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Impact of reduced physical activity on human health: comparison of younger and older adults


ARIS Code: J5-50178

Project duration: 1. 10. 2023–30. 9. 2026

Project leaderBoštjan Šimunić, PhD

Participating institute at ZRS KoperInstitute for Kinesiology Research

Physical inactivity (PI) is an independent risk factor for overall health. As it is very widespread (> 10 hours daily), it is a 2nd mortality risk factor and since 2019 WHO guidelines restrict sedentary behaviour. In addition, PI can be considered pandemic as it decreases exercise tolerance and dramatically increases disease risk. Although PI affects overall health, the main deterioration occurs at the level of loss of muscle size and function, impaired central and peripheral motor control, and impaired oxidative metabolism and insulin resistance. Most previous studies have focused only on young, and few on old.

There is growing interest in experimental studies of physical activity restriction to investigate the pathophysiological mechanisms by which PI affects human health. Most previous studies examining these aspects were conducted in laboratory settings using extreme models of unloading (e.g., bed rest). More recently, an additional systemic model of reduced PI has been proposed, termed step reduction (SR). SR consists of suddenly reducing participants’ habitual daily steps to a lower maximum step count, ranging from ∼750 to ∼4500 steps/day. Compared with bed rest, SR is considered a “milder” form of PI because participants continue to be exposed to exercise stimuli. However, this model appears to be much closer to real-world conditions, more ecologically valid, and capable of mimicking the detrimental effects of a sedentary lifestyle. In addition, it should be noted that prolonged bed rest is less common than periods of lower physical activity and that a low number of daily steps is strongly associated with an increased risk of mortality.