Αccepted Article
Journal of Musculoskeletaland Neuronal Interactions

J Musculoskelet Neuronal Interact 2019

Original Article

Safety considerations for forward falls
Saeed Abdolshah, Nader Rajaei, Yasuhiro Akiyama, Yoji Yamada, Shogo Okamoto
Department of Mechanical Systems Engineering, Nagoya University, Nagoya, Japan

Abstract
Objective: Forward falls are among the most frequent causes of upper extremity fractures. This study investigated
the safety considerations to prevent wrist injuries during bimanual forward falls. Methods: A biomechanical model wasdeveloped with two separated arms to facilitate investigation of asymmetrical contact and predict the impact force applied
to each hand separately. To validate the developed model, a series of fall experiments were conducted in which one handcollided with a hard surface, while the other collided with a soft surface. Results: The results show that the impact force
applied to each hand is independent of the other. Using these results and our model, the safety aspects of human forward
falls were analyzed with a view to preventing injuries. Specifically, we sought to determine the safe range of surface
stiffness and damping to ensure that the occurrence of forward falls does not lead to trauma. Conclusion: The results ofthis study can be applied in the design of compliant flooring to ensure the safety of people in environments with potential
fall hazards. From a robotics viewpoint, the results are applicable in the design of compliant flooring for shared workplaces,
where robots collaborate with people and collisions between humans and robots may cause falls.
Keywords: Bimanual Forward Fall, Biomechanical Model, Compliant Flooring, Impact Force, Wrist Injuries

Introduction
In recent years, fall studies have attracted significant
attention from robotics, safety, and biomechanicalresearchers. Fall-related injuries are the second mostcommon cause of accidental or unintentional injury deaths
worldwide1, which might incur substantial costs and longterm rehabilitation2. Such incidents might frequently occur
in the elderly due to musculoskeletal frailty3–5. The risk
factor associated with fall incidents6 as well as training7,
interventions8, and arresting strategies9 have been widely
studied. The highest percentage of falls among the elderlyis associated with forward walking10. Elevating, lowering,and skip motion have been reported as balance recovery
strategies during walking11; however, unsuccessful recovery
motions can cause injuries and fractures. Forward falls are a

The authors have no conflict of interest.
Corresponding author: Saeed Abdolshah, PhD, Department of Mechanical
Systems Engineering, Nagoya University, Nagoya, Japan. Furo-cho,
Chikusa-ku, Nagoya, 464-8601, Japan
E-mail: saeed.abdolshah@mech.nagoya-u.ac.jp • saeed.abdolshah@tum.de
Edited by: G. Lyritis
Accepted 29 October 2019major cause of upper extremity injuries such as distal radius
fracture, which is the most common type of fracture among
young adults12.
Furthermore, collisions might occur in workplaces where
humans and robots collaborate. Upon collision, although therobot might immediately stand still, the imposed force on
the human body might result in a forward fall. The time for a
falling person to react against a fall13 and avoid fall injuries isonly 500 ms14. Although fall breaking strategies might alter
the applied impact force, a realistic evaluation of the impact
force during a fall and physical interventions to reduce
injuries, such as compliant flooring, are important15. A few
previous studies have proposed biomechanical models to
describe the mechanism behind a forward fall and predicted
the impact force using various models or software16.
Zhou et al.17 measured the tripping force (i.e. obstacle-footimpact force), which was applied to the swing foot in a twelve
degree-of-freedom model. They simulated the forward fallinduced by tripping; however, the human body was modeledwith rigid links, and the effect of the soft tissues was notconsidered. Lo et al.18 used a seven degree-of-freedommodel to investigate the effect of the body configurationon the impact force. Their results showed that not only theupper extremity configuration, but also the lower extremity
adjustments affected the impact force significantly. Xu etal.19 used a five degree-of-freedom model (specifically, a
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S. Abdolshah et al.: Safety considerations for forward falls

model without arms) and formulated the forward fall motion.
Although the arms were not considered in their model, theresults from their study were useful for distinguishing thefalls from daily activities.
Moreover, researchers have conducted experiments to
reproduce fall motion with less severity to investigate theeffective parameters and have proposed biomechanicalmodels inspired by the experimental data. Chiu andRobinovitch20 designed a free-fall experiment to investigate
the impact force during falls. The subjects in their experimentwere instructed to lock their elbows throughout the landing.
Their experimental results indicated that the impact force
is governed by a primary high magnitude peak (fmax1) that
occurs shortly after contact, and a secondary lower peak(fmax2). The first peak impact force usually causes a fracture21.
Moreover, they observed that the ground stiffness reduction
attenuated the magnitude of the first peak impact force, but
did not affect the secondary maximum impact force22. Chiu
and Robinovitch also proposed a two degrees of freedom(DOF) mass-spring-damper model to predict the impact
force during a forward fall resulting from a standing/walking
position. Subsequently, their results were confirmed by23.
The results reported by20,22,23 stemmed from fallexperiments where a single force plate was used to measure
the impact force. These studies assumed that the impact
occurring on one hand deteriorates (i.e. the impact force
decays to zero) and subsequently the other hand strikes theground. Although bimanual forward fall is the most common
strategy24, the model proposed in20 suggested the condition/
situation where a single hand arrests a forward fall. This is
the only model that predicted the hand impact force during
a forward fall from a typical standing/walking position. Later,
several research studies employed the above-mentioned
results to estimate the risk of bone fractures25–27.
The effects of asymmetrical fall conditions including
asymmetric loading and body postures, and asymmetricalcontact (i.e. one hand colliding with a hard surface while
the other hand is in contact with a soft surface) have rarely
been studied. Particularly, very few studies have discussed
the effect of asymmetric loading28, and to the best of ourknowledge, the effect of different types of contact has notbeen studied previously.
In this paper, we seek to ascertain the impact force acting
on each hand during a forward fall with asymmetrical contact.
A series of fall experiments were performed using two force
plates. The subjects were instructed to use a bimanual fallarrest strategy, which is the most common hazardous fall
breaking method among humans. To avoid the previous
assumption20 (i.e. where one hand is delayed until the force
on the other side decays to zero), a force plate was mounted
under each hand to measure the impact force applied toeach hand separately. One force plate was covered by a soft
surface, while the other was considered as a hard surface. A
biomechanical model with two separate arms was developed
inspired by the real experiments. This model enabled us toinvestigate the effect of asymmetrical contact and predict the
impact force applied to each hand separately during an actual
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forward fall. The effects of surface stiffness and damping on
the impact force were investigated, and the safety aspects
necessary to prevent fall-related injuries were discussed.
Related information was also provided, which could be usefulin compliant surface design.

Material and method
Participants
For performing these experiments, we decided touse healthy young subjects to avoid any kind of injuries.
Twenty healthy male subjects ranged between 20 and 38
years participated in this study (mean±standard deviation[SD]=28.7±7.5). Their average heights and weights were
172.4±5.8 cm 64.8±11.3 kg, respectively. The subjects
filled a questionnaire to ascertain that they do not have any
related health problems or special fall arresting skills that
may cause deviations in the results of our experiments. The
participants did not report any bone diseases that would
increase the risk of injuries or may cause any changes in themagnitude of the impact force. None of them suffered frommovement disorders or neurological and medical illnesses,
and they did not have prior training experience regarding fall
prevention, martial arts techniques or Jodo. The subjects
have never experienced serious fall accidents and injuries.
All participants signed a specific consent form before theexperiments and then received a short training. They had an
opportunity to do some test experiments before starting themain trials. This study was conducted with the approval of theInstitutional Review Board of University. All the experiments
were conducted in accordance with the approved guidelines.
Experimental protocol
The experimental area was covered with soft yoga matsfor safety reasons; two separated force plates (US06-H5,
Tech Gihan Co., Ltd., Japan) were installed to measure theimpact force acting on each hand (Figure 1(a)). A supporting
harness was attached to the subject’s trunk. The participants
were instructed to fix their shanks on a soft pillow and extend
their knees to lean forward against the harness. The thighwas set at 30º from the horizontal.
By pulling the supporting harness connected to the trunk,the participants were elevated to reach the proper heightfrom the ground (Figure 1(b)). The subjects were instructed
to keep their elbows fully extended (i.e. outstretched hands)
and the arm angle was set at 15° to the vertical. Thus, theparticipant’s body posture and the experiment’s protocol
were similar to those of previous experiments20,22,23. The
surface of the force plates was considered hard surfaces (i.e.
approximately infinity stiffness), whereas for the fall on a soft
surface, a foam padding adhered to the surface of the force
plate. We designed the experiment to determine the impact
force applied to each hand under the following condition: One
hand strikes the soft surface and the other one strikes thehard surface.
The experiments were performed at heights of h=3 cm
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S. Abdolshah et al.: Safety considerations for forward falls

and 5 cm. The height was measured and set as the distance
between the palm of the hand and force plates. Eachparticipant completed twelve trials, which involved six trials
at h=3 cm, 15 minutes of rest, and six experiments at h=5 cm.
Biomechanical μodel
Previously, a simple 2-DOF system was proposed to
predict the impact force during forward falls26. The model
was proposed based on the assumption that the impact force
acting on one hand deteriorates and then the other handcontacts the ground, which means that all the impact force
is applied to one hand. The proposed model is not able todistinguish the impact force applied to each hand separately.
Specifically, it is not able to evaluate conditions such as thehands striking different types of surfaces or striking the
ground at different times.
To overcome the limitations of the above model andpredict the impact force during forward falls, a spring-massdamper model was proposed (see Figure 2). Let us assume
that the elbow flexion is negligible during the forward fall. In
the figure, m3 is the torso effective mass and m1 and m2 are
the effective masses of the right and left upper extremities.
kr2 and kl2 represent the right and left shoulder and torso
stiffness. cr2 and cl2 are the damping of the shoulder andtorso. kr1, kl1, cr1, and cl1 are the right and left hand, wrist, andpalmar tissue stiffness and damping parameters.
The governing equations of motion can be written as:
x1
x2
x3
θ
xrs
xls
:
:

0
0
0
0
0
0

:

0
0
0
0
0
0

:

0
0
0
I
0
0

:

m1 0 00 m2 00 0 m3
0 0 0
0 0 0
0 0 0

:

Figure 1. The experimental setup. This setup was used toevaluate the impact force during a forward fall on outstretchedarms from heights of 3 and 5 cm. The experimental area wascovered with soft yoga mats for safety reasons (i.e. blue area).

m1g
m2g
m3g
0
0
0
x1
x2
x3
θ
xrs
xls

−kr1−kr20
kr2
kr2L/2
kr1 0
0
kl2
0 kl1
−kl2−kl1−kl2L/2kr2
0kl2−kl2−kr2 kl2L/2−kr2L/2
0
+
kr2
−kl2
kl2−kr2 −kl2L/2−kr2L/2 00
kr1+krs 0
0
−kr1
0
0
0
−kl1
kl1+kls 0
0
0

x1
x2
x3
θ
xrs
xls

.

−cr1−cr20
cr2
cr2L/2
cr1 0
0
cl2
0 cl1
−cl2−cl1−cl2L/2cr2
cl2−cl2−cr2 cl2L/2−cr2L/2 0 0
+
cr2
−cl2
cl2−cr2 −cl2L/2−cr2L/2 0 0
cr1 0
0
−cr1
0
0
0
−cl1
cr1 0
0
0

.
.
.

.
.

(1)
The equations were solved using the Runge-Kutta 4 ordermethod and MATLAB software (MathWorks, 2015) under thefollowing conditions.
thx1(0)=0,x1(0)=υ,.

.

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x3(0)=0,υ= 2gh(2)
The stiffness and damping parameters were measured
beforehand. To obtain similar results but separately for eachhand, we used one-half of the values proposed in20. The
stiffness of the padding was 160 kN/m, which was measured
using the Discovery Hybrid Rheometer (DHR-2-NA, TA
Instruments, US).
.

Figure 2. The biomechanical model. To predict the impact force
during a forward fall on outstretched hands, a spring-massdamper model was proposed.

x2(0)=0,x2(0)=υ, x3(0)=υ,3

S. Abdolshah et al.: Safety considerations for forward falls

Figure 3. Impact force profile for a forward fall. Simulation and experimental impact forces during forward fall on outstretched arms,
where one hand contacts the hard surface and the other contacts the soft surface from heights of (a) 3 cm and (b) 5 cm.

Results
Figure 3 shows the results obtained for one handcontacting the soft surface and the other contacting the hardsurface. As in previous studies, two peaks can be recognized.
The first peak has a higher frequency and magnitude than
the second peak. Increasing the fall height increases the peak
impact forces; however, the first peak is amplified more. The
first peak for a fall from the 3 cm height on a hard surface isapproximately 291±98 N. This force increases to 382±121 N
for the 5 cm fall height. In addition, an independent-samples
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t-test was conducted to show the effect of the falling height(i.e. 3 cm and 5 cm) on the magnitude of the impact force.
The result of statistical analysis (IBM SPSS V.23) confirmedthat the magnitude of the impact force increases significantlywith increases in the falling height (p<0.001).
Our proposed model can predict the magnitude of the
impact force applied to each hand separately; however, aswith previously proposed models20,22,23, it cannot correctly
estimate the timing of the peak impact forces. Usually, thefirst peak occurs in a range of 20 to 30 ms after impact;
however, the simulation predicts the first peak as occurring
immediately after impact. The timing of the second impact
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S. Abdolshah et al.: Safety considerations for forward falls

Figure 4. Peak impact force-fall height graph. The peak impact force changes as a function of the fall height; point A shows the borderof the safe fall height, and point B indicates the impact force applied to the hand during a forward fall from a standing posture.

Figure 5. Energy absorption-fall height graph. The energy absorbed by one hand as a function of fall height. The absorbed energy
from a walking position is indicated by point B.

force was also over-estimated.
The soft surface affects the first impact force significantly.
In contrast, the second peak does not change noticeably.
The first peak impact force of falls from 3 and 5 cm heights
decreased to 201±81 N and 243±84 N respectively (i.e.
approximately 30% and 36% reduction in the first peak
impact force compared to the fall on a hard surface forfalls from 3 cm (p<0.002) and 5 cm (p<0.005) heights). In
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addition, the peaks were delayed and the first impact force
occurred in the range of 30 to 60 ms. The statistical analysis
also confirmed that the first peak impact force significantly
decreased for the heights of 3 cm (p<0.001) and 5 cm
(p<0.001) during forward fall on a soft surface compared toa hard surface. A comparison of our results with different fallcontact conditions (e.g., both hands contacting a hard surface
and both hands contacting a soft surface), reveals that the5

S. Abdolshah et al.: Safety considerations for forward falls

Figure 6. Peak impact force-surface stiffness graph. The effect of surface stiffness on the peak impact force applied to the hand.
Point A shows the border of the safe fall height.

Figure 7. Peak impact force change based on surface stiffness and damping parameters. The effect of a surface with both damping
and stiffness elements on the peak impact force during typical forward fall of a human from a height of 75 cm (i.e. standing posture).

magnitude of the peak impact force applied to each hand isindependent of the condition of the other hand.
To validate our model, it was used to predict the impact force
applied to a hand for forward falls from greater fall heights.
Figures 4–7 are associated with the safety issues of forward
fall. The presented plots were estimated based on the averagecharacteristics of male and female bodies20. Figure 4 shows
how the fall height increment leads to increases in the peak
impact force. Several researchers have investigated wrist
fractures and reported very different fracture loads. Recent
studies29 have shown that the probability of distal radius
fracture with maximum impact forces of 551 N, 1053.6 N,
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and 1858.2 N are 10%, 25%, and 50%, respectively. A riskorder of 10–25% is recommended for design applications.
In another study30, a maximum force of 1580±600 N was
considered as the fracture force among females. Thus, we
specified A as the safe border of the impact force with 980
N in Figure 4. This point reflects a fall height of 0.438 m as
the maximum safe falling height. The corresponding impact
velocity is 2.93 m/s.
A fall from a standing position is usually considered asa fall from a height approximately one-half of the subject’s
height31,32 or 75 cm20. Point B is associated with the impact
force applied to the hand from a walking position with a fall
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S. Abdolshah et al.: Safety considerations for forward falls

height of 75 cm. Such a fall posture imposes an impact force
on the hand that is equivalent to 1285 N. In cases of higher fallheights, such as 95 cm, the maximum impact force applied tothe hand is 1446 N. Consequently, it can be inferred that therisk of fracture for a person falling from a standing/walking
position is more than 25% and less than 50%.
The energy absorbed by a hand as a function of fall heightis illustrated in Figure 5. The absorbed energy increases
with fall height. The energy absorption magnitude can also
be considered as another important risk factor for wrist
fractures. The absorbed energy for a fall height of 75 cm isapproximately 19 J (Point B).
The effect of surface stiffness reduction on impact force
attenuation is shown in Figure 6. This graph reflects the factthat the application of compliant flooring reduces the impact
force significantly. Point A (indicating 980 N), is responsible
for the application of compliant flooring with a stiffness of
480 kN/m.
A compliant surface can be defined not only by stiffness
characteristics, but also damping feature. Let us imagine
a surface with both stiffness and damping specifications.
Figure 7 depicts the contour plot of the peak impact forcechanges based on the surface stiffness and damping for atypical forward fall from a standing position (i.e. 75 cm fallheight). The safe range can be considered as the region
under the 980 N line. This line starts from a stiffness of 980
kN/m without any damping characteristics of the surface andends on the stiffness of 1000 kN/m and 0.45 kNs/m as thedamping parameter.

Discussion
The bimanual fall-arresting strategy is the most common
strategy among people. In this paper, we proposed abiomechanical model that has two arms to calculate theimpact force applied to the hands during forward falls. The
model enables us to calculate the applied force to eachhand separately, especially when the contacting condition isdifferent, such as striking the hands on two different types of
surfaces (i.e. asymmetrical contact type). A set of experiments
was designed to validate our model by evaluating the impact
force applied to each hand.
Our results show that the impact force acting on the handconsists of two distinct peaks. The frequency and magnitudeof the first peak are considerably higher than that of thesecond. The results show that the compliant surface reduces
the first peak value significantly, but does not affect thesecond peak notably. In addition, the peaks were delayedcompared to the fall on the hard surface. A comparison of theresults shows that the impact force applied to one hand does
not affect that of the other.
In previous studies, only one force plate was used tomeasure the impact force and the related experiments wereconducted under the assumption that the impact force acting
on one hand falls to zero and then the other hand contacts
the ground. Considering this hypothesis, the impact force
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against one hand (e.g., 2.7 kN for a typical fall from standing
position20) generates a very high torque that leads to bodyrotation around the shoulder and the body loses balance.
In some of our experiments, one hand struck the groundshortly before the other and the measured impact force
was similar to the condition when both hands impacted theground simultaneously. Even if one hand contacts the groundsignificantly before the other one, the impact forces applied
to the hands show the results similar to the condition where
both hands contact the ground at the same time15. The
conclusion stemming from this fact proves that the previous
assumption to break a fall using only one hand is not realistic.
We estimated the impact force applied to each hand over
the range 1285 N to 1446 N. Based on previous studies,
we assumed that 980 N is a safe fracture border. Although
the wrist fracture strongly depends on bone strength,
the magnitude of the induced impact force significantly
affects the possibility of a fracture occurring. Thus, we
can assume that the force applied to the hand is strongly
associated with a risk of wrist injuries. Thus, based on
our results, a forward fall may cause a fracture due toexcessive force higher than bone fracture threshold. A soft
surface can attenuate the impact force and delay the peak
impact forces. Thus, it is desirable to cover the surface
with a soft material to prevent injuries in playgrounds andworkplaces, where robots collaborate with people any
collision between human and robot may result in a fall.
A stiffness component has the capability to receive andstore motion energy and then release it over an extended
period, consequently resulting in impact force attenuation.
A damping element dissipates the energy and causes
further impact force reduction. We presented a contour
plot that depicts the effect of surface stiffness and damping
elements on the first peak impact force. This graph provides
information that can be used by researchers to design a soft
surface to attenuate the impact force and the severity of
injuries. From a design perspective, compliant flooring may
have both damping and stiffness characteristics; however, toavoid an increase in the falling risk, the surface should not be
excessively soft.
Mounting handrails is an effective means to prevent falls or
reduce fall-related injuries. The handrails should be installedat an appropriate height to prevent falls or limit the impact
velocity to a safe range. The presented graphs can provide
useful information for designers to determine an optimum
height for installing handrails.

Conclusion
Realistic assessment of the force acting on the hands
during forward falls is necessary to design compliant
surfaces to prevent injuries. In this study, we investigatedthe most common fall-arresting strategy (namely, bimanual
fall breaking) under asymmetrical contact and measured
the impact force of each hand separately. To address the
problem, a series of fall experiments were conducted in
7

S. Abdolshah et al.: Safety considerations for forward falls

which a force plate was mounted under each hand. Further,to produce a different contact surface type, one of the force
plates was covered with a soft padding layer.
The results obtained show that the impact force applied
to each hand is independent of the other. The impact force
profile consists of two peaks-a high peak followed by a low
peak. The experimental and simulation results indicate thatthe impact force is strongly associated with the fall height(i.e. impact velocity).
A spring–damper–mass model simulating bimanual
forward fall arresting, with rigid masses representing theeffective mass of body segments, and springs and dampers
representing muscles and soft tissues was also developed.
The developed model was validated and used to investigate
the effect of surface stiffness and damping on the peak impact
force during a typical human forward fall. Thus, we were able
to determine a range of stiffness and damping values for thesurface to prevent forward fall injuries.
The results obtained in this study are useful for designers
who wish to produce appropriate compliant flooring to
reduce the risk of injuries in places such as playgrounds or
nursing homes where fall accidents may occur frequently.
From a robotics perspective, this kind of compliant flooring isnecessary for human-robot collaboration workplaces, wherecollisions between humans and robots may result in falls.
Acknowledgement
This work was supported by JSPS KAKENHI Grant Number 26750121
and 30813787, and METI “Strategic international standardization
promotion project: International standardization of human tolerance
against fall injuries”.

References
1.

2.

3.

4.

5.

6.

7.

World Health Organization. Falls fact sheet. Available:
https://www.who.int/news-room/fact-sheets/detail/falls, on November, 29, 2017.
Dionyssiotis Y, Dontas IA, Economopoulos D, Lyritis GP.
Rehabilitation after falls and fractures. J Musculoskelet
Neuronal Interact 2008;8(3):244-50.
Runge M, Rehfeld G, Resnicek E. Balance training andexercise in geriatric patients. J Musculoskelet NeuronalInteract 2000;1(1):61-5.
Hanssens L, Reginster JY. Relevance of bone mineraldensity, bone quality and falls in reduction of vertebral
and non-vertebral fractures. J Musculoskelet NeuronalInteract 2003;3(3):189-193.
Schacht E, Richy F, Reginster J. The therapeutic effectsof alfacalcidol on bone strength, muscle metabolism
and prevention of falls and fractures. J Musculoskelet
Neuronal Interact 2005;5(3):273-284.
Runge M, Schacht E. Multifactorial pathogenesis
of falls as a basis for multifactorial interventions. J
Musculoskelet Neuronal Interact 2005;5(2):127-134.
Allison SJ, Brooke-Wavell K, Folland J. High and odd
impact exercise training improved physical function
and fall risk factors in community-dwelling older men. J

http://www.ismni.org

Musculoskelet Neuronal Interact 2018;18(1):100-107.
Fusco A. Are multifactorial and multiple component
interventions effective in preventing falls in older people
living in the community? A Cochrane Review summarywith commentary. J Musculoskelet Neuronal Interact
2019;19(1):1-3.
9. Abdolshah S, Rajaei N, Akiyama Y, Yamada Y, Okamoto S.
Longitudinal Rollover Strategy as Effective Intervention
to Reduce Wrist Injuries During Forward Fall. IEEE Robot
Autom Lett 2018;3(4):4187-4192.
10. Robinovitch SN, Feldman F, Yang Y, Schonnop R, Leung
PM, Sarraf T, Sims-Gould J, Loughin M. Video captureof the circumstances of falls in elderly people residing
in long-term care: an observational study. The Lancet
2013;381(9860):47-54.
11. Mitsuoka K, Akiyama Y, Yamada Y, Okamoto S. Analysis
of Skip Motion as a Recovery Strategy after an Induced
Trip. The 2015 IEEE International Conference on
Systems, Man, and Cybernetics (SMC2015); 2015. p.
911-916.
12. Sahlin Y. Occurrence of fractures in a defined population:a 1-year study. Injury 1990;21(3):158-60.
13. Abdolshah S, Akiyama Y, Mitsuoka K, Yamada Y,
Okamoto S. Analysis of upper extremity motion duringtrip-induced falls. The 26th IEEE International Symposium
on Robot and Human Interactive Communication (ROMAN); 2017. p. 1485-1490.
14. DeGoede KM, Ashton-Miller JA, Liao JM, Alexander
NB. How quickly can healthy adults move their hands tointercept an approaching object? Age and gender effects.
J Gerontol A Biol Sci Med Sci 2001;56(9):M584-8.
15. Rajaei N, Abdolshah S, Akiyama Y, Yamada Y, Okamoto
S. Rigid material on top of a compliant flooring effectively
reduces the impact force in the event of a forward fall. In
2018 IEEE International Conference on Intelligence and
Safety for Robotics (ISR); 2018. p. 273-277.
16. Rajaei N, Abdolshah S, Akiyama Y, Yamada Y, Okamoto
S. Evaluation of forward fall on the outstretched handusing MADYMO human body model. In seventh IEEE
International Conference on Biomedical Robotics andBiomechatronics (Biorob); 2018. p. 954-959.
17. Zhou X, Draganich LF, Amirouche F. A dynamic model
for simulating a trip and fall during gait. Med Eng Phys
2002;24(2):121-7.
18. Lo J, Ashton-Miller JA. Effect of upper and lower
extremity control strategies on predicted injury risk
during simulated forward falls: a study in healthy young
adults. J Biomech Eng 2008;130(4):041015.
19. Xu JX, Sun Y, Pang CK. Modelling human falling process
based on a five-link bipedal robot. 8th IEEE International
Conference on Control and Automation (ICCA); 2010. p.
2212-2217.
20. Chiu J, Robinovitch SN. Prediction of upper extremity
impact forces during falls on the outstretched hand. J
Biomech 1998;31(12):1169-76.
21. Wigderowitz CA, Paterson CR, Dashti H, McGurty D,
Rowley DI. Prediction of bone strength from cancellous
8.

8S. Abdolshah et al.: Safety considerations for forward falls

structure of the distal radius: can we improve on DXA?
Osteoporos Int 2000;11(10):840-6.
22. Robinovitch SN, Chiu J. Surface stiffness affects impact
force during a fall on the outstretched hand. J Orthop
Res 1998;16(3):309-13.
23. Kawalilak CE, Lanovaz JL, Johnston JD, Kontulainen SA.
Linearity and sex-specificity of impact force prediction
during a fall onto the outstretched hand using a singledamper-model. J Musculoskelet Neuronal Interact
2014;14(3):286-93.
24. DeGoede KM, Ashton-Miller JA, Fall arrest strategy
affects peak hand impact force in a forward fall. J
Biomech 2002;35(6):843-848.
25. Dalzell N, Kaptoge S, Morris N, Berthier A, Koller B,
Braak L, Van Rietbergen B, Reeve J. Bone microarchitecture and determinants of strength in the radius
and tibia: age-related changes in a population-based
study of normal adults measured with high-resolution
pQCT. Osteoporos Int 2009;20(10):1683-94.
26. Melton LJ, Christen D, Riggs BL, Achenbach SJ, Müller
R, van Lenthe GH, Amin S, Atkinson EJ, Khosla S.
Assessing forearm fracture risk in postmenopausal
women. Osteoporos Int 2010;21(7):1161-9.
27. Hansen S, Shanbhogue V, Folkestad L, Nielsen MM,
Brixen K. Bone microarchitecture and estimated

http://www.ismni.org

strength in 499 adult Danish women and men: a crosssectional, population-based high-resolution peripheral
quantitative computed tomographic study on peak bone
structure. Calcif Tissue Int 2014;94(3):269-81.
28. Burkhart TA, Brydges E, Stefanczyk J, Andrews DM.
The effect of asymmetrical body orientation during
simulated forward falls on the distal upper extremity
impact response of healthy people. J Electromyogr
Kinesiol 2017;33:48-56.
29. Burkhart TA, Andrews DM, Dunning CE. Multivariate injury
risk criteria and injury probability scores for fractures tothe distal radius. J Biomech 2013;46(5):973-8.
30. Myers ER, Hecker AT, Rooks DS, Hipp JA, Hayes
WC. Geometric variables from DXA of the radiuspredict forearm fracture load in vitro. Calcif Tissue Int
1993;52(3):199-204.
31. Hansen S, Brixen K, Gravholt CH. Compromised trabecular
microarchitecture and lower finite element estimatesof radius and tibia bone strength in adults with turner
syndrome: A cross-sectional study using high-resolutionpQCT. J Bone Miner Res 2012;27(8):1794-803.
32. Melton LJ, Christen D, Riggs BL, Achenbach SJ, Müller
R, van Lenthe GH, Amin S, Atkinson EJ, Khosla S.
Assessing forearm fracture risk in postmenopausal
women. Osteoporos Int 2010;21(7):1161-9.

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