Biomechanical characteristics of the lower extremities during running in male long-distance runners with a history of medial tibial stress syndrome: a case control study.

BACKGROUND: Medial tibial stress syndrome (MTSS) is a running-related injury of the lower extremities. After returning to competition, there are often recurring episodes of MTSS. Therefore, it is important to prevent the onset and recurrence of MTSS among long-distance runners. This case-control study aimed to compare the kinematics and kinetics of runners with and without previous MTSS during running to clarify the biomechanical characteristics of the lower extremity of runners with previous MTSS. METHODS: Thirteen male long-distance runners aged over 18 years and asymptomatic at the time of measurement were divided into an MTSS group and a non-MTSS group based on their history of MTSS as reported in a questionnaire. The kinetics and kinematics of running were analyzed when participants ran at a speed of 2.0 ± 0.2 m/s by a three-dimensional motion analysis system and two force plates. Data regarding the joint angles, moments, and powers of the ankle, knee, and hip during the stance phase while running were extracted and compared between the two groups using the Mann-Whitney U test. RESULTS: Of the 13 participants, 5 and 8 were included in the MTSS (10 legs) and non-MTSS (16 legs) groups, respectively. The ankle maximum eversion moment was significantly larger in the MTSS group than in the non-MTSS group (p = 0.04). There were no significant differences in other parameters. CONCLUSIONS: This study found that the ankle maximum eversion moment during the stance phase of running was larger in the MTSS group than in the non-MTSS group. Even after the disappearance of the symptoms of MTSS, the running biomechanics of participants with previous MTSS differed from those of participants without previous MTSS.

Kinesiophobia Is Negatively Associated With Psychological Readiness to Return to Sport in Patients Awaiting Anterior Cruciate Ligament Reconstruction.

PURPOSE: To identify the factors associated with anterior cruciate ligament return to sport after injury (ACL-RSI) scores in patients awaiting ACL reconstruction (ACLR). METHODS: This was a retrospective cross-sectional observational study conducted at a single clinical center. We recruited patients scheduled for primary ACLR, aged 16-45 years, and with modified Tegner activity scale scores ≥5 before ACL injury. The main outcome was psychological readiness to return to sport (RTS), as measured using the ACL-RSI scale. Participants' personal and injury-related information were obtained, and their psychological status (Tampa Scale for Kinesiophobia [TSK] and athletic identity measurement scale) and knee functions (effusion, range of motion, joint stability, and knee flexion angle during a single-leg squat) were examined. All variables were assessed the day before the surgery. RESULTS: A total of 105 patients (median [interquartile range]: age, 20.0 [9.0] years; body mass index, 22.8 [4.3] kg/m2; days from injury to surgery, 63.0 [65.0] days; 44% female) were enrolled. Univariate analysis indicated that only the TSK score was associated with the ACL-RSI scores (r = -0.305; P = .02). Multiple regression analysis of factors, including sex, preinjury Tegner activity scale score, and days from injury to surgery, further showed that only the TSK score was associated with the ACL-RSI scores (P = .002; 95% confidence interval -1.738 to -0.394). CONCLUSIONS: In patients awaiting ACLR, kinesiophobia was moderately negatively associated with psychological readiness to RTS, while other factors were not. LEVEL OF EVIDENCE: Level III, retrospective cross-sectional observational study.

Association Between Knee Extension Strength at 3 and 6 Months After Anterior Cruciate Ligament Reconstruction.

CONTEXT: Deficits in knee extension strength after anterior cruciate ligament reconstruction have been a major problem. The inadequate recovery of the knee extension strength of surgical limb reportedly delays return to sports and increases reinjury risk. Accordingly, the early detection of knee extension strength deficits after reconstruction may help plan early interventions to manage impairment. This study aimed to clarify the association between knee extension strength at 3 and 6 months after anterior cruciate ligament reconstruction. DESIGN: Retrospective study. METHODS: Fifty patients who underwent primary anterior cruciate ligament reconstruction using hamstring grafts were included. At 3 months postoperatively, the limb symmetry index (LSI) of isokinetic knee extension strength (IKE) at 60°/s, degree of swelling, passive range of motion of knee flexion and extension, and anterior leg reach distance were measured. At 6 months postoperatively, the LSI of IKE was measured at 60°/s, which was used as the main outcome. A correlation analysis was performed with the LSI of IKE at 6 months postoperatively as the dependent variable and the LSI of IKE at 3 months postoperatively as the independent variable. Subsequently, a multiple regression analysis was performed, with LSI of IKE at 6 months postoperatively as the dependent variable; LSI of IKE at 3 months postoperatively as the independent variable; and other variables, demographic information, and surgical data as covariates. RESULTS: The correlation analysis revealed that the LSIs of IKE at 3 and 6 months postoperatively were correlated (r = .535, P < .001). In the multiple regression analysis, the LSI of IKE at 3 months postoperatively was significantly associated with that at 6 months postoperatively, even when other variables were included as covariates (R2 = .349, P = .004). CONCLUSION: Asymmetry of knee extension strength at 3 months postoperatively could be more useful than other variables related to knee strength in predicting the asymmetry of knee extension strength at 6 months postoperatively.

Differences in gait kinetics and kinematics between patients with rotating hinge knee and cruciate-retaining prostheses: a cross-sectional study.

[Purpose] Rotating hinge knee prostheses are often used in primary total knee arthroplasty. However, the biomechanics resulting from this treatment remain unexplored. This cross-sectional study compared patient data on gait kinetics and kinematics to assess the efficacy of primary total knee arthroplasty using a rotating hinge knee or other prostheses. [Participants and Methods] Thirty-three participants were assigned to the following groups: rotating hinge knee (n=7); cruciate-retaining prosthesis (n=7); untreated osteoarthritis (n=10); and young adults as a reference group (n=9). Participant data on biomechanical and spatiotemporal parameters were analyzed. [Results] The postoperative course of the rotating hinge knee group was not significantly longer than that of the cruciate-retaining prosthesis group. The knee varus angle and adduction moment of the rotating hinge knee group were significantly smaller than those of the untreated osteoarthritis group. Gait kinetics and kinematics were not different between the rotating hinge knee and cruciate-retaining prosthesis groups. [Conclusion] Participants who had undergone primary total knee arthroplasty with a rotating hinge knee prosthesis had worse preoperative conditions and demonstrated a similar postoperative gait as those who had undergone total knee arthroplasty with other prostheses. Our findings may be used to tailor rehabilitation programs for participants who have undergone total knee arthroplasty with a rotating hinge knee implant.

Development of a Wearable Mouth Guard Device for Monitoring Teeth Clenching during Exercise.

Teeth clenching during exercise is important for sports performance and health. Recently, several mouth guard (MG)-type wearable devices for exercise were studied because they do not disrupt the exercise. In this study, we developed a wearable MG device with force sensors on both sides of the maxillary first molars to monitor teeth clenching. The force sensor output increased linearly up to 70 N. In four simple occlusion tests, the trends exhibited by the outputs of the MG sensor were consistent with those of an electromyogram (EMG), and the MG device featured sufficient temporal resolution to measure the timing of teeth clenching. When the jaw moved, the MG sensor outputs depended on the sensor position. The MG sensor output from the teeth-grinding test agreed with the video-motion analysis results. It was comparatively difficult to use the EMG because it contained a significant noise level. Finally, the usefulness of the MG sensor was confirmed through an exercise tolerance test. This study indicated that the developed wearable MG device is useful for monitoring clenching timing and duration, and the degree of clenching during exercise, which can contribute to explaining the relationship between teeth clenching and sports performance.

The Japanese version of the anterior cruciate ligament-return to sport after injury (ACL-RSI) scale has acceptable validity and reliability.

PURPOSE: The anterior cruciate ligament-return to sports after injury (ACL-RSI) scale assesses the psychological impact of returning to sports (also referred to as psychological readiness) after ACL reconstruction. The aim of this study was to evaluate important measurement properties of the Japanese version of ACL-RSI scale. METHODS: Ninety-three participants who underwent ACL reconstruction filled out the Japanese version of ACL-RSI scale, the Tampa scale for kinesiophobia (TSK), the International Knee Documentation Committee-Subjective Knee Form (IKDC-SKF), and Knee injury and Osteoarthritis Outcome Score (KOOS). To assess test re-test reliability, 50 of the 93 participants re-answered the Japanese version of ACL-RSI scale within 10 days. Floor and ceiling effects, internal consistency, construct validity, and reliability of the Japanese version of ACL-RSI scale were analysed. RESULTS: There were no floor and ceiling effects. The Japanese version of ACL-RSI scale showed good internal consistency (Cronbach's alpha = 0.912). It was positively correlated with total points of IKDC-SKF and the Lysholm score, and with the all sub-categories of the KOOS, and it was negatively correlated with the TSK. Reliability of the Japanese version of ACL-RSI scale was satisfactory. CONCLUSION: The Japanese version of ACL-RSI scale has acceptable measurement properties. It can be a useful for evaluation of psychological readiness for return to sports in Japanese athletes who undergo primary ACL reconstruction. Information provided by the Japanese version of the ACL-RSI scale may also help to identify athletes who find return to sport a challenge, and guide conversations regarding treatment and rehabilitation plans. LEVEL OF EVIDENCE: II.

Comparison of foot kinetics and kinematics during gait initiation between young and elderly participants.

[Purpose] To investigate the differences in foot kinetics during gait initiation between young and elderly participants using a modified multi-segment foot model. [Participants and Methods] Twelve young (23.3 ± 2.4 years) and 12 elderly participants (73.3 ± 3.9 years) were included in this study. Gait initiation was measured using a three-dimensional motion analysis system. We calculated the kinetic and kinematic values using our modified multi-segment foot model and compared those values with the values calculated using Bruening et al.'s multi-segment foot model. Modified gait initiation values were also compared between the elderly and young participants. [Results] Our modified multi-segment foot model, created using the Software for Interactive Musculoskeletal Modeling, showed similar values to those reported by Bruening et al. When we compared gait initiation between the elderly participants and their younger counterparts, the elderly exhibited lower torque and power values in the ankle, tarsometatarsal, and metatarsophalangeal joints. Additionally, the elderly exhibited a lower torque ratio in the distal joint than in the proximal joint (torque ratio: ankle joint >tarsometatarsal joint >metatarsophalangeal joint). [Conclusion] The elderly participants had less speed, stride, foot joint movement, moment, and power than the young participants. Moreover, the ratio of joint moment was smaller in the elderly participants. In elderly patients whose walking speed has decreased, consideration of the kinetics of the foot is important when deciding physiotherapy intervention.

Limb-dominance and gender differences in the ground reaction force during single-leg lateral jump-landings.

[Purpose] The purpose of this study was to examine limb-dominance and gender differences in the magnitude of the ground reaction force during single-leg lateral jump-landings. We hypothesized that the peak ground reaction force would be larger in the non-dominant leg compared to that in the dominant leg and would be larger in females compared to that in men. [Subjects and Methods] Fifteen females and 15 males performed jump-landings sideways from a height of 20 cm, with a lateral distance of 60 cm. Vertical and medial ground reaction forces were measured, and the elapsed time from the initial contact to the peak ground reaction force was determined. The loading rate was calculated as the peak ground reaction force divided by the elapsed time from the initial contact to the peak ground reaction force. [Results] The vertical and medial peak ground reaction forces during single-leg lateral jump-landings were larger in females compared to that in males. In addition, the medial peak ground reaction force was larger for the non-dominant leg compared to that for the dominant leg. [Conclusion] The results suggest that in rehabilitation and conditioning settings, evaluations and instructions regarding attenuation are especially important for females and the non-dominant leg.

The Effect of Teeth Clenching on Dynamic Balance at Jump-Landing: A Pilot Study.

The aim of this study was to analyze the effect of teeth clenching on dynamic balance at jump landing. Twenty-five healthy subjects performed jump-landing tasks with or without teeth clenching. The first 3 trials were performed with no instruction; subsequently, subjects were ordered to clench at the time of landing in the following 3 trials. We collected the data of masseter muscle activity by electromyogram, the maximum vertical ground reaction force (vGRFmax) and center of pressure (CoP) parameters by force plate during jump-landing. According to the clenching status of control jump-landing, all participants were categorized into a spontaneous clenching group and no clenching group, and the CoP data were compared. The masseter muscle activity was correlated with vGRFmax during anterior jump-landing, while it was not correlated with CoP. In comparisons between the spontaneous clenching and the no clenching group during anterior jump-landing, the spontaneous clenching group showed harder landing and the CoP area became larger than the no clenching group. There were no significant differences between pre- and postintervention in both spontaneous clenching and no clenching groups. The effect of teeth clenching on dynamic balance during jump-landing was limited.

Differences in lower extremity kinematics during single-leg lateral drop landing of healthy individuals, injured but asymptomatic patients, and patients with chronic ankle instability- a cross-sectional observational study.

The lower-extremity kinematics associated with forward jump landing after an ankle injury is known to differ for patients with Chronic Ankle Instability (CAI), copers (injured but asymptomatic patients), and healthy individuals. However, the differences in the lower extremity kinematics of these groups associated with a Single-leg Lateral Drop Landing (SLDL) are unknown. The purpose of this study is to characterize the lower limb and foot kinematics during SLDL in CAI patients and to compare these characteristics with those of the copers and healthy individuals. This was a cross-sectional observational study. Nineteen participants, each, were selected from the CAI, Coper, and control groups. The lower-extremity kinematics during SLDL was measured using three-dimensional motion analysis over an interval progressing from 200 ms before landing to 200 ms after landing. Either one-way ANOVA or the Kruskal-Wallis test was used to compare the attributes of the respective groups, with each parameter measured every 10 ms. The maximum values and excursions of the parameters were established over time intervals progressing from 200 ms before landing to 200 ms after landing. Significant observations were subjected to post hoc analysis. Compared to the Coper group, the CAI group exhibited significantly smaller hip adduction angles at 160 ms, ankle dorsiflexion angles in the 110-150 ms interval, and maximum ankle dorsiflexion angles after landing. Compared to the control group, the CAI group exhibited significantly smaller excursions of MH inversion/eversion after landing. Our findings confirm the necessity of focusing on the kinematics of hip adduction/abduction and plantar/dorsiflexion during SLDL in evaluating patients with ankle injuries.

Gait analysis of patients with knee osteoarthiritis who can run versus cannot run.

BACKGROUND: Many middle-aged and older adults participate in running to maintain their health and fitness; however, some have to stop running due to osteoarthritis-attributed knee pain. It was unclear whether gait biomechanics and knee physical findings differ between those who can and cannot run. RESEARCH QUESTION: What are the gait and knee physical findings of patients with knee osteoarthritis who remain capable of running in comparison to those who are not capable of running? METHODS: This was a cross-sectional study, which recruited 23 patients over the age of 40 who had been diagnosed with knee osteoarthritis. Their knee joint ranges of motion and muscle strength, knee pain, and the maximum gait speed (walk as fast as possible) were measured. Knee alignment was calculated from X-ray images, and the knee joint extension angle and adduction moment during a self-selected gait speed were determined using motion analysis. Participants were divided into two groups-those able to run (n=11) and those unable to run (n=12). The measured and calculated outcomes were compared between groups, and logistic regression analyses of significantly different outcomes were performed. RESULTS: There were significant group differences in the maximum knee extension angle during stance phase (p = 0.027), maximum gait speed during the 10-m walk test (p = 0.014), knee pain during gait (p = 0.039) and medial proximal tibial angle by X-ray (p = 0.035). Logistic regression analyses revealed that the maximum knee extension angle during stance phase (OR: 1.44, 95%CI: 1.06¬1.94, p = 0.02) was a significant factor. SIGNIFICANCE: The ability to extend the knee during gait is an important contributing factor in whether participants with knee osteoarthritis are capable of running.

Anterior Cruciate Ligament-Return to Sport after Injury (ACL-RSI) subcategories are affected by subjective running ability and medial single-leg hop distance in postreconstruction patients at 6 months.

Purpose: This study aimed to investigate the intricate relationship between physical function factors and each subcategory score of the Anterior Cruciate Ligament-Return to Sport after Injury (ACL-RSI) scale among patients following ACL reconstruction. Methods: Participants comprised 59 patients who had undergone primary ACL reconstruction using hamstring tendon. The ACL-RSI was completed 6 months after reconstruction and five physical functions were measured in patients on the same day. Simple linear regression was performed multiple times to investigate the relationship between ACL-RSI subcategory scores as a dependent variable and each independent variable (knee strength, leg anterior reach distance, single-leg hop [SLH] distances, side bridge endurance, and subjective running ability). Multiple regression analysis was performed using a stepwise method, with factors showing a risk rate <0.05 in simple linear regression analyses as independent variables and the ACL-RSI in each subcategory score as the dependent variable. Results: Multiple regression analysis showed that subjective running ability affected all subcategories (p ≤ 0.001), and that the limb symmetry index of medial SLH distance affected both the Emotions (p = 0.047) and Confidence (p = 0.009) subcategories. Higher subjective running ability and greater limb symmetry in the medial SLH were thus positively associated with each dimension of psychological readiness. Conclusions: This study highlights the differential impact of physical function factors on specific subcategories of the ACL-RSI scale, providing clinicians with insights for designing targeted rehabilitation strategies. This original paper suggests the importance of analysing factors related to subcategory scores in addition to total ACL-RSI score, and could contribute to the understanding of determinants for a successful return to sport following ACL reconstruction. Level of Evidence: Level IV.

Effects of differences in femoral anteversion and hip flexion angle on hip abductor muscles activity during clam exercise in females.

This study aimed to determine differences in the hip abductor muscle activity during clam exercise at different hip flexion and femoral anteversion angles. Thirty healthy females were divided into two groups based on the femoral anteversion angle: the excessive femoral anteversion group and the normal group. Clam exercise was performed at three different hip flexion angles (60°, 45°, and 30°). Tensor fascia latae, gluteus medius, and superior portion of gluteus maximus activities were measured during the exercise, and the results were normalized to the activity during maximum voluntary isometric contraction to calculate the gluteal-to-tensor fascia latae muscle activation index. The superior portion of gluteus maximus activities at a hip flexion of 60° and 45° were greater than that at 30°. The excessive femoral anteversion group had a lower gluteal-to-tensor fascia latae muscle activation index than the normal group; the gluteal-to-tensor fascia latae muscle activation index for hip flexion at 60° was higher than that at 45°, and the gluteal-to-tensor fascia latae muscle activation index for hip flexion at 60° and 45° were higher than that at 30°. Therefore, the femoral anteversion angle and hip joint position were related to the activity of the hip abductor muscles during clam exercise. These findings may provide a rationale for instructing exercises to maximize the activity of the hip abductor muscles in individuals with an excessive femoral anteversion angle.

Association between landing biomechanics, knee pain, and kinesiophobia in athletes following anterior cruciate ligament reconstruction: A cross-sectional study.

INTRODUCTION: Kinesiophobia is a fear of physical movement and activity and is known to affect return to sports and second injury after anterior cruciate ligament reconstruction. OBJECTIVE: To determine the association among landing biomechanics, knee pain, and kinesiophobia in athletes following anterior cruciate ligament reconstruction. DESIGN: A cross-sectional study. SETTING: Clinical center of sports medicine. PARTICIPANTS: This study included 31 athletes who participated in sports after primary, unilateral anterior cruciate ligament reconstruction (age, median [interquartile range]: 20.0 [7.0] years; body mass index: 22.2 [2.6] kg/m2 ; time from anterior cruciate ligament reconstruction: 24.0 [23.0] months). INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Kinesiophobia was measured using the Tampa Scale for Kinesiophobia-11. Knee function included joint laxity, strength, and single-leg hop distance. Knee pain intensity during sports activities was measured using a numerical rating scale. Vertical ground reaction force was measured, and electromyography data for the vastus medialis and semitendinosus muscles during single-leg jump landing were collected. Univariate correlation analysis and multiple regression analysis were performed to identify the associations between the Tampa Scale for Kinesiophobia-11 score and outcome measures. RESULTS: There was no correlation between peak vertical ground reaction force and Tampa Scale for Kinesiophobia-11 score (Spearman's r = -0.17, p = .355). On multiple regression analyses, lower preparatory vastus medialis activity during landing (beta coefficient = -0.51, p < .001) and knee pain intensity (beta coefficient = 0.57, p < .001) were significantly associated with greater Tampa Scale for Kinesiophobia-11 scores. CONCLUSIONS: In athletes who have participated in sports following anterior cruciate ligament reconstruction, lower preparatory vastus medialis activity during landing and knee pain intensity are associated with greater kinesiophobia. These findings indicate that interventions to address the landing muscle activity pattern and pain control should be performed to decrease kinesiophobia after anterior cruciate ligament reconstruction.

Changes in subjective knee function and psychological status from preoperation to 6 months post anterior cruciate ligament reconstruction.

PURPOSE: To determine characteristic changes in subjective knee function, kinesiophobia, and psychological readiness to return to sports between scores taken before anterior cruciate ligament reconstruction (ACLR) and those taken 6 months post-ACLR. METHODS: Thirty-two participants (median age, 20.0 years) were included. Subjective knee function was assessed using the International Knee Documentation Committee Subjective Knee Form (IKDC-SKF). The Tampa Scale for Kinesiophobia (TSK-11) and Anterior Cruciate Ligament Return to Sport after Injury (ACL-RSI) scale were used to evaluate kinesiophobia and psychological readiness to return to sport, respectively. Questionnaires were administered 1 day before surgery and at 6 months post-ACLR. A positive change was defined as an increase in IKDC-SKF and ACL-RSI scores and a decrease in TSK-11 score. The change in each score from pre-ACLR to 6 months post-ACLR was analyzed using a paired t-test. The percentage change in scores was calculated, and the correlations of the percentage change in the TSK-11 and ACL-RSI scores and that in the IKDC-SKF score were analyzed. RESULTS: All scores differed significantly positively from pre-ACLR to 6 months post-ACLR. The proportion of participants whose scores did not change positively from pre-ACLR to 6 months post-ACLR was higher for the TSK-11 (38.0%) and ACL-RSI (38.0%) than for the IKDC-SKF (6.3%). No correlation was observed between the percentage change in the IKDC-SKF score and that in the TSK-11 or ACL-RSI scores from pre-ACLR to 6 months post-ACLR. CONCLUSIONS: Changes in subjective knee function and psychological status from pre-ACLR and 6 months post-ACLR may not be interdependent.

Cross-sectional study on relationships between physical function and psychological readiness to return to sport after anterior cruciate ligament reconstruction.

BACKGROUND: Information about specific factors of physical function that contribute to psychological readiness is needed to plan rehabilitation for a return to sports. The purpose of this study was to identify specific physical functions related to the psychological readiness of patients aiming to return to sports 6 months after reconstruction. We hypothesized that the knee strength is a factor related to the Anterior Cruciate Ligament-Return to Sport after Injury scale (ACL-RSI) cutoff score for a return to sports. METHODS: This was a cross-sectional study. Fifty-four patients who had undergone primary reconstruction using hamstring tendon participated in this study. Psychological readiness was measured using the ACL-RSI in patients at 6 months after reconstruction. To identify specific physical functions related to the ACL-RSI score, participants were divided into groups with ACL-RSI scores of ≥ 60 or < 60. Non-paired t-tests or the Mann-Whitney test were performed to analyze group differences in objective variables in physical function: (1) knee strength in both legs; (2) leg anterior reach distance on both sides; and (3) single-leg hop (SLH) distances in three directions for both legs. RESULTS: Significant differences between groups were identified in knee flexion strength (60°/s) for the uninvolved limb, hamstring-to-quadriceps ratio (60°/s) for the uninvolved limb, knee flexion strength (180°/s) for the involved limb, limb symmetry index (LSI) of leg anterior reach distance, the ratio of the distance to the height of the patient and LSI of SLH distances in lateral and medial directions. CONCLUSION: This study revealed that at 6 months after reconstruction, increased knee flexion strength (ratio of peak torque measured to body mass of the patient), hamstring-to-quadriceps ratio, leg anterior reach distance LSI, and lateral and medial SLH appear important to exceed the ACL-RSI cutoff for a return to sports. The present results may be useful for planning post-operative rehabilitation for long-term return to sports after reconstruction.

Movement patterns of the functional reach test do not reflect physical function in healthy young and older participants.

The relationship of the Functional Reach Test (FRT) value with the Center of Pressure Excursion (COPE) and physical function remains unclear, and would be influenced by different population characteristics and movement patterns used in the FRT. Therefore, we explored the relationship between the FRT value and the COPE and physical function in healthy young and older individuals classified according to movement patterns. In 21 healthy young participants (42 sides) and 20 older participants (40 sides), three-dimensional motion analysis was performed during the FRT and physical function assessments. The participants were assigned to two clusters after performing a motion analysis during the FRT. Kinematic and kinetic parameters during the FRT and physical function assessment results were compared between the clusters for both groups. Correlation analysis was performed to investigate the relationships of the FRT value with COPE and physical function parameters in each cluster, in young and older individuals separately. The results showed that the hip strategies could be divided into two groups according to the degree of use (Small Hip Strategy, SHS Group; Large Hip Strategy, LHS Group). In the older SHS group, the FRT values were significantly correlated with the COPE (r = 0.75), toe grip strength (r = 0.62), and the five-times sit-to-stand test time (r = -0.52). In the older LHS group and in both groups of young individuals, there were no significant correlations of the FRT value with any parameters. The FRT value reflects the COPE and physical function only in older individuals using the SHS. This could explain previous discrepant results. As there is no simple relationship between the FRT value and physical function, it is important to include movement strategy assessment when using the FRT in clinical evaluations.

Reactive strength index during single-limb vertical continuous jumps after anterior cruciate ligament reconstruction: cross-sectional study.

BACKGROUND: The association of the reactive strength index (RSI) during single-limb vertical continuous jumps (SVCJs) with single-limb hop tests in athletes after anterior cruciate ligament reconstruction (ACLR) is unclear. Thus, this study aimed to confirm the measurement properties of the RSI during SVCJs in athletes with ACLR at the phase of determining the timing of their return to sport. METHODS: RSI during SVCJs and single-limb hop (single, triple, and crossover) tests were measured for post-ACLR and healthy athletes. The limb symmetry index (LSI) was calculated using the measurements of each parameter. For each test, patients were divided into two subgroups according to their LSI score (≥ 90%, satisfactory; < 90%, unsatisfactory). Fisher's exact test was used to examine the association of single-limb hop tests with RSI during the SVCJs. RESULTS: A total of 21 post-ACLR and 17 healthy athletes completed all the tests. RSI during SVCJs was significantly lower on the involved limb than on the uninvolved limb in post-ACLR athletes (P < 0.001). The LSI of RSI during SVCJs of post-ACLR athletes was significantly lower than that of the healthy athletes (P < 0.01). Among the post-ACLR athletes, < 30% of those with LSIs > 90% in the single-limb hop tests had an LSI > 90% of the RSI during SVCJs. CONCLUSIONS: RSI during SVCJs of post-ACLR athletes was significantly lower on the involved limb than on the uninvolved limb, and the asymmetry was more remarkable in the SVCJs than in the single-limb hop tests.

Characteristics of ground reaction force and frontal body movement during failed trials of single-leg lateral drop jump-landing task.

BACKGROUND: /objectives: For biomechanical studies using jump-landing tasks, many researchers set the criteria for judging success or failure of the trial. Failed trials are usually removed from the analysis. However, the kinetics and kinematics during tasks included in failed trials might be important for understanding the mechanisms and risk factors of non-contact sports injuries. However, few studies have attempted to analyze failed trials. Therefore, the main objective of this study was to investigate the characteristics associated with ground reaction force (GRF) and two-dimensional frontal body movements during a failed trial of single-leg lateral drop jump-landing. METHODS: Ten healthy women and 16 healthy men participated in this study. Spearman's rank correlation coefficients were calculated using the total number of failed trials and GRF data of successful trials. The association between frontal body movement and kinetics data was identified using correlation analyses. Wilcoxon signed-rank tests were performed to compare the GRF data of successful trials and failed trials of the same subject. Additionally, a two-way repeated measure analysis of variance was used to determine significant interactions of each trial and time after initial contact in the frontal body movement. RESULTS: A total of 137 trials including successful and failed trials were recorded. There were 59 failed jump trials. There was a significant negative correlation between the number of failed jump trials and the elapsed time from initial contact to peak vertical GRF (peak vGRF time) during successful trials (r = -0.427). The majority of failed trials were judged to be due to rearfoot movement patterns (rearfoot medial slip or rearfoot lateral slip). During rearfoot medial slip, we observed shorter peak vGRF time, larger trunk medial motions, and larger hip adduction movements after landing than that during successful trials. During rearfoot lateral slip, we observed larger trunk lateral motions and hip abduction movements after landing than that during successful trials. CONCLUSIONS: Athletes who frequently failed during single-leg lateral drop jump-landing had poor skills absorbing jump-landing impact, which is related to various sports injuries. It is possible to identify the risk factors for sports injuries by analyzing failure patterns.

Correlations between isokinetic knee torques and single-leg hop distances in three directions in patients after ACL reconstruction.

BACKGROUND: When planning rehabilitation and conditioning for performance enhancement and a return to sports after anterior cruciate ligament reconstruction, identifying the elements of physical function associated with single-leg hop is important. The purpose of this study was to clarify the relationship between single-leg hop distances in three directions and knee extensor and flexor strengths at 6 months after reconstruction. METHODS: Participants were 47 patients taking part in training sessions for sports involving cutting, pivoting, and jump-landing 6 months after reconstruction using a hamstring tendon. Single-leg hop distances in 3 directions (anterior, lateral, and medial) and isokinetic concentric strengths of knee extension and flexion were assessed at an angular velocity of 60°/s and 180°/s. Simple regression analyses using Spearman's rank correlation coefficient were performed to assess relationships between single-leg hop distances and knee strengths. RESULTS: In the involved limb, correlations between single-leg hop distances in 3 directions and knee strengths were significant (P < 0.01) and correlation coefficients ranged from 0.48 to 0.65. Correlation coefficients between all single-leg hop parameters and knee extension/flexion strengths at an angular velocity of 180°/s were greater than those of 60°/s. CONCLUSIONS: In this cross-sectional study of patients who participated in sports training sessions that required jump-landings and cutting approximately 6 months after reconstruction using hamstring grafts, isokinetic knee flexor, and extensor torques were moderately to strongly associated with single-leg hop distances in lateral, medial, and anterior directions. Given these relationships, assessments and exercises for knee strength and single-leg hop distances should be planned.