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Studies in humans and animal models provide compelling evidence for age-related skeletal muscle denervation, which may contribute to muscle fiber atrophy and loss. Skeletal muscle denervation seems relentless; however, long-term, high-intensity physical activity appears to promote muscle reinnervation. Whether 5-month resistance training (RT) enhances skeletal muscle innervation in obese older adults is unknown. This study found that neural cell-adhesion molecule, NCAM+ muscle area decreased with RT and was inversely correlated with muscle strength. NCAM1 and RUNX1 gene transcripts significantly decreased with the intervention. Type I and type II fiber grouping in the vastus lateralis did not change significantly but increases in leg press and knee extensor strength inversely correlated with type I, but not with type II, fiber grouping. RT did not modify the total number of satellite cells, their number per area, or the number associated with specific fiber subtypes or innervated/denervated fibers. Our results suggest that RT has a beneficial impact on skeletal innervation, even when started late in life by sedentary obese older adults. [ABSTRACT FROM AUTHOR]

BACKGROUND: Resistance training (RT) improves muscle strength and overall physical function in older adults. RT may be particularly important in the obese elderly who have compromised muscle function. Whether caloric restriction (CR) acts synergistically with RT to enhance function is unknown. OBJECTIVE: As the primary goal of the Improving Muscle for Functional Independence Trial (I'M FIT), we determined the effects of adding CR for weight loss on muscle and physical function responses to RT in older overweight and obese adults. DESIGN: I'M FIT was a 5-mo trial in 126 older (65-79 y) overweight and obese men and women who were randomly assigned to a progressive, 3-d/wk, moderate-intensity RT intervention with a weight-loss intervention (RT+CR) or without a weight-loss intervention (RT). The primary outcome was maximal knee extensor strength; secondary outcomes were muscle power and quality, overall physical function, and total body and thigh compositions. RESULTS: Body mass decreased in the RT+CR group but not in the RT group. Fat mass, percentage of fat, and all thigh fat volumes decreased in both groups, but only the RT+CR group lost lean mass. Adjusted postintervention body- and thigh-composition measures were all lower with RT+CR except intermuscular adipose tissue (IMAT). Knee strength, power, and quality and the 4-m gait speed increased similarly in both groups. Adjusted postintervention means for a 400-m walk time and self-reported disability were better with RT+CR with no group differences in other functional measures, including knee strength. Participants with a lower percentage of fat and IMAT at baseline exhibited a greater improvement in the 400-m walk and knee strength and power. CONCLUSIONS: RT improved body composition (including reducing IMAT) and muscle strength and physical function in obese elderly, but those with higher initial adiposity experienced less improvement. The addition of CR during RT improves mobility and does not compromise other functional adaptations to RT. These findings support the incorporation of RT into obesity treatments for this population regardless of whether CR is part of the treatment. This trial was registered at clinicaltrials.gov as NCT01049698. [ABSTRACT FROM AUTHOR]

Objectives To describe the interindividual variability in physical function responses to supervised resistance and aerobic exercise training interventions in older adults. Design Data analysis of two randomized, controlled exercise trials. Setting Community-based research centers. Participants Overweight and obese (body mass index ( BMI) ≥27.0 kg/m2) sedentary men and women aged 65 to 79 (N = 95). Intervention Five months of 4 d/wk of aerobic training ( AT, n = 40) or 3 d/wk of resistance training ( RT, n = 55). Measurements Physical function assessments: global measure of lower extremity function (Short Physical Performance Battery ( SPPB)), 400-m walk, peak aerobic capacity ( VO2peak), and knee extensor strength. Results On average, both exercise interventions significantly improved physical function. For AT, there was a 7.9% increase in VO2peak; individual absolute increases varied from 0.4 to 4.3 mL/kg per minute, and four participants (13%) showed no change or a decrease in VO2peak. For RT, knee extensor strength improved an average of 8.1%; individual increases varied from 1.2 to 63.7 Nm, and 16 participants (30%) showed no change or a decrease in strength. Usual gait speed, 400-m walk time, chair rise time, and SPPB improved for the majority of AT participants and usual gait speed, chair rise time, and SPPB improved for the majority of RT participants, but there was wide variation in the magnitude of improvement. Only change in 400-m walk time with RT was related to exercise adherence (correlation coefficient = −0.31, P = .004). Conclusion Despite sufficient levels of adherence to both exercise interventions, some participants did not improve function, and the magnitude of improvement varied widely. Additional research is needed to identify factors that optimize responsiveness to exercise to maximize its functional benefits in older adults. [ABSTRACT FROM AUTHOR]

Objective: Our primary objective was to determine the long-term effects of physical activity (PA) and weight loss (WL) on body composition in overweight/obese older adults. Secondarily, the association between change in body mass and composition on change in several cardiometabolic risk factors and mobility was evaluated., Design and Methods: 288 older (X ± SD: 67.0 ± 4.8 years), overweight/obese (BMI 32.8 ± 3.8 kg/m² ) men and women participated in this 18-month randomized, controlled trial. Treatment groups included PA + WL (n = 98), PA-only (n = 97), and a successful aging (SA) health education control (n = 93). DXA-acquired body composition measures (total body fat and lean mass), conventional biomarkers of cardiometabolic risk, and 400-m walk time were obtained at baseline and 18 months., Results: Fat mass was significantly reduced from (X ± SE) 36.5 ± 8.9 kg to 31.7 ± 9.0 kg in the PA + WL group (p < 0.01), but remained unchanged from baseline in the PA-only (-0.8 ± 3.8 kg) and SA (-0.0 ± 3.9 kg) group. Lean mass losses were three times greater in the PA + WL groups compared to PA-only or SA groups (-2.5 ± 2.8 kg vs. -0.7 ± 2.2 kg or -0.8 ± 2.4 kg, respectively; p < 0.01); yet due to a larger decrease in fat mass, percent lean mass was significantly increased over baseline in the PA + WL groups (2.1% ± 2.6%; p < 0.01). Fat mass loss was primarily responsible for WL-associated improvements in cardiometabolic risk factors, while reduction in body weight, regardless of compartment, was significantly associated with improved mobility., Conclusion: This 18-month PA + WL program resulted in a significant reduction in percent body fat with a concomitant increase in percent body lean mass. Shifts in body weight and composition were associated with favorable changes in clinical parameters of cardiometabolic risk and mobility. Moderate PA without WL had no effect on body composition., (Copyright © 2013 The Obesity Society.)

Purpose: The purpose of this study was to evaluate the validity of three objective measures of physical activity (Accusplit Eagle 120 mechanical pedometer (AE120), NL-2000 electronic pedometer, and IDEEA pattern-recognition device) that varied in their levels of sophistication, among older adults at risk for mobility disability. In addition, we examined the potential influences of gait speed and body mass index (BMI) on step count accuracy., Methods: Step counts recorded on the three devices were compared against manual step counts made by two investigators as each participant walked 131 m around an indoor track at their preferred walking speed (N=29; 75.8+/-4.2 yr). Gait speed was determined by dividing total distance walked by time to completion. BMI was calculated from height and body mass measurements., Results: All three devices significantly underestimated steps taken (AE120=22.8+/-53.9 steps; NL-2000=4.0+/-5.8 steps; IDEEA=5.6+/-7.8 steps), but there was no significant difference between devices (P=0.084). Steps counted by the AE120, NL-2000, and IDEEA were significantly correlated with manual step counts (r=0.508, 0.980, and 0.965, respectively; P