Hip Work Research Articles

Does increased midsole bending stiffness of sport shoes redistribute lower limb joint work during running?

ObjectivesTo investigate if lower limb joint work is redistributed when running in a shoe with increased midsole bending stiffness compared to a control shoe. DesignWithin-subject with two conditions: (1) commercially available running shoe and (2) the same shoe with carbon fibre inserts to increase midsole bending stiffness. MethodsThirteen male, recreational runners ran on an instrumented treadmill at 3.5m/s in each of the two shoe conditions while motion capture and force platform data were collected. Positive and negative metatarsophalangeal (MTP), ankle, knee, and hip joint work were calculated and statistically compared between conditions. ResultsRunning in the stiff condition (with carbon fibre inserts) resulted in significantly more positive work and less negative work at the MTP joint, and less positive work at the knee joint. ConclusionsIncreased midsole bending stiffness resulted in a redistribution of positive lower limb joint work from the knee to the MTP joint. A larger MTP joint plantarflexor moment due to increased vGRF at the instant of peak positive power and an earlier onset of MTP joint plantarflexion velocity were identified as the reasons for lower limb joint work redistribution.

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.

The relative contributions of sagittal, frontal, and transverse joint works to self-paced incline and decline slope walking

Positive and negative work are generated at the lower limb joints in order to locomote over various terrains. Joint work quantifies the changes in energy that are necessary to adapt gait to environmental demands. The aim of this study was to quantify 3D joint work at the hip, knee, and ankle during slope walking. Work was calculated for ten males (23.9 ± 1.1 years) walking at a self-selected speed on inclines and declines (−20, −12, −6, 0, 6, 12, 20 degrees). Sagittal positive work significantly increased at the hip, knee, and ankle for incline walking (for example, hip positive work increased 153%, 280%, and 453% for 6, 12, and 20 degrees, respectively; knee and ankle positive work also increased) (p ≤ 0.05), in order to raise and propel the body forward. Sagittal negative work increased significantly at the hip, knee and ankle for decline walking (for example, knee negative work increased 193%, 355%, and 496% for −6, −12, and −20 degrees, respectively; hip and ankle negative work also increased) (p ≤ 0.05), in order to control body descent. These substantial changes in work will be especially challenging for people with compromised strength due to age and disease. Furthermore, changes in work were not limited to the sagittal plane: 46% of the total hip joint work occurred in the frontal and transverse planes for six degree decline walking. Thus, decline walking placed greater demands on the hip ab/adductors and rotators, and this may be related to the greater risk of falls observed for descent versus ascent.

Positive Work Contribution Shifts from Distal to Proximal Joints during a Prolonged Run.

To investigate the joint-specific contributions to the total lower-extremity joint work during a prolonged fatiguing run. Recreational long-distance runners (n = 13) and competitive long-distance runners (n = 12) performed a 10-km treadmill run with near-maximal effort. A three-dimensional motion capture system synchronized with a force-instrumented treadmill was used to calculate joint kinetics and kinematics of the lower extremity in the sagittal plane during the stance phase at 13 distance points over the 10-km run. A significant (P < 0.05) decrease of positive ankle joint work as well as an increase of positive knee and hip joint work was found. These findings were associated with a redistribution of the individual contributions to total lower-extremity work away from the ankle toward the knee and hip joint which was more distinctive in the recreational runner group than in the competitive runner group. This redistribution was accomplished by significant (P < 0.05) reductions of the external ground-reaction force lever arm and joint torque at the ankle and by the significant (P < 0.05) increase of the external ground-reaction force lever arm and joint torque at the knee and hip. The redistribution of joint work from the ankle to more proximal joints might be a biomechanical mechanism that could partly explain the decreased running economy in a prolonged fatiguing run. This might be because muscle-tendon units crossing proximal joints are less equipped for energy storage and return compared with ankle plantar flexors and require greater muscle volume activation for a given force. To improve running performance, long-distance runners may benefit from an exercise-induced enhancement of ankle plantar flexor muscle-tendon unit capacities.

The contributions of ankle, knee and hip joint work to individual leg work change during uphill and downhill walking over a range of speeds.

The muscles surrounding the ankle, knee and hip joints provide 42, 16 and 42%, respectively, of the total leg positive power required to walk on level ground at various speeds. However, each joint's contribution to leg work when walking up/downhill at a range of speeds is not known. Determining each biological joint's contribution to leg work over a range of speeds and slopes can inform the design of biomimetic assistive devices (i.e. prostheses). Twenty healthy adults walked 1.00, 1.25 and 1.50 m s−1 on 0°, ±3°, ±6° and ±9° while we collected kinematic and kinetic data. We calculated sagittal plane joint work and individual leg work over the entire stance phase. The ratio of ankle joint to total individual leg positive work (summed ankle, knee and hip joint work) did not change (0.42) with speed or slope, but the ratio of ankle joint to individual leg negative work was 0.38 at −9°, 0.42 at 0° and 0.27 at +9° across all speeds. The ratio of ankle joint to total individual leg negative work was 0.41 at 1.00 m s−1 and 0.32 at 1.50 m s−1 across all slopes. The ratio of knee joint to total individual positive leg work (0.22) did not change with speed or slope. The ratio of knee joint to total individual leg negative work was 0.39 at 1.00 m s−1 and 0.45 at 1.50 m s−1 across all slopes. The ratio of hip joint to total individual leg positive work did not change with speed but was 0.34 at −9°, 0.33 at 0° and 0.37 at +9° across all speeds. The ratio of hip joint to total individual leg negative work was 0.21 at 1.00 m s−1, and 0.24 at 1.50 m s−1 across all slopes and 0.17 at −9°, 0.19 at 0° and 0.29 at +9° across all speeds. The ankle significantly contributes to walking on slopes and this contribution changes during sloped compared with level-ground walking, thus assistive devices that provide biomimetic ankle function must adapt to accommodate walking at different speeds and slopes; whereas assistive biomimetic devices for the knee only need to adapt at different speeds.

Hip recovery strategy used by below-knee amputees following mediolateral foot perturbations

Lower-limb amputees have a higher risk of falling compared to non-amputees. Proper regulation of whole-body angular momentum is necessary to prevent falls, particularly in the frontal plane where individuals are most unstable. However, the balance recovery mechanisms used by lower-limb amputees when recovering from a perturbation are not well-understood. This study sought to understand the balance recovery mechanisms used by lower-limb amputees in response to mediolateral foot perturbations by examining changes to frontal plane whole-body angular momentum and hip joint work. These metrics provide a quantitative measure of frontal plane dynamic balance and associated joint contributions required to maintain balance during gait. Nine amputees and 11 non-amputees participated in this study where an unexpected medial or lateral foot placement perturbation occurred immediately prior to heel strike on the residual, sound or non-amputee limbs. Lateral perturbations of all limbs resulted in a reduced range of whole-body angular momentum and increased positive frontal plane hip work in the first half of single limb support. Medial perturbations for all limbs resulted in increased range of whole-body angular momentum and decreased positive frontal plane hip work, also in the first half of single limb support. These results suggest that medial foot placement perturbations are particularly challenging and that hip strategies play an important role in balance recovery. Thus, rehabilitation interventions that focus on hip muscles that regulate mediolateral balance, particularly the hip abductors, and the use of prostheses with active ankle control, may reduce the risk of falls.

Individual Leg and Joint Work during Sloped Walking for People with a Transtibial Amputation Using Passive and Powered Prostheses

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.

Mechanical Demands of the Hang Power Clean and Jump Shrug: A Joint-Level Perspective.

Kipp, K, Malloy, PJ, Smith, J, Giordanelli, MD, Kiely, MT, Geiser, CF, and Suchomel, TJ. Mechanical demands of the hang power clean and jump shrug: a joint-level perspective. J Strength Cond Res 32(2): 466-474, 2018-The purpose of this study was to investigate the joint- and load-dependent changes in the mechanical demands of the lower extremity joints during the hang power clean (HPC) and the jump shrug (JS). Fifteen male lacrosse players were recruited from a National Collegiate Athletic Association DI team, and completed 3 sets of the HPC and JS at 30, 50, and 70% of their HPC 1 repetition maximum (1RM HPC) in a counterbalanced and randomized order. Motion analysis and force plate technology were used to calculate the positive work, propulsive phase duration, and peak concentric power at the hip, knee, and ankle joints. Separate 3-way analysis of variances were used to determine the interaction and main effects of joint, load, and lift type on the 3 dependent variables. The results indicated that the mechanics during the HPC and JS exhibit joint-, load-, and lift-dependent behavior. When averaged across joints, the positive work during both lifts increased progressively with external load, but was greater during the JS at 30 and 50% of 1RM HPC than during the HPC. The JS was also characterized by greater hip and knee work when averaged across loads. The joint-averaged propulsive phase duration was lower at 30% than at 50 and 70% of 1RM HPC for both lifts. Furthermore, the load-averaged propulsive phase duration was greater for the hip than the knee and ankle joint. The joint-averaged peak concentric power was the greatest at 70% of 1RM for the HPC and at 30%-50% of 1RM for the JS. In addition, the joint-averaged peak concentric power of the JS was greater than that of the HPC. Furthermore, the load-averaged peak knee and ankle concentric joint powers were greater during the execution of the JS than the HPC. However, the load-averaged power of all joints differed only during the HPC, but was similar between the hip and knee joints for the JS. Collectively, these results indicate that compared with the HPC the JS is characterized by greater hip and knee positive joint work, and greater knee and ankle peak concentric joint power, especially if performed at 30 and 50% of 1RM HPC. This study provides important novel information about the mechanical demands of 2 commonly used exercises and should be considered in the design of resistance training programs that aim to improve the explosiveness of the lower extremity joints.

Joint dynamics and intra-subject variability during countermovement jumps in children and adults

The present study investigated lower limb joint work, lower limb joint energy transport and intra-subject variation of the joint dynamics during countermovement jumps in children and adults. Twelve healthy men and eleven healthy boys performed ten maximal countermovement jumps. Three dimensional kinematics and kinetics were recorded in synchrony. Hip, knee and ankle joint eccentric and concentric work, joint energy transfer, intra-subject variation of joint moment, joint power and joint moment components were calculated. The children had lower eccentric and concentric hip work and lower eccentric knee work but no group difference was observed in the concentric knee joint work and ankle joint work. Eccentric hip and knee joint energy transfer and concentric hip joint energy transfer were higher in adults. The children had higher intra-subject variation in the eccentric and concentric hip joint work, hip joint moment and hip and knee joint power. Higher intra-subject variation was observed in horizontal joint reaction force components for the children and higher intra-subject variation in the segment angular inertia components was observed for the adults. The joint dynamics of children during countermovement jumps were less efficient in producing proximal joint work, transferring energy through joint centres and characterized by a higher intra-subject variation.

Comparison of lower limb kinetics during vertical jumps in turnout and neutral foot positions by classical ballet dancers

The purpose of this study was to investigate the effect of hip external rotation (turnout) on lower limb kinetics during vertical jumps by classical ballet dancers. Vertical jumps in a turnout (TJ) and a neutral hip position (NJ) performed by 12 classical female ballet dancers were analysed through motion capture, recording of the ground reaction forces, and inverse dynamics analysis. At push-off, the lower trunk leaned forward 18.2° and 20.1° in the TJ and NJ, respectively. The dancers jumped lower in the TJ than in the NJ. The knee extensor and hip abductor torques were smaller, whereas the hip external rotator torque was larger in the TJ than in the NJ. The work done by the hip joint moments in the sagittal plane was 0.28 J/(Body mass*Height) and 0.33 J/(Body mass*Height) in the TJ and NJ, respectively. The joint work done by the lower limbs were not different between the two jumps. These differences resulted from different planes in which the lower limb flexion–extension occurred, i.e. in the sagittal or frontal plane. This would prevent the forward lean of the trunk by decreasing the hip joint work in the sagittal plane and reduce the knee extensor torque in the jump.

Arch structure is associated with unique joint work, relative joint contributions and stiffness during landing

To examine lower extremity joint contributions to a landing task in high-(HA) and low-arched (LA) female athletes by quantifying vertical stiffness, joint work and relative joint contributions to landing. MethodsTwenty healthy female recreational athletes (10 HA and 10 LA) performed five barefoot drop landings from a height of 30cm. Three-dimensional kinematics (240Hz) and ground reaction forces (960Hz) were recorded simultaneously. Vertical stiffness, joint work values and relative joint work values were calculated using Visual 3D and MatLab. ResultsHA athletes had significantly greater vertical stiffness compared to LA athletes (p=0.013). Though no differences in ankle joint work were observed (p=0.252), HA athletes had smaller magnitudes of knee (p=0.046), hip (p=0.019) and total lower extremity joint work values (p=0.016) compared to LA athletes. HA athletes had greater relative contributions of the ankle (p=0.032) and smaller relative contributions of the hip (p=0.049) compared to LA athletes. No differences in relative contributions of the knee were observed (p=0.255). ConclusionsThese findings demonstrate that aberrant foot structure is associated with unique contributions of lower extremity joints to load attenuation during landing. These data may provide insight into the unique injury mechanisms associated with arch height in female athletes.

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.

Novel Kinetic Strategies Adopted in Asymmetric Split-Belt Treadmill Walking

ABSTRACTThe hip and ankle strategies that affect learning of a novel gait have not been fully determined, and could be of importance in design of clinical gait interventions. The authors' purpose was to determine the effects of asymmetric split-belt treadmill walking on ankle and hip work during propulsion. Participants were randomized into either a gradual training group or a sudden training group and later returned for a retention test. The gradual training group performed significantly more work at the hip joint of the slow limb during acquisition, and decreased the hip joint work performed during retention. These findings reveal the hip joint on the slow limb during initial swing as a possible site of adaptation to a novel locomotor pattern.

Biomechanical energetic analysis of technique during learning the longswing on the high bar

Biomechanical energetic analysis of technique can be performed to identify limits or constraints to performance outcome at the level of joint work, and to assess the mechanical efficiency of techniques. The aim of this study was to investigate the biomechanical energetic processes during learning the longswing on the high bar. Twelve male, novice participants took part in a training study. Kinematic and kinetics data were collected during swing attempts in eight weekly testing sessions. Inverse dynamics analysis was performed from known zero forces at the toes. Joint work, total energy, and bar energy were calculated. Biomechanical constraints to action, that is, limits to novice performance, were identified as “total work” and “shoulder work”. The most biomechanically efficient technique was associated with an onset of the hip functional phase and joint work that occurred between 10–45° before the bottom of the swing. The learning of gross motor skills is realised through the establishment of a set of techniques with task specific biomechanical constraints. Knowledge of the biomechanical constraints to action associated with more effective and efficient techniques will be useful for both assessing learning and establishing effective learning interventions.

Asymmetries in joint work during multi‐joint movement after anterior cruciate ligament reconstruction: A pilot study

After anterior cruciate ligament reconstruction (ACL-R), many studies have reported a deficit of performance on the injured leg during multi-joint tasks. However, the total mechanical joint work (WTotal ), parameter best related to the vertical displacement of the body mass center during vertical jumping, has not yet been studied. The aim of this research was to compare asymmetries between ACL-R subjects and healthy matched subjects, through the analysis of the kinematics and kinetics during a single-leg squat jump. Asymmetries are defined by the Limb Symmetry Index (LSI). A greater LSI was observed for WTotal in the ACL-R group than in the healthy group. There was no difference in LSI for knee joint work between the two groups, while the LSI for hip and ankle joint work was significantly larger in the ACL-R group. This was explained by greater LSI for the hip and ankle joint range of motion in the ACL-R group than in the healthy group. After ACL-R, patients exhibited greater asymmetries than healthy subjects during single-leg squat jump. Physiotherapists should focus on quality execution of multi-joint movement, especially on hip and ankle joints range of motion in order to reduce asymmetries and to improve vertical jumping performance.

Walking speed related joint kinetic alterations in trans-tibial amputees: impact of hydraulic 'ankle’ damping

BackgroundPassive prosthetic devices are set up to provide optimal function at customary walking speed and thus may function less effectively at other speeds. This partly explains why joint kinetic adaptations become more apparent in lower-limb amputees when walking at speeds other than customary. The present study determined whether a trans-tibial prosthesis incorporating a dynamic-response foot that was attached to the shank via an articulating hydraulic device (hyA-F) lessened speed-related adaptations in joint kinetics compared to when the foot was attached via a rigid, non-articulating attachment (rigF).MethodsEight active unilateral trans-tibial amputees completed walking trials at their customary walking speed, and at speeds they deemed to be slow-comfortable and fast-comfortable whilst using each type of foot attachment. Moments and powers at the distal end of the prosthetic shank and at the intact joints of both limbs were compared between attachment conditions.ResultsThere was no change in the amount of intact-limb ankle work across speed or attachment conditions. As speed level increased there was an increase on both limbs in the amount of hip and knee joint work done, and increases on the prosthetic side were greater when using the hyA-F. However, because all walking speed levels were higher when using the hyA-F, the intact-limb ankle and combined joints work per meter travelled were significantly lower; particularly so at the customary speed level. This was the case despite the hyA-F dissipating more energy during stance. In addition, the amount of eccentric work done per meter travelled became increased at the residual knee when using the hyA-F, with increases again greatest at customary speed.ConclusionsFindings indicate that a trans-tibial prosthesis incorporating a dynamic-response foot reduced speed-related changes in compensatory intact-limb joint kinetics when the foot was attached via an articulating hydraulic device compared to rigid attachment. As differences between attachment conditions were greatest at customary speed, findings indicate a hydraulic ankle-foot device is most effectual at the speed it is set-up for.

Effect of arm swing on effective energy during vertical jumping: Experimental and simulation study

Arm swing helps to increase vertical jump height (VJH), in part by a greater hip joint muscle work. The force-velocity relationship has been put forward to explain the increase in hip joint work. Nevertheless, the efficacy ratio, muscle shortening length, and active state might be parameters that affect the effective energy and then VJH. The purpose of this study was to evaluate the influence of arm swing on effective energy in vertical jumping. Eight subjects performed maximal squat jumps with (SJ arm ) and without arm swing (SJ). A simulation model of the musculo-skeletal system was applied. For subjects and simulation, VJH was about 20% higher during SJ arm. In subjects, this was explained by the shoulder joint work (34%) and an increase of L5-S1 joint work (66%). In simulated jump, effective energy increase during SJ arm (+80.74 J) was related to an improvement of the total muscle work and not to the efficacy ratio. The increase in total muscle work was due to anterior deltoid work and to greater erector spinae, biceps femoris, and gluteus work. The greater muscle works were explained by a slower shortening velocity for all the muscles and by a greater shortening length and active state for the biceps femoris.

片脚および両脚リバウンドジャンプにおける3 次元的な力発揮特性の相違

This study aimed to clarify the 3-dimensional joint kinetics of the takeoff leg for the single-leg rebound jump (SRJ) and the double-leg rebound jump (DRJ). 14 male track and field athletes (sprinters, jumpers and decathletes) performed the SRJ and the DRJ with maximal effort. Kinematics and kinetics data were recorded using a Vicon T20 system (250 Hz) and force platforms (1000 Hz). The results of all the analyses were as follows: 1. In the SRJ, hip joint work around the adduction-abduction and internal-external rotation axes was higher than in the DRJ, because of larger hip abduction and internal rotational torque in the SRJ. 2. In the SRJ, hip abduction and internal rotation torque were larger than those in the DRJ. These may have been caused by the anatomical and mechanical differences between the SRJ and DRJ. 3. In the SRJ, hip abduction torque affected the increment in jump height. This result suggests that hip abduction torque affects the higher jump height for a single leg to a greater extent in the SRJ than in the DRJ. 4. In the SRJ, the trunk lateral flexion caused by trunk flexion torque reduced the lateral displacement of the center of gravity due to pelvic list. These results suggest that 1) the SRJ is an effective training tool for improvement of technique and force output ability for prioritization of power output at the hip internal rotators, especially the hip abductors in addition to the hip extensor, and 2) hip abduction torque in the SRJ has a role in both postural control and determining the increment in jump height. These findings will be useful for clarifying the most pertinent points related to the SRJ and for developing an effective method that can be applied to plyometrics.

Measurement of Pelvic Motion Is a Prerequisite for Accurate Estimation of Hip Joint Work in Maximum Height Squat Jumping

In experiments investigating vertical squat jumping, the HAT segment is typically defined as a line drawn from the hip to some point proximally on the upper body (eg, the neck, the acromion), and the hip joint as the angle between this line and the upper legs (θUL-HAT). In reality, the hip joint is the angle between the pelvis and the upper legs (θUL-pelvis). This study aimed to estimate to what extent hip joint definition affects hip joint work in maximal squat jumping. Moreover, the initial pelvic tilt was manipulated to maximize the difference in hip joint work as a function of hip joint definition. Twenty-two male athletes performed maximum effort squat jumps in three different initial pelvic tilt conditions: backward (pelvisB), neutral (pelvisN), and forward (pelvisF). Hip joint work was calculated by integrating the hip net joint torque with respect to θUL-HAT (WUL-HAT) or with respect to θUL-pelvis (WUL-pelvis). θUL-HAT was greater than θUL-pelvis in all conditions. WUL-HAT overestimated WULpelvis by 33%, 39%, and 49% in conditions pelvisF, pelvisN, and pelvisB, respectively. It was concluded that θUL-pelvis should be measured when the mechanical output of hip extensor muscles is estimated.

Kinetic features of sliding walk in Nogaku

Objectives: To investigate the kinetic features of sliding walk in Nogaku. Design: Biomechanical motion analysis study. Methods: Three male Nogaku actors participated in the experiment. Each actor performed the sliding walk on an 8-m walking track three times. To obtain the kinematics and kinetics, a three-dimensional optical motion capture system and two force platforms were used. The angles, moments, powers and work of each of the three lower extremity joints (i.e.,hip, knee, and ankle joints) in the sagittal plane were calculated using an inverse dynamics method. Results: The kinematic and kinetic results were successfully obtained. In the results for the vertical ground reaction force,one cycle could be clearly divided into two phases (stance and foot-sliding phases). The push force during the foot sliding phase reached 53 N on average. The energy dissipation by the push force (friction energy dissipation) reached 14 J, which was comparable to the hip joint work (19.7 J). Conclusion: The following three findings were revealed: (1) The push force during the foot-sliding phase was large (average 53 N). (2) The role of the hip joint was to propel the actor's body forward. The role of the knee and ankle joints was to keep the center of gravity of the actor's body low. (3) The differences in kinetic results among the actors were larger than the differences in kinematic results.