Differences between measurements made on day 1 and day 2 of heart rate, gas exchange, and perceptual responses are presented in Table 1. The slope of the change in oxygen uptake for subject 1 on day 1 and day 2 are illustrated in Figures 2 and 3, respectively. The mean maximal oxygen uptake of the subjects was 50.0 ± 11.7 ml/kg/min on day 1 and 49.6 ± 11 ml/ kg/min on day 2. This difference was not significant (NS). Accordingly, treadmill time was not different between day 1 (9.0 ± 1.4 minutes) and day 2 (9.3 ± 1.2 minutes). The mean maximal perceived exertion was 19.8 ±0.4 and 20 ±0 on days 1 and 2, respectively (NS), and the mean maximal respiratory exchange ratios were 1.30±0.10 and 1.24±0.12 on days 1 and 2, respectively (NS). These values are consistent with maximal effort on both days. http://www.medicine-against-diabetes.net/
Each of the data points in Figures 2 and 3 represents the slope of a 30-breath running recursive sample, where each breath is a running recursive eight-breath average, for subject 1. Since a single eight-breath average sample is an average of the current breath and the seven preceding it, each data point in Figures 2 and 3 represents the slope of the line derived from 30 such samples at that point in time (Fig 1). Open squares denote samples in which the slope in oxygen uptake was significantly greater than zero, while closed squares denote samples that did not differ from zero. On day 1, the slope did not differ significantly from zero at peak exercise, ie, a plateau appeared to occur. This was contrasted by day 2, in which the slope at peak exercise was significantly greater than zero. Irrespective of the response at peak exercise, considerable variability in the slope of the change in oxygen uptake was observed throughout submaximal exercise, including samples that both differed and did not differ from zero. From Figure 3, the subject may have been judged to “plateau” and thus reached physiologic maximum, at three points submaximally.
Variability in the slope of the change in oxygen uptake during progressive exercise was similar in the other subjects. Although all six subjects demonstrated a plateau (slope not different from zero at peak exercise) on day 1, this observation was not made in three of the subjects on repeat testing (subjects 1, 2, and 5). Further, variability in the slope of the change in oxygen uptake differed greatly for some subjects between tests (Table 1), as illustrated for subject 1 in Figures 2 and 3. It should be noted farther that the distribution of the slopes was non-Gaussian in all but one of the 12 tests. This suggests that the frequency of obtaining a given oxygen uptake value over the course of the exercise test did not fit a normal distribution curve.
Table 1—Heart Rate, Perceived Exertion, and Gas Exchange Responses on Days 1 and 2
|Maximal Heart Rate, beats/min||MaximalPerceivedExertion||MaximalOxygenUptake,
|Average Oxygen Uptake Slope* ml 0^min/kg min||SD ofthe Slope, mlO^min/kg min||RampRatefml/kg/min||MaximalHeartRate,
|SD of the Slope, ml 0,/min/kg min|
|Mean±SD||180±12||19.8 ±0.40||50.0± 11.7||3.80 ±0.62||5.1 ±4.8||4.0±1.9||181 ±8||20±0||49.6±11.0||3.04 ±0.87||6.9 ±4.5|
Figure 2. Individual slopes in oxygen uptake regressed with time for subject 1 on day 1. Each darkened square represents a 30 eight-breath average sample in which the slope was not significantly greater than zero. Each open square denotes those that were greater than zero.
Figure 3. Individual slopes in oxygen uptake regressed with time for subject 1 on day 2. Each darkened square represents a 30 eight-breath average sample in which the slope was not significantly greater than zero. Each open square denotes those that were greater than zero.