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Purpose: This study aimed to determine the magnitude of exercise-induced individual variability for waist circumference (WC) and body weight change after accounting for biological variability and measurement error. Determinants of response variability were also considered., Methods: Participants (53 ± 7.5 yr) were 181 adults (61% women) with abdominal obesity randomized to the following: control; low-amount, low-intensity exercise (LALI); high-amount, low-intensity exercise (HALI); or high-amount, high-intensity exercise (HAHI) for 24 wk. Unstructured physical activity was measured by accelerometer. The variability in response to exercise for WC and body weight (SDR) was isolated by subtracting the SD values for the change scores in the exercise group from that of the control group., Results: The variability of response due to exercise (SDR) for change in WC was 3.1, -0.3, and 3.1 cm for LALI, HALI, and HAHI groups, respectively. Corresponding values for body weight were 3.8, 2.0, and 3.5 kg for LALI, HALI, and HAHI, respectively. The high-amount exercise groups yielded the highest proportion of individuals with a clinically meaningful response. No variables predicted the response to exercise (P > 0.05)., Conclusions: Substantial variability in response to standardized exercise was observed for change in both WC and body weight after accounting for the variability not attributed to exercise. Potential determinants of the interindividual variability in response to exercise remain unclear.

Aim: To determine the separate effects of exercise amount and intensity on the rate of response for glucose and insulin variables, where rate of response was defined as the number of individuals with improvement in glucose and insulin values that was beyond the day-to-day variability of measurement., Methods: Participants were 171 sedentary, middle-aged abdominally obese adults who completed a 24-week intervention. Participants were randomly assigned to (1) no-exercise control (n = 51), (2) low-amount, low-intensity exercise (LALI, n = 38), (3) high-amount, low-intensity exercise (HALI, n = 52), or (4) high-amount, high-intensity exercise (HAHI, n = 30). Two-hour glucose, insulin area under the curve (AUC), and fasting insulin were measured during a 2-hour, 75g oral glucose challenge. The day-to-day variability for these measures was calculated to be ±2.2 mmol/L, ±940.2 pmol/L, and ±38.9 pmol/L, respectively., Results: At 24 weeks, the number of nonresponders for 2-hr glucose was 98.0%, 86.8%, 94.2%, 86.7% in the control, LALI, HALI, and HAHI groups, respectively. The number of nonresponders for insulin AUC was 88.0%, 75.7%, 75.0%, 80.0% in the control, LALI, HALI, and HAHI groups, respectively. The number of nonresponders for fasting insulin was 88.2%, 84.2%, 84.6%, 93.3% in the control, LALI, HALI, and HAHI groups, respectively. The rate of response was not different between control and any of the exercise groups for any measure (p>0.05)., Conclusion: The improvement in glucose and insulin measures did not exceed the day-to-day variability of measurement for approximately 80% of the participants independent of exercise amount or intensity.

Objective: To determine the separate effects of exercise intensity and amount on interindividual cardiorespiratory fitness (CRF) response., Participants and Methods: Participants were 121 (75 females, 62%) sedentary, middle-aged (mean [SD] age, 53.2 [7.5] years), abdominally obese adults who completed at least 90% of 5 weekly exercise sessions prescribed over a 24-week intervention. Participants were randomly assigned to (1) low-amount, low-intensity exercise (LALI) (180 and 300 kcal per session for women and men, respectively, at 50% of CRF [VO 2peak]; n=39), (2) high-amount, low-intensity exercise (HALI) (360 and 600 kcal per session for women and men, respectively, at 50% of CRF; n=51), or high-amount, high-intensity exercise (HAHI) (360 and 600 kcal per session for women and men, respectively, at 75% of CRF; n=31). Cardiorespiratory fitness was measured using a treadmill test at 4, 8, 16, and 24 weeks. The study duration was September 1, 2009, through May 31, 2013., Results: Cardiorespiratory fitness increased within all 3 groups at 24 weeks (P<.001). At 24 weeks, 38.5% (15 of 39), 17.6% (9 of 51), and 0% (0 of 31) of the participants within the LALI, HALI, and HAHI groups, respectively, were CRF nonresponders. At a fixed exercise intensity, increasing exercise amount reduced the rate of nonresponse by 50% (P=.02). At a fixed amount of exercise, increasing the exercise intensity eliminated nonresponse (P=.001). Exposure to exercise decreased the number of CRF nonresponders between 4 and 8 weeks for LALI and by 16 weeks for HALI but plateaued thereafter. For HAHI, the number of CRF nonresponders decreased continually over the 24 weeks., Conclusion: For a fixed amount of exercise, increasing exercise intensity consistent with consensus recommendations eliminated CRF nonresponse. Low-intensity exercise may not be sufficient to improve CRF for a substantial proportion of sedentary obese adults., (Copyright © 2015 Mayo Foundation for Medical Education and Research. Published by Elsevier Inc. All rights reserved.)