Concluded study following COVID19 outbreak and inability to complete study as designed.

This research project aims to determine whether supplementing with a mixture of the NAD+-precursors NA, NAM, and tryptophan can stimulate skeletal muscle mitochondrial function in physically compromised, elderly humans. Outcomes are related to mitochondrial function, energy metabolism, and physical function will be investigated.

Inclusion Criteria:

• Males and females
• Age ≥ 65 ≤ 75 years;
• BMI ≥ 20 kg/m2 ≤ 30 kg/m2;
• Normal physical activity levels: maximum of 1 hour per week engagement in a structured exercise session;
• SPPB score 4-9 and (pre-)frail;
• Subject should be in sufficient health to participate in the experiments, to be judged by the responsible physician based on the subject's medical history.

Exclusion Criteria:

• Not meeting all inclusion criteria;
• Smoking;
• Excessive alcohol use and/or drug abuse;
• Subjects with diabetes mellitus type 2;
• Significant food allergies or intolerances concerning the study products;
• Participation in another biomedical study within 1 month before the first study visit, possibly interfering with the study results;
• Medication use known to hamper subject's safety during the study procedures;
• Subjects who use selective serotonin re-uptake inhibitors (SSRI), or selective norepinephrin re-uptake inhibitors (SNRI), or monoamino oxidase inhibitors (MAO-inhibitors), or clomipramine, or St. John's wort (Hypericum perforatum);
• Subjects with contra-indications for MRI;
• Subjects who do not want to be informed about unexpected medical findings;
• Subjects who do not want that their treating physician to be informed;
• Co-morbidities to which the intervention or program the may pose as a complicating factor;
• Inability to participate and/or complete the required measurements.