Characterization of Detailed Sedentary Postures Using a Tri-Monitor ActivPAL Configuration in Free-Living Conditions

• Published in: Sensors (Basel, Switzerland) Vol. 23; no. 2; p. 587
• Main Authors: O'Brien, Myles W, Daley, W Seth, Schwartz, Beverly D, Shivgulam, Madeline E, Wu, Yanlin, Kimmerly, Derek S, Frayne, Ryan J
• Format: Journal Article
• Language: English
• Published: Switzerland MDPI AG 04.01.2023; MDPI
• Subjects: Accelerometers; Accelerometry; Adult; bent-knee sitting; Blood pressure; body positions; Configurations; Humans; inclinometry; Knee; Laboratories; lying time; Physiology; Posture; Sedentary behavior; Self report; Sitting Position; sitting postures; Sleep; Social Conditions; Software; Thigh; Torso; Canada; United States > US; lying time; sitting postures; bent-knee sitting; body positions; inclinometry
• ISSN: 1424-8220; 1424-8220
• DOI: 10.3390/s23020587

Objective monitors such as the activPAL characterize time when the thigh is horizontal as sedentary time. However, there are physiological differences between lying, bent-legged sitting, and straight-legged sitting. We introduce a three-monitor configuration to assess detailed sedentary postures and demonstrate its use in characterizing such positions in free-living conditions. We explored time spent in each sedentary posture between prolonged (>1 h) versus non-prolonged (<1 h) sedentary bouts. In total, 35 healthy adults (16♀, 24 ± 3 years; 24 h/day for 6.8 ± 1.0 days) wore an activPAL accelerometer on their thigh, torso, and shin. Hip and knee joint flexion angle estimates were determined during sedentary bouts using the dot-product method between the torso−thigh and thigh−shin, respectively. Compared to lying (69 ± 60 min/day) or straight-legged sitting (113 ± 100 min/day), most time was spent in bent-legged sitting (439 ± 101 min/day, p < 0.001). Most of the bent-legged sitting time was accumulated in non-prolonged bouts (328 ± 83 vs. 112 ± 63 min/day, p < 0.001). In contrast, similar time was spent in straight-legged sitting and lying between prolonged/non-prolonged bouts (both, p > 0.26). We document that a considerable amount of waking time is accumulated in lying or straight-legged sitting. This methodological approach equips researchers with a means of characterizing detailed sedentary postures in uncontrolled conditions and may help answer novel research questions on sedentariness.