CONFIDENTIAL. Limited circulation. For review only.

A New 3D Motion and Force Measurement System
for Sport Climbing
Hitomi Iguma1 , Akihiro Kawamura2 and Ryo Kurazume2
Abstract— Sport climbing is a form of rock climbing andhas currently increased in popularity. This kind of climbing
is played all over the world and becomes an Olympic sport.
Motion measurement and analysis system have been required
to improve the performance of climbers and instruct themproperly. Several systems using motion capture have been
proposed to analyze the movement of climbers so far. However,the conventional systems are not sufficient to describe climbing
motions since the forces on holds have not been taken into
account. This paper proposes a new 3D motion and force
measurement system for sport climbing that can obtain theinformation on human motion and forces on holds simultaneously. The motion and force data are synchronized. Then, we
can measure and analyze climbing motions geometrically anddynamically by using the proposed system. The performanceof the proposed system is qualitatively verified by experiments.

I. INTRODUCTION
Sport climbing is one of the sports increasing attention
all over the world. This sport has a short history as the first
official competition on a world scale is the World Cup in
1980. However, the climber population and the number ofathletic facilities have already increased enough to become
an Olympic sport in 2020. Therefore, motion measurement
and analysis system have been required to improve theperformance of players and instruct them properly.
In sport climbing, players and competitors climb 3D
shaped walls with various holds. The movement of sport
climbing is quite complex compared to other sports due tomulti-contact and to the diversity of the shapes of walls andholds. Several researches on motion analysis of climbing
have been presented so far [1–6]. Sibella et al. analyzed
the climbing motion for common patterns and differences
in a group of recreational climbers [1]. The motion ofclimbers is recorded through motion capture based on passive
markers. The movements of the subjects are evaluated byusing some parameters derived from the center of mass(COM) trajectory. White et al. analyzed the time allocationof elite climbers in competitions [2]. In their research, timemotion analyses are performed by using video footages.
Reveret et al. proposed a 3D motion analysis method forspeed climbing [3]. They approximated the center of massby a marker attached to subject’s harness, close to the middleof the pelvic ilium bones. By recording this marker with two
1 Hitomi Iguma is with Graduate School of Information Science andElectrical Engineering, Kyushu University, Fukuoka, JAPAN iguma@irvs.ait.kyushu-u.ac.jp
2 Akihiro Kawamura and Ryo Kurazume are with Faculty of Information
Science and Electrical Engineering, Kyushu University, Fukuoka, JAPAN

kawamura, kurazume@ait.kyushu-u.ac.jp

drone cameras, they analyzed the COM trajectory. Watts et
al. measured a geometric entropy derived from the center ofmass in lead and top rope rock climbing [4]. They manually
digitized the back center of subject’s waist harness from thevideo images and interpreted this position as the center ofmass. Cha et al. measured the postures and movements insport climbing using Microsoft Kinect, and calculated thelimb velocity and joint angles during climbing [5]. They
generated realistic 3D character animation by processing the
motion capture data. Asakawa et al. analyzed the movement
characteristics of experienced climbers in comparison with
beginners [6]. They attached reflective markers to the body ofsubjects and recorded the motion using two digital cameras.
They showed several characteristics using the data for joint
angles and trajectories of the center of gravity.
Most of the previous researches on motion analysis ofclimbing have utilized the motion capturing method so far.
The posture is certainly an important factor. However, thephysical interaction between climbing walls and human bodies has not been taken into account. In order to analyze thebody motion of climbers deeply, force information on multicontact is indispensable since climbers always have multicontact with walls and holds which have complex shapes.
The force information shows the difference in the physicalstrength of climbers including core and grip strengths.
In terms of force sensing, several researches on force
sensing on holds have been shown so far [7–9]. Fuss etal. and Lechner et al. developed force sensing systems ofa hold. Fuss et al. measured and analyzed the mechanicalparameters of climbing by instrumenting two 3D force transducers with a hold, and visualized the force vector diagrams[7]. In addition, they confirmed that experienced climbers
have smaller contact force and shorter the contact time than
beginners. Lechner et al. developed a three-dimensional force
measurement system [8]. In their system, they measured theforces which the athletes exerted on the climbing hold byusing three orthogonally mounted platform load cells and awireless data acquisition system. On the other hand, Quaine
et al. measured three-dimensional forces applied to holds
by using four holds equipped with strain gages [9]. They
analyzed the arrangement of forces on holds when subjects
release their right foot from the hold. Most of the researches
about force sensing on climbing holds have focused on only
force information.
However, in order to more precisely analyze the physicalstrength of the entire body, we have to consider both motion
and force information simultaneously. In addition, the force
sensing systems referred above are not able to be applied

Manuscript 265 submitted to 2020 IEEE/SICE International Symposium
on System Integration (SII). Received August 30, 2019.

CONFIDENTIAL. Limited circulation. For review only.

for various shaped holds. Therefore, the main contributionsof this paper are 1. Simultaneous measurement of motion
and force information about sport climbing, 2. Adaptation
capability for the diversity of the shapes of holds and 3.
Modification of arrangement of markers on a model for
motion capturing system.
This paper proposes a new motion and force measurement system for sport climbing. Both motion and force
behaviors are measured simultaneously. Then, the system canprovide more detailed information on the motion in sport
climbing. For example, inner forces, contact point on holds
and distribution of forces of multi-contact. The motion ofclimbing is measured by an optical tracking system usingreflective markers. Joint angles and the center of mass arecalculated accurately. In order to measure the force on theholds given by hands and feet, a new force measurement
system is developed. This system consists of a 6-axis force
sensor, several jigs, and a 3D printed protection cover. It is
installed between each hold and walls. The motion and force
information are synchronized accurately. In order to confirm
the performance of the proposed system, several experiments
are conducted in the climbing wall built in our laboratory andan actual climbing gym.

Fig. 1.

Arrangement of the markers

II. MOTION AND FORCE MEASUREMENTSYSTEM
This section introduces the proposed system that measures
motion and force during sport climbing. The motion information is observed by a motion tracking system using opticalmarkers. The model for the motion capture is modified toapply for sport climbing since the occlusions due to holds,
walls and human bodies are caused. The force informationof multi-contact on holds are sensed by 6-axis force sensors.
A force sensing system is proposed here that can measure
the force and moment on holds and is applicable for various
holds. The motion and force information is synchronized bytime stamps.
A. Three Dimensional Motion Capture System
A motion capture system using optical markers is utilized
in this research. The cameras of the system are composedof six Vero v1.3 and one Bonita3 (Vicon). The software to
analyze the data gathered by the cameras is Vicon Nexus
2.7.1. In this software, the detail of the motion such as
joint angles and center of mass are automatically calculated
by using a model named Plug-In-Gait. This model provides
detailed whole body motion. However, in climbing situations,the occlusion due to holds, wall and human body occurs.
Thereby, we modify the Plug-In-Gait model to apply for
climbers.
The Plug-In-Gait model needs 39 reflective markers on the
body of subjects. The arrangement of the markers is shown in
Figure 1. Among them, the markers attached on the throat
and the solar plexus are especially difficult to be detectedby cameras. The recognition rates of the two markers are
15 [%] and 27 [%] respectively. Therefore, we made an
extra attachment that has four markers to complement theFig. 2.

Attachment to complement the markers on front bodyFig. 3.

Existing and added markers on shoulders

missing markers. Figure 2 shows the attachment. After thecompletion using the attachment, the recognition ratios ofmarkers are improved up to 78 [%] and 79 [%] respectively.
In addition, two markers are added on the shoulders as shownin Figure 3 since the existing marker is also difficult to be
detected when climbers raise their arms. The recognition
ratios of the markers on the left and right shoulders are
improved from 31 [%] and 35 [%] to 88 [%] and 94 [%].
B. Climbing Hold Force Measurement System
In sport climbing, climbers’ movement is based on using
their hands and feet. Then, they have four or three pointsof contact with holds. The force measurement of the forces
applied for climbing holds is important to analyze the movement deeply. Additionally, the force and moment informationfrom multiple force sensors are expected to estimate the innerforces and detailed contact points on holds. This system is

Manuscript 265 submitted to 2020 IEEE/SICE International Symposium
on System Integration (SII). Received August 30, 2019.

CONFIDENTIAL. Limited circulation. For review only.

Fig. 4.

Process of the assembly

Fig. 5.

Protection coverFig. 8.

Snapshots of the motion

III. EXPERIMENTS
This section shows preliminary experiments using the wall
built in our laboratory and experiments in an actual climbing
gym. Firstly, it is qualitatively confirmed that the proposedsystem can measure the motion and force simultaneously
in the preliminary experiments. Next, in an actual climbing gym, the experiments using beginners and experienced
climbers in order to verify the performance of the proposedsystem and compare their performances.
A. Preliminary Experiments in a Laboratory
Fig. 6.

Fig. 7.

Climbing wall

Arrangement of cameras

designed to use various shaped holds and installed between
holds and climbing walls. This system consists of a 6axis force sensor(Leptrino Co. Ltd.), jigs and a 3D printed
protection cover. Figure 4 shows the process of the assembly.
Figure 5 shows a protection cover. This black cover is notmounted on the sensor and prevents the force sensor fromgrasping and being stepped on. The surface inclination of
the cover is designed not to be grasped and stepped on. By
using this system on multiple holds, all the force information
for multi-contact is acquired.

This preliminary experiment is conducted to confirm theperformance of the proposed system. The climbing verticalwall built in our laboratory is shown in Fig. 6. The height
and width of the wall are 2.8 [m] and 1.4 [m] respectively.
The number of the force sensing system installed into thewall is five. Seven cameras of the motion capture system
are arranged around the wall as shown in Fig. 7. Figure
8 shows the snapshots of the climbing motion and stick
pictures generated by the software Nexus provided by Vicon.
From this figure, it is confirmed that the climbing motionof the entire body of the subject is measured properly byusing the modified Plug-In-Gait model. The force and motion
information are synchronized by using time-stamps. In order
to confirm the synchronization between motion and force
information, the sum of all forces applied to the subject’s
body using each information. The sum calculated using force
information F force is expressed as
F force =

5
X

F i,

(1)

i=1

where F i is the force obtained from the ith sensing system.
On the other hand, the sum of the forces calculated using
motion information is given as
F motion = M (a − g) ,Manuscript 265 submitted to 2020 IEEE/SICE International Symposium
on System Integration (SII). Received August 30, 2019.

(2)

CONFIDENTIAL. Limited circulation. For review only.

Fig. 9. Transient responses of force from motion capturing F motion andforce from force sensors F force

Fig. 11.

Wall used in an experimentFig. 12.

Experimental environment

and F force in z axis up to 2.0 [s] is caused by the contactof the left foot on the ground shown in Fig. 8.
B. Motion and Force Analysis of Beginners and Experienced
Climbers

Fig. 10.

Trajectories of COM

where M is the weight of the subject, a is the acceleration
vector of COM of the body calculated by the software
Nexus and g represents the gravitational vector. These sumof forces are shown in Fig. 9. From these figures, it is shownthat the synchronization technique using time stamps works
appropriately. In addition, This result also shows the good
performance of the force sensing system since F motion and
F force are synchronized. The deviation between F motion

In this subsection, several experiments in an actual climbing gym are conducted. Figures 11 and 12 show the wall usedin this experiment and the whole experimental environment.
As shown in these figures, seven cameras for motion capturing and five force sensing systems are installed. The subjectsof this experiment are a beginner who has experienced sport
climbing several times and an experienced climber who
represented a prefecture in Japan. They climbed the wall
several times while changing the hold types. A part of theexperiments is introduced in this paper. Figure 13 shows thesnapshots of the motions of the subjects. This type of motion
is high steps. In this motion, the subjects get their left footup on to the hold mounted on sensorA and shift their COM
above the hold. They can reach to the top hold then.
Figure 14 shows the trajectories of COM, and the position of the hold mounted on SensorA. As shown fromthe trajectory of COM in the horizontal x axis in Fig.
14, the experienced climber shifts his COM smoothly in aquick motion compared with the beginner. Additionally, theManuscript 265 submitted to 2020 IEEE/SICE International Symposium
on System Integration (SII). Received August 30, 2019.

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Fig. 14.

Trajectories of COM

skills of subjects.
IV. CONCLUSION

Fig. 13.

Snapshots of movements

distance to the left of the experienced climber is bigger thanthe beginner. The final position of the COM is important toquantify their climbing skill since it is difficult for beginners
to step onto such thin and tiny holds. Figure 15 shows thepercentage of the force detected at the sensorA to subjects’
weight. From the z values in Fig. 15, it is confirmed that theexperienced climber shifts his weight onto the hold up to 93[%]. In contrast, the beginner climber shifts his weight up to
73 [%]. This result supports the result from the trajectories of
COM in Fig. 14. From these results, we finally confirmed thatthe proposed system performs well enough to measure themotion and force information and to quantify the climbing

In this paper, we developed the new 3D motion andforce measurement system for sport climbing. By using
this system, the motion and force on the climbing holds
during sport climbing are measured simultaneously. The
arrangement of reflective markers on the model for motion
capture was modified to apply for sport climbing. Moreover,the climbing hold force measurement system which applies
to various shaped holds were proposed. The performance ofthe system and the synchronization between motion and force
data were confirmed by several experiments: preliminary
experiments in our laboratory and experiments in an actual
climbing gym. The experimental results also showed that the
climbing skills are quantified by using the proposed system.
In future works, it is necessary to increase the number ofsubjects and analyze their motion and force data. Then, we
will suggest the characteristics of movements of experienced
climber compared with beginners. Additionally, an intuitive interface system to provide feedback about climbers’
movement to improve their performance and instruct themproperly. Furthermore, the variety of the analysis object will

Manuscript 265 submitted to 2020 IEEE/SICE International Symposium
on System Integration (SII). Received August 30, 2019.

CONFIDENTIAL. Limited circulation. For review only.

[7] FK. Fuss and G. Niegl, “Instrumented Climbing Holds and Performance Analysis in Sport Climbing”, Sports Technology, No.6, pp.301313, 2008.
[8] B. Lechner, I. Filzwieser, M. Lieschnegg and P. Sammer, “A Climbing
Hold With an Integrated Three Dimensional Force Measurement andWireless Data Acquisition”, International Journal on Smart Sensing
and Intelligent Systems, Vol.6, No.5, pp.2296-2307, 2013.
[9] F. Quaine and L. Martin, “A biomechanical study of equilibrium insport rock climbing”, Gait&Posture, Vol.10, pp.233-239, 1999.

Fig. 15.

Percentage of the force detected in sensorA to subject’s weight.

be increased such as inner force generated between contacts,
body strength, contact points on holds.
ACKNOWLEDGEMENTS
This work was supported by JSPS KAKENHI Grant
Number JP18K17824.
R EFERENCES[1] F. Sibella, I. Frosio, F. Schena and NA. Borghese, “3D analysis of the
body center of mass in rock climbing”, Human Movement Science,
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[2] D. White and P. Olsen, “A time motion analysis of bouldering stylecompetitive rock climbing”, Journal of Strength and Conditioning
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[3] L. Reveret, S. Chapelle, F. Quaine and P. Legreneur, “3D MOTIONANALYSIS OF SPEED CLIMBING PERFORMANCE”, 4th International Rock Climbing Research Congress, 2018, Chamonix, France.
[4] PB. Wattts, SN. Drum, MA. Kilgas and KC. Phillips, “Geometric
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[5] K. Cha, E. Lee, M. Heo, K. Shin, J. Son and D. Kim, “Analysisof climbing posture and movements in sport climbing for realistic 3D
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Manuscript 265 submitted to 2020 IEEE/SICE International Symposium
on System Integration (SII). Received August 30, 2019.