Citation: Choi, J.; Knarr, B.A.; Gwon,
Y.; Youn, J.-H. Prediction of Stability
during Walking at Simulated Ship’s
Rolling Motion Using Accelerometers.
Sensors 2022, 22, 5416. https://
doi.org/10.3390/s22145416
Academic Editor: Stefano Rossi
Received: 6 June 2022
Accepted: 18 July 2022
Published: 20 July 2022
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Article
Prediction of Stability during Walking at Simulated Ship’s
Rolling Motion Using Accelerometers
Jungyeon Choi
1
, Brian A. Knarr
2
, Yeongjin Gwon
3
and Jong-Hoon Youn
1,
*
1
College of Information Science and Technology, University of Nebraska at Omaha, Omaha, NE 68182, USA;
jungyeonchoi@unomaha.edu
2
Department of Biomechanics, University of Nebraska at Omaha, Omaha, NE 68182, USA;
bknarr@unomaha.edu
3
Department of Biostatistics, University of Nebraska Medical Center, Omaha, NE 68198, USA;
yeongjin.gwon@unmc.edu
* Correspondence: jyoun@unomaha.edu
Abstract:
Due to a ship’s extreme motion, there is a risk of injuries and accidents as people may
become unbalanced and be injured or fall from the ship. Thus, individuals must adjust their move-
ments when walking in an unstable environment to avoid falling or losing balance. A person’s
ability to control their center of mass (COM) during lateral motion is critical to maintaining balance
when walking. Dynamic balancing is also crucial to maintain stability while walking. The margin
of stability (MOS) is used to define this dynamic balancing. This study aimed to develop a model
for predicting balance control and stability in walking on ships by estimating the peak COM excur-
sion and MOS variability using accelerometers. We recruited 30 healthy individuals for this study.
During the experiment, participants walked for two minutes at self-selected speeds, and we used
a computer-assisted rehabilitation environment (CAREN) system to simulate the roll motion. The
proposed prediction models in this study successfully predicted the peak COM excursion and MOS
variability. This study may be used to protect and save seafarers or passengers by assessing the risk
of balance loss.
Keywords: gait stability; ship rolling; center of mass; margin of stability; accelerometer; CAREN
1. Introduction
Recent advances in wearable sensors have enabled gait analysis outside the laboratory.
Continuous gait monitoring during free-living activities presents a promising approach to
the gait study, investigating the risk of falling in real-world settings. Individual walking
characteristics differ from one individual to another, and walking strategies can change
depending on the walking environment [
1
]. Walking on a moving ship is very different
from walking on land. A ship’s movement directly affects a person’s ability to walk [
1
,
2
].
The extreme motion of the ship may result in accidents, such as being injured or falling
overboard, through the ship causing people to become unbalanced. Such ship’s motion
may compromise the safety of sailors and passengers. It was found that 22 people fall off
cruise ships each year and only about 20% of them survive [
3
]. Moreover, according to
the National Institute for Occupational Safety and Health (NIOSH), almost one-quarter of
all Alaskan fisher deaths between 1990 and 1999 resulted from man overboard (MOB) [
4
].
Particularly, MOB accidents on a small fishing boat with a few crew members on board are
riskier since there is no proper method to alert the MOB condition [
5
]. Thus, to reduce the
likelihood of falling off-board accidents, it is of the utmost importance to predict the risk of
falls in the moving environment of a ship.
The human body is less lateral stable when walking [
6
–
10
]. The lateral motion control
of the center of mass (COM) is essential for maintaining balance during walking [
11
]. In
this regard, the deviation of the gait pattern in the lateral direction has been proposed as
Sensors 2022, 22, 5416. https://doi.org/10.3390/s22145416 https://www.mdpi.com/journal/sensors
