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Adaptations to exercise in compensators and noncompensators in the E-MECHANIC Trial.

ABSTRACT: Rating of perceived exertion (RPE) and respiratory exchange ratio (RER) have previously been associated with acute exercise compensation. This study examined adaptations in the RPE and RER with long-term exercise training in individuals who did (noncompensators) and did not (compensators) lose the expected amount of weight. Participants (n = 110, 71.8% women, means ± SD; age 49 ± 12 yr) completed 24 wk of supervised exercise training at 65-85% V̇o_2peak to achieve a prescribed dose of 8 kcal·kg body wt^-1·wk^-1 (8 KKW) or 20 KKW. Participants were categorized as noncompensators (n = 55) or compensators (n = 55) based on the percent of expected weight loss (%EWL) achieved. Changes in RPE and RER during exercise over time (baseline, week 12, week 24) were compared by weight compensation category. Individual %EWL in relation to RPE, RER, and training intensity (%V̇o_2peak) was evaluated over the same time period. RPE and RER for a given workload decreased from baseline to week 12 and stabilized through week 24, regardless of weight compensation (time P < 0.0001). Noncompensators had a higher RPE relative to heart rate, which was partly explained by higher %V̇o_2peak. RPE and %V̇o_2peak both positively predicted %EWL, independent of age, sex, and exercise dose. Training intensity and RPE were positively associated with weight loss on the individual level, warranting further investigation into self-selection in exercise-based programs. Understanding individual heterogeneity in training intensity and behavioral responses may improve future weight management efforts that involve exercise.NEW & NOTEWORTHY In sedentary individuals with overweight and obesity, achievement of expected weight loss from long-term exercise training was associated with individual adaptations in perceived exertion. Contrary to our hypothesis, those with higher relative perceived exertion achieved a larger proportion of their expected weight loss, which was partly explained by a higher self-selected exercise training intensity.

SUBMITTER: Fearnbach SN

PROVIDER: S-EPMC7473954 | biostudies-literature | 2020 Aug

REPOSITORIES: biostudies-literature

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Adaptations to exercise in compensators and noncompensators in the E-MECHANIC Trial.

Fearnbach S Nicole SN Johannsen Neil M NM Myers Candice A CA Apolzan John W JW Johnson William D WD Earnest Conrad P CP Rood Jennifer C JC Tudor-Locke Catrine C Harris Melissa N MN Church Timothy S TS Martin Corby K CK

Journal of applied physiology (Bethesda, Md. : 1985) 20200716 2

Rating of perceived exertion (RPE) and respiratory exchange ratio (RER) have previously been associated with acute exercise compensation. This study examined adaptations in the RPE and RER with long-term exercise training in individuals who did (noncompensators) and did not (compensators) lose the expected amount of weight. Participants (<i>n</i> = 110, 71.8% women, means ± SD; age 49 ± 12 yr) completed 24 wk of supervised exercise training at 65-85% V̇o<sub>2peak</sub> to achieve a prescribed d ...[more]

PMID: 32673160

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Project description:BACKGROUND:Weight loss induced only by exercise is frequently less than expected, possibly because of compensatory changes in energy intake and/or energy expenditure. The purpose of the Examination of Mechanisms (E-MECHANIC) of Exercise-Induced Weight Compensation trial is to examine whether increased energy intake and/or reduced spontaneous activity or energy expenditure (outside of structured exercise) account for the less than expected, exercise-associated weight loss. METHODS/DESIGN:E-MECHANIC is a three-arm, 6-month randomized (1:1:1) controlled trial. The two intervention arms are exercise doses that reflect current recommendations for (1) general health (8 kcal/kg body weight per week (8 KKW), about 900 kcal/wk) and (2) weight loss (20 KKW, about 2,250 kcal/wk). The third arm, a nonexercise control group, will receive health information only. The sample will include a combined total of 198sedentary, overweight or obese (body mass index: ?25 kg/m² to ?45 kg/m²) men and women ages 18 to 65 years. The exercise dose will be supervised and tightly controlled in an exercise training laboratory. The primary outcome variables are energy intake, which will be measured using doubly labeled water (adjusted for change in energy stores) and laboratory-based food intake tests, and the discrepancy between expected weight loss and observed weight loss. Secondary outcomes include changes in resting metabolic rate (adjusted for change in body mass), activity levels (excluding structured exercise) and body composition. In an effort to guide the development of future interventions, the participants will be behaviorally phenotyped and defined as those who do compensate (that is, fail to lose the amount of weight expected) or do not compensate (that is, lose the amount of weight expected or more). DISCUSSION:In this study, we will attempt to identify underlying mechanisms to explain why exercise elicits less weight loss than expected. This information will guide the development of interventions to increase exercise-induced weight loss and maximize weight loss retention and related health benefits. TRIAL REGISTRATION:ClinicalTrials.gov ID: NCT01264406 (registration date: 20 December 2010).

Project description:BackgroundExercise is recommended for weight management, yet exercise produces less weight loss than expected, which is called weight compensation. The mechanisms for weight compensation are unclear.ObjectiveThe aim of this study was to identify the mechanisms responsible for compensation.MethodsIn a randomized controlled trial conducted at an academic research center, adults (n = 198) with overweight or obesity were randomized for 24 wk to a no-exercise control group or 1 of 2 supervised exercise groups: 8 kcal/kg of body weight/wk (KKW) or 20 KKW. Outcome assessment occurred at weeks 0 and 24. Energy intake, activity, and resting metabolic rate (RMR) were measured with doubly labeled water (DLW; with and without adjustments for change in RMR), armband accelerometers, and indirect calorimetry, respectively. Appetite and compensatory health beliefs were measured by self-report.ResultsA per-protocol analysis included 171 participants (72.5% women; mean ± SD baseline body mass index: 31.5 ± 4.7 kg/m2). Significant (P < 0.01) compensation occurred in the 8 KKW (mean: 1.5 kg; 95% CI: 0.9, 2.2 kg) and 20 KKW (mean: 2.7 kg; 95% CI: 2.0, 3.5 kg) groups, and compensation differed significantly between the exercise groups (P = 0.01). Energy intake by adjusted DLW increased significantly (P < 0.05) in the 8 KKW (mean: 90.7 kcal/d; 95% CI: 35.1, 146.4 kcal/d) and 20 KKW (mean: 123.6 kcal/d; 95% CI: 64.5, 182.7 kcal/d) groups compared with control (mean: -2.3 kcal/d; 95% CI: -58.0, 53.5 kcal/d). Results were similar without DLW adjustment. RMR and physical activity (excluding structured exercise) did not differentially change among the 3 groups. Participants with higher compared with lower compensation reported increased appetite ratings and beliefs that healthy behaviors can compensate for unhealthy behaviors. Furthermore, they increased craving for sweet foods, increased sleep disturbance, and had worsening bodily pain.ConclusionsCompensation resulted from increased energy intake and concomitant increases in appetite, which can be treated with dietary or pharmacological interventions. Compensation was not due to activity or metabolic changes. This trial was registered at clinicaltrials.gov as NCT01264406.

Project description:BackgroundPatients with chronic kidney disease have reduced cardiorespiratory fitness levels that contribute to mortality.ObjectivesThe purpose of this study was to investigate the effects of aerobic exercise on cardiopulmonary function in patients with chronic kidney disease.MethodsA total of 36 patients (mean [SD] estimated glomerular filtration rate 44 [12] ml/min/1.73m2) were randomly allocated to an exercise training or a control arm over 12 weeks. The exercise training group performed aerobic exercise for 45min 3 times/week at 65% to 80% heart rate reserve. The control group received routine care. Outcome measures were assessed at baseline and 12 weeks. Cardiopulmonary exercise testing was performed on a cycle ergometer with workload increased by 15W/min. A battery of physical function tests were administered. Habitual physical activity levels were recorded via accelerometry. Data are mean [SD].ResultsExercise training improved VO2peak as compared with the control group (exercise: 17.89 [4.18] vs 19.98 [5.49]; control: 18.29 [6.49] vs 17.36 [5.99] ml/kg/min; P<0.01). Relative O2 pulse improved following exercise, suggestive of improved left ventricular function (exercise: 0.12 [0.02] vs 0.14 [0.04]; control: 0.14 [0.05] vs 0.14 [0.04] ml/beat/kg; P=0.03). Ventilation perfusion mismatching (VE/VCO2) remained evident after exercise (exercise: 32 [5] vs 33 [5]; control: 32 [7] vs 34 [5] AU; P=0.1). Exercise did not affect the ventilatory cost of oxygen uptake (VE/VO2; exercise: 40 [7] vs 42 [8]; control: 3 [7] vs 41 [8] AU; P=0.5) and had no effect on autonomic function assessed by maximal and recovery heart rates. We found no changes in physical function or habitual physical activity levels.ConclusionsCardiopulmonary adaptations appeared to be attenuated in patients with chronic kidney disease and were not fully restored to levels observed in healthy individuals. Improvements in exercise capacity did not confer benefits to physical function. Interventions coupled with exercise may be required to enhance adaptations in chronic kidney disease. Performed according to CONSORT guidelines; ClinicalTrials.gov: NCT02050035.

Project description:PurposePreclinical radiation replicating clinical intensity modulated radiation therapy (IMRT) techniques can provide data translatable to clinical practice. For this work, treatment plans were created for oxygen-guided dose-painting in small animals using inverse-planned IMRT. Spatially varying beam intensities were achieved using 3-dimensional (3D)-printed compensators.Methods and materialsOptimized beam fluence from arbitrary gantry angles was determined using a verified model of the XRAD225Cx treatment beam. Compensators were 3D-printed with varied thickness to provide desired attenuation using copper/polylactic-acid. Spatial resolution capabilities were investigated using printed test-patterns. Following American Association of Physicists in Medicine TG119, a 5-beam IMRT plan was created for a miniaturized (∼1/8th scale) C-shape target. Electron paramagnetic resonance imaging of murine tumor oxygenation guided simultaneous integrated boost (SIB) plans conformally treating tumor to a base dose (Rx1) with boost (Rx2) based on tumor oxygenation. The 3D-printed compensator intensity modulation accuracy and precision was evaluated by individually delivering each field to a phantom containing radiochromic film and subsequent per-field gamma analysis. The methodology was validated end-to-end with composite delivery (incorporating 3D-printed tungsten/polylactic-acid beam trimmers to reduce out-of-field leakage) of the oxygen-guided SIB plan to a phantom containing film and subsequent gamma analysis.ResultsResolution test-patterns demonstrate practical printer resolution of ∼0.7 mm, corresponding to 1.0 mm bixels at the isocenter. The miniaturized C-shape plan provides planning target volume coverage (V95% = 95%) with organ sparing (organs at risk Dmax < 50%). The SIB plan to hypoxic tumor demonstrates the utility of this approach (hypoxic tumor V95%,Rx2 = 91.6%, normoxic tumor V95%,Rx1 = 95.7%, normal tissue V100%,Rx1 = 7.1%). The more challenging SIB plan to boost the normoxic tumor rim achieved normoxic tumor V95%,Rx2 = 90.9%, hypoxic tumor V95%,Rx1 = 62.7%, and normal tissue V100%,Rx2 = 5.3%. Average per-field gamma passing rates using 3%/1.0 mm, 3%/0.7 mm, and 3%/0.5 mm criteria were 98.8% ± 2.8%, 96.6% ± 4.1%, and 90.6% ± 5.9%, respectively. Composite delivery of the hypoxia boost plan and gamma analysis (3%/1 mm) gave passing results of 95.3% and 98.1% for the 2 measured orthogonal dose planes.ConclusionsThis simple and cost-effective approach using 3D-printed compensators for small-animal IMRT provides a methodology enabling preclinical studies that can be readily translated into the clinic. The presented oxygen-guided dose-painting demonstrates that this methodology will facilitate studies driving much needed biologic personalization of radiation therapy for improvements in patient outcomes.

Dataset Information

Adaptations to exercise in compensators and noncompensators in the E-MECHANIC Trial.

Publications

Adaptations to exercise in compensators and noncompensators in the E-MECHANIC Trial.

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