Negative Joint Work Research Articles

Influence of ankle invertor muscle fatigue on workload of the lower extremity joints during single-leg landing in the sagittal and frontal planes

BackgroundInsufficient rigidity of the foot owing to its ligaments and muscles can decrease the attenuation of the ground reaction force during landing. Therefore, dysfunction of the ankle invertors may increase the proximal joint load during landing. Research questionWhat are the effects of the fatigued ankle invertors on workload in the lower extremity joints during single-leg landing? MethodsTwenty-seven young adults (13 men and 14 women) performed landing trials in the forward and medial directions before and after exercise-induced fatigue of the ankle invertors. The exercise consisted of repeated concentric and eccentric ankle inversions until the maximum torque was below 80% of the baseline value. Negative joint workload during the landing tasks was calculated for the hip, knee, and ankle in the sagittal and frontal planes. Additionally, lower extremity work (the sum of the work of the hip, knee, and ankle) was calculated. ResultsInvertor fatiguing exercise resulted in a significant increase in negative joint work in the frontal and sagittal plane hip and the frontal plane knee during medial landing, whereas no significant change in negative joint work was observed during forward landing. SignificanceThese findings suggested that ankle invertor dysfunction may induce a high load on the proximal joints and have direction-specific effects.

Characteristics of upper limb joint mechanics with increased cane dependence during walking.

[Purpose] This study investigated the effects of differences in cane dependence on the mechanical work at the shoulder, elbow, and wrist joints during walking. [Participants and Methods] Fifteen volunteers participated in this study (mean ± standard deviation [SD] age: 24.9 ± 2.7 years, height: 1.73 ± 0.04 m, and body mass: 68.5 ± 8.9 kg). The participants walked under three conditions: (1) without a cane, (2) with a cane at 10% body weight (BW), and (3) with a cane at 20% BW. The shoulder, elbow, and wrist joint work was calculated to evaluate the mechanical load. [Results] The results indicated a significant interaction between load conditions and positive joint work, as well as between load conditions and negative joint work. The positive work in the shoulder and elbow joints significantly increased in the 20% BW condition compared to that in the 10% BW condition. [Conclusion] Increased cane dependence did not uniformly increase the positive and negative work of the shoulder, elbow, and wrist joints. Increased cane dependence during walking increases energy generation in the shoulder and elbow joints, which can result in adverse musculoskeletal strain on the shoulder and elbow joints.

The Effects of Fatigue on the Lower Limb Biomechanics of Amateur Athletes during a Y-Balance Test.

The Y-Balance Test (YBT) is a reliable tool for assessing the dynamic balance of athletes' lower limbs. This study aimed to compare the effects of the YBT on lower limb biomechanics before and after fatigue. Sixteen adult male recreational athletes were recruited for the study, and motion capture in combination with a force plate was used to collect kinematic, dynamics, and center of pressure (COP) data of the dominant leg during YBT testing before and after fatigue. Based on the research findings, there were significant statistical differences in the distances reached during the YBT in three directions before and after fatigue. After fatigue, there is a significant decrease in the ROM of the hip and knee joints in all three directions. Also, there is a significant increase in hip joint torque in the anterior- and posterior-lateral directions, while a significant decrease in hip and ankle joint torque is observed in the posterior-medial direction. Moreover, there is an increasing trend in positive and negative joint work for the hip, knee, and ankle joints in all three directions after fatigue. The range of COP displacement also increases following fatigue. The decline in YBT scores demonstrates the detrimental impact of fatigue on the dynamic balance of the lower limbs of adult male amateur athletes. We hope that these results can provide information for athletes and coaches to better understand the effects of fatigue on the dynamic balance of lower limbs, so as to carry out targeted lower limb balance training and prevent sports injuries.

Increasing Breast Support is Associated With a Distal-to-Proximal Redistribution of Joint Negative Work During a Double-Limb Landing Task.

Female athletes exhibit greater rates of anterior cruciate ligament injury compared with male athletes. Biomechanical factors are suggested to contribute to sex differences in injury rates. No previous investigation has evaluated the role of breast support on landing biomechanics. This study investigates the effect of breast support on joint negative work and joint contributions to total negative work during landing. Thirty-five female athletes performed 5 landing trials in 3 breast support conditions. Lower-extremity joint negative work and relative joint contributions to total negative work were calculated. Univariate analyses of variance were used to determine the effect of breast support on negative joint work values. Increasing levels of breast support were associated with lower ankle negative work (P < .001) and ankle relative contributions (P < .001) and increases in hip negative work (P = .008) and hip relative contributions (P < .001). No changes were observed in total negative work (P = .759), knee negative work (P = .059), or knee contributions to negative work (P = .094). These data demonstrate that the level of breast support affects lower-extremity biomechanics. The distal-to-proximal shift in negative joint work and relative joint contributions may be indicative of a more protective landing strategy for anterior cruciate ligament injuries.

Altered Joint Powers During Running After Tibial Bone Stress Injury

Background:Tibial bone stress injuries (tib-BSI) are common in adolescent runners. Previous research has examined running mechanics as possible risk factors for tib-BSI’s and implications have been observed for both kinematic and kinetic measures. Combining these measures to examine power absorption and production of the lower extremity can provide context on mechanical differences in individuals with a history of tib-BSI.Hypothesis/Purpose:The purpose of this study was to examine total limb power and percent joint contribution in healthy adolescent runners compared to peers with a history of tib-BSI. It was hypothesized that runners with a history of tib-BSI would have a greater contribution of power production and absorption at the ankle, and less at the hip and knee joints, with no difference in total power.Methods:Twenty-six runners were divided into groups: history of tib-BSI (n=14; male=10, female=4; age=16±2) and healthy controls (n=12; male=5, female=7; age=18±7). Data were collected using 3D motion capture with embedded force plates during overground running at self-selected pace. Total limb power and percent joint contribution were calculated from joint work. Positive and negative joint work was summed from the integrations of the joint power-time curve in each plane. Joint work was divided by step-time to obtain total joint power. Joint powers for the hip, knee, and ankle were summed to determine total limb power and percentage of limb power was calculated for each joint. Variables were grouped by control limb (CON), uninvolved limb (UNI), and involved limb (BSI). Both limbs in the healthy controls were averaged to generate the CON group. A one-way ANOVA was used to compare the variables of limb and joint power.Results:There were no significant differences between BSI and UNI limbs for any variables measured. The CON group exhibited significantly greater hip negative power compared to the BSI group (p=0.047), and significantly less ankle negative power compared to the BSI (p=0.001) and UNI groups (p=0.002). Despite a significant difference in total positive power between groups (p=0.04), there were no differences in joint positive power. Variables are presented in Table 1.Conclusion:This study is preliminary evidence that adolescent runners with a history of tib-BSI can present with adaptations in running mechanics that are not limited to the injured leg. Negative power may be more sensitive to change with the ankle increasing its contribution, comparatively. Clinicians and researchers should be aware of this adaptation after injury as it may influence treatment.

Loaded forced-marching shifts mechanical contributions proximally and disrupts stride-to-stride joint work modulation in recruit aged women.

Military personnel in combat roles often perform gait tasks with additional load, which can affect the contributions of joint mechanical work (positive and negative). Furthermore, different locomotion patterns can also affect joint specific work contributions. While mean behavior of joint work is important to understanding gait, changes in joint kinetic modulation, or the regulation/control of stride-to-stride joint work variability is necessary to elucidate locomotor system function. Suboptimal modulation exhibited as a stochastic time-series (large fluctuation followed by an opposite smaller fluctuation) could potentially affect locomotion efficiency and portend injury risk. It remains unclear how the locomotor system responds to a combination of load perturbations and varying locomotion patterns. What are the interactive effects of load magnitude and locomotion pattern on joint positive/negative work and joint work modulation in healthy, active, recruit-aged women? Eleven healthy, active, recruit-aged (18-33 years) women ran and forced-marched (walking at a velocity an individual would typically jog) in bodyweight (BW), an additional 25 % of BW (+25 %BW) and an additional 45 % of BW (+45 %BW) conditions at a velocity above their gait transition velocity. Joint work was calculated as the time integral of joint power. Joint work modulation was assessed with detrended fluctuation analysis (DFA) on consecutive joint work time-series. Joint work contributions shifted proximally for forced-marching demonstrated by lesser (p < .001) positive/negative ankle work but greater (p = .001) positive hip work contributions compared to running. Running exhibited optimal positive ankle work modulation compared to forced-marching (p = .040). Knee and ankle negative joint work modulation was adversely impacted compared to the hip during forced-marching (p < .001). Employing forced-marching gait while under loads of 25 and 45 % of BW reduces the ability of the plantar-flexors and knee extensors to optimally contribute to energy absorption and propulsion in recruit-aged women, potentially reducing metabolic efficiency and increasing injury risk.

Medial gastrocnemius muscle fascicles shorten throughout stance during sprint acceleration.

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.

Lower Extremity Joint Work During Braking Phase Of The Triple Hop For Distance

The triple hop for distance (THD) involves three consecutive single leg hops for maximal horizontal displacement. This task imposes variable mechanical demands challenging balance, coordination and leg strength. While THD is common during late-stage rehabilitation, these demands may also qualify THD as appropriate for healthy athletes. While research shows that energy absorption strategies vary between landing styles, genders and heights, a limitation is the use of a single contact for analysis or training. As a result, changes in landing strategy over repeated landings are not well understood. PURPOSE: To determine changes in sagittal plane joint energetic landing strategy during each contact of THD. METHODS: Nine female college soccer players performed THD on the dominant limb. Ground reaction forces and lower extremity kinematics were measured using a force platform (1200Hz) and 9-camera motion capture system (240Hz). Three trials were collected of each contact in the THD sequence. Negative joint work was calculated as negative joint power integrated with respect to time. Total negative joint work (TJW) is the sum of eccentric work done on the hip, knee, and ankle, and the proportion of TJW done on each joint was defined as relative negative joint work (RJW). RESULTS: TJW increased from the first (-80.5 ± 26.3J) to the second (-95.5 ± 33.7J), and third (-145.2 ± 42.5J) landings. From the first to second contacts, RJW done on the ankle (33.5% vs 34.7%, d = 0.10), knee (53.9% vs 52.1%, d = 0.20), and hip (12.6% vs 13.1%, d = 0.08) was unchanged. From the second to third contacts, RJW done on the ankle was substantially decreased (34.7% vs 18.4%, d = 1.67), while RJW done on the hip was substantially increased (13.1% vs 25.4%, d = 1.68). RJW done on the knee was modestly greater (52.1% vs 56.3%, d = 0.54) in the second compared to third contacts in THD sequence. CONCLUSION: The serial nature of THD requires athletes to adapt to different demands in each ground contact. This includes progressively greater braking forces and landing strategy modulation during each contact. This represents a task which exposes athletes to variable demands of both ground reaction forces and joint work in a controlled manner. THD may therefore address multiple athletic performance qualities during performance enhancement and rehabilitation.

Muscular Not Skeletal Components Of Leg Stiffness Are Significantly Correlated With Associated Biomechanical Variables During Running

Muscular (kMusc) and skeletal (kSkel) components of leg stiffness have been previously related to injury patterns in runners [1]. Though these components mirror proposed injury mechanisms in runners, their relationship to underlying biomechanical variables remains unclear. PURPOSE: to evaluate the association between components of leg stiffness (kMusc & kSkel) with common biomechanical variables of muscular (joint work) and skeletal loading (joint reaction forces) during a running task. METHODS: Thirteen recreational runners (8 male, 5 female) performed ten over ground running trials at 3.35 m/s (±5%) in each of four conditions with varying shoe and strike patterns. Kinematics and ground reaction forces (GRFs) were recorded using an 8-camera motion capture system (240 Hz, Qualisys) and force platform (1200 Hz, OR-7, AMTI). Visual3D (C-Motion) was used to calculate joint powers and compressive joint reaction forces (JRFs). MATLAB was used to calculate negative joint work values and stiffness variables. kMusc and kSkel were calculated as previously reported [1]. Prism 8.0 (GraphPad) was used to perform correlation analyses between muscular and skeletal contributions to load attenuation. RESULTS: kMusc had moderate and weak relationships with lower extremity work (p < 0.01; r = 0.55) and knee joint work (p = 0.01; r = 0.32). Weak correlations existed between kSkel and ankle (p = 0.25; r = -0.10), knee (p = 0.17; r = 0.14) and hip joint reaction forces (p = 0.46; r = 0.01). CONCLUSIONS: These data revealed moderate associations between kMusc and negative work values suggesting that kMusc is proportional to muscular contributions to load attenuation. JRFs had weak associations with kSkel, suggesting kSkel may not represent skeletal loading. These findings suggest this simplistic model may be insufficient to describe muscular and skeletal contributions to load attenuation. [1] Powell, Paquette & Williams, 2017.

How age and surface inclination affect joint moment strategies to accelerate and decelerate individual leg joints during walking

A joint moment also causes motion at other joints of the body. This joint coupling-perspective allows more insight into two age-related phenomena during gait. First, whether increased hip kinetic output compensates for decreased ankle kinetic output during positive joint work. Second, whether preserved joint kinetic patterns during negative joint work in older age have any functional implication. Therefore, we examined how age and surface inclination affect joint moment strategies to accelerate and/or decelerate individual leg joints during walking. Healthy young (age: 22.5 ± 4.1 years, n = 18) and older (age: 76.0 ± 5.7 years, n = 22) adults walked at 1.4 m/s on a split-belt instrumented treadmill at three grades (0%, 10%, −10%). Lower-extremity moment-induced angular accelerations were calculated for the hip (0% and 10%) and knee (0% and −10%) joints. During level and uphill walking, both age groups showed comparable ankle moment-induced ipsilateral (p = 0.774) and contralateral (p = 0.047) hip accelerations, although older adults generated lower ankle moments in late stance. However, ankle moment-induced contralateral hip accelerations were smaller (p = 0.001) in an older adult subgroup (n = 13) who showed larger hip extension moments in early stance than young adults. During level and downhill walking, leg joint moment-induced knee accelerations were unaffected by age (all p > 0.05). These findings suggest that during level and uphill walking increased hip flexor mechanical output in older adults does not arise from reduced ankle moments, contrary to increased hip extensor mechanical output. Additionally, results during level and downhill walking imply that preserved eccentric knee extensor function is important in maintaining knee stabilization in older age.

Altered Lower Extremity Joint Work Profiles During Inclined Running At Iso-efficiency Speeds

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.

Lower extremity stiffness when running in minimalist, traditional, and ultra-cushioning shoes

Differences in running mechanics between minimalist (MIN) and traditional (TRAD) running shoes have been the subject of much research in the last decade. More recently, ultra-cushioning (ULTRA) shoes featuring oversized midsoles have emerged and are growing in popularity. However, relatively little is known regarding how ULTRA shoes effect running mechanics. Therefore, the purpose of this study was to compare foot strike, leg stiffness, joint stiffness, and negative joint work when running in MIN, TRAD, and ULTRA shoes. Fifteen recreational runners ran on an instrumented treadmill in each shoe while their whole body kinematics were recorded using a 12-camera motion capture system. Foot strike pattern was quantified using the strike index (SI) and foot strike angle (FSA). Leg stiffness was calculated using a spring-mass model. Joint stiffness was calculated as change in joint moment relative to change in joint angle during the absorption period. Negative joint work was calculated by integrating the negative portion of the joint power curve. Differences between shoes were evaluated using a one-way repeated measures ANOVA. Results showed there were no differences between MIN and TRAD shoes for any of the dependent variables. In the ULTRA shoe, participants used a more pronounced rearfoot strike pattern. There were no differences in leg stiffness between shoes. Compared to the MIN and TRAD shoes, in the ULTRA shoes the ankle was stiffer and performed less negative work while the knee and hip were less stiff and performed more negative work. These findings suggest a reorganization of the neuromuscular control of the limb when running in ULTRA compared to MIN or TRAD shoes. This reorganization may have implications for running performance or injury prevention.

Between-limb differences in running technique induces asymmetric negative joint work during running

Negative work, which is mainly generated by eccentric muscle contraction, has an important influence on the associated muscle damage. Generally, mechanical parameters are determined for one side of a lower extremity on the assumption of negligible between-limb differences. However, between-limb differences in the negative work of lower extremity joints during running remain unclear. This study examines between-limb differences in negative work and associated mechanical parameters during the contact phase of running. Twenty-five young adult males voluntarily participated in this study. Each participant was asked to run on a straight runway at a speed of 3.0 m s−1. Negative work, amplitude, duration of negative power, moment, and angular velocity were computed for both sides of the lower extremities. Significant differences were found in negative work between limbs for the hip (18.9 ± 11.7%), knee (13.6 ± 10.4%), and ankle (11.8 ± 8.5%) joints. For the hip joint, asymmetric negative work was attributable to the between-limb difference in the amplitude of negative power owing to a corresponding difference in the moment. The between-limb differences concerning the duration and amplitude of negative power could explain the asymmetric negative work in the knee joint. The asymmetric negative work of the ankle joint was attributable to the between-limb difference in the amplitude and duration of the negative power and the moment. These results indicate that asymmetric negative work was generated in each lower extremity joint; however, the major mechanical parameters corresponding to the negative work are not the same across the joints.

Advanced Age Redistributes Positive but Not Negative Leg Joint Work during Walking.

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.

Compensations in lower limb joint work during walking in response to unilateral calf muscle weakness

BackgroundPatients with calf muscle weakness due to neuromuscular disorders have a reduced ankle push-off work, which leads to increased energy dissipation at contralateral heel-strike. Consequently, compensatory positive work needs to be generated, which is mechanically less efficient. It is unknown whether neuromuscular disorder patients compensate with their ipsilateral hip and/or contralateral leg; and if such compensatory joint work is related to walking energy cost. Research questionDo patients with calf muscle weakness compensate for the increase in negative joint work by increasing positive ipsilateral hip work and/or positive contralateral leg work? And is the total mechanical work related with walking energy cost? MethodsSeventeen patients with unilateral flaccid calf muscle weakness and 10 healthy individuals performed the following two tests: i) a barefoot 3D gait analysis at comfortable speed and matched control speed (i.e. 0.4 non-dimensional) to assess lower limb joint work and ii) a 6-minute walk test at comfortable speed to assess walking energy cost. ResultsPatients had a lower comfortable walking speed compared to healthy individuals (1.05 vs 1.36 m/s, p < 0.001) and did not increase positive lower limb joint work at comfortable speed. At matched speed (1.25 m/s), patients showed increased positive work at their ipsilateral hip (0.38 ± 0.08 vs 0.27 ± 0.07, p = 0.001) and/or contralateral leg (0.99 ± 0.14 vs 0.69 ± 0.14, p < 0.001). Patients with weakest plantar flexors used both strategies. No relation between total positive work and walking energy cost was found (r = 0.43, p = 0.122). SignificancePatients with unilateral calf muscle weakness compensated for reduced ankle push-off work by lowering their comfortable walking speed or, at matched speed, by generating additional positive joint work at the ipsilateral hip and/or contralateral leg. The additional positive joint work at matched speed did not explain the elevated walking energy cost at comfortable speed, which needs further exploration.

Gait biomechanics of skipping are substantially different than those of running

The inherit injury risk associated with high-impact exercises calls for alternative ways to achieve the benefits of aerobic exercise while minimizing excessive stresses to body tissues. Skipping presents such an alternative, incorporating double support, flight, and single support phases. We used ground reaction forces (GRFs), lower extremity joint torques and powers to compare skipping and running in 20 healthy adults. The two consecutive skipping steps on each limb differed significantly from each other, and from running. Running had the longest step length, the highest peak vertical GRF, peak knee extensor torque, and peak knee negative and positive power and negative and positive work. Skipping had the greater cadence, peak horizontal GRF, peak hip and ankle extensor torques, peak ankle negative power and work, and peak ankle positive power. The second vs first skipping step had the shorter step length, higher cadence, peak horizontal GRF, peak ankle extensor torque, and peak ankle negative power, negative work, and positive power and positive work. The first skipping step utilized predominately net negative joint work (eccentric muscle action) while the second utilized predominately net positive joint work (concentric muscle action). The skipping data further highlight the persistence of net negative work performed at the knee and net positive work performed at the ankle across locomotion gaits. Evidence of step segregation was seen in distribution of the braking and propelling impulses and net work produced across the hip, knee, and ankle joints. ConclusionsSkipping was substantially different than running and was temporally and spatially asymmetrical with successive foot falls partitioned into a dominant function, either braking or propelling whereas running had a single, repeated step in which both braking and propelling actions were performed equally.

Lower limb joint work and joint work contribution during downhill and uphill walking at different inclinations

Work performance and individual joint contribution to total work are important information for creating training protocols, but were not assessed so far for sloped walking. Therefore, the purpose of this study was to analyze lower limb joint work and joint contribution of the hip, knee and ankle to total lower limb work during sloped walking in a healthy population. Eighteen male participants (27.0±4.7yrs, 1.80±0.05m, 74.5±8.2kg) walked on an instrumented ramp at inclination angles of 0°, ±6°, ±12° and ±18° at 1.1m/s. Kinematic and kinetic data were captured using a motion-capture system (Vicon) and two force plates (AMTI). Joint power curves, joint work (positive, negative, absolute) and each joint’s contribution to total lower limb work were analyzed throughout the stance phase using an ANOVA with repeated measures. With increasing inclination positive joint work increased for the ankle and hip joint and in total during uphill walking. Negative joint work increased for each joint and in total work during downhill walking. Absolute work was increased during both uphill (all joints) and downhill (ankle & knee) walking. Knee joint contribution to total negative and absolute work increased during downhill walking while hip and ankle contributions decreased. This study identified, that, when switching from level to a 6° and from 6° to a 12° inclination the gain of individual joint work is more pronounced compared to switching from 12° to an 18° inclination. The results might be used for training recommendations and specific training intervention with respect to sloped walking.

Lower Extremity Joint Work During Acceleration, Deceleration, and Steady State Running.

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.

Absolute And Relative Joint Contributions To Landing In High- Compared To Low-Arched Athletes

Foot structure has been implicated in lower extremity injury. Research has shown that athletes with aberrant foot structure exhibit unique biomechanics during running and landing tasks. While foot function has been suggested to underlie distinct injury patterns in high- (HA) compared to low-arched (LA) athletes, no previous research has addressed the contribution of individual joints to load attenuation in a landing task. PURPOSE: Therefore, the purpose of this study was to quantify differences in individual joint contributions to total negative work during a landing task in high- compared to low-arched athletes. METHODS: Ten HA and 10 LA female athletes performed five landing trials from a height of 0.3 meters while three-dimensional kinematics and ground reaction forces were collected using an 8-camera motion capture system (240 Hz, ViconPEAK) and a force platform (960 Hz, AMTI), respectively. Lower extremity joint work values were calculated using Visual 3D (C-Motion, Inc.). Relative contributions of each joint to negative joint work was calculated as a percentage of the individual joint work relative to total joint work. Independent samples t-tests were used to compare relative joint work values for the lower extremity. RESULTS: HA athletes exhibited significantly smaller total negative joint work compared to LA athletes (p=0.016; HA: 1.79±0.43; LA: 2.16±0.26). HA athletes had significantly smaller knee (p=0.046; HA: 0.98±0.36; LA: 1.22±0.23) and hip joint work values (p=0.019; HA: 0.22±0.18; LA: 0.39±0.16). HA and LA athletes had similar ankle joint work values (p=0.252; HA: 0.59±0.16; LA: 0.55±0.12). When comparing relative joint work, HA athletes exhibited greater relative ankle contributions to total negative work than LA athletes (p = 0.032; HA: 35.1±25.7%; LA: 25.7±6.6%). No differences existed between HA and LA athletes at the knee (p=0.255; HA: 53.5±11.2%; LA: 56.3±6.3%). HA athletes had a smaller hip contribution to total negative work than the LA athletes during landing (p = 0.049; 11.4±8.8%; LA: 18.0±7.6%). CONCLUSIONS: These findings indicate that HA and LA athletes use unique biomechanical strategies to attenuate load during a landing task and may provide insight into the distinct injury patterns experienced by these two groups.

Increased delivery stride length places greater loads on the ankle joint in elite male cricket fast bowlers

The purpose of this study was to investigate the effect stride length has on ankle biomechanics of the leading leg with reference to the potential risk of injury in cricket fast bowlers. Ankle joint kinematic and kinetic data were collected from 51 male fast bowlers during the stance phase of the final delivery stride. The bowling cohort comprised national under-19, first class and international-level athletes. Bowlers were placed into either Short, Average or Long groups based on final stride length, allowing statistical differences to be measured. A multivariate analysis of variance with a Bonferroni post-hoc correction (α = 0.05) revealed significant differences between peak plantarflexion angles (Short-Long P = 0.005, Average and Long P = 0.04) and negative joint work (Average-Long P = 0.026). This study highlighted that during fast bowling the ankle joint of the leading leg experiences high forces under wide ranges of movement. As stride length increases, greater amounts of negative work and plantarflexion are experienced. These increases place greater loads on the ankle joint and move the foot into positions that make it more susceptible to injuries such as posterior impingement syndrome.