Get Moving!

Learning Objective (LO):  What are the effects of prolonged inactivity and what are the implications of this on everyday living?

————————————————————————————————————————–

Main take home messages:

• being sedentary for long periods of time can increase your risk of developing Type 2 Diabetes (T2D) via decreased skeletal muscle insulin sensitivity, increased visceral fat mass, decreased muscle mass
• sitting for too long is not the same as not getting enough exercise
• exercise and regulating food intake may help to negate some of the effects of prolonged sitting but they are not enough, therefore…
• move more! “moving” can be as simple as:
  • walking up the escalator instead of just standing on it while it brings you up
  • parking a little further from the store so you get to walk a bit more
  • getting up to stretch or walking around during commercial breaks if you’re watching TV

————————————————————————————————————————–

This was one of our first LOs that we did and I came across some research I found particularly interesting that I was not aware of before. This research implied that perhaps we should have guidelines for not just the minimum amount of regular physical exercise per week but also the maximum time spent sitting per week. There were some other effects of prolonged inactivity (more MSK-related), shown in Table 1, as well but I won’t be discussing them here.

There are several models that can be used when studying the effects of prolonged inactivity in humans (5):

• stopping daily endurance exercise in endurance athletes
• inducing bed rest
• increasing sitting time
• lowering daily ambulatory activity (i.e. # steps taken/day)

Of these models, increasing sitting time and lowering daily ambulatory activity seem most representative of how humans become more inactive in their daily lives and thus are probably more realistic when determining how physical inactivity can affect our health. While inducing bed rest and stopping daily endurance exercises in endurance athletes can have interesting results, the findings would likely overestimate the effects of prolonged physical inactivity. That being said, they can be useful for studying the mechanisms behind the effects (6) so I will be including results from bed rest studies in my discussion.

Thyfault et al. (6) conducted a literature review of the existing evidence that physical inactivity is harmful to health. I’ve summarized the main results found for each model used below as well as the implications of the results:

After reading that review and learning about these negative effects of prolonged physical inactivity, I had a couple more questions:

1. What effect does exercise have to help to offset these negative effects?

• I suspect that, similar to reducing energy intake, increasing amount of time exercising (or performing “moderate-to-high intensity physical activity”) will help to partially, but not fully, offset the effects
• Traditional continuous aerobic training, high intensity interval training, and resistance training have all shown to improve insulin sensitivity (8)

2. Does taking breaks over long sedentary periods (e.g. get up once an hour) help to offset these effects?

• according to Dunstan et al. (9), there are no definitive recommendations on how long people should sit or how frequent their breaks should be
• however, studies have shown a significant difference in waist circumference when comparing those who took a lot of breaks (top 25% in the ‘break’ distribution) and those who took very few (lowest 25%)

So what does all this research mean?

Personally, I used to think that since I went to the gym a lot, it would be okay to take the elevator instead of the stairs, or to take the bus instead of walk to school. However, I now realize that being healthy is not just about the amount of time you spend exercising, but also the amount of time you spend sitting, as this can greatly influence your risk of developing T2D. Since learning about this, I now take the extra effort to avoid sitting for extended periods of time and to walk whenever possible. Thank goodness I don’t have many long lectures to sit through anymore!

To reiterate the take home messages:

• being sedentary for long periods of time can increase your risk of developing Type 2 Diabetes (T2D) via decreased skeletal muscle insulin sensitivity, increased visceral fat mass, decreased muscle mass
• sitting for too long is not the same as not getting enough exercise
• exercise and regulating food intake may help to negate some of the effects of prolonged sitting but they are not enough, therefore…
• move more! “moving” can be as simple as:
  • walking up the escalator instead of just standing on it while it brings you up
  • parking a little further from the store so you get to walk a bit more
  • getting up to stretch or walking around during commercial breaks if you’re watching TV

Note: I am not saying that exercise and being aware of what you eat are not important. I am merely highlighting another important factor that contributes to health and is less well-known.

I hope everyone has a happy Thanksgiving and can take some time to get moving! It might even help your waistline ;).

Questions/comments/concerns? Feel free to leave a comment below or send me an email! Feedback is always appreciated :).

References

1.     LeBlanc AD, Spector ER, Evans HJ, Sibonga JD. Skeletal responses to space flight and the bed rest analog: a review. J Musculoskelet Neuronal Interact. 2007 Jan;7(1):33–47.

2.     Clark BC. In vivo alterations in skeletal muscle form and function after disuse atrophy. Med Sci Sports Exerc. 2009 Oct;41(10):1869–75.

3.     Matsumoto F, Trudel G, Uhthoff HK, Backman DS. Mechanical effects of immobilization on the Achilles’ tendon. Arch Phys Med Rehabil. 2003 May;84(5):662–7.

4.     Trudel G, Koike Y, Ramachandran N, Doherty G, Dinh L, Lecompte M, et al. Mechanical alterations of rabbit Achilles’ tendon after immobilization correlate with bone mineral density but not with magnetic resonance or ultrasound imaging. Arch Phys Med Rehabil. 2007 Dec;88(12):1720–6.

5.     Thyfault JP, Krogh-Madsen R. Metabolic disruptions induced by reduced ambulatory activity in free-living humans. J. Appl. Physiol. 2011 Oct;111(4):1218–24.

6.     Thyfault JP, Booth FW. Lack of regular physical exercise or too much inactivity. Curr Opin Clin Nutr Metab Care. 2011 Jul;14(4):374–8.

7.     DeFronzo RA, Tripathy D. Skeletal muscle insulin resistance is the primary defect in type 2 diabetes. Diabetes Care. 2009 Nov;32 Suppl 2:S157–63.

8.     Roberts CK, Little JP, Thyfault JP. Modification of insulin sensitivity and glycemic control by activity and exercise. Med Sci Sports Exerc. 2013 Oct;45(10):1868–77.

9.     Dunstan DW, Thorp AA, Healy GN. Prolonged sitting: is it a distinct coronary heart disease risk factor? Curr. Opin. Cardiol. 2011 Sep;26(5):412–9.

Share this