• Change from baseline in isometric quadriceps peak torque (Nm/kg) [ Time Frame: baseline, after dietary intervention (6 weeks) and after dietary and strength training (14 weeks) ]
  Isokinetic peak torque measurements of knee extensors and flexors will be performed using a LIDO Multijoint II isokinetic loading dynamometer. Participants will be tested in a sitting posion with their hip flexed at approximately 90° and subjects securely strapped to the seat of the chair using adjustable trunk and waist stabilisation belts. The anatomic axis of the knee rotation at the knee joint will aligned with the machine axis of rotation to insure similar movements for all participants. Two continuous maximal repetitions of knee extensors and knee flexors will be performed concentrically at each angular velocity (60°/s and 120°/s) for peak torque recording.
• Change from baseline in handgrip strength (kg) [ Time Frame: baseline, after dietary intervention (6 weeks) and after dietary and strength training (14 weeks) ]
  Handgrip strength of the right hand will be measured to the nearest kilogram (kg) using a hand Dynamometer. Participants will be encouraged to perform a maximal contraction within approximately 4 to 5 s. After a rest of 60 s, participants will be asked to perform a second trial. The highest score of maximum voluntary contraction will be used for data analyses.
• Change from baseline in muscle mass with BIA (kg) [ Time Frame: baseline, after dietary intervention (6 weeks) and after dietary and strength training (14 weeks) ]
• Change from baseline in 6min walking test (distance in meter) [ Time Frame: baseline, after dietary intervention (6 weeks) and after dietary and strength training (14 weeks) ]
• Change from baseline in the composition of gut-microbiota [ Time Frame: baseline, after dietary intervention (6 weeks) and after dietary and strength training (14 weeks) ]
  Gene sequencing of the 16S rRNA on the stool samples are performed to identify the microbes down to genus level, as well as the microbrobiota diversity and relative abundance.
• Change from baseline in stool short-chain fatty acids (SCFAs) [ Time Frame: baseline, after dietary intervention (6 weeks) and after dietary and strength training (14 weeks) ]
  The stool short-chain fatty acids (SCFAs) will be extracted and quantitatively analysed by gas chromatography.
• Change from baseline in oxidative stress marker such as malondialdehyd [ Time Frame: baseline, after dietary intervention (6 weeks) and after dietary and strength training (14 weeks) ]
  The investigators will consider changes in plasma concentrations of oxidative stress marker such as malondialdehyde from baseline to the end of the intervention.
• Change from baseline in inflammatory marker (i.g. IL-6, TNF-alpha) [ Time Frame: baseline, after dietary intervention (6 weeks) and after dietary and strength training (14 weeks) ]
  The investigators will consider changes in plasma concentrations of Interleukin 1 (IL-1), IL-6, IL-8, IL-10, TNF-alpha
• Change from baseline in the metabolomics response [ Time Frame: baseline, after dietary intervention (6 weeks) and after dietary and strength training (14 weeks) ]
  The metabolomic response (ie all metabolites) to the interventions will be analyzed using both nuclear magnetic resonance (NMR) and mass spectrometry (MS) techniques. Patterns of metabolites will be evaluated with statistical techniques, ie discriminant analysis and principal component analysis.
• Change from baseline in the amino acid pattern [ Time Frame: baseline, after dietary intervention (6 weeks) and after dietary and strength training (14 weeks) ]
  The plasma amino acid pattern will be assessed with HPLC-MS.

The aim of this randomized, observer-blind, controlled intervention study with parallel groups is to study the effect of resistance training (2x/week for 8 weeks) with and without different goals of protein intake on muscle strength, function and mass, oxidative stress parameters and the immune system in community dwelling persons.

Participants (n = 137) will be community-dwelling older adults. After a pre-participation screening participants will be distributed randomly but stratified by sex and age to one of the 3 groups (low protein + strength training, high protein + strength training, low protein and no strength training(=control)). Study participants are eligible if they are male or female with an age between 65 and 85 years and if their cognitive status as well as their physical fitness level allows to participate at the strength training sessions. Exclusion criteria comprise chronic diseases which contraindicate the training sessions, serious cardiovascular disease, diabetic retinopathy and manifest osteoporosis, a frailty index at or above 3, medication with anticoagulants or cortisone drugs and also regular strength training during the last six months.

Primary outcome measure is the change in the Chair Stand Test. Secondary outcome measures comprise anthropometric data, functional performance tests, immunological and oxidative stress parameters, microbiota, metabolomics, proteomics and the nutritional status.

• Other: High protein intake
  6 weeks of high protein intake mainly via food (additional 1g/kg bw/d) followed by a 8 weeks resistance training (Progressive strength training in a fitness center is applied; the intensity is adjusted continuously in order to obtain a sufficient training stimulus). During the training period the protein intake remains.
• Other: Control, no intervention
  No Intervention, control
• Other: Low protein intake
  6 weeks of low protein intake (1g/kg bw/d) followed by a 8 weeks resistance training (Progressive strength training in a fitness center is applied; the intensity is adjusted continuously in order to obtain a sufficient training stimulus). During the training period the protein intake remains
• Other: Strength training
  6 weeks of different protein intake followed by a 8 weeks resistance training (Progressive strength training in a fitness center is applied; the intensity is adjusted continuously in order to obtain a sufficient training stimulus). During the training period the protein intake remains

• Experimental: Strength Training and Protein high
  6 weeks of high protein intake (additional 1g/kg bw/d) followed by a 8 weeks resistance training (Progressive strength training in a fitness center is applied; the intensity is adjusted continuously in order to obtain a sufficient training stimulus). During the training period the protein intake remains.
  Interventions:

  • Other: High protein intake
  • Other: Strength training
• Experimental: Strength Training and Protein low
  6 weeks of low protein intake (1g/kg bw/d) followed by a 8 weeks resistance training (Progressive strength training in a fitness center is applied; the intensity is adjusted continuously in order to obtain a sufficient training stimulus). During the training period the protein intake remains.
  Interventions:

  • Other: Low protein intake
  • Other: Strength training
• Control
  No Intervention.
  Intervention: Other: Control, no intervention

Inclusion Criteria:

• Males and females between the age of 65 and 85 years of age
• Adequate mental condition in order to follow the instructions and to perform the resistance exercise independently (Mini-Mental-State >23)
• Independently mobile

Exclusion Criteria:

• Chronic diseases, which contraindicate a training participation
• Serious cardiovascular diseases (congestive chronic heart failure, severe or symptomatic aortic stenosis, unstable angina pectoris, untreated arterial hypertension, cardiac arrhythmias)
• Diabetic retinopathy
• Manifest osteoporosis
• Regular use of cortisone-containing drugs
• Regular strength training (> 1x / week) in the last 6 months before inclusion