Effects of experimental weight perturbation on skeletal muscle work efficiency in human subjects
ABSTRACT Maintenance of reduced or elevated body weight results in respective decreases or increases in energy expended in physical activity, defined as 24-h energy expenditure excluding resting energy expenditure and the thermic effect of feeding, beyond those attributable to weight change. We examined skeletal muscle work efficiency by graded cycle ergometry and, in some subjects, rates of gastrocnemius muscle ATP flux during exercise by magnetic resonance spectroscopy (MRS), in 30 subjects (15 males, 15 females) at initial weight and 10% below initial weight and in 8 subjects (7 males, 1 female) at initial weight and 10% above initial weight to determine whether changes in skeletal muscle work efficiency at altered body weight were correlated with changes in the energy expended in physical activity. At reduced weight, muscle work efficiency was increased in both cycle ergometry [mean (SD) change = +26.5 (26.7)%, P < 0.001] and MRS [ATP flux change = -15.2 (23.2)%, P = 0.044] studies. Weight gain resulted in decreased muscle work efficiency by ergometry [mean (SD) change = -17.8 (20.5)%, P = 0.043]. Changes in muscle efficiency at altered body weight accounted for 35% of the change in daily energy expended in physical activity.
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ABSTRACT: Effects of weight gain induced by controlled overfeeding on physical activity. Am J Physiol Endocrinol Metab 307: E1030–E1037, 2014. First published October 7, 2014; doi:10.1152/ajpendo.00386.2014.—It is unclear whether physical activity changes following long-term overfeeding and in response to different dietary protein intakes. Twenty-five (16 males, 9 females) healthy adults (18–35 yr) with BMI ranging from 19 to 30 kg/m2 enrolled in this inpatient study. In a parallel group design, participants were fed 140% of energy needs, with 5, 15, or 25% of energy from protein, for 56 days. Participants wore an RT3 accelerometer for at least 59 days throughout baseline and during overfeeding and completed 24-h whole room metabolic chamber assessments at baseline and on days 1, 14, and 56 of overfeeding and on day 57, when the baseline energy intake was consumed, to measure percent of time active and spontaneous physical activity (SPA; kcal/day). Changes in activity were also assessed by doubly labeled water (DLW). From accelerometry, vector magnitude (VM), a weight-independent measure of activity, and activity energy expenditure (AEE) increased with weight gain during overfeeding. AEE remained increased after adjusting for changes in body composition. Activity-related energy expenditure (AREE) from DLW and percent activity and SPA in the metabolic chamber increased with overfeeding, but SPA was no longer significant after adjusting for change in body composition. Change in VM and AEE were positively correlated with weight gain; however, change in activity was not affected by protein intake. Overfeeding produces an increase in physical activity and in energy expended in physical activity after adjusting for changes in body composition, suggesting that increased activity in response to weight gain might be one mechanism to support adaptive thermogenesis.The American journal of physiology 01/2014; 307:E1030–E1037. DOI:10.1152/ajpendo.00386.2014. · 3.28 Impact Factor
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ABSTRACT: Author Affi liations: Physical Therapy Department (Messrs Resende and Magalhães and Drs Fonseca and Silva) and Graduate Program in Rehabilitation (Dr Kirkwood), Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais, Brazil . The authors have no confl ict of interests. The purpose of this study was to investigate the mechanical work of the hip, knee, and ankle in females with mild and moderate levels of knee osteoarthritis (OA). Thirty-nine women with knee OA and 39 healthy women participated in the study. Mechanical work expenditures at the hip, knee, and ankle were computed using data obtained during gait. Knee total and absorptive mechanical work was lower for the OA group. Muscle weakness and pain may have contributed to the lower mechanical effi ciency of the knee, which may help explain the lower level of physical function demonstrated by women with knee OA. phase of gait. The knowledge of these mechanical defi cits in joints proximal and distal to the knee contributed to a better understanding of the mechanical defi cits under-lying lower physical function in women with knee OA. However, the level of OA severity was not specifi ed, which emphasizes the need for further studies with more strict inclusion criteria. 9Topics in Geriatric Rehabilitation 01/2013; 29(1). DOI:10.1097/TGR.0b013e318277beee · 0.14 Impact Factor
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ABSTRACT: Objective Energetic adaptations induced by bariatric surgery have not been studied in adolescents or for extended periods postsurgery. Energetic, metabolic, and neuroendocrine responses to Roux-en-Y gastric bypass (RYGB) surgery were investigated in extremely obese adolescents.Methods At baseline and at 1.5, 6, and 12 months post-baseline, 24-h room calorimetry, body composition, and fasting blood biochemistries were measured in 11 obese adolescents relative to five matched controls.ResultsIn the RYGB group, mean weight loss was 44 ± 19 kg at 12 months. Total energy expenditure (TEE), activity EE, basal metabolic rate (BMR), sleep EE, and walking EE significantly declined by 1.5 months (P = 0.001) and remained suppressed at 6 and 12 months. Adjusted for age, sex, fat-free mass, and fat mass, EE was still lower than baseline (P = 0.001). Decreases in serum insulin, leptin, and triiodothyronine (T3), gut hormones, and urinary norepinephrine (NE) paralleled the decline in EE. Adjusted changes in TEE, BMR, and/or sleep EE were associated with decreases in insulin, homeostatic model assessment, leptin, thyroid stimulating hormone, total T3, peptide YY3-36, glucagon-like peptide-2, and urinary NE and epinephrine (P = 0.001-0.05).Conclusions Energetic adaptations in response to RYGB-induced weight loss are associated with changes in insulin, adipokines, thyroid hormones, gut hormones, and sympathetic nervous system activity and persists 12 months postsurgery.Obesity 03/2015; 23(3). DOI:10.1002/oby.20994 · 4.39 Impact Factor