Plasma oxidative state induced by exercise in young heat-not-burn cigarette users.

INTRODUCTION: Oxidative state, a risk factor for several diseases, is increased by habitual conventional cigarette (CC) smoking. Reports have demonstrated that heat-not-burn cigarettes (HNBC), which have recently become popular among smokers, generate less oxidative state than CC in smokers with a long smoking history. However, no previous study has examined oxidative state in young HNBC users. Previously, we reported that exercise induces a greater oxidative state in young CC smokers than in never-smokers of similar age, but there was no difference in resting oxidative state. This study aimed to clarify the resting and exercise-induced oxidative states in young HNBC users, compared with those in never-smokers and CC users of similar age. METHODS: Healthy young never-smokers, HNBC users, and CC users were recruited, and they underwent the Wingate anaerobic test. Blood samples were collected before and after exercise, and the plasma hydroperoxide concentration, a marker of oxidative state, was measured. RESULTS: No significant differences in pre-exercise plasma hydroperoxide concentrations were detected among never-smokers, HNBC users, and CC users (n = 10 each). Plasma hydroperoxide concentration was significantly increased after exercise in all participants. The exercise induced a significant increase in plasma hydroperoxide concentration in HNBC users compared with that in never-smokers (P < .005), but it was significantly decreased compared with that in CC users (P < .01). CONCLUSIONS: The use of HNBC increased exercise-induced plasma oxidative state compared with that in never-smokers, indicating that HNBC may lead to the risk of oxidative damage. IMPLICATIONS: This study, for the first time, reports exercise-induced oxidative state in young heat-not-burn cigarette users compared with never-smokers and conventional cigarette users. The exercise-induced oxidative state in heat-not-burn cigarette users was higher than that in never-smokers and lower than that in conventional cigarette users. Our study suggests that the use of heat-not-burn cigarettes increases the risk of acute oxidative damage.

Effects of soy protein isolate and soy peptide preload on gastric emptying rate and postprandial glycemic control in healthy humans.

BACKGROUND: This study aims to compare the effects of soy protein isolate (SPI) and soy peptide (PEP) preload 30 min before a 75-g oral glucose tolerance test (OGTT) on the gastric emptying rate, plasma insulin, and blood glucose responses. METHODS: Nine healthy young subjects were evaluated on four occasions. The participants consumed a 200-ml solution containing either 20 g of SPI or PEP in experiment 1. In experiment 2, 30 min after consuming either 20 g of SPI or PEP solutions, an OGTT was performed to evaluate the individual glycemic response. The gastric emptying rate was measured by the 13C-sodium acetate breath test. Blood glucose and plasma insulin were measured before and after consuming either the SPI or PEP solutions and during the OGTT. RESULTS: In experiment 1, plasma insulin levels were higher 30 min after consuming the PEP solution than after the SPI solution. PEP resulted in a faster gastric emptying rate than SPI. In experiment 2, just before performing the OGTT, the plasma insulin response was higher for PEP than for SPI. Fifteen minutes after starting the OGTT, the blood glucose response was lower after consuming PEP than after SPI. The gastric emptying rate tended to be faster after consuming PEP than after SPI (p = 0.08). CONCLUSION: A PEP preload might be slightly more effective for the suppression of postprandial blood glucose excursion compared with SPI; thus, a PEP preload potentially induces an enhanced insulin response just before the OGTT.

Effects of L-arginine on impaired blood fluidity after high-intensity exercise: An in vitro evaluation.

BACKGROUND: Exercise-induced impairment of blood fluidity is considered to be associated with thrombosis development. However, the effects of L-arginine on blood fluidity after exercise remain unclear. OBJECTIVE: We investigated the mechanisms of impaired blood fluidity after high-intensity exercise, and examined whether L-arginine improves exercise-induced blood fluidity impairment in vitro. METHODS: Ten healthy male participants performed 15 minutes of ergometer exercise at 70% of their peak oxygen uptake levels. Blood samples were obtained before and after exercise. L-arginine and NG-monomethyl-L-arginine acetate (L-NMMA)-a nitric oxide (NO) synthase inhibitor-were added to the post-exercise blood samples. Using Kikuchi's microchannel method, we measured the blood passage time, percentage of obstructed microchannels, and the number of adherent white blood cells (WBCs) on the microchannel terrace. RESULTS: Exercise increased the hematocrit levels. The blood passage times, percentage of obstructed microchannels, and the number of adherent WBCs on the microchannel terrace increased after exercise; however, they decreased in a dose-dependent manner after the addition of L-arginine. L-NMMA inhibited the L-arginine-induced decrease in blood passage time. CONCLUSIONS: High-intensity exercise impairs blood fluidity by inducing hemoconcentration along with increasing platelet aggregation and WBC adhesion. The L-arginine-NO pathway improves blood fluidity impairment after high-intensity exercise in vitro.

Relationship between perceived exertion and blood lactate concentrations during incremental running test in young females.

BACKGROUND: To investigate more practical handling of Borg's ratings of perceived exertion (RPE) and category-ratio scale of RPE (CR-10), we evaluated interrelationships between RPE, CR-10, and blood lactate concentrations (bLa) during incremental treadmill running tests for young females with different aerobic fitness levels. METHODS: Oxygen consumption, heart rate, bLa, RPE, and CR-10 were measured from distance runners (DR; n = 15), race walkers (RW; n = 6), and untrained females (UT; n = 11). These variables corresponding to the lactate threshold (LT) and onset of blood lactate accumulation (OBLA) were compared among these groups. RESULTS: The UT had significantly lower RPE at LT than DR and RW, although the CR-10 at LT was not significantly different among these groups. The CR-10 at OBLA was significantly lower for the UT than DR. The relationship between bLa and CR-10 was approximated well by two linear regression lines in all groups. The bLa at the intersection only for the RW was significantly lower than that at LT, however, such intersections were observed at CR-10 = 3.1 to 3.2 without significant group differences. The CR-10 scores at LT and intersections were not significantly different in each group. CONCLUSION: These results suggested that an intersection between CR-10 and bLa was observed at the CR-10 score around three points of first half regardless of the aerobic fitness levels in young females, and such CR-10 scores would be associated with LT.

Autonomic nervous activities assessed by heart rate variability in pre- and post-adolescent Japanese.

There are many studies with respect to the age-related change of the characteristics of beat-to-beat heart rate variability (HRV), reflected by cardiac autonomic control, especially focusing on adulthood (i.e., aging related to the incidence of metabolic syndrome) in Japanese individuals. However, it is not still clear how basic control matures during childhood. This study was, therefore, designed to explore the HRV characteristics of pre- and post-adolescent Japanese, in a cross-sectional manner. Resting HRV data was recorded in a relaxing supine position from 136 healthy individuals between 8 and 20 years (48 boys between 8 and 14 years; 88 girls between 8 and 20 years) who were instructed to breathe periodically (0.25 Hz). Frequency-domain analysis (i.e., the spectral analysis based on an autoregressive model) of short-term, stationary R-R intervals was performed to evaluate the low- (LF; below 0.15 Hz) and high- (HF; 0.15-0.40 Hz) frequency powers. The HF to total power represents the vagal control of heart rate (PNS indicator), and the ratio of LF to HF (LF/HF) is considered to relate to the sympathetic modulations (SNS indicator). Both PNS and SNS indices had substantially no effect from age and/or gender in the range between 8 and 20 years. In conclusion, the control of the cardiac autonomic nervous system in Japanese seems already to be compatible with that in adulthood before approximately 10 years. In other word, the cardiac autonomic modulation would presumably be maturated before the age of approximately 7-8 years, though further research is awaited.

Effect of aerobic leg exercise training on subcutaneous adipose tissue of thigh in young Japanese women.

A one-legged training model was adopted to assess the influence of moderate-intensity exercise training on subcutaneous adipose tissue, especially focusing on the trained limb. Eight young sedentary Japanese women (ages 21-23 yr) participated in a 12-week training program. The leg was assigned randomly to trained or untrained limb. Each subject performed a supervised 60-min one-legged cycle ergometer training session three times a week. The exercise intensity was set at approximately 40% of peak VO(2) ("moderate" intensity, i.e., below the estimated lactate threshold), which was determined before training. Each subject performed a one-legged incremental cycle exercise test until exhaustion to determine the peak VO(2) of each leg (the trained and untrained legs being investigated separately). The areas of subcutaneous fat and the remaining nonfat tissues of the thigh were evaluated by our novel visualized measuring system based on ultrasonography. The fat cross-sectional areas of the trained and untrained thigh were not different after training (trained: 68.6+/-17.8 vs. untrained: 68.3+/-18.5 cm(2)). The non-fat (muscle and bone) area was also similar between the trained and untrained limb. In addition, there was no systematic influence of the training on the total and lean body mass. After training, the duration time of the one-legged cycle incremental exercise test by the trained leg was significantly improved unilaterally (trained: 1049+/-122 vs. untrained: 930+/-109 s, p<0.05) without any difference of peak VO(2). The results indicate that moderate one-legged aerobic training did not induce any compositional change in the trained thigh; rather, what did improve were certain peripheral factor alone relating to endurance.

Exercise hyperpnea and hypercapnic ventilatory responses in women.

We studied the relationship between exercise hyperpnea (i.e., ventilatory dynamics) at the onset of exercise and hypercapnic ventilatory response (HCVR), and their differences between the follicular (FP) and luteal (LP) phases of the menstrual cycle in six healthy females. HCVR was tested under three O(2) conditions: hyperoxia (FiO(2)=1.0), normoxia (0.21), and hypoxia (0.12). HCVR was defined as the relationship between the end-tidal P(CO2) and minute ventilation (V(E)) using the regression line of the CO(2) slope and a mimetically apneic threshold of CO(2). HCVR provocation and measurements were conducted using an inspired CO(2) concentration of up to approximately 8 mmHg higher than the end-tidal P(CO2) level of basal isocapnic the end-tidal P(CO2) at each menstrual both the slope and threshold in HCVR showed no statistically significant difference between LP and FP under any inspired FiO(2) conditions. In the case of exercise hyperpnea during the onset of submaximal exercise, the mean response time (MRT) in V(E) dynamics showed no significant difference between LP and FP. Consequently, MRT in V(E) response was not related to the slope in HCVR. During steady-state exercise, even though the V(E)/V(CO2) showed no significance between LP and FP, V(E)/V(CO2) was significantly related to the slope in HCVR (r=0.59, P<0.05). Exercise ventilation (i.e., V(E)/V(CO2)) would partly be adjusted by the enhancement of the chemoreflex drive to CO(2) only during the steady-state exercise.

Central circulatory and peripheral O2 extraction changes as interactive facilitators of pulmonary O2 uptake during a repeated high-intensity exercise protocol in humans.

It has frequently been demonstrated that prior high-intensity exercise facilitates pulmonary oxygen uptake [Formula: see text] response at the onset of subsequent identical exercise. To clarify the roles of central O(2) delivery and/or peripheral O(2) extraction in determining this phenomenon, we investigated the relative contributions of cardiac output (CO) and arteriovenous O(2) content difference [Formula: see text] to the [Formula: see text] transient during repeated bouts of high-intensity knee extension (KE) exercise. Nine healthy subjects volunteered to participate in this study. The protocol consisted of two consecutive 6-min KE exercise bouts in a supine position (work rate 70-75% of peak power) separated by 6 min of rest. Throughout the protocol, continuous-wave Doppler ultrasound was used to measure beat-by-beat CO (i.e., via simultaneous measurement of stroke volume and the diameter of the arterial aorta). The phase II [Formula: see text] response was significantly faster and the slow component (phase III) was significantly attenuated during the second KE bout compared to the first. This was a result of increased CO during the first 30 s of exercise: CO contributing to 100 and 56% of the [Formula: see text] speeding at 10 and 30 s, respectively. After this, the contribution of [Formula: see text] became increasingly more predominant: being responsible to an estimated 64% of the [Formula: see text] speeding at 90 s, which rose to 100% by 180 s. This suggests that, while both CO and [Formula: see text] clearly interact to determine the [Formula: see text] response, the speeding of [Formula: see text] kinetics by prior high-intensity KE exercise is predominantly attributable to increases in [Formula: see text].

Effects of femoral vascular occlusion on ventilatory responses during recovery from exercise in human.

We investigated the effect of occluding of femoral blood flow on the post-exercise ventilatory response of both the sub- and supra-anaerobic threshold (AT) leg cycling in humans. Seven healthy subjects (aged 21-44 years) volunteered to participate in this study. The protocol consisted of 6 min constant-load upright cycling at either a sub-AT (80% of AT) or supra-AT (midway between AT and VO(2)max) work rate and a subsequent 6 min rest period either with or without femoral blood flow being occluded by a rapid cuff inflation to 250 Torr during the first 2 min of recovery. Blood lactate levels at the cessation of the sub- and supra-AT exercise averaged 1.8+/-0.2 and 4.9+/-0.4 mequiv.l(-1) (mean+/-S.E.M.), respectively. Compared to spontaneous recovery, the circulatory occlusion significantly reduced ventilation irrespective of the intensity of the preceding exercise. The relative contribution of the ventilatory deficit to the total spontaneous ventilation (defined as the difference between the cumulative ventilation with and without cuff inflation during the first 2 min of recovery) was significantly greater supra-AT (18.0+/-3.9%) than sub-AT (9.3+/-2.9%, P<0.05). The subsequent release of occlusion was accompanied by a rapid increase in ventilation that began on the first breath after release. We concluded that the relatively greater speeding of ventilatory decline with occlusion during the first 2 min of recovery from supra-AT exercise argues against a significant role for an intramuscular chemoreflex-induced hyperpnoea. Rather, mechanisms related to the hemodynamic effects of suddenly altered muscle perfusion seem more consistent with this phenomenon.

Effects of wheelchair training on VO2 kinetics in the participants with spinal-cord injury.

PURPOSE: We tested the hypothesis that, in eight participants (seven males, one female; 46.5 +/- 8.3 years) with spinal-cord injury (complete lesions, T7-L1), the effects of exercise training on pulmonary O2 uptake (VO2) on- and off-kinetics would appear early in this pilot study. METHODS: The subjects underwent the wheelchair-training program (3 day/w, 30 min/day, and 50% HRreserve), and were evaluated before training ("time 0", T0), and after 7 (T7), 15 (T15), 30 (T30), and 60 (T60) days of training. Breath-by-breath peak VO2 was determined during the incremental exercise until their exhaustion. At another day following the incremental exercise, the subjects performed three repetitions of a constant exercise at 50% peak VO2 workload so that VO2 could be determined for both on- and off-kinetics. RESULTS AND CONCLUSION: Peak VO2 showed a tendency to increase with training; the increases became significant at T30. The time constants (tau 2) during "phase II" of the VO2 on-kinetics were 62.4 +/- 13.0 (s) (T0), 51.2 +/- 8.7 (T7), 46.1 +/- 7.4 (T15), 45.0 +/- 7.2 (T30), and 43.4 +/- 6.4 (T60); a significant difference compared to T0 was observed from T7 onward. The same pattern of change as a function of training was described for the VO2 off-kinetics. It is concluded that in SCI participants, the acceleration of VO2 kinetics at the onset of exercise was observed over a short term.