Knee Angular Velocity Research Articles

Are isokinetic leg torques and kick velocity reliable predictors of competitive level in taekwondo athletes?

The aim of this study is to analyze how isokinetic knee and hip peak torques and roundhouse kick velocities are related to expertise level (elite vs. sub-elite) in taekwondo athletes. Seven elite and seven sub-elite athletes were tested for kick-specific variables (KSV, composed of kinematic variables and power of impact) and for concentric isokinetic peak torque (PT) at 60°/s and 240°/s. First, KSVs and PTs were compared between groups, then PTs were correlated with KSVs. Parametric variables with larger effect sizes (Cohen’s d) were entered in a stepwise linear discriminant analysis (LDA), generating an equation to estimate competitive level. Between-group differences were found in hip flexors (p = 0.04, d = 0.92) and extensors (p = 0.04, d = 0.96) with PT at 240°/s. Hip flexion PT at 60°/s and 240°/s correlated negatively with kick time (R = –0.46, p = 0.0499 and R = –0.62, p = 0.01 respectively). Hip flexion torque at 60°/s correlated positively (R = 0.52, p = 0.03) with peak linear velocity of the foot (LVF) and power of impact (R = 0.51, p = 0.03). Peak torque of hip extension at 60°/s and hip abduction at 240°/s also correlated with LVF (R = 0.56, p = 0.02 and R = 0.46, p = 0.0499). Hip extension at 60°/s correlated positively with peak linear velocity of the knee (R = 0.48, p = 0.04). The LDA showed an accuracy of 85.7% (p = 0.003) in predicting expertise level based on hip flexion and extension torques at 240°/s and on knee extension velocity during the kick. The study demonstrates that hip muscle strength is probably the dominant muscular factor for determining kick performance. Knee angular velocity combined with hip torques is the best discriminator for competitive level in taekwondo athletes.

Effect of Footwear on the Biomechanics of Loaded Back Squats to Volitional Exhaustion in Skilled Lifters.

Brice, SM, Doma, K, and Spratford, W. Effect of footwear on the biomechanics of loaded back squats to volitional exhaustion in skilled lifters. J Strength Cond Res 36(10): 2676-2684, 2022-This study examined whether footwear influences the movement dynamics of barbell back squats to volitional exhaustion in experienced lifters. Eleven men (1 repetition maximum [1RM] = 138 ± 19 kg; 1RM % body mass = 168 ± 18%) performed 3 sets (5-12 ± 4 repetitions per set) of loaded barbell back squats to volitional exhaustion using raised-heel and flat-heel footwear. Barbell motion as well as moments, angles, angular velocity, and power in the sagittal plane at the ankle, knee, hip, and lumbopelvis were examined during the second repetition of the first set (T second ) and the final repetition of the third set (T final ). There were significant reductions ( p < 0.05) in lower-limb concentric angular velocity and power output for both footwear conditions. For the raised-heel condition at T final , hip and knee concentric angular velocities were significantly slower ( p < 0.05), and knee concentric power output was significantly less ( p < 0.05) compared with the flat-heel condition. A reduction in barbell velocity was not observed for the raised-heel condition despite there being reduction in hip and knee angular velocities. Furthermore, no differences were identified in lower-limb joint moments or any of the biomechanical characteristics of the lumbopelvis between the footwear conditions. The findings of this study suggest that neither type of footwear reduced joint loading or improved joint range-of-motion.

Toward Remote Assessment of Physical Frailty Using Sensor-based Sit-to-stand Test

BackgroundTraditional physical frailty (PF) screening tools are resource intensive and unsuitable for remote assessment. In this study, we used five times sit-to-stand test (5×STS) with wearable sensors to determine PF and three key frailty phenotypes (slowness, weakness, and exhaustion) objectively. Materials and methodsOlder adults (n = 102, age: 76.54 ± 7.72 y, 72% women) performed 5×STS while wearing sensors attached to the trunk and bilateral thigh and shank. Duration of 5×STS was recorded using a stopwatch. Seventeen sensor-derived variables were analyzed to determine the ability of 5×STS to distinguish PF, slowness, weakness, and exhaustion. Binary logistic regression was used, and its area under curve was calculated. ResultsA strong correlation was observed between sensor-based and manually-recorded 5xSTS durations (r = 0.93, P < 0.0001). Sensor-derived variables indicators of slowness (5×STS duration, hip angular velocity range, and knee angular velocity range), weakness (hip power range and knee power range), and exhaustion (coefficient of variation (CV) of hip angular velocity range, CV of vertical velocity range, and CV of vertical power range) were different between the robust group and prefrail/frail group (P < 0.05) with medium to large effect sizes (Cohen's d = 0.50-1.09). The results suggested that sensor-derived variables enable identifying PF, slowness, weakness, and exhaustion with an area under curve of 0.861, 0.865, 0.720, and 0.723, respectively. ConclusionsOur study suggests that sensor-based 5×STS can provide digital biomarkers of PF, slowness, weakness, and exhaustion. The simplicity, ease of administration in front of a camera, and safety of 5xSTS may facilitate a remote assessment of PF, slowness, weakness, and exhaustion via telemedicine.

Biomechanical Analysis of the Tuck Jump Assessment.

Nascimento, N, Sideris, V, and Read, PJ. Biomechanical analysis of the tuck jump assessment. J Strength Cond Res 36(10): 2946-2949, 2022-The tuck jump assessment (TJA) examines plyometric technique flaws associated with the increased risk of anterior cruciate ligament injury. Biomechanical data to investigate the mechanics used during the TJA are limited and assessing each jump individually across the entire test period is time inefficient. This study examined performance characteristics and movement mechanics in 16 professional soccer players during a standardized TJA protocol (10 jumps) to determine if sensitive periods exist within the test period (first 5 vs. last 5). Jump height, average power (PW) reactive strength index (RSI), frontal plane projection angle (FPPA), knee angular velocity (AV), and peak knee flexion angle (PKA) were analyzed using an optoelectrical and inertial measurement unit device. Jump height and PW increased in the past 5 jumps displaying a medium effect size (d = > 0.5). A trend was observed of increased AV, FPPA, and PKA during the past 5 jumps; however, no meaningful differences were observed between respective jump phases, and effect sizes were small (d ≤ 0.2). This study indicates that performance metrics increase during the past 5 jumps of a standardized TJA 10-jump protocol; thus, analyzing the entire test period may not be required, providing a time-efficient approach. Caution should be applied if using this protocol as an injury risk screening tool or to identify fatigue related alterations in male professional soccer players as no obvious movement abnormalities were apparent and minimal differences were present between jump phases in a range of kinematic variables across the recorded test duration.

Women with patellofemoral pain and knee crepitus have reduced knee flexion angle during stair ascent

ObjectivesTo compare trunk and knee biomechanics of women with and without patellofemoral pain (PFP) and knee crepitus during stair ascent. DesignCross-sectional. SettingLaboratory-based study. Participants29 women with PFP and knee crepitus (PFPCrepitus); 28 women with PFP and no knee crepitus (PFPNOCrepitus); 17 pain-free women with knee crepitus (Pain-freeCrepitus); and 29 pain-free women without knee crepitus (Pain-freeNOCrepitus). Main outcome measuresPeak trunk flexion, peak knee flexion, mean knee angular velocity, knee extensor moment at peak knee flexion, peak and impulse of the knee extensor moment. ResultsPFPCrepitus group performed the stair ascent task with reduced peak knee flexion compared to Pain-freeCrepitus (p = 0.04; Effect size = −0.85) and Pain-freeNOCrepitus (p = 0.03; Effect size = −0.75). No significant differences among groups were found for peak trunk flexion (p = 0.979), knee angular velocity (p = 0.420), knee extensor moment at peak knee flexion (p = 0.933), peak (p = 0.290) and impulse (p = 0.122) of the knee extensor moment. ConclusionWomen with concomitant PFP and knee crepitus demonstrated reduced knee flexion during stair ascent, but no significant differences for trunk flexion and knee extensor moment variables were found.

Choice of low-pass filter influences practical interpretation of ball kicking motions: the effect of a time-frequency filter method

ABSTRACT When studying ball kicking, conventional low-pass filters may distort kick leg kinematics near the time of foot-to-ball contact, leading to flawed practical interpretation of the skill. Time-frequency filters are a viable alternative but are not widely used. This study compared a fractional Fourier filter (FrFF) with conventional filters (CF) methods for estimating common parameters used to define kicking performance. Instep kicks from 23 experienced soccer players were captured by 3D motion analysis (1000 Hz), and kick leg foot velocities, knee angular velocities and ankle dorsi-plantarflexion angles compared between the FrFF and variations of a Butterworth CF. The FrFF and CFs using a higher cut-off frequency (>70 Hz) successfully detected lower leg motion prior to, during and following impact, whereas CFs with low cut-off frequencies (<20 Hz) attenuated motion near impact. Truncating data at impact provided valid pre-impact kinematics, but ignored information thereafter. Rather than decelerating the lower leg to conserve accuracy, ‘kicking through the ball’ should be considered a valid coaching cue. Further, controlling ankle plantar flexion to ensure efficient impact mechanics may be important for skilled kicking. Practitioners should consider how choice of filter will affect their data, and use of time-frequency methods can help inform empirically grounded coaching practices.

Modulation of physiological cross-sectional area and fascicle length of vastus lateralis muscle in response to eccentric exercise

In the current study, we investigated the effect of lengthening velocity during eccentric exercise on the modulation of the physiological cross-sectional area (PCSA) and fascicle length of the vastus lateralis (VL) muscle. We hypothesized a greater increase in muscle PCSA after training with lower lengthening velocities and a greater increase in fascicle length after higher lengthening velocities. Forty-seven young men were randomly assigned to either a control (n = 14) or an intervention group (n = 33). The participants of the intervention group were randomly allocated to one of four isokinetic eccentric training protocols of the knee extensors, with four different knee angular velocities (45°/s, 120°/s, 210°/s and 300°/s), yet similar range of motion (25–100° knee joint angle), load magnitude (100% of isometric maximum) and load volume (i.e. similar time under tension for one training set). Before and after an 11-week training period with 3 times per week exercise, muscle volume, pennation angle, fascicle length and PCSA of the VL muscle were measured using magnetic resonance imaging and ultrasonography. After the training, the VL muscle volume and fascicle length increased similarly and approximately 5% in all investigated protocols. The PCSA and pennation angles of the VL did not change after any exercise protocol, indicating negligible radial muscle adaptation after the training. The reason for the found hypertrophy of VL muscle after eccentric training in a wide range of lengthening velocities was mainly a longitudinal muscle growth. Further, the longitudinal muscle growth was independent of the lengthening velocity.

Validity of and recommendations for knee joint acoustic assessments during different movement conditions

Knee joint sounds contain information on joint health, morphology and loading. These acoustic signals may be elicited by further, as yet unknown factors. By assessing potential elicitors and their relative contributions to the acoustic signal, we investigated the validity of vibroarthrographic assessments during different movement conditions with the aim to derive recommendations for their practical usage. Cross-sectional study. Nineteen healthy participants (24.7 ± 2.8 yrs, 7 females) performed five movements: level walking, descending stairs, standing up, sitting down, and forward lunge. Knee joint sounds were recorded by two microphones (medial tibial plateau, patella). Knee joint kinematics and ground reaction forces were recorded synchronously to calculate knee joint moments (Nm/Kg). The mean amplitude (dB) and the median power frequency (Hz) were determined. A repeated measures mixed model investigated the impact of potential predictors (sagittal, frontal, transverse plane and total knee joint moments, knee angular velocity, age, sex, body mass index (BMI) and Tegner Activity Score (TAS)). Most of the amplitudes variance is explained by between-subject differences (tibia: 66.6%; patella: 75.8%), and of the median power frequencies variance by the movement condition (tibia: 97.6%; patella: 98.9%). The final model revealed several predictor variables for both sensors (tibia: sagittal plane, frontal plane, and total knee joint moments, age, and TAS; patella: sagittal plane knee moments, knee angular velocity, TAS). The standardization of the execution of the activities, a between-group matching of variables and the inclusion of co-variates are recommended to increase the validity of vibroarthrographic measurements during different movement conditions of the knee joint.

Age-related differences in vastus lateralis fascicle behavior during fast accelerative leg-extension movements.

Leg-extensor rate of power development (RPD) decreases during aging. This study aimed to identify the underlying mechanism of the age-related decline in RPD during a fast acceleration in terms of in vivo vastus lateralis (VL) fascicle shortening behavior. Thirty-nine men aged between 25 and 69years performed three maximal isokinetic leg-extensor tests with a fixed initial acceleration of 45° knee extension in 150ms until 340°/s knee angular velocity. RPD, VL activity, and ultrasound images were recorded to assess (relative) fascicle shortening and mean shortening velocity for the phases of electromechanical delay, pretension, and acceleration. Our findings show that fascicle shortening and mean shortening velocity during a fast action increase with aging (0.002 per year, P=.035 and 0.005s-1 per year, P=.097, respectively), mainly due to a higher amount of shortening in the phase of electromechanical delay. The ratio of VL fascicle length over upper leg length at rest showed a negative correlation (r=-.46, P=.004) with RPD/body mass, while pennation angle at rest showed a trend toward a positive correlation (r=.28, P=.089). To conclude, our findings indicate that the ability to reach high VL fascicle shortening velocities in vivo is not reduced in older men while performing preprogrammed fast accelerations. The greater amount of fascicle shortening in old age is probably the result of age-related differences in the tendinous properties of the muscle-tendon complex, forcing the fascicles to shorten more in order to transmit the muscle force to the segment.

Use of Sonomyographic Sensing to Estimate Knee Angular Velocity During Varying Modes of Ambulation.

Ultrasound (US) imaging of muscle has been introduced as a promising sensing modality for assistive device control. Ten able-bodied subjects completed level, incline and decline walking on a treadmill in a motion capture laboratory while wearing reflective markers on upper- and lower-body. A wearable US transducer was affixed to subjects' anterior thigh, and time-intensity features were extracted from transverse US images of the knee extensor muscles. These features were used to train and test Gaussian process regression models for continuous estimation of knee flexion/extension angular velocity. Four regression models were evaluated: (1) subject-dependent/task-specific, (2) subject-dependent/pooled-tasks, (3) subject-independent/task-specific, and (4) subject-independent/pooled-tasks. Subject-independent models were "tuned" with up to six strides of the test subject's data to boost performance. A two-factor analysis of variance test was used to assess the effect of each approach on root mean square error (RMSE) of estimated knee angular velocity (α=0.05). Statistical parametric mapping (SPM) was completed to compare actual vs. estimated knee angular velocity as a function of the gait cycle (α=0.05). For incline and level walking, the subject-dependent/pooled-tasks model resulted in the lowest error while the subject-dependent/task-specific model resulted in the lowest error for decline walk. Impressively, the two-factor test revealed no difference between task-specific and pooled-task models. Furthermore, despite capturing many important features of knee velocity across individuals there were, as expected, significant differences between subject-dependent and subject-independent models. Collectively, these results are promising for potential assistive device control with error rates <10% for all regression models that were tested.Clinical Relevance-This work is the first study to demonstrate the feasibility of using ultrasound-based sensing for estimation of knee angular velocity during multiple modes of ambulation.

The kick motion analysis of adolescent male soccer players with Osgood-Schlatter disease

Objectives:Osgood-Schlatter disease (OSD) is an injury during adolescence, in which inflammation occurs in the epiphyseal cartilage of the tibial tubercle by repeated traction of patellar tendon. OSD is associated with more in sports that involve jumping, kicking, and running, such as soccer. However, whether the kick motion of adolescent soccer players is related to onset of OSD remains unclear. The purpose of this study was to clarify the characteristics of kick motion in adolescent soccer players who developed OSD prospectively, using three-dimensional motion analysis system.Methods:A total of 29 Japanese adolescent male soccer players who were 12 years old (Hight 153.1 ± 6.9cm, Bodyweight 42.8 ± 7.0kg) joining the same soccer team were followed over a half year period. The team is a town recreation league team. At the baseline, all players went through the medical examination, ultrasonography of tibial tubercle and measurement of real-time kick motion using a three-dimensional motion analysis system (Qualisys track manager, Qualisys AB., Sweden). The three-dimensional angle of the lumbar spine, pelvis, hips, knees, ankles of both legs, the position of supporting leg and center of mass (COM) were calculated by 65 spherical markers on each anatomical landmark. COM was adjusted dividing by height. The ball speed, kicking time, angular velocity and angular acceleration were also calculated. The data of each phase was collected for the following eight events: foot contact, toe off, maximum hip extension, maximum knee flexion, ball impact, maximum hip flexion of kicking leg, and foot contact, maximum knee flexion of supporting leg. Phase duration was calculated as a percentage of the kick motion. The muscle tightness test of bilateral lower limbs (Iliopsoas, Hamstrings, Quadriceps, Gastrocnemius, Soleus muscle) were measured at the baseline and the follow-up. The participants were followed six months later, and OSD was diagnosed by tenderness and ultrasonography findings of the tibial tubercle and were divided into two groups: presence of OSD on supporting leg; OSD and absence of OSD; CON. All the factors calculated by the kick motion analysis at the baseline and the development of muscle tightness of bilateral lower limbs between OSD and CON were compared by using the unpaired t-test. Players who were diagnosed as OSD at the baseline (n=6) were excluded from the analysis.Results:There were 10 players of OSD and 13 players of CON. The growth of height, muscle tightness, ball speed, kicking time, phase duration in OSD were not different from CON. The sagittal translation of COM in OSD was significantly smaller than CON(p<0.05) before the ball impact phase. The knee angular acceleration of supporting leg was significantly larger in OSD(p<0.05) between the phase supporting leg lands and the flexion angle of its knee reaches the peak before the ball impact. The lateral bending angle of the pelvis toward the supporting leg in OSD was significantly smaller(p<0.05), and the maximum hip extension angle of kicking leg, lumbar rotation angle, kicking leg’s knee angular velocity and acceleration at the ball impact were smaller in OSD(p<0.1).Conclusion:The kick motion with small translation of COM before ball impact was associated to onset of OSD. OSD also showed smaller range of motion in proximal joints to the knees compared with CON. The large knee angular acceleration of supporting leg towards maximum knee flexion was found in OSD, which may increase the traction of quadriceps muscle to the tibial tubercle.Figure 1.

Kinematic differences between successful and faulty spikes in young volleyball players

ABSTRACT This study was designated to investigate the kinematical differences between successful and faulty spikes, in order to identify the best strategies leading to better spike performance. Simulating a real-game condition, 13 elite youth attackers performed 6 spikes in the presence of 2 blocks. The kinematic variables of the spike performances were recorded using 6 optoelectronic cameras (Vicon Motion systems, Oxford, UK). The paired sample t-test was used to compare the kinematic variables recorded during the delivery of successful and faulty spikes. Among the successful trials, both the angular velocities of the knees (≈12.4%) and hips (≈13.3%), and the vertical velocity of the centre of mass at take-off (≈6.5%) and arm swing (≈8.2%) were considerably higher during the plant phase. Consequently, the jump (≈4.3%) and spike (≈1.5%) heights, as well as the wrist velocity (≈5.5%), were significantly higher during the jump phase of successful spikes. In successful spike performances, the attackers adopted higher hip and knee angular velocities, combined with efficient arm swings, to produce higher take-off velocities and reach higher jump heights. This approach provides them with the better position regarding the ball and the blockers to find the best path and hit the ball with higher arm velocities.

An Inertial Measurement Unit Based Method to Estimate Hip and Knee Joint Kinematics in Team Sport Athletes on the Field.

Current athlete monitoring practice in team sports is mainly based on positional data measured by global positioning or local positioning systems. The disadvantage of these measurement systems is that they do not register lower extremity kinematics, which could be a useful measure for identifying injury-risk factors. Rapid development in sensor technology may overcome the limitations of the current measurement systems. With inertial measurement units (IMUs) securely fixed to body segments, sensor fusion algorithms and a biomechanical model, joint kinematics could be estimated. The main purpose of this article is to demonstrate a sensor setup for estimating hip and knee joint kinematics of team sport athletes in the field. Five male subjects (age 22.5 ± 2.1 years; body mass 77.0 ± 3.8 kg; height 184.3 ± 5.2 cm; training experience 15.3 ± 4.8 years) performed a maximal 30-meter linear sprint. Hip and knee joint angles and angular velocities were obtained by five IMUs placed on the pelvis, both thighs and both shanks. Hip angles ranged from 195° (± 8°) extension to 100.5° (± 8°) flexion and knee angles ranged from 168.6° (± 12°) minimal flexion and 62.8° (± 12°) maximal flexion. Furthermore, hip angular velocity ranged between 802.6 °·s-1 (± 192 °·s-1) and -674.9 °·s-1 (± 130 °·s-1). Knee angular velocity ranged between 1155.9 °·s-1 (± 200 °·s-1) and -1208.2 °·s-1 (± 264 °·s-1). The sensor setup has been validated and could provide additional information with regard to athlete monitoring in the field.This may help professionals in a daily sports setting to evaluate their training programs, aiming to reduce injury and optimize performance.

Kinetic and Kinematic Changes in Vertical Jump in Prepubescent Girls After 10 Weeks of Plyometric Training.

To examine the effect of a 10-week plyometric training (PT) on the kinematic and kinetic properties of prepubescent girls during squat jump, countermovement jump, and drop jumps. Twenty-four untrained girls (aged 9-11y) were assigned to a training group (TG) and a control group. The TG followed twice a week PT for 10 weeks. Squat jump, countermovement jump, and drop jumps performed from heights of 20, 35, and 50cm were tested before and after PT. Jump height, kinematic, and kinetic parameters were evaluated using a motion analysis system and a force plate. Jumping height in all jump types increased significantly after PT for the TG (P < .001). After training, the TG presented increased power (P < .001) and knee angular velocity (P < .001), higher knee flexion at the deepest point during the braking phase (P < .001), longer contact time (P < .001), and unchanged stiffness and reaction strength index (P > .05). No differences were observed in the control group (P > .05). These findings indicate that a 10-week PT positively affected jumping performance in prepubescent girls who improved their drop jump performance after training not by adopting a stiff/bouncing jumping style of short contact time and increased stiffness, but a compliant/absorbing style of prolonged contact time.

Biomechanical correlates for recovering walking speed following a stroke. The potential of tibia to vertical angle as a therapy target

BackgroundRecovering independent walking is a priority for stroke survivors. Community walking requires speeds exceeding the average values typically achieved at discharge (0.7 m/s). To improve outcomes there is a need to clarify the factors associated with recovery of functional walking speeds. Research questionWhich biomechanical variables correlate significantly with improved walking speed following rehabilitation in acute stroke patients. MethodsThe study was embedded in a larger clinical trial testing efficacy of a gait training splint. Participants, within 6 weeks of their stroke and exhibiting abnormal gait, were recruited. Using a valid and reliable video-based system, specific kinematic measures were recorded before randomisation (baseline), after a 6-week rehabilitation phase (outcome) and six months after stroke (follow-up). Measures of temporospatial symmetry, knee angular velocity and tibia to vertical angle were added to clinical measures and correlated with change in speed. Results23 participants were recruited, (mean age 67.7 ± 16.7 years, 19.2 ± 9.0 days after stroke and 73.9% male), with 20/23 assessed at outcome and 17/23 at follow-up. Drop out was due to withdrawal (3) and technical failure (3). Walking speed increased by 0.15 ± 0.21 m/s (outcome), and 0.21 ± 0.14 m/s (follow-up) from baseline (0.50 ± 0.20 m/s). This increase correlated with an increase in step length (r=0.88) and change in angle of tibia at initial contact (r=-0.59), foot flat (r=-0.61) and terminal contact (r=0.54). SignificanceThis study of gait recovery among acute stroke patients demonstrated modest improvements in walking speed. Walking speed by follow-up (0.71 m/s) classified the group as community walkers (>0.66 m/s) but still too slow to safely use a pedestrian road crossing. Change in step length and tibia to vertical angle significantly correlated with increased walking speed. This finding provides distinctive targets for therapy aimed at improving community walking among stroke survivors. This hypothesis should be tested prospectively in future studies.

On the use of segmental tracking methods with skin clusters

Recovering independent walking is a priority for stroke survivors. Community walking requires speeds exceeding the average values typically achieved at discharge (0.7 m/s). To improve outcomes there is a need to clarify the factors associated with recovery of functional walking speeds.Which biomechanical variables correlate significantly with improved walking speed following rehabilitation in acute stroke patients.The study was embedded in a larger clinical trial testing efficacy of a gait training splint. Participants, within 6 weeks of their stroke and exhibiting abnormal gait, were recruited. Using a valid and reliable video-based system, specific kinematic measures were recorded before randomisation (baseline), after a 6-week rehabilitation phase (outcome) and six months after stroke (follow-up). Measures of temporospatial symmetry, knee angular velocity and tibia to vertical angle were added to clinical measures and correlated with change in speed.23 participants were recruited, (mean age 67.7 ± 16.7 years, 19.2 ± 9.0 days after stroke and 73.9% male), with 20/23 assessed at outcome and 17/23 at follow-up. Drop out was due to withdrawal (3) and technical failure (3). Walking speed increased by 0.15 ± 0.21 m/s (outcome), and 0.21 ± 0.14 m/s (follow-up) from baseline (0.50 ± 0.20 m/s). This increase correlated with an increase in step length (r=0.88) and change in angle of tibia at initial contact (r=-0.59), foot flat (r=-0.61) and terminal contact (r=0.54).This study of gait recovery among acute stroke patients demonstrated modest improvements in walking speed. Walking speed by follow-up (0.71 m/s) classified the group as community walkers (>0.66 m/s) but still too slow to safely use a pedestrian road crossing. Change in step length and tibia to vertical angle significantly correlated with increased walking speed. This finding provides distinctive targets for therapy aimed at improving community walking among stroke survivors. This hypothesis should be tested prospectively in future studies.

One-DOF Wire-Driven Robot Assisting Both Hip and Knee Flexion Motion

Gait assistance robots are used to improve gait performance ability or perform gait motion with an assistance for several articular motions. The sparing use of a gait assistance robot to decrease the duration of the robot’s assistance is important for keeping the ability to perform a movement when the robot assists walking. In previous research, methods of ensuring a compliance mechanism and control method have been studied, and assistance for articular motions has been conducted independently using actuators corresponding to each articular motion. In this paper, we propose a wire-driven gait assistance robot to aid both hip and knee articular flexion motions by applying just one force to assist motion in the swing phase. We focused on a force that assists hip and knee flexion motion, and designed a robot with a compensation mechanism for the wire length. We used an assistance timing detection method for the robot, conducting tensile force control based on information from the hip, knee, and ankle angles. We carried out an experiment to investigate the controlled performance of the proposed robot and the effect on hip and knee angular velocity. We confirmed that the proposed robotic system can aid both hip and knee articular motion with just one force application.

Concurrent changes in eccentric hamstring strength and knee joint kinematics induced by soccer-specific fatigue

ObjectivesTo investigate the influence of soccer-specific fatigue on concurrent changes in knee joint kinematics and hamstring strength, given the increased risk of injury during the latter stages of match-play and the prevalence of knee joint and hamstring muscular injury. DesignRepeated measures, randomized order trials. SettingLaboratory. ParticipantsTen male professional soccer players. Main outcome measuresReactive inversion, eversion and neutral hop tasks were completed at 15 min intervals during a soccer-specific protocol, with touchdown knee joint kinematics in the frontal and sagittal planes calculated at 200 Hz. In a separate trial, players completed maximal eccentric knee flexions at 160°·s−1 (reflecting average knee angular velocity in the functional task) at 15 min intervals, quantifying peak torque. ResultsAll trials were characterized by knee varus at touchdown, with ∼4° greater mal-alignment elicited over the final 15 min of the protocol (P ≤ 0.05). Peak eccentric hamstring strength was significantly (P = 0.045) reduced throughout the 2nd half. ConclusionsThe coincident impairment of eccentric hamstring strength and increased knee varus at touchdown predisposes the player to injury, supporting epidemiological observations. Knee varus in these elite male players is in marked contrast to the valgus associated with ACL injury risk in female players.

Sex-related differences in joint-angle-specific hamstring-to-quadriceps function following fatigue

The purpose of this study was to examine the effect of fatiguing exercise on sex-related differences in the function of hamstring and quadriceps muscles at several angular velocities and joint angles. Physically active participants (50 male: 28.7 ± 4.5y, 1.82 ± 0.07 m, 82.3 ± 6.87 kg; 50 female: 27.0 ± 5.8y, 1.61 ± 0.08 m, 68.75 ± 9.24 kg) carried out an isokinetic assessment to determine concentric and eccentric torques during knee extension and flexion actions at three different angular velocities (60/180/300°/s). The H/QFUNCT was calculated using peak torque (PT) values at 3 different joint-angle-specific (15°, 30° and 45° of knee flexion). A repeated measures analysis of variance (ANOVA) was used to compare within group results. Between group comparisons of sex-related differences were assessed by independent T-tests. Fatiguing exercise in males resulted in a decrease in H/QFUNCT ratios for each angle of knee flexion at both 60°/s and 300°/s angular velocities (p < 0.05). In females, significant decreases in H/QFUNCT ratios were observed following fatiguing exercise for each angle of knee flexion and angular velocity (p < 0.01). Significant differences in H/QFUNCT ratios following fatiguing exercise were evident between males and females at each joint angle and angular velocity (p < 0.01). These findings indicate sex related differences in H/QFUNCT ratios following fatiguing exercise. Females have greater reductions in torque and H/QFUNCT ratios following fatigue than their male counterparts. This potentially exposes females to higher risks of injury, particularly when fatigued. Practitioners should attend to the imbalance in fatigue resistance of hamstring and quadriceps function, particularly in female athletes.

An exploration of the effect of proprioceptive knee bracing on biomechanics during a badminton lunge to the net, and the implications to injury mechanisms.

The aim of this study was to determine changes in knee biomechanics during badminton lunges due to fatigue, lunge strategy and knee bracing. Kinetic and kinematic data were collected from 16 experienced right-handed badminton players. Three factor repeated measures ANOVAs (lunge direction—fatigue—brace) were performed with Least Significant Difference pairwise comparisons. In addition, clinical assessments including; Y-balance test, one leg hop distance and ankle dorsiflexion range of motion were performed pre- and postfatigue. The knee showed significantly greater flexion during the forehand lunge compared to backhand. In contrast, the internal rotation velocity and the knee extension moment were greater during backhand. Knee angular velocity in the sagittal plane, peak knee moment and range of moment in the coronal plane and stance time showed significantly lower values postfatigue. In addition, the peak knee adduction moment showed significantly lower values in the braced condition in both the fatigued and nonfatigues states, and no significant differences were seen for peak vertical force, loading rate, approach velocity, or in any of the clinical assessment scores. There appears to be greater risk factors when performing a backhand lunge to the net compared to a forehand lunge, and proprioceptive bracing appears to reduce the loading at the knee.