Influence of prosthetic foot selection for load carriage on prosthetic limb mechanical work.

Advanced age brings a distal-to-proximal redistribution of positive joint work during walking that is relevant to walking performance and economy. It is unclear whether negative joint work is similarly redistributed in old age. Negative work can affect positive work through elastic energy return in gait. We determined the effects of age, walking speed, and grade on positive and negative joint work in young and older adults. Bilateral ground reaction force and marker data were collected from healthy young (age = 22.5 yr, n = 18) and older (age = 76.0 yr, n = 22) adults walking on a split-belt instrumented treadmill at 1.1, 1.4, and 1.7 m·s at each of three grades (0%, 10%, and -10%). Subjects also performed maximal voluntary eccentric, isometric, and concentric contractions for the knee extensors (120°·s, 90°·s, and 0°·s) and plantarflexors (90°·s, 30°·s, and 0°·s). Compared with young adults, older adults exhibited a distal-to-proximal redistribution of positive leg joint work during level (P < 0.001) and uphill (P < 0.001) walking, with larger differences at faster walking speeds. However, the distribution of negative joint work was unaffected by age during level (P = 0.150) and downhill (P = 0.350) walking. Finally, the age-related loss of maximal voluntary knee extensor (P < 0.001) and plantarflexor (P = 0.001) strength was smaller during an eccentric contraction versus concentric contraction for the knee extensors (P < 0.001) but not for the plantarflexors (P = 0.320). The distal-to-proximal redistribution of positive joint work during level and uphill walking is absent for negative joint work during level and downhill walking. Exercise prescription should focus on improving ankle muscle function while preserving knee muscle function in older adults trying to maintain their independence.

Inclined running is a common component of many runners' training programs in the form of hill repeats. Runners are often forced to slow their running pace, iso-efficiency speed (ISO), during inclined running to maintain their metabolic effort. Though commonly used in training, little is known regarding the changes in joint kinetics associated with running on an inclined treadmill at an ISO speed. PURPOSE: To evaluate changes in lower extremity joint work when running on increasing inclines at ISO speeds. METHODS: Eleven NCAA Division I runners performed five 5-second treadmill running trials during each of three ISO speed inclined conditions: 0% incline, 4% incline, and 8% incline. ISO speed was confirmed using oxygen consumption (VO2) using indirect calorimetry. Kinematics and ground reaction forces were recorded simultaneously using an 8-camera motion capture system (100 Hz, Qualisys Inc.) and instrumented treadmill (1000 Hz, Bertec), respectively. Visual 3D was used to calculate ankle, knee and hip joint powers while custom software (MATLAB, MathWorks) calculated positive and negative joint work as joint power integrated with time. A repeated measures ANOVA with Tukey's post-hoc was used to determine the effect of treadmill incline on joint work. RESULTS: Negative ankle joint work increased while negative knee and hip joint work decreased with increasing treadmill incline (Table 1). Positive ankle and hip joint work increased while positive knee work decreased with increasing treadmill incline (Table 1). CONCLUSIONS: Our findings suggest that even at ISO speeds (i.e., reduced speeds to maintain effort), inclined treadmill running increases eccentric demands on plantarflexors, and concentric demands on knee and hip extensors. These data may support altered training prescriptions for athletes recovering from joint-specific muscular injuries to minimize training-related stresses placed on those tissues.

People with a transtibial amputation using passive-elastic prostheses exhibit reduced prosthetic ankle power and push-off work compared to non-amputees and compensate by increasing their affected leg (AL) hip joint work and unaffected leg (UL) ankle, knee, and hip joint and leg work during level-ground walking. Use of a powered ankle-foot prosthesis normalizes step-to-step transition work during level-ground walking over a range of speeds for people with a transtibial amputation, but the effects on joint work during level-ground, uphill and downhill walking have not been assessed. We investigated how use of passive-elastic and powered ankle-foot prostheses affect leg joint biomechanics during level-ground and sloped walking. 10 people with a unilateral transtibial amputation walked at 1.25 m/s on a dual-belt force-measuring treadmill at 0°, ±3°, ±6°, and ±9° using their own passive-elastic and a powered prosthesis (BiOM T2, BionX Medical Technologies, Inc. Bedford, MA, USA) while we measured kinematic and kinetic data. We calculated AL and UL prosthetic, ankle, knee, hip, and individual leg positive, negative, and net work. Use of a powered compared to passive-elastic ankle-foot prosthesis resulted in greater AL prosthetic and individual leg net work on uphill and downhill slopes. Over a stride, AL prosthetic positive work was 23-30% greater (p<0.05) during walking on uphill slopes of +6°, and +9°, prosthetic net work was up to 10 times greater (more positive) (p≤0.005) on all uphill and downhill slopes and individual leg net work was 146% and 82% more positive (p<0.05) at uphill slopes of +6° and +9°, respectively, with use of the powered compared to passive-elastic prosthesis. Greater prosthetic positive and net work through use of a powered ankle-foot prosthesis during uphill and downhill walking improves mechanical work symmetry between the legs, which could decrease metabolic cost and improve functional mobility in people with a transtibial amputation.

Load carriage influences intact limb knee loading estimate associated with osteoarthritis in individuals with transtibial amputation.

The influence of load carriage and prosthetic foot type on individual muscle and prosthetic foot contributions to body support and propulsion

Footwear companies modify midsole stack height in running shoes, often aiming to either enhance performance or reduce the risk of injuries, such as patellofemoral pain. Despite changes in midsole characteristics, the incidence of running-related injuries remains high. Limited research has investigated the effects of minimal, traditional, and maximal footwear in the same study. Therefore, the purpose of this study was to compare patellofemoral kinetics and ankle, knee, and hip joint work between minimal, traditional, and maximal footwear during running. It was hypothesised that minimal shoes would reduce patellofemoral joint stress and knee negative work but increase ankle negative work compared to traditional and maximal shoes. Twenty-seven healthy runners completed five trials in each footwear condition, while an 8-camera motion capture system and two embedded force plates collected three-dimensional kinematic and kinetic data of the hip, knee, and ankle. Peak quadriceps force, patellofemoral joint reaction force, patellofemoral joint stress, and positive, negative, and net joint work were compared between footwear conditions using repeated measures ANOVAs (α = 0.05). Peak quadriceps force, patellofemoral joint reaction force and patellofemoral joint stress were significantly lower in the minimal shoe compared to the maximal and traditional shoes. Negative ankle work was significantly higher in the minimal shoe and significantly lower in the maximal shoe compared to the traditional shoe, while net ankle work was significantly lower in the minimal shoe compared to the maximal and traditional shoes. Negative knee work, positive knee work, and net knee work were significantly lower in the minimal shoe compared to the other two shoes. These findings suggest that midsole stack height can influence patellofemoral kinetics as well as joint work at the ankle and knee.

Introduction Loss of power production at the ankle joint contributes to many problems people with unilateral transtibial (UTT) amputation experience during walking. Little is known about walking acceleration and deceleration, which is common in daily living and may require substantial compensatory behaviors from the residual lower-limb joints. Objective The aim of this study was to quantify individual lower-limb joint contributions to walking acceleration and deceleration in people with UTT amputations. We hypothesized that joint work on the prosthetic limb would be primarily modulated at the hip, and joint work on the sound limb would be primarily modulated at the ankle. Study Design The study is a repeated-measures design. Methods Six K3 level ambulators with UTT amputations participated. Participants performed a total of 40 walking trials while wearing their own nonarticulated dynamic prosthetic foot and socket. Each trial consisted of walking along a straight walkway. After walking approximately 2 m, participants received a cue instructing them to perform one of three walking conditions: continue walking at a constant average velocity, rapidly accelerate, or rapidly decelerate. We used ground reaction forces and motion capture data to derive joint kinematics and kinetics during the three walking conditions. We used one-way repeated-measures analyses of variance (ANOVAs) to identify significant differences between conditions. Results For the sound limb, positive hip and ankle work was significantly greater during acceleration compared with constant average velocity or deceleration conditions, and negative knee work was significantly greater during acceleration compared with deceleration. For the prosthetic limb, negative ankle work was significantly greater during acceleration compared with deceleration. Conclusions People with UTT amputation who use nonarticulated prostheses primarily modulated joint work on their sound limb to accelerate or decelerate walking speed. Clinical Relevance Characterizing compensatory behaviors of people with a UTT amputation is important for understanding injury mechanisms, informing clinical guidelines, and improving future ankle-foot prosthesis designs.

Prosthetic foot prescription guidelines lack scientific evidence and are concurrent with an amputee's concurrent with an amputee's Medicare Functional Classification Level (K-Level) and categorization of prosthetic feet. To evaluate the influence of gait training and four categories of prosthetic feet (K1, K2, K3, and microprocessor ankle/foot) on Symmetry in External Work for K-Level-2 and K-Level-3 unilateral transtibial amputees. Randomized repeated-measures trial. Five K-Level-2 and five K-Level-3 subjects were tested in their existing prosthesis during Session 1 and again in Session 2, following 2 weeks of standardized gait training. In Sessions 3-6, subjects were tested using a study socket and one of four randomized test feet. There was an accommodation period of 10-14 days with each foot. Symmetry in External Work for positive and negative work was calculated at each session to determine symmetry of gait dynamics between limbs at self-selected walking speeds. K-Level-2 subjects had significantly higher negative work symmetry with the K3 foot, compared to K1/K2 feet. For both subject groups, gait training had a greater impact on positive work symmetry than test feet. Higher work symmetry is possible for K-Level-2 amputees who are trained to take advantage of K3 prosthetic feet designs. There exists a need for an objective determinant for categorizing and prescribing prosthetic feet.

Lower-limb joint work symmetry responses to load carriage and prosthetic foot type during transtibial amputee walking.

Running during sports and for physical activity often requires changes in velocity through acceleration and deceleration. While it is clear that lower extremity biomechanics vary during these accelerations and decelerations, the work requirements of the individual joints are not well understood. The purpose of this investigation was to measure the sagittal plane mechanical work of the individual lower extremity joints during acceleration, deceleration, and steady-state running. Ten runners were compared during acceleration, deceleration, and steady-state running using three-dimensional kinematics and kinetics measures. Total positive and negative joint work, and relative joint contributions to total work were compared between conditions. Total positive work progressively increased from deceleration to acceleration. This was due to greater ankle joint work during acceleration. While there was no significant change in total negative work during deceleration, there was a greater relative contribution of the knee to total negative work with a subsequent lower relative ankle negative work. Each lower extremity joint exhibits distinct functional roles in acceleration compared with deceleration during level running. Deceleration is dominated by greater contributions of the knee to negative work while acceleration is associated with a greater ankle contribution to positive work.

Gait biomechanics of skipping are substantially different than those of running

The effects of load carriage on joint work at different running velocities

Reflections and the future

Mechanical work performed by distal foot-ankle and proximal knee-hip segments during anticipated and unanticipated cutting

The compliant nature of distal limb muscle-tendon units is traditionally considered suboptimal in explosive movements when positive joint work is required. However, during accelerative running, ankle joint net mechanical work is positive. Therefore, this study aims to investigate how plantar flexor muscle-tendon behavior is modulated during fast accelerations. Eleven female sprinters performed maximum sprint accelerations from starting blocks, while gastrocnemius muscle fascicle lengths were estimated using ultrasonography. We combined motion analysis and ground reaction force measurements to assess lower limb joint kinematics and kinetics, and to estimate gastrocnemius muscle-tendon unit length during the first two acceleration steps. Outcome variables were resampled to the stance phase and averaged across three to five trials. Relevant scalars were extracted and analyzed using one-sample and two-sample t-tests, and vector trajectories were compared using statistical parametric mapping. We found that an uncoupling of muscle fascicle behavior from muscle-tendon unit behavior is effectively used to produce net positive mechanical work at the joint during maximum sprint acceleration. Muscle fascicles shortened throughout the first and second steps, while shortening occurred earlier during the first step, where negative joint work was lower compared with the second step. Elastic strain energy may be stored during dorsiflexion after touchdown since fascicles did not lengthen at the same time to dissipate energy. Thus, net positive work generation is accommodated by the reuse of elastic strain energy along with positive gastrocnemius fascicle work. Our results show a mechanism of how muscles with high in-series compliance can contribute to net positive joint work.