Ventilatory Threshold Level Research Articles

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

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. 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. 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. 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.

The Relationships between Using the Rating of Perceived Exertion, Metabolic Equivalent and Maximum Heart Rate at Ventilatory Threshold into Determine Appropriate Exercise Prescription for Intensity in Obese Diabetic Patients: A Preliminary Study

Background: The rating of perceived exertion (RPE), metabolic equivalent (MET) and maximum heart rate (HRmax) at ventilatory threshold (VT) are commonly used methods as physiological parameters for monitoring exercise intensity. However, the appropriate levels of training intensity for obese type 2 diabetic diabetes mellitus (type 2 DM) patients have not been established.Purpose: To examine the parameters in obese Type 2 DM patients at ventilatory threshold, the exercise capacity of obese Type 2 DM patients, and to determine the appropriate levels of exercise intensity for exercise prescription in obese type 2 DM patients was investigated.Methods: Twenty obese type 2 DM patients (body mass index ＞27) were recruited. The physiological parameters (maximum oxygen uptake, maximum heart rate [or simply HRmax], and RPE at ventilatory threshold) of these patients were measured and compared during the cardiopulmonary exercise test.Results: The mean age of the subjects was 54.3±10.9 years, and the mean body mass index was 30.3±3.7. There was no difference on gender, the maximum oxygen uptake, maximum heart rate, and RPE by gender effect (p＞0.05). At ventilatory threshold level, the mean metabolic equivalent was 4.1±0.9, and the mean RPE was 13.0±1.7. The mean heart rate at VT was 117.3±14.5 beats/min, which is corresponded to 70.6±8.3% of the age-predicted HRmax, and the heart rate reserve was 36.3±14.7%.Conclusion: Our results indicate that the appropriate levels of exercise intensity for obese type 2 DM patients are 70% of the age-predicted HRmax, 30-40% of the heart rate reserve, MET of 4, and RPE of 13.

Influence of hypoxia training on the aerobic capacity of an elite race walker

PurposeThe aim of the study was to evaluate the influence of a combination of two different hypoxic training models (“live high-train high” and “live high-train low” with the use of a hypoxic tent) on the aerobic capacity of a elite race walker preparing for the 2009 IAAF World Championships.MethodsEvaluation of VO<sub>2</sub>max and the second ventilatory threshold was performed three times: 1) after four weeks training without hypoxic conditions, 2) after 28 days training in normoxia and sleeping for 8 h/day in a hypoxic tent (normobaric hypoxia, simulated hypoxia at 2133 m above sea level) and 3) after 26 days of classical altitude training at a moderate altitude of about 1800 m ASL (hypobaric hypoxia). The hematological parameters of the athlete’s blood (hematocrit, hemoglobin concentration, and erythrocytes and reticulocytes counts) were also measured after each stage.ResultsAfter training in normoxia and sleeping in a hypoxic tent the ventilatory threshold was noted at a higher work intensity and featured an improvement in his hematological parameters, although VO<sub>2</sub>max was unchanged (compared to training without hypoxia). After classical altitude training a higher level of VO<sub>2</sub>max was observed (with a ventilatory threshold level similar to the level after training in normobaric hypoxia), but the hematological indices were lower than the levels observed before starting hypoxic training.ConclusionsThe combination of two methods of hypoxic training improved the aerobic capacity of the test subject, but an improvement in the analyzed hematological indicators was observed only after LH + TL training. After training in LH + TH these indicators were lower in comparison to the levels prior hypoxic training. The changes in the hematological indices after hypoxic training did not seem to have a significant influence on aerobic capacity; the observed improvements in physical performance may result from other factors.

Relationship between Dyspnea Increase and Ventilatory Gas Exchange Thresholds during Exercise in Children with Surgically Corrected Heart Impairment

To study the relationship between the onset of an increase in dyspnea and ventilatory threshold (VT) in children with congenital heart impairment, sixteen young subjects underwent a cardiopulmonary exercise test with dyspnea perception and ventilatory gas exchange assessments. Dyspnea score was measured from a visual analogical scale at rest and during each step of an incremental exercise test. Dyspnea score was plotted against oxygen uptake and the onset of an increase in dyspnea (DT) was determined when a brutal disruption occurs on the dyspnea score-oxygen uptake curve. VT was defined from gas exchange according to Beaver's method. The first breakdown point in the oxygen uptake-carbon dioxide production relationship locates VT. Oxygen uptake (V(.-)O (2)), pulmonary ventilation (V(.-)E), heart rate (HR), oxygen pulse (O (2) pulse = V(.-)O (2)/HR), carbon dioxide production (V(.-)CO (2)) and power output (P) were measured both at VT and DT effort level. Results pointed out that there was no significant difference between the cardiorespiratory variables measured respectively at VT and DT: V(.-)O (2) (VTV(.-)O (2) = 16.71 +/- 2.65 vs. DTV(.-)O (2) = 18.34 +/- 5.74 ml x kg (-1) x min (-1)), V(.-)E (VTV(.-)E = 24.33 +/- 6.86 vs. DTV(.-)E = 26.82 +/- 9.59 l x min (-1)), (VTV(.-)CO (2) = 789.31 +/- 165.17 vs. DTV(.-)CO (2) = 924.02 +/- 342.28 ml x min (-1)), HR (VTHR = 116 +/- 10 vs. DTHR = 123 +/- 20 beat x min (-1)), O (2) pulse (VT O (2) pulse = 7.83 +/- 2.00 vs. DT O (2) pulse = 8.01 +/- 2.13 ml x kg (-1) x beat (-1)), and P (VTP = 43 +/- 16 vs. DTP = 52 +/- 27 W). Moreover, the cardiorespiratory variables measured at DT and VT were closely related: V(.-)O (2) (r = 0.64, p < 0.01), V(.-)E (r = 0.51, p < 0.01), HR (r = 0.75, p < 0.02), O (2) pulse (r = 0.90, p < 0.001), and P (r = 0.80, p < 0.01). In addition, according to Bland and Altman's procedure, the onset of dyspnea increase and ventilatory threshold were shown in close agreement for the cardiorespiratory variables measured at these effort levels. The standard errors of the estimates were low. It was concluded that dyspnea and ventilatory gas exchange thresholds occur concomitantly and were strongly correlated in children with congenital heart impairment. The use of the onset of dyspnea increase for aerobic capacity assessment may be a good alternative to ventilatory gas exchange threshold measurement.

Effect of Hypoxia on the Kinetics of Peripheral Muscle Oxygenation during Prolonged Exercise

Near-infrared spectroscopy (NIRS) is a noninvasive method of measuring muscle oxygenation. We have examined relationships between muscle oxygenation and blood lactate concentration, substrate utilization, femoral artery blood flow, and systemic oxygen intake during prolonged exercise. However, we have not examined muscle oxygenation trends during prolonged exercise at different oxygen levels. PURPOSE: To clarify the effect of hypoxia (FiO2=0.16) on the local muscle oxygenation trends during prolonged cycle exercise at ventilatory threshold (VT) level. METHODS: Seven healthy males completed an orientation trial and a maximal exercise test, followed by two 30-min submaximal exercise bouts. During each exercise test, expiratory gas analysis was performed using an expiratory gas analyzer, and the muscle oxygenation trends of vastus lateralis muscle were determined by NIRS. After exercises, calibration was performed by cuff occlusion at 260 mmHg for 10 min. Cardiorespiratory parameters, forearm venous blood lactate concentration and epinephrine levels were measured at rest and during exercise. RESULTS: Arterial O2 saturation levels at rest and during exercise in the hypoxic condition were significantly lower than those in normoxia condition (p<0.05). VO2, HR and epinephrine levels during exercise in the hypoxic condition were significantly higher than those in normoxia condition (p<0.05). Muscle oxygenation decreased immediately after the onset of exercise and gradually increased, but it did not reach the resting level. This pattern of muscle oxygenation was similar for two gas conditions. However, the rate of decrease in muscle oxygenation was enhanced by reduced arterial O2 saturation. On the other hand, after the initial drop, the rate of increase in muscle oxygenation during exercise did not change for two gas conditions. These results indicate that the rate of decrease in muscle oxygenation is sensitive to oxygen delivery. CONCLUSIONS: The significant decrease in muscle oxygenation induced by hypoxia during prolonged exercise at VT level was due to a greater release of oxygen by oxyhemoglobin at the capillaries via Bohr effect.

Recommendation for Cardiovascular Safety of Exercise in Middle-aged and Elderly People

In order to exercise safely, proper exercise prescription based on each individual's physical fitness and health status is needed. An intensity equivalent to the ventilatory threshold level has been recommended in terms of safety of aerobic exercise, and we confirmed its safety in very elderly subjects (older than 75 years) if they had no contraindications to exercise. More than 20% of the subjects with sedentary lifestyles and lower physical fitness had deleterious symptoms such as excessive blood pressure elevation, dangerous arrhythmias, and myocardial ischemia during exercise testing. Therefore, evaluation of physical fitness level enables optimal exercise prescription for aerobic exercise in the elderly, and low-level intensity (40% of VO2max) is recommended for those subjects. Excessive blood pressure elevation was frequent in greater than 60% of 1RM lower-leg resistance exercise in the elderly subjects. Therefore, 40% of 1RM intensity is recommended in terms of safety in very elderly-aged people or those with hypertension. Proper breathing technique avoiding the Valsalva effect is effective to minimize blood pressure rise during resistance exercise. Aerobic exercise training could have a lowering effect on blood pressure rise during resistance exercise in the elderly subjects. It is noteworthy that the frequency of deleterious symptoms during exercise could not decrease after short-term aerobic exercise training in the elderly.

Six-Minute Walking Test to Assess Exercise Tolerance and Cardiorespiratory Responses During Training Program in Children With Congenital Heart Disease

This study assessed the exercise tolerance and the cardiorespiratory responses to a training program by the six-minute walk test (6'WT) in children with congenital heart disease (CHD). Seventeen cardiac and 14 healthy children performed maximal cardiopulmonary exercise test (CPET) and 6'WT. Reliability of 6'WT was assessed in all subjects (test-retest) by Bland-Altman plots. Cardiac subjects were randomly divided in training (T-CHD) and control groups (C-CHD). T-CHD underwent an individualized training exercise at the ventilatory threshold (VT) intensity during 12 weeks. We found that the 6'WT is a reliable and reproducible test. CHD children walked a lower distance than healthy children before training (472.5 +/- 18.1 vs. 548.8 +/- 7.7 m, respectively, p < 0.001). Likewise, power output, oxygen uptake (V.O (2)), and heart rate (HR) at the maximum and the VT levels, were significantly lower in patients (p < 0.001). After training, a significant improvement of walking distance (WD) was shown in T-CHD (529.6 +/- 15.3 vs. 467.7 +/- 17.1 m, p < 0.001). The power output, VO2, HR, and V.E increased slightly (6 to 10 %, p > 0.05) at peak exercise and significantly at ventilatory threshold level (p < 0.05) in T-CHD. Significant relationships between WD and VO2max as well as VO2 at VT were founded (p < 0.05). We concluded that the 6'WT is a useful and reliable tool in the assessment and follow-up of functional capacity during rehabilitation program in children with CHD.

腹腔内脂肪面積の差異が換気性代謝閾値強度での長時間運動中の脂質代謝に及ぼす影響

Some previous investigations have discussed whether visceral adipose tissue may decrease as a result of exercise intervention. However, there is no evidence that the lipid metabolism of visceral adipose tissue predominates during aerobic exercise. The purpose of this study was to examine whether there is a difference in lipolysis of intra-abdominal fat and endocrine hormone during prolonged exercise at ventilatory threshold (VT) load intensity. Sixteen healthy obese women, aged 51.8 ± 7.5 years were categorized into two groups according to their intra-abdominal fat area: a visceral fat obesity (VF-Ob) group and a subcutaneous fat obesity (SF-Ob) group. Mean ± SD of body weight and body mass index were 67.2 ± 4.0 kg and 28.1 ± 1.7 kg/m^2 respectively for the VF-Ob group, and 68.2 ± 3.0 kg and 27.3 ± 0.7 kg/m^2, respectively for the SF-Ob group. Each subject perfomed a submaximal cycling exercise test for 60 min at a constant VT level load, which had been previously determined by an incremental protocol exercise. There were no significant differences between the two groups in catecholamines, %fat oxidation, insulin, and glucose at each of the measurement points (0, 30, 60 min). Significant differences were found in free fatty acid and glycerol in the VF-Ob group (two-way repeated ANOVA, P&lt;0.05), but these remained unchanged during the last 30 min of exercise. There was no significant difference in energy expenditure of fat metabolism over exercise between the two groups. These results suggest that visceral adipose tissue seems to be affected more instantly by lipolysis than subcutaneous fat tissue during prolonged exercise. However, both types of fat show approximately equal consumption during exercise. Therefore, more investigations are needed to determine whether there is a specific form of metabolism for visceral fat during exercise.

Exercise at ventilatory threshold aggravates left ventricular remodeling in patients with extensive anterior acute myocardial infarction

BackgroundThe effects of physical training on ventricular remodeling after extensive anterior acute myocardial infarction (AMI) have not yet been defined. This randomized controlled study examines whether exercise aggravates left ventricular (LV) remodeling in patients with extensive anterior AMI. MethodsForty-eight consecutive patients with a first extensive anterior AMI and an LV ejection fraction (EF) of <45% assessed with left ventriculography (LVG) within 3 days of onset were randomly allocated to a training group (n = 24) or a control group (n = 24). Exercise intensity was determined by the heart rate of each patient at ventilatory threshold (VT). Three weeks after onset, a second LVG was performed, followed by a supervised exercise program at VT for 12 weeks. The LVG was reassessed after the exercise program. We then calculated the global LV volume (end-diastolic volume index [EDVI], end-systolic volume index [ESVI]) and systolic expansion volume index (SEVI), a new parameter for measuring the infarction site expansion at the end-systolic phase. ResultsBoth EDVI and ESVI significantly decreased in the control group from 1 to 4 months after onset (91.2 ± 26.1 to 83.3 ± 24.0 mL/m2, P <.05; 52.4 ± 22.5 to 45.7 ± 18.8mL/m2, P <.01, respectively), but not in the exercise group. The SEVI also significantly decreased in the control group from 1 to 4 months (33.1 ± 16.9 to 25.7 ± 13.9 mL/m2, P <.05), but not in the training group (34.2 ± 12.9 to 36.5 ± 15.5 mL/m2, P = not significant). ConclusionExercise while healing in patients with extensive anterior AMI, even at the VT level, induces LV enlargement and thus might aggravate LV remodeling. Therefore, in these patients, clinicians should consider withholding exercise training for at least 8 weeks, versus the 3-week period used in this trial.

Effects of exercise intensity on circulating leukocyte subpopulations.

The purpose of this study was to examine the relation between exercise intensity and immune function. Ten healthy young males underwent a constant work rate exercise of three levels, 90%, 80% and 70% ventilatory threshold (VT) work rate, for 20 min on a bicycle ergometer. These work rates were calculated for each individual based on his VT work rate obtained by the incremental exercise tests. Blood samples were collected before and after the exercise, and immune function indices were measured. Compared with the obtained[Formula: see text] at[Formula: see text] in the incremental test, the[Formula: see text] with the exercise of 70% VT work rate was at a similar level and the one with the exercise of 90% or 80% VT work rate had a significantly greater value. The numbers of leukocytes and neutrophils significantly increased in the 90% and 70% VT work rate groups. In 80% VT work rate group, the CD4/CD8 ratio was significantly depressed. The CD16(+)CD57(-) (%), natural killer cell populations, had a tendency to increase at 80% VT work rate, and also the CD16(+)CD57(-) (%) had a similar tendency at 90% or 80% VT work rate. This study shows that moderate exercise reaching or exceeding the VT level acutely affects T cell and NK cell subsets.

Physiological profiles of male and female taekwon-do (ITF) black belts

Baseline physiological and kinanthropometric data were collected for 11 male and 12 female elite taekwon-do athletes from the Czech national team for evaluation of anthropometry, aerobic and anaerobic capacities, strength, visual reaction time, pulmonary function, flexibility and explosive power of the lower limbs (vertical jump). Both male and female taekwon-do black belts demonstrated low adiposity (8.2 and 15.4% fat, BMI 21.9 and 22.0 kg m-2, respectively), normal reactivity and pulmonary function, above average muscular strength, PWC-170 (3.4 vs 2.7 W kg-1) and aerobic power (54 vs 42 ml min-1 kg-1), and a high flexibility (37 and 38 cm) and anaerobic performance (peak power output from a 30 s Wingate test = 14.7 and 10.1 W kg-1; anaerobic capacity = 334 and 242 J kg-1, in males and females, respectively). In male athletes, competitive performance was significantly related to maximum power output and upper limb reaction time only, whereas in females, performance was related to maximum power output and ventilatory threshold level. These variables accounted for 66 and 67% of the performance rank in males and females, respectively. Time-motion analysis of competition taekwon-do fighting (two times 2 min) revealed 3-5 s bouts of maximum exercise alternating with low-intensity periods. This elicits high heart rates (100% HRmax) and lactate responses (11.4 mmol 1-1 = 81% LAmax), which agrees well with the physiological characteristics of taekwon-do black belts measured in laboratory exercise tests.

Quantitative beat-to-beat analysis of heart rate dynamics during exercise.

Beat-to-beat heart rate (HR) dynamics were studied by plotting each R-R interval as a function of the previous R-R interval (Poincaré plot) during incremental doses of atropine followed by exercise for 10 subjects and during exercise without autonomic blockade for 31 subjects. A quantitative two-dimensional vector analysis of a Poincaré plot was used by measuring separately the standard deviation of instantaneous beat-to-beat R-R interval variability (SD1) and the standard deviation of continuous long-term R-R interval variability (SD2) as well as the SD1/SD2 ratio. Quantitative Poincaré measures were compared with linear measures of HR variability (HRV) and with approximate entropy (ApEn) at rest and during exercise. A linear progressive reduction was observed in SD1 during atropine administration, and it remained almost at the zero level during exercise after a parasympathetic blockade. Atropine resulted in more variable changes in SD2 and the SD1/SD2 ratio, but during exercise after parasympathetic blockade, a progressive increase was observed in the SD1/SD2 ratio until the end of exercise. The SD1/SD2 ratio had no significant correlations with the frequency domain measures of HRV. However, the SD1/SD2 ratio had a modest correlation with ApEn at rest (r = -0.69, P < 0.001), but not during exercise (r = 0.27, P = NS). All measures of vagal modulation of HR decreased progressively until the ventilatory threshold level was reached, when sympathetic activation was reflected as changes in the SD1/SD2 ratio. These results show that quantitative two-dimensional vector analysis of a Poincaré plot can provide useful information on vagal modulation of R-R interval dynamics during exercise that are not easily detected by linear summary measures of HRV or by ApEn.

Ventilatory threshold in various groups of highly trained athletes.

The ventilatory threshold (VT) was determined on a treadmill in highly trained male marathon, male and female long-distance, young male long-distance, adult male and female and young female middle-distance runners, modern pentathlonists, adult canoeists of both sexes, young male canoeists and football players, and on a bicycle ergometer in table tennis players, water slalom paddlers, young female canoeists rowers, and ice hockey players. Young female canoeists were also examined on the paddling ergometer and rowers on the rowing ergometer. VT expressed in %VO2 max was higher the longer the duration of racing performance (in marathoners 86.7%). %VO2 max at the VT level depends on the type of load and is higher the better the organism is adapted to a load. In young female canoeists and rowers examined on the bicycle ergometer, we found the VT level at 74.2% and 74.6% of %VO2 max, respectively. In the case of specific loading, we recorded 84.8% and 85.0% of %VO2 max, respectively, in the same athletes. In the case of nonspecific loading highly trained individuals may have low VT values close to the level characteristic for normal subjects. In relatively equally trained young and adult athletes we did not find significant differences in %VO2 max at the VT level (for long-distance runners, 85.2% and 85.3%, respectively, in female middle-distance runners, 82.8% and 82.7%, respectively, and in canoeists 81.3% and 78.9% of %VO2 max, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)