The effect of external focus versus internal focus instruction on jump-landing biomechanics in healthy females.

CONTEXT: Different forms of instruction have contributed to favorable results in injury interventions. External focus (EF) instruction may be superior to internal focus (IF) instruction. OBJECTIVE: To investigate the difference in landing biomechanics between participants who received EF versus IF instruction and a control. A secondary aim was to evaluate participant perceptions of focus of attention. DESIGN: Randomized controlled trial. SETTING: Laboratory. PATIENTS OR OTHER PARTICIPANTS: Forty-one healthy females. EF: N=14; 23.0±2.9yrs; 1.69±0.07m; 64.0±6.8kg; IF: N=15; 22.9±3.2yrs;1.66±0.08m;66.2±12.4kg; Control: N=12; ±2.9yrs; 1.67±0.11m; 74.3±15.1kg. MAIN OUTCOME MEASURES: Participants scoring ≥ five on the LESS and were allocated into EF, IF or control groups. Knee and hip flexion and abduction were collected pre- and post-intervention during five drop vertical jumps. For the intervention, each group was provided separate instructions. In-between the intervention jumps, participants answered: "What strategy were you focusing on when completing the previous jump-landing trials?". Post-intervention minus pre-intervention change scores were calculated and separate 1-way ANOVAs assessed differences in the dependent variables. RESULTS: EF had a greater change in hip and knee flexion angles versus control. There was no significant difference between EF and IF for any variables. There were no significant differences in frontal plane variables. In the EF group, 71.4% were "aligned". In the IF group, 80% of the were "aligned". In the CONT group, 50% were "aligned". CONCLUSIONS: EF instruction may not produce immediate changes in movement compared to IF instruction. Hip and knee flexion were greater in the EF group compared to the control group but was not better than the IF group. Clinicians should provide instruction to patients, but the mode of instruction may not be as critical to see positive biomechanical changes. Patients may not always focus on the instruction being given, therefore the relationship between instruction and patient experience should be further explored.

Case report: Self-performed orthopedic exams in telehealth treatment of a youth athlete with acute rotator cuff strain.

Background: Sports-related rotator cuff muscle injury is one of the most prevalent pathologies affecting overhead sports athletes. Since the COVID-19 pandemic and its subsequent stay-at-home protocols, physical therapy has transited into a new realm of telehealth. Current evidence regarding examining and managing RTC strain in telehealth physical therapy is minimal. Case presentation: A self-referred 14-year-old female Chinese semi-professional tennis player presented with an acute right RTC strain. The mechanism of injury involved forehand strokes with left trunk rotation. No ligamentous or labral damage was observed on Magnetic Resonance Imagining. The individualized care plan included virtual partner-assisted assessment, online instructions on therapeutic exercises, and education with psychosocial considerations. Outcome and follow-up: After a 6-week intervention, the patient demonstrated complete shoulder range of motion, full muscle strength, complete return-to-practice, 0% Quick DASH disability index, and 6/68 on the Tampa Scale for kinesiophobia. Discussion: This case report demonstrated that telehealth is an accessible and cost-effective option for youth tennis athletes with RTC strain. This unique case showed a detailed roadmap from examination to discharge of this plan of care. There are also barriers including test and measure validity, and communication difficulties to be considered. Despite the challenges, this case was a good example of telehealth being an effective, repeatable, and cost-efficient option for patients with poor healthcare access.

The injury risk profile of an Army Reserve Officers' Training Corps population: A preliminary descriptive study.

OBJECTIVES: Army Reserve Officers' Training Corps (ROTC) prepares cadets for military service where lower extremity injuries can occur. The Landing Error Scoring System (LESS), Functional Movement Screen (FMS) and Y-Balance (YBAL) have not been used to evaluate injury risk in the ROTC. Higher physical fitness lowers injury risk in basic training recruits, it is unknown if previous high school sport participation affects injury risk in the ROTC. The purpose of this study was to evaluation the LESS, FMS, YBAL and high school sport participation in the ROTC. DESIGN: Descriptive study. SETTING: University. PARTICIPANTS: 78 ROTC (49 males, 29 females; 19.7 ± 2.3yrs; 1.71 ± 10.1 m; 62.5 ± 21.2 kg). MAIN OUTCOME MEASURES: LESS, FMS, YBAL and sports participation were collected and scores were calculated. Means, standard deviation and range were reported for each test. Distribution of scores within injury risk categories were evaluated. Sport participation frequency was reported. RESULTS: The mean LESS and FMS scores were 7.1 ± 2.1 and 14.6 ± 2.1, respectively. The average YBAL composite score was 90.2% ± 12.0. 68% were poor on the LESS. 46.1% were high risk on the FMS. 69.2% were high risk on the YBAL composite. Seventy-seven percent reported at least one year of participation in high school sports. CONCLUSIONS: ROTC population demonstrated poor jump landing mechanics and were high risk on the YBAL composite.

Females Decrease Vertical Ground Reaction Forces Following 4-Week Jump-Landing Feedback Intervention Without Negative Affect on Vertical Jump Performance.

CONTEXT: High vertical ground reaction force (vGRF) when initiating ground contact during jump landing is one biomechanical factor that may increase risk of anterior cruciate ligament injury. Intervention programs have been developed to decrease vGRF to reduce injury risk, yet generating high forces is still critical for performing dynamic activities such as a vertical jump task. OBJECTIVE: To evaluate if a jump-landing feedback intervention, cueing a decrease in vGRF, would impair vertical jump performance in a separate task (Vertmax). DESIGN: Randomized controlled trial. Patients (or Other Participants): Forty-eight recreationally active females (feedback: n = 31; 19.63 [1.54] y, 1.6 [0.08] cm, 58.13 [7.84] kg and control: n = 15; 19.6 [1.68] y, 1.64 [0.05] cm, 60.11 [8.36] kg) participated in this study. INTERVENTION: Peak vGRF during a jump landing and Vertmax were recorded at baseline and 4 weeks post. The feedback group participated in 12 sessions over the 4-week period consisting of feedback provided for 6 sets of 6 jumps off a 30-cm box. The control group was instructed to return to the lab 28 days following the baseline measurements. MAIN OUTCOME MEASURES: Change scores (postbaseline) were calculated for peak vGRF and Vertmax. Group differences were evaluated for peak vGRF and Vertmax using a Mann-Whitney U test (P < .05). RESULTS: There were no significant differences between groups at baseline (P > .05). The feedback group (-0.5 [0.3] N/kg) demonstrated a greater decrease in vGRF compared with the control group (0.01 [0.3] N/kg) (t(46) = -5.52, P < .001). There were no significant differences in change in Vertmax between groups (feedback = 0.9 [2.2] cm, control = 0.06 [2.1] cm; t(46) = 0.46, P = .64). CONCLUSIONS: While the feedback intervention was effective in decreasing vGRF when landing from a jump, these participants did not demonstrate changes in vertical jump performance when assessed during a different task. Practitioners should consider implementing feedback intervention programs to reduce peak vGRF, without worry of diminished vertical jump performance.

Evaluation of Agreement Between Participant and Expert on Jump-Landing Characteristics During a 4-Week Intervention.

CONTEXT: Feedback is an important factor in interventions designed to reduce anterior cruciate ligament injury risk. Self-analysis feedback requires participants to self-critique their jump-landing mechanics; however, it is unknown if individuals can effectively self-analyze their own biomechanics and if this self-analysis agrees with observed biomechanical changes by an expert. OBJECTIVE: To determine agreement between an expert and participants on biomechanical errors committed during 3 of 12 sessions, which were part of an intervention to change jump-landing biomechanics in healthy females. DESIGN: Descriptive analysis. SETTING: Research laboratory. PATIENTS OR OTHER PARTICIPANTS: Healthy recreationally active females with no history of lower-extremity fracture or surgery. INTERVENTIONS: Participants completed a 4-week, 12-session feedback intervention. Each intervention session lasted approximately 15 minutes and included asking participants to perform 6 sets of 6 jumps off a 30-cm-high box placed 50% of their height away from the target landing area. Participants performed self-analysis feedback and received expert feedback on 7 different jump-landing criteria following each set of jumps. MAIN OUTCOME MEASURES: Data were coded, and agreement between the expert and the participant was assessed using Cohen's unweighted kappa for sessions 1, 6, and 12. RESULTS: There was agreement between the expert and participants for 0/7 criteria for session 1, 3/7 criteria for session 6, and 4/7 criteria for session 12. CONCLUSIONS: Participants demonstrated some agreement with the expert when evaluating their jump-landing biomechanics. Self-analysis feedback may not replace what an expert can provide; both types of feedback may be better used in conjunction to produce significant biomechanical changes. Changes made by the participant may not translate into biomechanical changes during a real-life game or practice situation. Future research should continue to investigate effective interventions to reduce injury risk.

Jump-landing biomechanics following a 4-week real-time feedback intervention and retention.

BACKGROUND: Poor neuromuscular control can increase the risk of anterior cruciate ligament (ACL) injury. Landing with decreased knee and hip flexion may increase the risk of lower extremity injury. Feedback interventions have demonstrated changes in jump-landing biomechanics. Traditional feedback (TF), provided after task completion, includes critical factors to focus on during jump-landing. Real-time feedback (RTF), provided while completing the task, may be superior for improving jump-landing biomechanics. This investigation evaluated the effect of RTF+TF compared to TF and a control group in changing lower extremity jump-landing biomechanics following a 4-week feedback intervention and a 1-week no feedback retention. METHODS: Participants completed 12 feedback sessions over 4 weeks. At each session, participants performed 6 sets of 6 jumps off a 30 cm box. Participants were provided TF or RTF+TF following each set of jumps. Participants were tested at baseline, immediately following the 4-week intervention and following a 1-week retention. The control group was tested at two time points 4 weeks apart. FINDINGS: Acquisition analysis: RTF+TF and TF groups demonstrated greater change in peak hip flexion angles and peak knee flexion angles compared to the control group following the intervention. TF and RTF+TF groups demonstrated a greater decrease in peak vertical ground reaction force compared to the control group. No significant differences were observed between groups in the retention analysis. INTERPRETATION: This study provides evidence of acquisition of biomechanical changes following a 4-week feedback intervention. Future research should further investigate the retention of biomechanical changes, the optimal length of feedback interventions and transfer of learned biomechanics to similar athletic tasks.

Neural Excitability Alterations After Anterior Cruciate Ligament Reconstruction.

CONTEXT: Neuromuscular dysfunction is common after anterior cruciate ligament reconstruction (ACL-R). However, little is known about quadriceps spinal-reflex and descending corticomotor excitability after ACL-R. Understanding the effects of ACL-R on spinal-reflex and corticomotor excitability will help elucidate the origins of neuromuscular dysfunction. OBJECTIVE: To determine whether spinal-reflex excitability and corticomotor excitability differed between the injured and uninjured limbs of patients with unilateral ACL-R and between these limbs and the matched limbs of healthy participants. DESIGN: Case-control study. SETTING: Laboratory. PATIENTS OR OTHER PARTICIPANTS: A total of 28 patients with unilateral ACL-R (9 men, 19 women; age = 21.28 ± 3.79 years, height = 170.95 ± 10.04 cm, mass = 73.18 ± 18.02 kg, time after surgery = 48.10 ± 36.17 months) and 29 participants serving as healthy controls (9 men, 20 women; age = 21.55 ± 2.70 years, height = 170.59 ± 8.93 cm, mass = 71.89 ± 12.70 kg) volunteered. MAIN OUTCOME MEASURE(S): Active motor thresholds (AMTs) were collected from the vastus medialis (VM) using transcranial magnetic stimulation. We evaluated VM spinal reflexes using the Hoffmann reflex normalized to maximal muscle responses (H : M ratio). Voluntary quadriceps activation was measured with the superimposed-burst technique and calculated using the central activation ratio (CAR). We also evaluated whether ACL-R patients with high or low voluntary activation had different outcomes. RESULTS: The AMT was higher in the injured than in the uninjured limb in the ACL-R group (t27 = 3.32, P = .003) and in the matched limb of the control group (t55 = 2.05, P = .04). The H : M ratio was bilaterally higher in the ACL-R than the control group (F1,55 = 5.17, P = .03). The quadriceps CAR was bilaterally lower in the ACL-R compared with the control group (F1,55 = 10.5, P = .002). The ACL-R group with low voluntary activation (CAR < 0.95) had higher AMT than the control group (P = .02), whereas the ACL-R group with high voluntary activation (CAR ≥ 0.95) demonstrated higher H : M ratios than the control group (P = .05). CONCLUSIONS: The higher VM AMT in the injured limbs of ACL-R patients suggested that corticomotor deficits were present after surgery. Higher bilateral H : M ratios in ACL-R patients may be a strategy to reflexively increase excitability to maintain voluntary activation.

Immediate effects of real-time feedback on jump-landing kinematics.

STUDY DESIGN: Randomized controlled trial. OBJECTIVE: To determine if the addition of real-time feedback (RTF) to postresponse feedback (PRF) improves jump-landing kinematics compared to PRF alone and a no-feedback control group. BACKGROUND: Injury-prevention programs to reduce risk of anterior cruciate ligament injury have shown promising results in altering jump-landing biomechanics. Real-time feedback provided during the task may allow participants to more easily understand and execute new movement strategies compared to PRF provided after the task is completed. METHODS: Thirty-six healthy females were randomized to 1 of 3 groups: RTF plus PRF, PRF, or control. Sagittal plane moments and angles at the knee and hip, frontal plane angles at the knee, and vertical ground reaction forces during a jump-landing task were quantified at baseline and postintervention. The RTF plus PRF and PRF groups received a PowerPoint presentation containing the goals of correct landing technique. In addition to the PowerPoint presentation, the RTF plus PRF group was provided real-time visualization of their frontal plane knee angle. Participants in the control group performed the jump-landing task without feedback. RESULTS: Posttraining, the RTF plus PRF and PRF groups demonstrated similar improvements in hip and knee flexion and decreased vertical ground reaction forces compared to the control group. There were no changes in frontal plane knee kinematics between groups posttraining. CONCLUSION: The addition of RTF to PRF did not result in significant changes in jump-landing kinematics compared to PRF alone. LEVEL OF EVIDENCE: Prevention, level 5.

Contributions of neural excitability and voluntary activation to quadriceps muscle strength following anterior cruciate ligament reconstruction.

BACKGROUND: Persistent quadriceps weakness is common following anterior cruciate ligament reconstruction (ACLr). Alterations in spinal-reflexive excitability, corticospinal excitability and voluntary activation have been hypothesized as underlying mechanisms contributing to quadriceps weakness. The aim of this study was to evaluate the predictive capabilities of spinal-reflexive excitability, corticospinal excitability and voluntary activation on quadriceps strength in healthy and ACLr participants. METHODS: Quadriceps strength was measured using maximal voluntary isometric contractions (MVIC). Voluntary activation was quantified via the central activation ratio (CAR). Corticospinal and spinal-reflexive excitability were measured using active motor thresholds (AMT) and Hoffmann reflexes normalized to maximal muscle responses (H:M), respectively. ACLr individuals were also split into high and low strength subsets based on MVIC. RESULTS: CAR was the only significant predictor in the healthy group. In the ACLr group, CAR and H:M significantly predicted 47% of the variance in MVIC. ACLr individuals in the high strength subset demonstrated significantly higher CAR and H:M than those in the low strength subset. CONCLUSION: Increased quadriceps voluntary activation, spinal-reflexive excitability and corticospinal excitability relates to increased quadriceps strength in participants following ACLr. CLINICAL RELEVANCE: Rehabilitation strategies used to target neural alterations may be beneficial for the restoration of muscle strength following ACLr.

Different modes of feedback and peak vertical ground reaction force during jump landing: a systematic review.

CONTEXT: Excessive ground reaction force when landing from a jump may result in lower extremity injuries. It is important to better understand how feedback can influence ground reaction force (GRF) and potentially reduce injury risk. OBJECTIVE: To determine the effect of expert-provided (EP), self-analysis (SA), and combination EP and SA (combo) feedback on reducing peak vertical GRF during a jump-landing task. DATA SOURCES: We searched the Web of Science database on July 1, 2011; using the search terms ground reaction force, landing biomechanics, and feedback elicited 731 initial hits. STUDY SELECTION: Of the 731 initial hits, our final analysis included 7 studies that incorporated 32 separate data comparisons. DATA EXTRACTION: Standardized effect sizes and 95% confidence intervals (CIs) were calculated between pretest and posttest scores for each feedback condition. DATA SYNTHESIS: We found a homogeneous beneficial effect for combo feedback, indicating a reduction in GRF with no CIs crossing zero. We also found a homogeneous beneficial effect for EP feedback, but the CIs from 4 of the 10 data comparisons crossed zero. The SA feedback showed strong, definitive effects when the intervention included a videotape SA, with no CIs crossing zero. CONCLUSIONS: Of the 7 studies reviewed, combo feedback seemed to produce the greatest decrease in peak vertical GRF during a jump-landing task.

Relationship between gluteal muscle strength, corticospinal excitability, and jump-landing biomechanics in healthy women.

CONTEXT: Components of gluteal neuromuscular function, such as strength and corticospinal excitability, could potentially influence alterations in lower extremity biomechanics during jump landing. OBJECTIVE: To determine the relationship between gluteal muscle strength, gluteal corticospinal excitability, and jump-landing biomechanics in healthy women. SETTING: University laboratory. DESIGN: Descriptive laboratory study. PARTICIPANTS: 37 healthy women (21.08 ± 2.15 y, 164.8 ± 5.9 cm, 65.4 ± 12.0 kg). INTERVENTIONS: Bilateral gluteal strength was assessed through maximal voluntary isometric contractions (MVIC) using an isokinetic dynamometer. Strength was tested in the open chain in prone and side-lying positions for the gluteus maximus and gluteus medius muscles, respectively. Transcranial magnetic stimulation was used to elicit measures of corticospinal excitability. Participants then performed 3 trials of jump landing from a 30-cm box to a distance of 50% of their height, with an immediate rebound to a maximal vertical jump. Each jump-landing trial was video recorded (2-D) and later scored for errors. MAIN OUTCOME MEASURES: MVICs normalized to body mass were used to assess strength in the gluteal muscles of the dominant and nondominant limbs. Corticospinal excitability was assessed by means of active motor threshold (AMT) and motor-evoked potentials (MEP) elicited at 120% of AMT. The Landing Error Scoring System (LESS) was used to evaluate jump-landing biomechanics. RESULTS: A moderate, positive correlation was found between dominant gluteus maximus MEP and LESS scores (r = .562, P = .029). No other significant correlations were observed for MVIC, AMT, or MEP for the gluteus maximus and gluteus medius, regardless of limb. CONCLUSIONS: The findings suggest a moderate relationship between dominant gluteus maximus corticospinal excitability and a clinical measure of jump-landing biomechanics. Further research is required to substantiate the findings and expand our understanding of the central nervous system's role in athletic movement.

Quadriceps strength and corticospinal excitability as predictors of disability after anterior cruciate ligament reconstruction.

BACKGROUND: Disability is common in a proportion of patients after anterior cruciate ligament reconstruction (ACL-R). Neuromuscular quadriceps deficits are a hallmark impairment after ACL-R, yet the link between muscle function and disability is not understood. PURPOSES: To evaluate the ability of quadriceps strength and cortical excitability to predict self-reported disability in patients with ACL-R. METHODS: Fifteen participants with a history of ACL-R (11 female, 4 male; 172 ± 9.8 cm, 70.4 ± 17.5 kg, 54.4 ± 40.9 mo postsurgery) were included in this study. Corticospinal excitability was assessed using active motor thresholds (AMT), while strength was assessed with maximal voluntary isometric contractions (MVIC). Both voluntary strength and corticospinal excitability were used to predict disability measured with the International Knee Documentation Committee Index (IKDC). RESULTS: The overall multiple-regression model significantly predicted 66% of the variance in self-reported disability as measured by the IKDC index (R2 = .66, P = .01). Initial imputation of MVIC into the model accounted for 61% (R2 = .61, P = .01) of the variance in IKDC. The subsequent addition of AMT into the model accounted for an insignificant increase of 5% (Δ R2 = .05, P = .19) in the prediction capability of the model. CONCLUSIONS: Quadriceps voluntary strength and cortical excitability predicted two-thirds of the variance in disability of patients with ACL-R, with strength accounting for virtually all of the predictive capability of the model.