Research Article: Objective measurement of tummy time in infants (0-6 months): A validation study

Date Published: February 27, 2019

Publisher: Public Library of Science

Author(s): Lyndel Hewitt, Rebecca M. Stanley, Dylan Cliff, Anthony D. Okely, Yih-Kuen Jan.


The 2017 Australian and Canadian 24-hour movement guidelines recommend infants receive 30 minutes of tummy time daily. Currently, there are no validated objective measurement tools or devices to assess tummy time. The purpose of this study was to: 1) test the practicality of using devices on infants as an objective measure of tummy time, and 2) test the accuracy of developed algorithms and cut-points for predicting prone posture. Thirty-two healthy infants aged 4 to 25 weeks completed a protocol of 12 positions. Infants were placed in each position for 3 minutes while wearing a MonBaby (chest), GENEActiv (right hip) and two ActiGraphs (right hip and ankle). Direct observation was the criterion measure. The accuracy of the algorithms or cut-points to predict prone on floor, non-prone and prone supported positions were analyzed. Parents also completed a practicality questionnaire. Algorithms and cut-points to classify posture using devices from MonBaby, GENEActiv and ActiGraph (hip and ankle) were 79%, 95%, 90% and 88% accurate at defining tummy time and 100%, 98%, 100% and 96% accurate at defining non-prone positions, respectively. GENEActiv had the smallest mean difference and limits of agreement (-8.4s, limits of agreement [LoA]: -78.2 to 61.3s) for the prone on floor positions and ActiGraph Hip had the smallest mean difference and LoA for the non-prone positions (-0.2s, LoA: -1.2 to 0.9s). The majority of parents agreed all devices were practical and feasible to use with MonBaby being the preferred device. The evaluated algorithms and cut-points for GENEActiv and ActiGraph (hip) are of acceptable accuracy to objectively measure tummy time (time spent prone on floor). Accurate measurement of infant positioning practices will be important in the observation of 24-hour movement guidelines in the early years.

Partial Text

The Australian and Canadian 24-Hour Movement Guidelines for the Early Years (Birth to 5 years) recommend infants (Birth to one year) participate in supervised, interactive floor-based play in safe environments [1, 2]. Tummy time, defined as awake time in the prone position [3] is advantageous for motor development [4]. Thirty minutes of tummy time, spread throughout the day whilst the infant is awake and supervised is encouraged [5]. In addition, a lack of tummy time is one of the most commonly reported risk factors for the development of deformational plagiocephaly [6]. Despite this, evidence remains inconsistent, with some studies reporting a significant positive effect of tummy time on plagiocephaly and others reporting no effect [7–12].

Participant information is shown in Table 1. All participants (N = 32) completed the positioning protocol and had data available from each device to review for each category of position except for MonBaby where there was no data downloaded from three prone on floor and three prone supported categories due to connectivity issues. The complete duration of all 32 videos was 98150 seconds. Infants were coded as: off screen (for example, mother took baby off screen to breast feed, mother in front of infant on video thus blocking the view) for 8% of this time; were coded as invalid position (for example, when the infants were not in one of the 12 defined positions such as picking up off the floor, putting into the car seat/pram, supported standing on the lap of the parent, infant being held whilst parent is moving into and out of the beanbag) for 18% of this time; and coded as invalid device (for example, if the device required re-positioning on the infant) for <1% of the time. The total time able to be classified as one of the 12 positions (excluding when the infant was coded as off screen, invalid position or invalid device) was 72050 seconds (11749 seconds in prone positions; 49123 seconds in non prone positions and 11178 seconds in prone supported positions). This study investigated the accuracy of the manufacturer’s (MonDevices Inc, ActiGraph LLC and Activinsights Ltd) algorithm or cut-points for predicting posture. The GENEActiv device was the most accurate to determine prone on floor positions, followed by ActiGraph Hip. All devices were able to accurately determine non-prone positions but not prone supported positions.   Source:


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