We determined whether short-term weight-lifting exercise increases the synthesis rate of the major contractile proteins, myosin heavy chain (MHC), actin, and mixed muscle proteins in nonfrail elders and younger women and men. Fractional synthesis rates of mixed, MHC, and actin proteins were determined in seven healthy sedentary 23- to 32-yr-old and seven healthy 78- to 84-yr-old participants in paired studies done before and at the end of a 2-wk weight-lifting program. The in vivo rate of incorporation of 1-[(13)C]leucine into vastus lateralis MHC, actin, and mixed proteins was determined using a 14-h constant intravenous infusion of 1-[(13)C]leucine. Before exercise, the mixed and MHC fractional synthetic rates were lower in the older than in the younger participants (P < or = 0.04). Baseline actin protein synthesis rates were similar in the two groups (P = not significant). Over a 2-wk period, participants completed ten 1- to 1. 5-h weight-lifting exercise sessions: 2-3 sets per day of 9 exercises, 8-12 repetitions per set, at 60-90% of maximum voluntary muscle strength. At the end of exercise, MHC and mixed protein synthetic rates increased in the younger (88 and 121%) and older participants (105 and 182%; P < 0.001 vs. baseline). These findings indicate that MHC and mixed protein synthesis rates are reduced more than actin in advanced age. Similar to that of 23-32 yr olds, the vastus lateralis muscle in 78-84 yr olds retains the capacity to increase MHC and mixed protein synthesis rates in response to short-term resistance exercise.

Muscle atrophy (sarcopenia) in the elderly is associated with a reduced rate of muscle protein synthesis. The purpose of this study was to determine if weight-lifting exercise increases the rate of muscle protein synthesis in physically frail 76- to 92-yr-old women and men. Eight women and 4 men with mild to moderate physical frailty were enrolled in a 3-mo physical therapy program that was followed by 3 mo of supervised weight-lifting exercise. Supervised weight-lifting exercise was performed 3 days/wk at 65–100% of initial 1-repetition maximum on five upper and three lower body exercises. Compared with before resistance training, the in vivo incorporation rate of [13C]leucine into vastus lateralis muscle protein was increased after resistance training in women and men ( P < 0.01), although it was unchanged in five 82 ± 2-yr-old control subjects studied two times in 3 mo. Maximum voluntary knee extensor muscle torque production increased in the supervised resistance exercise group. These findings suggest that muscle contractile protein synthetic pathways in physically frail 76- to 92-yr-old women and men respond and adapt to the increased contractile activity associated with progressive resistance exercise training.

Objective: To determine whether alterations in diet and/or activity patterns during weekends contribute to weight gain or hinder weight loss. Methods and Procedures: Randomized, controlled trial comparing 1 year of caloric restriction (CR) with 1 year of daily exercise (EX). Subjects included 48 healthy adults (30F, 18M) aged 50-60 years with BMI 23.5-29.9 kg/m 2 . Body weight was measured on 7 consecutive mornings for a total of 165 weeks at baseline and 437 weeks during the 1-year interventions. Daily weight changes were calculated for weekends (Friday to Monday) and weekdays (Monday to Friday). Daily energy intake was estimated using food diaries; daily physical activity was measured using accelerometers. Both measures were validated against doubly labeled water (DLW). Results: At baseline, participants consistently gained weight on weekend days (+0.06 ± 0.03 kg/day, (mean ± s.e.), P = 0.02), but not on weekdays (−0.02 ± 0.02 kg/day, P = 0.18). This was attributable to higher dietary intake on Saturdays and lower physical activity on Sundays relative to weekdays (both P < 0.05). During the interventions, both CR and EX participants were in negative energy balance on weekdays (P < 0.005). On weekends, however, CR participants stopped losing weight, and EX participants gained weight (+0.08 ± 0.03 kg/day, P < 0.0001) due to higher dietary intakes on weekends. This helps to explain the slower-than-expected rate of weight loss during the interventions. Discussion: Alterations in lifestyle behaviors on weekends contribute to weight gain or cessation of weight loss on weekends. These results provide one explanation for the relatively slow rates of weight loss observed in many studies, and the difficulty with maintaining significant weight loss.

2 ) received an energy-restricted diet (943 Ϯ 26 kcal/d) for 1 week, followed by a lifestyle program of reduced dietary fat (Ϫ125 kcal/d) and increased physical activity (ϩ125 kcal/d) for 1 year. Body weight and plasma concentrations of glucose, insulin, and C-peptide during an oral glucose tolerance test were measured at baseline, 1-week, and 4-month intervals. A control group (n ϭ 24; 48 Ϯ 1 year; 110 Ϯ 5 kg; body mass index: 41 Ϯ 2 kg/m 2 ) underwent these measurements at 4-month intervals. Results: No changes in weight or glucose tolerance were observed in the control group. The intervention group had significant (p Ͻ 0.05) improvements in body weight and glucose tolerance in response to the 1-week diet, which persisted for 4 months (p Ͻ 0.001 vs. control for change in weight). A total of 19 subjects (42%) continued the intervention program for 1 year, with sustained improvements (weight: Ϫ4.6 Ϯ 1.0 kg; p Ͻ 0.001 vs. control; oral glucose tolerance test glucose area: Ϫ103 Ϯ 44 mM ⅐ min; p Ͻ 0.05 vs. control). Discussion: A modest lifestyle program facilitates weight loss and enables improvements in glucose tolerance to be maintained in obese individuals with abnormal glucose tolerance. However, attrition was high, despite the mild nature of the program.

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