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Physical activity in an inpatient setting is often limited to brief periods of walking. For healthy adults, public health agencies recommend a minimum of 150 min/week of moderate-intensity exercise. The authors sought to determine if meeting this activity threshold, in the absence of incidental activities of daily living, could protect skeletal muscle health during bed rest. Healthy older adults (68 ± 2 years) were randomized to 7-day bed rest with (STEP, n = 7) or without (CON, n = 10) a 2,000 steps/day intervention. Performing 2018 ± 4 steps/day did not prevent the loss of lean leg mass and had no beneficial effect on aerobic capacity, strength, or muscle fiber volume. However, the insulin response to an oral glucose challenge was preserved. Performing a block of 2,000 steps/day, in the absence of incidental activities of daily living, was insufficient to fully counter the catabolic effects of bed rest in healthy older adults. [ABSTRACT FROM AUTHOR]

Background: Brief periods of physical inactivity can compromise muscle health. Increasing dietary protein intake is potentially beneficial but complicated by difficulties reconciling anabolic potential with a realistic food volume and energy intake. We sought to determine whether increasing dietary protein quality could reduce the negative effects of physical inactivity.Methods: Twenty healthy, older men and women completed 7 days of bed rest followed by 5 days of rehabilitation. Volunteers consumed a mixed macronutrient diet (MIXED: N = 10; 68 ± 2 years; 1,722 ± 29 kcal/day; 0.97 ± 0.01 g protein/kg/day) or an isoenergetic, whey-augmented, higher protein quality diet (WHEY: N = 10; 69 ± 1 years; 1,706 ± 23 kcal/day; 0.90 ± 0.01 g protein/kg/day). Outcomes included body composition, blood glucose, insulin, and a battery of physical function tests.Results: During bed rest, both groups experienced a 20% reduction in knee extension peak torque (p < .05). The WHEY diet partially protected leg lean mass (-1,035 vs. -680 ± 138 g, MIXED vs. WHEY; p = .08) and contributed to a greater loss of body fat (-90 vs. -233 ± 152 g, MIXED vs. WHEY; p < .05). Following rehabilitation, knee extension peak torque in the WHEY group fully recovered (-10.0 vs. 2.2 ± 4.1 Nm, MIXED vs. WHEY; p = .05). Blood glucose, insulin, aerobic capacity, and Short Physical Performance Battery (SPPB) changes were similar in both dietary conditions (p > .05).Conclusions: Improving protein quality without increasing total energy intake has the potential to partially counter some of the negative effects of bed rest in older adults. [ABSTRACT FROM AUTHOR]