Cyclists with unilateral transtibial amputation (CTA) provide a unique model to study integration of the neuromuscular and bicycle systems while having the option to modify this integration via the properties of the prosthesis. This study included eight CTA and nine intact cyclists. The cyclists pedaled on a stationary bicycle with instrumented force pedals. The CTA group pedaled with a stiff or flexible prosthetic foot during a simulated time trial and a low difficulty condition. During the time trial condition, pedaling with the flexible foot resulted in force and work asymmetries of 11.4% and 30.5%, the stiff foot displayed 11.1% and 21.7%, and the intact group displayed 4.3% and 4.2%, respectively. Similar trends were shown in the low difficulty condition. These data suggest foot stiffness has an effect on cycling symmetry in amputees.

Prosthetic feet are designed to store energy during early stance and then release a portion of that energy during late stance. The usefulness of providing more energy return depends on whether or not that energy transfers up the lower limb to aid in whole body propulsion. This research examined how increasing prosthetic foot energy return affected walking mechanics across various slopes. Five people with a uni-lateral transtibial amputation walked on an instrumented treadmill at 1.1 m/s for three conditions (level ground, +7.5°, −7.5°) while wearing a prosthetic foot with a novel linkage system and a traditional energy storage and return foot. The novel foot demonstrated greater range of motion (p = 0.0012), and returned more energy (p = 0.023) compared to the traditional foot. The increased energy correlated with an increase in center of mass (CoM) energy change during propulsion from the prosthetic limb (p = 0.012), and the increased prosthetic limb propulsion correlated to a decrease in CoM energy change (i.e., collision) on the sound limb (p < 0.001). These data indicate that this novel foot was able to return more energy than a traditional prosthetic foot and that this additional energy was used to increase whole body propulsion.

People with amputations may find cycling advantageous for exercise, transportation and rehabilitation. The reciprocal nature of stationary cycling also makes it a viable model for research in motor control because the body is supported by the saddle allowing the researcher to focus on the cyclic movement of the legs without the confounding variable of balance. The purpose of this article is to provide an overview of the cycling task in intact cyclists and relate this information to understanding the challenges faced by cyclists with transtibial amputations (CTA). Ongoing research into the biomechanics of CTAs will be summarized to expose the differences between intact and CTA cycling mechanics, asymmetries between limbs of CTAs as well as neuromuscular adaptation following amputation. The article will include recommendations for prosthetic design and modification of the bicycle to improve cycling performance for CTA at all experience levels.

The neuromusculoskeletal system interacts with the external environment via end-segments, e.g. feet. A person with trans-tibial amputation (TTAmp) has lost a foot and ankle; hence the residuum with prosthesis becomes the new end-segment. We investigated changes in kinetics and muscle activity in TTAmps during cycling with this altered interface with the environment. Nine unilateral TTAmps and nine subjects without amputation (NoAmp) pedaled at a constant torque of 15Nm and a constant cadence of 90rpm (~150watts). Pedal forces and limb kinematics were used to calculate resultant joint moments. Electromyographic activity was recorded to determine its magnitude and timing. Biomechanical and EMG variables of the amputated limb were compared to those of the TTAmp sound limb and to the dominant limb in the NoAmp group using a one-way ANOVA. Results showed maximum angular displacement between the residuum and prosthesis was 4.8 ± 1.8deg. The amputated limb compared to sound limb and NoAmp group produced lower extensor moments averaged over the cycle about the ankle (13 ± 2.3, 20 ± 5.7, and 19 ± 5.3Nm, respectfully) and knee (8.4 ± 5.0, 15 ± 4.5, and 12.7 ± 5.9Nm, respectfully) (p<0.05). Gastrocnemius and rectus femoris peak activity in the TTAmps shifted to later in the crank cycle (by 36° and 75°, respectfully; p<0.05). These data suggest gastrocnemius was utilized as a one-joint knee flexor in combination with rectus femoris for prosthetic socket control and highlight prosthetic control as an interaction between the residuum, prosthesis and external environment.

Individuals with a unilateral transtibial amputation have lost the structure of the ankle joint and the muscles and connective tissues controlling the joint. In addition, sensory input from the joint and surrounding tissues has also been lost. These individuals must now adapt to structural and physiological changes related to the amputation and interact with their environment via a prosthetic limb on one side and via an intact limb on the other. 1 Changes that occur after amputation include: the sound limb becomes the dominate limb for locomotion [2][3][4][5][6] ; atrophy of the residual limb with possible hypertrophy of the sound limb 7 ; and alterations in movement strategies. 1,4,5 All of these changes are interrelated and will affect the person's ability to generate and effectively direct forces to interact with their environment. It remains unclear how these distinct, yet integrated, changes relate to the control of task performance. The purpose of this study was to investigate the pedaling technique employed by transtibial Effectiveness of force production in persons with unilateral transtibial amputation during cycling Walter Lee Childers and Robert J Gregor Abstract Background: Few published reports exist regarding the control of the human/prosthesis interface in persons with unilateral transtibial amputation. Objective: To investigate strategies employed by prosthetic users in controlling the human/prosthesis interface to highlight challenges associated with either the amputation or the design of the prosthesis. Study Design: Randomized controlled trial. Methods: Cycling was used as the locomotor task to allow for better control of task mechanics compared to walking. A group of nine cyclists with intact limbs were compared to eight cyclists with transtibial amputation (CTA) during a simulated cycling time trial. The CTA group pedaled with a stiff and flexible prosthetic foot. Reaction forces between the foot and the pedal were measured using an instrumented pedal system. The force effectiveness (FE) ratio was used as the measure of task performance. The FE ratio is the force component normal to the bicycle crank arm divided by the resultant force for both limbs and is commonly used to analyze pedaling technique. Results: The CTA group was equally as effective at applying forces as the intact group. Conclusions: These data suggest that individuals with lower limb loss are able to compensate for their amputation to utilize a similar pedaling technique for locomotor performance. As global strategies, e.g. force effectiveness, appear similar between groups future research should focus on local strategies, e.g. individual joint kinematics and kinetics. Clinical relevanceResearch involving local strategies, e.g. individual joint kinematics and kinetics and their relationship to net output of the human/prosthesis system, will enhance our understanding of this system while allowing for better clinical application of the research.

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The ability to quantify movement between the residual limb and the prosthetic socket will improve prosthetic treatment through the evaluation of different prosthetic suspensions, socket designs, and motor control of the prosthetic interface.

The purpose of this research was 1) to develop a system to measure pistoning in sagittal plane (2D), 2) to test this system during a dynamic task (cycling), and 3) to determine the effect of prosthetic suspension. The limb/socket motion measurement device consisted of an aluminum frame attached to the prosthetic socket. Two linear potentiometers were attached to the frame and aligned with the longitudinal and orthogonal axes of the prosthesis. The subject wore a small metal bracket adhered to the skin over the distal tibia that protruded through a slit cut into a prosthetic liner. The opposite ends of the linear potentiometers were connected to the bracket. Two subjects with unilateral transtibial amputation secondary to trauma (31 Ϯ 11 years, 82 Ϯ 15 kg) pedaled on a stationary electromagnetically braked ergometer at 150 W and 90 rpm. The pin and cuff strap type were the two prosthetic suspensions tested. The pin suspension produced less displacement in the superior/inferior (S/I) direction (2 vs. 4 mm). Suspension type had no effect on the magnitude of displacement in the anterior/posterior direction (ϳ4 mm). The device could measure differences between two different prosthetic suspension systems, but these differences were very small. Future research should address movement of the knee center within the prosthetic socket and use the limb/socket motion measurement device to measure pistoning during gait. (J Prosthet Orthot. 2012;24:19 -24.)