Metabolic Cost of Sitting, Standing, and Transitions
Condition: Metabolic Cost
Study type: Interventional

Summary: 
      There is already a lot of scientific evidence supporting the benefits of public health
      recommendations regarding physical activity (the accumulation of at least 150 minutes of at
      least moderate intensity physical activity per week). However, these 30 daily minutes
      represent only about 3% of the waking period. Recent data suggest that most of the population
      spends on average 8-9 hours / day of sedentary behavior (SB). SB is characterized by any
      activity with a metabolic cost (MC) below 1.5 METs, mainly actions in the sitting position.
      In fact, there is evidence that the more time spent sitting higher the risk of disease and
      mortality, with sitting directly associated with diseases such as type II diabetes,
      cardiovascular diseases and even cancer. The average life expectancy may increase by ~ 2
      years if the investigators reduce sitting about 3h/ day. Additionally, how people accumulate
      sitting time seems to be a major factor, with prolonged sitting associated with a higher risk
      of disease. Short-term experimental studies indicate that sedentary lifestyles affect energy
      balance enhancing weight gain. While there is some research regarding the MC associated with
      "sitting" and "standing" behaviors, the results are contradictory. Besides these conflicting
      results, the impact of transitions between these two types of behavior and how these
      transitions can contribute to MC increase have never been investigated.

      Our hypothesis is that, in both men and women, the simple replacement of sitting for
      "standing" may not substantially increase MC, but instead, the largest contribution may
      reside on the transitions between these two states of behavior. Therefore, the investigators
      will perform a study with the following purposes:

      Examine MC and HR associated with "sitting", "standing", and transitions between these two
      types of behavior in adults of both gender, apparently healthy with variable body composition
      profiles.
    

Detailed description: 
      Introduction Regular physical activity (PA) positively influences most physiological
      processes in the human body. Inversely, sedentary behavior (SB)-too much sitting as distinct
      from too little physical activity-contributes adversely to cardio metabolic health outcomes
      and premature mortality [1-3]. Obesity results from a long-term excess of energy consumed vs.
      energy expended, a positive energy balance [4]. While overeating certainly contributes to a
      positive energy balance, the epidemic of obesity and related metabolic disorders is also
      driven by reductions in energy expended [5]. Modern human environments are vastly different
      from those of our ancestors. Technologic developments in transportation, communications,
      workplaces, and home entertainment confer a wealth of comfort, but increase the time spent in
      SB which represents costs to human health [6]. With increased use of computers, office
      workers may remain seated for long periods of time during which metabolic cost (MC) is
      minimal, making many worksites obesogenic environments [7]. Sitting time not only contributes
      to positive energy balance but is also an independent risk factor for excess adiposity [8,9]
      and obesity [10] even among people participating in high levels of moderate-to-vigorous
      physical activity (MVPA) [11,12]. Even without performing exercise people can have markedly
      variable low intensity physical activity (LIPA) levels, which in turn substantially varies PA
      energy expenditure (PAEE) by up to 2000 kcal/day [13]. Emerging evidence supports the
      feasibility of raising daily MC by replacing office work-related SB with LIPA via workstation
      alternatives to the traditional office chair and desktop computer-based combinations [14].

      Regardless of total sitting time, evidence has been growing on the metabolic benefits of
      interrupting sitting time more often [15-17], with less focus on MC as a result from these
      breaks. There is some basic science on the differences of MC associated with "sitting" and
      "standing", however the results are contradictory [14,18]. Also, other alternatives have been
      investigated [14,19] and it seems that in terms of MC, sitting on a stability ball or using
      sit-stand/standing desks are comparable to the traditional seated condition EE (≅1.2 kcal
      min(-1)). The treadmill and pedal desks (active workstation alternatives) have been shown to
      offer the greatest promise in terms of EE (≅2-4 kcal min(-1)) [14]. Another strategy is to
      introduce walking breaks into prolonged sedentary time which according to a recent study [20]
      can yield an additional 24, 59 or 132 kcal per day, if they stood up and walked at a normal,
      self-selected pace for one, two or five minutes compared with sitting for the 8-hour working
      period. From this intervention, heart rate (HR) was also examined to assess differences
      between conditions with no significant between-condition differences for heart rate.
      Therefore, taking breaks from sitting is a potential outlet to prevent obesity and the rise
      of obesity but the real contribution of the simple action of standing up from a seated
      position and returning to the seated position (sit/stand transition) on MC and HR is yet to
      be investigated. To overcome these limitations, a randomized controlled trial will be
      conducted to examine the MC and HR associated with sitting, standing, and transitions between
      the previous behaviors in laboratory settings and using accurate methods (indirect
      calorimetry). By including this methodological approach we will be able to estimate the
      additional contribution of a "break" compared to just standing when accumulating sedentary
      time on MC and HR [18].

      Hypothesis

        1. The percent increase in MC and heart rate (HR) above resting associated with sitting,
           standing and sitting/stand transitions will be different, independently of gender, body
           composition, and age.

        2. The MC, either per kg of body weight or per kg of fat-free mass, associated with sitting
           and standing will be similar but a higher cost is expected for the sitting-to-stand
           transitions, regardless of gender, age, and FFM.

      Purposes

        1. To determine the MC differences between sitting, standing and transitions conditions,
           adjusting for the effects of gender, body composition, and age.

        2. To determine the HR differences between sitting, standing and transitions, adjusting for
           the effects of gender, body composition, and age.

      Participants Sample power analysis For sample and power calculations we used the (GPower
      software, version 3.1.9.2) and consider MC as the continuous response variable. Based on a
      pilot study with a small sample size that aimed to test the differences in MC between the
      three conditions assessed by indirect calorimetry we have an effect size of approximately
      0.385 by using repeated measures ANCOVA. Therefore we will need to study 50 participants to
      be able to reject the null hypothesis that the population means of the three experimental
      conditions are equal with probability (power) 0.8. The Type I error probability associated
      with this test of this null hypothesis is 0.05. Considering a 10% drop out rate may occur due
      to invalid data we will enroll 60 participants using a crossover design where participants
      will be randomly assigned to perform the 3 conditions in different orders.

      Sample recruitment and selection A total of 60 healthy participants, both men and women will
      be selected. Participants will be recruited through advertisements placed nearby the
      institution and volunteer to participate in this study. If inclusion criteria are present
      participants will be randomly assigned to one of the conditions' orders and participate in
      the study.

      Assessments Anthropometry Subjects will be weighed to the nearest 0.1kg wearing minimal
      clothes and without shoes and height will be measured to the nearest 0.1cm in a digital scale
      with integrated stadiometer (Seca, Hamburg, Germany) according to the standardized procedures
      described elsewhere [21]. BMI will be calculated using the formula [weight(Kg)/height2(m2)].

      Body Composition To estimate total fat mass and FFM it will be used the dual energy X-ray
      absorptiometry (Hologic Explorer-W, Waltham, USA). A whole-body scan will be performed and
      the attenuation of X-rays pulsed between 70 and 140 kV synchronously with the line frequency
      for each pixel of the scanned image will be measured.

      Resting Energy Expenditure (REE) The REE will be estimated using an open-circuit spirometry
      system (MedGraphics Corporation, Breezeex Software). Subjects will lye supine for ~45
      minutes. The calorimeter device is attached to the mask and breath-by-breath VO2 and VCO2 are
      measured for a 30 minutes period. Data will be analyzed according to procedures described
      elsewhere [22].

      MC measurement in each testing condition The MC will be estimated using an open-circuit
      spirometry system (MedGraphics Corporation, Breezeex Software). Each participant will have to
      complete 4 periods (conditions) of 10 minutes in which the calorimeter device is attached to
      the mask and breath-by-breath VO2 and VCO2 are measured for 40 minutes. The first condition
      is to remain seated in a chair, with hands placed on top of the thighs for 10 minutes,
      remaining motionless. The second condition is identical to the first but the participant is
      in an upright position (standing). Finally, in the third condition, the participant will
      perform one sitting-to-stand followed by a stand-to-sitting transition, every minute. The
      order of the three conditions will be randomly assigned. Heart rate will be measured
      continuously using a pulse oximeter that is attached to the MedGraphics system. This is a
      medical device that indirectly monitors the oxygen saturation of a patient's blood (as
      opposed to measuring oxygen saturation directly through a blood sample). Heart rate and
      oxygen consumption data will be analyzed minute-by-minute.

      Statistical Analysis Statistical analysis will be performed using SPSS Statistics version
      22.0, 2013 (SPSS Inc., Chicago, IL). Descriptive statistics (mean ± SD) will be calculated
      for all outcome measurements. Normality will be verified using the Kolmogorov-Smirnov test. A
      repeated measure ANCOVA with post hoc analysis will be used to compare the differences
      between conditions, adjusting for potential covariates (FFM and age) and considering the
      order of conditions' randomization as a between-subject effect. To test the sphericity or
      homogeneity of variances, the Mauchly's statistical test will be performed. Statistical
      significance will be set at (p<0.05)

      Risk/benefit analysis The study first aim is to assess the MC associated with sitting,
      standing, and the sitting-to-stand transitions. By doing this we will be able to estimate the
      additional contribution of the actual transition to MC comparing to just sitting or standing
      for longer periods of time. Evidence found SB to have deleterious effects on general health
      status, specifically associated with a positive energy balance that lead to adiposity and
      weight gain thus increasing the risk of obesity and related metabolic risk factors.
      Therefore, participants will only benefit with this intervention [23]. No risk will be added
      for participating in the study as no risk will be associated with the intervention itself.
      Recognized and safe techniques will be used to assess MC and body composition.

      Privacy and confidentiality of data This research will only take place if approved by the
      ethics Committee of the Faculdade de Motricidade Humana from Universidade de Lisboa and will
      be conducted in accordance with the declaration of Helsinki for human studies. All
      participants will be informed about the possible risks of the investigation before giving
      their written informed consent to participate. The collected data will be treated and
      analyzed but confidentiality and privacy will always be kept. Therefore, all the data is
      collected and treated without any personal identifier and we will never provide the code. The
      data is kept in excel and SPSS file in the faculty server connected to the Exercise and
      Health Laboratory. Later the documents received with the data of each participant will be
      destroyed after the database is constructed.

      Participants' compensation and insurance There are no expenses and costs associated with the
      participation in this study therefore participants will need no insurance. However, as
      described in the informed consent, transportation to the laboratory will be supported by the
      participants.

      Who to contact in case of emergence? Pedro Júdice.

      Conflicts of interest The authors declare that there are no conflicts of interest within this
      study.
    

Intervention name(s): Metabolic cost and HR associated with distinct postural behaviors
Intervention type(s): Other
Intervention description(s): The order of the three conditions will be randomly assigned and all will be undertaken in laboratory settings. Before engaging in the experimental conditions participants will perform anthropometric and body composition assessments and also the resting EE evaluation. All evaluations will be performed at one time only, starting at 7:00 am in the morning after an overnight fast
Allocation: Randomized
Intervention model: Crossover Assignment
Masking: None (Open Label)
Primary purpose: Basic Science
Keywords: Sitting; Standing; Transitions