3. Introduction
For this project, I have decided to work and analyze the propulsion cycle of a wheelchair user.
Manual WCP is a cyclic task that requires repetitive generation of propulsive forces on the pushrim of
the WC. Generation of these reaction forces (RFs) applied at the pushrim involves coordinated
activation of muscles responsible for simultaneously maintaining shoulder joint stability and controlling
shoulder rotation. (Russell et al. 2015) Manual wheelchair users are at great risk for the development of
upper extremity injury and pain. Any loss of upper limb function due to pain adversely impacts the
independence and mobility of manual wheelchair users. (Sosnoff et al. 2015) While the exact
relationship between the physical demands of wheelchair use and the development of shoulder
pathology is not yet fully understood, ergonomics studies consistently suggest that there is a link
between highly repetitive tasks and the occurrence of upper extremity pain and injury. (Santos et al.
2016)
As a physical therapist it is important to know and understand the biomechanical reason behind the
often seen injuries or complaints amongst wheelchair users, and the effect that proper training and
wheelchair seat position has on patients. This movement analysis is very complex due to the number of
joints involved, and most importantly, when looking into the shoulder, the number of bones and muscles
involved. It is frequently speculated that propulsion biomechanics contributes to the pathogenesis of
shoulder pathology. This speculation is based on simple Newtonian mechanics that forces applied to the
wheelchair hand rim resulted in reactive forces acting on the shoulder that may over time lead to
musculoskeletal damage. (Moon et al. 2013)
The wheelchair propulsion cycle can be divided in two major phases:
1. Push phase
2. Recovery phase
(Moon Y et al. 2013)
The Push Phase starts when the hand makes contact with the push rim and then applies a propulsive
force. The push phase makes up approximately 25% of the total cycle in a standard wheelchair. In the
2
4. early part of the push phase, the hand is accelerating to the speed of the rim. A propulsive force is then
applied through the hand rim creating a torque about the wheel axle.
The Recovery Phase starts when the hands disengage from the push rim and return to initiate the next
push phase. The recovery phase is about 65-75% of the propulsion cycle.
During the recovery phase, the hand is much less constrained than during the push phase and can
follow a number of different paths. The resulting hand patterns (i.e., full- cycle hand paths) are frequently
classified into four distinct hand pattern types based on the shape of their projection onto the plane of
the handrim (Slowik et al. 2016):
(Slowik et al. 2016)
Arcing (AR): The third metacarpophalangeal (MP) follows an arc along the path of the hand rim during
the recovery phase.
● Single looping over propulsion (SL): the hands rise above the hand rim during recovery phase.
● Double looping over propulsion (DL): the hands rise above the hand rim, then cross over and
drop below the hand rim during the recovery phase.
● Semicircular (SC): the hands fall below the hand rim during recovery phase.
3
5. Whole Body Analysis
GCM Calculation
In order to calculate the GCM a decision must be made in terms of what the analyzed body will be,
whether I wanted to analyze the person individually, or the person and the chair as one object.
I decided to consider the person and the wheelchair as one, because of the fact that most wheelchair
users are bound to them, and therefore consider the wheelchair part of their body; as well as the
physical impact this has on the person and the body.
According to Karman et al. the center of gravity of an unoccupied
wheelchair lies in the upper frontal quadrant of the wheel, as seen in
the picture. In order to calculate the GCM of the occupied
wheelchair, I made use of the construction method (Loozen. 2014)
and translated the GCM of the individual and the GCM of the
unoccupied wheelchair.
To find the GCM, I first had to calculate the PCM of the leg, the
torso, and the arm, as well as the wheelchair. For these calculations,
some measurements were necessary, including the weight of the
individual: 60KG; and the weight of the wheelchair: 20KG.
Phase 1
The picture on the left shows the calculated
PCM’s of the leg, torso, and arm; as well as the
GCM of the wheelchair alone (red star), and the
individual (green star). The yellow star represents
the combined GMC, and therefore what will be
used as the GCM for this analysis. The GCM lies
more cranially and dorsally than that of a
motionless wheelchair user due to the position of
the arms. As seen in the picture on the right, the
GCM lies slightly more ventral and caudal
because the arms are moving in a
posterior-anterior direction, shifting a portion of
the weight of the body forward.
Phase 2
The GCM lies more ventrally than the previous
phase due to the forward shift of weight because
of the movement of the arms.
4
6. Phase 3
The GCM lies in an almost unchanged position
from the previous phase due to the fact that the
weight of the body is the same, only the hands
are no longer making contact with the handrim of
the wheels.
Phase 4
The GCM lies slightly more dorsally than the last
phase due to the changed position on the arms,
and the backward movement of them.
Phase 5
During this phase the GCM has shifted more
dorsally again, due to the backward position of the
arms.
5
7. Phase 6
At this point the GCM has reached its initial
position, which is slightly more cranial than the
last frame.
** The length of the line of gravity is estimated and tries to depict -800N that are acting on the GCM. This line is of equal
length in each picture.
GCM Displacement
To find the translation of the GCM throughout the movement, I overlapped the images where the GCM
was shown, and tracked the movement.
The photo above shows the GCM displacement in space throughout the propulsion cycle of a wheelchair
user. Some images are very blurry because of the blending effect; however, the GCM of each phase is
still visible. The displacement shows a forward translation, and minimal displacements cranially and
caudally, this is because of the (very slight) forward bending of the torso as well as the movement in the
arms.
The total forward displacement of the GCM in meters was: 1.37m / 1 sec (real time). Therefore the
velocity of the displacement is 1.37m/1sec.
6
8. Because of the constant speed at which the movement is happening, I can assume that the acceleration
is 0.
Joint Angles – Absolute angles
*Angles of hip, knee and ankle will be neglected.
Phase Shoulder Elbow Wrist
295° - 294°
Extension
*Change in angle
could be negligible
239° - 256°
Flexion
193° - 192°
Ulnar dev
294° - 350°
Flexion
256° -215°
Extension
192° - 157°
Ulnar dev
350° - 352°
Flexion
215°- 201°
Extension
157°- 163°
Radial dev
352° - 341°
Extension
201°-207°
Flexion
163° - 168°
Radial dev
7
9. 341° - 314°
Extension
207°- 218°
Flexion
168° - 181°
Radial dev
314° - 294°
Extension
218° - 240°
Flexion
181° - 186°
Radial dev
I used the program Kinovea to calculate and trace the joint angles in each frame. All angles were
calculated in a counterclockwise direction. Shoulder angle of frame 2 was mistakenly calculated in the
opposite direction, so that angle was just subtracted from 360 in order to get the correct calculation.
The change of angles in the lower limb, especially knee and ankle can be reasoned to be due because
of the fact that the person in the wheelchair is not paralyzed and therefore unconsciously contracted
muscles in her legs due to the effort that was needed to push the chair. These changes can be
neglected.
External Forces
(Hoffman. 2009)
For this analysis I have decided to consider the individual and
the wheelchair as one “object”, therefore I would like to use
the example shown in the image on the right to depict the
external forces generated on a wheelchair (and the user).
There is a vertical ground reaction force acting on the wheels,
a forward friction force (because the wheel is in turning
backward direction -so against the friction force-), there is also
an air (fluid) resistance, which, in my movement analysis I will
ignore due to the relative slow speed at which the individual is
propelling forward.
In order to calculate how these external forces act on the
individual, I need to know some details. The weight of the
person (60KG), the weight of the wheelchair (20KG). By
having these facts, I know that the force with which gravity is
pulling on the GCM of the P+W (person and wheelchair) is -800N.
8
10. The ground reaction force on the wheel is always the same, and always vertical. By combining the force
of friction and the vertical ground reaction force we can assume the GRF would be slightly tilted forward
in order for the wheelchair to be able to propel forward (or the wheel to turn backward without slipping on
the surface). In this movement analysis I must focus instead on the reaction forces applied by the hand
on the pushrim of the wheel.
In order to understand the relationship between the forces applied on the pushrim by the hand, and the
forces that the pushrim exerts on the hand I had to rely on a few articles that wrote about this specific
subject (Bednarczyk et al. 1995, Robertson et al. 1996, Morrow et al. 2010). Despite the publication date
of these articles, they are of high quality and very commonly referenced to in other scientific papers.
External (handrim) forces acting on the hand. Summation
of tangential and radial forces
(Robertson et al. 1996)
The pictures above and on the left display the forces the hand applies on the pushrim throughout the
propulsion cycle, while the picture to the right display the pushrim reaction force throughout the same
cycle (the equivalent of the GRF on a foot). The lengths of the lines that represent the magnitude of the
forces that act on the hand are estimated based on the articles used.
The picture above shows what an estimation of the external forces taken from Robertson et al (1996)
would look like on my analysis.These forces would only be applied to the patient during push phase
(black pushrims and red arrows). During recovery phase the only force acting on the arm (regardless of
the specific joint analyzed) would be gravity (which in the picture is shown as the orange arrow)
9
11. The picture below displays the forces and moment that Robertson et al used to analyze the propulsive
stroke. Fx represents horizontal force, Fy vertical force; and Mz moment around the hub (or axis of the
wheel). Fr represents the radial force, and Ft the tangential force. These forces and their paths are very
important when analyzing the joints and considering the clinical impact of them. These will be reviewed
in the next section.
10
12. Joint Analysis
Shoulder Joint Analysis Free Body Elbow Joint Analysis Free Body Wrist Joint Analysis Free Body
For the joint analysis I have chosen to determine the free body parts as the body part distal from the joint
that I am analyzing. This is because of the forces applied to the arm through the handrim.
In order to calculate the PCM of the arm in each frame, I made use of the displacement method (Loozen
2014) for PCM calculation. In this stance, and for calculation reasons, I am only including the weight of
the person’s body, and neglecting the weight of the wheelchair, therefore I will use the GCM of the
person alone as a reference point, and not the GCM of wheelchair and person combined.
Picture showing the mean external forces acting on the individual during push phase
The position of the PCM of the arm has slightly shifted in each frame due to the reduction of the weight
of the rest of the body (purple star). The PCM of the arm shows a forward and vertical displacement
across the cycle. The red arrows display the reaction force of the rim on the arm at the specific frame,
11
13. while the orange arrows display the gravitational force acting on the arm during recovery phase; the
black circles represent the wheel at which the hand is in contact with the pushrim. This force was
approximated based on the study by Robertson et al. There are no external forces applied onto the arm
when there is no contact with the pushrim. At this point the only force acting on the arm is gravitational
force pulling the arm down.
The table below shows the calculated lever arms and moments in each frame of each phase.The total
weight of the arm was calculated by finding 7% of the total body weight (60kg). The forearm and hand is
equal to 3% of the total body weight, and the hand only 0.5%. All results are shown in the table.
The scale used to measure the lever arm 1:8 (size of the upper arm, forearm or hand) depending on the
joint analyzed.
The formula used to calculate the force of gravity was: N% body weight below joint
body weight acceleration of gravity*
= x
The formula used to calculate moment of gravity was: orce of gravity xternal lever arm x Nmf ×e =
Frame Shoulder Joint
Total weight of arm = 7% total body
weight = 4.2kg
Force of gravity: 4.2 * -10m/s2 = -42N
Moment of Gravity: FG * external lever
arm= - x Nm
Elbow Joint
weight of forearm + hand= 3% total
body weight = 1.8kg
Force of gravity: 1.8 * -10m/s2 = -18N
Moment of Gravity: FG * external lever
arm= - x Nm
Wrist Joint
Total weight of hand = 0.5% total body
weight = .3 kg
Force of gravity: .3 * -10m/s2 = -3N
Moment of Gravity: FG x external lever
arm= - x Nm
1
2
12
15. 7
When the individual applies a moment to the pushrim, the moment at the hub is the sum of the hand
moment and the tangential component transmitted from the hand to the pushrim (Mhub = Mzhand + Ft
xR-1) and it can also be used to calculate net joint moments. (Bednarczyk et al. 1995, Robertson et al.
1996) Net joint forces and moments represent the overall forces seen across joint structures. They
represent a combination of inertial factors, muscle contractions, and segmental weights.
The horizontal and vertical forces seen at the pushrim are the major contributors to the net joint reaction
forces, and analysis of these forces at the pushrim reflects what is happening at the joints. The
tangential and radial pushrim forces represent how effectively an individual applies force to the pushrim,
therefore how efficiently they propel.
The stick figure represents the position of the arm, forearm, and hand when
the peak vertical reaction force (mean value) was reached. The mean start
position (x) and end position (o) are indicated. The peak value was reached
at 62%. As it is visible in my screenshots, the peak force is different than the
one shown on the analysis by Robertson et al. This can be assumed that is
due to several reasons, including: 1. The wheelchair user in my video is not
an experienced wheelchair user, 2. The wheelchair used is not designed to
be pushed by the person sitting in it 3. The wheels were not pumped
correctly, forcing the person to adapt the pushing technique for the
wheelchair to follow a somewhat straight line, and 4. The ground was uneven
and slightly tilted.
Robertson et al showed peak pushrim forces to average between 66 and 95N
tangentially and 43 to 39N radially for a propulsion speed of approximately
.75m/s.
According to Robertson et al, average peak shoulder, elbow, and wrist moments are -19.6, -12.3, and
5.8 Nm. Vertical forces at the pushrim averaged 57N. Veeger et al reported peak vertical forces between
88 and 152N for propulsion speeds between 1.11 and 1.67m/sec. Joint moments were between 22 to
36Nm for the shoulder, 5 to 10Nm for the elbow and 4 to 9Nm for the wrist. Robertson et al. analysis
focused on tangential forces (Ft), the portion of the force driving the wheelchair forward, and radial
forces (Fr), the portion of the force directed radially. Fr, although not involved in moving the wheelchair,
is required to create friction between the hand and the pushrim. (Veeger et al. 1992 Shimada et al. 1998,
Kootz et al. 2005) As it will be shown in the next sections, the values calculated in the analysis of the
video used for this study vary dramatically from the ones found by Robertson et al and Veeger et al. This
14
16. can be due to the limitations in image capturing and analyzing tools, as well as the reasons previously
stated on the difference of peak forces.
From an efficiency standpoint, the greater proportion of force directed tangential to the pushrim, the
greater the moment developed at the hub. Some radial force is required to provide friction such that a
tangential force can be produced. However, people who apply large non-tangential forces will need
larger total forces to maintain the same velocity. This has implications for injury meaning that if larger
forces are required at the pushrim, then greater joint forces and moments are developed. Lower peak
forces paired with longer stroke time decreases exposure of joints to harmful forces without decreasing
speed. A rapid force at pushrim contact may expose joint structures to rapid rates of loading which will
ultimately produce trauma. This implies that forces at the pushrim are the main contributor to the
reaction forces seen at the joints. It is expected that at higher speeds the larger inertial component
would increase the forces across the shoulder. The vertical forces the pushrim force is directed vertically
with reference to the global coordinate system. These forces averaged 57N. Vertical forces, when
transmitted to the shoulder, have a tendency to drive the head of the humerus into the acromion This
upward driving force may place the shoulder at risk for the development of rotator cuff tears or
impingement syndromes. (Robertson et al. 1996, Curtis et al. 1999, Morrow et al 2011)
15
17. Muscle activity
Phase 1
Joint analyzed Shoulder Elbow Wrist
Angle Start 295 239 193
Angle End 294 256 192
Movement Extension Flexion Ulnar dev
Moment of Gravity Initial position: -9.24Nm
Final position: -7.56Nm
Counterclockwise:
Flexion
Initial position: -.54Nm
Final position: -1.26Nm
Clockwise: Extension
Initial position: 0Nm
Final position: 0Nm
No moment of gravity
Moment PRF Extension Extension Radial dev
Moment Muscles Extension Flexion None
Monoarticular Muscles Flexors: Isometric
Extensors: Isometric
Flexors: Concentric
Extensors: Eccentric
Ulnar deviators:
Isometric (change in
angle can be neglected)
Radial deviators:
Isometric
Biarticular muscles Biceps: Concentric
(shoulder is not moving
[measurement can be
neglected], but elbow is
flexing)
Triceps: Eccentric (the
change of angle is
negligible. The triceps is
eccentrically contracting by
extending the shoulder
while the elbow is flexing)
Biceps: Concentric
(elbow is flexing to a
bigger extent than
shoulder is extending)
Triceps: Eccentric
---------------------------------
---------------------------------
---------------------------------
---------------------------------
---------------------------------
Discussion: The reason why biarticular muscles are considered to be acting concentrically and eccentrically
as opposed to isometrically is due to the very small (negligible) change of angle in shoulder extension, but
more drastic elbow flexion, leading us to believe that monoarticular shoulder extensors and flexors are
acting isometrically to maintain the shoulder in its extended position throughout this phase. Biarticular
muscles (biceps and triceps), unlike in other phases, are acting concentrically and eccentrically in this phase
because of the elbow flexion. Wrist calculations were difficult to carry out due to the picture quality, but
because of the very small change in angle it can be assumed that muscle contractions affecting the wrist are
isometric. Due to the very small lever arm on the wrist joint, the moment of gravity is equal to 0.
16
18. Phase 2
Joint Analyzed Shoulder Elbow Wrist
Angle Start 294 256 192
Angle End 350 215 157
Movement Flexion Extension Ulnar dev
Moment of Gravity Initial position: -7.56Nm
Final position: -0.42Nm
Counterclockwise:
Flexion
Initial position: -1.26Nm
Final position: -1.8Nm
Clockwise: Extension
Initial position: 0Nm
Final position: -0.03Nm
Clockwise: Ulnar dev
*Can be neglected
because of the small pull
Moment PRF Extension Flexion Radial dev
Moment Muscles Extension Flexion Radial dev
Monoarticular Muscles Flexors: Concentric
Extensors: Eccentric
Flexors: Eccentric
Extensors: Concentric
Ulnar deviators:
Concentric
Radial deviators:
Eccentric
Biarticular muscles Biceps: Isometric
(Shoulder is flexing and
elbow is extending)
Triceps: Isometric
(Shoulder is flexing and
elbow extending)
Biceps: Isometric
Triceps: Isometric
--------------------------------
--------------------------------
--------------------------------
--------------------------------
--------------------------------
--------------------------------
--------------------------------
Discussion: Based on the theory of biarticular muscles proposed by van Ingen Schenau (1990), the
biarticular muscles are acting isometrically during this movement (it can be compared to a jumping leg) by
transforming the large muscle actions into joint actions. The shoulder is flexing, and the elbow is extending,
consequentially pushing the wheel forward. These biarticular muscles also are contracting isometrically when
analyzing the elbow joint.
17
19. Phase 3
Joint Analyzed Shoulder Elbow Wrist
Angle Start 350 215 157
Angle End 352 201 163
Movement Flexion Extension Radial dev
Moment of Gravity Initial position: -0.42Nm
Final position: -2.94Nm
Clockwise: Extension
Initial position: -1.8Nm
Final position: -1.62Nm
Clockwise: Extension
Initial position: -0.03Nm
Final position: 0Nm
Clockwise: Ulnar dev
*Can be neglected because
of the small pull
Moment PRF Flexion Flexion Radial dev
Moment Muscles Flexion Flexion Radial dev
Monoarticular Muscles Flexors: Isometric*
Extensors: Isometric*
*Because of the very
small change in angle
Flexors: Eccentric
Extensors: Concentric
Ulnar deviators:
Eccentric
Radial deviators:
Concentric
Biarticular muscles Biceps: Eccentric
Triceps: Concentric (the
higher extension in elbow
compared small flexion in
shoulder leads to this
conclusion)
Biceps: Eccentric
Triceps: Concentric
--------------------------------
--------------------------------
--------------------------------
--------------------------------
Discussion: Same reasoning applies to this phase as to the first phase. There is a very small change in angle
on the shoulder joint, leading us to believe that it either is a miscalculation due to restricted tools and image
quality, or simply the bigger change in angle at the elbow joint means that biarticular muscles crossing the
shoulder and the elbow are acting concentrically and eccentrically as opposed to isometrically. In this case,
the bigger extension movement at the elbow compared to the flexion movement at the shoulder leads us to
believe that the biceps is contracting eccentrically and the triceps is contracting concentrically.
18
20. Phase 4
Joint Analyzed Shoulder Elbow Wrist
Angle Start 352 201 163
Angle End 341 207 168
Movement Extension Flexion Radial dev
Moment of Gravity Initial position: -2.94Nm
Final position: -2.1Nm
Clockwise: Extension,
then flexion
Initial position: -1.62Nm
Final position: -0.9Nm
Clockwise: Extension
Initial position: 0Nm
Final position: 0Nm
No moment of gravity
Moment PRF None None None
Moment Muscles Flexion, then extension Flexion No muscle moment
Monoarticular Muscles Flexors: Eccentric
Extensors: Concentric
Flexors: Concentric
Extensors: Eccentric
Ulnar deviators:
Eccentric
Radial deviators:
Concentric
Biarticular muscles Biceps: Isometric
(shoulder is extending
but elbow is flexing)
Triceps: Isometric
Biceps: Isometric
(shoulder is extending
but elbow is flexing)
Triceps: Isometric
---------------------------------
---------------------------------
---------------------------------
---------------------------------
Discussion: Biarticular muscles are isometrically contracting in this phase (following Ingen Schenau theory),
allowing the shoulder to perform an extension movement and the elbow to flex. During this phase, the hand is
no longer in contact with the pushrim, and therefore the only force acting on the shoulder, elbow and wrist
joints is the pull of gravity and the muscle pull.
19
21. Phase 5
Joint Analyzed Shoulder Elbow Wrist
Angle Start 341 207 168
Angle End 314 218 181
Movement Extension Flexion Radial dev
Moment of Gravity Initial position: -2.1Nm
Final position: -8.4Nm
Counterclockwise:
Flexion
Initial position: -0.9Nm
Final position: -0.18Nm
Clockwise: Extension
then flexion
Initial position: 0Nm
Final position: -0.03Nm
Clockwise: Ulnar dev
Moment PRF None None None
Moment Muscles Extension Flexion then extension Radial dev
Monoarticular Muscles Flexors: Eccentric
Extensors: Concentric
Flexors: Concentric
Extensors: Eccentric
Ulnar deviators: Eccentric
Radial deviators:
Concentric
Biarticular muscles Biceps: Isometric
(shoulder is extended but
elbow is flexing)
Triceps: Isometric
(shoulder is extended but
elbow is flexing)
Biceps: Isometric
(shoulder is extended but
elbow is flexing)
Triceps: Isometric
(shoulder is extended but
elbow is flexing)
----------------------------------
----------------------------------
----------------------------------
----------------------------------
Discussion: During this phase biarticular muscles crossing the shoulder and the elbow are isometrically
contracting due to the opposing movements of these two joints. The radial deviators of the wrist are
concentrically contracted in preparation for the hand to come in contact with the pushrim.
20
22. Phase 6
Joint Analyzed Shoulder Elbow Wrist
Angle Start 341 218 181
Angle End 294 240 186
Movement Extension Flexion Radial dev
Moment of Gravity Initial position: -8.4Nm
Final position: -9.24Nm
Counterclockwise: Flexion
Initial position: -0.18Nm
Final position: -0.54Nm
Clockwise: Extension
Initial position: -0.03Nm
Final position: 0Nm
Clockwise: Ulnar dev
Moment PRF None *Until final contact
when there is an extension
moment
None *Until final contact
when there is a flexion
moment
None *Until final contact
when there is a radial
dev moment
Moment Muscles Extension Flexion Radial dev
Monoarticular Muscles Flexors: Eccentric
Extensors: Concentric
Flexors: Concentric
Extensors: Eccentric
Ulnar deviators:
Eccentric
Radial deviators:
Concentric
Biarticular muscles Biceps: Isometric
(shoulder is extending but
elbow is flexing)
Triceps: Isometric
(shoulder is extending but
elbow is flexing)
Biceps: Isometric
(shoulder is extending
but elbow is flexing)
Triceps: Isometric
(shoulder is extending
but elbow is flexing)
----------------------------------
----------------------------------
----------------------------------
----------------------------------
Discussion: During this phase the arm is preparing to come back in contact with the pushrim, to start a new
push cycle. At this time the monoarticular shoulder extensors, elbow flexors, and radial deviators are
contracting concentrically, while the biarticular flexors and extensors crossing the shoulder and elbow are
contracting isometrically.
21
23. The anterior fibers of the deltoid, pectoralis major and biceps brachii act primarily during the push
phase and contraction start towards the end of the recovery phase with load peaks at around 10% of
the pushing phase; conversely, the activity of the triceps brachii is initially quite modest during push
phase (acting as a synergist to the shoulder -providing stability-, and having a isometric contraction as
an elbow extensor), and then it gradually increases during the recovery phase. The deactivation of the
shoulder flexors occurs in the final pushing phase, where the muscles of the recovery phase begin to
act: middle and posterior deltoid, subscapularis, supraspinatus and medium trapezius (the latter 3
muscles acting on the joint on different planes) (Dellabiancia et al. 2013).
Figure 5 –taken from ‘Early motor learning changes in upper-limb dynamics and shoulder complex
loading during handrim wheelchair propulsion’ by Vegter et al– shows a typical example of the different
muscle contributions that counteract the external moment around the glenohumeral joint for each of the
three global axes. Around the global x-axis (sagittal plane), mainly the infraspinatus, subscapularis and
biceps muscles are responsible for the ‘flexion’ moment, with smaller contributions of the
coracobrachialis and pectoralis major. Around the global y-axis (frontal plane) the supraspinatus,
subscapularis and biceps mostly account for the ‘adduction’ moment. The moment around the global
z-axis (transverse plane) is mainly expressed by pectoralis major, biceps and coracobrachialis activity,
but besides the external moment these muscles also have to counteract the vector components of the
infra- and supraspinatus in this plane. DSEM stands for the Delft Shoulder and Elbow model, and is a
finite element, inverse dynamic model describing musculoskeletal behavior of the upper extremity.
(Vegter et al. 2015)
The elbow joint is the least affected joint in the upper limb during wheelchair propulsion, due to the
direction of the forces applied, the wrist and GH joint are more largely affected. (Vegter et al. 2015). It is
known that wheelchair bound people often complain of wrist pain and injuries such as carpal tunnel
syndrome (Sawatzky et al. 2015).
The chart below (figure 6) is taken from ‘Early motor learning changes in upper-limb dynamics and
shoulder complex loading during handrim wheelchair propulsion’ by Vegter et al., and it shows the mean
force and power exerted per push and recovery phase in three different attempts, showing how with
practicing the correct propulsion technique, power is exerted in a more efficient way, and forces are
directed more proportionally.
22
24. This chart also shows the activity of muscles throughout the main two phases, which gives relevant
information to physiotherapists when it comes to training patients with SCI and teaching them how to
push in their wheelchair. As it can be seen, the triceps and rotator cuff are the biggest actors during the
cycle, together with other important muscles such as the pectoralis major and deltoideus. The fact that
the arms are limited to a certain position during the push cycle also help understand the degree of the
wear and tear injuries present in wheelchair users. The forces acting on the joints are always directed in
the same direction, leaving little room for finding a way to prevent these injuries.
Arnet U. et al. (2012) showed in their study comparing hand cycling to wheelchair propulsion that the
mean power of the forces exerted on the joints during motion were significantly smaller with the hand
cycle than the conventional wheelchair.
23
25. Conclusion
Wheelchair propulsion is a very repetitive activity that many people need to perform in order to get
around and complete their activities of daily living. Often times, people who rely on wheelchairs have
disabilities that impair their muscle activity on important levels. The analysis performed for this course
shows the importance of correct technique during wheelchair propulsion, as well as the need to always
create training programs that are unique to the patient’s needs and capabilities.
As it was stated before, the triceps and rotator cuff are the biggest actors during the wheelchair
propulsion cycle, together with the pec major and deltoid. As physical therapists, it is very important to
assess the strength of this group of muscles on patients after injury to create an appropriate strength
rehabilitation plan together with a wheelchair mobility technique class plan to avoid early injuries, as well
as bad propulsion habits that may lead to chronic injuries.
The upper limb is not anatomically designed to undergo such repetitive activities on a daily basis, as well
as to endure such forces that are exerted on it during propulsion. Although these findings have been
known for a long time, more efforts should be made in order to improve the quality of life of wheelchair
users, decrease their pain and physical complaints, and find a way to enhance their ambulation. The
constant strain together with the high forces these muscles have to overcome to keep the wheelchair
moving shines a light on the common injuries and complaints wheelchair users have. It should be
interesting to have a study evaluate the forces needed to propel a wheelchair in day-to-day activities,
(environments that are not ideal for wheelchair propulsion) to get a more realistic picture of what the
anatomical structures of patients endure on a daily basis.
24
26. References
● Arnet U, van Drongelen Stefan, Scheel-Sailer A, van der Woude L H.V, Veeger HE. Shoulder
load during synchronous handcycling and handrim wheelchair propulsion in persons with
paraplegia. J Rehabil Med. 2012;44:222–228.
● Bednarczyk JH, Sanderson DJ. Limitations of Kinematics in the Assessment of Wheelchair
Propulsion in Adults and Children With Spinal Cord Injury. Phys Ther. 1995;75(4):281-289
● Boninger ML, Souza AL, Cooper RA, Fitzgerald SG, Koontz AM, Fay BT. Propulsion patterns
and pushrim biomechanics in manual wheelchair propulsion. Arch Phys Med Rehabil.
2002;83(5):718-23.
● Cooper RA, Boninger ML, Shimada SD, Lawrence BM. Glenohumeral joint kinematics and
kinetics for three coordinate system representations during wheelchair propulsion. Am J Phys
Med Rehabil 1999;78(5):435-46.
● Curtis KA, Drysdale GA, Lanza RD, Kolber M, Vitolo RS, West R. Shoulder pain in wheelchair
users with tetraplegia and paraplegia. Arch Phys Med Rehabil. 1999;80(4):453-7.
● Dellabiancia F, Porcellini G, Merolla G. Instruments and techniques for the analysis of
wheelchair propulsion and upper extremity involvement in patients with spinal cord injuries:
current concept review. Muscles, Ligaments and Tendons Journal. 2013;3(3):150-156.
● Hoffman SJ. Introduction to kinesiology: Studying physical activity. 3rd ed. Illinois, Human
Kinetics. 2009. P.281-286
● Karman HC. Center of gravity of a manual wheelchair. Clin Biomech. 2011;22(7):623-24
● Koontz AM, Cooper RA, Boninger ML, Souza AL, Fay BT. Shoulder kinematics and kinetics
during two speeds of wheelchair propulsion. J Rehabil Res Dev. 2002;39(6):635–49.
● Koontz AM, Cooper RA, Boninger ML, Yang Y, Impink BG, van der Woude LH. A kinetic
analysis of manual wheelchair propulsion during start-up on select indoor and outdoor surfaces.
J Rehabil Res Dev. 2005;42(4):447–58.
● Lemaire ED, Lamontagne M, Barclay HW, John T, Martel G. A technique for the determination
of center of gravity and rolling resistance for tilt-seat wheelchairs. Journal of Rehabilitation
Research and Development. 1991;28(3):51-58
● Loozen B, Moed B. Biomechanics course manual [online]. Amsterdam 2014.
URL:https://drive.google.com/drive/folders/0B_3MSu1Aedr_bk1SbHQzS3BxSHc
● Mercer JL, Boninger M, Koontz A, Ren D, Dyson-Hudson T, Cooper R. Shoulder joint kinetics
and pathology in manual wheelchair users. Clin Biomech. 2006;21(8):781-89.
● Morrow MMB, Hurd WJ Hurd, Kaufman KR, An KN. Shoulder demands in manual wheelchair
users across a spectrum of activities. J Electromyogr Kinesiol. 2010; 20(1): 61–67
25
27. ● Moon Y, Jayaraman C, Hsu IMK, Rice IM, Hsiao-Wecksler ET, Sosnoff JJ. Variability of peak
shoulder force during wheelchair propulsion in manual wheelchair users with and without
shoulder pain. Elsevier Clin Biomech. 2013;28:967–72.
● Robertson RN, Bonninger ML, Cooper RA,Shimada SD. Pushrim Forces and Joint Kinetics
During Wheelchair Propulsion. Arch Phys Med Rehabil. 1996;77(4):856-64
● Russell IM, Raina S, Requejo PS, Wilcox RR, Mulroy S, McNitt-Gray JL. Modifications in
wheelchair propulsion technique with speed. Front Bioeng Biotechnol. 2015;3:171
● Santos Requejo P, McNitt-Gray JL. Editorial: wheeled mobility biomechanics. Front. Bioeng.
Biotechnol. 2016;4(53):1-3
● Shimada SD, Robertson RN, Bonninger ML, Cooper RA. Kinematic characterization of
wheelchair propulsion. Journal of Rehabilitation Research and Development. 1998;35(2):210-18
● Slowik JS, Requejo PS , Mulroy SJ , Neptune RR. The influence of wheelchair propulsion hand
pattern on upper extremity muscle power and stress. J. Biomech. 2016;49:1554-61
● Sosnoff JJ, Rice IM, Hsiao-Wecksler ET, Hsu IMK, Jayaraman C, Moon Y. Variability in
wheelchair propulsion: a new window into an old problem. Front. Bioeng. Biotechnol.
2015;3(105):1-7
● Sawatzky B, DiGiovine C, Berner T, Roesler T, Katte L. The need for updated clinical practice
guidelines for preservation of upper extremities in manual wheelchair users: a position paper.
Am J Phys Med Rehabil. 2015;94(4):313-24
● Van Ingen Schenau GJ. On the action of biarticular muscles, a review. Netherlands Journal of
Zoology. 1990;40(3):521-40
● Veeger HE, Van der Woude LH, Rozendal RH. A computerized wheelchair ergometer. Results
of a comparison study. Scand J Rehabil Med 1992;24:17-23.
● Vegter RJ, Hartog J, de Groot S, Lamoth CJ, Bekker MJ, van der Scheer JW, van der Woude
LH, Veeger HE. Early motor learning changes in upper-limb dynamics and shoulder complex
loading during handrim wheelchair propulsion. Journal of NeuroEngineering and Rehabilitation.
2015;12(26):1-14
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28. Appendix 1 - Moments of Gravity on each joint
27
29. Appendix 2 - Lever arm and Moments of Gravity Calculations
28
