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28th Congress of the European Society of Biomechanics, July 9-12, 2023, Maastricht, the Netherlands
IN WATER AND ON LAND FORWARD AND BACKWARD
SPATIOTEMPORAL GAIT CHARACTERISTICS
Cecilia Monoli (1,2), Manuela Galli (2), Jeffrey A. Tuhtan (1)
1. Tallinn University of Technology, Department of Computer System, Tallinn 12616, Estonia
2. Politecnico di Milano, Department of Electronics, Information and Bioengineering, Milano 20133, Italy
Introduction
Forward and backward walking is a common exercise
for rehabilitation due to the major role that locomotion
plays in an individual’s quality of life [1]. Aquatic
exercises are widely used alongside traditional land-
based therapy because of the beneficial physical
characteristics of water on various body systems [2].
Walking underwater, for instance, impacts the
muscular-skeletal system, reducing fatigue and pain and
improving the physical recovery rate as well as the
joints’ range of motion [3]. A recent systematic review
[4] pointed out that the use of wearable inertial
measurement unit sensors (IMUs) in water for human
biomechanical motion analysis is still limited. In
particular, no previous studies investigated the
kinematic differences between forward and backward
walking in water using wearables. Therefore, the aim of
this investigation is to explore gait analysis via
customized IMUs estimating and comparing forward
and backward spatiotemporal gait parameters and gait
phases, in and outside water.
Methods
Five healthy female volunteers (24.5 ± 0.6 years old),
with no previous history of injuries at the lower limbs,
were included. They were asked to walk ten times at
their preferred self-selected regular pace forward and
backward in a straight line, inside and outside water
(swimming pool: 1.20m depth, 33°C, Enjoy Sport
center, Cernusco sul Naviglio, Milano, Italy). Two
IMUs, developed by Tallinn University of Technology
(Tallinn, Estonia) were placed on the instep of both feet
using self-adhesive tape. The loggers are small
(30x12x9mm) and lightweight (about 7g), causing as
little discomfort as possible and not interfering with the
subjects' movements. The sensors include an absolute
orientation sensor (BMX160, Bosch), sampling at
100Hz, a microcontroller and onboard memory. The
devices have been specifically developed for underwater
applications and therefore do not require any casing or
specific precautions to be employed safely. The first two
complete gait cycles of the left and right legs were
investigated. Matlab (2022b) was used to define the gait
events from the accelerometer data and to estimate the
spatiotemporal gait parameters. The stride time is
identified as the period between two subsequent
homolateral foot strikes (respectively heel or toe strike
during forward or backward gait) while the stance and
swing components are identified respectively as the
portions of the gait cycle in which the foot is in contact
with the ground and in which it is undergoing motion.
Results
The results of stride time expressed in seconds and
stance and swing components expressed as a percentage
of the gait cycle are resumed in Figure 1, for both
forward and backward gait on land (brown) and in water
(blue). Right and left gait parameters are displayed
together after checking the two populations with the
two-sample Kolmogorov-Smirnov test to assess
whether they come from the same distribution.
Discussion
The stride time underwater is more than doubled for
both forward and backward gait, showing a much higher
variability and uncertainty. In water, the stride time was
observed to considerably decrease between forward and
backward gait, with a difference of 0.5s (about 17% of
the stride time during forward walking). These results
might be related to the higher density of water with
respect to air, which creates a safe environment that
reduces the fear of falling during backward gait and
simultaneously increases the difficulty of moving
consistently, increasing the gait variability. Despite the
differences in stride time, the partitioning of the gait
cycle in stance (about 60%) and swing (about 40%)
phases remains invariant for land and underwater
environments and for forward and backward gait.
Figure 1: Gait parameters (stride time, stance and
swing components of the gait cycle) of forward and
backward gait on land (brown)and in water (blue).
References
1. Cadenas-Sanchez et al, J Hum Kinet., 49:15-24, 2015.
2. Marinho-Buzelli et al, Clin. Rehabil., 29: 741–751, 2015.
3. Mooventhan et al, N. Amer. J. Med. Sci., 6(5): 199–209,
2014.
4. Monoli et al, Clin. Rehabil., 0(0), 2022.