Upright-working has been proven to benefit health by combating the negative effects of physical inactivity. However, long-term commitment to static standing regimens may be limited due to symptoms of musculoskeletal fatigue that may develop during prolonged static standing in the absence of facilitated weight shifting. We propose a dynamic standing approach (working while standing accompanied by small periodic stepping movements) as a more tolerable and thereby more applicative lifestyle modification.

Within-group design to study the effects of standing-and-working accompanied by periodic movement compared to standing-and-working and to sitting-and-working on measures of musculoskeletal fatigue and discomfort, and physiological measures, in healthy normal control subjects, middle-aged to older adults. Measures of musculoskeletal and subjective discomfort and fatigue will be assessed in three sessions, i.e. "seated", "static standing", and "dynamic standing" (see below). During these test sessions subjects will perform small assignments using a computer mimicking light office work, including several tests measuring attention span. The first session will be the seated condition for all participants. Sessions 2 and 3 will be randomized between static or dynamic standing.

Prior to any research procedures, written informed consent will be obtained from each subject followed by initial study eligibility screening. Eligibility screening includes clinical screening questions, including, but not limited to, questions regarding significant history of cardiovascular disease, history of lower extremity pain and fractures, back pain, and migraines.

Subjects will stand behind a height adjustable table that is positioned about 0.5 meters from a wall. For the "static standing" position subjects will be asked to stand behind the table. No specific restrictions for standing will be imposed on subjects (e.g. "do not move" or "stand quietly"). For the "dynamic standing" condition participants will stand behind the same table but received periodic cues to induce weight-shifting steps. A seated control session condition will also be used to get baseline musculoskeletal subjective ratings for the same time period. Each sitting or standing session will not exceed 4 hour. As many rest breaks will be provided to the subject as needed. The entire test session may take up to approximately 5 hours.

The experimental testing protocol will be conducted preferably in the morning over three or more different days. Each day will be dedicated to one testing condition. Subjects will stand on an anti-fatigue mat during the static and dynamic standing sessions. For the standing conditions, rest breaks (e.g. sitting or walking around) will be provided as needed. During the study session caffeine consumption will be prohibited in order to standardize the stimulant effect of caffeine across subjects.

Inclusion Criteria:

1. Healthy adults (both gender, age range 18-64 years) who are currently employed.

Exclusion Criteria:

1. Inability to stand or walk without an assistive device
2. History of symptoms in stance that preclude safe and comfortable participation, such as dizziness and lightheadedness, orthostasis, severe symptomatic leg or back musculoskeletal pain, or medication side effects
3. History of symptomatic cardiovascular or pulmonary disease
4. History of rheumatic arthritis
5. History of stroke or other neurologic conditions with residual sensorimotor deficits
6. History of chronic pain syndrome requiring narcotic analgesics
7. Neurological disorders
8. Evidence of dementia
9. Diabetics: low or poorly controlled blood glucose
10. Any other history of medical or psychiatric comorbidity precluding safe participation in the project

Not decided yet

Participants will receive a general information about the study protocol and received three conditions in a random order.