Lled W′ (work doable above CP), which together predict the tolerable duration of exercise above CP. Crucially, the CP concept integrates sentinel physiological profiles—respiratory, metabolic, and contractile—within a coherent framework that has great scientific and practical utility. Rather than calibrating equivalent exercise intensities relative to metabolically distant parameters such as the lactate threshold or V˙O2max, setting the exercise intensity relative to CP unifies the profile of systemic and intramuscular responses and, if greater than CP, predicts the tolerable duration of exercise until W′ is expended, V˙O2max is attained, and intolerance is manifested. CP may be regarded as a “fatigue threshold” in the sense that it separates exercise intensity domains within which the physiological responses to exercise can (CP) be stabilized. The CP concept therefore enables important insights into 1) the principal loci of fatigue development (central vs. peripheral) at different intensities of exercise and 2) mechanisms of cardiovascular and metabolic control and their modulation by factors such as O2 delivery. Practically, the CP concept has great potential application in optimizing athletic training programs and performance as well as improving the life quality for individuals enduring chronic disease....

The quantification of maximum oxygen uptake (V̇o_{2 max}), a parameter characterizing the effective integration of the neural, cardiopulmonary, and metabolic systems, requires oxygen uptake (V̇o₂) to attain a plateau. We were interested in whether a V̇o₂plateau was consistently manifest during maximal incremental ramp cycle ergometry and also in ascertaining the relationship between this peak V̇o₂(V̇o_{2 peak}) and that determined from one, or several, maximal constant-load tests. Ventilatory and pulmonary gas-exchange variables were measured breath by breath with a turbine and mass spectrometer. On average, V̇o_{2 peak}[3.51 ± 0.8 (SD) l/min] for the ramp test did not differ from that extrapolated from the linear phase of the response in 71 subjects. In 12 of these subjects, the V̇o_{2 peak}was less than the extrapolated value by 0.1-0.4 l/min (i.e., a “plateau”), and in 19 subjects, V̇o_{2 peak}was higher by 0.05-0.4 l/min. In the remaining 40 subjects, we could not discriminate a difference. The V̇o_{2 peak}from the incremental test also did not differ from that of a single maximum constant-load test in 38 subjects or from the V̇o_{2 max}in 6 subjects who undertook a range of progressively greater discontinuous constant-load tests. A plateau in the actual V̇o₂response is therefore not an obligatory consequence of incremental exercise. Because the peak value attained was not different from the plateau in the plot of V̇o₂vs. work rate (for the constant-load tests), the V̇o_{2 peak}attained on a maximum-effort incremental test is likely to be a valid index of V̇o_{2 max}, despite no evidence of a plateau in the data themselves. However, without additional tests, one cannot be certain.

Rationale: The small conducting airways are the major site of airflow obstruction in chronic obstructive pulmonary disease and may precede emphysema development. Objectives: We hypothesized a novel computed tomography (CT) biomarker of small airway disease predicts FEV₁ decline. Methods: We analyzed 1,508 current and former smokers from COPDGene with linear regression to assess predictors of change in FEV₁ (ml/yr) over 5 years. Separate models for subjects without and with airflow obstruction were generated using baseline clinical and physiologic predictors in addition to two novel CT metrics created by parametric response mapping (PRM), a technique pairing inspiratory and expiratory CT images to define emphysema (PRM^emph) and functional small airways disease (PRM^fSAD), a measure of nonemphysematous air trapping. Measurements and Main Results: Mean (SD) rate of FEV₁ decline in ml/yr for GOLD (Global Initiative for Chronic Obstructive Lung Disease) 0–4 was as follows: 41.8 (47.7), 53.8 (57.1), 45.6 (61.1), 31.6 (43.6), and 5.1 (35.8), respectively (trend test for grades 1–4; P < 0.001). In multivariable linear regression, for participants without airflow obstruction, PRM^fSAD but not PRM^emph was associated with FEV₁ decline (P < 0.001). In GOLD 1–4 participants, both PRM^fSAD and PRM^emph were associated with FEV₁ decline (P < 0.001 and P = 0.001, respectively). Based on the model, the proportional contribution of the two CT metrics to FEV₁ decline, relative to each other, was 87% versus 13% and 68% versus 32% for PRM^fSAD and PRM^emph in GOLD 1/2 and 3/4, respectively. Conclusions: CT-assessed functional small airway disease and emphysema are associated with FEV₁ decline, but the association with functional small airway disease has greatest importance in mild-to-moderate stage chronic obstructive pulmonary disease where the rate of FEV₁ decline is the greatest. Clinical trial registered with www.clinicaltrials.gov (NCT 00608764).

This document reviews 1) the measurement properties of commonly used exercise tests in patients with chronic respiratory diseases and 2) published studies on their utilty and/or evaluation obtained from MEDLINE and Cochrane Library searches between 1990 and March 2015.Exercise tests are reliable and consistently responsive to rehabilitative and pharmacological interventions. Thresholds for clinically important changes in performance are available for several tests. In pulmonary arterial hypertension, the 6-min walk test (6MWT), peak oxygen uptake and ventilation/carbon dioxide output indices appear to be the variables most responsive to vasodilators. While bronchodilators do not always show clinically relevant effects in chronic obstructive pulmonary disease, high-intensity constant work-rate (endurance) tests (CWRET) are considerably more responsive than incremental exercise tests and 6MWTs. High-intensity CWRETs need to be standardised to reduce interindividual variability. Additional physiological information and responsiveness can be obtained from isotime measurements, particularly of inspiratory capacity and dyspnoea. Less evidence is available for the endurance shuttle walk test. Although the incremental shuttle walk test and 6MWT are reliable and less expensive than cardiopulmonary exercise testing, two repetitions are needed at baseline. All exercise tests are safe when recommended precautions are followed, with evidence suggesting that no test is safer than others.