Muscle activity and inactivity periods during normal daily life

PLoS One. 2013;8(1):e52228. doi: 10.1371/journal.pone.0052228. Epub 2013 Jan 18.

Abstract

Recent findings suggest that not only the lack of physical activity, but also prolonged times of sedentary behaviour where major locomotor muscles are inactive, significantly increase the risk of chronic diseases. The purpose of this study was to provide details of quadriceps and hamstring muscle inactivity and activity during normal daily life of ordinary people. Eighty-four volunteers (44 females, 40 males, 44.1±17.3 years, 172.3±6.1 cm, 70.1±10.2 kg) were measured during normal daily life using shorts measuring muscle electromyographic (EMG) activity (recording time 11.3±2.0 hours). EMG was normalized to isometric MVC (EMG(MVC)) during knee flexion and extension, and inactivity threshold of each muscle group was defined as 90% of EMG activity during standing (2.5±1.7% of EMG(MVC)). During normal daily life the average EMG amplitude was 4.0±2.6% and average activity burst amplitude was 5.8±3.4% of EMG(MVC) (mean duration of 1.4±1.4 s) which is below the EMG level required for walking (5 km/h corresponding to EMG level of about 10% of EMG(MVC)). Using the proposed individual inactivity threshold, thigh muscles were inactive 67.5±11.9% of the total recording time and the longest inactivity periods lasted for 13.9±7.3 min (2.5-38.3 min). Women had more activity bursts and spent more time at intensities above 40% EMG(MVC) than men (p<0.05). In conclusion, during normal daily life the locomotor muscles are inactive about 7.5 hours, and only a small fraction of muscle's maximal voluntary activation capacity is used averaging only 4% of the maximal recruitment of the thigh muscles. Some daily non-exercise activities such as stair climbing produce much higher muscle activity levels than brisk walking, and replacing sitting by standing can considerably increase cumulative daily muscle activity.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Activities of Daily Living*
  • Adult
  • Aged
  • Electromyography
  • Female
  • Humans
  • Male
  • Middle Aged
  • Muscle, Skeletal / physiology*
  • Quadriceps Muscle / physiology
  • Time Factors
  • Young Adult

Grant support

This study was funded by Academy of Finland (#128643/Finni), Ministry of Education (42/627/2010/Finni) and Urheiluopistosäätiö (Tikkanen). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.