Table 1 Exclusion criteria

1

Care dependency

2

Disability in lower extremities

3

Arthritis or arthrosis in knee or hip joints, arthritis requiring medication, or other rheumatic diseases potentially affecting joints or muscles

4

Diagnosed or suspected knee osteoarthritis (based on EULAR criteria: three symptoms and three signs); excluded if more than one of the following thee symptoms are found: morning stiffness <30 minutes, persistent knee pain, or functional limitations

5

Bilateral knee alloplastic and hip alloplastic material

6

Connective tissue disorders

7

Severe COPD (FEV₁/FVC ratio <70 % and FEV₁ < 50 % of predicted value (GOLD stage 3 or 4)

8

Unstable cardiac arrhythmias or decreased LVEF (<60 %)

9

Gut diseases affecting food absorption

10

Surgical diseases affecting ability to conduct heavy load strength exercise

11

Embodied magnetic metal

12

Endocrinological diseases potentially affecting muscles (diabetes mellitus, growth hormone-treated, sex hormone-treated, or untreated thyroid diseases)

13

Alcohol consumption >21 U/week for men and 14 U/week for women (1 U = 15.2 ml of alcohol)

14

Participation in studies using the same stable isotopically labeled tracers as this study (i.e., L-[ring-¹³C₆]phenylalanine) within the last 6 months

15

Medications: systemic corticosteroids, sex hormone therapy, anti-sex hormone therapy, anticoagulants (thrombin inhibitors, K-vitamin antagonists, heparins, pentasaccharides, factor Xa inhibitors, thrombocyte inhibitors except nonsteroidal anti-inflammatory drugs and acetylsalicylic acid).

16

>1 h of weekly heavy strength training

17

Dementia or other severe cognitive impairment

18

Not holding Danish citizenship or not fluent in Danish