Metabolic Measurement System Research Articles

VALIDATION OF AEROSPORT KB1-C PORTABLE METABOLIC SYSTEM

The purpose of this study was to test the validity of the Aerosport KB1-C portable metabolic measurement system against the criterion Douglas bag method. During cycle ergometry, simultaneous measurements of minute ventilation (V E ), oxygen consumption (VO 2 ), and carbon dioxide production (VCO 2 ) were made at rest and at power outputs of 50,100,150, 200, and 250 W. No significant differences (P > 0.05) were observed for V E , VO 2 , and VCO 2 between the KB1-C and Douglas bag at 100, 150, and 250 W, while the KB1-C was significantly different (P < 0.05) from Douglas bag values at rest, 50, and 200 W. R values were found to be significantly different (P < 0.05) at 100, 150, and 200 W, while no significant differences were observed at rest, 50, and 250 W. The fractional concentrations of oxygen (F E O 2 ) and carbon dioxide (F E CO 2 ) were not significantly different at 50, 100, 200, and 250 W while values at rest and 150 W were significantly different (P < 0.05). These findings show that the Aerosport KB1-C portable rmetabolic system is acceptable for measuring oxygen uptake in the range of 1.5 and 3.5 L·min -1 using the medium flow pneumotach setting. At lower intensities, the low-flow pneumotach setting provides acceptable results.

ACCURACY OF USING RPE TO MONITOR INTENSITY OF GROUP INDOOR STATIONARY CYCLING

643 The purpose of this study was to determine the accuracy of the Borg 6-20 RPE Scale as a subjective assessment of exercise intensity during a 40-minute group indoor cycling class (spinning). Seven novice, female subjects (38 ± 6 years) participated in two separate testing sessions, first an actual spinning class, and second a maximal GXT on a cycle ergometer. In both tests, a portable metabolic measurement system was used to collect physiological measurements (VO2 and HR) while subjects indicated perceived exertion levels (Borg 6-20 RPE). Results of paired sample t-tests revealed: (1) significantly higher HR's during spinning compared to GXT at RPE 12 (t=4.22; p=0.0056); and (2) significantly lower maximal RPE's during spinning compared to GXT (t=3.45; p=0.0137) with significantly higher HR-values (at maximal RPE's) during spinning compared to GXT (t=3.60; p=0.0113). In addition a 2 × 3 ANOVA was utilized to compare the actual VO2 and the VO2 estimates based on RPE at three intensity levels indicated by RPE 12, 15, and 16. A significant interaction was found between group and intensity (F=8.97; p=0.0009). Tukey's Post Hoc Tests showed that actual VO2's obtained during spinning were significantly higher than estimated VO2's at RPE 12 and 15. These results suggest that Borg's 6-20 RPE Scale may be inaccurate when used by novice participants to subjectively monitor intensity in a group indoor stationary cycling class and that the additional use of an objective measure such as HR monitoring may be needed to insure the safety and effectiveness of the program.

The relationship between a twelve minute wheelchair push test and VO2peak in women wheelchair athletes

Field testing of able‐bodied individuals to predict cardiorespiratory endurance has been used extensively. A modification of the popular twelve‐minute walk‐run field test for individuals who use wheelchairs has been recently reported. The purpose of the present study was to assess the relationship of a twelve‐minute wheelchair push test (12WPT) in women wheelchair basketball athletes with their cardiorespiratory endurance (VO2peak). Thirteen women wheelchair basketball athletes (mean age ± SD: 26 ± 6 yr) volunteered to participate in this study. These athletes were all members of the U.S. National Women's Basketball team sent to the International Federation Games and classified for wheelchair basketball (BBC) according to the National Wheelchair Basketball Association from class 1 to 3. The group mean (± SD) subject weight was 62.5 ± 9.5 kg, percent body fat, 23.3 ± 4.6%, and years of basketball experience, 6.8 ±5.7 yr, respectively. Each subject performed a maximal incremental exercise test using an Cybex UBE isokinetic arm ergometer (ACE‐GXT). Oxygen uptake was measured breath‐by‐breath by a SensorMedics 2900™ Metabolic Measurement System. On a separate day, each athlete performed a 12WPT for maximal distance on an indoor rubberized track using a sport wheelchair. The group mean (± SD) absolute VO2peak was 1.67 ± 0.41 1‐min−1 (range 1.04–2.40 1‐min−1), peak workrate, 114 ± 32 W (range 75–175 W) and 12WPT distance, 2,115 ± 135 m (range 1950–2350 m), respectively. A two‐tailed Pearson correlation between absolute VO2peak (l‐min−1) and 12WPT distance was r = 0.30 (p > 0.05). Multiple regression analysis of these data established that the best and only significant (p ≤ 0.05) predictor of absolute VO2peak (l'mhr1) was the BBC (r = 0.60; p ≤ 0.05). In this group of wheelchair athletes, the 12WPT failed to predict absolute VO2peak (l.min−1) accurately and was not a valid measure of cardiorespiratory endurance.

Reliability and Validity of a Portable Metabolic Measurement System

The purpose of this study was to assess the reliability and validity of a portable metabolic system (TEEM 100) during submaximal and maximal (VO2max) exercise using a computer-based metabolic system as the reference system (REF). Between repeated trials of submaximal exercise at three constant loads, differences in ventilation (Ve) and oxygen consumption (VO2) were 0.2 +/- 4.9 L . min-1 and 0.03 +/- 0.10 L . min-1 for REF, and 1.9 +/- 0.7 L . min-1 and 0.00 +/- 0.17 L . min-1 for TEEM 100. Pooled intraclass reliability coefficients for Ve and VO2 calculated from the repeated submaximal trials were r = .89 and r = .94 for REF, and r = .86 and r = .94 for the TEEM 100. Respiratory exchange ratio (RER) measured by the TEEM 100 was significantly higher (p = .01) at only the lowest workload. At VO2max, the TEEM 100 recorded significantly higher values for FeO2 (p = .01) and RER (p < .001). These results suggest that the TEEM 100 provides reliable and valid measurements of VO2 during submaximal and maximal exercise.

Expired air temperature during steady-state running

While some metabolic measurement systems measure expiratory temperature to standardize gas volumes, other systems use only an estimate. This study investigated the effect of prolonged exercise on expiratory temperature near the pneumotachometer to provide a basis for its estimation when actual measurement is unavailable. Seven active females each performed two 45-min treadmill runs at identical speeds (64.5% +/- 11.8% of VO2max) in which the pneumotachometer heater control was either set to 37 degrees C or turned off. Expired air temperatures were monitored with thermocouples at the nonrebreathing valve (VAL) and 1 cm upstream (UPS) and downstream (DNS) from the pneumotachometer screens. There were no temperature differences over time for any of the conditions, and there were no differences in the VAL or UPS temperatures between the heated and unheated conditions. DNS temperature was higher during the heated condition at all time periods (P < 0.01). Mean DNS temperatures for the heated and unheated condition were 30.2 +/- 1.0 degree C and 27.9 +/- 1.1 degrees C, respectively. We conclude that expired air temperatures near the pneumotachometer remain stable during extended steady-state exercise regardless of whether the pneumotachometer is heated or not.

A respiratory gas exchange simulator for routine calibration in metabolic studies

We have developed a method for simulating respiratory gas exchange for on-line calibration of metabolic measurement systems. It utilizes a pump which intakes a mixture of atmospheric air and a known flow of precision-analysed calibration gas (21% CO2, 79% N2). It expels the resulting mixture with flow wave form and profiles of gas concentration which closely resemble those of normal expiration. Control of the calibration mixture's inflow allows the investigator to set any desired metabolic rate regardless of the minute ventilatory rate. This separation of metabolic from ventilatory rates provides a stringent test of the computational performance of the respiratory gas exchange measurement systems. The apparatus can reproduce any range of respiratory and metabolic performance (currently ranging from 0.2-5 l.min-1 O2 uptake and CO2 output) with accuracy +/- 2%.