Incremental exercise

Abstract: WASSERMAN, KARLMAN, BRIAN J. WHIPP, SANKAR IX KOYAL, AND WILLIAM L. BEAVER. Anaerobic threshold and respiratory gas exchange during exercise. J. Appl. Physiol. 35(Z): 236-243. 1973.-Alterations in gas exchange were studied in man during exercise increasing in increments of 15 w each minute, to determine the noninvasive indicators of the onset of metabolic acidosis (anaerobic metabolism). Expired airflow and CO 2 and 0 2 tensions at the mouth during the breath were continuously monitored with rapid1 y responding gas analyzers. These measurements were recorded directly as well as processed by a minicomputer, on-line, to give minute ventilation (VE), COP production #co& 02 consumption (voz), and the gas exchange ratio (R), breath-by-breath. The anaerobic threshold (AT) could be identified by the point of I) nonlinear increase in VE, 2) nonlinear increase in Vco2, 3) an increase in end-tidal 02 without a corresponding decrease in endtidal COz, and 4) an increase in R, as work rate was increased during an incremental exercise test. Of these measurements, R was found least sensitive. The AT was determined in 85 normal subjects between 17 and 91 years of age, by these techniques. The lower limit of normal was 45 w (KTo 2 = 1 liter/min), while values for very fit normal adults were as high as 180 w. The patients studied with cardiac disease above functional class I have lower anaerobic thresholds than the least fit normal subjects. The I-min incremental work rate test is associated with changes in gas exchange which can be used as sensitive on-line indicators of the AT, thus bypassing the need for measuring arterial lactate or acid-base parameters to indicate anaerobiosis.

Abstract: Twelve normal men performed 1-min incremental exercise tests to exhaustion in approximately 10 min on both treadmill and cycle ergometer. The maximal O2 uptake (VO2 max) and anaerobic threshold (AT) were higher (6 and 13%, respectively) on the treadmill than the cycle; the AT was reached at about 50% of VO2 max on both ergometers. Maximal CO2 output, heart rate, and O2 pulse were also slightly, but significantly higher on the treadmill. Maximal ventilation, gas exchange ratio, and ventilatory equivalents for O2 and CO2 for both forms of exercise were not significantly different. To determine the optimum exercise test for both treadmill and cycle, we exercised five of the subjects at various work rate increments on both ergometers in a randomized design. The treadmill increments were 0.8, 1.7, 2.5, and 4.2%/min at a constant speed of 3.4 mph, and 1.7 and 4.2%/min at 4.5 mph. Cycle increments were 15, 30, and 60 W/min. The VO2 max was significantly higher on tests where the increment magnitude was large enough to induce test durations of 8-17 min, but the AT was independent of test duration. Thus, for evaluating cardiopulmonary function with incremental exercise testing by either treadmill or cycle, we suggest selecting a work rate increment to bring the subject to the limit of his tolerance in about 10 min.

Abstract: Though exercise training is part of most pulmonary rehabilitation programs, whether there is a physiologic basis for increased exercise tolerance is unclear. We sought to determine whether patients with chronic obstructive pulmonary disease (COPD) are capable of obtaining a physiologic training effect, as manifested by a reduction in blood lactate and ventilation (VE) at a given level of exercise. We also sought to determine whether training work rate determines the size of the training effect. Nineteen participants with COPD of predominantly moderate severity in an inpatient rehabilitation program performed two cycle ergometer exercise tests at a low and a high work rate for 15 min or to tolerance and also an incremental exercise test to tolerance. Arterial blood was sampled for blood gas and lactate analyses. Identical tests were performed before and after 5-day-per-week cycle ergometer training for 8 wk either for 45 min/day at a high work rate (average, 71 W) or for a proportionally longer time at a low work rate (average, 30 W). Average FEV1 was 56 +/- 12% predicted and did not change with training. Peak exercise lactate (average, 6.5 mEq/L) was not correlated with FEV1. For the high work rate training group, identical work rates engendered less lactate (4.5 versus 7.2 mEq/L) and less VE (48 versus 55 L/min) after training; the low work rate training group had significantly less lactate and VE decrease (p less than 0.01). Further, endurance time for the high constant work rate increased 73% in the high work rate training group but only 9% in the low work rate training group. At identical work rates, VE decrease average 2.5 L/min per mEq/L decrease in lactate (r = 0.75). We conclude that most COPD subjects studied increased blood lactate at low work rates. Many of these patients were able to achieve a physiologic training effect. Though total work was the same, training at a high work rate was more effective than was training at a low work rate. The lower VE requirement to perform exercise was in proportion to the lower lactate level, but the VE decrease for a given decrease in lactate was smaller than that seen in normal subjects (7.2 L/min/mEq/L), apparently because patients with COPD fall to hyperventilate in response to lactic acidosis (PaCO2 does not drop). These findings provide a physiologic rationale for exercise training of patients with COPD.

Abstract: Borg's rating of perceived exertion (RPE) is a widely used psycho-physical tool to assess subjective perception of effort during exercise. We evaluated the association between Borg's RPE and physiological exercise parameters in a very large population. In this cohort study, 2,560 Caucasian men and women [median age 28 (IQR 17-44) years] completed incremental exercise tests on treadmills or cycle ergometers. Heart rate, blood lactate concentration, and RPE (Borg scale 6-20) were simultaneously measured at the end of each work load. Rating of perceived exertion was strongly correlated with heart rate (r = 0.74, p 0.05). Borg's RPE seems to be an affordable, practical and valid tool for monitoring and prescribing exercise intensity, independent of gender, age, exercise modality, physical activity level and CAD status. Exercising at an RPE of 11-13 ("low") is recommended for less trained individuals, and an RPE of 13-15 may be recommended when more intense but still aerobic training is desired.