Biomechanics of Ascending an Incline
Jon Singer and D. Gordon E. Robertson
School of Human Kinetics, University of Ottawa, Ontario, CANADA, K1N 6N5
500.
Results
Figure 1 shows a typical subject’s support, hip, knee and ankle
moments during the step on level ground immediately before the
ramp and the same leg’s moments while on the ramp (second
step). The first support moment was approximately the same as
level walking. The support moment on the ramp, however, was
slightly lower. All subjects showed this slight decrease in the
amplitude of the support moment, as well as having a smaller
second peak for both steps. This may be due to the incline of the
ramp and therefore the reduced need to swing and decelerate the
lower extremity before landing.
Biomechanics Laboratory
H1
H3
H1
H3
0.
H2
H2
- 250.
Knee
powers
250.
K2
0.
K4
K3
- 250.
K1
K3
500.
A2
A2
Ankle
powers
250.
0.
A1
- 250.
3
FS
- 500.
Support
moment
2
Trial: RUAP03
0.0
TO
0.2
0.4
0.6
0 .8
FS
1.0
1.2
TO
1.4
1.6
1.8
2.0
Time (seconds)
1
Net moments of force (N.m/kg)
Methods
Participants were required to walk across a laboratory
walkway and ascend a 10-degree ramp at a self-selected
walking pace. Two force platforms were used; one was
positioned on the level walkway, just prior to the ramp; the
second was imbedded in the ramp itself. Force platforms
were positioned such that the right leg would make contact
with the level force platform, then strike the force platform on
the ramp with the same leg on the subsequent step.
Force platform data were rotated to compensate for the
10-degree incline and combined with the kinematic data
using inverse dynamics to obtain the net moments of the
ankle, knee and hip (Winter & Robertson, 1978). Then, the
three moments were normalized to body mass and summed
to obtain the support moment.
250.
Hip
powers
A1
Figure 2: Hip, knee and ankle moment powers during
walking up a ramp.
0
Purpose
To determine the differences between the work and power
requirements of the net moments of the lower extremity
during ramp ascent, as compared to level walking.
Trial: RUAP03
Power (watts)
Introduction
Ramps are a common means of ambulation and are often
used in the transportation of materials (Robertson &
Ellwood, 1995) from one level surface to another. Despite
this fact, little research has been performed in this domain.
An assessment of this activity, in comparison with
normative data from level walking, is possible based on
data presented by Winter (1991). A useful tool in
comparing gait on an incline, as compared to that on a
level surface, is the support moment. This concept was
defined by Winter (1991) as the algebraic sum of the three
joint moments of the lower limb, with the extensor moment
being positive. During stance phase, individuals produce a
characteristic bimodal impulse that represents the total
extensor force of the lower limb needed to prevent collapse
under the effect of the body weight.
Hip
extensor
-1
Results
The knee powers for the step on the ramp (Figure 2) have
the same pattern to those reported by Winter (1991) for
level walking. The step before the ramp, however, was
modified by work done by the extensor moment.
Hip powers during level walking were usually more
variable between individuals than were the knee and ankle
moments. This held true for ramp ascent as well. Phases
H1, H2 and H3 were usually present but were typically of
lower amplitude than the step before the ramp.
1
0
-1
Knee
extensor
1
0
-1
Ankle
extensor
1
0
-1
TO
FS
-2
0.0
0.2
0.4
0.6
0.8
FS
1.0
1.2
TO
1.4
1.6
1.8
2.0
Time (seconds)
Figure 1: Normalized support, hip, knee and ankle moments
before and during walking up a ramp.
Results
Figure 2 shows the powers produced by the same subject. The
ankle powers during the step on the ramp were essentially the
same as level walking i.e., an initial burst of dorsiflexor activity
followed by plantar flexor negative work, then positive work.
Summary
The lower extremity moments during ramp ascent were
essentially the same as those that occur during level
walking. The main difference was the reduction of the
support moment, mainly due to reduced hip moments.
References
Robertson DGE, Ellwood DM (1995) Proceedings of ISB 15:774-775.
Winter DA, Robertson, DGE (1978) Biological Cybernetics, 29:137-142.
Winter DA (1991) Biomechanics and Motor Control of Human Gait.
2ndEd., Waterloo: Waterloo Biomechanics.