Peak Vertical Ground Reaction Force Research Articles

Accurate estimation of peak vertical ground reaction force using the duty factor in level treadmill running.

This study aimed to (1) construct a statistical model (SMM) based on the duty factor (DF) to estimate the peak vertical ground reaction force ( ) and (2) to compare the estimated to force plate gold standard (GSM). One hundred and fifteen runners ran at 9, 11, and 13 km/h. Force (1000 Hz) and kinematic (200 Hz) data were acquired with an instrumented treadmill and an optoelectronic system, respectively, to assess force-plate and kinematic based DFs. SMM linearly relates to the inverse of DF because DF was analytically associated with the inverse of the average vertical force during ground contact time and the latter was very highly correlated to . No systematic bias and a 4% root mean square error (RMSE) were reported between GSM and SMM using force-plate based DF values when considering all running speeds together. Using kinematic based DF values, SMM reported a systematic but small bias (0.05BW) and a 5% RMSE when considering all running speeds together. These findings support the use of SMM to estimate during level treadmill runs at endurance speeds if underlying DF values are accurately measured.

Understanding the influences on horizontal jump landing mechanics: A systematic review

Horizontal jumps have been used to assess pathological landing mechanics and as a plyometric conditioning exercise. Investigations have yet to clarify what and how varying jump characteristics influence landing mechanics. A search of Medline, CINAHL, Embase, Scopus and SPORTDiscus was conducted. Included articles were original published research articles, which reported 3D kinetic or kinematic measurements on landing, from bilateral horizontal jumps in healthy adult populations. Nine articles met inclusion criteria and demonstrated a satisfactory to low risk of bias. Kinematic and kinetic landing data for bilateral horizontal jumps were extracted and analysed. The addition of a subsequent jump on landing reduced peak vertical ground reaction force (GRF), and addition of a heading task reduced landing hip and knee joint flexion. Greater magnitude jumps increased knee joint flexion. Horizontal jump tasks which restricted arm swing produced less peak vertical GRF. Bilateral horizontal jumps described as having higher peak vertical trajectories appeared to be associated with reduced hip flexion on landing. These findings highlight the importance of considering jump characteristics when designing bilateral horizontal jump tasks. Further research on landing performance following bilateral horizontal jumps is required to strengthen findings and should include measures of flight trajectory.

Gender Comparisons and Associations between Lower Limb Muscle Activation Strategies and Resultant Knee Biomechanics during Single Leg Drop Landings

(1) Background: We aimed to compare gender differences in knee biomechanics and neuromuscular characteristics, and to determine the relationships between lower limb muscle pre-activations and knee biomechanics during a single leg drop landing, in order to identify riskier landing patterns to prevent injury and intervene properly. (2) Methods: Descriptive laboratory cross-sectional study on 38 healthy untrained subjects with low to moderate physical activity status. (3) Results: During the initial-contact phase of landing, females demonstrated greater peak vertical ground reaction force (GRF) normalized to body weight (49.12 ± 7.53 vs. 39.88 ± 5.69 N/kg; p < 0.001; Hedge’s g = 1.37), peak knee anterior reaction force normalized to body weight (0.23 ± 0.04 vs. 0.17 ± 0.05 N/kg; p < 0.001; Hedge’s g = 1.33), and decreased pre-activation of the semitendinosus (45.10 ± 20.05% vs. 34.03 ± 12.05%; p = 0.04; Hedge’s g = 0.67). The final regression equation was peak knee anterior reaction force = 0.024 + 0.025 (peak knee flexion moment) − 0.02 (semitendinosus-to-vastus lateralis pre-activation ratio) + 0.003 (peak vertical GRF) (R2 = 0.576, p < 0.001). (4) Conclusions: Overall, the data provided in this study support that a reduced semitendinosus-to-vastus lateralis pre-activation ratio predicted an increase in knee anterior reaction force and potentially an increase in ACL forces. Female non-athletes had gender-specific landing characteristics that may contribute to ACL injury. Future studies are warranted to consider more possible predictors of non-contact ACL injury.

Influence of body mass index and anterior cruciate ligament reconstruction on gait biomechanics.

Body mass index (BMI) and history of anterior cruciate ligament reconstruction (ACLR) independently influence gait biomechanics and knee osteoarthritis risk, but the interaction between these factors is unclear. The purpose of this study was to compare gait biomechanics between individuals with and without ACLR, and with and without overweight/obesity. We examined 104 individuals divided into four groups: with and without ACLR, and with low or high BMI (n = 26 per group). Three-dimensional gait biomechanics were evaluated at preferred speed. The peak vertical ground reaction force, knee flexion angle and excursion, external knee flexion moment, and external knee adduction moment were extracted for analysis. Gait features were compared between groups using 2 (with and without overweight/obesity) × 2 (with and without ACLR) analysis of variance. Primary findings indicated that those with ACLR and high BMI had a larger external knee adduction moment compared with those with low BMI and with (p = 0.004) and without ACLR (p = 0.005), and compared with those without ACLR and high BMI (p = 0.001). The main effects of ACLR and BMI group were found for the knee flexion moment, and those with ACLR and with high BMI had lower knee flexion moments compared with those without ACLR (p = 0.031) and with low BMI (p = 0.021), respectively. Data suggest that individuals with ACLR and high BMI may benefit from additional intervention targeting the knee adduction moment. Moreover, lower external knee flexion moments in those with high BMI and ACLR were consistent, but high BMI did not exacerbate deficits in the knee flexion moment in those with ACLR. [Correction added on 9 November 2022, after first online publication: In the preceding sentence, for clarity, the words "reductions in the lower" was removed from the initial sentence to read "Moreover, lower external knee flexion moments".].

The influence of surface and speed on biomechanical external loads obtained from wearable devices in rearfoot strike runners

ABSTRACT External load variables such as peak tibial acceleration (PTA), peak vertical ground reaction forces (GRF) and its instantaneous vertical loading rate (IVLR) may contribute to running injuries although evidence is conflicting given the influence of training load and tissue health on injuries. These variables are influenced by footwear, speed, surface and foot strike pattern during running. The purpose of this study was to assess the influence of four surfaces and two running speeds on external load variables in rearfoot strike (RFS) runners. Twelve RFS runners (confirmed with sagittal foot contact angle) completed a 2-min running bout on a treadmill and 50-m running bouts over the three surfaces (pavement, rubber track and grass) in standardised shoes at their preferred speed and 20% faster. PTA and vertical GRFs were collected using inertial measurement units and in-shoe force insoles. No interaction or surface effects were observed (p > 0.017). The faster speed produced greater axial PTA (+19.2%; p < 0.001), resultant PTA (+20.7%; p < 0.001), peak vertical GRF (+6.6%; p = 0.002) and IVLR (+16.5%; p < 0.001). These findings suggest that surface type does not influence PTA, peak vertical GRF and IVLR but that running faster increases the magnitude of these external loads regardless of surface type in RFS runners.

Lower Limb Ground Reaction Force and Center of Pressure Asymmetry During Bodyweight Squats.

BackgroundPerformance asymmetries between the lower limbs have been reported across a variety of variables and for numerous motor tasks including double leg squats. Additionally, the degree of symmetry is often used as a recovery metric during rehabilitation programs.Hypothesis/PurposeThe purpose of this investigation was to examine leg asymmetry during a bodyweight double leg squat task and assess the effects of squat speed in a physically active population.Study DesignCross-over Study Design.MethodsEighteen healthy individuals completed two sets of 20 squats at two tempos (preferred tempo and 60 bpm) while ground reaction force and center of pressure data were recorded using dual force plates. Peak vertical ground reaction force, force impulse, and center of pressure (COP) standard deviation in the anterior-posterior (AP) and mediolateral (ML) direction were calculated and analyzed to identify any differences between legs, tempo, and as a function of repetitions. Significance was set at ρ ≤ .05.ResultsThe subjects exhibited greater ground reaction forces during the self-paced tempo compared to the metronome-paced tempo (F1,79 = 14.48, p < .001) with the preferred leg generating larger values than the non-preferred leg during the self-paced condition. There was also a significant tempo x leg interaction for force impulse (F1,79 = 5.927, p = 0.015). A greater amount of COP variability was found in the preferred leg compared to the non-preferred leg in both the AP (F1,79 = 30.147, p < 0.001) and ML (F1,79 = 41.204, p < 0.001) directions.ConclusionsThese findings highlight the importance of considering multiple levels of analysis when assessing lower limb symmetry as separate variables may provide differential evidence for asymmetry. Practically, these results emphasize the need for coaches and practitioners to consider different degrees of lower limb asymmetries that may impact the development and design of strength and rehabilitation programs.Level of Evidence3

The Influence of Footwear Longitudinal Bending Stiffness on Running Economy and Biomechanics in Older Runners

ABSTRACTPurpose: This study assessed the effects of footwear longitudinal bending stiffness on running economy and biomechanics of rearfoot striking older runners. Methods: Nine runners over 60 years of age completed two running bouts at their preferred running pace in each of three footwear conditions: low (4.4 ± 1.8 N·m-1), moderate (5.7 ± 1.7 N·m-1), and high (6.4 ± 1.6 N·m-1) bending stiffness. Testing order was randomized and a mirror protocol was used (i.e., A,B,C,C,B,A). Expired gases, lower limb kinematics, and ground reaction forces were collected simultaneously and lower limb joint kinetics, running economy (i.e., VO2), leg stiffness, and spatio-temporal variables were calculated. Results: Running economy was not different among stiffness conditions (p = 0.60, p = 0.53 [mass adjusted]). Greater footwear stiffness reduced step length (p = 0.046) and increased peak vertical ground reaction force (p = 0.019) but did not change peak ankle plantarflexor torque (p = 0.65), peak positive ankle power (p = 0.48), ankle positive work (p = 0.86), propulsive force (p = 0.081), and leg stiffness (p = 0.46). Moderate footwear stiffness yielded greater peak negative knee power compared to low (p = 0.04) and high (p = 0.03) stiffness. Conclusions: These novel findings demonstrate that increasing footwear longitudinal bending stiffness using flat carbon fiber inserts does not improve running economy and generally does not alter lower limb joint mechanics of rearfoot strike runners over 60 years. Future studies should investigate how other footwear characteristics (e.g., midsole material, plate location, and sole curvature) influence economy and biomechanics in this population.

Total Support Moment Analysis Of The Stop-jump Task In Individuals Following Anterior Cruciate Ligament Reconstruction

Purpose: To examine total support moment in the sagittal plane and individual contribution from each joint during a dynamic sport task to understand the presence of compensatory strategies in a cohort of individuals who have undergone anterior cruciate ligament reconstruction (ACLR) and have been cleared for return-to-sport (RTS) Methods: Twenty-six individuals with unilateral ACLR and RTS clearance participated in the study (20.9 ± 6.6 years; 10.0 ± 1.7 months since surgery). Each participant completed a single-leg and double-leg stop jump task. These tasks were assessed using force plates and a 3D motion analysis system. Bilateral internal hip flexor/extensor, knee flexor/extensor, and ankle plantarflexor/dorsiflexor moments were calculated at peak vertical ground reaction force. The total support moment was calculated by summing these moments for each leg and the individual percent contribution was calculated. Paired t-tests were used to assess between-limb differences for each stop jump task in the following variables of interest: total support moment; hip, knee and ankle joint contributions to the total support moment; hip, knee and ankle moments; and peak vertical ground reaction force. Wilcoxon Signed Rank tests were used to compare variables that were not normally distributed. Statistical significance was set a priori at <0.05. Results: Internal knee extensor moment was lower in the involved limb compared to the uninvolved for both tasks (17.6%, P = 0.022; 18.4%, P = 0.008). The involved limb exhibited 18.2% decrease in knee joint contribution (P = 0.01) and 21.6% increase in ankle joint contribution (P = 0.016) to the total support moment compared to the uninvolved limb in the single-leg stop jump task. No significant between-limb differences were found for the total support moment. Conclusion: Following clearance for RTS, altered knee loading is still observed. These results suggest that compensation for the involved knee is likely due to redistribution of load to the knee of the uninvolved limb or to adjacent joints of the involved limb. A partial shift in joint contribution from the knee to the ankle during the single-leg stop jump task demonstrates intralimb compensation. Further studies are needed to investigate how these adaptations impact the prevalence of subsequent injury and poor joint health.

Effects Of Reducing Vertical Ground Reaction Forces On Metabolic Energy Expenditure During Loaded Treadmill Walking

Metabolic energy expenditure (MEE) is a primary determinant of gait, and joint loading may be as well. Externally loading an individual may require balancing these determinants when walking. PURPOSE: The purpose of this study was to investigate the effects of reducing vertical ground reaction forces (vGRF) through feedback on gross metabolic power. We hypothesized that reducing vGRF would come at the cost of greater MEE. METHODS: Twelve healthy participants (6 males [BMI = 22.19 ± 1.57]; 6 females [BMI = 20.12 ± 1.33]) between 20-25 years of age completed three 10-minute walking trials on an instrumented treadmill at 1.4 m·s-1 with no load, 15% body-weight (BW) and 30% BW (weighted vest). The participants received no feedback for the first five minutes, then during the second five minutes, they were told to lower peak vertical ground reaction forces based on visual feedback of those forces. Expired gases were collected to estimate MEE using the Brockway equation, then normalized by body mass (BM) and body mass plus external load (BMEL). A 2-way ANOVA (p < 0.05) was used to compare main effects of feedback and load for each of the load normalizations. RESULTS: The feedback conditions had significantly greater MEE than no feedback across the different loads (p < 0.001) for both normalization methods (Fig 1). The MEE increased significantly with greater loads for feedback and no-feedback with BM normalization (p < 0.001) but did not differ significantly with BMEL normalization (p = 0.177) (Fig 1). CONCLUSION: As participants tried to lower peak vertical ground reaction forces, MEE increased, suggesting an interaction of loads and MEE while walking. Similar to previous studies, MEE increases when deviating from preferred gait mechanics. We found that when accounting for the BMEL, MEE decreased as external load increased, that is opposite to BM normalization alone. Including BMEL may allow better understanding about how we metabolically accommodate to increasing loads.

Effects Of Fatigue On Lower Extremity Kinetics And Kinematics In Jump-stop Tasks

Non-contact anterior cruciate ligament (ACL) injury is common among athletes. Sudden deceleration in basketball competitions is closely related to non-contact ACL injury. Fatigue has also been considered one of potential injury risk factors according to epidemiological statistics. PURPOSE:To simulate the actual fatigue in basketball competitions and investigate the changes of injury-related lower extremity biomechanical characteristics. METHODS:Twelve male basketball players (age: 20.1 ± 0.6 years old; height: 1.8 ± 0.1 m; weight: 71.4 ± 13.5 kg) were recruited to executive a basketball-specific fatigue protocol. The fatigue protocol consists of a sequence including sprinting, cutting and consecutive vertical jumps. Participants repeated this sequence until they were unable to reach 80% of the maximal height. Participants were required to perform 6 trials of jump-stop tasks before and immediately after the fatigue protocol. Eight high-speed cameras (Motion Analysis Raptor- 4, USA) sampling at 200 Hz were used to collect joint angles. Two force plates (Kistler 9281CA, Switzerland) sampling at 1000 Hz were used to collect ground reaction forces. Joint net moment was calculated by inverse dynamics. All data was smoothed by 13.3 Hz Butterworth low-pass filter with Cortex 2.6. Paired t-test was performed (α =0.05) with SPSS 24.0. RESULTS:Knee flexion angle (73.52 ± 12.21, P = 0.034, Cohen’s d = 1.243) significantly increased post-fatigue at peak stance, so was the approach speed at initial contact (2.78 ± 0.51, P = 0.003, Cohen’s d = 1.333). A decreased hip abduction angle (-7.67 ± 8.57, P = 0.010, Cohen’s d = 0.577) was significantly observed post-fatigue at initial contact. Participants landed with increased vertical ground reaction force (0.245 ± 0.063(BW), P = 0.031, Cohen’s d = 0.667) in kinetics, but the posterior ground reaction force significantly decreased (0.005 ± 0.012(BW), P = 0.014, Cohen’s d = -0.6) at peak vertical ground reaction force. No fatigue-induced difference of lower extremity moment was found in this study. CONCLUSIONS:The influence of fatigue on both kinematics and kinetics of lower extremity during jump-stop tasks indicates an increased ACL injury risk. Research supported by the Education Social Science Foundation Project of the 13th Five-Year Plan of Education in China (BLA180218).

Anterior Cruciate Ligament Reconstruction And Alterations In Biomechanical Landing-stability And Decision-making Quality During Unanticipated Jump-landings

In team sports such as football, athletes are often required to adapt their motor plans in response to unpredictable/unanticipated visual information on the playing field under time pressure. These unanticipated movements lead to high-risk knee mechanics (landing safety decrements) which elevates injury/re-injury risk compared to pre-planned tasks. PURPOSE: To compare the magnititude of landing safety decrements (‘unanticipated-landing costs’) in athletes with and without a history of anterior cruciate ligament (ACL) reconstruction. METHODS: Matched-paired cross-sectional data from 14 ACL-reconstructed (females: n = 6, mean age: 23 ± 5 SD, BMI: 23 ± 4 Kg/m2, Tegner activity score (TAS): 8 ± 1; time since surgery: <2 years) and 14 healthy individuals (females: n = 6, mean age: 26 ± 3, BMI: 22 ± 2 Kg/m2, TAS: 8 ± 2) were analyzed. Participants performed countermovement-jumps with pre-planned or unanticipated single-leg landings on force plates. Landing kinetics (peak vertical ground reaction forces; pGRF), postural landing stability (center of pressure, time to stabilization), and decision-making quality (number of landings on wrong foot) were assessed. RESULTS: In both groups, the unanticipated condition resulted in significantly higher pGRF (ACL: 52 ± 4 vs. 56 ± 5 N/Kg, p = 0.004; Controls: 55 ± 7 vs. 59 ± 5 N/Kg, p = 0.021) and decision errors (ACL: 0 ± 0 vs. 3.2 ± 2, p = 0.001; Controls: 0 ± 0 vs. 2.1 ± 1.7, p = 0.003) compared to the pre-planned condition. The magnitude of unanticipated-landing costs did not differ significantly between groups (p > 0.05) for all the outcomes assessed. CONCLUSION: Unanticipated-landing costs occurred in both groups, but their magnitude was not significantly higher in the ACL-reconstructed group. To further elucidate the ACL-injury/re-injury risk associated with unanticipated movements, future biomechanical studies measuring joint kinetics and kinematics are warranted.

ACL Research Retreat IX March 17–19, 2022 High Point, NC

ACL Research Retreat IX March 17–19, 2022 High Point, NC

The Influence on Post-Activation Potentiation Exerted by Different Degrees of Blood Flow Restriction and Multi-Levels of Activation Intensity.

(1) Background: To explore the influence on post-activation potentiation (PAP) when combining different degrees of blood flow restriction (BFR) with multi-levels of resistance training intensity of activation. (2) Purpose: To provide competitive athletes with a more efficient and feasible warm-up program. (3) Study Design: The same batch of subjects performed the vertical jump test of the warm-up procedure under different conditions, one traditional and six BFR procedures. (4) Methods: Participants performed seven counter movement jump (CMJ) tests in random order, including 90% one repetition maximum (1RM) without BFR (CON), and three levels of BFR (30%, 50%, 70%) combined with (30% and 50% 1RM) (BFR-30-30, BFR-30-50, BFR-50-30, BFR-50-50, BFR-70-30 and BFR-70-50). Jump height (H), mean power output (P), peak vertical ground reaction force (vGRF), and the mean rate of force development (RFD) were recorded and measured. (5) Results: Significantly increasing results were observed in: jump height: CON (8 min), BFR-30-30 (0, 4 min), BFR-30-50 (4, 8 min), BFR-50-30 (8 min), BFR-50-50 (4, 8 min), BFR-70-30 (8 min), (p < 0.05); and power output: CON (8 min), BFR-30-30 (0, 4 min), BFR-30-50 (4 min), BFR-50-30 (8 min), BFR-50-50 (4, 8 min) (p < 0.05); vGRF: CON (8 min), BFR-30-30 (0, 4 min), BFR-30-50 (4, 8 min), BFR-50-30 (4 min), BFR-50-50 (4, 8 min) (p < 0.05); RFD: CON (8 min), BFR-30-30 (0, 4 min), BFR-30-50 (4 min), BFR-50-30 (4 min), BFR-50-50 (4 min) (p < 0.05). (5) Conclusions: low to moderate degrees of BFR procedures produced a similar PAP to traditional activation. Additionally, BFR-30-30, BFR-30-50, and BFR-50-50 were longer at PAP duration in comparison with CON.

Quadriceps strength symmetry predicts vertical ground reaction force symmetry during running in patients who have undergone ACL reconstruction

ObjectiveTo determine whether quadriceps strength symmetry can predict peak vertical ground reaction force (vGRF) running force symmetry in patients who have undergone ACL reconstruction (ACLR). We also sought to determine a cutoff for quadriceps strength symmetry to identify patients at risk for vGRF running asymmetry. DesignRetrospective cross-sectional. SettingClinical facility. MethodsBilateral quadriceps strength and vGRF data during running were obtained from 79 patients 26–30 weeks post ACLR. Linear regression was used to determine if quadriceps strength symmetry predicted peak vGRF running force symmetry. Classification and regression tree (CART) analysis was used to determine the cutoff value for quadriceps strength symmetry to identify patients at risk for vGRF running asymmetry. ResultsIncreased quadriceps strength symmetry predicted increased vGRF running symmetry (R2 = 0.20). CART analysis revealed that patients with quadriceps strength symmetry less than or equal to 88% were at highest risk for vGRF running asymmetry (R2 = 26%). ConclusionGreater quadriceps strength symmetry is predictive of greater vGRF running force symmetry in patients who have undergone ACLR. This finding highlights the need for clinicians to consider the degree of quadriceps strength symmetry before initiating a return to running program.

The effect of fatigue on running mechanics in older and younger runners

BackgroundThe presence of fatigue has been shown to modify running biomechanics. Throughout a run individuals become more fatigued, and the effectiveness of the musculoskeletal protective mechanism can diminish. Older adults are at an elevated risk for sustaining an overuse running related injury. This can be partially explained by changes in the musculoskeletal system and load attenuation. Research questionThe purpose was to compare post-fatigue running mechanics between older and younger runners. MethodsThirty runners (15 young, 15 older) between the ages of 18–65 participated in this study. All participants ran at least 15 miles/week. Running kinematics were captured using a 10-camera motion capture system while participants ran over a 10-m runway with force platforms collecting kinetic data under two conditions: C1: rested state at a controlled pace of 3.5 m/s ( ± 5%); C2: post-exertional protocol where pace was not controlled, rather it was monitored based on heartrate and RPE representative of somewhat-hard to hard intensity exercise. Prior to C2, participants underwent an exertional protocol that consisted of a maximal exercise test to induce fatigue and a required cool-down. A 2 (state of fatigue) x 2 (age) MANOVA was run to test for the effects of fatigue and age and their interactions. Results: No state of fatigue x age interaction was observed. A main effect of age for peak knee extension moment (Y > O; p = 0.01), maximum knee power (Y > O; p = 0.04), maximum hip power (O >Y; p = 0.04), and peak vertical ground reaction force (Y > O; p = 0.007). Regardless of age, participants exhibited decreased knee ROM (p = 0.007) and greater hip extension moment (p < 0.001) in C2 compared to C1. ConclusionWhile different in knee and hip mechanics overall, the subtle differences observed demonstrate that older runners exhibit comparable gait adaptions post-fatigue to younger volume-matched runners.

Jump landing among chronic ankle instability individuals who did or did not attend rehabilitation at the time of injury

ObjectivesThe purpose was to compare vertical ground reaction forces and sagittal-plane energy dissipation patterns of the lower extremity during a single-limb jump-stabilization task between individuals with chronic ankle instability who did or did not attend rehabilitation after their initial ankle sprain. DesignCross-sectional. SettingResearch laboratory. ParticipantsEight participants with chronic ankle instability who did and 12 participants who did not attend rehabilitation were enrolled. Main outcome measuresNormalized vertical ground reaction force data were used to calculate the average loading rate, time to peak force, and the peak force. Sagittal plane kinematics and joint moments at the ankle, knee, and hip, were used to calculate each joint's relative energy dissipation at 50, 100, 150, and 200 ms post-landing. ResultsParticipants who attended rehabilitation had a slower average loading rate (P = 0.025) and smaller peak vertical ground reaction force (P = 0.025). The average relative energy dissipation at the knee was higher in those who attended rehabilitation at the 100 ms (P = 0.041), 150 ms (P = 0.046), and 200 ms (P = 0.042) time intervals. ConclusionsAttending rehabilitation after an ankle sprain may have a beneficial effect on jump-stabilization outcomes among individuals with chronic ankle instability.

Reduction of risk factors for ACL Re-injuries using an innovative biofeedback approach: A phase I randomized clinical trial

ObjectivesDetermine the safety and initial efficacy of a novel biofeedback intervention to improve landing mechanics in patients following anterior cruciate ligament reconstruction (ACLR). MethodsForty patients post-ACLR (age: 16.9 ± 2.0 years) were randomly allocated to a biofeedback intervention or an attention control group. Patients in the biofeedback group completed 12 sessions over six-weeks that included bilateral unweighted squats with visual and tactile biofeedback. Patients in the control group completed a six-week educational program. Lower extremity mechanics were collected during a bilateral stop jump at baseline, six-weeks, and 12-weeks post-intervention. Linear mixed-effects models adjusted for sex and graft type determined the main effects of and interactions between group and time. ResultsNo group by time interaction existed for peak knee extension moment symmetry. A group by time interaction existed for peak vertical ground reaction force symmetry (p = 0.012), where patients in the biofeedback group had greater improvements in symmetry between baseline and post-intervention that were not maintained through the retention assessments. ConclusionThis novel biofeedback program did not reduce risk factors for second ACL injuries. Future work could develop and test multidisciplinary interventions for reducing second ACL injury risk factors. Clinicaltrials.gov identifier(NCT03273673)

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

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. To determine the association among landing biomechanics, knee pain, and kinesiophobia in athletes following anterior cruciate ligament reconstruction. A cross-sectional study. Clinical center of sports medicine. 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). Not applicable. 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. 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. 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.

Effect of progressive bridging exercise on weight-bearing during the extension phase of sit-to-stand, and on sit-to-stand ability in individuals with stroke: A randomised controlled trial

Objective To examine the effect of a progressive bridging exercise on force, time, and pressure during the extension phase of sit-to-stand, and on sit-to-stand ability in individuals with stroke. Design A single-blinded randomised controlled trial. Setting Hospital. Participants Forty-eight individuals with acute ischemic stroke, not at brainstem and cerebellum, randomly allocated to the intervention (n = 24) and control (n = 24) groups. Five participants dropped out during the 2-month follow-up, but they were in the intention-to-treat analysis. Interventions The intervention group undertook a 45-min conventional physiotherapy and a 30-min progressive bridging exercise. The control group received only the conventional exercise. Main measures Peak vertical ground reaction force, time to peak force, peak foot pressure, and regional peak foot pressure during the extension phase of sit-to-stand, and sitting-to-standing item of the Motor Assessment Scale were assessed before training, after 4-week training, and 2-month follow-up. Results The intervention group showed significantly (p < 0.001) less difference in peak vertical ground reaction force between feet during the extension phase of sit-to-stand than the control after 4-week training (mean ± standard deviation; intervention, 5.38 ± 3.99; control, 17.1 ± 10.3) and 2-month follow-up (intervention, 6.79 ± 3.84; control, 17.5 ± 9.89), and demonstrated significantly (p < 0.001) higher score in sit-to-stand than the control after training [mean (interquartile range); intervention, 5 (2-5); control, 2 (1-2)] and follow-up [intervention, 2 (2-5); control, 2 (1-2)]. Both groups demonstrated peak foot pressure on the medial and lateral heels, metatarsals, and hallux regions. Conclusion Progressive bridging exercise improved symmetrical weight bearing during the extension phase of sit-to-stand, consequently enhanced sit-to-stand ability in individuals with stroke.

Knee Movement Characteristics of Basketball Players in Landing Tasks Before Onset of Patellar Tendinopathy: A Prospective Study.

BackgroundPatellar tendinopathy is one of the most common injuries for basketball players. Jumping and landing movement patterns are potential risk factors for patellar tendinopathy.HypothesisMale college basketball players who developed patellar tendinopathy would demonstrate greater peak vertical ground reaction force and knee flexion angular velocity, and smaller knee flexion range of motion and knee flexion angles at initial contact compared to players who did not develop the injury when performing a stop-jump task within a year prior to the onset of the injury.Study DesignProspective study.MethodsFreshmen college basketball male players (n = 181) were recruited for three consecutive years and followed to the end of the third year of the study. Three-dimensional kinematic and kinetic data during a stop-jump task were collected for all participants at the beginning of each school year. Peak vertical ground reaction force, knee flexion angle at initial foot contact with the ground, range of motion for knee flexion and maximal knee flexion angular velocity during the landing phases of the stop-jump task were collected and calculated. Development of patellar tendinopathy was monitored in follow-up. Independent t-tests and Cohen's d effect sizes (ES) were used to compare movement patterns between injury and no injury groups for each school year.ResultsA total of 60 knees developed patellar tendinopathy. The injury groups had a significantly greater peak vertical ground reaction force in freshmen and junior years (P = 0.020, ES = 0.13; P = 0.046, ES = 0.17), smaller knee flexion ROM in freshmen year (P = 0.002, ES = 0.10), and greater maximum knee flexion angular velocity in freshmen and junior year (P = 0.012, ES = 0.10; P = 0.001, ES = 0.35) during the horizontal landing phase before the takeoff of the jump compared to the no injury groups. The injury groups also had a significantly smaller knee flexion angle at initial contact during vertical landing phase after the takeoff of the jump in freshmen and junior years (P = 0.001, ES = 0.36; P = 0.001; ES = 0.37) during vertical landing phase.ConclusionPeak vertical ground reaction force, knee flexion angle at initial foot contact, knee flexion range of motion, and maximum knee flexion angular velocity are associated with patellar tendinopathy among male college basketball players in different school years.