Continuous Incremental Exercise Test Research Articles

健常女性における最大下運動時の二重積屈曲点と動脈スティフネスの関係

The purpose of this study was to elucidate the relation between double product break point (DPBP) and pulse wave velocity (PWV).Two hundred three healthy Japanese females were studied (mean age; 53.5 +/- 11.7 years old). The DPBP was measured by continuous incremental exercise test with a bicycle ergometer (ML-3600, Fukuda Electronic Co. Ltd). The work rate at DPBP was converted into metabolic equivalents (METs@DPBP). The brachial-ankle PWV (baPWV) was also measured. In addition, height, weight and mean blood pressure (mBP) were measured and physical activity condition in daily life (PA) was evaluated by questionnaire.The mean METs@DPBP was 5.0 +/- 0.7 METs. The mean baPWV was 1,373 +/- 254 cm/ sec. The relation between METs@DPBP and baPWV was investigated with the use of multiple linear regression models with adjustment for affecting factors of baPWV.In this study, it was identified that there was a significantly inverse relation between METs@DPBP and baPWV (p <0.01). This finding was independent from age, height, weight, mBP and PA. Thus, there was an inverse relation between sub-maximal aerobic capacity and arterial stiffness.

年齢から推定した50%VO&lt;sub&gt;2&lt;/sub&gt;max相当のMETsと冠動脈疾患危険因子との関係

The aim of this study is to elucidate the relationship between the predicted 50%VO2max/wt (ml/kg/min) and coronary risk factors (CRFs).Seven hundred eighty six men (37.3 +/- 13.5 years old) and 1,268 women (41.5 +/- 13.6 years old) were studied. The predicted 50%VO2max/wt was calculated by utilizing data from the continuous incremental exercise test with a stationary bicycle ergometer and the age-predicted heart rate at 50%VO2max (=138-age/2). As CRFs, percent body fat, systolic blood pressure, diastolic blood pressure, total cholesterol, triglyceride, high density lipoprotein cholesterol, fasting blood sugar and HbA1c were measured.The age-adjusted odds ratio of having abnormal values in CRFs across quartiles of the predicted 50%VO2max/wt (highest to lowest) were 1.00 (reference), 1.39, 2.64, and 6.78 in men, and 1.00, 1.73, 2.33 and 3.44 in women (for trend, p<0.001), respectively.This study indicated that the lower 50%VO2max/wt resulted in the higher odds ratio of having abnormal values in CRFs among Japanese. It was also confirmed that the sub-maximal aerobic capacity was associated with CRFs.

Emergence of the verification phase procedure for confirming ‘true’V̇O2max

Traditional (.)VO(2max) criteria are typically based on attainment of a (.)VO2 plateau, and threshold values for the respiratory exchange ratio, heart rate and blood lactate concentration. Despite long-standing criticisms directed at these criteria, their use remains widespread. This article discusses an alternative procedure, termed the verification phase, for confirming the attainment of true (.)VO(2max). Following a continuous incremental exercise test to the limit of tolerance and appropriate recovery period, the verification phase is performed and is characterized by a supramaximal square wave exercise bout. Consistent peak (.)VO2 values in the incremental and verification phases, confirms that a true (.)VO(2max) has been attained. Six recent studies investigated the utility of the verification phase for evaluating true (.)VO(2max). These studies consistently found small insignificant mean differences between the maximal (.)VO2 attained in the incremental and verification phases. However, this group mean approach does not identify individual subjects who may not have attained a true (.)VO(2max). Notably, only one of the six studies reported a criterion threshold to verify the (.)VO(2max) of individual subjects. Further research is required to investigate the utility of different verification phase procedures and to establish a suitable verification criterion threshold for confirming true VO(2max).

Vo2 requirement at different displayed power outputs on five cycle ergometer models: a preliminary study

Background and aimsThe validity of five brands of cycle ergometers was evaluated by the comparison of the Vo2 requirements at different displayed power.Methods and resultsFive physically active men performed a...

Fat Oxidation Rates are Higher Over a Wide Range of Intensities in Rowing Compared to Cycling Ergometry

The relative contribution of carbohydrate and fat oxidation to whole body energy production during exercise is dependent on oxygen availability. Continuous incremental exercise is associated with a progressive increase in carbohydrate oxidation and a decrease in fat oxidation. The exercise modality, more specifically the muscle mass recruited, is also thought to be an important contributor to substrate selection. PURPOSE: The purpose of this study was to determine the rates of fat oxidation and the cross-over point for substrate utilisation over a wide range of intensities during incremental rowing and cycle ergometry. METHODS: Thirteen moderately trained male rowers [age, 23.2 ± 1.6 yrs; height, 1.82 ± 0.02 m; body mass, 77.0 ± 1.6 kg] performed a continuous incremental exercise test to exhaustion on an electronicaly braked cycle ergometer and an air braked rowing ergometer. The exercise intensity began at 95W and increased in 35W increments every 3-min. Rates of substrate oxidation and the relative contribution to energy expenditure were calculated for the same absolute (W) and relative (%VO2peak) intensity by indirect calorimetry during the last 2-min of each 3-min stage. RESULTS: Peak oxygen consumption was similar for the rowing (57.5 ± 1.5 ml kg min−1) and cycle (55.7 ± 1.6 ml kg min−1) ergometer tests. Peak fat oxidation was higher in rowing (0.72 ± 0.05 g.min−1) than cycling (0.51 ± 0.04 g.min−1, p=0.008) and occurred during the first stage. The rate of fat oxidation was greater during rowing at the same absolute (p=0.019) and relative (p=0.001) exercise intensities up to ∼93%VO2peak. The crossover point for substrate utilisation occurred at a higher relative exercise intensity for rowing than cycling (57.8 ± 2.1 vs. 42.1 ± 3.6 %VO2peak, p=0.003). CONCLUSION: The rate of fat oxidation is higher during rowing exercise than cycling, across a range of exercise intensities, despite similar oxygen uptake. It is possible that the greater muscle mass recruited during rowing may distribute the metabolic stress and facilitate fat oxidation. These results indicate that when prescribing exercise to optimise fat oxidation, the exercise modality should be such that it recruits a larger muscle mass.

Accumulated oxygen deficit on a continuous incremental exercise test

Exercise tolerance is limited by maximal accumulated oxygen deficit (MAOD) for constant work rate exercise tests (CW) in the severe intensity domain (J Appl Physiol 64: 50–60, 1988). Unpublished data from our laboratory indicate that endurance trained subjects performing a continuous incremental test (CI) reach exhaustion in concert with MAOD. The purpose of the present investigation was to determine whether untrained subjects also achieve MAOD on an exhaustive CI. On a motorized treadmill, eight recreationally active males (VO2max 50.9 ± 6.5 mL×kg−1×min−1) completed: a) sub-maximal tests (SMT) to establish the grade-VO2 relationship at the speed that elicited 4 mM blood [lactate] (S4), b) a CI at S4 to determine VO2max and accumulated oxygen deficit (AODCI), c) a CW to confirm VO2max, and d) a CW that induced exhaustion in 2–4 min to ascertain MAOD. O2 demand was linearly extrapolated from the VO2 response at each grade on the SMT. Data were analyzed by repeated measures ANOVA. Each subject manifested blood [lactate] > 8.0 mM and RER > 1.10 on the CI. Peak VO2 on the CI (3.93 ± 0.56 L×min−1) tended (p = 0.054) to be greater than on the CW (3.85 ± 0.53 L×min−1). AODCI (38.1 ± 21.0 mL×kg−1) was significantly lower (p < 0.05) than MAOD (50.3 ± 16.6 mL×kg−1). This may be due to difficulties in the prediction of O2 demand or differences in the mechanisms of exhaustion in untrained and endurance trained subjects. Estimation of AODCI is confounded in some cases by non-linear VO2 responses, akin to a slow component, driving the measured VO2 in excess of O2 demand in the late stages of the CI.

Estimating the total energy demand for supra-maximal exercise using the V̇O 2-power regression from an incremental exercise test

The VO2-power regression and estimated total energy demand for a 6-minute supra-maximal exercise test was predicted from a continuous incremental exercise test. Sub-maximal VO2-power co-ordinates were established from the last 40 seconds (s) of 150-second exercise stages. The precision of the estimated total energy demand was determined using the 95% confidence interval (95% CI) of the estimated total energy demand. The linearity of the individual VO2-power regression equations was determined using Pearson's correlation coefficient. The mean 95% CI of the estimated total energy demand was 5.9 +/- 2.5 mL O2 Eq x kg(-1) x min(-1), and the mean correlation coefficient was 0.9942 +/- 0.0042. The current study contends that the sub-maximal VO2-power co-ordinates from a continuous incremental exercise test can be used to estimate supra-maximal energy demand without compromising the precision of the accumulated oxygen deficit (AOD) method.

A method to determine mechanical energy conservation and efficiency in equine gait: a preliminary study.

Metabolic and mechanical energy costs of locomotion can be combined to calculate locomotor efficiency, which is the quotient of the mechanical energy and metabolic costs. The purpose of this pilot study was to evaluate the mechanical and metabolic energy costs of locomotion at a range of 7 trotting speeds (2.5 to 6.2 m/s) on a level treadmill. A single, sound Thoroughbred horse was modelled as a system of 15 linked segments incorporating all 4 limbs, head, neck and trunk. The horse performed a continuous incremental exercise test at increasing trotting speeds while VO2 was recorded using a breath-by-breath gas analysis system. Positional data were recorded concurrently at 100 Hz using a 2-camera infrared kinematic system. Mechanical energy cost was calculated for 3-6 strides per speed increment, and metabolic data were obtained during the last 15 s of each speed step. Mechanical energy cost increased linearly from 3.3 J/kg/m at 2.5 m/s to a value of 5.31 J/kg/m at 6.2 m/s, and the within-subject variability was low at each of the speed steps. This analysis accounted for the important energy-conserving mechanisms of energy exchange within and between segments of the link segment model. Within-segment energy conservation remained approximately constant as speed increased, whereas between-segment conservation increased from 1040 to 4502 J/stride. The combination of both metabolic and mechanical costs of locomotion yielded an inverted bell-shaped curve of 'apparent' efficiency across the speed increments, with the maximum value occurring when metabolic cost was lowest at 3.8 m/s.

Physiological Responses to Short-Duration High-Intensity Intermittent Rowing

Six highly trained male elite rowers performed five sets of intermittent exercise on a rowing ergometer at competition intensity. Each set consisted of eight cycles of 15 s work and 15 s rest (15/15). Each set was repeated at 30-s intervals. Oxygen uptake and heart rate were continuously measured during each set. During the period between sets, microsamples of arterialized blood were obtained and later analyzed for lactate concentration. On two separate days, each subject also performed a 6-min bout of "all-out" exercise and a continuous incremental exercise test to fatigue on the rowing ergometer. During the intermittent rowing, no significant differences were detected in any of the measured variables between sets. Heart rate, oxygen uptake, and blood lactate averaged 89, 78, and 32%, respectively, of peak values measured during the continuous incremental exercise test. It is concluded that with rowing, the investigated 15/15 intermittent exercise model demands relatively high aerobic loading and low glycolytic activity. This exercise protocol may be considered an alternative model for training which allows rowers to work for prolonged periods of time at or slightly above competition intensity.

Effect of Oral Creatine Supplementation on Respiratory Gas Exchange and Blood Lactate Accumulation during Steady-State Incremental Treadmill Exercise and Recovery in Man

1. Oral creatine supplementation has been shown to increase muscle creatine and phosphocreatine concentrations with consequent benefits on performance during short-term maximal exercise. However, recently there have been anecdotal reports that creatine supplementation can also influence the pattern of substrate utilization and improve performance during more prolonged, submaximal exercise, which, based on recent experimental evidence, may have some scientific justification. 2. Eight men performed a continuous incremental exercise test running at 10 km/h on a motorized treadmill at predetermined workloads from 50% to 90% of maximal oxygen uptake, before and after 5 days of creatine supplementation (4 x 5 g daily). Exercise was performed for 6 min at each workload to achieve a steady state, and respiratory gas exchange and blood lactate concentrations were measured during the last 30 s at each workload. Measurements were also made at 5-min intervals for the first 15 min of recovery. 3. The results showed no measurable effect of creatine supplementation on respiratory gas exchange and blood lactate concentrations during either incremental submaximal exercise or recovery. This suggests that creatine supplementation does not influence substrate utilization during and after this type of exercise.