CRPC patients receiving second-line hormone treatment at Ghent University Hospital are invited to participate in this phase I 3+3 dose escalation design (escalation to next exercise dose per 3 study patients). The prescription start dose is 15min. aerobic training (50-80% maximum heart rate (HRmax). warm-up and cooling-down and 65-80%HRmax. core), 1 set with 8-10 reps. resistance training (50-60% one repetition maximum (1RM), 8 exercises) and 1 set (30s.) with 2 reps. flexibility training (5 exercises). Factors determining compliance for the dose are tolerance and safety. Tolerance for the exercise prescription will be assessed with the Borg scale of perceived exertion after every exercise. Compliant for tolerance is a score ≤16. Safety will be assessed by the visual analogue scale (VAS) (assessed by the patient) for pain and the CTCAE criteria (assessed by a trained health care provider) for bone pain after every exercise. Compliant for safety is ≤3 VAS for exercise-induced pain and \<grade 2 according to the CTCAE criteria.
