Evaluating the Accuracy of Using Fixed Ranges of METs to Categorize Exertional Intensity in a Heterogeneous Group of Healthy Individuals: Implications for Cardiorespiratory Fitness and Health Outcomes.

Background: Appropriate quantification of exertional intensity remains elusive.

Objective: To compare, in a large and heterogeneous cohort of healthy females and males, the commonly used intensity classification system (i.e.

Using ramp-incremental V̇O responses for constant-intensity exercise selection.

Despite compelling evidence to the contrary, the view that oxygen uptake (V̇O) increases linearly with exercise intensity (e.g., power output, speed) until reaching its maximum persists within the exercise physiology literature.

Measurement of a True [Formula: see text]O during a Ramp Incremental Test Is Not Confirmed by a Verification Phase.

The accuracy of an exhaustive ramp incremental (RI) test to determine maximal oxygen uptake ([Formula: see text]O) was recently questioned and the utilization of a verification phase proposed as a gold standard. This study compared the oxygen uptake ([Formula: see text]O) during a RI test to that obtained during a verification phase aimed to confirm attainment of [Formula: see text]O. Sixty-one healthy males [31 older (O) 65 ± 5 yrs; 30 younger (Y) 25 ± 4 yrs] performed a RI test (15-20 W/min for O and 25 W/min for Y).

Slow V˙O kinetics in acute hypoxia are not related to a hyperventilation-induced hypocapnia.

We examined whether slower pulmonary O uptake (V˙O) kinetics in hypoxia is a consequence of: a) hypoxia alone (lowered arterial O pressure), b) hyperventilation-induced hypocapnia (lowered arterial CO pressure), or c) a combination of both. Eleven participants performed 3-5 repetitions of step-changes in cycle ergometer power output from 20W to 80% lactate threshold in the following conditions: i) normoxia (CON; room air); ii) hypoxia (HX, inspired O = 12%; lowered end-tidal O pressure [PO] and end-tidal CO pressure [PCO]); iii) hyperventilation (HV; increased PO and lowered PCO); and iv) normocapnic hypoxia (NC-HX; lowered PO and PCO matched to CON). Ventilation was increased (relative to CON) and matched between HX, HV, and NC-HX conditions.

Formulation of evidence-based messages to promote the use of physical activity to prevent and manage Alzheimer's disease.

Background: The impending public health impact of Alzheimer's disease is tremendous. Physical activity is a promising intervention for preventing and managing Alzheimer's disease. However, there is a lack of evidence-based public health messaging to support this position.

Similar pattern of change in V̇o kinetics, vascular function, and tissue oxygen provision following an endurance training stimulus in older and young adults.

The purpose of this study was to examine the time course of changes in the oxygen uptake (V̇o) kinetics response subsequent to short-term exercise training (i.e., 24, 48, 72, and 120 h posttraining) and examine the relationship with the time course of changes in microvascular [deoxygenated hemoglobin concentration ([HHb])-to-V̇o ratio ([HHb])/V̇o)] and macrovascular [flow-mediated dilation (FMD)] O delivery to the active tissues/limbs.

Long-term Evaluation of the "Get Fit for Active Living" Program.

This study examined six- and 12-month levels of adherence to physical activity, functional changes, and psychosocial determinants of physical activity in 176 older adults who participated in the "Get Fit for Active Living (GFAL)" pilot program. Functional and psychosocial measures were conducted in person at six months; psychosocial measures and physical activity participation were assessed by telephone interview at 12 months. Ninety-five per cent were retained in the study at the six-month follow-up, and 88 per cent at 12 months.

Vascular responsiveness measured by tissue oxygen saturation reperfusion slope is sensitive to different occlusion durations and training status.

What is the central question of this study? Is the near-infrared spectroscopy-derived measure of tissue oxygen saturation (StO2) reperfusion slope sensitive to a range of ischaemic conditions, and do differences exist between trained and untrained individuals? What is the main finding and its importance? The StO2 reperfusion rate is sensitive to different occlusion durations, and changes in the reperfusion slope in response to a variety of ischaemic challenges can be used to detect differences between two groups. These data indicate that near-infrared spectroscopy-derived measures of StO2, specifically the reperfusion slope following a vascular occlusion, can be used as a sensitive measure of vascular responsiveness. The reperfusion rate of near-infrared spectroscopy-derived measures of tissue oxygen saturation (StO2) represents vascular responsiveness.

Repeatability of vascular responsiveness measures derived from near-infrared spectroscopy.

Near-infrared spectroscopy (NIRS)-derived measures of tissue oxygen saturation (StO2) have been recently shown to significantly correlate with the widely used method for noninvasively assessing vascular endothelial function, flow-mediated dilation (FMD). The purpose of this study was to examine the intraday and interday reliability of the reperfusion slope of StO2 (slope 2 StO2) and compare it to FMD Ultrasound-derived FMD was quantified following 5 min of distal cuff occlusion of the popliteal artery in nine healthy young men (26 ± 3 years). An FMD test was performed each of 4 days, with a fifth involving three tests.

Vascular responsiveness determined by near-infrared spectroscopy measures of oxygen saturation.

Vascular impairments at the macro- and microcirculatory levels are associated with increased risk for cardiovascular disease. Flow-mediated dilation (FMD) is currently the most widely used method for non-invasive assessment of vascular endothelial function. Recently, near-infrared spectroscopy (NIRS)-derived measures of tissue oxygen saturation (StO2) have been used to characterize the dynamic response of local tissue perfusion to a brief period of ischaemia.

Slower V̇O₂ Kinetics in Older Individuals: Is It Inevitable?

Introduction: The mechanisms controlling the rate of adjustment of oxidative phosphorylation have been debated for several years. Although disagreement exists as to what the prevailing mechanisms controlling the speed of the oxygen uptake (V̇O₂) kinetics are in both young and older individuals, it seems tenable that the slower V̇O₂ kinetics response typically observed in older adults is at least partly imposed by an O2 delivery limitation.

Results: Several studies have demonstrated that different interventions can speed V̇O₂ kinetics in older individuals so that this response can become similar to that observed in their young counterparts.

Exercise Intensity Thresholds: Identifying the Boundaries of Sustainable Performance.

Unlabelled: Critical power (CP), respiratory compensation point (RCP), maximal lactate steady state (MLSS), and deoxyhemoglobin breakpoint ([HHb]BP) are alternative functional indices that are thought to demarcate the highest exercise intensity that can be tolerated for long durations.

Purpose: We tested the hypothesis that CP, RCP, MLSS, and [HHb]BP occur at the same metabolic intensity by examining the pulmonary oxygen uptake (V˙)O2p and power output (PO) associated with each "threshold."

Methods: Twelve healthy men (mean ± SD age, 27 ± 3 yr) performed the following tests on a cycle ergometer: i) four to five exhaustive tests for determination of CP, ii) two to three 30-min constant-power trials for MLSS determination, and iii) a ramp incremental exercise test from which the V˙O2p and PO at RCP and [HHb]BP were determined.

Pulmonary O₂ uptake kinetics during moderate-intensity exercise transitions initiated from low versus elevated metabolic rates: insights from manipulations in cadence.

Introduction: The rate of adjustment (τ) of phase II pulmonary O₂ uptake (VO₂p) is slower when exercise transitions are initiated from an elevated baseline work rate (WR) and metabolic rate (MR). In this study, combinations of cycling cadence (40 vs. 90 rpm) and external WR were used to examine the effect of prior MR on τVO₂p.

Breath-by-breath pulmonary O2 uptake kinetics: effect of data processing on confidence in estimating model parameters.

To improve the signal-to-noise ratio of breath-by-breath pulmonary O2 uptake (V̇O2p) data, it is common practice to perform multiple step transitions, which are subsequently processed to yield an ensemble-averaged profile. The effect of different data-processing techniques on phase II V̇O2p kinetic parameter estimates (V̇O2p amplitude, time delay and phase II time constant (τV̇O2p)] and model confidence [95% confidence interval (CI95)] was examined. Young (n = 9) and older men (n = 9) performed four step transitions from a 20 W baseline to a work rate corresponding to 90% of their estimated lactate threshold on a cycle ergometer.

Faster VO(2) kinetics after eccentric contractions is explained by better matching of O(2) delivery to O(2) utilization.

Purpose: This study examined the impact of eccentric exercise-induced muscle damage on the rate of adjustment in muscle deoxygenation and pulmonary O2 uptake (VO(2p)) kinetics during moderate exercise.

Methods: Fourteen males (25 ± 3 year; mean ± SD) completed three step transitions to 90 % θL before (Pre), 24 h (Post24) and 48 h after (Post48) eccentric exercise (100 eccentric leg-press repetitions with a load corresponding to 110 % of the participant's concentric 1RM). Participants were separated into two groups: phase II VO(2p) time constant (τVO(2p)) ≤ 25 s (fast group; n = 7) or τVO(2p) > 25 s (slow group; n = 7).

Effects of age and long-term endurance training on VO2 kinetics.

Purpose: This study examined the effects of age and training status on the pulmonary oxygen uptake (VO2p) kinetics of untrained and chronically trained young, middle-age, and older groups of men.

Methods: Breath-by-breath VO2p and near-infrared spectroscopy-derived muscle deoxygenation ([HHb]) were monitored continuously in young (20-39 yr) trained (YT, n = 8) and untrained (YuT, n = 8), middle-age (40-59 yr) trained (MT, n = 9) and untrained (MuT, n = 9), and older (60-85 yr) trained (OT, n = 9) and untrained (OuT, n = 8) men. On-transient VO2p and [HHb] responses to cycling exercise at 80% of the estimated lactate threshold (three repeats) were modeled as monoexponential.

The critical role of O2 provision in the dynamic adjustment of oxidative phosphorylation.

It has been proposed that the adjustment of oxygen uptake (V˙O2) during the exercise on-transient is controlled intracellularly in young healthy individuals and that insufficient local O2 delivery plays a rate-limiting role in aging and disease only. This review shows that adequate O2 provision to the active tissues is critical in the dynamic adjustment of oxidative phosphorylation even in young healthy individuals.

Sex-related differences in muscle deoxygenation during ramp incremental exercise.

Sex-specific differences in the temporal profiles of fractional O2 extraction during incremental cycling were examined using changes in near-infrared spectroscopy (NIRS)-derived muscle deoxygenated hemoglobin concentration (Δ[HHb]) and breath-by-breath pulmonary O2 uptake ( .VO2p ) measurements. Subject's (men: n=10; women: n=10) Δ[HHb] data were normalized to 100% of the response, plotted as a function ( .

Effect of voluntary hyperventilation with supplemental CO2 on pulmonary O2 uptake and leg blood flow kinetics during moderate-intensity exercise.

Pulmonary O2 uptake (V(O₂p)) and leg blood flow (LBF) kinetics were examined at the onset of moderate-intensity exercise, during hyperventilation with and without associated hypocapnic alkalosis. Seven male subjects (25 ± 6 years old; mean ± SD) performed alternate-leg knee-extension exercise from baseline to moderate-intensity exercise (80% of estimated lactate threshold) and completed four to six repetitions for each of the following three conditions: (i) control [CON; end-tidal partial pressure of CO2 (P(ET, CO₂)) ~40 mmHg], i.e.

Flexibility of older adults aged 55-86 years and the influence of physical activity.

Cross-sectional age-related differences in flexibility of older adults aged 55-86 years of varying activity levels were examined. Shoulder abduction and hip flexion flexibility measurements were obtained from 436 individuals (205 men, 71 ± 9 years; 231 women, 72 ± 8 years). Total physical activity was assessed using the Minnesota Leisure-Time Physical Activity Questionnaire.