Stance Time and Impact Loading Rates are Significant Predictors of Critical Speed During a 3-Minute All-Out Running Test.

The addition of wearable technology during a 3-minute all-out overground running test (3MAOT) could provide additional insights to guide training and coaching strategies. The purpose of this study was to explore the relationships between critical speed (CS) and biomechanical parameters (cadence, stride length, vertical oscillation, stance time, form power, leg spring stiffness, and impact loading rate), and changes in biomechanical parameters throughout the 3MAOT. Sixty-three (male, n=37, female, n=26) recreationally active college-aged (23.4±3.9 years) subjects completed a 3MAOT while wearing a Stryd foot-pod. The correlations between CS and biomechanical parameters were evaluated using Pearson coefficients. Stepwise multiple linear regressions were used to test if biomechanical parameters could predict CS. Stance time and impact loading rate explained 69% and 63% of the variance in CS, respectively (R2=0.69, p<0.05; R2=0.63, p<0.05). Step-wise multiple linear regression analysis indicated that vertical oscillation, stance time, form power, leg spring stiffness, and impact loading rate explained 90% of the variance in CS (R2=0.90, p<0.05). Throughout the 3MAOT, changes in cadence (-29%), stride length (57%), vertical oscillation (-8%), stance time (82%), form power (-5%), leg spring stiffness (-24%), and impact loading rate (-48%) were observed. Interventions such as auditory cueing or training designed to improve CS should focus on maintaining large impact loading rates and short stance times, and efforts should be made to enhance an athlete's ability to maintain cadence, leg spring stiffness, vertical oscillation, and form power throughout the 3MAOT.

Running Alterations Pre- and Postarthroscopy for Femoroacetabular Impingement Syndrome and Labral Tears.

ABSTRACT: Freemyer, B, Beeler, D, Crawford, S, Durkin, R, and Stickley, C. Running alterations pre- and postarthroscopy for femoroacetabular impingement syndrome and labral tears. J Strength Cond Res 38(3): 501-509, 2024-Running is essential to sports participation and activity over the lifespan; however, running biomechanics are not fully described in patients with femoroacetabular impingement (FAIS). The purpose was to compare FAIS patient report outcome surveys (PRO) and running biomechanics preoperatively and 6 months postoperatively with controls. Nineteen subjects (FAIS, n = 10 and age-matched controls, n = 9) were included. The UCLA, Hip Outcome Score activity of daily living (HOS ADL ) and sports subscale (HOS SS ), and 3-D running biomechanics were evaluated. Statistical parametric mapping was conducted on biomechanics data. Statistical significance was set at p ≤ 0.05. Femoroacetabular impingement had similar UCLA activity scores compared with controls by 6 months (FAIS: 8.4 ± 1.7, CON: 8.6 ± 2.0, p = 0.80), despite lower HOS ADL (FAIS-Six: 89.3 ± 6.3, CON: 100 ± 0, p = 0.04) and HOS SS (FAIS-Six: 82.6 ± 18.5, CON: 100 ± 0, p = 0.05). The FAIS group had lower knee adduction moments (KAM) around 22-27% of stance ( p = 0.05) and lower sagittal plane ankle power generation during the final 5% of stance compared with the controls ( p = 0.04) preoperatively. The FAIS also had lower vertical ground reaction forces the first 2% of stance ( p = 0.05) and lower KAM from 20 to 30% stance ( p = 0.03) at the postoperative time vs. controls. Femoroacetabular impingement had higher hip external rotation angles the first 5% stance ( p = 0.05) and the last 20% of stance ( p = 0.01) vs. controls. This is the first study to describe FAIS running pre- and postoperatively. Despite higher activity and health 6 months postarthroscopy, the patients with FAIS had altered running biomechanics. Clinicians should consider these findings when creating rehabilitation protocols and during running progressions across the postoperative care of patients with FAIS.

Allometric Scaling Hip Joint Moments Optimally Reduces Anthropometric Differences in Males and Females.

Running biomechanics are scaled to reduce the effects of anthropometric differences between participants. Ratio scaling has limitations, and allometric scaling has not been applied to hip joint moments. The aim was to compare raw, ratio and allometrically scaled hip joint moments. Sagittal and frontal plane moments of 84 males and 47 females were calculated while running at 4.0 m/s. Raw data were ratio scaled by body mass (BM), height (HT), leg length (LL) and BM multiplied by HT (BM*HT) and LL (BM*LL). Log-linear (for BM, HT and LL individually) or log-multilinear regression (BM*HT and BM*LL) exponents were calculated. Correlations and r2 values assessed the effectiveness of each scaling method. Eighty-five per cent of raw moments were positively correlated to the anthropometrics with r2 values of 10-19%. In ratio scaling, 26-43% were significantly correlated to the moments and a majority were negative, indicating overcorrections. The most effective scaling procedure was the allometric BM*HT, as the mean shared variance between the hip moment and anthropometrics was 0.1-0.2% across all sexes and moments and none had significant correlations. Allometric scaling of hip joint moments during running are advised if the goal is to remove the underlying effects of anthropometrics across male and female participants.

Favorable outcomes of posterior cruciate-stabilized inserts over ultracongruent inserts in total knee arthroplasty.

OBJECTIVE: Posterior cruciate-stabilized (PS) and ultracongruent (UC) inserts are used during total knee arthroplasty (TKA), but superiority in gaining postoperative knee flexion and functionality remains contested. Therefore, this study compared postoperative outcomes between PS and UC inserts. METHODS: A retrospective review evaluated unilateral or bilateral TKAs with PS or UC inserts from August 2011 to March 2020. Nonparametric statistics were performed to evaluate differences in patient demographics, pre- and postknee flexion and Knee Society Knee (KSS-K) and Function Score (KSS-F). Univariate and multivariable regressions were performed to evaluate the influence on postoperative knee flexion ≥ 120°, presented as odds ratios (OR) and 95% confidence intervals (CI). RESULTS: Patient demographics were not significantly different between the 577 PS and 399 UC knees evaluated. Postoperatively, a larger proportion of UC knees demonstrated knee flexion < 120° (36.0% vs. 18.6%, p < 0.001) and lower KSS-K (91.0 ± 8.7 vs. 91.6 ± 10.3, p < 0.001) and KSS-F (76.8 ± 21.6 vs. 79.9 ± 21.6, p = 0.007) than the PS group. The PS group had greater improvement in flexion angle (4.9° ± 14.9° vs. 1.0° ± 15.6°, p < 0.001) and KSS-F (27.3 ± 23.3 vs. 23.1 ± 25.3, p = 0.007) as compared to that of UC patients. Patients with preoperative flexion < 120° (OR 2.787, CI 2.066-3.761; p < 0.001), higher body mass index (OR 1.033, CI 1.006-1.061; p = 0.017) and UC insert (OR 2.461, CI 1.832-3.307; p < 0.001) were less likely to achieve flexion ≥ 120°. CONCLUSION: Favorable clinical and functional outcomes were noted in the PS group as compared to UC inserts in TKA. The greater improvement in overall knee flexion may suggest the PS insert may be especially appropriate for patients with lower preoperative range of motion. LEVEL OF EVIDENCE: III, retrospective comparative study.

Preoperative and Postoperative Walking Gait in Women With Acetabular Labral Tears and Femoroacetabular Impingement Syndrome.

CONTEXT: Symptomatic femoroacetabular impingement syndrome (FAIS) is a painful condition that leads to decreased function. How walking gait changes over time within the first year after surgery for FAIS and how these changes present in women are currently unknown. OBJECTIVE: To determine biomechanical gait differences between women with FAIS or labral tears and control individuals preoperatively and at 3 and 6 months postoperatively. DESIGN: Case-control study. SETTING: Laboratory. PATIENTS OR OTHER PARTICIPANTS: A total of 18 female participants comprising 9 women in the FAIS group (age = 31.44 ± 7.47 years, height = 1.73 ± 0.08 m, mass = 73.61 ± 14.44 kg) and 9 women in the control group (age = 31.44 ± 6.65 years, height = 1.69 ± 0.06 m, mass = 60.93 ± 5.58 kg). MAIN OUTCOME MEASURE(S): Between-groups comparisons of the Hip Outcome Score Activities of Daily Living subscale (HOSADL) and gait biomechanics were conducted preoperatively and at the 3- and 6-month postoperative sessions. Statistical parametric mapping was performed on normalized time-series data. RESULTS: Preoperatively, the FAIS group had poor HOSADL scores (FAIS group = 64.1 ± 15.4 versus control group = 100.0 ± 0, P < .001), walked 15% slower, and exhibited several gait differences compared with the control group. Three months postoperatively, the FAIS group displayed greater vertical ground reaction force (P = .01), ankle-dorsiflexion angle (P = .02), and external dorsiflexion moment (P = .01) in midstance, as well as a greater knee-flexion angle through the second half of stance (P < .001). The FAIS group also demonstrated less hip-extension angle (P = .02) and hip-abduction angle (P = .01) through the second half of stance, which transitioned into less hip extension (P = .040) and hip abduction (P = .03) during the subsequent swing phase. The FAIS group improved their HOSADL to 87.6 ± 7.6 by 6 months postoperatively and had a greater dorsiflexion moment (P = .003) and ankle external rotation during stance (P = .03). In addition, the FAIS group showed a greater external hip external-rotation moment in late stance (P < .001). CONCLUSIONS: The biomechanical differences between groups were most evident at 3 months postoperatively, suggesting that women with FAIS had more postoperative gait compensations in the short term after surgery. By 6 months postoperatively, patient-reported outcomes had markedly improved, and the FAIS group displayed few gait differences compared with the control group.

Weight-Bearing Versus Traditional Strength Assessments of the Hip Musculature.

CONTEXT: Traditional nonweight-bearing (NWB) hip-strength assessments may not directly translate to functional strength during weight-bearing (WB) activity. How NWB assessments of hip muscle strength compare with WB assessments in various positions is currently unknown. OBJECTIVE: To determine the magnitude of the differences and correlations between NWB hip strength and WB functional strength during the squatting and lunge (LNG) positions in female athletes. DESIGN: Crossover design. SETTING: Laboratory. PATIENTS OR OTHER PARTICIPANTS: Female athletes (N = 51, age = 16.2 ± 3.5 years, height = 161.5 ± 8.3 cm, mass = 58.3 ± 11.6 kg). INTERVENTION(S): Isometric resistance (N/kg) was determined for the dominant and nondominant limbs via WB assessments (squat-bilateral [legs tested simultaneously], squat-unilateral, and lunge positions) and NWB assessments (hip external rotation [HER], hip extension [HEXT], and hip abduction [HAB]). MAIN OUTCOME MEASURE(S): To compare differences between positions (P ≤ .05), we used effect sizes (d) and matched-pairs t tests, and we calculated Pearson r and R2 values. RESULTS: During the squat-bilateral on the dominant limb, females produced the most hip torque (6.13 ± 1.12 N/kg). The magnitudes of differences were very large compared with HER (3.96 ± 0.83, d = 2.2), HEXT (3.22 ± 0.69, d = 3.2), and HAB (3.80 ± 1.01, d = 2.2; all P values ≤ .01), and positions were moderately correlated (r = 0.347-0.419, R2 = 0.12-0.18). The lunge position produced the least amount of torque in the dominant limb (2.44 ± 0.48 N/kg) compared with HER (d = -2.3), HEXT (d = -1.3), and HAB (d = -1.7; all P values ≤ .001), and correlations were small to moderate (r = 0.236-0.310, R2 = 0.06-0.10). CONCLUSIONS: Strength in WB positions was different than strength evaluated using traditional NWB assessments in female athletes. Weight-bearing tests may provide clinicians with additional information regarding strength and function.

Musculoskeletal Injury in Reserve Officers' Training Corps: A Report From the Athletic Training Practice-Based Research Network.

BACKGROUND: Reserve Officers' Training Corps (ROTC) cadets must meet the same physical standards as active duty military servicemembers and undergo organized physical training (PT). ROTC participation, like all physical activity, can result in training-related musculoskeletal injury (MSKI), and of course, cadets could sustain MSKI outside of ROTC. However, MSKI incidence in ROTC programs is largely unknown. PURPOSE: To describe patient and injury demographics of MSKI in 5 universities' Army ROTC programs. STUDY DESIGN: Descriptive epidemiology study. METHODS: A retrospective chart review of electronic medical records was performed using the Athletic Training Practice-Based Research Network (AT-PBRN). Athletic trainers at 5 clinical practice sites within the AT-PBRN documented injury assessments via a web-based electronic medical record system. Medical records during the 2017-2018 and 2018-2019 academic years were used for analysis. Summary statistics were calculated for age, sex, height, body mass, military science year, training ability group, mechanism of injury, activity type associated with injury, anatomic location of injury, participation status, injury severity, and diagnosis. RESULTS: A total of 364 unique injuries were documented. Cadets in the most advanced fitness group (Alpha; n = 148/364) and in their third year of training (n = 97/364) presented with the most injuries. Injuries most commonly occurred during PT (n = 165/364). Insidious onset (n = 146/364) and noncontact (n = 115/364) mechanisms of injury were prevalent. The most frequent anatomic location of injury was the knee (n = 71/364) followed by the ankle (n = 57/364). General sprain/strain was the most frequent International Classification of Diseases, Ninth Revision, Clinical Modification diagnosis code reported (n = 34/364). CONCLUSION: The knee was the most frequent location of MSKI in ROTC participants, and most MSKIs had insidious onset. Cadets with higher injury frequency were high achieving (Alpha) and in a critical time point in ROTC (military science year 3). The majority of MSKIs can be attributed to ROTC training, with PT being the most frequent activity associated with injury. Civilian health care providers, from whom ROTC cadets will most likely seek medical attention, need to be aware of ROTC physical demands as well as the characteristics of training-related injuries.

Fatigue-Induced Hip-Abductor Weakness and Changes in Biomechanical Risk Factors for Running-Related Injuries.

CONTEXT: Despite overlap between hip-abductor (HABD) weakness and fatigue-induced changes in running, the interaction of these theorized contributors to running injuries has been underevaluated. OBJECTIVE: To assess the effects of a fatiguing run on HABD torque and evaluate the correlation between HABD torque and previously identified running-related injury pathomechanics while participants were rested or fatigued. DESIGN: Crossover study. SETTING: Laboratory. PATIENTS OR OTHER PARTICIPANTS: A total of 38 healthy, physically active males (age = 21.61 ± 4.02 years, height = 1.78 ± 0.08 m, body mass = 76.00 ± 12.39 kg). INTERVENTION(S): Data collection consisted of rested-state collection, a fatiguing treadmill-run protocol, and fatigued-state collection. For the HABD measures, side-lying handheld-dynamometer isometric tests were performed and converted to torque using femur length. For the gait analysis, kinematic (240 Hz) and kinetic (960 Hz) running (4.0 m/s) data were collected for 3 trials. The fatigue protocol involved a graded exercise test and 80% o2max run to exhaustion. Immediately after the run, fatigued-state measures were obtained. MAIN OUTCOME MEASURE(S): Variables of interest were HABD torque and peak angles, velocities, and moments for hip and knee adduction and internal rotation. Differences between conditions were compared using paired t tests. Pearson correlation coefficients were calculated to evaluate relationships between HABD torque and biomechanical variables. RESULTS: Fatigue decreased HABD torque and increased hip-adduction angle, knee-adduction velocity, and hip and knee internal-rotation velocities and moments (all P values < .05). In the rested state, HABD torque was correlated with hip-adduction velocity (r = -0.322, P = .049). In the fatigued state, HABD torque was correlated with hip-adduction velocity (r = -0.393, P = .015), hip internal-rotation velocity (r = -0.410, P = .01), and knee-adduction angle (r = 0.385, P = .017) and velocity (r = -0.378, P = .019). CONCLUSIONS: Changes in joint velocities due to fatigue and correlations between HABD torque and hip- and knee-joint velocities highlight the need to consider not only the quantity of HABD strength but also the rate of eccentric control of HABDs.

The effect of Kinesio-tape® on pain and vertical jump performance in active individuals with patellar tendinopathy.

BACKGROUND: Patellar tendinopathy is a common inflammatory condition in athletes who undergo large volumes of running and jumping. Kinesio-tape® (KT) is proposed to provide pain relief; however, its effect has not been examined on patellar tendinopathy. OBJECTIVE: To examine the effects of KT on pain modulation for active individuals with patellar tendinopathy during functional activities. METHODS: Thirteen symptomatic knees from seven college-aged females (6 bilateral; 1 unilateral) were included. Participants underwent three data collection sessions with KT, sham, and no tape (NT) in a randomized order. During the session, participants performed a maximum vertical jump, single-leg squats and isometric knee extension. The KT intervention was applied according to the KT manual and the sham utilized the same pattern without tension. Pain level was evaluated using the numeric pain scale before, during and after each activity. Function was assessed as maximum vertical jump height and maximum isometric strength. A separate repeated measures ANOVA was used to compare each dependent variable (pain level, vertical jump height, and isometric strength) among the conditions. RESULTS: Reported pain scores were significantly lower (p = 0.05) during the maximal vertical jump test for KT (3.38 ± 1.26) compared to NT (4.54 ± 2.22). Significantly lower jump heights were found under KT (17.73 ± 3.06in) during the maximum vertical jump test compared to sham (18.65 ± 2.17in, p = 0.000) and NT (18.18 ± 2.93in, p = 0.008). CONCLUSIONS: The use of the KT tape with a tendon corrective strip and muscle facilitative strip was effective for decreasing pain associated with patellar tendinopathy during jump landing but led to decreased maximum jump height. CLINICAL TRIAL IDENTIFIER: NCT04153877.

Post total knee arthroplasty alignment of 347 consecutive obese patients receiving a fixed distal femoral cut of 6° valgus.

This study examined post-total knee arthroplasty (TKA) mechanical axis (MA), measured on hip-to-ankle radiographs, for patients with a body mass index (BMI) > 30 when a fixed 6° valgus distal femoral cut was made. A retrospective radiographic review included 347 TKAs receiving a distal femoral cut of 6° valgus. A distal femoral cut of 6° valgus successful established a neutral, ±3° MA in 86.7% of the 347 obese patients, with a slight tendency toward varus in patients with a BMI>40. A fixed cut may provide more consistent post-TKA alignment, when visualization of anatomical landmarks is made difficult by increased adipose tissue.

The effect of patellar thickness on gait biomechanics following total knee arthroplasty.

BACKGROUND: Patella resurfacing is commonly performed during total knee arthroplasty; however, determining the appropriate patellar thickness remains a challenge. The purpose of this study was to evaluate the role of post-TKA patellar thickness on knee extensor strength and biomechanical joint loading forces during walking and stair negotiation. METHODS: Fifteen patients (21 knees) underwent gait analysis prior to TKA and post-TKA at six weeks, three months, six months, and one year. Knee extensor strength and biomechanics were collected during level walking and stair negotiation and analyzed using Pearson correlation coefficients. RESULTS: Knee extensor strength was positively correlated to patellar thickness at three months and one year post-TKA (p ≤ .05). During walking, no significant correlations were present. During stair ascent, there was a positive correlation between patellar thickness and peak knee flexion angle one year post-TKA (p ≤ .05). During stair descent, there was a positive correlation between patellar thickness and maximum vertical ground reaction forces at one year post-TKA (p ≤ .01). CONCLUSIONS: The loss of patellar thickness when compared to measured pre-resurfacing thickness was correlated with a decrease in knee extensor strength; however, changes in patellar thickness were not significantly correlated to biomechanical loading forces during walking. Increases in demand of activity increase the torque to the knee joint, which elicit increases in compensatory motions, likely reducing the extent to which differences in joint loading during stair negotiation may be attributable to changes in patellar thickness. Therefore, the effect of post-patellar thickness on patient function in primary TKA is limited.

Fixed Distal Femoral Cut of 6° Valgus in Total Knee Arthroplasty: A Radiographic Review of 788 Consecutive Cases.

BACKGROUND: In place of the mechanical axis (MA), the use of the variable tibiofemoral angle is frequently used to plan measured resection bony cuts during total knee arthroplasty (TKA). This angle, coupled with operator-dependent variability of intramedullary distal femoral cutting guides, has the potential for catastrophic outcomes. Therefore, a simpler, fixed femoral cut of 6° valgus may be more appropriate when direct measurement of the MA is not possible. METHODS: This was a retrospective study of 788 consecutive TKAs, in which the distal femoral cut was set to 6° valgus. The preoperative and 6-week postoperative MA were measured on hip-to-ankle radiographs. Data were evaluated as a group as well as grouped by preoperative deformity (MA < -3°, -3° < MA < 3°, 3° < MA). RESULTS: Following TKA, MA alignment for all patients was 0.0° ± 2.3° (range, -7.0° to 8.0°). When grouped by pre-TKA alignment, 548 patients were considered varus (MA < -3°), 137 were neutral (-3° < MA < 3°), and 103 patients were valgus (3° < MA). When evaluating the post-TKA alignment achieved in the 3 groups, neutral alignment (-3° < MA < 3°) was established in 86.5% of varus patients, 86.1% of neutral patients, and 82.5% of valgus patients. CONCLUSION: A standard distal femoral cut of 6° resulted in a neutral MA in 86% of patients. While no single technique will be correct for all deformities, in the absence of sophisticated preoperative planning aids, this simple technique could provide a more reliable surgical technique than the measured tibiofemoral angle.

Allometric Grip Strength Norms for American Children.

Kocher, MH, Oba, Y, Kimura, IF, Stickley, CD, Morgan, CF, and Hetzler, RK. Allometric grip strength norms for American children. J Strength Cond Res 33(8): 2251-2261, 2019-To develop normative data from a large cohort of American school children (ages 6-18) for unscaled and allometrically scaled handgrip strength data that are uninfluenced by body size (body mass [BM] and stature [Ht]). Data (age, handgrip strength, BM, and Ht) were collected from the 2011-2012 and 2013-2014 National Health and Nutrition Examination Survey databases, resulting in 4,665 cases (2,384 boys and 2,281 girls). Multiple log-linear regressions were used to determine allometric exponents for BM and Ht separately for each age and sex to satisfy the common exponent and group difference principles described by Vanderburgh. Appropriateness of the allometric model was assessed through regression diagnostics, including normality and homoscedasticity of residuals. Allometrically scaled, ratio-scaled, and unscaled grip strength were then correlated with BM and Ht to examine the effectiveness of the procedure in controlling for body size. The data did not allow for development of a common exponent across age and sex that did not violate the common exponent and group difference principles. Correlations between allometrically scaled handgrip strength with BM and Ht were not significant (p ≤ 0.479) and approached zero, unlike correlations of unscaled handgrip strength with BM and Ht (p < 0.001 for all), indicating that allometric scaling was successful in removing the influence of body size. Allometric scaling handgrip strength by age and sex effectively controls for body size (Ht and BM) and perhaps maturation (Ht). The allometric exponents and normative values developed can be used to compare handgrip strength within age and sex while controlling for body size.

The effectiveness of scaling procedures for comparing ground reaction forces.

Various scaling methods are used when attempting to remove the influence of anthropometric differences on ground reaction forces (GRF) when comparing groups. Though commonly used, ratio scaling often results in an over-correction. Allometric scaling has previously been suggested for kinetic variables but its effectiveness in partialing out the effect of anthropometrics is unknown due to a lack of consistent application. This study examined the effectiveness of allometric scaling vertical, braking and propulsive GRF and loading rate for 84 males and 47 females while running at 4.0 m/s. Raw, unfiltered data were ratio scaled by body mass (BM), height (HT), and BM multiplied by HT (BM∗HT). Gender specific exponents for allometric scaling were determined by performing a log-linear (for BM and HT individually) or log-multilinear regression (BMHT). Pearson productmoment correlations were used to assess the effectiveness of each scaling method. Ratio scaling by BM, HT, or BM∗HT resulted in an over-correction of the data for most variables and left a considerable portion of the variance still attributable to anthropometrics. Allometric scaling by BM successfully removed the effect of BM and HT for all variables except for braking GRF in males and vertical GRF in females. However, allometric scaling for BMHT successfully removed the effect of BM and HT for all reactionary forces in both genders. Based on these results, allometric scaling for BMHT was the most appropriate scaling method for partialing out the effect of BM and HT on kinetic variables to allow for effective comparisons between groups or individuals.

Dynamic Varus and the Development of Iliotibial Band Syndrome.

CONTEXT: Although the risk of osteoarthritis development after acute knee injury has been widely studied, the long-term consequences of knee overuse injury are not well understood. OBJECTIVE: To identify the relationship between gait-related risk factors associated with osteoarthritis and the development of iliotibial band syndrome (ITBS) in members of a single University Army Reserve Officers' Training Corps unit. DESIGN: Prospective cohort study. SETTING: Biomechanics laboratory. PATIENTS OR OTHER PARTICIPANTS: Sixty-eight cadets undergoing standardized physical fitness training. INTERVENTION(S): Three-dimensional lower extremity kinematics (240 Hz) and kinetics (960 Hz) were collected for 3 bilateral trials during shod running at 4.0 m/s ± 10%. Injury tracking was conducted for 7 months of training. MAIN OUTCOME MEASURE(S): Biomechanical variables, including varus thrust and knee-adduction moment, were compared between the injured and control groups. RESULTS: Twenty-six cadets with no history of overuse injury served as the control group, whereas 6 cadets (7 limbs) who developed ITBS that required them to modify their training program or seek medical care (or both) served as the injured group. Maximum varus velocity was higher ( P = .006) and occurred sooner during stance ( P = .04) in the injured group than in the control group, indicating greater varus thrust. Maximum knee-varus angle and maximum knee-adduction moment were higher ( P = .02 and P = .002, respectively) and vertical stiffness was lower ( P = .03) in the injured group. CONCLUSIONS: Measures of dynamic varus stability appeared to be altered in individuals who developed ITBS. Biomechanical knee variables previously identified as increasing the risk for knee osteoarthritis were also associated with the development of ITBS in healthy adults.

Effect of 8 weeks of concurrent plyometric and running training on spatiotemporal and physiological variables of novice runners.

Concurrent plyometric and running training has the potential to improve running economy (RE) and performance through increasing muscle strength and power, but the possible effect on spatiotemporal parameters of running has not been studied yet. The aim of this study was to compare the effect of 8 weeks of concurrent plyometric and running training on spatiotemporal parameters and physiological variables of novice runners. Twenty-five male participants were randomly assigned into two training groups; running group (RG) (n = 11) and running + plyometric group (RPG) (n = 14). Both groups performed 8 weeks of running training programme, and only the RPG performed a concurrent plyometric training programme (two sessions per week). Anthropometric, physiological (VO2max, heart rate and RE) and spatiotemporal variables (contact and flight times, step rate and length) were registered before and after the intervention. In comparison to RG, the RPG reduced step rate and increased flight times at the same running speeds (P < .05) while contact times remained constant. Significant increases in pre- and post-training (P < .05) were found in RPG for squat jump and 5 bound test, while RG remained unchanged. Peak speed, ventilatory threshold (VT) speed and respiratory compensation threshold (RCT) speed increased (P < .05) for both groups, although peak speed and VO2max increased more in the RPG than in the RG. In conclusion, concurrent plyometric and running training entails a reduction in step rate, as well as increases in VT speed, RCT speed, peak speed and VO2max. Athletes could benefit from plyometric training in order to improve their strength, which would contribute to them attaining higher running speeds.

Reliability of clinically feasible dual-task tests: Expanded timed get up and go test as a motor task on young healthy individuals.

Dual-Task testing has been reported to have a higher sensitivity to deficits associated with concussion; however, the feasibility as a clinical or field test is questionable due to the requirements of laboratory-based equipment. With an overarching goal of exploration of clinically feasible Dual-Task testing options, the specific aims of this study were 1) to evaluate the reliability of Dual-Task testing methods using the Expanded Timed Get-Up-and-Go (ETGUG) paired with Backward Digit Recall (BDR), Serial Seven (SS), and Auditory Pure Switch Task (APST), and 2) to determine the effects of Dual-Task testing on motor and cognitive performance in healthy college-aged individuals. Fifty-four healthy young adults completed two separate testing sessions, which consisted of Single-Task tests in a randomized order followed by 3 pairs of Dual-Task tests in a randomized order. Test-retest reliability for ETGUG time to completion was excellent for all Single- and Dual-Task conditions (ICC 0.89-0.92); however, ETGUGBDR and ETGUGSS were associated with learning effects (p=0.002 and 0.007, respectively). Test-retest reliability for Response Rate of the cognitive tasks was lower than those of motor task and all outcomes were associated with learning effects. The completion time of the ETGUGAPST pair indicated excellent reliability with no learning effect. Performance level declined in all tasks under Dual-Task conditions compared to Single-Task; however, motor tasks showed larger deficits indicating the prioritization of the cognitive task compared to the motor task.

The effects of ankle braces and taping on lower extremity running kinematics and energy expenditure in healthy, non-injured adults.

Ankle braces and taping are commonly used to prevent ankle sprains and allow return to play following injury, however, it is unclear how passive restriction of joint motion may effect running gait kinematics and energy expenditure during exercise. The purpose of this study was to determine the effect of different types of ankle supports on lower extremity kinematics and energy expenditure during continuous running. Thirteen healthy physically active adults ran at self-selected speed on the treadmill for 30min in four different ankle support conditions: semi-rigid hinged brace, lace-up brace, tape and control. Three-dimensional lower extremity kinematics and energy expenditure were recorded every five minutes. The semi-rigid hinged brace was most effective in restricting frontal plane ankle motion. The lace-up brace and tape restricted sagittal plane ankle motion, while semi-rigid hinged bracing allowed for normal sagittal plane ankle kinematics. Kinematic changes from all three ankle supports were generally persistent through 25-30min of exercise. Only tape influenced knee kinematics, limiting flexion velocity and flexion-extension excursion. Small but significant increased in energy expenditure was found in tape and semi-rigid hinged brace conditions; however, the increases were not to any practically significant level (<0.5kcal/min).

Differences in Spatiotemporal Parameters Between Trained Runners and Untrained Participants.

Gómez-Molina, J, Ogueta-Alday, A, Stickley, C, Tobalina, JC, Cabrejas-Ugartondo, J, and García-López, J. Differences in spatiotemporal parameters between trained runners and untrained participants. J Strength Cond Res 31(8): 2169-2175, 2017-The aim of this study was to compare the spatiotemporal parameters of trained runners and untrained participants with the same foot strike pattern (rearfoot) during running at controlled speeds. Twenty-one participants were classified in 2 groups according to their training experience: Trained (n = 10, amateur runners with long distance training experience) and Untrained (n = 11, healthy untrained participants). Anthropometric variables were recorded, and the participants performed both a submaximal (between 9 and 15 km·h) and a graded exercise running test (from 6 km·h until exhaustion) on a treadmill. Physiological (V[Combining Dot Above]O2max, heart rate, running economy [RE], peak speed …) and biomechanical variables (contact and flight times, step rate, and length) were simultaneously registered. Trained runners showed higher step rate and shorter step length than the Untrained group at the same running speeds (between 4 and 7%, p ≤ 0.05) and at the same physiological intensities (between 7 and 11%, p ≤ 0.05). However, there were no differences in contact and flight times between groups. Significant differences (p ≤ 0.05) and large effect sizes (Cohen's d) between groups were found for body mass, sum of 6 skinfolds, V[Combining Dot Above]O2max, peak speed, and ventilatory threshold and respiratory compensation threshold speeds. The Trained group also showed a ∼7% better RE (ml·kg·km) than the Untrained group. In conclusion, adopting higher step rate and shorter step length may be an adaptive mechanism of the Trained group to reduce injury risk and possibly improve RE. However, contact and flight times were consistent regardless of training level.

Allometric Grip Strength Norms for Children of Hawaiian Lineage.

The purpose of the study was to determine allometric exponents for scaling grip strength in children that effectively control for body mass (BM) and stature (Ht) and to develop normative grip strength data for Hawaiian children. One thousand, four hundred thirty-seven students (754 boys) from a rural community in Hawaii participated in this 5-year study, resulting in 2,567 data points. Handgrip strength, BM, and Ht were collected every year. Multiple log-linear regression was used to determine allometric exponents for BM and Ht. Appropriateness of the allometric model was assessed through regression diagnostics, including normality of residuals and homoscedasticity. Allometrically scaled, ratio-scaled, and unscaled grip strength were then correlated with BM and Ht to examine the effectiveness of the procedure in controlling for body size. Allometric exponents for BM and Ht were calculated separately for each age group of boys and girls to satisfy the common exponent and group difference principles described by Vanderburgh. Unscaled grip strength had moderate to strong positive correlations with BM and Ht (p ≤ 0.05 for all) for all age groups. Ratio-scaled handgrip strength had significant moderate to strong negative correlations with BM (p ≤ 0.05 for all) and, to a lesser extent, Ht (p ≤ 0.05 for 8- to 12-year-old boys; p ≤ 0.05 for 8- to 12- and 14-year-old girls). Correlations between allometrically scaled handgrip strength and BM and Ht were not significant and approached zero. This study was the first to allometrically scale handgrip strength for BM and Ht in Hawaiian children. Allometric scaling applied to grip strength provides a useful expression of grip strength free of the confounding influence of body size.