title: Lack of regular physical exercise or too much inactivity.
abstract: OBJECTIVE
  To discuss the current data that acute periods of physical inactivity are harmful to health.
  
  
  RESULTS
  Bed rest prescribed for recovery from clinical conditions causes changes in thousands of mRNAs in leg muscles within days. Humans genetically more susceptible to metabolic disorders (low birth weight babies and type 2 diabetic offspring) are as, or more, susceptible to further metabolic dysfunction by the environmental perturbation of bed rest, as compared with healthy controls without these risk factors. High daily accumulations of sitting are not only associated with enhanced metabolic risk, but current findings report that increased sitting time leads to a reduction in insulin sensitivity. Reductions in walking or in ambulatory activity (lower step numbers taken by healthy humans) reduce insulin sensitivity and insulin signaling through Akt in skeletal muscle.
  
  
  CONCLUSIONS
  New findings using human models of physical inactivity (bed rest, increased sitting time, and reduced daily ambulatory activity), extend pre-existing research showing that transitioning to physical inactivity rapidly reduced metabolic health. Modern technological advances that remove standing, walking, and major limb movement initiate metabolic dysfunctions that likely play a fundamental role in the development of obesity and type 2 diabetes.
authors.affiliation: Harry S Truman Memorial VA Hospital, Department of Nutrition and Exercise Physiology, Dalton Cardiovascular Research Center, University of Missouri, Columbia, Missouri 65201, USA. thyfaultj@missouri.edu
authors.forename: John P
authors.initials: JP
authors.lastname: Thyfault
authors.forename: Frank W
authors.initials: FW
authors.lastname: Booth
mesh_terms: D000222:Adaptation, Physiological; D001510:Bed Rest / Q000009:adverse effects*; D003924:Diabetes Mellitus, Type 2; D015536:Down-Regulation; D015444:Exercise; D015438:Health Behavior; D006801:Humans; D007328:Insulin / Q000097:blood; D007333:Insulin Resistance; D009043:Motor Activity / Q000502:physiology*; D009765:Obesity; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D012307:Risk Factors
chemical_list: D007328:Insulin; D012333:RNA, Messenger