Inactivity Physiology: Be Active - and Also Less Inactive

Tuesday, May 24, 2016 - 08:15
For optimal health outcomes, sit as little as possible

Most of us are familiar with the benefits of physical activity.  A reduction in the risk of cardiovascular disease (CVD), diabetes, low back pain, osteoarthritis, anxiety and depression, and even some forms of cancer can be counted among the myriad advantages of leading an active life.  However, what is lesser known is the flip side of this – the damaging effect of an inactive lifestyle, which includes sitting all day at work, and lying on the couch in the evening.  The relatively new area of research is aptly called inactivity physiology, and recent findings shed an uncomfortable light on the manner in which more people in the Western world live. The average person now spends 9.3 hours a day sitting.  People who sit for six or more hours per day are 40 percent more likely to die within 15 years compared to someone who sits less than three hours a day – even if they exercise.  That is to say, that even if you are getting the American College of Sports Medicine (ACSM) recommended amount of physical activity - 30 minutes of cardiovascular exercise per day - you still fall into this category.  The excessive sitting behaviour effectively cancels out the benefit of the daily exercise.  Obese people sit 2.5 hours more each day then people of normal weight.  Among the 7278 men and 9735 women enrolled in the Canadian Physical Activity Longitudinal Study, there was a strong association between sitting and mortality risk from CVD and all other causes, after adjusting the data for potential confounding variables (eg, age, sex, smoking status, alcohol consumption, leisure time, and physical activity).  The highest mortality subpopulation group is obese men and women who spend most of their waking time sitting.

Studies of sedentary behaviour suggest that sitting for extended periods of time increase a person’s chances of developing a wide range of illnesses and diseases, including several types of cancer, CVD, obesity, and Type II diabetes.  In a recently published study, Dr. Christine Friedenreich, a senior epidemiologist at the Alberta Health Services, found that high levels of physical activity reduced the risk of breast and colon cancers by up to 30 percent, reduced the risk of prostate cancer about 10 to 20 percent, and reduced the risk of endometrial cancer between 30 and 35 percent.  However, the most disquieting result of her study was that people who jog for half an hour in the morning and then sit at a desk all day may be no better off then those who don’t go running. Why might this be?  There are few definitive answers as this is an emerging area of research, but current findings points to several possible factors:

  1. In animal studies with rats, it has been found that when they are not allowed to stand there is a dramatic drop in lipoprotein lipase, the enzyme in the leg muscles that captures fat out of the blood to be used by the body as fuel.  Thus, with consistent sitting, blood triglyceride levels start to soar which increases the risk of CVD.  It has been hypothesized that this same process occurs in humans.
  2. Levels of enzymes that help break down fat drop by 90 percent as soon as a person sits down.
  3. A clinically relevant decrease in HDL (“good”) cholesterol is observed with regular, prolonged periods of sitting.

Exercise Specialist Recommendations

  • Stand up and walk around your office every 30 minutes.
  • Set a timer on your computer or phone to remind you to get up regularly.
  • Stand up and get some water.
  • Walk to your colleagues' offices instead of emailing them.
  • Walk to the farthest bathroom in your workplace (if more than one is available).
  • Always stand and walk around the room when on the phone.
  • Take a 5-minutes walk break with every coffee break.
  • At night when watching tv, take breaks during commercials to do standing stretches or some easy leg exercises.
  • Stand up while watching tv to do single leg balances.
  • Capitalize on Non-Exercise Activity Thermogenesis (NEAT) – in a nutshell, it has been found that people who tend to fidget and move around spontaneously throughout the day have lower levels of obesity, because they burn more calories than their sedentary counterparts

The bottom line is that it is necessary to incorporate as much movement into our daily lives as possible, in addition to scheduled exercise sessions.