Kara I. Gallagher

CONTEXT: A higher duration and intensity of exercise may improve long-term weight loss. OBJECTIVE: To compare the effects of different durations and intensities of exercise on 12-month weight loss and cardiorespiratory fitness. DESIGN, SETTING, AND PARTICIPANTS: Randomized trial conducted from January 2000 through December 2001 involving 201 sedentary women (mean [SD] age, 37.0 [5.7] years; mean [SD] body mass index, 32.6 [4.2]) in a university-based weight control program. INTERVENTION: Participants were randomly assigned to 1 of 4 exercise groups (vigorous intensity/high duration; moderate intensity/high duration; moderate intensity/moderate duration; or vigorous intensity/moderate duration) based on estimated energy expenditure (1000 kcal/wk vs 2000 kcal/wk) and exercise intensity (moderate vs vigorous). All women were instructed to reduce intake of energy to between 1200 and 1500 kcal/d and dietary fat to between 20% and 30% of total energy intake. MAIN OUTCOME MEASURES: Body weight, cardiorespiratory fitness, and exercise participation. RESULTS: After exclusions, 184 of 196 randomized participants completed 12 months of treatment (94%). In intention-to-treat analysis, mean (SD) weight loss following 12 months of treatment was statistically significant (P <.001) in all exercise groups (vigorous intensity/high duration = 8.9 [7.3] kg; moderate intensity/high duration = 8.2 [7.6] kg; moderate intensity/moderate duration = 6.3 [5.6] kg; vigorous intensity/moderate duration = 7.0 [6.4] kg), with no significant difference between groups. Mean (SD) cardiorespiratory fitness levels also increased significantly (P =.04) in all groups (vigorous intensity/high duration = 22.0% [19.9%]; moderate intensity/high duration = 14.9% [18.6%]; moderate intensity/moderate duration = 13.5% [16.9%]; vigorous intensity/moderate duration = 18.9% [16.9%]), with no difference between groups. Post hoc analysis revealed that percentage weight loss at 12 months was associated with the level of physical activity performed at 6 and 12 months. Women reporting less than 150 min/wk had a mean (SD) weight loss of 4.7% [6.0%]; inconsistent (other) pattern of physical activity, 7.0% [6.9%]; 150 min/wk or more, 9.5% [7.9%]; and 200 min/wk or more of exercise, 13.6% [7.8%]. CONCLUSIONS: Significant weight loss and improved cardiorespiratory fitness were achieved through the combination of exercise and diet during 12 months, although no differences were found based on different exercise durations and intensities in this group of sedentary, overweight women.

PURPOSE: To assess the accuracy of the SenseWear Pro Armband for estimating energy expenditure during exercise. METHODS: : Forty subjects (age = 23.2 +/- 3.8 yr; body mass index = 23.8 +/- 3.1 kg x m) performed four exercises (walking, cycling, stepping, arm ergometry) with each exercise lasting 20-30 min and workload increasing at 10-min intervals. Subjects wore the SenseWear Pro Armband on the right arm, and energy expenditure was estimated using proprietary equations developed by the manufacturer. Estimated energy expenditure from the SenseWear Pro Armband was compared with energy expenditure determined from indirect open-circuit calorimetry, which served as the criterion measure. RESULTS: : When a generalized proprietary algorithm was applied to the data, the SenseWear Pro Armband significantly underestimated total energy expenditure by 14.9 +/- 17.5 kcal (6.9 +/- 8.5%) during walking exercise, 32.4 +/- 18.8 kcal (28.9 +/- 13.5%) during cycle ergometry, 28.2 +/- 20.3 kcal (17.7 +/- 11.8%) during stepping exercise, and overestimated total energy expenditure by 21.7 +/- 8.7 kcal (29.3 +/- 13.8%) during arm ergometer exercise (P < or = 0.001). At the request of the investigators, exercise-specific algorithms were developed by the manufacturer and applied to the data that resulted in nonsignificant differences in total energy expenditure between indirect calorimetry and the SenseWear Pro Armband of 4.6 +/- 18.1 kcal (2.8 +/- 9.4%), 0.3 +/- 11.3 kcal (0.9 +/- 10.7%), 2.5 +/- 18.3 kcal (0.9 +/- 11.9%), and 3.2 +/- 8.1 kcal (3.8 +/- 9.9%) for the walk, cycle ergometer, step, and arm ergometer exercises, respectively. CONCLUSIONS: It appears that it is necessary to apply exercise-specific algorithms to the SenseWear Pro Armband to enhance the accuracy of estimating energy expenditure during periods of exercise. When exercise-specific algorithms are used, the SenseWear Pro Armband provides an accurate estimate of energy expenditure when compared to indirect calorimetry during exercise periods examined in this study.

PURPOSE: This study examined ratings of perceived exertion (RPE) during resistance exercise in women. In addition, changes in blood lactic acid and biceps muscle activity assessed using electromyography (EMG) were investigated as potential mediators of RPE during resistance exercise. METHODS: Twenty female volunteers (age, 25 +/- 4 yr) performed one set of biceps curl exercise at 30%, 60%, and 90% of their one-repetition maximum (1-RM). Total work was held constant by varying the number of repetitions during each of the three intensities. The three intensities were performed in random order. RPE responses were assessed for both the active muscle (RPE-AM) and the overall body (RPE-O) following each intensity. EMG data were collected from the biceps brachii muscle during each intensity. Blood samples were taken before and following the intensities and analyzed for blood lactic acid concentration. RESULTS: A two-factor repeated-measures ANOVA showed a significant RPE (region) x intensity interaction (P < 0.02). Both RPE-AM and RPE-O increased as the intensity of exercise increased. EMG activity increased significantly (P < 0.01) as the intensity of exercise increased. A two-factor repeated measures ANOVA performed on the blood lactate data showed a significant (P < 0.04) time x intensity interaction. Postexercise [Hla] was significantly greater (P < 0.01) at 90% 1-RM than at 30% 1-RM. No significant differences were found in [Hla] between 30% and 60% 1-RM, or between 60% and 90% 1-RM. CONCLUSION: These results indicate that monitoring RPE may be a useful technique for regulating resistance exercise intensity. Moreover, blood lactate and activity of the involved muscle may mediate the relation between RPE and resistance exercise intensity.

This investigation compared ratings of perceived exertion specific to the active muscles used during resistance exercise (RPE-AM) using the 15-category Borg scale during high-intensity (HIP) and low-intensity (LIP) weight lifting. Ten men (23.2 +/- 3.6 years) and 10 women (21.8 +/- 2.7 years) performed 2 trials consisting of seven exercises: bench press (BP), leg press, latissimus dorsi pull down, triceps press, biceps curl, shoulder press, and calf raise. The HIP and LIP protocols were completed in counterbalanced order. During HIP, subjects completed 5 repetitions using 90% of 1 repetition maximum (1RM). RPE-AM was measured after every repetition. During LIP, subjects completed 15 repetitions using 30% of 1RM. RPE-AM was measured after every third repetition. RPE-AMs were greater (p <or= 0.001) for HIP than for LIP for each exercise. For example, the mean initial BP RPE was 14.11 +/- 2.08 for the HIP and 8.34 +/- 1.35 for the LIP. Performing few repetitions using heavier weight is perceived to be more difficult than lifting comparatively lighter weight with more repetitions when external work is held constant.

PURPOSE: This study examined whether psychosocial factors related to physical activity in overweight, previously sedentary women were affected by a 6-month behavioral weight loss program. In addition, these psychosocial factors were examined across levels of weight loss and self-reported physical activity in response to a weight loss intervention. METHODS: Data from 165 overweight (body mass index (BMI) = 32.7 +/- 4.2 kg.m(-2)) women (age = 37.6 +/- 5.5 yr) who participated in a comprehensive behavioral weight loss program that included behavioral education, moderate caloric restriction, and progressive home-based exercise were examined. Body weight was assessed at 0 and 6 months. Perceived benefits and barriers, physical activity self-efficacy, and physical activity processes of change were assessed at 0 and 6 months. Physical activity (minutes per week of at least moderate-intensity activity) was assessed using the 7-Day Physical Activity Recall at 0 and 6 months. RESULTS: The intervention resulted in increases in physical activity self-efficacy, behavioral processes of change, and several cognitive processes of change(P < 0.05). There was a reduction in expected barriers for physical activity (P < 0.05). Individuals with > or = 10% weight loss reported higher levels of physical activity self-efficacy, greater use of behavioral strategies to elicit social support, and fewer barriers to physical activity than those with lower levels of physical activity and less weight loss (P < 0.05). Individuals reporting higher levels of exercise also reported higher levels of physical activity self-efficacy, greater use of behavioral strategies, and fewer barriers to physical activity than those individuals with lower levels of physical activity (P < 0.05). CONCLUSION: Targeting self-efficacy, behavioral strategies, and barriers in weight management programs may improve physical activity, which may result in improved weight loss in overweight adults.