SCIENTIFIC RESEARCH & POSE METHOD Pose Method® of Running has
created a revolution in every runner's world, has arguably become the new
standard of teaching running and has definitely opened new horizons to an ever
growing army of runners of all levels. Some inquiring minds would like to know:
what about the science behind this method?
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Medicine & Science
in Sports & Exercise Cover |
Reduced Eccentric Loading of the Knee with the Pose Running Method
ARENDSE, REGAN E.¹; NOAKES, TIMOTHY D.¹; AZEVEDO, LIANE B.¹; ROMANOV,
NICHOLAS¹; SCHWELLNUS, MARTIN P.¹; FLETCHER, GRAHAM²
¹ MRC/UCT Exercise Science and Sports Medicine Research Unit, Department of
Human Biology, Faculty of Health Sciences, University of Cape Town, SOUTH
AFRICA; and
² University College of the Fraser Valley, British Columbia, CANADA
Medicine & Science in Sports & Exercise: Volume 36(2) February
2004 pp 272-277
Address for correspondence: Dr. Regan E. Arendse, MB.ChB., M.Sc., MRC/UCT Research
Unit for Exercise Science and Sports Medicine, Department of Human Biology,
University of Cape Town, Sports Science Institute of South Africa, P. O. Box
115 Newlands 7725, South Africa; E-mail: rarendse@sports.uct.ac.za.
Submitted for publication May 2003.
Accepted for publication October 2003.
ABSTRACT TOP
ARENDSE, R. E., T. D. NOAKES, L. B. AZEVEDO, N. ROMANOV, M. P. SCHWELLNUS, and
G. FLETCHER. Reduced Eccentric Loading of the Knee with the Pose Running
Method. Med. Sci. Sports Exerc., Vol. 36, No. 2, pp. 272-277, 2004.
Purpose: The aim of this study was to compare the biomechanical changes during
natural heel-toe running with learned midfoot and Pose running.
Methods: Twenty heel-toe
runners were instructed in midfoot running and a novel running style in which
the acromium, greater trochanter, and lateral malleolus are aligned in stance
(Pose running). Clinical gait analysis was performed for each running style and
the biomechanical variables compared.
Results: In comparison with
midfoot and heel-toe running Pose running was characterized by shorter stride
lengths and smaller vertical oscillations of the sacrum and left heel marker.
Compared with midfoot and Pose running heel-toe running was characterized by
greater magnitudes and loading rates of the vertical impact force. In
preparation for initial contact, the knee flexed more in Pose than in heel-toe
and midfoot running. The ankle at initial contact was neutral in Pose compared
with a dorsiflexed and plantarflexed position in heel-toe and midfoot running,
respectively. The knee power absorption and eccentric work were significant
lower (P < 0.05) in Pose than in either heel-toe or midfoot
running. In contrast, there was a higher power absorption and eccentric work at
the ankle in Pose compared with heel-toe and midfoot running.
Conclusions: Pose running was
associated with shorter stride lengths, smaller vertical oscillations of the
sacrum and left heel markers, a neutral ankle joint at initial contact, and
lower eccentric work and power absorption at the knee than occurred in either
midfoot or heel-toe running. The possibility that such gait differences could
be associated with different types and frequencies of running injuries should
be evaluated in controlled clinical trails.
Running style is described as a learned response to a given set of
anthropometric and physiological constraints (4) so that the movement of the
body components minimizes the amount of mechanical work performed (1). Running style may be
described by the overall action, body angle, arm swing, foot placement, rear
leg lift, and length of stride (19).
The biomechanical variables associated with specific running styles change with
running speed (16),
inclination of the running surface (2,20), the use of running shoes
(6), and the use of
treadmills (24).
Biomechanical variables also differ between different running styles for
example between forward and backward running (7).
Backward running is characterized by initial contact with the midfoot, with the
ankle plantarflexed (7).
Compared with forward running, the knee is more flexed in terminal swing,
initial contact, and stance (7).
One of the consequences of this running style is that the peak ground reaction
force is only 25-33% of that measured during forward running, suggesting that
the calf musculature absorbs more of the impact forces during backward running
(15). The peak
patellofemoral compressive force is also reduced with backward running (3.0 ±
0.6 body weight (BW) compared with 5.6 ± 1.3 BW for forward running (8)). These biomechanical characteristics
of backward running may be more beneficial in the treatment of running
injuries, as suggested by anecdotal reports (15). But backward running is an
impractical method for the treatment or prevention of running injuries.
Running in the forward direction with similar flexed knee geometry and midfoot
contact to that of backward running may be hypothesized to offer equivalent
treatment benefits. Midfoot running is, however, not associated with a lower
risk of injury (3). Although
the stance phase knee geometry of midfoot running is not described, it appears
that foot contact is unlikely to be the exclusive determinant of the risk of
injury.
A novel running style with a midfoot strike pattern and a flexed knee in stance
has been developed and is called Pose running. The Pose running lower-limb
geometry instance is achieved by forward lean of the trunk and vertical
alignment of the ipsilateral shoulder, hip, and heel of the supporting limb.
Pose running therefore appears to have a similar lower-limb geometry to
backward running. It is intuitive that Pose running may have a role in the
treatment of running injuries equivalent to backward running.
Accordingly, the aims of this study were to determine whether clinical gait
analysis can distinguish between midfoot and Pose running in natural heel-toe
recreational runners and whether the Pose method produces biomechanical changes
that might be of value in the treatment or prevention of running injuries.
METHODS TOP
Subjects TOP
Twenty (20) male and female
natural heel-toe recreational runners (height: 1.62 ± 0.29 m, mass: 75.9 ± 16.6
kg, age: 33.2 ± 12.7 yr), free of physical deformity or neurological
abnormality, were recruited from running clubs in the Cape Town, South Africa,
region. The mean ± SD 10-km time for the group was 54.3 ± 22.5 min (11.1 km·h-1).
Written informed consent was obtained from the runners before their
participation in the study. Ethical approval for the study was obtained from
the Research and Ethics Committee of the Faculty of Health Sciences, University
of Cape Town.
Test procedure TOP
A repeated measures experimental design (within-subjects) was employed. The
runners were tested in each of three running styles. Initial biomechanical data
were collected for the natural heel-toe running style. The runners were then
instructed in midfoot and Pose running. The data collection procedure was
repeated once the runners were able to run confidently with the two novel
running styles. The running trials were conducted barefoot to aid reliability
of marker placement on successive test sessions and reduce the effect
differences in footwear between runners.
Running style TOP
All runners naturally employed a heel-toe running style in which initial
contact with the supporting surface was made with the heel followed by the mid
and anterior portions of the foot (3). The runners were instructed
in midfoot and Pose running (Fig.
1).
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FIGURE
1- Representative heel-toe, midfoot and pose running styles at initial
contact. |
Midfoot
running instruction consisted of practical demonstration and verbal instruction
to the runners to alter the point of first contact of the foot with the
supporting surface from the heel to the midfoot area. The runners were
instructed to avoid contact with the heel of the foot with the supporting
surface in stance. The runners were allowed to practice midfoot running until
they volunteered that they were confident with the running style and the
investigators were satisfied that there was no contact of the heel with the
supporting surface in stance. None of the runners required more than 15 min to
become confident in the midfoot running style.
In contrast, learning the Pose method required a total instruction of 7.5 h and
comprised 1.5-h sessions daily on five consecutive days. The runners were
encouraged to achieve the following postural changes and actions:
1.
Align
the acromium, the greater trochanter, and lateral malleolus in stance
2.
Lean
forward in the above posture and allow the body to fall forward and thereby
initiate movement
3.
At
initiation of movement, lift the supporting foot by flexing the knee and avoid
pushing away from the supporting surface
4.
At
successive stance phases, contact with the midfoot (ball of foot, not the toes)
and avoid contact of the heel with the supporting surface
5.
Maintain
a flexed knee throughout the gait cycle
Running speed. TOP
The trials in each running style were undertaken at self-selected speeds. The
runners were encouraged to maintain a constant speed for all three styles. A
self-selected running speed was described as a running speed that he or she
could select independently, that felt comfortable, and that would be
representative of the running speed they each followed in an easy training run.
The running speed for each trial was determined from the displacement of the
sacrum marker in the x-axis of the laboratory co-ordinate system during the
processing of the biomechanical data for each trial.
Data collection. TOP
Biomechanical data were collected with a strain gauge force plate (1000 Hz)
(AMTI Inc., Newton, MA) that was mounted flush with the surface of the running
track and a six-camera Vicon-370 Motion Analysis system (120 Hz) (Oxford
Metrics, Oxford, UK). A modified Helen Hayes marker set (22) was used to collect
kinematic data.
Biomechanical data were collected from 10 barefoot running trials in each
style. The 10 trials were scrutinized for errors, and five complete trials of
each runner in each running style were processed. The runners were unaware of
the position of the force plate. A trial was considered successful when the
runner made contact exclusively with the force plate with the right foot, all
retro-reflective markers were tracked for the duration of the right-foot stance
phase on the force plate, and there was no alteration in running style as
observed from the runner with the naked eye and on review of the animation from
the collected gait analysis data.
All biomechanical variables were collected and processed to C3D files with the
Workstation® program by Oxford Metric (Oxford, UK). The C3D files were further
converted to DST files using the Rdata2® program by Motion Lab Systems (Baton
Rouge, LA). Processing of the raw data files was accomplished with the
Bodybuilder® program by Oxford Metrics and the GaitLab® program by Kiboho
Publishers (Cape Town, South Africa) to calculate the temporal-distance
variables, ground reaction forces, knee and ankle joint angles, and power-time
curves. All data were exported as text files for analysis in Excel® (Microsoft
Corporation, Redmond, WA).
Selection of biomechanical variables. TOP
The biomechanical variables selected for this study were based on selected
previous studies (6,14).
Temporal-distance parameters such as stride and step length and vertical
displacement of the sacrum and left heel marker during a gait cycle were
determined. The average horizontal (x-axis) and vertical (z-axis) displacements
of the left heel marker over five running trials were used to determine the
average stride length (m) and vertical foot displacement (m), respectively. The
average vertical displacement of the sacral marker in the z-axis of the global
reference system over five running trials, determined the average vertical body
displacement (m).
The ground reaction forces of the five trials per runner per running style were
averaged and specific variables selected (5,6,12). These included: the
loading rate and magnitude of the vertical impact force peak, the vertical
propulsive force peak, and the horizontal braking and propulsive force peaks.
Due to the inconsistent presence of the vertical impact force peak in the
midfoot style previously reported (3) the loading rate and
magnitude of the vertical impact force at 25 ms of stance were determined. All
ground reaction forces were expressed in multiples of BW.
The knee and ankle joint angles were limited to those about the y-axis through
the knee and ankle joint centers averaged for five running trials per runner
per style and analyzed (22).
Kinematic data included the peak knee flexion angle in swing, the peak knee
extension angle, and the accompanying ankle angle immediately before and at
initial contact, and the peak knee flexion and ankle dorsiflexion angles in
stance phase (°).
The knee and ankle power (W·kg-1) curves during stance phase were
determined with an inverse dynamics method and a three degrees of freedom joint
model in GaitLab® (Kiboho Publishers, Cape Town, South Africa). The peak
negative and positive knee and ankle power values were determined from the data
in an Excel® (Microsoft Corporation) spreadsheet.
Negative (eccentric) and positive (concentric) work (J·kg-1) values
were calculated from the trapezoidal integration of the area below the negative
and positive portions of the power-time curve, respectively.
Statistical analysis. TOP
Statistical tests were performed with a commercial statistical program
(StatSoft, Inc. (2000); STATISTICA for Windows [Computer program manual];
Tulsa, OK). Detailed descriptive statistical analysis was undertaken of the
demographic and training variables. The means of the running speed and
biomechanical variables in each test condition were compared with the repeated
measures ANOVA, the level of significance posted at P < 0.05.
Significant relationships between the means as indicated by significant F-ratios
were explored with the Scheffépost hoc analysis test.
RESULTS TOP
Running speed. TOP
The running speed of the heel-toe running style (2.98 ± 0.42 m·s-1)
was similar to that have midfoot (P = 0.066) and Pose running (P
= 0.089). The running speed for midfoot running (3.06 ± 0.42 m·s-1)
was greater than for Pose running (2.90 ± 0.37 m·s-1) (P =
0.001).
Temporal-distance biomechanical variables. TOP
Pose running was characterized by shorter mean stride and step lengths and
smaller vertical oscillations of the sacrum and left heel marker, compared with
both heel-toe and midfoot running (Table 1).
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TABLE
1. A comparison of the temporal-distance variables between heel-toe, midfoot,
and Pose running (N = 20). |
Ground reaction forces. TOP
Heel-toe running caused greater magnitudes and loading rates of the vertical
impact force at 25 ms of stance and at peak magnitude compared with midfoot and
Pose running (Table 2). The
vertical propulsive force was similar between the heel-toe, midfoot, and Pose
running. The horizontal braking and propulsive forces were less in Pose than
heel-toe and midfoot running.
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TABLE
2. A comparison of the ground reaction force variables between heel-toe,
midfoot, and Pose running (N = 20). |
Knee and ankle joint angles. TOP
The peak knee flexion during the swing phase was the same in all three running
styles (Table 3). The knee
flexed more in preparation for initial foot contact in Pose compared with
heel-toe and midfoot running. The ankle in terminal swing was neutral in Pose
compared with a dorsiflexed and plantarflexed position in heel-toe and midfoot
running, respectively. The knee and ankle geometries in terminal swing of the
respective running styles were maintained at initial foot contact. The peak
knee flexion in stance was greater in the heel-toe and midfoot compared with
Pose running. The peak ankle dorsiflexion in stance was greater in the heel-toe
than midfoot and Pose running.
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TABLE
3. A comparison of the knee and ankle joint angles between heel-toe, midfoot,
and Pose running (N = 20). |
Knee and ankle work and power. TOP
The knee power absorption (Table
4) and eccentric work (Fig.
2) were less in Pose running compared with heel-toe and midfoot running.
The ankle power absorption (Table
4) and eccentric work (Fig.
3) were greater in Pose compared with heel-toe and midfoot running. The
knee power generation and concentric work were less in Pose compared with
either heel-toe or midfoot running (Table 4). There were no
differences in ankle power generation and concentric work between the running
styles.
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TABLE
4. A comparison of the knee and ankle dynamic variables between heel-toe,
midfoot and Pose running (N = 20). |
DISCUSSION TOP
The first relevant finding of this study was that clinical gait analysis was
able to identify the biomechanical differences in midfoot and Pose running in
natural heel-toe runners. Thus, it was found that Pose running is characterized
by shorter stride lengths, lower magnitudes of the vertical impact forces,
greater knee flexion in preparation for and at initial contact, and less
eccentric work at the knee and more eccentric work at the ankle compared with
midfoot and heel-toe running.
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FIGURE
2- A comparison of the knee eccentric work between heel-toe, midfoot and Pose
running (N = 20). *Significantly different from heel-toe and midfoot running. |
Previous attempts to modify running style have measured
the efforts of changing stride length (26), vertical displacement of
the body (18), trunk
inclination, arm swing, and leg mechanics (13). Although each of these
studies has demonstrated changes in individual kinematic variables, these
changes have been inconsistent, showing the resistance of the naturally chosen
running style to change. In contrast, marked changes in running biomechanics
have been measured with changes in running speed (16), gradient of the supporting
surface (20), and the use
of running shoes (6). We now
show that Pose running can produce marked changes in biomechanical variables.
Pose running produced significantly smaller vertical displacement of the body;
the feet are kept close to the supporting surface and the stride and step
lengths are shorter, compared with heel-toe and midfoot running (Table 1).
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FIGURE
3- A comparison of the ankle eccentric work between heel-toe, midfoot and
Pose running (N = 20). *Significantly different from heel-toe and midfoot
running. |
Like midfoot running, but in contrast to heel-toe running,
Pose running reduced the magnitudes and loading rates of the vertical impact
force at 25 ms of stance, as well as the peak value (Table 2). However, Pose and
midfoot running cause different lower-limb geometry during the running stride (Table 3). The horizontal
braking and propulsive forces appeared to be the only components of the ground
reaction force that may distinguish between Pose and midfoot running. This
suggests that the ground reaction forces may not be the most valuable
measurements for evaluating modification of running style but that the other
biomechanical variables need also to be considered.
A change in knee and ankle geometry with the transition from barefoot to shod
running (6), and between
running at different speeds on treadmills (10,11) and overground (16), are well described. The
results of the present study indicate the knee is more flexed in preparation
for and at initial contact in Pose compared with heel-toe and midfoot running (Table 3). This may be a
function of the short stride length characteristic of Pose running (Table 1).
Ankle position also distinguished between the three running styles in terminal
swing and at initial contact, with the ankle dorsiflexed in heel-toe,
plantarflexed in midfoot, and neutral in Pose running. Ankle dorsiflexion in
heel-toe running appears to be associated with the greater magnitude of the
vertical impact force compared with midfoot and Pose running. The difference in
ankle angles between Pose and midfoot running does not appear to have any association
with any other variable measured.
Downhill running has been shown to increase knee eccentric work (2). This study shows that knee
power absorption and eccentric work were significantly reduced with Pose
compared with heel-toe and midfoot running (Fig. 1). In contrast, ankle
power absorption and eccentric work were increased with Pose compared with
heel-toe and midfoot running (Fig.
2). This suggests that there is redistribution of the work activity between
the knee and ankle joints with different running styles. However, the effects
of a different running style on the hip dynamics were not studied.
The hip is the more important source of power for forward propulsion during
running than during walking (16,17).
In contrast, the contribution of the knee and ankle power is minimized as
running speed increases. The reduction in knee power generation and concentric
work with Pose running was not accompanied by a complementary increase in the
ankle power generation and concentric work. Presumably that this was provided
by changes in the hip as a source of power and work for forward propulsion,
which was likely increased in Pose running. This would explain the constant
ankle dynamics in propulsion in all three running styles. To clarify this
relationship, the hip biomechanics should be evaluated in future studies of
running style modification.
The magnitude of the moment arm at the joint of interest is an important
determinant of the magnitude of the mechanical joint work calculated with the
inverse dynamics approach (21).
The low work values at the knee and high work values at the ankle in Pose
running suggest that the magnitude of the moment arm at the knee is least but
is greatest at the ankle. This observation may be due to a combination of the
lower-limb geometry and the position of the torso in stance. The similarity of
knee and ankle work and power between the heel-toe and midfoot running suggests
that the different ankle joint positions do not change the moment arms. Positioning
of the torso over the supporting limb may influence the direction of the ground
reaction force in relation to the lower limb joint centers. The posture of the
whole body throughout the gait cycle should be included in future studies to
fully understand the reasons for the changes in knee and ankle joint power and
work.
In this study, the runners were evaluated in the barefoot condition, to which
they were not habituated. Although standard to all three test conditions, it is
possible that the barefoot condition may prevent the adoption a conventional
heel-toe running style. Runners protect the heel during barefoot running and
reduce distortion of the heel fat pad (6). Subsequently, initial
contact occurs predominantly with the anterior portion of the foot. This may
explain the similar biomechanical variables between heel-toe and midfoot
running in the barefoot condition.
The runners in this study naturally employed a heel-toe running style. The
duration of instruction in midfoot running was no greater than 15 min. In
contrast, Pose running was instructed over a total of 7.5 h. The prolonged time
to teach Pose running was devoted mainly to achieving the desired alignment of
the trunk and supporting limb in stance. It is unlikely that a longer duration
of instruction in midfoot running may have elicited differences in the
biomechanical variables between midfoot and heel-toe running. This opinion is
based on the results of a study in which six male and three female heel-toe
runners readily changed to midfoot contact with verbal instruction by the
investigators with similar instruction time to the present study (25). More importantly, the
biomechanical variables of the natural heel-toe runners with the changed
landing technique were similar to that of natural midfoot runners (25). Accordingly, because the
kinetics and kinematics of Pose running were different from those of midfoot
running, we conclude that the biomechanical characteristics of midfoot running
were faithfully reproduced in this study and were not an artifact of too-short
familiarization period.
An increase in walking and running speed is known to significantly increase the
magnitude of the ground reaction forces (6,23). Although the running
speed in midfoot running was significantly greater than that of Pose, the
ground reaction forces were similar. Kinematic adaptations may produce similar
ground reaction forces with different running conditions (9). In this regard, the
differences in ankle kinematics between midfoot and Pose running may have
minimized any differences in the ground reaction forces between the two,
despite a difference in running speed.
Our results suggest that runners can be taught to run with the novel running
style of Pose running which has biomechanical characteristics different to that
of midfoot and heel-toe running. Pose running is characterized by a shorter
stride length, lower vertical impact forces, a greater knee flexion in
preparation for and at initial contact, less eccentric work at the knee, and
more eccentric work at the ankle compared with midfoot and heel-toe running.
The position of the torso during the gait cycle may explain the reduced knee
eccentric work and increased ankle eccentric work in Pose running compared with
the heel-toe and midfoot running styles. This suggests that the position of the
torso and the center of mass should be included in future studies of running
style modification.
We did not evaluate the clinical or performance consequences of the biomechanical
differences between heel-toe, midfoot, and Pose running. Nevertheless, the
possibility that the reduced knee eccentric work and increased ankle eccentric
work in Pose running may be associated with or have a role in the treatment and
rehabilitation of different types and frequencies of running injuries should be
evaluated in controlled trials.
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