For decades, we have been hearing about the health benefits of living a physically active lifestyle. But what about the times when we are not moving a lot; travelling to work, hours at work spent sitting, and the post-work couch time devoted to relaxing? As long as we make time for physical activity each day, we get a free pass to sit in our remaining hours, correct? Unfortunately research is beginning to show that the answer to that question is a resounding no.
The dangers of prolonged sitting is centred on its sedentary behaviour. Sedentary behaviour refers to ‘any waking behaviour characterised by an energy expenditure ≤1.5 METs while in a sitting or reclining posture’ (Sedentary Behaviour Research Network, 2012). This is conceptually different from ‘physical inactivity’, which is the lack of sufficient moderate/ vigorous intensity physical activity, and therefore both need to be considered as separate health hazards (Sedentary Work – Safe Work Australia, 2016).
“Sedentary behaviour refers to ‘any waking behaviour characterised by an energy expenditure ≤1.5 METs while in a sitting or reclining posture’
Overall exposure to sedentary behaviour (especially prolonged, unbroken sitting time) is shown to be detrimentally associated with a range of poor health outcomes, including; musculoskeletal problems, cardio-metabolic outcomes (including cardiovascular disease, diabetes and obesity), some cancers, mental ill health and health related quality of life. Furthermore, data also demonstrates a dose–response association between sitting time and all-cause mortality, independent of leisure time physical activity. As such, the simple pleasure of sitting for prolonged periods is deemed more of a risk factor for preventable morbidity and mortality in Australia than high cholesterol and is just behind high blood pressure on the risk scale.
In terms of energy expenditure, there is a relatively small differential between sitting and static standing. However, during standing, postural muscles (predominately those of the lower limbs) are continually contracting in order to keep the body upright and prevent loss of balance. Frequent contractions in these large muscle groups are largely absent while sitting. This can lead to an adverse metabolic profile with suppression of hormones related to fat metabolism and reduced glucose uptake by skeletal muscles, which can lead to insulin resistance. It is important to note that these sedentary metabolic changes do not appear to exist when incidental, light-intensity activity (including standing) is introduced every 20-30 minutes (Sedentary Work – Safe Work Australia, 2016).
What research is currently illustrating is that sitting too much is not the same as exercising too little.
But before you all go out and ditch your chair, the question is….how much sitting is too much? Findings suggest that – at least for mortality outcomes in adults – excessive can be considered somewhere near a 7 hour daily threshold without 30 minute mini-breaks (self-reported) (J.Y. Chau et al, 2013; Sedentary Work – Safe Work Australia, 2016). Interrupting prolonged periods of sitting every 20-30 minutes is supported by epidemiological studies and even as little as 2 minutes of light intensity activity (e.g. slow walking) may be sufficient for beneficial metabolic effects (Dunstan et al, 2012; Sedentary Work – Safe Work Australia, 2016).
So what can you do to limit your sitting? The simple answer is to stand up more often. Standing more could be as simple as standing up to take phone calls or to adopt the habit of standing meetings. Effectively, trying to stand up every half hour or so for a minute or 2 may well be the best daily medicine you can take.
Please browse our other blogs for further information on how to gradually start implementing standing/ introducing a sit to stand workstation within your working environment and other steps that can be taken to reduce the negative health consequences of sitting for prolonged periods of time.
MOVING MORE @ WORK – REDUCE YOUR SITTING TIME
ERGONOMICS OF A STANDING WORKSTATION
- Changing excessive sitting behaviours is an individual, organisational and national priority
- Prolonged sitting is associated with significant negative health outcomes
- Sedentary behaviour and physical inactivity are separate entities and risk factors associated with prolonged sitting (being ‘too busy’ to take a break) are NOT negated by current physical activity guidelines (moderate exercise 30 minutes a day)
- The harm associated with prolonged occupational sitting is likely due to insufficient movement and energy expenditure, lack of postural variety, diminished gravitational resistance, and a number of other mechanisms
- Small and frequent interruptions from sitting (every 20-30 minutes) and less total time sitting can start to mitigate the potential harm