The Effect of Exercise-Induced Central Fatigue on Cervical Spine Joint Position Error, Strength, and Endurance.

Background: Fatigue is common in sports, impairing performance and increasing injury risk, yet little is known regarding fatigue and concussion. Impaired neck neuromuscular function may contribute to concussion at baseline, where central fatigue may further impair neck function resulting in increased concussion risk. These effects may be magnified in athletes with a history of concussion. Purpose: To determine the effect of exercise induced central fatigue on neck joint position error, strength, and endurance in healthy subjects and those with a history of concussion. The investigators hypothesized that EICF would have a negative effect on all variables. Study Design: Healthy subjects were examined using a single factor, within-subjects repeated measures design. Concussion history subjects were examined using a single-subject design. Methods: Nineteen healthy subjects and five subjects with a history of concussion were recruited for the study. Cervical joint position error, muscle strength, and neck flexor endurance were tested before and after exercise induced fatigue. Results: There was a significant increase in constant (p = 0.0027) and absolute joint position error (JPE) (p < 0.001); decrease in neck flexor endurance (p < 0.001); and decrease neck strength into cervical flexion (p = 0.01) in healthy subjects following fatigue. Among concussion history subjects, five demonstrated a significant increase in absolute and constant JPE (p < 0.05); four demonstrated a significant decrease in neck flexor endurance (p < 0.05); one in neck flexion muscle strength (p < 0.05); and three in neck extension and rotation muscle strength (p < 0.05) following fatigue. Conclusions: Cervical neuromuscular function deteriorated following fatigue in healthy subjects. Resulting impairments may affect force alterations in cervical control, potentially increasing concussion risk. Concussion history subjects descriptively demonstrated similar results, however further research should examine formal comparisons involving subjects with and without concussion history. Level of Evidence: 3b.

Effect of verbal instructions on trunk muscle activity during volitional preemptive abdominal contraction.

OBJECTIVE: This study investigated the effect of Verbal Instruction (VI) strategies on trunk muscle contraction among healthy subjects. The effect of three VI Abdominal Drawing-In Maneuver (ADIM) and two VI Abdominal Bracing Maneuver (ABM) strategies on left Internal (LIO) and External Oblique (LEO) and bilateral superficial Multifidi (sMf) activation was examined. DESIGN: Within-subjects, repeated measure design. METHODS: Surface EMG (sEMG) measured LIO, LEO, and sMf activity in 28 subjects (mean age 23.5 ± 5.5 years). Testing included five supine hook-lying and five quiet standing conditions. RESULTS: One-way ANOVAs demonstrated no significant main effect for ADIM or ABM in supine or standing (p > .05). Muscle activation amplitudes during VPAC conditions demonstrated higher mean values for standing versus supine (p < .05) except for two conditions involving LEO. Friedman Tests for dominant strategy demonstrated a significant main effect for ADIM-VI and ABM-VI strategies. Post-hoc testing generally showed the dominant strategy to be significantly higher versus others. CONCLUSION: No single preferred VI cue for ADIM or ABM was observed. Each subject's dominant strategy dictated the most suitable VI. Standing was preferred for LIO and sMf activation, whereas position did not change LEO activation. Non-significant correlations between all muscle pairings during all ADIM and ABM strategies were observed. These findings may suggest the need for healthcare providers who understand the intricacies of trunk stability to teach and monitor VPAC with either ADIM or ABM options.

Incidence and Risk Factors for Bone Stress Injuries in United States Air Force Special Warfare Trainees.

OBJECTIVES: To determine (1) the incidence rate of lower extremity (LE) bone stress injuries (BSIs) in United States Air Force Special Warfare (AFSPECWAR) trainees during the first 120 days of training, and (2) factors associated with sustaining a LE BSI. DESIGN: Retrospective cohort study. METHODS: AFSPECWAR Airmen (n = 2,290, mean age = 23.7 ± 3.6 years) entering an intensive 8-week preparatory course "SW-Prep" between October 2017 and May 2021. We compared anthropometric measurements, previous musculoskeletal injury (MSKI), fitness measures, and prior high-impact sports participation in those that did and did not suffer a BSI during the 120-day observation period using independent t-tests and chi-square tests. A multivariable binary logistic regression was used to determine factors associated with suffering a BSI. RESULTS: A total of 124 AFSPECWAR trainees suffered a BSI during the surveillance period, yielding an incidence proportion of 5.41% and an incidence rate of 1.4 BSIs per 100 person-months. The multivariate logistic regression revealed that lower 2-minute sit-up scores, no prior history of participation in a high-impact high-school sport, and a history of prior LE MSKI were associated with suffering a BSI. A receiver operator characteristic curve analysis yielded an area under the curve (AUC) of 0.727. CONCLUSION: BSI incidence proportion for our sample was similar to those seen in other military settings. Military trainees without a history of high-impact sports participation who achieve lower scores on sit-ups tests and have a history of LE MSKI have a higher risk for developing a LE BSI during the first 120 days of AFSPECWAR training.

The Effect of Volitional Preemptive Abdominal Contraction on Biomechanical Measures During A Front Versus Back Loaded Barbell Squat.

Background: Weightlifting is growing in popularity among recreational and competitive athletes. The barbell back squat (BackS) is commonly included in these training programs, while the barbell front squat (FrontS) is commonly performed as a component of other lifts such as the power clean or clean and jerk, it is less commonly practiced in isolation. Hypothesis/Purpose: The purpose of this study was to examine the effects of VPAC performance on trunk muscle and LE biomechanical responses during loaded BackS versus FrontS in healthy subjects. Study Design: Controlled Laboratory Study. Methods: Healthy male subjects with the ability to perform a sub-maximal loaded barbell squat lift were recruited. Subjects completed informed consent, demographic/medical history questionnaires and an instructional video. Subjects practiced VPAC and received feedback. Surface electromyography (sEMG) electrodes and kinematic markers were applied. Muscles included were the internal oblique (IO), external oblique (EO), rectus abdominis, iliocostalis lumborum (ICL), superficial multifidi, rectus femoris, vastus lateralis, biceps femoris, and gluteus maximus. Maximal voluntary isometric contractions established reference sEMG values. A squat one-rep-max (1RM) was predicted by researchers using a three to five repetition maximum (3RM, 5RM) load protocol. Subjects performed BackS trials at 75% 1RM while FrontS trials were performed at 75% BackS weight, both with and without VPAC. Subjects performed three repetitions of each condition with feet positioned on two adjacent force plates. Significant interactions and main effects were tested using a 2(VPAC strategy) x 2(squat variation) and 2(VPAC strategy) x 2(direction) within-subject repeated measures ANOVAs. Tukey's Post-Hoc tests identified the location of significant differences. Results: Trunk muscle activity was significantly higher during FrontS versus BackS regardless of VPAC condition. (IO: p=0.018, EO: p<0.001, ICL: p<0.001) VPAC increased performance time for both squat variations (p=.0011), which may be associated with decreased detrimental force potential on the lumbar spine and knees. VPAC led to improved ability to maintain a neutral lumbar spine during both squat variations. This finding is associated with decreased detrimental force potential on the lumbar spine. Conclusions: Findings could help guide practitioners and coaches to choose squat variations and incorporate VPAC strategies during their treatments and/or training programs. Level of Evidence: Level 3©The Author(s).

Safe Administration and Low Healthcare Utilization Following Musculoskeletal Corticosteroid Injections by U. S. Military Physical Therapists.

INTRODUCTION: Musculoskeletal (MSK) injuries make up a significant proportion of conditions treated by military healthcare providers during wartime. Though many common MSK injuries may benefit from corticosteroid injection (CSI), a shortage of qualified military clinicians has led to diminished access to appropriate care. Longer wait times to receive treatment pose detrimental effects on military readiness and have garnered the attention of military leaders. One solution was the development of advanced training for United States Air Force physical therapists (USAF PTs) to gain clinical privileges in administering CSI. The objectives of this study were to determine in USAF PTs (1) the prevalence of those with privileges to administer CSI; (2) the type and (3) safety of MSK CSI administered; (4) incidence of CSI complications; (5) healthcare utilization following CSI; and (6) barriers to obtaining and practicing CSI privileges. MATERIALS AND METHODS: United States Air Force PTs with CSI privileges received instructions to follow a link to an anonymous Google survey. Electronic medical record reviews were conducted by three USAF PTs to determine the occurrence and severity of CSI complications provided by USAF PTs and advanced healthcare providers (AHPs). The principal investigator conducted further review of the patients' electronic medical records to calculate healthcare utilization following CSI administered by USAF PTs. A hospital administrator selected cases of similar diagnoses treated with CSI by USAF AHPs. The number selected cases treated by AHPs are similar to the number of CSI cases treated by USAF PTs. RESULTS: Eleven USAF PTs held CSI privileges. No major complications associated with CSI were recorded. Of the 95 CSI cases treated by USAF PTs, 27 (28.4%) reported increased pain compared to 24 (27.9%) of 86 CSI cases treated by AHPs (P = .94). Healthcare utilization for the number of follow-up visits, imaging, and additional laboratory tests following CSI by USAF PTs was lower compared to AHPs (chi-square; P < .0069). CONCLUSION: Nine percentage of USAF PTs held CSI privileges. United States Air Force PTs were equally safe as AHPs who administered CSI and associated with a lower rate of healthcare utilization following the intervention. Training USAF PTs to administer CSI could be the standard for all USAF PTs who meet qualification requirements. Adoption of similar training and credentialing policies for civilian PTs warrants further exploration.

Variability of Intradiscal Pressure During Cervical Spine Posterior-Anterior Mobilization: A Cadaveric Investigation.

OBJECTIVES: The purpose of this study was to investigate in cadaveric specimens the reliability of measuring cervical intradiscal pressure (CIDP) and if posterior-anterior (PA) mobilizations targeting the cervical spine were associated with CIDP changes. METHODS: Cervical PA mobilizations were performed on the spinous processes of 7 (3 men, 4 women) cadaveric specimens using a servo-controlled linear actuator to provide 25N and 45N forces. CIDP measurements were performed at C4-5, C5-6, C6-7, and C7-T1 intervertebral discs (IVDs) using a fiberoptic catheter system that recorded CIDP for each IVD cervical segment. To assess CIDP measurement reliability, the intraclass correlation coefficient (ICC [3,k]) was calculated. Repeated measures Friedman analysis of variance assessed effect of cervical mobilizations on CIDP for before, during, and immediately after mobilization at 25N and 45N forces for each cervical IVD segment. RESULTS: All CIDP measurements demonstrated excellent reliability (ICC >0.98). During the 25N mobilizations, the median CIDP varied from -0.12 to 0.91 (interquartile range, 5.22-5.36), while for 45N mobilizations the median ranged from -0.94 to 1.21 (interquartile range, -7.74 to 43.49). These changes were not statistically significant (P > .40) during 25N and 45N PA mobilizations, with the exception of C5-6 CIDP at 25N and 45N (P = .05 and .018, respectively). CONCLUSION: There was high CIDP variability between cadavers during and after mobilization. Mobilizations of 1 cervical vertebra resulted in both CIDP increase or decrease at adjacent and remote cervical IVD segments that were not consistent. Cervical PA mobilizations produced variable CIDP changes at adjacent and remote cervical segments in cadavers.

Influence of clinical experience on accuracy and safety of obliquus capitus inferior dry needling in unembalmed cadavers.

BACKGROUND: Suboccipital myofascial trigger points are common in tension-type headaches. OBJECTIVES: Compare the influence of clinical experience on the accuracy and safety of dry needle placement on the C2 laminar arch using a cranial-medial and caudal-medial technique to target obliquus capitus inferior in unembalmed cadavers. METHODS: Three physical therapists inserted three 50 mm dry needles, per technique, individually toward the C2 laminar arch targeting the obliquus capitus inferior. Ultrasound video of each trial was recorded, and an investigator trained in ultrasound interpretation and blinded to experience level recorded needling accuracy. RESULTS: The novice, experienced and expert clinicians were accurate on 73.8%, 59.5% and 71.4% of caudal-medial trials, and 14.3%, 16.7% and 66.7% of cranial-medial trials, respectively, with each clinician striking the spinal cord at least once. The expert clinician was 10 times more likely to accurately reach the C2 laminar arch using the cranial-medial direction than the experienced and novice clinicians. CONCLUSION: Increased clinical experience improved accuracy reaching the C2 laminar arch, with all investigators being more accurate with the caudal-medial technique. Greater experience did not eliminate risk as all investigators recorded at least one incident of striking the spinal cord. Fewer spinal cord strikes occurred with the cranial-medial than the caudal-medial technique.

Abdominal bracing changes lower quarter muscle activity but not reach distances during active forward reach on an unstable surface.

OBJECTIVE: This study examined the effects of abdominal bracing maneuver (ABM) performance on stable and unstable surfaces on active forward reach (AFR) distance as a measure of trunk control, measuring changes in reach distance and muscle activation patterns. DESIGN: Single-group, repeated measures design. METHODS: Twenty-eight subjects (mean age 25 ± 5.09 years) performed an AFR with and without ABM while on stable and unstable surfaces. Lower quarter muscle activity and forward reach distances were recorded. RESULTS: Forward reach distances on the unstable surface were significantly decreased compared to the stable condition with and without ABM (p < .001). The surface-by-contraction interaction was significant for the tibialis anterior (TA) and gastrocnemius (GS). Significant main effects were found for internal oblique, external oblique, gluteus maximus, biceps femoris, TA, and GS, where muscle activity significantly increased during the ABM trials. The interaction between surface and contraction was significant for the TA and GS muscles. TA (p = .007) and GS (p < .001) activity increased with ABM on the unstable surface. TA activity increased with ABM on the stable surface (TA: p < .001). CONCLUSION: Reach distances decreased on the unstable surface, but ABM did not change reaching distance. Ankle muscle co-contraction occurred during ABM trials and posterior chain activity increased. These changes suggest ABM may be beneficial during forward reaching activities.

The Immediate Effects of Foam Rolling and Stretching on Iliotibial Band Stiffness: A Randomized Controlled Trial.

BACKGROUND: Iliotibial Band Syndrome (ITBS) is a common clinical condition likely caused by abnormal compressive forces to the iliotibial band (ITB). Stretching interventions are common in ITBS treatment and may predominantly affect tensor fascia latae (TFL). Another ITBS treatment is foam rolling, which may more directly affect the ITB. Shear wave ultrasound elastography (SWUE) measures real-time soft tissue stiffness, allowing tissue changes to be measured and compared. PURPOSE: To examine effects of foam rolling and iliotibial complex stretching on ITB stiffness at 0˚ and 10˚ of hip adduction and hip adduction passive range of motion (PROM). STUDY DESIGN: Randomized controlled trial. METHODS: Data from 11 males (age = 30.5 ± 9.0 years, Body Mass Index (BMI) = 27.8 ± 4.0) and 19 females (age = 23.5 ± 4.9, BMI = 23.2 ± 2.1) were analyzed for this study. Subjects were randomly assigned to one of three groups: control, stretching, and foam rolling. Shear wave ultrasound elastography measurements included ITB Young's modulus at the mid-thigh, the distal femur and the TFL muscle belly. ITB-to-femur depth was measured at mid-thigh level. Hip adduction PROM was measured from digital images taken during the movement. RESULTS: No significant interactions or main effects were found for group or time differences in ITB Young's modulus at the three measured locations. The ITB stiffness at the mid-thigh and distal femur increased with 10° adduction, but TFL stiffness did not increase. A main effect for adduction PROM was observed, where PROM increased 0.8˚ post-treatment (p = 0.02). CONCLUSION: A single episode of stretching and foam rolling does not affect short-term ITB stiffness. The lack of ITB stiffness changes may be from an inadequate intervention stimulus or indicate that the interventions have no impact on ITB stiffness. LEVELS OF EVIDENCE: 1b.

The relationship between measures of foot mobility and subtalar joint stiffness using vibration energy with color Doppler imaging-A clinical proof-of-concept validation study.

INTRODUCTION: Subtalar joint (STJ) dysfunction can contribute to movement disturbances. Vibration energy with color Doppler imaging (VECDI) may be useful for detecting STJ stiffness changes. OBJECTIVES: (1) Support proof-of-concept that VECDI could detect STJ stiffness differences; (2) Establish STJ stiffness range in asymptomatic volunteers; (3) Examine relationships between STJ stiffness and foot mobility; and (4) Assess VECDI precision and reliability for examining STJ stiffness. METHODS: After establishing cadaveric testing model proof-of-concept, STJ stiffness (threshold units, ΔTU), ankle complex passive range-of-motion (PROM) and midfoot-width-difference (MFWDiff) data were collected in 28 asymptomatic subjects in vivo. Three reliability measurements were collected per variable; Rater-1 collected on all subjects and rater-2 on the first ten subjects. Subjects were classified into three STJ stiffness groups. RESULTS: Cadaveric VECDI measurement intra-rater reliability was 0.80. A significantly lower STJ ΔTU (p = .002) and ankle complex PROM (p < .001) was observed during the screw fixation versus normal condition. A fair correlation (r = 0.660) was observed between cadaveric ΔTU and ankle complex PROM. In vivo VECDI measurements demonstrated good intra-rater (0.76-0.84) versus poor inter-rater (-3.11) reliability. Significant positive correlations were found between STJ stiffness and both dorsum (r = .440) and posterior (r = .390) PROM. MFWDiff exhibited poor relationships with stiffness (r = .103) and either dorsum (r = .256) or posterior (r = .301) PROM. STJ stiffness ranged from 2.33 to 7.50 ΔTUs, categorizing subjects' STJ stiffness as increased (n = 6), normal (n = 15), or decreased (n = 7). Significant ANOVA main effects for classification were found based on ΔTU (p< .001), dorsum PROM (p = .017), and posterior PROM (p = .036). Post-hoc tests revealed significant: (1) ΔTU differences between all stiffness groups (p < .001); (2) dorsum PROM differences between the increased versus normal (p = .044) and decreased (p = .017) stiffness groups; and (3) posterior PROM differences between the increased versus decreased stiffness groups (p = .044). A good relationship was found between STJ stiffness and dorsum PROM in the increased stiffness group (r = .853) versus poor, nonsignificant relationships in the normal (r = -.042) or decreased stiffness (r = -.014) groups. CONCLUSION: PROM may not clinically explain all aspects of joint mobility. Joint VECDI stiffness assessment should be considered as a complimentary measurement technique.

Glenohumeral joint capsular tissue tension loading correlates moderately with shear wave elastography: a cadaveric investigation.

PURPOSE: The purpose of this study was to investigate changes in the mechanical properties of capsular tissue using shear wave elastography (SWE) and a durometer under various tensile loads, and to explore the reliability and correlation of SWE and durometer measurements to evaluate whether SWE technology could be used to assess tissue changes during capsule tensile loading. METHODS: The inferior glenohumeral joint capsule was harvested from 10 fresh human cadaveric specimens. Tensile loading was applied to the capsular tissue using 1-, 3-, 5-, and 8-kg weights. Blinded investigators measured tissue stiffness and hardness during loading using SWE and a durometer, respectively. Intraobserver reliability was established for SWE and durometer measurements using intraclass correlation coefficients (ICCs). The Pearson product-moment correlation was used to assess the associations between SWE and durometer measurements. RESULTS: The ICC3,5 for durometer measurements was 0.90 (95% confidence interval [CI], 0.79 to 0.96; P<0.001) and 0.95 (95% CI, 0.88 to 0.98; P<0.001) for SWE measurements. The Pearson correlation coefficient values for 1-, 3-, and 5-kg weights were 0.56 (P=0.095), 0.36 (P=0.313), and -0.56 (P=0.089), respectively. When the 1- and 3-kg weights were combined, the ICC3,5 was 0.72 (P<0.001), and it was 0.62 (P<0.001) when the 1-, 3-, and 5-kg weights were combined. The 8-kg measurements were severely limited due to SWE measurement saturation of the tissue samples. CONCLUSION: This study suggests that SWE is reliable for measuring capsular tissue stiffness changes in vitro at lower loads (1 and 3 kg) and provides a baseline for the non-invasive evaluation of effects of joint loading and mobilization on capsular tissues in vivo.

Large variability found in musculoskeletal physiotherapy scope of practice throughout WCPT and IFOMPT affiliated countries: An international survey.

BACKGROUND: Advanced practice physiotherapy (APP) rights are part of the evolution of the Physical Therapy profession. To date, no study has investigated musculoskeletal APP rights within the World Confederation for Physical Therapy (WCPT). OBJECTIVE: To investigate musculoskeletal APP rights for physical therapists worldwide and examine the relationship between level of education (entry and post-professional) and direct access for countries that are vs. are not members of the International Federation of Orthopaedic Manipulative Physical Therapists (IFOMPT). DESIGN: Cross-sectional study with descriptive and exploratory online surveys. METHODS: An electronic survey-based descriptive and exploratory investigation was conducted. We assessed variability between WCPT member organizations descriptively and the strength of the relationships among the number and types of APP rights with: (1) country affiliation to IFOMPT; (2) entry-level professional degree; (3) post-professional training; and (4) direct access. RESULTS: Some countries reported having the right to practice all 20 APP rights while others reported no APP rights. Countries with IFOMPT member organization countries displayed fair correlation (rs = .48, p < .03) between entry-level physical therapy degrees and number of APP rights. IFOMPT member organization countries were less likely to require post-professional training for direct access and manipulation. CONCLUSION: APP rights for countries with direct access were significantly higher than for countries without direct access. IFOMPT member organizations demonstrated higher APP rights prevalence and were less likely to require post-professional training to obtain the right to direct access and perform manipulation.

Musicians injuries: Upper quarter motor control deficits in musicians with prolonged symptoms - A case-control study.

STUDY DESIGN: Case-control study. BACKGROUND: A large number of student and professional musicians are affected by long term playing related musculoskeletal disorders (PRMSDs) during their career, with prevalence rates above 80%. OBJECTIVE: To investigate if there were differences between musicians with and without prolonged symptoms of upper quarter PRMSDs in the presence of: (1) scapular dyskinesis; (2) cervical motor control and endurance deficits. METHODS: Seventy-two musicians (24 males; 48 females) were matched based on sex, type of instrument and average hours played per week and assigned to one of two groups: A symptomatic group (mean age 23.3 ±â€¯8.2 years) with history of prolonged PRMSDs (constant symptoms lasting more than one week) during the past year; and a control group (mean age 25 ±â€¯10.5 years) with no history of PRMSDs lasting more than one week. Musicians completed a questionnaire and underwent clinical testing for the presence of scapular dyskinesis and cervical motor control and endurance deficits using the following tests: (1) cervical flexor endurance test; (2) scapular dyskinesis test; and (3) craniocervical flexion test. Assessor blinding as to group assignment was ensured. RESULTS: Participants in the symptomatic group presented with a statistically significant higher prevalence of positive scapular dyskinesis (P < .0001; OR = 7.8) and lower scores for the craniocervical flexion test (P < .0001). CONCLUSION: Musicians with prolonged symptoms of PRMSDs presented with higher prevalence of scapular and cervical motor control deficits detected by standard clinical tests when compared to the control group. LEVEL OF EVIDENCE: Therapy, level 4. CLINICALTRIALS. GOV IDENTIFIER: NCT02267395.

Deep Neck Flexor Endurance in the Adolescent and Young Adult: Normative Data and Associated Attributes.

BACKGROUND: Deep neck flexor (DNF) muscles stabilize the neck and contribute to head acceleration control. The function of DNF in cervical spine dynamic stabilization has not been examined in athletes of any age group, including adolescents. This investigation was necessary prior to studying the DNF muscles' role in cervical spine injury patterns. OBJECTIVES: The objectives of this study were (1) to determine average Deep Neck Flexor Endurance Test (DNFET) time scores in high school-aged and university-aged subjects (aged 14-22 years); and (2) to establish the relationship between gender and age for adolescent DNFET time scores. DESIGN: Cross-sectional design. SETTING: Public high school and private university. PARTICIPANTS: A total of 81 (40 male, 41 female) healthy high school and collegiate athletes. INTERVENTION: DNFET time scores (in seconds) were collected and means values were calculated. Interrater reliability was established using the first 15 university-aged subjects enrolled in the study. MAIN OUTCOMES: Mean DNFET time (seconds) scores. RESULTS: The DNF muscle endurance interrater reliability coefficient of reproducibility for 4 allied health clinicians was intraclass correlation coefficient (2,4) 0.712 (confidence interval, 0.24-0.85). The mean (± standard deviation) DNFET time score for females was 31.86 (±8.53) seconds versus 35.57 (±10.43) seconds for males. The DNFET performance demonstrated a significant but fair correlation with age (r = 0.401, P = .0001). No significant performance differences were found between male and female subjects in the 14- to 17-year-old group (U = 187.0, P = .285), the 18- to 22-year-old group (U = 145.0, P = .215), or the total male versus female subject groups (U = 653.0, P = .083). CONCLUSION: Our study establishes a normative data set available for the DNFET in the adolescent population. The fair correlation between DNFET time scores and age is consistent with other studies. These findings serve as a basis for clinician testing, objectifying, and monitoring DNF dysfunction in an adolescent athletic population. LEVEL OF EVIDENCE: II.

The Effect of Current Low Back Pain on Volitional Preemptive Abdominal Activation During a Loaded Forward Reach Activity.

BACKGROUND: A volitional preemptive abdominal contraction (VPAC) supports trunk stability during functional activity. Pain-free individuals can sustain VPAC during function, but such has not been reported for individuals with current low back pain (cLBP). OBJECTIVE: To examine whether cLBP affects VPAC performance during a loaded forward reach (LFR) task. DESIGN: Observational crossover study. SETTING: Laboratory. PARTICIPANTS: A total of 18 controls and 17 subjects with cLBP with pain ratings of 1/10 to 4/10 on a visual analog scale. INTERVENTIONS: Transverse abdominis (TrA) thickness measurements were recorded by blinded researchers from M-mode ultrasound imaging during 4 conditions: (1) quiet standing without abdominal drawing-in maneuver (ADIM); (2) quiet standing with ADIM; (3) LFR without ADIM; and (4) LFR with ADIM. A physical therapist with 29 years of experience collected historical and examination data. MAIN OUTCOME MEASURES: TrA muscle thickness (mm). RESULTS: A 2 (group) × 2 (contraction) × 2 (reach) analysis of variance demonstrated a significant group × contraction interaction (F [1, 31] = 4.499, P = .04) where ADIM produced greater TrA thickness increases in PLBP subjects (2.18 mm) versus controls (1.36 mm). We observed a significant main effect for reach (F [1, 31] = 14.989, P < .001), where LFR activity produced a greater TrA thickness (6.15 ± 2.48 mm) versus quiet standing (5.30 ± 2.12 mm). CONCLUSIONS: Subjects with cLBP demonstrated a greater increase in TrA activation during ADIM versus controls.

Volitional Spine Stabilization During a Drop Vertical Jump From Different Landing Heights: Implications for Anterior Cruciate Ligament Injury.

CONTEXT: Volitional preemptive abdominal contraction (VPAC) during dynamic activities may alter trunk motion, but the role of the core musculature in positioning the trunk during landing tasks is unclear. OBJECTIVE: To determine whether volitional core-muscle activation incorporated during a drop vertical jump alters lower extremity kinematics and kinetics, as well as trunk and lower extremity muscle activity at different landing heights. DESIGN: Controlled laboratory study. SETTING: Clinical biomechanics laboratory. PATIENTS OR OTHER PARTICIPANTS: Thirty-two young healthy adults, consisting of 17 men (age = 25.24 ± 2.88 years, height = 1.85 ± 0.06 m, mass = 89.68 ± 16.80 kg) and 15 women (age = 23.93 ± 1.33 years, height = 1.67 ± 0.08 m, mass = 89.68 ± 5.28 kg). INTERVENTION(S): Core-muscle activation using VPAC. MAIN OUTCOME MEASURE(S): We collected 3-dimensional ankle, knee, and hip motions, moments, and powers; ground reaction forces; and trunk and lower extremity muscle activity during 0.30- and 0.50-m drop vertical-jump landings. RESULTS: During landing from a 0.30-m height, VPAC performance increased external oblique and semitendinosis activity, knee flexion, and knee internal rotation and decreased knee-abduction moment and knee-energy absorption. During the 0.50-m landing, the VPAC increased external oblique and semitendinosis activity, knee flexion, and hip flexion and decreased ankle inversion and hip-energy absorption. CONCLUSIONS: The VPAC performance during landing may protect the anterior cruciate ligament during different landing phases from different heights, creating a protective advantage just before ground contact and after the impact phase. Incorporating VPAC during high injury-risk activities may enhance pelvic stability, improve lower extremity positioning and sensorimotor control, and reduce anterior cruciate ligament injury risk while protecting the lumbar spine.

Dynamic balance as measured by the Y-Balance Test is reduced in individuals with low back pain: A cross-sectional comparative study.

OBJECTIVES: To determine the effects of current LBP (cLBP) and LBP history (hxLBP) on Y-Balance Test (YBT) reach and establish relationships between YBT performance and demographic, behavioral, and disability measures. DESIGN: Cross-sectional comparative study. SETTING: Research laboratory. PARTICIPANTS: Forty-two participants (24 males, 18 females) aged 18-50 years (30.9 ± 8.2 yr) in three groups: cLBP, hxLBP, and healthy controls. INTERVENTIONS: Three YBT trials in anterior (ANT), posterolateral (PL), and posteromedial (PM) directions. MAIN OUTCOME MEASURES: YBT reach (relative to leg length) was measured and compared amongst groups. Pearson correlations were calculated between reach distances and pain, disability, and fear avoidance scores in the cLBP and hxLBP groups and age and activity level in all participants. RESULTS: For PL reach, cLBP (94.7 ± 10.6 cm) and hxLBP (94.2 ± 9.2 cm) groups demonstrated shorter distances versus controls (105.8 ± 6.6 cm). For PM reach, cLBP (100.7 ± 8.4 cm) and hxLBP (102.3 ± 7.6 cm) groups' distances were shorter versus controls (109.3 ± 6.7 cm). No significant difference was found for ANT reach (control = 66.4 ± 7.0 cm; cLBP = 66.2 ± 6.2 cm; hxLBP = 66.4 ± 3.1 cm). No significant correlations were identified. CONCLUSION: YBT performance is reduced in individuals with cLBP and hxLBP in the PL and PM directions but not ANT. The YBT is useful for measuring balance deficits in these populations.

The Effect of Distractive Function on Volitional Preemptive Abdominal Contraction During a Loaded Forward Reach in Normal Subjects.

BACKGROUND: Volitional preemptive abdominal contraction (VPAC) is used to protect the spine and prevent injury. No published studies to data have examined the effect of distraction on VPAC use during function. OBJECTIVE: To examine the effect of an auditory distraction ("Stroop task") on healthy subjects' ability to sustain VPAC by use of the abdominal drawing-in maneuver during loaded forward reach. DESIGN: Within-subjects, repeated-measure cohort design. SETTING: Clinical laboratory setting. PARTICIPANTS: Convenience sample of 42 healthy individuals (ages 20-57 years). METHODS: Transversus abdominis (TrA) thickness was measured with M-mode ultrasound imaging. Each subject performed Stroop versus no Stroop during 4 conditions: (1) without VPAC, quiet standing; (2) with VPAC, quiet standing; (3) without VPAC, forward reach; and (4) with VPAC, forward reach. An investigator blinded to the conditions measured the first 10 subjects to establish intratester reliability of probe/transducer placement and TrA measurement. DATA REDUCTION: TrA thickness (mm) change represented VPAC performance. A single investigator measured onscreen TrA thickness twice at each second from second-6 through -10 on a recorded ultrasound imaging sequence. RESULTS: A 2 (Stroop) × 4 (Activity) repeated-measures analysis of variance found no significant Stroop × Activity interaction [F(3, 93) = 0.345, P = .793] and no main effect for Stroop [F (1,31) = 1.324, P = .259] but found a significant main effect for activity [F (3,93) = 17.729, P < .001]. Tukey post-hoc pairwise comparisons demonstrated significant differences between VPAC versus no-VPAC conditions, except between quiet standing/yes-VPAC and loaded forward reach/no-VPAC conditions (P = .051). The interclass correlation coefficient (3,2) for probe/transducer placement reliability was 0.87, 0.91, 0.92, and 0.93 for conditions 1-4, respectively. The interclass correlation coefficient (3,2) for TrA measurement reliability was 0.96, 0.99, 0.99, and 0.99 for conditions 1-4, respectively. CONCLUSION: A distracting executive function (Stroop task) did not produce a significant negative impact on normal individuals' ability to sustain a VPAC during quiet standing or loaded forward reach activities. LEVEL OF EVIDENCE: II.

Reliability and validation of in vitro lumbar spine height measurements using musculoskeletal ultrasound: A preliminary investigation.

BACKGROUND: Stadiometry measures total trunk height variations but cannot quantify individual spinal segment height changes. Different methods exist to measure both intervertebral disc and lumbar spine height (LSH) variations but they are either limited by radiation exposure or cost. Musculoskeletal ultrasound could be a valuable alternative to measure spinal segmental height changes as a result of intervention. OBJECTIVE: To validate the use of musculoskeletal ultrasound (MSU) and new anatomical landmark references used in assessing inter-mammillary distances (IMD) and LSH changes resulting from lumbar spine traction. METHODS: Two unembalmed cadaveric lumbar spines were extracted to assess (1) the reliability and validity of MSU, as compared to caliper, for measuring in vitro IMD and LSH using alternative anatomical landmarks than previously reported, and (2) the reliability of MSU for measuring in vitro IMD and lumbar spine height changes recorded during standardized mechanical traction up to 1.20 cm. RESULTS: Intra- and inter-rater reliability of musculoskeletal ultrasound for within and between sessions and for all experimental design, Standard Error ranged from 0.01 to 0.02 and from 0.03 to 0.04 cm for IMDs and LSHs, respectively. Root Mean Square Errors ranged from 1.6 to 6.8% and from 1 to 1.1% for IMDs and LSHs, respectively and mean ICC ranged from 0.98 to 1 for LSH. During traction, mean lumbar spine height measurement change using MSU was 1.15 ± 0.03 cm. Bland and Altman plots demonstrated confidence intervals included in the limits of agreement. Nevertheless, there were significant differences (p< 0.001) for both IMD measurements and lumbar spine height between caliper and ultrasound measurements. Musculoskeletal ultrasound overestimated distances of about 5.5 ± 1.5%. CONCLUSIONS: Musculoskeletal ultrasound is reliable and accurate for measuring intersegmental spinal distances and lumbar spine height with an apparent slight overestimation of distances. Based on mean differences, ultrasound technology seems to be valid for measuring lumbar spine height changes and could be suitable for in vivo research.

The Effects of Volitional Preemptive Abdominal Contraction on Postural Control Responses in Healthy Subjects.

OBJECTIVE: To investigate the effect of volitional preemptive abdominal contraction by using an abdominal bracing maneuver (ABM) on postural control responses. DESIGN: A within-subjects, repeated-measure, experimental design. SETTING: Laboratory. PARTICIPANTS: Sixty-five healthy subjects between 18 and 50 years of age. METHODS: Subjects performed ABM alternating with No-ABM during 2 rounds of 2 Neurocom computed dynamic posturography tests: the Motor Control Test (MCT) and conditions 1 (eyes open), 2 (eyes closed), and 5 (eyes closed, sway-referenced support) of the Sensory Organization Test (SOT). MAIN OUTCOME MEASUREMENTS: (1) MCT Response Latency (milliseconds) and Response Scaling (magnitude of active postural correction) and (2) SOT Equilibrium Scores and 2-Dimensional Sway (°/second), and SOT Movement Strategy, which measure postural sway and movement strategies (ankle versus hip strategy), respectively. RESULTS: The use of ABM (versus No-ABM) produced: (1) a small but statistically significant decrease in SOT Equilibrium Score for condition 2 (-1.0%; P = .004); (2) an increase in SOT 2-Dimensional Sway (°/second) during conditions 1 (16.9%; P = .0001) and 2 (15.0%; P = .0001); (3) a small decrease in SOT Movement Strategy scores during condition 1 (-0.5%; P = .001) and condition 2 (-1.0%; P = .017); and (4) a reduction of MCT Response Latency by 3 milliseconds (-2.1%; P = .005) and reduction of Response Scaling by 0.33°/second (-9.2%; P = .001). CONCLUSION: Individuals can incorporate the ABM without substantively altering postural control. Although selected SOT and MCT scores exhibited small decreases in postural response integrity, those outcomes did not reflect functionally meaningful changes. These findings can enhance clinicians' confidence in prescribing the ABM as a means to protectively stabilize the spine and potentially prevent injury in healthy subjects without concern for reducing postural control, especially during more complex postural perturbations that introduce sensory conflict.