Effect of Alternating Postures on Cognitive Performance

Study Overview
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Brief Summary
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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.

Detailed Description
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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.

Official Title
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Effect of Alternating Postures on Cognitive Performance

Conditions
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Sedentary Lifestyle

Intervention / Treatment
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* Other: Alternating working postures, first day
* Other: Alternating working postures, second day


Participation Criteria
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Eligibility Criteria
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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

Ages Eligible for Study
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Minimum Age: 18 Years
Maximum Age: 39 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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Accepts Healthy Volunteers

Study Plan
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How is the study designed?
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Design Details

Allocation: Randomized
Intervention Model: Crossover Assignment
Masking: None (Open Label)


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: Alternating postures: first day<br>Alternating body postures on the first day of measurement. Sitting body posture on the second day of measurement. | Other: Alternating working postures, first day<br>* On the first day of measurement participants execute five test battery trials in alternating postures (sit/stand/sit/stand/sit). On the second day of measurement participants execute the test battery in a sitting posture (sit/sit/sit/sit/sit).<br>|
| Experimental: Alternating postures: second day<br>Alternating body postures on the second day of measurement. Sitting body posture on the first day of measurement. | Other: Alternating working postures, second day<br>* On the first day of measurement participants execute five test battery trials in a sitting posture (sit/sit/sit/sit/sit). On the second day of measurement participants execute the test battery in alternating postures (sit/stand/sit/stand/sit).<br>|
| No Intervention: Control group<br>Sitting body posture on both days of measurement. | |

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Reaction time | Reaction time is a commonly measured parameter to describe mental states, fatigue or performance in ergonomic research. As the effect of alternating postures on reaction time is still unclear, a digital version of the Color-Word-Conflict-Stroop-Test has been implemented. It contained 190 congruent, incongruent and neutral tasks and required approximately 10 min to simulate long-lasting monotonous office screen work. The reaction time was measured and recorded automatically. Outliers (values outside of the limits of 3 standard deviations) have been automatically eliminated. The Stroop-Test is characterized by a high test-retest reliability. Due to the cross-over design of the study two days were necessary to determine the interventional effect. According to the group allocation the participants executed the Stroop-test either in an alternating or sitting posture. Differences in reaction time and accuracy between alternating and sitting days will be analyzed. | 2 experimental days | 
| Attentional performance | As the effect of alternating postures on attentional performance is still unclear, an attentional performance test called d2R-test of attention has been implemented. The d2R-test was executed as a pen and paper version. Therefore, it enabled screen breaks during the test protocol and simulated paper-related office work. The d2R-Test is characterized by a high test-retest reliability and do not require any specific previous knowledge except of rudimentary language skills. Normative values for the d2R-test are available for different countries. Attentional performance and accuracy were manually determined according to the d2R-guidelines. Due to the cross-over design of the study two days were necessary to determine the interventional effect. According to the group allocation the participants executed the d2R-test either in an alternating or sitting posture. Differences in attentional performance and accuracy between alternating and sitting days will be analyzed. | 2 experimental days | 
| Working speed | Physical efforts when performing standardized tests (e.g. standing or walking) can negatively influence cognitive parameters as well as working speed. To determine the effect of alternating postures on working speed a digital text editing task encouraging participants to fill in spaces in an ergonomic guideline text for 10 min was used. Working speed (words per minute) and accuracy (relative error) have been manually calculated. Due to the cross-over design of the study two days were necessary to determine the interventional effect. According to the group allocation the participants executed the text editing task either in an alternating or sitting posture. Differences in working speed between alternating and sitting days will be analyzed. | 2 experimental days | 
| Workload perception | Sit-to-stand workstations can evoke positive as well as negative associations. A common method to rate workload perception is the NASA-TLX questionnaire (Task Load Index, National Aeronautics and Space Administration). For reasons of simplicity and unmodified sensitivity, the short version of this questionnaire (RTLX, raw task load index), consisting of six major items, was used. Influences on workload perception based on unweighted items in the RTLX were negated due to the cross-over design. Due to the cross-over design of the study two days were necessary to determine the interventional effect. According to the group allocation the participants scored their perceived workload after executing several cognitive tests in an alternating or sitting posture. Differences in workload perception between alternating and sitting days will be analyzed. | 2 experimental days | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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postural changes, alternating postures, Cognitive performance, Height-adjustable desk, Worksite