Ankle-Foot Prosthesis for the Modern Alpinist – Overcoming Challenges in

Rock Climbing.
P Surya Darshini - 4NI22ME061
Noothana A Y - 4NI22ME060
4th Semester B Section
Mechanical Engineering, NIE

1. Abstract
Rock climbing demands significant physical endurance, powerful muscles, and precise use of
foot grips and handholds. For alpinists with lower limb amputations, these challenges are
compounded by the need to adapt to the loss of a limb. Current prosthetic technologies, while
advanced for everyday mobility, fall short for rock climbing. This paper explores the
development and potential of Electromyographically (EMG) Controlled 2-Degree of Freedom
(DOF) Robotic Ankle-Foot Prosthesis designed for rock climbing, aiming to enhance
performance and quality of life for amputees. It examines the anatomical and biomechanical
requirements of the ankle and foot, essential for designing effective prostheses that support body
weight, enable movement, and provide balance. The paper reviews advancements in powered
and adaptive prosthetic designs, highlighting their potential to improve mobility, stability, and
adaptability on complex terrains. A biomechanical assessment compares robotic and passive
prostheses, showing that robotic versions increase the range of ankle and subtalar positions,
reduce maximum knee and hip flexion angles, and offer intuitive control and comfort.
Addressing the specific needs of alpinists, specialized prostheses can enhance climbing
performance, promote independence, and boost self-esteem among climbers with limb loss,
contributing to more effective prosthetic solutions for rock climbing.
Keywords- Rock climbing, Biomechanics, Quasi passive devices, lower limb amputation.

2. Introduction
Rock climbing is a challenging and dangerous activity that involves ascending vertical cliffs,
often balancing on narrow ledges and gripping precarious holds. The difficulty of the climb,
rather than its height, is the primary challenge, requiring physical endurance, powerful leg and
arm muscles, and efficient use of foot grips and handholds [2]. For alpinists with lower limb

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amputations, these challenges are compounded by the need to adapt to the loss of a limb.
Today’s commercially available lower extremity prosthesis centers mostly on the creation and
operation of tools that enhance mobility and function during everyday tasks like walking on level
ground and negotiating stairs and ramps. With the use of cutting-edge robotic prostheses,
individuals who have lost a lower limb may now walk on level ground and mimic the gait
patterns of others who still have their biological limbs intact [1] [3]. Nevertheless, these
prostheses lack functionality necessary to fully restore climbing function. Existing prosthetic
devices are primarily designed for everyday mobility tasks and are not optimized for the unique
demands of rock climbing. These limitations include insufficient foot grip, inadequate support on
uneven surfaces, and the lack of necessary flexibility and durability to withstand the rigorous
conditions of rock climbing [2]. Therefore, the development of specialized ankle-foot prostheses
for rock climbing is crucial, as it opens up new possibilities for amputees to engage in this
physically and mentally demanding sport [1]. By addressing the specific needs of alpinists, these
prosthetics can enhance not only their climbing performance but also their overall quality of life,
fostering independence and boosting self-esteem [2]. Recent advancements in prosthetic
technology, such as the development of powered ankle-foot prostheses and adaptive designs,
show promise in overcoming these challenges. These innovations aim to provide greater
mobility, stability, and adaptability, which are essential for navigating complex climbing terrains
[1] [2] [3].
This study aims to explore the current state of ankle-foot prosthesis technology, identify the
specific needs and challenges faced by alpinists with lower limb amputations, and evaluate the
potential of new prosthetic designs to enhance climbing performance. The ultimate goal is to
contribute to the development of more effective prosthetic solutions tailored for rock climbing.

2.1. Anatomical Considerations

The human ankle and foot form a complex structure that supports body weight, enables
movement, and provides balance. Ankle-foot prostheses must mimic the complex anatomy and
biomechanics of the human ankle and foot to be effective, particularly for demanding activities
like rock climbing that demand high precision and flexibility. This section explores the essential
anatomical structures and biomechanical functions that need to be replicated or approximated in
prosthetic design [4] [5] [6].

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2.1.1. Human Ankle and Foot Anatomy
The ankle joint, comprising the tibia and fibula of the lower leg along with the talus above the
calcaneus, forms a critical structure for ankle-foot prostheses. Supporting these are the tarsal
bones—including the calcaneus, talus, navicular, cuboid, and three cuneiform bones—which
provide foundational stability. Further down, the metatarsal bones contribute to arch support and
weight distribution, crucial for mobility and balance. Finally, the phalanges of the toes facilitate
propulsion during walking and climbing, highlighting their importance in prosthetic design for
replicating natural foot function and movement dynamics (Fig.1) [4] [5] [11].

Fig. 1.Foot Bones Labelled Diagram [4].

(Fig.2) Ankle movement in ankle-foot prostheses is predominantly driven by powerful lower leg
muscles whose tendons pass through the ankle to the foot, crucial for activities like walking,
running, and jumping. Key muscles include the peroneals (peroneus longus and peroneus brevis)
on the outer ankle, aiding ankle flexion and outward movement, and the calf muscles
(gastrocnemius and soleus) which connect to the calcaneus via the Achilles tendon, facilitating

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ankle extension. Additionally, the posterior tibialis muscle supports the foot arch and assists in
inward rotation, while the anterior tibialis muscle lifts the ankle. Understanding these muscle
functions is essential for optimizing prosthetic design to replicate natural ankle biomechanics
effectively (Fig.2) [5] [6].

(Fig.3) In prosthetic design, understanding the neural and sensory components of the lower limb
is crucial. Sensory nerves in the foot, such as the proper and common plantar digital nerves,
medial and lateral plantar nerves, and the tibial nerve, play essential roles in transmitting
information for balance and coordination [7]. These nerves are integral to proprioception,
enabling precise movements and stability during activities like walking and climbing.
Replicating this sensory feedback in prosthetics is challenging, as current technologies struggle
to provide the real-time feedback necessary for adapting to varied terrains. Innovations in
neuroprosthetics, including advanced sensors and neural interfaces, aim to improve sensory
feedback in prostheses, enhancing users' balance, coordination, and overall functionality. These
advancements hold promise for improving the quality of life and mobility for individuals with
limb loss (Fig.3) [8].

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 Fig. 2.Muscles [5] [6]. Fig. 3.Nerves [7] [8].

(Fig.4) The ankle's stability in ankle-foot prostheses relies on ligaments that stabilize the lower
leg and form essential components of the joint capsule. These include the anterior inferior
tibiofibular ligament (AITFL), connecting the front of the ankle joint between the tibia and
fibula, and the posterior fibular ligaments—comprising the posterior inferior tibiofibular
ligament (PITFL) and the transverse ligament—that provide stability at the back of the ankle.
The interosseous ligament, positioned between the tibia and fibula, reinforces the connection
from knee to ankle, supporting the syndesmosis where these bones meet. Together, these
ligaments ensure joint integrity crucial for activities like walking and climbing in prosthetic
design (Fig.4) [5] [6].

Fig. 4.Ligaments [5] [6].

(Fig.5) The Achilles tendon, the body's largest and strongest tendon, connects the powerful calf
muscles—the gastrocnemius and soleus—to the heel bone (calcaneus). This tendon is crucial for
transmitting the force generated by these muscles during activities such as walking, running, and
jumping, facilitating efficient movement and stability of the ankle joint. On the other hand, the
posterior tibial tendon, situated on the inner side of the ankle and foot, extends from the posterior
tibialis muscle to various bones in the foot. It plays a vital role in supporting the foot's arch and
aiding in inward foot rotation (inversion). By maintaining the structural integrity of the foot and
providing stability during weight-bearing activities, the posterior tibial tendon contributes
significantly to normal gait and overall foot function (Fig.5) [5].

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 Fig. 5.Tendons [5].

The vascular anatomy of the lower leg and foot is crucial for providing oxygenated blood and
nutrients essential for tissue function and mobility. The popliteal artery, a continuation of the
femoral artery, runs behind the knee joint and branches into the anterior tibial artery, which
supplies the front of the lower leg, and the posterior tibial artery, responsible for blood flow to
the posterior compartment of the leg and the foot. The fibular (peroneal) artery branches off from
the posterior tibial artery [5], supporting the lateral aspect of the leg and foot. Distally, the
plantar artery contributes to the blood supply of the sole of the foot, ensuring adequate
circulation to support weight-bearing activities. Additionally, the sural artery provides blood to
the lateral aspect of the leg and foot. Together, these arteries form a comprehensive network that
supports the metabolic needs of the lower limb, facilitating optimal function during activities
such as walking, running, and climbing. Understanding this vascular system is critical for
designing prosthetic devices that maintain proper blood flow and support the physiological
demands of active individuals (Fig.6) [5] [7].

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 Fig. 6.Vascular network in the ankle [7].

2.2.Biomechanical Considerations

Detailed understanding of the gait cycle phases and their corresponding prosthetic functions is
crucial for designing effective ankle-foot prostheses that can enhance mobility and functionality
for users, particularly in demanding activities such as rock climbing [3] [9] [10] [14].

 Heel-strike to Foot-flat: The prosthesis controls plantar flexion using a linear spring
mechanism. This helps in absorbing the impact and preparing for the next phase [14].
 Foot-flat to Maximum Dorsiflexion: Controlled dorsiflexion occurs with the help of a
nonlinear spring, allowing the foot to adapt to the ground and providing stability [14].
 Maximum Dorsiflexion to Toe-off: During this phase, the prosthesis provides powered
plantar flexion, combining a torque source with a spring mechanism to push off the
ground and propel the body forward [14].
 Swing Phase: The prosthesis uses position control to ensure the foot is correctly
positioned for the next heel-strike, aiding in a smooth transition between steps (Fig.7)
[10] [14].

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 Fig. 7. Normal human ankle biomechanics for level-ground walking [9][10].

Fig. 8. Average ankle torque is plotted versus ankle angle for N=10 individuals with intact limbs
walking at a moderate gait speed (1.25 m/s) [9] [10].

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The solid line shows the ankle torque—angle behaviour during stance while the dash line shows
the ankle behaviour during the SW. The points (1), (2), (3), and (4) represent the conditions of
the foot at heel-strike, foot-flat, maximum dorsiflexion, and toe-off, respectively. The segments
(1)—(2), (2)—(3), (3)—(4), and (4)—(1) represent the ankle torque—angle behaviours during
CP, CD, PP, and SW phases of gait, respectively. Segments (1)—(2) and (2)—(3) reveal
different spring behaviours of the human ankle during CP and CD, respectively. The area W
enclosed by points (1), (2), (3), and (4) is the net work done at the joint per unit body mass
during the stance period (Fig.8) [9] [10].

2.3. Comparison Between Human Ankle and Prosthetic Ankle Behaviour

Fig. 9. Comparison Between Human Ankle and Prosthetic Ankle Behaviour [9].

Figure X presents a comparative analysis of normal human ankle behaviour (a) and prosthetic
ankle walking behaviour (b). In the model of normal human ankle behaviour, the ankle joint
operates through a sequence of phases: heel-strike, foot-flat, start of push-off, maximum
dorsiflexion, and toe-off. This natural motion is depicted through the interaction of torque and
ankle angle, demonstrating how the human ankle adapts dynamically to different phases of
walking and climbing [9] [10].

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In contrast, the prosthetic ankle walking behaviour showcases the efforts to replicate this natural
movement through mechanical means. The prosthetic model incorporates components like
springs and torque sources to mimic the natural biomechanics. The prosthetic behaviour diagram
highlights the decomposition of the torque into spring and torque source elements, aiming to
replicate the natural ankle’s response [9] [10].

Key elements include

KCD and KCP, representing the spring constants, and

τ PP, the offset output torque,

which are critical for achieving a functional prosthetic gait.

∆ W =∆ τ
( τKPP + 2∆Kτ )
CD CP

THIS equation encapsulates the net work done at the ankle joint, emphasizing the importance of
precise torque management for effective prosthetic function. By understanding and modelling
these behaviours, advancements in prosthetic design, such as the EMG-controlled 2-DOF robotic
ankle-foot prosthesis, can be optimized to provide greater mobility and stability for amputees,
particularly those engaged in complex activities like rock climbing. This comparative analysis
underscores the challenges and innovations in replicating the sophisticated mechanics of the
human ankle through prosthetic technology (Fig.10) [1] [9] [10].

3. Background
3.1. History of Ankle Foot Prosthetics
The development of powered ankle-foot prostheses has significantly advanced over the past few
decades. The first powered ankle-foot prosthesis capable of performing net positive work was
built by Klute et al. in 1998. This pioneering device used pneumatic actuation with off-board
power, marking a crucial step toward enhancing the functional capabilities of prosthetic limbs. In
2007, Versluys et al. furthered this innovation by designing another powered ankle-foot
prosthesis, also employing pneumatic actuation with off-board power [3]. Some recent research

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has led to the development of quasi-passive ankle–foot prostheses that use active damping or
spring-clutch mechanisms to automatically adjust prosthetic ankle angle for distinct ground
surfaces, or to allow improved metabolic walking economy. These quasi-passive devices do not
include an actuator that can actively plantar-flex the prosthetic ankle during the terminal stance
phase, so no network is performed during a step, as is not the case with the biological ankle
during walking [3].

Some of the quasi-passive devices includes -

RJFA (Robotic Joint Foot-Ankle)- The RJFA represents a significant advancement in prosthetic
foot design, incorporating robotics to enhance movement and adaptability. This system utilizes
sensors and microprocessors to provide real-time adjustments, allowing for smoother transitions
and more natural gait patterns. The robotic components work in conjunction with the user’s
residual limb movements, offering improved stability and responsiveness [12].

SACH (Solid Ankle Cushioned Heel) [11] -The SACH foot, developed in the mid-20th century,
remains a fundamental design in prosthetic feet consisting of wood, rubber, and compressible
foam materials. It features a solid ankle with a cushioned heel, providing basic support and shock
absorption. While it lacks the dynamic adaptability of powered prostheses, the SACH foot is
known for its simplicity, durability, and affordability, making it a popular choice in various
contexts [12]. Passive ankle prosthetic devices, such as the SACH foot, have been shown to
produce less, approximately one-eighth of the power of intact gastrocnemius and soleus muscles
(Fig.11) [11].

ESAR (Energy Storage and Return) prosthetic feet represent a significant advancement in
prosthetic technology, designed to mimic the natural biomechanics of human walking more
closely than traditional prosthetic feet like SACH (Solid Ankle Cushion Heel). By storing and
releasing energy during each step, ESAR feet enhance push-off power, reduce metabolic costs,
and allow for increased self-selected walking speeds. Studies have demonstrated that ESAR feet
enable users to achieve greater energy generation, maintain longer intact step lengths, and ensure
stability during various activities. These biomechanical advantages make ESAR prosthetic feet a

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preferred choice for enhancing mobility and improving quality of life for prosthetic users
(Fig.12) [11].

Fig. 10. SACH Foot - a)Labelled drawing of a SACH foot cross-section, including wood,
rubber, and compressible foam materials, and (b,c) photograph of SACH foot prosthetic
including a cosmetic shell [11].

Fig. 11. EASR Foot - (a) Appearance of constructed functional ESAR prosthetic and (b) labelled

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 graphic of the ESAR foot design with the top blade, middle blade, sole blade, mechanical link,
and main body [11].

But, this paper mainly concentrates on ankle foot prosthesis for rock climbing and one of the
most recent research done in this area is the mechanical design and control of a novel
lightweight, electromyographically (EMG) controlled 2- Degree of Freedom (DOF) robotic
ankle-foot prosthesis for rock climbing [1] [10].

3.2.Electromyographically (EMG) Controlled 2- Degree of Freedom (DOF) Robotic Ankle-

Foot Prosthesis for Rock Climbing [1] [11].

Fig. 12. Model of robotic climbing ankle showing subsystems of device: linear actuators, custom
rock climbing foot, 2-DOF ankle U-joint, actuator mounting bracket, electronics, and protective
cover [1]

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The prosthesis includes motorized ankle and subtalar joints capable of emulating key
biomechanical behaviours of the ankle-foot complex during rock climbing. It uses EMG surface
electrodes embedded in a custom silicone liner worn on the residual limb to control the
prosthesis volitionally. The device allows for 0.29 radians each of dorsiflexion and plantar
flexion, and 0.39 radians each of inversion and eversion [1].

Performance Metrics: Preliminary evaluations validated the system mass at 1292 grams, build
height of 250 mm, joint velocity of 2.18 radians/second, settling time of 120 milliseconds, and
steady-state error of 0.008 radians [1].

3.2.1.Mechanical Design:

Fig. 13. The four major motions of the ankle-foot prosthesis [1].

The four major motions of the ankle-foot prosthesis -

Fig.9.(a) plantar flexion occurs when both actuators contract,
Fig.9.(b) dorsiflexion occurs when both actuators extend,
Fig.9.(c) eversion occurs when the left actuator contracts and the right actuator extends, and
Fig.9.(d) inversion when the left actuator extends and the right actuator contracts (Fig. 9) [1].

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  2-DOF U-Joint: Provides ankle and subtalar joint movement, crucial for stability and
adaptability on varied climbing surfaces.
 Non-backdrivable Linear Actuators: Custom designs minimize motor torque
requirements and enhance efficiency.
 Custom Climbing Foot: Designed using 3D scanning and MultiJet fusion 3D printing
for lightweight and robust performance.
 High-Strength Materials: Structural components machined from titanium and
aluminium ensure durability and reliability under load.

3.2.2.Electronics Design:

 Flex SEA Embedded System: Optimized for wearable robotics, integrates motor
controllers, power management, and a microcontroller for real-time control [15].
 Brushed DC Motors: Selected for torque output and compact size, with integrated
optical encoders for precise position feedback.
 Load Cells: Integrated in each actuator for accurate torque sensing, with motor encoders
to monitor motor positions.
 Power Supply: Lithium polymer battery provides adequate capacity for actuators, EMG
system, and embedded electronics [1] [15].

3.2.3.Electromyography Acquisition and Processing:

 Muscle Activation: Signals from agonist/antagonist pairs are acquired via surface
electrodes integrated into a custom prosthetic liner.
 EMG System: Signals are amplified, digitized, and filtered (band-pass filter: 80–420 Hz)
by an embedded system, then processed to calculate percent maximum voluntary
contraction (%MVC).
 Calibration: Subject performs maximal contractions to establish %MVC values for real-
time control.
 Communication: Processed EMG data is transmitted to the prosthetic control system via
I2C communication, updating at 1 kHz [16] [17].

3.2.4.Control System Design:

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  Operating States: The system operates in two states: supporting body weight (State 1)
and free space (State 2). Load cell feedback determines the state.
 EMG Processing: Muscle activation levels drive a virtual joint dynamic model,
calculating torque outputs based on normalized muscle activations.
 Dynamic Joint Model: Converts EMG signals into desired joint angles using moment
arm lengths and virtual joint parameters.
 Position Controller: PID controllers translate joint angle commands into PWM signals
for actuators, ensuring accurate positioning and torque application [1].

3.2.5.Actuator Design:

 Linear Actuators: Each features a brushed DC motor driving an ACME thread lead
screw, coupled through a flexible shaft and supported by angular contact bearings.
 Anti-backlash Mechanism: Minimizes play during directional changes, crucial for
stability and accuracy.
 Structural Components: Machined from titanium and aluminium for durability under
load [1].

3.2.6.Validation:

 Finite Element Analysis (FEA): Simulations validate structural integrity and stress
distribution, ensuring reliability in challenging climbing conditions.

3.2.7.Evaluation:

1. Biomechanical Assessment: The clinical evaluation involved one subject with a

transtibial amputation. Measurements of joint angles of the ankle-foot, knee, and hip
during rock climbing showed that the robotic prosthesis increased the range of achieved
ankle and subtalar positions compared to a standard passive prosthesis.
2. Biomechanical Benefits: Using the robotic prosthesis resulted in decreased maximum
knee and hip flexion angles while climbing, suggesting improved climbing efficiency and
comfort.

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3.2.8.Specifications of the EMG-Controlled 2-DOF Robotic Ankle-Foot Prosthesis.

TABLE 1- Design Specifications and Resulting Parameters for Robotic Prosthesis

Design parameters were developed for the prosthesis based on literature reviews and interviews
with rock climbers with transtibial amputation (Table 1) [1].

The robotic ankle-foot prosthesis has several key specifications that enhance its functionality for
rock climbing:

1. Range of Motion: The prosthesis offers a range of motion of ±0.39 radians for
inversion/eversion and ±0.29 radians for dorsiflexion/plantar flexion.
2. Max Payload: It can support a payload of over 100 kg.
3. Free-Space Torque: The device generates a torque of 0.55 Nm in free space.
4. Velocity: The maximum joint velocity is 2.18 radians per second.
5. Accuracy: It has an accuracy of ±0.008 radians.
6. Mass: The total mass of the prosthesis is 1292 grams (Table 2) [1].
7. Build Height: The prosthesis has a build height of 250 mm.

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 8. Battery Life: The battery life exceeds 4 hours, ensuring extended use during climbing
sessions.

Table 2 - Ankle-Foot Prosthesis Mass Distribution [1].

4. Results

The results of the Electromyographically (EMG) Controlled 2-Degree of Freedom (DOF)

Robotic Ankle-Foot Prosthesis for Rock Climbing indicate several promising outcomes:

1. Enhanced Range of Motion: The robotic prosthesis increased the range of achieved
ankle and subtalar positions compared to a standard passive prosthesis. Specifically, the
ankle joint achieved a range of motion of 0.31 radians with the robotic prosthesis,
whereas it was 0 radians with the passive prosthesis. The subtalar joint had a range of
motion of 0.09 radians with the robotic device, compared to 0 with the passive prosthesis.

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 This enhanced range of motion suggests that users can manipulate the prosthesis more
effectively in real time while rock climbing.
2. Improved Biomechanics: The use of the robotic prosthesis led to a decrease in
maximum knee flexion and hip flexion angles during climbing compared to the passive
prosthesis. The reduced excursion of the knee and hip indicates improved biomechanics
and potentially less physical strain on the user. The device also demonstrated sufficient
accuracy and speed in position command response during the evaluation
3. Positive User Feedback: Subject feedback was positive, noting that the control of the
device felt intuitive and sufficiently fast. The subject also mentioned that adjusting the
joint angle of the device allowed for more accurate foot positioning on holds and
improved comfort in the prosthetic socket during climbing.
4. Device Performance: The prosthesis showed a joint velocity of 2.18 radians/second, a
settling time of 120 milliseconds, and a steady state error of 0.008 radians. These metrics
indicate that the device performs reliably and accurately under the conditions tested.
5. Future Research: Further studies are planned to assess the clinical efficacy of the
prosthesis on a larger subject population. Additional biomechanical studies will be
conducted with more subjects and diverse climbing routes to fully explore the benefits of
the device. Future designs aim to reduce the mass and build height of the prosthesis,
improve response time, and enhance overall functionality.

These preliminary results suggest that the 2-DOF EMG-controlled robotic ankle-foot prosthesis
can significantly improve rock climbing performance and biomechanics for individuals with
transtibial amputation [1 – 15].

6. Conclusion

The development and implementation of specialized ankle-foot prostheses for rock climbing
mark a significant advancement in the field of prosthetic technology. This study focused on the
Electromyographically (EMG) Controlled 2-Degree of Freedom (DOF) Robotic Ankle-Foot
Prosthesis, which is specifically designed to address the unique challenges faced by alpinists
with lower limb amputations. The findings demonstrate that these innovative prosthetic devices
can significantly enhance climbing performance, providing increased range of motion, improved

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biomechanics, and greater comfort for users. The prosthesis' ability to replicate the complex
functions of the human ankle and foot allows for more precise and effective foot positioning on
climbing holds, ultimately promoting better performance and reducing physical strain.

The research underscores the importance of tailoring prosthetic designs to meet the specific
needs of rock climbers, thereby expanding the possibilities for individuals with limb loss to
engage in this demanding sport. By enhancing mobility, stability, and adaptability, these
advanced prostheses contribute to improved quality of life, fostering independence and self-
esteem among amputees.

Future research should focus on further refining these prosthetic designs, reducing their mass and
build height, and enhancing their response time and overall functionality. Additionally,
expanding clinical evaluations to include a larger and more diverse population of subjects will
provide a more comprehensive understanding of the prosthesis' benefits and potential areas for
improvement. This study sets the foundation for ongoing innovation in prosthetic technology,
with the goal of creating more effective and efficient solutions for the unique challenges of rock
climbing and other specialized activities.

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University of Leeds, School of Sport and Exercise Sciences, 2005
C. J. Low. Biomechanics of Rock Climbing Technique. PhD thesis, The
University of Leeds, School of Sport and Exercise Sciences, 2005

M.J. Highsmith, J.T. Kahle, J.L. Fox, K.L. Shaw, W.S. Quillen, and L.J.
Mengelkoch. Metabolic Demands of Rock Climbing in Transfemoral
Amputees. International Journal of Sports Medicine, 31(01):38–43,
January 2010
M.J. Highsmith, J.T. Kahle, J.L. Fox, K.L. Shaw, W.S. Quillen, and L.J.
Mengelkoch. Metabolic Demands of Rock Climbing in Transfemoral
Amputees. International Journal of Sports Medicine, 31(01):38–43,
January 2010
M.J. Highsmith, J.T. Kahle, J.L. Fox, K.L. Shaw, W.S. Quillen, and L.J.
Mengelkoch. Metabolic Demands of Rock Climbing in Transfemoral
Amputees. International Journal of Sports Medicine, 31(01):38–43,
January 2010

H.M. Herr and A.M. Grabowski. Bionic anklefoot prosthesis normalizes

walking gait for persons with leg amputation. Proceedings of the Royal
Society B: Biological Sciences, 279(1728):457–464, February 2012
H.M. Herr and A.M. Grabowski. Bionic anklefoot prosthesis normalizes
walking gait for persons with leg amputation. Proceedings of the Royal
Society B: Biological Sciences, 279(1728):457–464, February 2012
H.M. Herr and A.M. Grabowski. Bionic anklefoot prosthesis normalizes
walking gait for persons with leg amputation. Proceedings of the Royal
Society B: Biological Sciences, 279(1728):457–464, February 2012
H.M. Herr and A.M. Grabowski. Bionic anklefoot prosthesis normalizes
walking gait for persons with leg amputation. Proceedings of the Royal
Society B: Biological Sciences, 279(1728):457–464, February 2012
H.M. Herr and A.M. Grabowski. Bionic anklefoot prosthesis normalizes
walking gait for persons with leg amputation. Proceedings of the Royal
Society B: Biological Sciences, 279(1728):457–464, February 2012

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