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Dietary protein adequacy and lower body versus whole body resistive training in older humans

机译:老年人膳食蛋白质的充足性和下身与全身抵抗力训练的关系

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摘要

This study assessed the effects of long-term consumption of the United States Recommended Dietary Allowance (RDA) for protein by older people who were sedentary or performed resistive training (RT) on body composition, skeletal muscle size and protein metabolism, and if the number of muscle groups trained influenced the muscle hypertrophy response to RT. Twelve men and 17 women (age range 54–78 years) completed this 14 week controlled diet and exercise study. Throughout the study, each subject completely consumed daily euenergetic menus that provided the RDA of 0.8 g protein kg−1 day−1. From study weeks 3–14 (weeks RT1-RT12), 10 subjects (four men, six women) performed whole body RT (WBRT), nine subjects (four men, five women) performed lower body RT (LBRT) and 10 subjects (four men, six women) remained sedentary (SED). Both the LBRT and WBRT groups performed knee extension and flexion exercises, and the WBRT group also performed chest press and arm pull exercises (three sets per exercise at 80 % of one repetition maximum, 3 days per week for 12 weeks). From week 2 (baseline) to week RT12, muscle strength increased in muscle groups trained in the LBRT and WBRT groups, and was not changed in the SED group. From baseline to week RT12, whole body muscle mass and protein-mineral mass were not changed, fat-free mass (P = 0.004) and total body water (P = 0.013) were decreased, and percentage body fat was increased (P = 0.011) in these weight-stable older people, independent of group assignment. The RT-induced increases in mid-thigh muscle area (from computed tomography scans) were comparable in the LBRT and WBRT groups (2.13 ± 1.26 cm2 and 2.17 ± 1.24 cm2, respectively), and were different from those in the SED group, which lost muscle area (-1.74 ± 0.57 cm2; group-by-time P < 0.05). From baseline to week RT12, 24 h urinary total nitrogen excretion decreased (P < 0.001), nitrogen balance shifted from near equilibrium to positive, whole body leucine oxidation (from the infusion of L-[13C]leucine) decreased (P < 0.05) and net (postabsorptive vs. postprandial) leucine balance (P < 0.05) increased from near equilibrium to positive, with no differences in responses over time among the three groups. In conclusion, the number of muscle groups trained did not influence whole body protein metabolism or RT-induced muscle hypertrophy in older people. Most of these data are consistent with a successful adaptation to the RDA for protein. However, research should continue to question whether the decreases in fat-free mass and total body water observed in all subjects, and the decrease in mid-thigh muscle area in the SED group, are physiological accommodations, and whether the RDA for protein might be marginally inadequate for older people to maintain skeletal muscle.
机译:这项研究评估了久坐或进行抵抗训练(RT)的老年人长期食用美国推荐饮食津贴(RDA)的蛋白质对人体成分,骨骼肌大小和蛋白质代谢的影响,以及训练的肌肉群中的一部分影响了肌肉对RT的肥大反应。十二名男性和十七名女性(年龄在54-78岁之间)完成了为期14周的饮食控制和运动控制研究。在整个研究过程中,每个受试者都完全消耗了每日正常饮食菜单,提供的RDA为0.8 g蛋白质kg -1 -1 。在研究的第3-14周(RT1-RT12周)中,有10名受试者(四名男性,六名女性)进行了全身RT(WBRT),九名受试者(四名男性,五名女性)进行了下体RT(LBRT),而十名受试者(四名男子,六名妇女)久坐不动(SED)。 LBRT和WBRT组均进行了膝盖伸展和屈曲练习,WBRT组也进行了胸部按压和手臂拉拽练习(每组三套,最多重复一次的80%,每周3天,共12周)。从第2周(基线)到RT12周,LBRT和WBRT组训练的肌肉组的肌肉力量增加,而SED组则没有变化。从基线到RT12周,全身肌肉质量和蛋白质矿物质质量无变化,无脂肪质量(P = 0.004)和总水分(P = 0.013)减少,体脂百分比增加(P = 0.011) ),这些体重稳定的老年人不受小组分配的影响。 RT诱发的大腿中部肌肉区域(通过计算机断层扫描)的增加在LBRT和WBRT组中相当(2.13±1.26 cm 2 和2.17±1.24 cm 2 分别与SED组中的肌肉区不同(SED组中的肌肉区丢失了(-1.74±0.57 cm 2 ;分组时P <0.05)。从基线到RT12周,尿24h尿总氮排泄减少(P <0.001),氮平衡从接近平衡转变为阳性,全身亮氨酸氧化(注入L-[ 13 C]亮氨酸)降低(P <0.05),净(吸收后与餐后)亮氨酸平衡(P <0.05)从接近平衡增加到阳性,三组之间随时间的变化无差异。总之,受过训练的肌肉群的数量不会影响老年人的全身蛋白质代谢或RT诱发的肌肉肥大。这些数据中的大多数与成功适应蛋白质的RDA一致。然而,研究应继续质疑在所有受试者中观察到的无脂肪量和总水分的减少以及SED组中大腿中部肌肉面积的减少是否是生理适应性的,以及蛋白质的RDA是否可能对于老年人来说,维持骨骼肌的功能还远远不够。

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