Physical Activity & Sedentary Behavior

Around 1.000 words, estimated reading time: 5 min.

WHO_CoverIn 2015, the Regional Committee of the World Health Organization (WHO) for the European Region has set a physical activity strategy for the years 2016–2025.

The goal of this strategy is to reduce by 25% the incidence of mortality through noncommunicable conditions such as cancer, type 2 diabetes, high blood pressure, and obesity, and in general increase well-being through:

  1. promotion of physical activity
  2. reduction of sedentary behavior

Lack of physical activity and excess of sedentary behavior are two independent factors that increase the risk of developing one of the conditions targeted by the WHO.

Defining physical activity

The WHO is concerned primarily with aerobic physical activity, as its immediate health benefits are greater than strength training or mobility training.

The WHO recommendations for aerobic physical activity for adults (18-64) are:

  • at least 150 minutes of moderate-intensity aerobic physical activity throughout the week, which amounts to 2h30m per week; or
  • at least 75 minutes of vigorous-intensity aerobic physical activity throughout the week, which amounts to 1h15m per week; or
  • an equivalent combination of moderate- and vigorous-intensity aerobic activity.

For additional health benefits, adults should aim for double the amount, and increase their physical aerobic activity level to 300 minutes/ 5h (moderate-intensity) or 150 minutes/2h30m (vigorous-intensity). Furthermore, it is also recommended that adults undertake muscle-strengthening activities involving major muscle groups on 2 or more days a week.

The table below gives some examples of moderate- and vigorous-intensity aerobic physical activity. (The acronym MET stands for Metabolic Equivalent of Task. You can read more about it there, but it is not necessary to understand the rest of this post.)

moderate-and-vigorous-pa

Notice that that ‘moving/carrying loads’ does not include strength training, which is not an aerobic activity.

Sedentary behavior

Sedentary Behavior_noncontroversial
Sedentary behavior is behavior that:

  1. involves passive sitting and standing (at a desk, at home, in passive modes of transportation, etc. )
  2. reduces the amount of effort in activities of everyday life (using escalators, elevators, automatic door openers, etc.).

Below is a short list of instances of workplace sedentary behavior:

  • using the elevator, especially on the way up;
  • using the automatic door opener, even if one’s hands are free;
  • sitting during coffee breaks, especially if talking to someone else;
  • rarely changing desk height from sitting to standing, or from standing to sitting (when it is possible);
  • working for more than one hour without leaving one’s desk.

Everyday sedentary behavior includes the following choices, some of which may be more surprising than others:

  • at the supermarket, using shopping trolleys rather than shopping baskets;
  • when on an escalator, not climbing the stairs, especially on the way up;
  • taking the bus/train/car rather than walking/biking;
  • watching T.V., reading, playing video games or working on a laptop for more than one hour without leaving the couch;
  • always putting the dirty dishes in the dishwasher, even for one person only;
  • using openers to take the lid off a jar.

Sedentary behavior reduces the overall level of physical activity, and as such, increase the risks of ill-health indirectly.

“… sitting at work or watching television (…) may constitute an independent risk factor for ill health regardless of other activity levels.”

The WHO report also mentions recent research showing that sedentary behavior and in particular sitting is a risk factor independent of activity levels. There is already enough evidence to conclude that excess sedentary behavior offsets the health benefits of physical activity for conditions as serious as type 2 diabetes and cancer (although the causal link is not always well understood).

Non-life-threatening conditions associated with sedentary behavior

Sedentary behavior, and in particular sitting, is associated with increased risk of life-threatening conditions (type 2 diabetes, cardiovascular diseases, cancer), but also with non-life-threatening conditions that lower quality of life. Below are listed some of the common conditions associated with excess sitting:

  • neck pain, when moving the head to one side too quickly, but sometimes also when moving slowly;
  • shoulder joint pain, when reaching out behind on the back seat of a car, or when reaching overhead to a cupboard or a shelf;
  • lower back pain, while tying your shoes or when reaching to the floor to pick up something;
  • hip joint pain, when walking or biking;
  • knee pain, in particular when taking the stairs up or down;
  • ankles sprain from everyday activity, for instance from misstepping on high heels or on unstable ground.

Causal mechanisms between these minor conditions and sitting are understood well enough, and ordinarily, boil down to muscle imbalances, which are themselves the consequences of postural adaptations to prolonged sitting (and sometimes, prolonged standing). There is also evidence that muscle imbalances also have neurological causes due to some muscles being prone to weakness (inhibition) or tightness (hypertonicity).

Obviously, those two causes reinforce each other: some muscles that are prone to inhibition (like the glutes) are also weakened by lack of use in the seated posture (leading to “gluteal amnesia”, a common indirect cause of lower back pain).

What can we do about it?

We are spending an increasing amount of time sitting still or almost still (and in some cases, standing still or almost) at home, at the office, commuting, but also at movie theaters, that it creates a feedback loop:

  1. we engage in sedentary behavior;
  2. as a result, our aerobic fitness decreases, which makes everyday moderate-intensity aerobic activities harder;
  3. subsequently, our level of moderate-intensity aerobic activity decreases;
  4. we engage in more sedentary behavior…

However, given the WHO definition of “moderate-intensity aerobic physical activity”, and the examples given in the table above, gradually increasing one’s level of physical activity is not that difficult. For instance, one could:

  • walk the stairs down instead of taking an elevator; then walk the stairs up one story, then take the elevator, then two stories, etc.; take the elevator and stop one story early, then two stories, etc.
  • tickle one’s children for a few minutes every day, then play hide-and-seek, then play tag, then play ball.
  • at the supermarket, use a hanging basket until one has put one kilo worth of groceries, then walk back to the wheeled baskets and transfer the content; then, progressively increase the weight of the hanging basket.

None of those strategies are complicated, and they do not require a precise program to work. However, pre-existing muscle imbalances may sometimes constitute an obstacle, in which case they need to be addressed more systematically.

In future posts, we will explore some of those systematic strategies.

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