Hip and knee kinematics, center of pressure position, and ground reaction force are associated with Achilles tendon force during jump landing.

PURPOSE: Jump-landing exercises are often performed during the rehabilitation of Achilles tendon (AT) injuries. However, the factors that affect the AT force (ATF) during landing are unclear. This study aimed to determine the kinematics and ground reaction force (GRF) variables associated with the peak ATF during a drop vertical jump (DVJ). METHODS: The landing phase of DVJ was evaluated in 101 healthy participants (46 males, age: 21.2 ± 1.4 years old) using a three-dimensional motion analysis system with two force plates. ATF was estimated from the ankle flexion angle and moment. Univariate and multivariate regression analyses were performed with the peak ATF as the dependent variable. The vertical GRF (VGRF), center of pressure (COP), forward trunk leaning, hip/knee/ankle joint angles at peak ATF, and sex were used as independent variables. RESULTS: In the univariate regression analysis, larger VGRF (ß = 0.813), more anterior COP position (ß = 0.214), smaller knee flexion (ß = -0.251) and adduction (ß = -0.252), smaller hip flexion (ß = -0.407), smaller forward trunk lean (ß = -0.492), and male sex (ß = -0.282) were significantly associated with a larger peak ATF. Multivariate analysis revealed that larger VGRF (ß = 1.018), more anterior COP position (ß = 0.320), a larger knee (ß = 0.442), and smaller hip flexion (ß = -0.205) were associated with the larger peak ATF. CONCLUSIONS: The VGRF, COP position, and knee and hip flexion were independently associated with ATF. Modifying these factors may be useful in managing tendon loading during jump-landing exercises.

Transcranial direct current stimulation to the left dorsolateral prefrontal cortex enhances early dexterity skills with the left non-dominant hand: a randomized controlled trial.

BACKGROUND: The left dorsolateral prefrontal cortex (DLPFC) is involved in early-phase manual dexterity skill acquisition when cognitive control processes, such as integration and complexity demands, are required. However, the effectiveness of left DLPFC transcranial direct current stimulation (tDCS) on early-phase motor learning and whether its effectiveness depends on the cognitive demand of the target task are unclear. This study aimed to investigate whether tDCS over the left DLPFC improves non-dominant hand dexterity performance and determine if its efficacy depends on the cognitive demand of the target task. METHODS: In this randomized, double-blind, sham-controlled trial, 70 healthy, right-handed, young adult participants were recruited. They were randomly allocated to the active tDCS (2 mA for 20 min) or sham groups and repeatedly performed the Purdue Pegboard Test (PPT) left-handed peg task and left-handed assembly task three times: pre-tDCS, during tDCS, and post tDCS. RESULTS: The final sample comprised 66 healthy young adults (mean age, 22.73 ± 1.57 years). There were significant interactions between group and time in both PPT tasks, indicating significantly higher performance of those in the active tDCS group than those in the sham group post tDCS (p < 0.001). Moreover, a greater benefit was observed in the left-handed assembly task performance than in the peg task performance (p < 0.001). No significant correlation between baseline performance and benefits from tDCS was observed in either task. CONCLUSIONS: These results demonstrated that prefrontal tDCS significantly improved early-phase manual dexterity skill acquisition, and its benefits were greater for the task with high cognitive demands. These findings contribute to a deeper understanding of the underlying neurophysiological mechanisms of the left DLPFC in the modulation of early-phase dexterity skill acquisition. TRIAL REGISTRATION: This study was registered in the University Hospital Medical Information Network Clinical Trial Registry in Japan (UMIN000046868), Registered February 8, 2022 https://center6.umin.ac.jp/cgi-open-bin/ctr_e/ctr_view.cgi?recptno=R000053467.

Repetitive pitching decreases the elbow valgus stability provided by the flexor-pronator mass: the effects of repetitive pitching on elbow valgus stability.

BACKGROUND: Baseball pitching induces a large elbow valgus load, stressing the ulnar collateral ligament (UCL). Flexor-pronator mass (FPM) contraction contributes to valgus stability; however, repetitive baseball pitching may weaken the FPM contractile function. The present study investigated the effects of repetitive baseball pitching on the medial valgus stability measured using ultrasonography. We hypothesized that repetitive pitching would decrease elbow valgus stability. METHODS: This was a controlled laboratory study. Fifteen young male baseball players at the collegiate level (age: 23.0 ± 1.4 years) were enrolled. The medial elbow joint space was measured using ultrasonography (B-mode, 12-MHz linear array transducer) in the following three conditions: at rest (unloaded), under 3 kg valgus load (loaded), and under valgus load with maximal grip contraction to activate FPM (loaded-contracted). All measurements were performed before and after the pitching tasks, which comprised five sets of 20 pitches. Two-way repeated-measures analysis of variance was applied to determine changes in the medial elbow joint space. The post hoc test with Bonferroni adjustment was applied to assess the changes within the time and condition. RESULTS: The medial elbow joint space was significantly greater under the loaded than the unloaded and loaded-contracted conditions both before and after pitching (P < .001). In the loaded-contracted condition, the medial elbow joint space significantly increased after repetitive baseball pitching (P < .001). CONCLUSIONS: The results of the present study indicated that repetitive baseball pitching reduced the elbow valgus stability. This reduction could be attributed to the decreased FPM contractile function. Insufficient contraction may increase the tensile load on the UCL with pitching. FPM contraction plays a role in narrowing the medial elbow joint space; however, repetitive baseball pitching reduced the elbow valgus stability. It has been suggested that sufficient rest and recovery of the FPM function are required to reduce the UCL injury risk.

Validity of AI-Based Gait Analysis for Simultaneous Measurement of Bilateral Lower Limb Kinematics Using a Single Video Camera.

Accuracy validation of gait analysis using pose estimation with artificial intelligence (AI) remains inadequate, particularly in objective assessments of absolute error and similarity of waveform patterns. This study aimed to clarify objective measures for absolute error and waveform pattern similarity in gait analysis using pose estimation AI (OpenPose). Additionally, we investigated the feasibility of simultaneous measuring both lower limbs using a single camera from one side. We compared motion analysis data from pose estimation AI using video footage that was synchronized with a three-dimensional motion analysis device. The comparisons involved mean absolute error (MAE) and the coefficient of multiple correlation (CMC) to compare the waveform pattern similarity. The MAE ranged from 2.3 to 3.1° on the camera side and from 3.1 to 4.1° on the opposite side, with slightly higher accuracy on the camera side. Moreover, the CMC ranged from 0.936 to 0.994 on the camera side and from 0.890 to 0.988 on the opposite side, indicating a "very good to excellent" waveform similarity. Gait analysis using a single camera revealed that the precision on both sides was sufficiently robust for clinical evaluation, while measurement accuracy was slightly superior on the camera side.

Evaluation of Lower-Limb Kinematics during Timed Up and Go (TUG) Test in Subjects with Locomotive Syndrome (LS) Using Wearable Gait Sensors (H-Gait System).

Few studies have dealt with lower-limb kinematics during the timed up and go (TUG) test in subjects with locomotive syndrome (LS). This study aimed to evaluate the characteristics of lower-limb kinematics during the TUG test in subjects with LS using the wearable sensor-based H-Gait system. A total of 140 participants were divided into the non-LS (n = 28), the LS-stage 1 (n = 78), and LS-stage 2 (n = 34) groups based on the LS risk test. Compared with the non-LS group, the LS-stage 1 and LS-stage 2 groups showed significantly smaller angular velocity of hip and knee extension during the sit-to-stand phase. The LS-stage 2 group showed significantly smaller peak angles of hip extension and flexion during the walking-out phase compared to the non-LS group. These findings indicate that the evaluation of the lower-limb kinematics during the TUG test using the H-Gait system is highly sensitive to detect LS, compared with the evaluation of the lower-limb kinematics when simply walking.

Improved responsiveness for JKOOS+ compared to KOOS in Japanese patients undergoing total knee arthroplasty.

BACKGROUND: Existing knee related patient reported outcome measurements (PROMs) have overwhelmingly been developed and validated in western chair-based societies, suggesting a potential for a western bias in PROMs evaluation of patients with knee conditions. We, therefore, endeavor to evaluate the responsiveness of the previously developed culturally relevant Japanese version of the knee injury and osteoarthritis outcome score (JKOOS+). METHODS: We enrolled 114 patients scheduled for total knee arthroplasty (TKA) across 8 knee clinics in Japan. Patients completed the Oxford Knee Score (OKS) and JKOOS + both at the time of enrollment and again 1-year post-TKA. Responsiveness was evaluated using effect size and standardized response mean (SRM). An effect size or SRM >0.8 is considered adequately responsive. We further tested the difference in responsiveness between the original Japanese language KOOS activities of daily living (ADL) domain and the novel Japanese ADL (JADL) domain using the modified Jacknife test. RESULTS: All domains were adequately responsive with the exception of the KOOS sports and recreation domain, which has previously been ignored by TKA researchers due to its lack of applicability to elderly patients undergoing TKA. The JADL domain outperformed the ADL domain in both effect size (1.51 v. 1.45) and SRM (1.67 v. 1.57) (p < 0.001). The novel Knee Flexion (KF) domain was adequately responsive, though less responsive than other domains except sports and recreation (p < 0.01 v. all other PROMs domains). CONCLUSIONS: The JKOOS+ JADL domain is significantly more responsive than the Europe-developed ADL domain to TKA in Japanese knee patients suffering from knee osteoarthritis (OA). The KF domain, unique to the JKOOS+ and intended to assess difficulty with knee flexion, is adequately responsive to TKA in Japanese patients suffering from OA.

Pelvic Rotation Is Associated With Asymmetry in the Knee Extensor Moment During Double-Leg Squatting After Anterior Cruciate Ligament Reconstruction.

Asymmetry in knee extensor moment during double-leg squatting was observed after anterior cruciate ligament reconstruction, even after the completion of the rehabilitation program for return to sports. The purpose of this study was to clarify the association between asymmetry in the knee extensor moment and pelvic rotation angle during double-leg squatting after anterior cruciate ligament reconstruction. Twenty-four participants performed double-leg squatting. Kinetics and kinematics during squatting were analyzed using a 3-dimensional motion analysis system with 2 force plates. The limb symmetry index of knee extensor moment was predicted by the pelvic rotation angle (R2 = .376, P = .001). In addition, the pelvic rotation and the limb symmetry index of the vertical ground reaction force independently explained the limb symmetry index of the knee extensor moment (R2 = .635, P < .001, ß of pelvic rotation = -0.489, ß of vertical ground reaction force = 0.524). Pelvic rotation toward the involved limb was associated with a smaller knee extensor moment in the involved limb than in the uninvolved limb. The assessment of pelvic rotation would be useful for partially predicting asymmetry in the knee extensor moment during double-leg squatting. Minimizing pelvic rotation may improve the asymmetry in the knee extensor moment during double-leg squatting after anterior cruciate ligament reconstruction.

Early Changes in Postural Balance Following Inverted V-Shaped High Tibial Osteotomy in Patients With Knee Osteoarthritis.

Patients with knee osteoarthritis and varus knee deformity have impaired postural balance, resulting in decreased walking performance and an increased risk of falls. This study aimed to investigate the early changes in the postural balance following inverted V-shaped high tibial osteotomy (HTO). Fifteen patients with medial knee osteoarthritis were recruited. Postural balance was assessed using the center-of-pressure (COP) data during single-leg standing before and 6 weeks after inverted V-shaped HTO. The maximum range, mean velocity, and area of COP movements in the anteroposterior and mediolateral directions were analyzed. Preoperative and postoperative visual analog scale for knee pain was assessed. The maximum range of COP in the mediolateral direction decreased (P = .017), whereas the mean velocity of COP in the anteroposterior direction increased 6 weeks postoperatively (P = .011). The visual analog scale score for knee pain significantly improved at 6 weeks postoperatively (P = .006). Valgus correction with inverted V-shaped HTO resulted in improved postural balance in the mediolateral direction and good short-term clinical outcomes early following surgery. Early rehabilitation after inverted V-shaped HTO should focus on postural balance in the anteroposterior direction.

Subsequent Jumping Increases the Knee and Hip Abduction Moment, Trunk Lateral Tilt, and Trunk Rotation Motion During Single-Leg Landing in Female Individuals.

Single-leg landings with or without subsequent jumping are frequently used to evaluate landing biomechanics. The purpose of this study was to investigate the effects of subsequent jumping on the external knee abduction moment and trunk and hip biomechanics during single-leg landing. Thirty young adult female participants performed a single-leg drop vertical jumping (SDVJ; landing with subsequent jumping) and single-leg drop landing (SDL; landing without subsequent jumping). Trunk, hip, and knee biomechanics were evaluated using a 3-dimensional motion analysis system. The peak knee abduction moment was significantly larger during SDVJ than during SDL (SDVJ 0.08 [0.10] N·m·kg-1·m-1, SDL 0.05 [0.10] N·m·kg-1·m-1, P = .002). The trunk lateral tilt and rotation angles toward the support-leg side and external hip abduction moment were significantly larger during SDVJ than during SDL (P < .05). The difference in the peak hip abduction moment between SDVJ and SDL predicted the difference in the peak knee abduction moment (P = .003, R2 = .252). Landing tasks with subsequent jumping would have advantages for evaluating trunk and hip control as well as knee abduction moment. In particular, evaluating hip abduction moment may be important because of its association with the knee abduction moment.

Improvements in asymmetry in knee flexion motion during landing are associated with the postoperative period and quadriceps strength after anterior cruciate ligament reconstruction.

This study investigated the relationship between quadriceps strength and knee kinematics during a drop vertical jump (DVJ) at 6, 9 and 12 months after anterior cruciate ligament reconstruction (ACLR) in 9 male and 22 female athletes (16.6 ± 2.1 years old). Isokinetic quadriceps strength was measured by a dynamometer (Biodex System 3). Knee flexion excursion was assessed using two-dimensional analysis. Knee flexion excursion at 6 months was significantly smaller in the involved limb than in the uninvolved limb independent of quadriceps strength (56.7° ± 9.3°, 63.4° ± 11.4°, P < 0.001). At 9 months, only the low quadriceps strength group demonstrated a similar interlimb difference (57.2°± 12.3°, 63.3° ± 10.5°, P < 0.001). At 12 months, there was no significant interlimb difference in knee flexion excursion regardless of quadriceps strength. These findings indicate that restoration in symmetrical knee flexion excursion during a DVJ requires rehabilitation as well as quadriceps strength.

Inertial Sensor-Based Assessment of Static Balance in Athletes with Chronic Ankle Instability.

The Balance Error Scoring System (BESS), a subjective examiner-based assessment, is often employed to assess postural balance in individuals with chronic ankle instability (CAI); however, inertial sensors may enhance the detection of balance deficits. This study aimed to compare the BESS results between the CAI and healthy groups using conventional BESS scores and inertial sensor data. The BESS test (six conditions: double-leg, single-leg, and tandem stances on firm and foam surfaces, respectively) was performed for the CAI (n = 16) and healthy control (n = 16) groups with inertial sensors mounted on the sacrum and anterior shank. The BESS score was calculated visually by the examiner by counting postural sway as an error based on the recorded video. The root mean square for resultant acceleration (RMSacc) in the anteroposterior, mediolateral, and vertical directions was calculated from each inertial sensor affixed to the sacral and shank surfaces during the BESS test. The mixed-effects analysis of variance and unpaired t-test were used to assess the effects of group and condition on the BESS scores and RMSacc. No significant between-group differences were found in the RMSacc of the sacral and shank surfaces, and the BESS scores (P > 0.05), except for the total BESS score in the foam condition (CAI: 14.4 ± 3.7, control: 11.7 ± 3.4; P = 0.039). Significant main effects of the conditions were found with respect to the BESS scores and RMSacc for the sacral and anterior shank (P < 0.05). The BESS test with inertial sensors can detect differences in the BESS conditions for athletes with CAI. However, our method could not detect any differences between the CAI and healthy groups.

Trunk Muscle Activities during Ergometer Rowing in Rowers with and without Low Back Pain.

This study aimed to determine the differences in trunk muscle activity during rowing at maximal effort between rowers with and without low back pain (LBP). Ten rowers with LBP and 12 rowers without LBP were enrolled in this study. All rowers performed a 500-m trial using a rowing ergometer at maximal effort. The amplitudes of the activities of the thoracic erector spinae (TES), lumbar erector spinae (LES), latissimus dorsi (LD), rectus abdominis (RA), and external oblique (EO) muscles were analyzed using a wireless surface electromyography (EMG) system. EMG data at each stroke were converted into 10-time series data by recording averages at every 10% in the 100% stroke cycle and normalized by maximum voluntary isometric contraction in each muscle. Two-way repeated measures analysis of variance was performed. Significant interactions were found in the activities of the TES and LES (P < 0.001 and P = 0.047, respectively). In the post hoc test, the TES activity in the LBP group was significantly higher than that in the control group at the 10% to 20% and 20% to 30% stroke cycles (P = 0.013 and P = 0.007, respectively). The LES activity in the LBP group was significantly higher than that in the control group at the 0% to 10% stroke cycle (P < 0.001). There was a main group effect on the LD activity, with significantly higher activity in the LBP group than in the control group (P = 0.023). There were no significant interactions or main effects in the EO and RA activities between the groups. The present study showed that rowers with LBP compared with those without LBP exhibited significantly higher TES, LES, and LD muscle activities. This indicates that rowers with LBP exhibit excessive back muscle activity during rowing under maximal effort.

Evaluation of gait characteristics in subjects with locomotive syndrome using wearable gait sensors.

BACKGROUND: Individuals with locomotive syndrome (LS) require nursing care services owing to problems with locomotion and the musculoskeletal system. Individuals with LS generally have a reduced walking speed compared with those without LS. However, differences in lower-limb kinematics and gait between individuals with and without LS are not fully understood. This study aimed to clarify the characteristics of the gait kinematics of individuals with LS using wearable sensors. METHODS: We assessed 125 participants (mean age 73.0 ± 6.7 years) who used a public health promotion facility. Based on the 25-question Geriatric Locomotive Function Scale (GLFS-25), these participants were grouped into the non-LS (GLFS-25 < 7), LS-stage 1 (GLFS-25 7-16), and LS-stage 2 (GLFS-25 ≥ 16) groups (larger GLFS-25 scores indicate worse locomotive ability). Spatiotemporal parameters and lower-limb kinematics during the 10-m walk test were analyzed by the "H-Gait system", which is a motion analysis system that was developed by the authors and is based on seven inertial sensors. The peak joint angles during the stance and swing phases, as well as the gait speed, cadence, and step length were compared among all groups. RESULTS: There were 69 participants in the non-LS group, 33 in the LS-stage 1 group, and 23 in the LS-stage 2 group. Compared with the non-LS group, the LS-stage 2 group showed significantly smaller peak angles of hip extension (9.5 ± 5.3° vs 4.2 ± 8.2°, P = 0.002), hip flexion (34.2 ± 8.8° vs 28.5 ± 9.5°, P = 0.026), and knee flexion (65.2 ± 18.7° vs 50.6 ± 18.5°, P = 0.005). The LS-stage 1 and LS-stage 2 groups had a significantly slower mean gait speed than the non-LS group (non-LS: 1.3 ± 0.2 m/s, LS-stage 1: 1.2 ± 0.2 m/s, LS-stage 2: 1.1 ± 0.2 m/s, P < 0.001). CONCLUSIONS: The LS-stage 2 group showed significantly different lower-limb kinematics compared with the non-LS group, including smaller peak angles of hip extension, hip flexion, and knee flexion. It would be useful to assess and improve these small peak joint angles during gait for individuals classified as LS-stage 2.

Effects of Changing Center of Pressure Position on Knee and Ankle Extensor Moments During Double-Leg Squatting.

The effects of changes in the anterior-posterior center of pressure (AP-COP) position on the lower limb joint moments during double-leg squatting remain unclear. The purpose of this study was to determine the effects of AP-COP positional changes on the hip, knee, and ankle extensor moments during double-leg squatting. Sixteen male participants (22.1 ± 1.5 years) performed double-leg squatting under two conditions (anterior and posterior COP conditions) with visual feedback on their COP positions. Kinematics and kinetics were analyzed using a three-dimensional motion analysis system and force plates. The hip, knee and ankle flexion angles and extensor moments at peak vertical ground reaction force were compared between the two conditions using paired t tests. The COP position was 53.5 ± 2.4% of the foot length, starting from the heel, under the anterior condition and 44.4 ± 2.1% under the posterior condition (P < 0.001). The knee extensor moment was significantly smaller under the anterior than the posterior COP condition (P = 0.003, 95% confidence interval (CI) -0.087 to -0.021 Nm/kg/m), while the ankle extensor moment significantly larger under the anterior COP condition than under the posterior COP condition (P < 0.001, 95% CI 0.113 to 0.147 Nm/kg/m). There was no significant difference in hip extensor moment (P = 0.431). The ankle dorsiflexion angle was significantly larger under the anterior than the posterior COP condition (P = 0.003, 95% CI 0.6 to 2.6°), while there was no difference in trunk, hip, or knee flexion angle. The present results indicate that changes in the AP-COP position mainly affect the ankle and knee extensor moments during double-leg squatting, while the effect on the lower limb joint and trunk flexion angles was limited. Visual feedback on the AP-COP position could be useful for modifying the ankle and knee extensor moments during double-leg squatting.

Dynamic postural control correlates with activities of daily living and quality of life in patients with knee osteoarthritis.

BACKGROUND: Knee osteoarthritis (OA) negatively affects dynamic postural control, which is a basic function that individuals use to perform activities of daily living (ADL). The purpose of this study was to investigate the associations of center of pressure (COP) control during the transition from double-leg to single-leg standing with subjective assessments of ADL and quality of life (QOL) in patients with knee OA. METHODS: Thirty-six patients (29 females) with moderate-to-severe knee OA participated. Dynamic postural control was evaluated during the transition from double-leg to single-leg standing. Each patient stood on a force plate, lifted the less affected limb as fast as possible, and maintained single-leg standing with the more affected limb. The COP movements corresponding to anticipatory postural adjustment (APA) and transitional phases were assessed. The maximum displacement and peak velocity of the COP movements in the medial-lateral direction were calculated. The Knee Injury and Osteoarthritis Outcome Score (KOOS) was used for the subjective assessment of ADL and QOL. Pearson's product correlation analysis was performed to investigate the associations of COP movements in the APA and transitional phases with KOOS-ADL and KOOS-QOL. RESULTS: In the APA phase, the maximum COP displacement was significantly correlated with KOOS-ADL (r = -0.353, P = 0.035) and KOOS-QOL (r = -0.379, P = 0.023). In the transitional phase, the maximum COP displacement and peak COP velocity were significantly correlated with KOOS-ADL (maximum displacement: r = 0.352, P = 0.035; peak velocity: r = 0.438, P = 0.008) and with KOOS-QOL (maximum displacement: r = 0.357, P = 0.032; peak velocity: r = 0.343, P = 0.040). CONCLUSIONS: The present study showed that smaller COP movements in the APA phase and smaller and slower COP movements in the transitional phase correlated with poorer ADL and QOL conditions in patients with knee OA. These findings suggest that poor dynamic postural control is associated with poor ADL and QOL conditions in patients with moderate-to-severe medial knee OA. Conservative treatment for patients with knee OA may need to focus on dynamic postural control during the transition from double-leg to single-leg standing.

Effects of unweighting on gait kinematics during walking on a lower-body positive-pressure treadmill in patients with hip osteoarthritis.

BACKGROUND: Hip osteoarthritis (OA) is a musculoskeletal condition that makes walking difficult due to pain induced by weight-bearing activities. Treadmills that support the body weight (BW) reduce the load on the lower limbs, and those equipped with a lower-body positive-pressure (LBPP) device, developed as a new method for unweighting, significantly reduce pain in patients with knee OA. However, the effects of unweighting on gait kinematics remain unclear in patients with hip OA. Therefore, we investigated the effects of unweighting on kinematics in patients with hip OA during walking on a treadmill equipped with an LBPP device. METHODS: A total of 15 women with hip OA and 15 age-matched female controls wore a three-dimensional (3-D) motion analysis system and walked at a self-selected speed on the LBPP treadmill. Data regarding self-reported hip pain using a numeric rating scale (NRS) in which the scores 0 and 10 represented no pain and the worst pain, respectively, under three different BW conditions (100, 75, and 50%) were collected. Moreover, 3-D peak joint angles during gait under each condition were calculated and compared. RESULTS: In the hip OA group, the NRS pain scores at 50 and 75% BW conditions significantly decreased compared with that at 100% BW condition (50%, P = 0.002; 75%, P = 0.026), and the peak hip extension angle decreased compared with that in the healthy controls (P = 0.044). In both groups, unweighting significantly decreased the peak hip (P < 0.001) and knee (P < 0.001) flexion angles and increased the peak ankle plantar flexion angle (P < 0.001) during walking. CONCLUSIONS: Unweighting by the LBPP treadmill decreased pain in the hip OA group but did not drastically alter the gait kinematics compared with that in the control group. Therefore, regarding the use of the LBPP treadmill for patients with hip OA, clinicians should consider the benefits of pain reduction rather than the kinematic changes.

Analysis of 3-D Kinematics Using H-Gait System during Walking on a Lower Body Positive Pressure Treadmill.

Recently, treadmills equipped with a lower-body positive-pressure (LBPP) device have been developed to provide precise body weight support (BWS) during walking. Since lower limbs are covered in a waist-high chamber of an LBPP treadmill, a conventional motion analysis using an optical method is impossible to evaluate gait kinematics on LBPP. We have developed a wearable-sensor-based three-dimensional motion analysis system, H-Gait. The purpose of the present study was to investigate the effects of BWS by a LBPP treadmill on gait kinematics using an H-Gait system. Twenty-five healthy subjects walked at 2.5 km/h on a LBPP treadmill under the following three conditions: (1) 0%BWS, (2) 25%BWS and (3) 50%BWS conditions. Acceleration and angular velocity from seven wearable sensors were used to analyze lower limb kinematics during walking. BWS significantly decreased peak angles of hip adduction, knee adduction and ankle dorsiflexion. In particular, the peak knee adduction angle at the 50%BWS significantly decreased compared to at the 25%BWS (p = 0.012) or 0%BWS (p < 0.001). The present study showed that H-Gait system can detect the changes in gait kinematics in response to BWS by a LBPP treadmill and provided a useful clinical application of the H-Gait system to walking exercises.

Influence of Constant Torque Stretching at Different Stretching Intensities on Flexibility and Mechanical Properties of Plantar Flexors.

ABSTRACT: Oba, K, Samukawa, M, Nakamura, K, Mikami, K, Suzumori, Y, Ishida, Y, Keeler, N, Saitoh, H, Yamanaka, M, and Tohyama, H. Influence of constant torque stretching at different stretching intensities on flexibility and mechanical properties of plantar flexors. J Strength Cond Res 35(3): 709-714, 2021-The purpose of this study was to examine the effects of constant torque stretching (CTS) at different stretching intensities on the maximal range of motion (ROM) and muscle-tendon unit (MTU) stiffness of plantar flexors. Fourteen healthy men performed 4 trials of differing stretch intensities: no stretching (control), 50, 75, and 100%. Stretch intensity was defined as maximum passive resistive torque predetermined at a familiarization trial. Each stretch trial consisted of 5 sets of 60-second CTS at the designated stretch intensity. Both maximal ROM and passive resistive torque were assessed during passive dorsiflexion, and MTU stiffness was calculated using the torque-angle curves measured before and after CTS. There were no significant differences in maximal ROM or MTU stiffness at the baseline condition. After the intervention, significantly greater maximal ROM and significantly lower MTU stiffness were observed in the 100% CTS condition than the control condition, whereas there were no significant differences between the submaximal intensity condition (i.e., 50 or 75% intensity) and the control condition. Therefore, our findings suggest that maximal intensity stretching is the most effective approach for improving both flexibility and MTU stiffness with CTS.

Abdominal draw-in maneuver changes neuromuscular responses to sudden release from trunk loading in patients with non-specific chronic low back pain.

BACKGROUND: Abdominal draw-in maneuver (ADIM) has been recommended to achieve appropriate trunk muscle response for patients with non-specific chronic low back pain (CLBP). However, it has remained unclear whether the intervention with ADIM could change the trunk muscle response to sudden release from loading, which is considered to contribute mechanical circumstances to low back pain. The purpose of the present study was to investigate the effects of the intervention with ADIM on electromyography (EMG) activities of trunk muscles following sudden release from loading. METHODS: Seventeen subjects with non-specific CLBP participated. Subjects resisted trunk flexion or extension loading in semi-seated position, and then the loading was suddenly released. EMG recordings of 6 trunk muscles were acquired using a wireless surface EMG system. Onset and offset times were calculated from the EMG data. The intervention with ADIM was provided for 4 weeks. The onset and offset times were compared between pre- and post-intervention with ADIM. RESULTS: At the post-intervention, the onset of trunk flexors following release from trunk flexion loading became significantly earlier than pre-intervention (P = 0.028). The offset of flexors following release from trunk extension loading of post-intervention was significantly earlier than that of pre-intervention (P = 0.001). CONCLUSIONS: We showed that the intervention with ADIM changed the EMG activity of trunk flexors in response to sudden release from loading. These results suggest a possibility that ADIM might be effective to improve the neuromuscular control of trunk flexors for the treatment of young patients with non-specific CLBP.

Warm-Up Intensity and Time Course Effects on Jump Performance.

Jump performance is affected by warm-up intensity and body temperature, but the time course effects have not been thoroughly investigated. The purpose of this study was to investigate time course effects on jump performance after warm-up at different intensities. Nine male athletes (age: 20.9 ± 1.0 years; height: 1.75 ± 0.03 m; weight: 66.4 ± 6.3 kg; mean ± SD) volunteered for this study. The participants performed three warm-ups at different intensities: 15 min at 80% VO2 max, 15 min at 60% VO2 max, and no warm-up (control). After each warm-up, counter movement jump (CMJ) height, vastus lateralis temperature, heart rate and subjective fatigue level were measured at three intervals: immediately after warm-up, 10 min after, and 20 min after, respectively. Significant main effects and interactions were found for muscle temperature (intensity: p < 0.01, η2p = 0.909; time: p < 0.01, η2p = 0.898; interaction: p < 0.01, η2p = 0.917). There was a significant increase of muscle temperature from the baseline after warm-up, which lasted for 20 min after warm-up with 80% VO2 max and 60% VO2 max (p < 0.01). Muscle temperature was significantly higher with warm-up at 80% VO2 max than other conditions (P < 0.01). Significant main effects and interactions for CMJ height were found (intensity: p < 0.01, η2p = 0.762; time: p < 0.01, η2p = 0.810; interaction: p < 0.01, η2p = 0.696). Compared with the control conditions, CMJ height after 80% VO2 max and 60% VO2 max warm-ups were significantly higher (p < 0.01 and p < 0.05, respectively). CMJ height at 20 min after warm-up was significantly higher for 80% VO2 max warm-up than for 60% VO2 max warm-up (p < 0.01). However, CMJ height at 10 min after 60% VO2 max warm-up was not significantly different from the baseline (p < 0.05). These results showed that both high and moderate intensity warm-up can maintain an increase in muscle temperature for 20 min. Jump performance after high-intensity warm-up was increased for 20 min compared to a moderate intensity warm-up.