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Gait initiation in upslope walking
Gerda Strutzenberger, Maria Flecker,
Institute of Sports and Sport Science, University of Kassel, Kassel, Germany
Department of Sport Exercise and Science, Paris Lodron University of Salzburg, Salzburg,
Studies examining biomechanical aspects of sloped walking at different inclination angles have only paid
little attention to the initial walkway’s length and its influence on gait parameters . Methodological
either treadmills [2, 3] or custom-built ramps [1,4-8] were used to replicate the gait on slopes. While ramps
allow for a genuine walking pattern and force plates can be included, their restricted walking space requires
considerations on where to allow participants to start and stop walking.
Gait initiation was examined in level walking by using different biomechanical parameters. Mann, Hagy,
White, and Liddell (1979) suggested that three steps were necessary to reach steady-state gait based on
changes in joint angles, muscle activity and force plate data. Breniere and Do (1986) found that steady-state
gait velocity was reached within the first step of gait initiation. On the basis of a mechanical energy analysis,
Miller and Verstraete (1996) supposed to take three full steps before recording data. Despite disagreement
on the number of steps necessary to reach speed steady-state in level walking, it is recommended for gait
analysis to allow participants at least three steps before and after data collection .
In fact, the issue of the number of steps necessary to reach steady state in sloped walking has not been
addressed. In existing studies, the number of initial steps before the foot under investigation steps on the
force plate differs between studies or is not clearly reported [7,13]. For instance, Kawamura et al. (1991)
prepared a 2 m level walking platform in front of the slope and at the top of the slope in order to exclude
acceleration at the beginning and deceleration at the end of walking. Lay et al. (2006) adjusted the starting
position so the participant’s third step struck the force plates. Alexander and Schwameder (2016) let their
participants take up to four steps before and after the measurement.
Due to altered requirements on the kinematics and kinetics during upslope walking in order to raise the
body, it is hypothesized that reaching steady-state walking is the more difficult the steeper the incline is
compared to level walking. Thus, we suggested that the number of steps necessary to reach steady-state
walking increases as ramp angle increases during upslope walking.
Therefore, the main purpose of this study is to determine when speed steady-state in slope walking is
reached measured by the relative chance in horizontal velocity and the resultant center of mass (CoM)
velocity. Based on the results, recommendation for the set-up of further investigations on sloped walking
regarding the initial walkway should be defined.
Fourteen healthy participants (24.5 ± 2.0 yrs) walked on a ramp (6m x1.4m) at level (0°) and three uphill
inclinations (+6°, +12°, +18°). Kinematic and kinetic data were collected using a motion capture system
(Vicon, Oxford Metrics Ltd. UK, 250Hz) and two force plates imbedded in the ramp (AMTI, Watertown, USA,
1000 Hz). The starting position was adjusted to contact the force plates with a) the first (left) and second
step (right) and b) the third (left) and fourth (right) step of gait initiation. The participants were asked to
complete three trials in each step condition of walking from the starting point until the end of the ramp
with self-selected speed. The relative change of horizontal velocity (∆vel
) and the resultant CoM velocity
) for each stance phase were determined. Additionally, temporo-spatial, kinematic and kinetic
parameters of the lower limb were calculated. Statistics were calculated using a Friedman ANOVA (factor:
steps) with pairwise comparison using Wilcoxon tests (p=0.05, Bonferroni corrected: p=0.016)
decreased significantly from step 1 to step 2 in all inclinations, and remained afterwards on average
between ± 0.05 m/s of relative horizontal velocity change (Figure 1). Adding the vertical component leads to
a significant increase in vel
between step 1 to 2, between step 2 and 3 and a significant decrease of
velocity between step 3 and 4. Step frequency showed significant increases between step 1 to step 2 and
step 2 to step 3 in all inclinations (Figure 2).
Figure 1. relative change of horizontal velocity for
each step in all inclinations
Figure 2. step frequency for each step in all
Uphill gait requires raising the knee higher than in level walking in order to allow for a safe forward swing of
the foot to be placed in the higher position. Furthermore, the CoM has to overcome the gravity and be
further raised upwards. As with inclined steepness a higher demand is placed on the coordination of the
neuromuscular system, this study aimed to investigate if the same pattern for reaching speed steady-state
occurs in uphill walking compared to level walking, which is important for the analysis of uphill gait. With
respect to the relative change of horizontal velocity, speed steady-state in upslope walking was reached
already after the second step in all inclinations. However, maximum velocity was reached in all inclinations
with the 3
step when the resultant velocity was analyzed. This might be due to the vertical component of
the uphill movement. The increase in velocity was mainly generated due to the increase in step frequency,
which showed significant increases between the 1
step as well as between the 2
while step length did not show any relevant changes within all four steps. Critically reviewing the data
collection set-up, it has to be noted that a functional gait asymmetry is discussed in able-bodied gait .
Hence, we cannot fully state that the differences between the steps are only due to the change in gait
velocity from standing to steady-state walking. Therefore, significant differences between the steps could
be partly a result of functional gait asymmetry. In conclusion, it seems that steady state was reached with
step and thus, this step seems to be appropriate to be used for uphill gait analysis in all inclinations.
The following decrease of vel
between -0.7 and -2.4% indicated a slight deceleration of the motion.
However, it yet needs to be investigated if this is in the range of limb asymmetry or might be related to the
specific situation of the ramp.
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