The focus of this study will be to determine the accuracy of the MOX, the Axivity and Fitbit, Empatica and Chill+ activity monitors (with both custom-made and available algorithms) for the classification of lying, sitting, standing, walking and climbing stairs in hospitalized older people in Acute Care for the elderly (ACE) and geriatric rehabilitation units.

In addition, the feasibility of the use of the activity monitors as a measurement tool in daily practice during hospitalization in the geriatric department will be investigated.

Adequate physical activity and exercise throughout the day are important to maximize independence and quality of life. To be able to optimize the physiotherapeutic interventions and to monitor how much geriatric patients move during hospitalization, it is desirable to follow up their activity by means of an activity monitor. In this study the investigators will determine the accuracy of three different types of activity monitors, the "MOX" placed on the thigh, the "Axivity" placed on the torso and the "Fitbit Sense", the "Empatica" and the "Chill+" placed on the wrist, for the classification of lying, sitting, standing, walking and climbing stairs in hospitalized older people in the geriatric department.

In this clinical study, 40 patients will participate of which 20 hospitalized in the geriatric rehabilitation unit at campus Pellenberg and 20 hospitalized in the acute care of elderly units at campus Gasthuisberg UZ Leuven, Belgium.

These activity monitors will remain attached for seven days so that activity can monitored during the week as well as on weekends. In an experimental test session a total of five activities (lying down, sitting, standing, walking and possibly climbing stairs) will be performed and observed, each lasting four minutes. The observations will be recorded by video where only the lower body will be in focus.

There will be daily checks to see if the activity monitors on the thigh, torso, and wrist stay in place, if the skin tolerates it well, if participants experiencing subjective discomfort, and if the measurements continue. At the end of the week, a short questionnaire will be completed on the user-friendliness of the different monitors.

The investigators will use the accuracy and patient satisfaction outcomes to decide the feasibility of using these activity monitors as a measurement tool in daily practice during hospitalization.

Inclusion Criteria:

• admitted to the rehabilitation or acute ward of UZ Leuven
• walking with the use of a walkingaid
• a signed informed consent form
• an expected stay of at least 7 days

Exclusion Criteria:

• medically unstable

Participant are admitted to a geriatric ward in UZ Leuven, Belgium and use a walkingaid.