Crossover Turn Research Articles

The Estimation of Knee Medial Force with Substitution Parameters during Walking and Turning.

Knee adduction, flexion moment, and adduction angle are often used as surrogate parameters of knee medial force. To verify whether these parameters are suitable as surrogates under different walking states, we investigated the correlation between knee medial loading with the surrogates during walking and turning. Sixteen healthy subjects were recruited to complete straight walk (SW), step turn (ST), and crossover turn (CT). Knee joint moments were obtained using inverse dynamics, and knee medial force was computed using a previously validated musculoskeletal model, Freebody. Linear regression was used to predict the peak of knee medial force with the peaks of the surrogate parameters and walking speed. There was no significant difference in walking speed among these three tasks. The peak knee adduction moment (pKAM) was a significant predictor of the peak knee medial force (pKMF) for SW, ST, and CT (p < 0.001), while the peak knee flexion moment (pKFM) was only a significant predictor of the pKMF for SW (p = 0.034). The statistical analysis showed that the pKMF increased, while the pKFM and the peak knee adduction angle (pKAA) decreased significantly during CT compared to those of SW and ST (p < 0.001). The correlation analysis indicated that the knee parameters during SW and ST were quite similar. This study investigated the relationship between knee medial force and some surrogate parameters during walking and turning. KAM was still the best surrogate parameter for SW, ST, and CT. It is necessary to consider the type of movement when comparing the surrogate predictors of knee medial force, as the prediction equations differ significantly among movement types.

Backstroke-to-Breaststroke Turns Muscular Activity. A Study Conducted in Age Group Swimmers.

The aims of this study were to compare surface electromyographic (EMG) activity and kinematic variables among open, somersault, bucket and crossover backstroke-to-breaststroke turning techniques, and identify relationships between the integrated electromyography (iEMG) and kinematics profile focusing on the rotation and push-off efficacy. Following a four-week of systematically increasing contextual interference intervention program, eight 12.38 ± 0.55 years old male swimmers randomly performed twelve repetitions (three in each technique) turns in and out of the wall at maximum speed until the 7.5 m reference mark. Surface EMG values of the right vastus lateralis, biceps femoris, tibialis anterior, gastrocnemius medialis, rectus abdominis, external oblique, erector spinae and latissimus dorsi were recorded and processed using the integrated electromyography (iEMG) and the total integrated electromyography (TiEMG) that was expressed as a percentage of iEMGmax to normalize per unit of time for each rotation and push-off phase. Complementarily, 2D sagittal views from an underwater video camera were digitized to determine rotation and push-off efficacy. The crossover turn presented the highest rotation and push-off iEMG values. Erector spinae and gastrocnemius medialis had the highest activity in the rotation and push-off phases (89 ± 10 and 98 ± 69%, respectively). TiEMG depicted a very high activity of lower limb muscles during push-off activity (222 ± 17 to 247 ± 16%). However, there were no relation between TiEMG and rotation and push-off time, tuck index and final push-off velocity during the rotation and the push-off phases across all the studied turning techniques. The rotation efficacy in age-group swimmers were dependent on rotation time (p = 0.04). The different turning techniques were not distinguishable regarding iEMG activity as a possible determinant of rotation and push-off efficacy. Our study has direct implications for selecting appropriate exercises and designing training programs for optimizing the rotation and push-off phases of backstroke-to-breaststroke turning at young ages.

Biomechanical Features of Backstroke to Breaststroke Transition Techniques in Age-Group Swimmers.

This study aimed to identify the biomechanical features of backstroke to breaststroke transition techniques (open, somersault, bucket, and crossover) in age-group swimmers. Eighteen preadolescent swimmers (12.2 ± 0.4 years old and 3–4 Tanner stages) underwent 4 weeks of systematic contextual interference training, comprising 16 sessions (40 min·session−1). Soon after, experimental testing was conducted where swimmers randomly performed 12 × 15 m maximal turns (composed of 7.5 m turn-in and 7.5 m turn-out of the wall segments), three in each transition technique. Kinematical, kinetic, and hydrodynamic variables were assessed with a dual-media motion capture system (12 land and 11 underwater cameras), triaxial underwater force plates, and inverse dynamics. Variables were grouped in turn-in (approach and rotation) and turn-out (wall contact, gliding, and pull-out) phases, with factor analysis used to select the variables entering on multiple regressions. For the turn-in phase, 86, 77, 89, and 87% of the variance for open, somersault, bucket, and crossover turning techniques, respectively, was accounted by the 7.5 and 2.5 m times, mean stroke length, and rotation time. For the turn-out phase, first gliding distance and time, second gliding depth, turn-out time, and dominating peak_Z push-off force accounted for 93% in open turn, while wall contact time, first gliding distance, breakout distance and time, turn-out time, dominating peak_Y push-off force, and second gliding drag coefficient accounted for 92% in a somersault turn. The foot plant index, push-off velocity, second gliding distance, and turn-out time accounted for 92% in bucket turn while breakout and turn-out time, non-dominating peak_Y and peak_Z push-off force, first and second gliding drag force and second gliding drag coefficient accounted for 90% in crossover turn, respectively. The findings in this study were novel and provided relevant biomechanical contribution, focusing on the key kinematic–temporal determinant during turn-in, rotation, and push-off efficacy, and the kinetic and hydrodynamic during turn-out, which would lead to improved backstroke to breaststroke transition techniques in 11–13 years-old age-group swimmers.

Modeling and predicting the backstroke to breaststroke turns performance in age-group swimmers

ABSTRACT The purpose of the present study was to identify the performance determinant factors predicting 15-m backstroke-to-breaststroke turning performance using and comparing linear and tree-based machine-learning models. The temporal, kinematic, kinetic and hydrodynamic variables were collected from 18 age-group swimmers (12.08 ± 0.17 yrs) using 23 Qualisys cameras, two tri-axial underwater force plates and inverse dynamics approach. The best models were obtained: (i) with Lasso linear model of the leave-one-out cross-validation in open turn (MSE = 0.011; R2 = 0.825) and in the somersault turn (MSE = 0.016; R2 = 0.734); (ii) the Ridge of the leave-one-out cross-validation (MSE = 0.016; R2 = 0.763) for the bucket turn; and (iii) the AdaBoost tree-based model of the leave-one-out cross-validation for the crossover turn (MSE = 0.016; R2 = 0.644). Model’s selected features revealed that optimum turning performance was very similarly determined for the different techniques, with balanced contributions between turn-in and turn-out variables. As a result, the relevant feature’s contribution of each backstroke-to-breaststroke turning technique are specific; developing approaching speed in conjunction with proper gliding posture and pull-out strategy will result in improved turning performance, and may influence differently the development of specific training intervention programmes.

Increasing the height of the anterior lip on a tibial insert in a posterior stabilized knee prosthesis has little effect on the wear rate

A high anterior lip on a total knee prosthesis is an effective way of reducing anterior translation, but the effect on joint wear is unclear. Using finite element analysis (FEA), this study quantitatively compared wear rates and anterior contact stresses in three posterior stabilized knee prostheses with different heights for the anterior lip during six daily activities (walking, stair ascent, stair descent, sit-to-stand, pivot turn and crossover turn). The wear rate and location of maximum wear depth were similar for the three lip heights tested, but the knee with the highest anterior lip also showed slight anterior wear scaring due to articular contact stress during swing phase, which was highly dependent on the shape of the contact interface. This study illustrates that tibial inserts with a high anterior lip maintain a wear rate similar to moderate and low lip posterior stabilized designs.

Backstroke to Breaststroke Turning Performance in Age-Group Swimmers: Hydrodynamic Characteristics and Pull-Out Strategy.

We compared the hydrodynamic characteristics and pull-out strategies of four backstroke-to-breaststroke turning techniques in young swimmers. Eighteen 11 and 12-year-old swimmers participated in a 4 week intervention program including 16 contextual interference sessions. The hydrodynamic variables were assessed through inverse dynamics, and the pull-out strategy kinematics were assessed with tracking markers followed by 12 land cameras and 11 underwater cameras. Swimmers randomly completed sixteen 30 m maximal backstroke-to breaststroke-open, somersault, bucket and crossover turns (four in each technique) with a 3 min rest. The data showed higher drag force, cross-sectional area and drag coefficient values for the first (compared with the second) gliding position. The crossover turn revealed the highest push-off velocity (2.17 ± 0.05 m·s−1), and the somersault turn demonstrated the lowest foot plant index (0.68 ± 0.03; 68%), which could have affected the first gliding, transition and second gliding depths (0.73 ± 0.13, 0.86 ± 0.17 and 0.76 ± 0.17 m). The data revealed the consistency of the time spent (4.86 ± 0.98 s) and breakout distance (6.04 ± 0.94 m) among the four turning techniques, and no differences were observed between them regarding time and average velocity up to 7.5 m. The hydrodynamic characteristics and pull-out strategy of the backstroke-to-breaststroke turns performed by the age group swimmers were independent of the selected technique.

Effect of Crossover Turns in Double-Pancake Winding on Magnetic Field Homogeneity of HTS NMR Magnet

Field homogeneity of a superconducting magnet is a critical factor for nuclear magnetic resonance (NMR) spectrometers. For REBCO high-temperature superconducting (HTS) coil fabrication, layer-wound is considered a better option than double-pancake (DP) winding, in terms of field homogeneity. Nonetheless, DP winding is preferred to layer-wound owing to the ease of manufacturing and the difficulty in making long REBCO tapes. However, DP winding has an inevitable crossover turn between the top and bottom layers. For magnets with an HTS insert used in NMR spectrometers, the crossover turn could be critical for the field homogeneity. In this paper, the magnetic field generated by the crossover turn is derived based on the Biot-Savart law, and the effect of crossover turns in stacked DPs on the field homogeneity of an NMR-class HTS magnet is analyzed.

Motion type and knee articular conformity influenced mid-flexion stability of a single radius knee prosthesis.

Single radius knee implants were introduced to reduce the level of paradoxical anterior femoral translation (AFT) during mid-flexion after total knee arthroplasty. Findings from clinical and experiment studies are inconsistent, which may be due to the different loading conditions and articular conformities of the knee implants studied. The aim of this study is to analyze how variations in these two factors affect the mid-flexion stability of a single radius knee prosthesis. Six daily activities (walking, stair ascent, stair descent, sit-to-stand, pivot turn and crossover turn), and three articular conformity ratios (low, moderate and high) were considered. The resulting AFTs from the 18 finite element models were analyzed. For low conformity knees, the worst case activity (the greatest AFT) was sit-to-stand with an AFT of 6.2mm, while for the moderate conformity the worst case was crossover turn and pivot turn. For high conformity, all activities produced a relatively small AFT ranging from 0mm to 1.8mm, which more closely resembles natural knee motion. In addition, no AFT was recorded during stair ascent for all three conformities (low, moderate, high). This study demonstrated that the amount of AFT is highly dependent on the activity being undertaken and the articular conformity of the knee prosthesis, and the worst case activity depends on the knee conformity. The clinical relevance of this study is that it offers valuable information towards the design of improved knee prostheses and selection of knee implants for clinical use. II.

Assessment of Physiological Load Testing of Total Knee Implants

Abstract As the demands for total knee arthroplasty continue to rise, the methodologies for testing current and future devices may require refinement. Current standards have not been shown to simulate wear rates and patterns seen in explanation studies. The purpose of this study was to assess a combination of potentially more physiological testing protocols. Four identical TKAs were implanted into four fresh cadaver knees and tested in a knee simulator. Each knee was tested using the ISO load control testing standard (ISO 14243-1) and five novel testing protocols representing different activities of daily living. Motions were recorded between the tibia and femur (tibial rotation, anterior–posterior (AP) motion) and between the implant and bone (superior-inferior femoral condylar motion, tibial tray vertical motion). The total tibial AP cadaver motion varied from a total of 6.2 to 7.6 mm for the six loading protocols during a cycle of motion. For the ISO gait profile and the new gait, stair ascent and stair descent profiles, the range of tibial cadaver rotation varied from 9.2° with the ISO gait to 10.2° with the stair ascent. The crossover turn had a range of 16.3° and the pivot turn a range of 18.7°. Larger tibial tray AP motion, relative to the tibia, occurred with the pivot turn and crossover turn motions, compared to the gait motions or stair activities. This study supports the viability of new and alternative loading profiles. We suggest that these novel profiles should be considered by the ASTM or ISO as they seek to supplement or replace the profiles currently in use.

Anterior translation and rotational stability of anterior cruciate ligament-deficient knees during walking: speed and turning direction.

Anterior cruciate ligament (ACL) rupture is one of the most common injuries associated with the knee. After ACL injury, knee joint stability can be altered, resulting in abnormal loading during functional activities. Since ACL-deficient (ACLD) knees are also vulnerable to translational and rotational instability, patients need to be wary of certain motions encountered in daily life. The present study investigated the effect of walking speed and pivoting directional change during gait on knee joint kinematics of ACLD knees. We hypothesized that faster walking and crossover turning would induce severe kinematic changes. Thirty-five patients (22 males and 13 females) having a unilateral isolated subacute ACLD knee (from 1 to 3 months after injury) and contralateral intact (CLI) knee participated in this study. Spatiotemporal parameters, three-dimensional (3D) knee joint angles, and anterior-posterior (AP) translation were obtained by a 3D high-speed motion-capturing system. The CLI knee of each patient served as the control. The calculated AP stability and knee joint angles were used to test the research hypothesis. Mixed two-way repeated measures analysis of variance was performed to clarify the effects of walking speed and pivoting direction with a significance of 0.05. When a significance of mean comparison was detected, a post hoc test was performed. Significant and consistent increased AP translation of the tibia relative to the femur at the whole stance phase of the gait cycle was evident in ACLD knees compared to CLI knees for normal and faster (20 % greater than normal) walking speeds. Faster walking speed did not induce significantly more anterior location of the tibia. In addition, ACLD knees were significantly less extended than CLI knees during a large portion of midstance. Although there was a consistent varus offset between the curves of ACLD and CLI knees, the difference did not reach statistical significance during the stance phase. Also, ACLD knees did not show any significant difference in tibial rotation compared to CLI knees during the entire stance phase of the gait cycle. For pivoting turns, ACLD knees showed significantly less extended and varus offset than CLI knees only during the cutting turn. ACLD knees exhibited less tibial internal rotation during the crossover turn and less tibial external rotation during the cutting turn than CLI knees. In ACLD knees, the tibia tended to shift more anteriorly and changed with less extension at walking. However, faster walking speed did not induce any significant difference compared with normal-speed walking. In addition, ACLD knees displayed kinematic changes during pivoting, but not the crossover turn.

Listenin’ to the Breeze

Listenin’ to the Breeze Jeffrey R. Di Leo (bio) Benson: The Autobiography George Benson With Alan Goldsher Da Capo Press www.dacapopress.com 222 Pages; Print, $25.99 “Listen.” So begins Miles: The Autobiography (1989) withan imperative from the master that no right-minded jazz fan would ignore. Love him or hate him, when Miles Davis spoke to us with his horn, welistened, just as we did when the man behind the horn told his life story back in 1989. “The greatest feeling I ever had in my life—with my clothes on—was when I first hear Diz and Bird together in St. Louis, back in 1944,” he continues. “I was just eighteen years old and had just graduated from Lincoln High School.” Davis’s story, like those of Diz and Bird, is part of the origin story of jazz in America, one that cannot be retold enough by its progenitors. “When I heard Diz and Bird in B’s band, I said, ‘What? What is this!?’ Man, that shit was so terrible it was scary.” It’s a moment of pure jazz injected into the teenage bloodstream of a genius. The rest is music history—and Davis left few stones unturned in the 400-plus pages of densely and richly packed autobiography. The world of jazz is hyper-competitive, particularly onstage where musicians aim to outplay and out-style one another. It is also a world where the footsteps and shadows of the greats like Bird and Miles are often respected almost to a fault. This respect is part of the jazz code, a set of unwritten rules. Learning from those who practice them is a revealing glimpse into artistic life. This is the gift of Benson: The Autobiography (2014) by George Benson and Alan Goldsher: engaging stories from a talented guitarist with a mellow voice who seemed always one step behind the giants of jazz. George Benson recounts his interactions with and feelings about many musicians from his long and remarkable life in music. In one of the book’s more memorable passages, Benson recalls getting a call from Miles asking him to join a recording session. “After I hung up, I stared at the wall for a good long while,” says Benson, “the same question blowing through my head over and over again: What am I going to play on a Miles Davis record?” Turns out Benson was right: his role in the session ended up little more than a vamp reinforcement. “And to tell the truth,” confesses Benson, “most of what happened that afternoon and evening was well out of my comfort zone.” But Benson made his mark, laying down the guitar track for “Paraphernalia,” a cut from Davis’s 1968 classic album, Miles in the Sky—a track that opened a new chapter in Davis’s musical journey. Later, Benson recounts getting paired with guitarist John McLaughlin for a gig at Lincoln Center. “I’m sure he [the promoter] was hoping for a guitar gunfight at the O.K. Corral,” says Benson, but both guitarists decided to take it back a notch. Afterwards, Benson wondered about the strange, sitar-sounding effects used by McLaughlin, who replied, “I don’t want people comparing us, so I did something completely different.” Benson is dismissed by some jazz enthusiasts because of his crossover turn towards popular and mainstream music. If anything, Benson’s original sin as a jazz musician is becoming a household name. He seems to be aware of this as he tells his story in this wonderfully concise and fast-moving autobiography. Benson rose in popularity in the mid-1970s with the release of his album Breezin’. “After twelve months,” writes Benson, “the album sold over four million copies and was nominated for five Grammy Awards.” “After that, things started changing. Drastically.” But surprisingly, these tales of drastic changes amount to little more than the final thirty-five pages of the book. The fact that Benson devotes only one fifth of the book to the last half of his career, notably the period after he became a household name, is telling. The tension between artistic and commercial success tempers the entirety of his autobiography...

Analysis of a rotary task following total knee arthroplasty: Stair descent with a cross-over turn

Leg loading and knee angle differences have been reported in total knee replacement individuals during straight gait; however, little is known about the impact on the knee during turning. Rotary motions may be difficult following total knee replacement surgery; therefore, some individuals may develop strategies or utilize pre-surgical strategies in order to maintain function. The primary aim of this study was to identify differences in individuals with a total knee replacement as compared to their healthy counterparts during stair descent followed by a cross-over turn. Ground reaction force, knee angle and moments were recorded on 10 total knee replacement and 12 healthy individuals during stair descent followed by a turn and compared to walking straight. Variables were analyzed for the affected, unaffected and healthy knees during the gait cycle. On initial contact, the total knee replacement group had less ground reaction force on the affected leg compared to the unaffected leg (p = 0.021) and had delayed contact (p = 0.044) and a slower loading rate (p = 0.020) compared to healthy group. During mid-stance, the affected leg had less ground reaction force compared to the healthy leg (p = 0.049). The affected stance leg had less knee flexion during mid-stance in both the straight trial (p = 0.002) and turn (p = 0.010). Moment differed between straight and turn trials but not between groups. Stair descent with or without a turn was approached in a precautionary manner by individuals with a total knee replacement. Slow approach, reduced impact and weight-bearing with a more extended knee on the affected leg may suggest a protective strategy to avoid risk of fall.

Compensatory turning strategies while walking in patients with hip osteoarthritis

The ability to change directions while walking is an integral component of adaptive locomotor behavior. Patients with hip osteoarthritis (OA) experience prolonged hip dysfunction. Gait compensation adopted by the patients with hip OA may become more pronounced while they turn. The purposes of this study were to identify the turning strategy while walking in patients with hip OA, and to examine the relationship between the turning strategy and the patient’s functional level. Fourteen patients with hip OA and 13 age-matched healthy controls were recruited. The hip, knee, and ankle joint angles and moments, and the foot progression angle were measured under three walking conditions (straight walking, 45° step turn, and 45° crossover turn), and the gait variables for each walking condition were compared between the 2 groups. The relationship between the increasing rate of knee and ankle joint moments in the turning to the straight walking and the functional point in the Harris hip score (HHS) was examined. The OA group showed decreased hip flexion, extension, and abduction angles, and hip flexion moment during the step turn, and decreased hip flexion, extension, and adduction angles, and hip abduction moment during the crossover turn. Furthermore, the ankle plantarflexion moment and the change in the foot angle during the stance phase were significantly increased during the crossover turn in the OA group. The increasing rate of the ankle plantarflexion moment correlated significantly with the functional point in the HHS. Patients with hip OA rely primarily on the ankle plantarflexors to compensate for the hip dysfunction while changing the walking direction.

Long-axis rotation: a missing degree of freedom in avian bipedal locomotion.

Ground-dwelling birds are typically characterized as erect bipeds having hind limbs that operate parasagittally. Consequently, most previous research has emphasized flexion/extension angles and moments as calculated from a lateral perspective. Three-dimensional (3D) motion analyses have documented non-planar limb movements, but the skeletal kinematics underlying changes in foot orientation and transverse position remain unclear. In particular, long-axis rotation of the proximal limb segments is extremely difficult to measure with topical markers. Here, we present six degree of freedom skeletal kinematic data from maneuvering guineafowl acquired by marker-based XROMM (X-ray Reconstruction of Moving Morphology). Translations and rotations of the hips, knees, ankles and pelvis were derived from animated bone models using explicit joint coordinate systems. We distinguished sidesteps, sidestep yaws, crossover yaws, sidestep turns and crossover turns, but birds often performed a sequence of blended partial maneuvers. Long-axis rotation of the femur (up to 38 deg) modulated the foot's transverse position. Long-axis rotation of the tibiotarsus (up to 65 deg) also affected medio-lateral positioning, but primarily served to either re-orient a swing phase foot or yaw the body about a stance phase foot. Tarsometatarsal long-axis rotation was minimal, as was hip, knee and ankle abduction/adduction. Despite having superficially hinge-like joints, birds coordinate substantial long-axis rotations of the hips and knees to execute complex 3D maneuvers while striking a diversity of non-planar poses.

Three-Dimensional Knee Kinematics by Conventional Gait Analysis for Eleven Motor Tasks of Daily Living: Typical Patterns and Repeatability

The availability of detailed knee kinematic data during various activities can facilitate clinical studies of this joint. To describe in detail normal knee joint rotations in all three anatomical planes, 25 healthy subjects (aged 22-49 years) performed eleven motor tasks, including walking, step ascent and descent, each with and without sidestep or crossover turns, chair rise, mild and deep squats, and forward lunge. Kinematic data were obtained with a conventional lower-body gait analysis protocol over three trials per task. To assess the repeatability with standard indices, a representative subset of 10 subjects underwent three repetitions of the entire motion capture session. Extracted parameters with good repeatability included maximum and minimum axial rotation during turning, local extremes of the flexion curves during gait tasks, and stride times. These specific repeatable parameters can be used for task selection or power analysis when planning future clinical studies.

Relationship of Off-Ice and On-Ice Performance Measures in High School Male Hockey Players

The purpose of this study was to examine the relationship of off-ice performance measures with on-ice turning, crossover, and forward skating performance in high school male hockey players. Thirty-eight players aged 15-18 (mean age ± SD: 16.4 ± 1.1 years; height: 177.9 ± 6.8 cm; weight: 72.5 ± 8.9 kg) participated in this study. On-ice tests included a forward sprint, short radius turns, and crossover turns. Off-ice tests included a 40-yd sprint, vertical jumps, horizontal jumps, and a dynamic balance test using a Y balance testing device. Five off-ice variables correlated with all on-ice performance measures. These variables included the 40-yd sprint, lateral bound right to left limb, double limb horizontal hop, balance on right in posterolateral direction, and composite balance performance on the right. Hierachical regression demonstrated that off-ice sprint time was most predictive of on-ice skating performance, accounting for 65.4% of the variability in forward skate time, 45.0% of the variability in left short radius time, 21.8% of the variance in right short radius time, 36.2% of the variance in left crossover time, and 30.8% of the variability in right crossover time. When using off-ice tests to evaluate hockey players, the 40-yd sprint is the best predictor of skating performance. Based on our regression equation, for every 1-second difference in the 40-yd sprint time, there will be approximately a 0.6-second difference in the 34.5-m on-ice sprint. The 40-yd sprint predicts forward skating performance and to a lesser degree; it also predicts crossover and tuning performance.

Range of motion and repeatability of knee kinematics for 11 clinically relevant motor tasks

Standard gait analysis reports knee joint rotations in the three anatomical planes without addressing their different levels of reliability. Most clinical studies also restrict analysis to knee flexion–extension, because knee abduction–adduction and axial rotation are small with respect to the corresponding amount of measurement artefact. This study analyses a set of 11 motor tasks, in order to identify those that are adequately repeatable and that can induce greater motion at the knee than walking. Ten volunteers (mean ± SD age: 29 ± 9 years) each underwent three motion analysis sessions on different days with a standard gait analysis system and protocol. In each session they performed normal walking, walking with sidestep and crossover turns, ascent onto and descent off a step, descent with sidestep and crossover turns, chair rise, mild and deep squats, and lunge. Range and repeatability of motions in the three anatomical planes were compared by ANOVA. The sidestep turns showed a range of axial rotation significantly larger than that in walking (about 8°), while maintaining similar levels of repeatability. Ascent, chair rise, squat, and lunge showed greater flexion ranges than walking; among these, ascent was the most repeatable. The results show that turning increases knee axial rotation in young subjects significantly. Further, squats and lunges, currently of large interest in orthopaedics and sports research, have smaller repeatability, likely accounted for to the smaller constraints than in the traditional motor tasks.

Knee rotation during a weightbearing activity: Influence of turning

Kinematic studies, in which mobile- and fixed-bearing total knee arthroplasty (TKA) were compared, showed controversial results with respect to axial femorotibial rotation. However, all studies focused only on straight ahead tasks, which may underestimate possible differences in freedom of rotation. The purpose of this study was to investigate the influence of turning on normal axial knee rotation. If large differences across tasks were to be found, this would support the use of this task in the evaluation of in-vivo TKA kinematics. In 15 healthy persons, crossover and sidestep turns were added to a standardized chair rise. Three-dimensional knee angles were recorded using an optoelectronic motion analysis system, and a noninvasive epicondylar frame was developed to track the femur. Compared to knee rotation during the straight ahead task, average peak tibial internal rotation increased during a crossover turn ( p < 0.001), as did peak external tibia rotation during a sidestep turn ( p < 0.001). The combined range of axial rotation for both turning tasks together was 20.9°, versus 13.5° for the straight ahead task ( p < 0.001). The turning maneuvers in this study induced a large range of axial knee rotation, so they could be important in studies comparing freedom of rotation in mobile- and fixed-bearing TKA.

Kinematic modifications after surgical correction of equinovarus foot deformity in chronic hemiplegic adults

nertia during the pivot phase. The actual pivot phase required hree specific power phases in the transverse plane (A2T, 2T, H2T), which provided rotational power to displace the oG toward the new direction. The rotational power at the nkle appears to have been a result of a counter movement uring the deceleration phase, which resulted in an absorption 1T phase prior to the generation A2T phase. The timings of he transverse power peaks suggest that rotation was coming own the kinetic chain initiated from the hip. However, it is robable that the upper body segments lead the pivot [1]. The ipsilateral crossover turn did not require increased uscular demand during the turn phase, as there was no pivot hase suggesting the turn was a result of a fall rather than by ny active means. Because there was no pivot and the foot as rooted to the ground, to complete the crossover, an H3T eneration phase externally rotated the hip/pelvis toward the ew direction.

Performance skating characteristics of professional ice hockey forwards

The performance skating characteristics of the typical National Hockey League forward have not been investigated to the best of the authors' knowledge. The purpose of this study was: (1) to establish an observational protocol and perform motion analysis to identify the individual performance skating characteristics of the high and low, point scoring, National Hockey League forward (n= 12), (2) determine the percentage of execution time spent in each skating characteristic measured by time and the percentage of occurrence of each skating characteristic counted and (3) identify each variable that differentiates a high from a low point scorer. A two‐tiered slow‐motion observational protocol was used to analyze each skating characteristic adopted during a game. Fifteen timed, and 12 frequency, performance skating characteristics were identified and analyzed. The highest mean percentages of time spent by a player in a game were on a two foot glide (39.0%), a cruise stride (16.2%), medium intensity skating (10.0%), a struggle for puck or position (9.8%), and low intensity skating (7.8%). The highest percentage of total occurrences were a left crossover turn (20.2%), a gliding left turn (17.8%), a right crossover turn (17.7%) and a gliding right turn (16.4%). The primary difference between a high and a low point scorer was that a high point scorer spent more time on the ice, and had a higher mean percentage of time spent in a two foot glide with and without a puck. A low point scorer had a higher mean percentage of occurrence in transition from forward to backward skating, and a higher mean percentage of occurrence in a gliding right turn and a left cross over turn while stickhandling the puck.