Question

Please summarize (1-2 pages ) either on-
Part F. Chapter 1. Physical Activity Behaviors: Steps, Bouts, and High Intensity Training
OR
Part F. Chapter 2. Sedentary Behavior

Using the 2018 Physical Activity Guidelines Advisory Committee Scientific Report

Answer 1

Chapter 2. Sedentary Behavior

Sendentary behaviour is a serious problem in current lifestyle. Sedentary behaviour differs from physical inactivity and sleeping. More clear, one can be sedentary at work, at school, at home, when travelling or during leisure time. Sendentary behaviour is something which requires less energy expenditure which includes:

• Sitting while driving a vehicle, or while travelling.
• Sitting or lying down while watching television or playing electronic games.
• Sitting or lying down to read, study, write, or work at a desk or computer.

Physical inactivity is a condition when the the physical activity guidelines are not met whereas, being sendentary means sitting or lying for long periods. Therefore, someone still can be sedentary even after done with enough physical activity to meet the guidelines.

The definition given for sendentary behavior by SBRN sedentary behavior research network is acceptable by majority group. SBRN states that sedentary behavior can be defined as "any waking behaviour characterized by an energy expenditure ≤1.5 METs while in a sitting or reclining posture or lying position" .

The above definition of sedentary behavior has dual components which includes both energy expenditure and posture. The widely used sedentary behavior is postural aspect which can be easily operationalized by means of direct observation or inclinometers, but tends to ignore the energetic component.On the other hand, the energetic aspect is usually determined by indirect calorimetry or accelerometry. But this analysis has gained  criticism in relation to its inability to discriminate between postures. The cons of accelerometer is that they assess the movement rather than energy expenditure. Therefore, at best represent an indirect method of assessing energy expenditure in any population.

There are also some claims regarding the 1.5 metabolic equivalent (MET) intensity threshold which is used in SBRN definition. It is generally appropriate for distinguishing between common sitting and standing activities in healthy weight and obese adults but rather failed to coordiante with some common sitting behaviors (e.g., typing) sometimes have a MET level above this threshold. Recent studies on MET threshold for adults and children would vary; that is adult threshold may not be appropriate for children therefore the upper threshold for children should be raised to 2 METs.

There is also a need for a consensus definition of sedentary bout or sedentary break on their association with health indicators. Sedentary bout can be defined as the minimum period of uninterrupted sedentary time, not allowing any “tolerance time”.Sedentary break is the non-sedentary period in between two sedentary bouts.

Physical activity is referred to the bodily movement produced by skeletal muscles upon energy expenditure. Actually the term 'physical activity' does not specify any quality of movement rather it comprise all types, intensities, and domains though it mostly used instead of moderate-to-vigorous-intensity forms of physical activity. It should be more specific while descripting sedentary behavior, light, moderate, vigorous, or moderate-to-vigorous.

It has been observed that sedentary lifestyle is bad for health condition. It is associated with poorer health outcomes linked to more than 30 chronic diseases. Primarily, there is 112% increased risk of type 2 diabetes and 147% increase in cardio vascular diseases.

The 2008 Advisory Report infer that habitual walking of atleast 5 to 15 minutes 2 to 3 times per week improves the musculoskeletal and cardiovascular health. Before increasing the intensity of any aerobic activity, the frequency and duration should be increased. The attainment of desired physical activity may require more time for sedentary individuals.