Effect of Alternating Postures on Cognitive Performance

Prolonged sitting is a risk factor for cardiovascular and musculoskeletal diseases, diabetes, several types of cancer and all-cause mortality. In combination with static and awkward postures, the prevalence of musculoskeletal diseases can increase further. Although the implementation of sit-to-stand or active workstations can help to reduce sitting time, improve physical activity at work and promote health benefits, it might also lead to changes in cognitive functions such as productivity. The purpose of this study is to evaluate the short-term effect of alternating working postures on cognitive performance for healthy people.

Measurements were made in a laboratory. They were made on two different days with an interval of 7 days between sessions. Laboratory tests were conducted in a controlled, simulated work-space located at the University of Applied Sciences Campus Linz. All laboratory measurements were made in a controlled laboratory at the campus site Linz of the University of Applied Sciences Upper Austria. Temperature, air flow, humidity, lighting conditions (artificial light only) and noise level were controlled and set to be consistent with the subjects' typical working environment.

During the laboratory measurements, subjects either stood or sat upright in an ergonomic office chair, according to the study protocol. Subjects were encouraged to work as fast and as accurately as they could. To ensure identical testing conditions between subjects and to not unduly influence physiological parameters such as heart rate variability (HRV), subjects were required to minimize excessive movement (e.g. standing up during the sitting periods).

In the first (initial) phase participants were familiarized with the study protocol. Sitting time and weekly physical activity were determined via the long version of the International Physical Activity Questionnaire (IPAQ, only on the first day of measurement). Examples of each cognitive test implemented in the cognitive phase were executed according to their guidelines. A 30 minute break in a sitting posture was used to ascertain baseline heart-rate level. Baseline heart-rate was calculated after a 20 minute rest for a 5 minute interval.

In the second (cognitive) phase subjects participated in a test battery containing five blocks. Each block consisted of a working speed test (text editing task), an attentional test (d2R-test of attention) and a reaction time test (Stroop-test). These tests lasted for 30 minutes to fulfill recommendations regarding postural changes. To simulate "common" working conditions (computer based and non-computer based tasks), digital (text editing task, Stroop-test) as well as pen \& paper (d2R-test) versions of the implemented tests were used.

For the intervention group, the cognitive blocks were executed in an alternating posture (sit - stand - sit - stand - sit) either on the first or the second day of measurement (cross-over design). To generate control periods, this procedure was executed in an sitting posture only (sit - sit - sit - sit - sit) for the non-interventional day. For the control group, both days of measurement were executed in sitting posture only (sit - sit - sit - sit - sit ).

In the third (final) phase participants were asked to estimate their workload by means of the Task Load Index questionnaire developed by the National Aeronautics and Space Administration (NASA-TLX), followed by a 30 minutes resting phase in a sitting posture. During both 30 min resting phases (initial \& final) participants watched documentaries and were encouraged not to talk.

Heart-rate and trunk movements were measured from the start of the study protocol until the next morning by means of an mobile ECG-recorder.

Eligibility Criteria:
Inclusion Criteria:

* Healthy Caucasian (no acute or chronic diseases)
* Normal weight or overweight (BMI: 18.5 - 30.0 kg/m²)
* Regular computer users
* Fluent German speakers
* Consented to participate

Exclusion Criteria:

* Obesity (BMI \> 30.0 kg/m²)
* Experience in sit-to-stand workstations
* Acute or chronic diseases
* Inability to stand
* Visual impairments that had not been corrected
* Color blindness
* Regular heavy smokers (\> 10 cigarettes /day)
* Not consented to participate