This cross-over study of 12 patients with sarcoidosis will look at two different widely-used accelerometer devices. These devices are wrist worn and similar in size to a wrist-watch. They measure daily activity levels. The investigators hope to use one of these devices in the future within a randomised-controlled trial looking at using methylphenidate for the treatment of sarcoidosis-associated fatigue. In order to ensure that the investigators choose the ideal device the investigators wish to compare the GENEActiv and ActiGraph GT3X devices. Participants will be required to wear the devices for 7 days each, with 6 patients beginning with the GENEActiv device and changing to the ActiGraph device after 7 days, the remaining 6 participants starting with the Actigraph before changing to the GENEActiv. Patients will complete a short exit questionnaire about their experience with the devices and their preference. The best device will be determined by both patient preference and reliability of collecting data.

This will be a small comparator study comparing two devices (GENEActiv original and ActiGraph GT3X) in 12 patients with sarcoidosis. Participants wear one device for 7 days before returning the device, and wear the second device to wear for a further 7 day period. Each participant will wear the devices for 24 hours throughout the measurement period. The devices will be worn in a random order, randomised using sealed envelopes. They will be advised not to remove the devices during the 7 day monitoring period, with the exception of the GT3X which should be removed if the participant is bathing or swimming (they are able to shower). When each device is returned the participants will be asked to complete an exit questionnaire on their experience with the device. Before the participants wear the devices they will be asked to complete a short question regarding how tired/fatigued they feel.

The devices will be worn on the participant's non-dominant wrist. They will wear both devices in a random order (determined by randomisation at the start of the trial with regards to which device will be worn first). Six participants will start with the GENEActiv device and six will begin with the Actigraph GT3X device. The device order will be chosen randomly based upon a random number sequence generated in Microsoft Excel and placed in envelopes numbered 1 to 12.

Inclusion Criteria:

1. Male or Female aged over 18
2. Diagnosed with sarcoidosis by either; biopsy confirming non-caseating granulomas consistent with sarcoidosis, or multi-disciplinary interstitial lung disease meeting diagnosis of sarcoidosis.
3. Ambulatory patient (not wheelchair or bed-bound)
4. Able to provide written informed consent

Exclusion Criteria:

1. Unable to provide informed consent.