Investigation into Hand Impact Force during Forward Falls
on Uneven Terrain
Saeed Abdolshah*, Nader Rajaei*, Yasuhiro Akiyama*, Yoji Yamada*, Shogo Okamoto**Department of Mechanical Systems Engineering
Nagoya University, Nagoya, Japan

Corresponding Author:
Saeed Abdolshah, PhD (ORCID: 0000-0003-0077-5757)
Department of Mechanical Systems Engineering
Nagoya University, Nagoya, Japan
Furo-cho, Chikusa-ku, Nagoya, 464-8601, Japan
Email: saeed.abdolshah@mech.nagoya-u.ac.jp, saeed.abdolshah@tum.de
Tel/Fax: +81-52-789-5330

Acknowledgment
This work was supported by JSPS KAKENHI Grant Number 26750121 and 30813787, and METI (Ministryof Economy) “Strategic international standardization promotion project: International standardizationof human tolerance against fall injuries”. The authors have no financial relationships that may cause aconflict of interest.

1

Abstract
Outdoor falls predominantly occur because of environmental factors, such as tripping caused byuneven terrain; as a result, the faller may land on an uneven surface. Forward falls are among the mostfrequent causes of fractures. Previous investigations concentrated on the evaluation of impact forces
acting on the hand/wrist on even terrains; however, further studies are necessary to evaluate the impact
force during forward falls on uneven surfaces, which may occur frequently in daily activities. This study
investigated the distal/proximal hand impact force during forward falls on even/uneven terrain. A seriesof fall experiments in which the distal and proximal areas of the hand contacted the groundsimultaneously (even surface) or at different times (uneven surface) was conducted. The results showedthat the magnitude of the peak impact forces acting on the distal and proximal areas are strongly
associated with the terrain shape and the contact timing. Although in all experiments, a significant portionof the impact force was exerted on the proximal area of the hand, the earlier distal-ground contact reduced
the peak proximal impact force significantly. The results of this study are beneficial for finding strategies
to reduce fall-related injuries and the design of protective gloves and wrist guards to satisfy fracture
prevention requirements.
Keywords—Forward fall; Distal and Proximal areas of the hand; Impact force; Uneven ground2

1. Introduction
Mechanical perturbation such as an external force may endanger human balance during gait [1].
Elevating, lowering, and skip motions have been identified as the most common recovery strategies tomaintain balance and avoid falls [2]. However, losing postural stability and failure to recover invariably
results in a fall incident, which is a common cause of unintentional injuries, particularly for the elderly,
owing to high risk factors [3]. Forward falls, one the most frequent type of falls [4], can result in upper
extremity injuries such as wrist fractures [5].
Various researchers have conducted experiments to reproduce less severe fall motions and investigated
the impact force and injuries during forward falls. For example, Chiu and Robinovitch [6] conducted freefall experiments and developed a mathematical model supported by experimental findings to identify the
impact force profile during forward falls. Their results showed that the impact force experienced by thehand is governed by an initial high magnitude peak (fmax1) occurring shortly after contact, followed by alower peak (fmax2). Moreover, they observed that reduction in surface stiffness attenuates the magnitude of
the primary peak impact force, but does not significantly affect the secondary peak [7]. However, the main
limitation of their study and other similar studies [8, 9] was the inability of their models to evaluate theeffect of elbow flexion on the impact force applied to the hand. DeGoede et al. [10] proposed a 3-DOF
model comprising a lumped mass and two arm segments moving on the sagittal plane, and investigated theeffect of initial elbow angle and impact velocity during forward falls.
Several researchers have focused on finding training programs to improve postural control [11-13] andthe human reaction after losing control [14]. Although the training programs showed promising results,
postural control can be different among people with different body factors [15], and always there is apossibility of fall. A falling person has less than 500 milliseconds to perform an appropriate fall strategy
prior to ground contact [16]. Initial elbow flexion and reducing the velocity of the hands relative to thetorso are strategies that can decrease the impact force during a forward fall [17, 18]. Further, elbow flexion
movement at the time of impact leads to a delayed and reduced impact force [19] and is a more effective
3

strategy than shoulder joint flexion [20]. Experimental results show that longitudinal rollover strategy [21]and internally rotated forearm are appropriate fall arrest strategies that reduce the risk of upper extremity
injuries, whereas an externally rotated forearm can increase the risk of injuries [22]. Whereas body rotationin the sagittal plane has negligible effect on the impact force, frontal plane rotation can lead to a reductionin the impact force applied to the trailing hand [23].
Aging also affects human postural fluctuations [24] and the impact force during falls. Fall incidents
occur frequently among the elderly [25] and may lead to injuries and fractures. The capacity for upper
extremity energy absorption among young women is twice that of older women [26]. The force applied toupper limb joints during forward falls and the associated fractures have attracted the attention of various
researchers. To identify the mechanical response of the distal radius under impact loading, humancadaveric radii are widely used and the risk of bone fractures estimated [27].
From a design perspective, the data associated with injuries are useful to develop compliant flooring,
airbags and wrist guards, which is applicable in both the daily life of the elderly and sports such as
snowboarding [28]. The impact force applied to the hip can be reduced using hip protection airbag [29, 30].
Evidence show that wrist guards can attenuate the impact force during forward falls [31]. The distribution
and magnitude of the force/pressure over the palm of the hand also provides several guidelines for making
more efficient handguards. Choi et al. [32] determined how pressure distribution over the palm of the handis associated with padding, the impact angle of the arm, the soft tissue foam over the palm, and body massindex.
Previous studies [33] have shown that outdoor falls are more frequent than indoor falls among healthy
and active older people. Of the outdoor falls, 73% occur because of environmental factors [34] such as
uneven or slippery terrains. Thus, the faller may land on an uneven surface; where one area of the hand
may contact the ground earlier than the other areas because of terrain irregularities. To the best of ourknowledge, all previous studies investigated the different aspects of the impact forces applied to the hands
under various circumstances only on even terrain.
4In this study, we investigated the impact force applied to two areas of the hand on even/uneven terrain.
We assumed the first null hypothesis that the magnitude of the peak impact forces exerted on the distal andproximal areas of the hand are the same. This hypothesis was defined to compare the peak impact forces on
distal and proximal areas separately, which is necessary for studying the impact force applied to the handon uneven surfaces. Moreover, this investigation provides an understanding about the portion of the impact
force applied to the proximal area that is the cause of ulna/radius fracture [35]. Secondly, we hypothesizedthat the shape of the surface (i.e., even or uneven terrain) does not affect the impact force profile applied tothe proximal and distal areas of the hand in all conditions. This hypothesis was designated to investigate towhat extent the shape of surface (i.e. three different conditions in this paper) can affect the peak impact
forces applied to proximal and distal areas of the hand. Both hypotheses and our results can provide useful
information for designing effective fall arresting strategies and protective devices.

2. Methods
2.1. Participants
Twelve healthy young male subjects, ranging in age from 20 to 38 years (25.5±5.5), participated in thisstudy. Their average height and weight were 173.4±5.7 cm and 65.9±11.5 kg, respectively. None of thesubjects had previously received training such as martial arts techniques, gymnastics, Jodo, or wrestling.
Moreover, they did not have any record of major medical or neurological illnesses such as epilepsy,
significant hand trauma, balance disorders, or falls. All participants signed a written informed consent form
prior to the experiments, and the experimental protocol was approved by the Institutional Review Board of
the University. All the experiments were conducted in accordance with the approved guidelines.

2.2. Experimental Protocol
A supporting harness was fitted and attached to each subject’s trunk. The participants were instructed to
fix their shanks on a soft surface and extend their knees to lean forward against the harness. The thighorientation was checked to ensure that it was set at 30º from the horizontal using a soft wedge. By pulling5the supporting harness connected to the trunk, the participants were elevated to reach the proper heightfrom the ground (Fig. 1(a)). The subjects were instructed to keep their elbows fully extended (i.e.,
outstretched arm). The arm angle was set at 15° from the vertical. Thus, at the moment of fall, eachparticipant's body posture matched that used in the experimental setup considered in studies in theliterature [6].
As in the previous studies, we asked the subjects to keep their hands parallel to the ground before theharness release. The experiments were designed to determine the impact forces on two parts of the hand on
uneven and even terrain. We call the headmost part of the hand the distal area, including the distal palmar
and fingers. The lower part starts from the middle of the proximal palmar crease, including the Thenar andHypothenar eminences (Fig. 1(b)). To test the null hypothesis, we conducted several fall experiments inwhich the distal and proximal areas of the hand contacted the surface simultaneously (even terrain) or atdifferent times (uneven terrain). The experiments were conducted based on three different scenarios:
Experiment 1: The proximal and distal areas contact the ground simultaneously. This experiment isrelated to forward falls on even terrain.
Experiment 2: The distal area contacts the ground followed by the proximal area of the hand. This
experiment is associated with forward falls on uneven terrain.
Experiment 3: The proximal area of the hand contacts the ground first, followed by the distal area. This
experiment is related to forward falls on uneven terrain.
In order to measure the proximal and distal hand impact forces, two force plates were installed undereach hand (i.e. in total, four separated force plates (US06-H5, Tech Gihan Co., Ltd., Japan)). After the
release of the harness, the participants fell on these force plates, which were fixed on the ground. To
conduct the experiments related to uneven terrains (Experiments 2 and 3), two force plates (i.e., one undereach hand) were mounted 1 cm higher or lower. For example, to perform the second experiment, the force
plates under the distal areas of the hands were installed 1 cm higher than the force plates under the6

proximal areas. The first experiment enabled us to measure the impact force on even terrain, separately forproximal and distal areas. It is obvious that the force plates were installed at the same height for the firstexperiment. Three fall heights were considered at h = 2, 5, and 8 cm. The height was measured and set as
the distance between the hand and the highest force plate. Each participant completed 18 trials in which
there were three experiments, repeated twice for each of the three fall heights.

Fig. 1 (a) The experimental setup used to evaluate impact forces during forward falls on outstretched arms at heights
of 2, 5, and 8 cm. (b) Two parts of the hand; distal and proximal areas. (c) Different types of experiments:
Experiment 1 is associated with falls on even terrain, where both distal and proximal areas of the hand contact the7ground simultaneously. Experiment 2 is related to falls on an uneven terrain, where the distal area of the handcontacts the ground followed by the proximal area. Experiment 3 is associated with falls on uneven terrain, where
the proximal area of the hand contacts the ground first, followed by the distal area.

To examine the first null hypothesis, an independent sample t-test was conducted to compare the meanvalues of the peak impact forces applied to the proximal and distal areas for various fall heights.
Subsequently, we performed one-way analysis of variance (ANOVA) to evaluate the effect of different
surface shapes (i.e., even and uneven terrain) on the peak impact forces at the distal and proximal areas(Table 1). Statistical analysis was conducted using SPSS Software (version 23; IBM Corporation, Armonk,
NY, US). A statistically significant value was considered at p < 0.05. Moreover, a Pearson productmoment correlation was used to determine if there is a significant relation between two parameters: 1.
Body mass and BMI, 2. The peak impact force.
Table 1. Experimental orders for ANOVA analysis
Experiment
numberShape of surface(Different terrains)
Experiment 1

Hand areas which wereconsidered in impact
force measurement
Proximal

1(Even terrain, h = 2, 5, 8 cm)

DistalExperiment 2(Uneven, distal area contacts the ground followed by theproximal area, h = 2, 5, 8 cm)
Experiment 3(Uneven, proximal area contacts the ground followed by
the distal area, h = 2, 5, 8 cm)

Proximal

2

3

DistalProximal
Distal

3. Results
Fig. 2 shows the average of the left and right hands’ impact forces for the fall heights of 2, 5, and 8 cm
on even terrain. The impact force profiles have similar trends for both areas of the hand, involving an
initial high magnitude peak (fmax1) occurring shortly after contact, followed by a lower peak (fmax2). For
both the proximal and distal areas, the first peak force has a significant growth rate affected by the fallheight; however, the second peak rise is low. All participants displayed increasing peak impact force8magnitude with increasing fall height: 194±33 N and 49±14 N for the proximal and distal areas at the 2 cm
height, 313±49 N and 72±20 N for the proximal and distal areas at the 5 cm height, and 392±58 N and
90±25 N for the proximal and distal areas at an 8 cm height (Table 2).
Table 2 The peak impact forces for different experimental conditions

Fall Height

2 cm
5 cm
8 cm

Peak Impact Force Magnitude (N)Experiment 2
Experiment 2(Uneven, distal area contacts(Uneven, proximal area contacts
followed by the proximal area)
followed by the distal area)

Area

Experiment 1(Even Terrain)

Proximal

194±33127±29218±47Distal

49±14

75±23

43±19

Proximal

313±49205±42334±56

Distal72±20

109±4359±28

Proximal392±58264±74415±63Distal90±25

136±5473±30

The results of Experiment 1 show that the distal area of the hand possesses a low proportion of the total
impact force during forward falls on even terrain where the distal and proximal areas of the hand contact
the ground simultaneously. There is a significant difference in the peak impact forces between the distaland proximal areas; thus, the first null hypothesis was rejected. On average, about 19% (p < 0.002) of thetotal peak impact force is applied to the distal area; the remainder is exerted against the proximal area ofthe hand.
Fig. 3 shows the average left and right-hand impact forces for the fall heights of 2, 5, and 8 cm on theuneven terrain where the distal area contacts the force plates prior to the proximal area. Whereas theproximal area impact force includes two peaks, the distal area impact force profile is governed by threepeaks. The first peak occurs approximately 6 ms after contact and the other two peaks occur at timings
close to the proximal area peaks. Both the proximal and distal area impact forces were significantly
affected by the fall height.

9

Fig. 2 Impact force profile applied to the proximal and distal areas of the hand during a fall on an even surface (i.e.,
both the proximal and distal areas of the hand contact the surface simultaneously) from heights of 2 cm, 5 cm, and
8 cm.

10

Fig. 3 Profile of the impact forces applied to the proximal and distal areas of the hand during a fall on an unevensurface, where the distal area of the hand contacts the surface followed by the proximal area from heights of 2 cm,
5 cm, and 8 cm.

11All subjects exhibited a significantly higher magnitude of peak impact forces by increasing the fallheight: 127±29 N and 75±23 N for the proximal and distal (i.e., second peak) areas at the 2 cm height,
205±42 N and 109±43 N for the proximal and distal (i.e., second peak) areas at the 5 cm height, and
264±74 N and 136±54 N for the proximal and distal (i.e., second peak) areas at the 8 cm height (Table 2).
The average peak impact force applied to the distal area was approximately 35% (p < 0.005) of the total
peak impact force. The magnitude of the first peak (i.e., extra peak compared to the proximal area force
profile) impact force applied to the distal area displayed an increasing trend associated with the fall height:
97±31 N at the 2 cm height, 122±29 N at the 5 cm height, and 138±35 N at the 8 cm height.
The average left and right-hand impact forces for the fall heights of 2, 5, and 8 cm on the uneven terrain
where the proximal area contacts the force plates prior to the distal area is shown in Fig. 4. The magnitudeof the peak impact forces applied to the distal area of the hand is the highest and the magnitude of the peakproximal area is the lowest among the three types of experiments: 218±47 N and 43±19 N for the proximaland distal areas at the 2 cm height, 334±56 N and 59±28 N for the proximal and distal areas at the 5 cm
height, and 415±63 N and 73±30 N for the proximal and distal areas at the 8 cm height (Table 2). The
impact force of the proximal area can be characterized by two peaks; however, the distal area second peakcan be difficult to recognize. On average, only 15% (p < 0.001) of the total peak impact force was applied
to the distal area. As in other experiments, the larger fall heights induce higher peak impact forces on both
the distal and proximal areas of the hand.
The secondary null hypothesis was also rejected following comparison of the distal and proximal
impact forces on different terrain shapes. The ANOVA analysis revealed that there was a significant effectof surface shape on the mean value of the peak impact force at the proximal (F (2,186) = 83.1, p < 0.0005)
and the distal (F (2,186) = 34.7, p < 0.0005) areas. Post hoc pairwise comparisons conducted using the
Tukey HSD test indicated that the mean of the peak impact force for Experiment 2 differed significantly
from that of Experiment 1 and Experiment 3. However, the average peak impact force in Experiment 1 did
not significantly differ from Experiment 3 at the proximal (p = 0.218) and the distal (p = 0.161) areas.

12The peak impact force applied to the proximal area for the earlier distal-ground contact is about 39% (p< 0.001) and 34% (p < 0.002) less than earlier proximal-contact and distal/proximal-ground contact,respectively.

4. Discussion
This study examined the role of surface shape on the impact force applied to the distal/proximal areasof the hand. The results obtained show that the proximal area peak impact force is significantly higher thanthat of the distal area for all conditions. Although a large portion of the impact force acts on the proximal
area of the hand, the magnitude of the exerted forces against the distal and proximal areas are strongly
dependent on the shape of the surface and the contact. In these experiments, we did not observe asignificant difference between the impact forces applied to the left and right hands during the bimanual
forward fall. Thus, the average left and right-hand impact forces were reported.
The experimental results show that in a fall on even terrain, only about one-fifth of the peak impact
force is applied to the distal area of the hand, the rest is exerted on the proximal area. For falls on an
uneven surface, the ratio between the distal and proximal forces is significantly affected by the shape of thesurface. In cases of earlier distal-ground contact, the applied force on the proximal area can be substantiallyreduced. Conversely, if the proximal area contacts the ground prior to the distal area, the peak impact force
against the proximal area may increase slightly, which is not significant.
The proximal impact forces had similar trends in all the experiments, both on even and uneven terrain,including two peaks. The magnitude of the peak impact forces in Experiments 1 and 3 are close. In
contrast, the peak impact force in Experiment 2 occurs with a longer delay and is significantly lower thanthat of the two other experiments.

13

Fig. 4 Profile of the impact forces applied to the proximal and distal areas of the hand during a fall on an unevensurface, where the proximal area of the hand contacts the surface followed by the distal area from heights of 2 cm,
5 cm, and 8 cm.

14Consequently, a significant portion of the impact force is exerted on the proximal area when it contacts
the ground prior to/with the distal area. This factor can increase the radius/ulna fracture risk [35].
Conversely, in cases where the distal area contacts the ground followed by the proximal area, the proximal
peak impact force and the fracture risk are reduced. Early proximal-ground contact can be similar to thecondition in which a person falls while clenching an object in their hand. The object may be placed
between the ground and the proximal area of the hand. This condition may lead to a hamate fracture [36].
Experiments 1 and 3 showed similar patterns for the distal area impact forces comprising two peaks.
However, the distal force profile in Experiment 2 has a different arrangement, in which three peaks can berecognized. The difference is due to early contact between the distal area and the surface. This causes an
early peak in distal area impact force profile, and then similar to experiments 1 and 3, two other peaks
occur afterwards; however, in this case they are delayed (i.e., in total three peaks can be observed).
Moreover, the distal early contact causes a reduction in hand acceleration, and consequently the impact
force applied to the proximal area reduces. The peak distal impact force of Experiment 2 is significantly
higher than that of the other two experiments. This fact shows that the early distal-ground contact leads to ahigher portion of the peak impact force on the distal area of the hand and, consequently, reduction in theimpact force applied to the proximal area.
Although it may seem beneficial to for the distal part to make contact prior to the proximal area in orderto decrease the impact force acting on the proximal area, more studies are necessary to investigate possible
injuries that may result from a large impact force on the distal area. The common design of padded gloves
is predominantly targeted at covering the proximal area to reduce fracture risk. Such devices should bedesigned based on the impact force profiles for terrains with different shapes. The outcomes of this study
can be useful for researchers investigating the design of such protective equipment to ensure their efficacy.
A Pearson product-moment correlation was performed for forward falls to assess the relationshipbetween the participants' body mass, BMI and the peak impact force in experiments 1, 2 and 3. The
correlation analysis showed that there were very strong, positive correlations between the body mass and15the peak impact force for both proximal and distal areas, which were statistically significant (p ≤ 0.01);
however, BMI did not have any significant effect on the magnitude of the peak impact force (p > 0.05).
Our findings are consistent with the previous studies [6].
The populations with the highest risk for a distal radius fracture are children and older adults,
particularly older women. This limited many researchers to conduct fall experiments only with healthy
young males [17, 18]. This is also a limitation of our study to use only young male adults for our
experiments. As a future plan, we are going to design experiments, which are safe enough to involveelderly people, and compare the outcome with the current study.

5. Conclusion
During a forward fall on an uneven surface, one area of the hand may contact the ground earlier/later
than the other because of ground irregularities. We designed an experiment to investigate the impact force
in such fall conditions, which may occur frequently in daily activities. We sought to determine the impact
force on two areas of the hand, which we called the distal (distal palmer and fingers) and proximal (Thenarand Hypothenar eminence). Two conditions were considered for falls on uneven terrain—the proximal areaof the hand contacting the ground before or after the distal area. However, falls on even terrain were
defined as a condition where both the distal and proximal areas contacted the ground simultaneously.
The results obtained show the proximal impact force as having two peaks for all conditions. However,the surface shape and the falling height may affect the magnitude of the peak impact forces. Morespecifically, the earlier distal-ground contact reduces the impact force exerted on the proximal area of thehand. The difference between the proximal peak impact forces in the case of earlier proximal-groundcontact compared with simultaneous proximal- and distal-ground contact can be ignored. The lower
proximal peak impact force is beneficial to reduce the risk of distal radius/ulna and scaphoid fractures.
The distal impact force in the case of earlier distal-ground contact has an extra peak before contact by
the proximal area, in contrast to two other conditions. This peak occurs in a very short time after the16

contact. In this condition, the main distal peak impact force is also higher than the other conditions whichleads to reduced proximal impact force. These results are advantageous in finding new strategies to reduce
the risk of injuries and provides useful information about the distribution of the impact force that isbeneficial for designing of protective gloves and wrist guards to satisfy fracture prevention requirements.
Wrist fractures may occur in both forward and backward falls. Thus, future studies will examine how thefall direction influences the impact force on uneven terrain.

References
1. Kim, J., Kim, C., Lee, J., Kwon, Y., Eom, G., Tak, G., & Hong, J. (2009). Human postural control
against external force perturbation applied to the high-back. International Journal of Precision
Engineering and Manufacturing, 10(4), 147-151.
2. Mitsuoka, K., Akiyama, Y., Yamada, Y., & Okamoto. S. (2015). Analysis of Skip Motion as a Recovery
Strategy after an Induced Trip. In Proceedings of 2015 IEEE International Conference on Systems, Man,
and Cybernetics. doi:10.1109/smc.2015.167.
3. Pavol, M.J., Owings, T.M., Foley, K.T., & Grabiner, M.D. (2001). Mechanisms Leading to a Fall Froman Induced Trip in Healthy Older Adults. The Journals of Gerontology: Series A, 56(7):428-437.
4. Stevens, J.A., Mahoney, J.E., & Ehrenreich, H. (2014) Circumstances and outcomes of falls among highrisk community-dwelling older adults. Injury Epidemiology, 1(5):1-9, doi: 10.1186/2197-1714-1-5.
5. Crenshaw, J.R., Bernhardt, K.A., Achenbach, S.J., Atkinson, E.J., Khosla, S., Kaufman, K.R., et al.
(2017). The circumstances, orientations, and impact locations of falls in community-dwelling older
women. Archives of Gerontology and Geriatrics, 73:240–247.
6. Chiu, J., & Robinovitch, S.N. (1998). Prediction of upper extremity impact forces during falls on theoutstretched hand. Journal of Biomechanics, 31(12):1169-1176.

17

7. Robinovitch, S.N., & Chiu, J. (1998). Surface stiffness affects impact force during a fall on theoutstretched hand. Journal of Orthopaedic Research, 16(3):309-313.
8. Kim, K.J., & Ashton-Miller, J.A. (2009). Segmental dynamics of forward fall arrests: A system
identification approach. Clinical Biomechanics, 24(4):348-54.
9. Rajaei, N., Abdolshah, S., Akiyama, Y., Yamada, Y., & Okamoto, S. (2018). Rigid material on top of acompliant 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), 273-277.
10. DeGoede, K.M., Ashton-Miller, J.A., Schultz, A.B., & Alexander, N.B. (2002). Biomechanical Factors
Affecting the Peak Hand Reaction Force During the Bimanual Arrest of a Moving Mass. Journal of
Biomechanical Engineering, 124(1):107-112.
11. Yu, C.H., Piao, Y.J., Kim, K., & Kwon, T.K. (2014). The effects of an 8-weeks training on posturalcontrol for the elderly. International journal of precision engineering and manufacturing, 15(1), 161-168.
12. Jung, H., Kim, H.J., Kim, B.R., & Lim, D. (2017). Alterations of human responses by varying dynamic
rotational perturbations on balance training equipment. International Journal of Precision Engineering andManufacturing, 18(9), 1269-1274.
13. Kang, S.R., Yu, C.H., Moon, D.A., & Kwon, T.K. (2014). Effect of long time whole-body vibration
training on muscle function and postural balance. International journal of precision engineering andmanufacturing, 15(8), 1681-1688.
14. Abdolshah, S., Akiyama, Y., Mitsuoka, K., Yamada, Y., & Okamoto. S. (2017). Analysis of upper
extremity motion during trip-induced falls. In Proceedings of 26th IEEE International Symposium on
Robot and Human Interactive Communication (RO-MAN). doi:10.1109/roman.2017.8172500.
15. Kim, J., Kwon, Y., Chung, H.Y., Kim, C.S., Eom, G.M., Jun, J.H., & Park, B.K. (2012). Relationshipbetween body factors and postural sway during natural standing. International Journal of Precision
Engineering and Manufacturing, 13(6), 963-968.
1816. Degoede, K.M., Ashton-Miller, J.A., Liao, J.M., & Alexander, N.B. (2001). How Quickly Can Healthy
Adults Move Their Hands to Intercept an Approaching Object? Age and Gender Effects. Journals ofGerontology Series A: Biological Sciences and Medical Sciences, 56(9):M584-588.
17. Degoede, K.M., & Ashton-Miller, J. (2002). Fall arrest strategy affects peak hand impact force in a
forward fall. Journal of Biomechanics, 35(6):843–848.
18. Lo, J., Mccabe, G., Degoede, K., Okuizumi, H., & Ashton-Miller, J. (2003). On reducing hand impact
force in forward falls: results of a brief intervention in young males. Clinical Biomechanics, 18(8):730–
736.
19. Chou, P.-H., Chou, Y.-L., Lin, C.-J., Su, F.-C., Lou, S.-Z. C., Lin, -F., et al. (2001). Effect of elbow
flexion on upper extremity impact forces during a fall. Clinical Biomechanics, 16(10):888–894.
20. Chou, P.-H., Chen, H.-C., Hsu, H.-H., Huang, Y.-P., Wu, T.-C., & Chou. Y.-L. (2012). Effect of upper
extremity impact strategy on energy distribution between elbow joint and shoulder joint in forward
falls. Journal of Medical and Biological Engineering, 32(3): 175-180.
21. Abdolshah, S., Rajaei, N., Akiyama, Y., Yamada, Y., & Okamoto, S. (2018). Longitudinal Rollover
Strategy as Effective Intervention to Reduce Wrist Injuries During Forward Fall. IEEE Robotics andAutomation Letters, 3(4), 4187-4192.
22. Hsu, H.H., Chou, Y.L., Lou, S.-Z., Huang, M.J., & Chou, P.P.H. (2011). Effect of forearm axiallyrotated posture on shoulder load and shoulder abduction / flexion angles in one-armed arrest of forward
falls. Clinical Biomechanics, 26(3):245–249.
23. Burkhart, T.A., Brydges, E., Stefanczyk, J., & Andrews, D.M. (2017). The effect of asymmetrical bodyorientation during simulated forward falls on the distal upper extremity impact response of healthypeople. Journal of Electromyography and Kinesiology, 33:48–56.

1924. Ramdani, S., Tallon, G., Bernard, P.L., & Blain. H. (2013). Recurrence Quantification Analysis of
Human

PosturalFluctuations

in

Older

FallersandNon-fallers. Annals

ofBiomedical

Engineering, 41(8):1713–1725.
25. Hahn, M.E., and Chou, L.S. (2005). A model for detecting balance impairment and estimating falls riskin the elderly. Annals of biomedical engineering, 33(6):811-820.
26. Sran, M.M., Stotz, P.J., Normandin, S.C., & Robinovitch, S.N. (2009). Age Differences in Energy
Absorption in the Upper Extremity During a Descent Movement: Implications for Arresting a
Fall. Journals of Gerontology Series A: Biomedical Sciences and Medical Sciences, 65(3):312–317.
27. Eckstein, F., Kuhn, V., & Lochmüller. E.-M. (2004). Strength Prediction of the Distal Radius by Bone
Densitometry—Evaluation Using Biomechanical Tests. Annals of Biomedical Engineering, 32(3):487–
503.
28. Michel, F.I., Schmitt, K.-U., Greenwald, R.M., Russell, K., Simpson, F.I., Schulz, D., & Langran, M.
(2013). White Paper: functionality and efficacy of wrist protectors in snowboarding—towards a
harmonized international standard. Sports Engineering. 16(4):197–210.
29. Jeong, Y., Ahn, S., Kim, J., Kim, S., Koo, B., Ryu, J., & Kim, Y. (2019). Impact Attenuation of theSoft Pads and the Wearable Airbag for the Hip Protection in the Elderly. International Journal of Precision
Engineering and Manufacturing, 20(2), 273-283.
30. Ahn, S., Choi, D., Kim, J., Kim, S., Jeong, Y., Jo, M., & Kim, Y. (2018). Optimization of a pre-impact
fall detection algorithm and development of hip protection airbag system. Sensors and Materials, 30(8),1743-1752.
31. Burkhart, T.A., & Andrews, D.M. (2010). The Effectiveness of Wrist Guards for Reducing Wrist and
Elbow Accelerations Resulting from Simulated Forward Falls. Journal of Applied Biomechanics, 26:281–
289.

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32. Choi, W., & Robinovitch, S.N. (2011). Pressure distribution over the palm region during forward falls
on the outstretched hands. Journal of Biomechanics, 44(3):532–539.
33. Kelsey, J.L., Procter-Gray, E., Hannan, M.T., & Li, W. (2012). Heterogeneity of falls among older
adults: implications for public health prevention. American Journal of Public Health, 102(11): 2149–2156.
34. Li, W., Keegan, T.H., Sternfeld, B., Sidney, S., Quesenberry, C.P., & Kelsey, J.L. (2006). Outdoor
Falls Among Middle-Aged and Older Adults: A Neglected Public Health Problem. American Journal of
Public Health, 96(7):1192–1200.
35. Frykman, G. (1967). Fracture of the Distal Radius Including Sequelae-Shoulder–Handfinger
Syndrome, Disturbance in the Distal Radio-Ulnar Joint and Impairment of Nerve Function: A Clinical andExperimental Study. Acta Orthopaedica Scandinavica, 38:1–61.
36. Glaudemans, A.W., Dierckx, R.A., Gielen, J.L., & Zwerver, J.H. (2015). Nuclear Medicine andRadiologic Imaging in Sports Injuries. Springer.

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