intake measured in the first week were divided by seven days, and the average values were calculated. These were used as the daily calorie and carbohydrate intakes in the second week. Only the nighttime carbohydrate restriction group was prohibited from consuming carbohydrates after 4:00 p.m. During the two-week study period, all participants ran for one hour each day before breakfast at a heart rate of 65% of their maximum heart rate. RESULTS: The results obtained from young adults participating in sports showed significant differences in peak oxygen consumption (V·O2peak), work rate max, respiratory quotient (RQ), body weight and lean body mass after the intervention when compared with before the intervention in the nighttime carbohydrate restriction group (p < 0.05). CONCLUSIONS: Our findings suggest that the nighttime carbohydrate restriction method markedly improves fat metabolism even when performed for a short period. This method can be used to reduce body weight in individuals with obesity and enhance athletes' performance. However, it is important to consider the intake of nutrition other than carbohydrates.

Effects of Standing after a Meal on Glucose Metabolism and Energy Expenditure.

In the past decade, university students have become more sedentary. A sedentary lifestyle is associated with an increased risk of obesity and cardiovascular disease. Methods that decrease sedentary lifestyles, such as the use of standing desks to increase physical activity, have been extensively examined. However, the effects of postprandial standing and sitting on energy metabolism have not yet been compared. Therefore, the present study investigated the effects of standing after a meal on energy expenditure and glucose metabolism. Ten males participated in the present study. The experiment was initiated with 300 g of rice ingested as a carbohydrate load. The subjects maintained a standing or sitting position for 120 min after the meal. Energy expenditure was calculated from VO2 and VCO2 using the indirect calorimetry method. Glucose metabolism was assessed by measuring blood glucose levels and the exogenous glucose metabolic rate. Energy expenditure through standing after eating was approximately 0.16 ± 0.08 kcal/min higher than that through sitting. Blood glucose dynamics did not significantly differ between the standing and sitting positions. Furthermore, no significant differences were observed in the dynamics of the exogenous glucose metabolic rate between the standing and sitting positions. Standing for 2 h after a meal increased energy expenditure by 10.7 ± 4.6% without affecting glucose metabolism.

Effects of pre-exercise acupuncture stimulation on heart rate response during short-duration exercise.

BACKGROUND: The purpose of the present study was to investigate the effects of bradycardia induced by pre-exercise acupuncture on heart rate responses during short-duration exercise. METHODS: A total of 29 healthy subjects underwent two protocols: protocol 1 assessed the effects of manual acupuncture on heart rate response during rest, and protocol 2 tested the hypothesis that the bradycardic effects induced by pre-exercise acupuncture continue during low- and high-intensity exercise. Their average age, height, weight, and body mass index were 21.2 ± 2.0 years, 167.2 ± 8.8 cm, 63.8 ± 12.8 kg, and 22.7 ± 3.5 kg/m2, respectively. In acupuncture stimulations for protocols 1 and 2, an acupuncture needle was inserted into the lower leg and manual acupuncture stimulation was performed at 1 Hz. RESULTS: In protocol 1 (resting condition), acupuncture stimulation induced a bradycardic response, which continued for 4 min after the cessation of acupuncture stimulation (p < 0.05). In protocol 2, the bradycardic response induced by pre-exercise acupuncture stimulation remained during low-intensity exercise and in the beginning of high-intensity exercise performed immediately after the cessation of acupuncture stimulation (p < 0.05). However, the effects disappeared when post-acupuncture exercise was performed when the heart rate was approximately 140 beats/min during high-intensity exercise. The rating of perceived exertion after exercise differed significantly between the acupuncture stimulation task (7.9 ± 1.6) and no-stimulation task (8.5 ± 2.0) (p = 0.03) only in the low intensity group. CONCLUSION: This study may provide new insights into the effect of acupuncture stimulation on psycho-physiological conditions during exercise.

Low Frequency Severe-Intensity Interval Training Markedly Alters Respiratory Compensation Point During Incremental Exercise in Untrained Male.

This study investigated the effect of low-frequency severe-intensity interval training on the respiratory compensation point (RCP) during incremental exercise test. Eighteen healthy males (age; 20.7 ± 2.2 years, range 18 to 29 years, height; 174.0 ± 5.6 cm, weight; 68.8 ± 13.5 kg) were randomly assigned to an interval training group or a control group. Interval training was conducted once weekly for 3 months. Each session consisted of three bouts of bicycle ergometer exercise at 80% maximum work rate until volitional fatigue. Before (baseline) and after the 3-month intervention, incremental exercise test was performed on a bicycle ergometer for determination of ventilatory threshold (VT), RCP, and peak oxygen consumption (V̇O 2 peak). The training program resulted in significant increases of V̇O 2 peak (+ 14%, p < 0.001, η p 2 = 0.437), oxygen consumption (V̇O 2) at VT (+ 18%, p < 0.001, η p 2 = 0.749) and RCP (+ 15%, p = 0.03, η p 2 = 0.239) during incremental exercise test in the training group. Furthermore, a significant positive correlation was observed between the increase in V̇O 2 peak and increase in V̇O 2 at RCP after intervention (r = 0.87, p = 0.002) in the training group. Tidal volumes at VT (p = 0.04, η p 2 = 0.270) and RCP (p = 0.01, η p 2 = 0.370) also increased significantly after intervention compared to baseline. Low-frequency severe-intensity interval training induced a shift in RCP toward higher work rate accompanied by higher tidal volume during incremental exercise test.

Increase in diastolic blood pressure induced by fragrance inhalation of grapefruit essential oil is positively correlated with muscle sympathetic nerve activity.

Fragrance inhalation of essential oils is widely used in aromatherapy, and it is known to affect blood pressure (BP) and heart rate (HR) via autonomic control of circulation. In this study, we aimed to test the hypothesis that the changes in hemodynamics with fragrance inhalation were observed along with changes in muscle sympathetic nerve activity (MSNA). In study 1, thirteen healthy men were exposed to fragrance stimulation of grapefruit essential oil for 10 min, and BP, HR, and MSNA were continuously measured. In study 2, another nine healthy men were exposed to the same fragrance stimulation; responses in BP and HR were continuously measured, and plasma noradrenaline and cortisol concentrations were determined. We found that diastolic BP increased significantly during fragrance inhalation, while the other variables remained unchanged in both studies. Although MSNA burst frequency, burst incidence, and total activity remained unchanged during fragrance inhalation, we found a significant linear correlation between changes in diastolic BP in the last 5 min of fragrance inhalation and changes in MSNA burst frequency. The plasma cortisol concentration decreased significantly at 10 min of fragrance inhalation, though the noradrenaline concentration remained unchanged. These results suggest, for the first time, that changes in BP with fragrance inhalation of essential oil are associated with changes in MSNA even with decreased stress hormone.

Acupoint dependence of depressor and bradycardic responses elicited by manual acupuncture stimulation in humans.

The cardiovascular effects of the autonomic nervous system (ANS) are modulated by inputs from peripheral sensors and other brain regions. However, it currently remains unknown whether the manual acupuncture (MA) stimulation of different acupuncture points evokes different responses by the heart and vasculature, a phenomenon known as "site specificity". Sixty healthy subjects were randomly divided into a control group and MA stimulation groups at the lower leg, ear, abdomen, and forearm. MA was performed at 1 Hz for 2 min. A depressor response was observed only in the lower leg stimulation group, in which mean blood pressure significantly decreased from 83.4 ± 10.1 to 80.9 ± 11.7 mmHg (p < 0.003). A bradycardic response was elicited in all MA stimulation groups. There was no significant differences in the magnitude of the bradycardic response between groups. MA-induced cardiovascular responses, which may be mediated by the modulation of ANS, differ depending on acupuncture points.

Effects of walking in water on gut hormone concentrations and appetite: comparison with walking on land.

The effects of water exercise on gut hormone concentrations and appetite currently remain unclear. The aim of the present study was to investigate the effects of treadmill walking in water on gut hormone concentrations and appetite. Thirteen men (mean ± s.d. age: 21.6 ± 2.2 years, body mass index: 22.7 ± 2.8 kg/m2, peak oxygen uptake (VO2peak): 49.8 ± 7.8 mL/kg per min) participated in the walking in water and on land challenge. During the study period, ratings of subjective feelings of hunger, fullness, satiety and motivation to eat were reported on a 100-mm visual analog scale. A test meal was presented after walking, and energy intake (EI) was calculated. Blood samples were obtained during both trials to measure glucagon-like peptide-1 (GLP-1), peptide YY (PYY) and acylated ghrelin (AG) concentrations. Hunger scores (How hungry do you feel?) were significantly lower during the water trial than during the land trial (P < 0.05). No significant differences were observed in EI between water and land trials. GLP-1 concentrations were significantly higher in the water trial than in the land trial (P < 0.05). No significant differences were observed in PYY concentrations between water and land trials. AG concentrations were significantly lower in the water trial than in the land trial (P < 0.01). In conclusion, changes in gut hormone concentrations during walking in water contribute to the exercise-induced suppression of appetite and provide novel information on the influence of walking in water on the acute regulation of appetite.

A novel approach for evaluating the effects of odor stimulation on dynamic cardiorespiratory functions.

We aimed to develop a novel method to quantitatively evaluate the effects of odor stimulation on cardiorespiratory functions over time, and to examine the potential usefulness of clinical aromatherapy. Eighteen subjects participated. Nine people were assigned to each of the two resting protocols. Protocol 1: After resting for 2 min in a sitting position breathing room air, the subject inhaled either air or air containing sweet marjoram essential oil from the Douglas bag for 6 min, Protocol 2: After resting for 5 min in a supine position, the subject inhaled the essential oil for 10 min, and then recovered for 10 min breathing room air. All subjects inhaled the essential oil through a face mask attached to one-way valve, and beat-to-beat heart rate (HR) and arterial blood pressure (BP) as well as breath-by-breath respiratory variables were continuously recorded. In both protocols, during fragrance inhalation of the essential oil, time-dependent decrease in mean BP and HR were observed (P<0.05). During post-inhalation recovery, the significant fragrance-induced bradycardic effect lasted at least 5 min (- 3.1 ± 3.9% vs. pre-inhalation baseline value, p<0.05). The mean BP response at the start of odor stimulation was approximated by a first-order exponential model. However, such fragrance-induced changes were not observed in the respiratory variables. We established a novel approach to quantitatively and accurately evaluate the effects of quantitative odor stimulation on dynamic cardiorespiratory functions, and the duration of the effect. This methodological approach may be useful for scientific evaluation of aromatherapy as an approach to integrated medicine, and the mechanisms of action of physiological effects in fragrance compounds.

Electroacupuncture most effectively elicits depressor and bradycardic responses at 1 Hz in humans.

PURPOSE: Acupuncture stimulation is known to act on the autonomic nervous system and elicits depressor and bradycardic effects. However, previous studies on humans did not conduct quantitative analyses on optimal acupuncture conditions such as the stimulation frequency and duration to achieve maximum depressor and bradycardic effects. The aim of the present study was to investigate the effects of varying stimulation frequencies of electroacupuncture on time-dependent changes in blood pressure and heart rate in humans. METHODS: Twelve healthy volunteers participated in the study. An acupuncture needle was inserted at the Ximen acupoint (PC4 according to WHO nomenclature), located at the anterior aspect of the forearm. An electrical stimulation was delivered through the acupuncture needle at an intensity of 1 V, pulse width of 5 ms, and stimulation frequencies of 0.5, 1, 5, and 10 Hz in a random order. The duration of electroacupuncture was 6 min, during which blood pressure and heart rate responses were monitored. RESULTS: Group-averaged data indicated that 1-Hz electroacupuncture decreased blood pressure and heart rate. Blood pressure was significantly decreased from the prestimulation baseline value of 86.6 ± 2.9 to 81.4 ± 2.3 mmHg during 4-6 min of 1-Hz electroacupuncture (mean ± SE, P < 0.01). Heart rate was also significantly decreased (from 66.2 ± 2.0 to 62.7 ± 1.7 beats/min, P < 0.01). CONCLUSIONS: These results provide fundamental evidence that bradycardiac and depressor responses are effectively produced by electrical acupuncture in humans.

Low-frequency severe-intensity interval training improves cardiorespiratory functions.

PURPOSE: The present study investigated the effects of severe-intensity interval training at a frequency of once a week on cardiorespiratory function at rest and during exercise. METHODS: Fourteen young healthy males were randomly assigned to either an interval training group or control group. Cardiorespiratory function was investigated by incremental maximal exercise test and constant work rate submaximal exercise test before and after the intervention period in all subjects. Submaximal exercise test was conducted at two work rates (80% ventilatory threshold (VT) level and 100% VT level plus 50% of the difference between VT and peak oxygen consumption (V˙O2)) for 8 min; the same work rates and duration were used before and after training. Left ventricular adaptations were assessed by echocardiography under supine resting conditions before and after training. In the interval training group, seven subjects performed cycle ergometer training once per week for 3 months. The training consisted of three bouts of exercises to volitional fatigue at 80% maximum work rate. RESULTS: Increased V˙O2max (+13%, P = 0.015), VT (+21%, P = 0.001), and left ventricular posterior wall thickness (+18%, P = 0.002) and reduced minute ventilation (-12%, P = 0.032) and blood lactate concentration (-16%, P = 0.025) during high-intensity exercise were observed after the training program compared with baseline. Although not significant, V˙O2 and cycling economy (V˙O2 per work rate) during high-intensity exercise decreased slightly after training. CONCLUSION: The present results indicate that severe-intensity interval training, even when performed at a low frequency, markedly improves cardiorespiratory function as well as induces cardiac morphological adaptations involving left ventricular hypertrophy and cardiorespiratory metabolic response during submaximal exercise. The present findings may provide new insights for low-frequency, severe-intensity interval training in the field of sports science.

Effects of exercise training on gut hormone levels after a single bout of exercise in middle-aged Japanese women.

The purpose of this study was to investigate the effects of 12 weeks of exercise training on gut hormone levels after a single bout of exercise in middle-aged Japanese women. Twenty healthy middle-aged women were recruited for this study. Several measurements were performed pre and post exercise training, including: body weight and composition, peak oxygen consumption (peak VO2), energy intake after the single bout of exercise, and the release of gut hormones with fasting and after the single bout of exercise. Exercise training resulted in significant increases in acylated ghrelin fasting levels (from 126.6 ± 5.6 to 135.9 ± 5.4 pmol/l, P < 0.01), with no significant changes in GLP-1 (from 0.54 ± 0.04 to 0.55 ± 0.03 pmol/ml) and PYY (from 1.20 ± 0.07 to 1.23 ± 0.06 pmol/ml) fasting levels. GLP-1 levels post exercise training after the single bout of exercise were significantly higher than those pre exercise training (areas under the curve (AUC); from 238.4 ± 65.2 to 286.5 ± 51.2 pmol/ml x 120 min, P < 0.001). There was a tendency for higher AUC for the time courses of PYY post exercise training than for those pre exercise training (AUC; from 519.5 ± 135.5 to 551.4 ± 128.7 pmol/ml x 120 min, P = 0.06). Changes in (delta) GLP-1 AUC were significantly correlated with decreases in body weight (r = -0.743, P < 0.001), body mass index (r = -0.732, P < 0.001), percent body fat (r = -0.731, P < 0.001), and energy intake after a single bout exercise (r = -0.649, P < 0.01) and increases in peak VO2 (r = 0.558, P < 0.05). These results suggest that the ability of exercise training to create a negative energy balance relies not only directly on its impact on energy expenditure, but also indirectly on its potential to modulate energy intake.

Changes in salivary antimicrobial peptides, immunoglobulin A and cortisol after prolonged strenuous exercise.

The aim of the present study was to examine whether amount of oral antimicrobial components, human ß-defensin-2 (HBD-2), cathelicidin (LL-37), and immunoglobulin A (IgA), might be affected by prolonged strenuous exercise. Ten young male volunteers either exercised on recumbent ergometer at 75% [Formula: see text] for 60 min (exercise session) or sat quietly (resting session). Saliva samples were obtained at 60-min intervals during sessions for measurements of saliva antimicrobial components (HBD-2, LL-37, and IgA), saliva cortisol and osmolality. Saliva flow rate was decreased and saliva osmolality was increased during the 60-min exercise. Saliva HBD-2 and LL-37 concentrations and secretion rates were increased during and after the exercise, whereas saliva IgA concentration and secretion rates were decreased after the exercise. Saliva cortisol was increased during and after the exercise. The areas under the curve of the time courses of saliva levels of HBD-2 and LL-37 were negatively correlated with those of cortisol levels in saliva. The present findings suggested that a single bout of prolonged strenuous exercise caused a transient increase in the oral HBD-2 and LL-37 levels.

Effects of aquatic exercise training using water-resistance equipment in elderly.

To prevent falls in Japan, both gait and resistance training of the lower extremities are recommended. However, resistance training for the elderly induces muscle damage. Recently, aquatic exercise using water buoyancy and resistance have commonly been performed by the elderly. We have now produced new water-resistance equipment. The purpose of the present study was to evaluate the efficacy of aquatic exercise training using the new equipment for the elderly. Subjects were divided into two groups: a resistance group of 12 subjects (using water-resistance equipment) and a non-resistance group of eight subjects (without the equipment). The aquatic exercise training was 90 min, three times per week for 8 weeks, and mostly consisted of walking. All subjects underwent anthropometric measurements, physical performance testing, and profile of mood states (POMS). Significant improvements were observed in muscle strength in plantar flexion, and the timed up and go test (TUG) in both groups. Additionally, 10-m obstacle walking and 5-m maximum walking speed and length with eye-open were significantly improved in the resistance group. Also, a low negative correlation was found between the degree of change in TUG and POMS (tension and anxiety) scores in the resistance group. As it became easier to maintain posture, stand, and move, tension and anxiety in everyday life were alleviated with improvement of strength of the lower extremities and balance function. The present aquatic exercise training using water-resistance equipment may be used by the elderly to improve balance and walking ability, which are associated with the prevention of falls.

Comparable effects of moderate intensity exercise on changes in anorectic gut hormone levels and energy intake to high intensity exercise.

There is growing interest in the effects of exercise on plasma gut hormone levels and subsequent energy intake (EI) but the effects of mode and exercise intensity on anorectic hormone profiles on subsequent EI remain to be elucidated. We aimed to investigate whether circulating peptide YY(3-36) (PYY(3-36)) and glucagon-like peptide-1 (GLP-1 or GCG as listed in the HUGO Database) levels depend on exercise intensity, which could affect subsequent EI. Ten young male subjects (mean+/-s.d., age: 23.4+/-4.3 years, body mass index: 22.5+/-1.0 kg/m(2), and maximum oxygen uptake (VO(2 max)): 45.9+/-8.5 ml/kg per min) received a standardized breakfast, which was followed by constant cycling exercise at 75% VO(2 max) (high intensity session), 50% VO(2 max) (moderate intensity session), or rest (resting session) for 30 min. At lunch, a test meal was presented, and EI was calculated. Blood samples were obtained during three sessions for measurements of glucose, insulin, PYY(3-36), and GLP-1, which includes GLP-1 (7-36) amide and GLP-1 (9-36) amide. Increases in blood PYY(3-36) levels were dependent on the exercise intensity (effect of session: P<0.001 by two-way ANOVA), whereas those in GLP-1 levels were similar between two different exercise sessions. Of note, increase in area under the curve values for GLP-1 levels was negatively correlated with decrease in the EI in each exercise session (high: P<0.001, moderate: P=0.002). The present findings raise the possibility that each gut hormone exhibits its specific blood kinetics in response to two different intensities of exercise stimuli and might play differential roles in regulation of EI after exercise.

Changes in gut hormone levels and negative energy balance during aerobic exercise in obese young males.

We examined whether changes in gut hormone levels due to a single bout of aerobic exercise differ between obese young males and normal controls, and attempted to determine the involvement of hormonal changes during exercise in the regulation of energy balance (EB) in these obese subjects. Seven obese and seven age-matched subjects of normal weight participated in exercise and rest sessions. Subjects consumed a standardized breakfast that was followed by constant cycling exercise at 50% VO(2max) or rest for 60 min. At lunch, a test meal was presented, and energy intake (EI) and relative energy intake (REI) were calculated. Blood samples were obtained at 30 min intervals during both sessions for measurement of glucose, insulin, glucagon, ghrelin, peptide YY (PYY), and glucagon-like peptide-1 (GLP-1). Plasma levels of PYY and GLP-1 were increased by exercise, whereas plasma ghrelin levels were unaffected by exercise. The areas under the curve (AUC) of the time courses of PYY and GLP-1 levels did not significantly differ between the two groups. In contrast, EI and REI were decreased by exercise in both groups, and energy deficit was significantly larger in obese subjects than in normal controls. The present findings suggest that short-term EB during a single exercise session might be regulated not by increased amounts of these gut hormones per se.