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Blackburn JT, Pietrosimone B, Harkey MS, Luc BA, Pamukoff DN. Inter-limb differences in impulsive loading following anterior cruciate ligament reconstruction in females. J Biomech 2016; 49:3017-3021. [DOI: 10.1016/j.jbiomech.2016.07.030] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2015] [Revised: 05/18/2016] [Accepted: 07/26/2016] [Indexed: 11/26/2022]
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Schmidt JD, Guskiewicz KM, Mihalik JP, Blackburn JT, Siegmund GP, Marshall SW. Head Impact Magnitude in American High School Football. Pediatrics 2016; 138:peds.2015-4231. [PMID: 27432843 DOI: 10.1542/peds.2015-4231] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 05/18/2016] [Indexed: 11/24/2022] Open
Abstract
OBJECTIVES To describe determinants of head impact magnitudes between various play aspects in high school football. METHODS Thirty-two high school American football players wore Head Impact Telemetry System instrumented helmets to capture head impact magnitude (linear acceleration, rotational acceleration, and Head Impact Technology severity profile [HITsp]). We captured and analyzed video from 13 games (n = 3888 viewable head impacts) to determine the following play aspects: quarter, impact cause, play type, closing distance, double head impact, player's stance, player's action, direction of gaze, athletic readiness, level of anticipation, player stationary, ball possession, receiving ball, and snapping ball. We conducted random intercepts general linear mixed models to assess the differences in head impact magnitude between play aspects (α = 0.05). RESULTS The following aspects resulted in greater head impact magnitude: impacts during the second quarter (HITsp: P = .03); contact with another player (linear, rotational, HITsp: P < .001); initial head impact when the head is struck twice (linear, rotational, HITsp: P < .001); longer closing distances, especially when combined with a 3-point stance or when being struck in the head (linear: P = .03); the 2-point stance (linear, rotational, HITsp: P < .001); and offensive linemen not snapping the ball compared with those snapping the ball (rotational: P = .02, HITsp: P = .02). CONCLUSIONS Preventing head impacts caused by contact with another player may reduce head impact magnitude in high school football. Rule or coaching changes that reduce collisions after long closing distances, especially when combined with the 3-point stance or when a player is being struck in the head, should be considered.
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Pietrosimone B, Blackburn JT, Golightly YM, Harkey MS, Luc BA, DeFreese JD, Padua DA, Jordan JM, Bennell KL. Certified Athletic Trainers' Knowledge and Perceptions of Posttraumatic Osteoarthritis After Knee Injury. J Athl Train 2016; 52:541-559. [PMID: 27145097 DOI: 10.4085/1062-6050-51.2.13] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
CONTEXT Posttraumatic osteoarthritis (PTOA) is a specific phenotype of osteoarthritis (OA) that commonly develops after acute knee injury, such as anterior cruciate ligament (ACL) or meniscal injury (or both). Athletic trainers (ATs) are well positioned to educate patients and begin PTOA management during rehabilitation of the acute injury, yet it remains unknown if ATs currently prioritize long-term outcomes in patients with knee injury. OBJECTIVE To investigate ATs' knowledge and perceptions of OA and its treatment after ACL injury, ACL reconstruction, or meniscal injury or surgery. DESIGN Cross-sectional study. PATIENTS OR OTHER PARTICIPANTS An online survey was administered to 2000 randomly sampled certified ATs. We assessed participants' perceptions of knee OA, the risk of PTOA after ACL or meniscal injury or surgery, and therapeutic management of knee OA. RESULTS Of the 437 ATs who responded (21.9%), the majority (84.7%) correctly identified the definition of OA, and 60.3% indicated that they were aware of PTOA. A high percentage of ATs selected full meniscectomy (98.9%), meniscal tear (95.4%), ACL injury (90.2%), and partial meniscectomy (90.1%) as injuries that would increase the risk of developing OA. Athletic trainers rated undertaking strategies to prevent OA development in patients after ACL injury or reconstruction (73.8%) or meniscal injury or surgery (74.7%) as extremely or somewhat important. Explaining the risk of OA to patients with an ACL or meniscal injury was considered appropriate by 98.8% and 96.8% of respondents, respectively; yet a lower percentage reported that they actually explained these risks to patients after an ACL (70.8%) or meniscal injury (80.6%). CONCLUSIONS Although 84.7% of ATs correctly identified the definition of OA, a lower percentage (60.3%) indicated awareness of PTOA. These results may reflect the need to guide ATs on how to educate patients regarding the long-term risks of ACL and meniscal injuries and how to implement strategies that may prevent PTOA.
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Harkey M, Luc B, Lepley A, Grindstaff T, Gribble P, Blackburn JT, Spang J, Pietrosimone B. Spinal Reflex Excitability does not Associate with Persistent Muscle Inhibition after Anterior Cruciate Ligament Reconstruction. Med Sci Sports Exerc 2016. [DOI: 10.1249/01.mss.0000486215.01110.f2] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Luc B, Harkey M, Blackburn JT, Kim R, Royal T, Pietrosimone B. Intracortical Inhibition Associates with Quadriceps Voluntary Activation in Individuals with an Anterior Cruciate Ligament Reconstruction. Med Sci Sports Exerc 2016. [DOI: 10.1249/01.mss.0000486213.23981.b0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Pamukoff DN, Pietrosimone B, Ryan ED, Brown LE, Blackburn JT. Whole Body Vibration Improves Early Rate Of Torque Development In Individuals With ACL Reconstruction. Med Sci Sports Exerc 2016. [DOI: 10.1249/01.mss.0000486762.58129.e9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Pietrosimone B, Lepley A, Harkey M, Luc B, Blackburn JT, Gribble P, Spang JT, Sohn D. Quadriceps Strength as a Predictor of Self-Reported Function In Individuals with Anterior Cruciate Ligament Reconstruction. Med Sci Sports Exerc 2016. [DOI: 10.1249/01.mss.0000485907.00329.ff] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Blackburn JT, Pietrosimone BG, Harkey MS, Luc BA, Pamukoff DN. Comparison of three methods for identifying the heelstrike transient during walking gait. Med Eng Phys 2016; 38:581-5. [PMID: 27118622 DOI: 10.1016/j.medengphy.2016.04.008] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2015] [Revised: 02/26/2016] [Accepted: 04/03/2016] [Indexed: 10/21/2022]
Abstract
Impulsive, or high rate, loading contributes to cartilage degradation and is commonly identified via the heelstrike transient (HST) in the vertical ground reaction force (vGRF) during gait. Investigation of the HST may improve our understanding of knee osteoarthritis mechanical pathogenesis. However, the most appropriate method for objectively identifying the HST is unclear. Twenty-eight healthy subjects walked at a self-selected pace while vGRF data were captured. The efficacies of three HST identification methods (Radin, Hunt, and Modified Hunt) were evaluated using vGRF data lowpass filtered at three frequencies (raw/unfiltered, 75Hz, and 50Hz). Both the HST identification method and lowpass filter frequency influenced whether a HST was identified and whether a subject was classified as an "impulsive loader" (i.e. HST identified in 3 of 5 trials). The methods identified different phenomena in the vGRF, with the Radin and Modified Hunt methods identifying the HST 11-16ms following ground contact and the Hunt method identifying the HST 83-122ms following ground contact. Lowpass filtering the vGRF at 75Hz and implementing the Radin method was the most effective approach for identifying the HST. Future longitudinal observations are necessary to determine if specific HST criteria are indicative of knee osteoarthritis development and progression.
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Pamukoff DN, Lewek MD, Blackburn JT. Greater vertical loading rate in obese compared to normal weight young adults. Clin Biomech (Bristol, Avon) 2016; 33:61-65. [PMID: 26952204 DOI: 10.1016/j.clinbiomech.2016.02.007] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/26/2015] [Revised: 01/07/2016] [Accepted: 02/15/2016] [Indexed: 02/07/2023]
Abstract
BACKGROUND Obesity is a risk factor for knee osteoarthritis. Altered gait biomechanics are common in obese individuals, and may contribute to the development of knee osteoarthritis. Research has focused on older obese adults with knee osteoarthritis, and it is unclear if young obese individuals display similar aberrant biomechanics. The purpose of this study was to compare gait biomechanics between normal-weight and obese young adults. METHODS 15 normal-weight (body mass index=21.5 (1.1)) and 15 obese (body mass index=33.5 (3.7)) young adults were recruited and categorized by body mass index. Lower extremity kinematics and kinetics were collected while participants walked at standardized (1m/s) and self-selected speeds. Analysis of variance (group by condition) was used to compare peak vertical ground reaction force, vertical loading rate, peak internal knee extension moment, peak internal knee abduction moment, peak knee flexion angle, and knee flexion excursion between groups. FINDINGS Gait biomechanics did not differ between groups during walking at a self-selected speed. When walking at a standardized speed, obese subjects displayed greater instantaneous vertical loading rates (46.2 vs. 35.0 N/s, P<0.001), and lesser knee flexion excursion (5.5° vs. 7.7°, P=0.04). Instantaneous vertical loading rate was greater during walking at a self-selected speed compared to a standardized speed in the obese (P=0.007) and normal weight groups (P=0.001). INTERPRETATION As greater loading rates are related to cartilage degeneration, these results suggest that obesity may contribute to knee osteoarthritis. Prospective studies are needed to identify the influence of higher loading rates on knee osteoarthritis.
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Luc BA, Harkey MH, Arguelles GD, Blackburn JT, Ryan ED, Pietrosimone B. Measuring voluntary quadriceps activation: Effect of visual feedback and stimulus delivery. J Electromyogr Kinesiol 2016; 26:73-81. [DOI: 10.1016/j.jelekin.2015.10.006] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2015] [Revised: 09/24/2015] [Accepted: 10/14/2015] [Indexed: 11/26/2022] Open
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Pietrosimone B, Blackburn JT, Harkey MS, Luc BA, Hackney AC, Padua DA, Driban JB, Spang JT, Jordan JM. Greater Mechanical Loading During Walking Is Associated With Less Collagen Turnover in Individuals With Anterior Cruciate Ligament Reconstruction. Am J Sports Med 2016; 44:425-32. [PMID: 26684662 DOI: 10.1177/0363546515618380] [Citation(s) in RCA: 73] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
BACKGROUND Individuals who have sustained an anterior cruciate ligament (ACL) injury and undergo ACL reconstruction (ACLR) are at higher risk of developing knee osteoarthritis. It is hypothesized that altered knee loading may influence the underlying joint metabolism and hasten development of posttraumatic knee osteoarthritis. PURPOSE To explore the associations between serum biomarkers of cartilage metabolism and peak vertical ground-reaction force (vGRF) and vGRF loading rate in the injured and uninjured limbs of individuals with ACLR. STUDY DESIGN Descriptive laboratory study. METHODS Patients with a history of a primary unilateral ACLR who had returned to unrestricted physical activity (N = 19) participated in the study. Resting blood was collected from each participant before completing 5 walking gait trials at a self-selected comfortable speed. Peak vGRF was extracted for both limbs during the first 50% of the stance phase of gait, and the linear vGRF loading rate was determined between heel strike and peak vGRF. Sera were assessed for collagen breakdown (collagen type II cleavage product [C2C]) and synthesis (collagen type II C-propeptide [CPII]), as well as aggrecan concentrations, via commercially available specific enzyme-linked immunosorbent assays. Pearson product-moment correlations (r) and Spearman rank-order correlations (ρ) were used to evaluate associations between loading characteristics and biomarkers of cartilage metabolism. RESULTS Lower C2C:CPII ratios were associated with higher peak vGRF in the injured limb (ρ = -0.59, uncorrected P = .007). There were no significant associations between peak vGRF or linear vGRF loading rate and CPII, C2C, or aggrecan serum concentrations. CONCLUSION Lower C2C:CPII ratios were associated with higher peak vGRF in the ACLR limb during gait, suggesting that higher peak loading in the ACLR limb is related to lower type II collagen breakdown relative to type II collagen synthesis. CLINICAL RELEVANCE These data suggest that type II collagen synthesis may be higher relative to the amount of type II collagen breakdown in the ACLR limb with higher lower extremity loading. Future study should determine if metabolic compensations to increase collagen synthesis may affect the risk of developing osteoarthritis after ACLR.
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Schwane BG, Goerger BM, Goto S, Blackburn JT, Aguilar AJ, Padua DA. Trunk and Lower Extremity Kinematics During Stair Descent in Women With or Without Patellofemoral Pain. J Athl Train 2015; 50:704-12. [PMID: 25898109 DOI: 10.4085/1062-6050-49.3.100] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
CONTEXT There is limited evidence indicating the contribution of trunk kinematics to patellofemoral pain (PFP). A better understanding of the interaction between trunk and lower extremity kinematics in this population may provide new avenues for interventions to treat PFP. OBJECTIVE To compare trunk and lower extremity kinematics between participants with PFP and healthy controls during a stair-descent task. DESIGN Cross-sectional study. SETTING Research laboratory. PATIENTS OR OTHER PARTICIPANTS Twenty women with PFP (age = 22.2 ± 3.1 years, height = 164.5 ± 9.2 cm, mass = 63.5 ± 13.6 kg) and 20 healthy women (age = 21.0 ± 2.6 years, height = 164.5 ± 7.1 cm, mass = 63.8 ± 12.7 kg). INTERVENTION(S) Kinematics were recorded as participants performed stair descent at a controlled velocity. MAIN OUTCOME MEASURE(S) Three-dimensional joint displacement of the trunk, hip, and knee during the stance phase of stair descent for the affected leg was measured using a 7-camera infrared optical motion-capture system. Pretest and posttest pain were assessed using a visual analogue scale. Kinematic differences between groups were determined using independent-samples t tests. A 2 × 2 mixed-model analysis of variance (group = PFP, control; time = pretest, posttest) was used to compare knee pain. RESULTS We observed greater knee internal-rotation displacement for the PFP group (12.8° ± 7.2°) as compared with the control group (8.9° ± 4.4°). No other between-groups differences were observed for the trunk, hip, or other knee variables. CONCLUSIONS We observed no difference in trunk kinematics between groups but did note differences in knee internal-rotation displacement. These findings contribute to the current knowledge of altered movement in those with PFP and provide direction for exercise interventions.
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Pamukoff DN, Ryan ED, Troy Blackburn J. The acute effects of local muscle vibration frequency on peak torque, rate of torque development, and EMG activity. J Electromyogr Kinesiol 2014; 24:888-94. [DOI: 10.1016/j.jelekin.2014.07.014] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2013] [Revised: 07/09/2014] [Accepted: 07/28/2014] [Indexed: 11/25/2022] Open
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Pamukoff DN, Bell SE, Ryan ED, Blackburn JT. The Myotonometer: Not a Valid Measurement Tool for Active Hamstring Musculotendinous Stiffness. J Sport Rehabil 2014. [PMID: 25389783 DOI: 10-1123/jsr.2014-0271] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
CONTEXT Hamstring musculotendinous stiffness (MTS) is associated with lower-extremity injury risk (ie, hamstring strain, anterior cruciate ligament injury) and is commonly assessed using the damped oscillatory technique. However, despite a preponderance of studies that measure MTS reliably in laboratory settings, there are no valid clinical measurement tools. A valid clinical measurement technique is needed to assess MTS and permit identification of individuals at heightened risk of injury and track rehabilitation progress. OBJECTIVE To determine the validity and reliability of the Myotonometer for measuring active hamstring MTS. DESIGN Descriptive laboratory study. SETTING Laboratory. PARTICIPANTS 33 healthy participants (15 men, age 21.33 ± 2.94 y, height 172.03 ± 16.36 cm, mass 74.21 ± 16.36 kg). MAIN OUTCOME MEASURES Hamstring MTS was assessed using the damped oscillatory technique and the Myotonometer. Intraclass correlations were used to determine the intrasession, intersession, and interrater reliability of the Myotonometer. Criterion validity was assessed via Pearson product-moment correlation between MTS measures obtained from the Myotonometer and from the damped oscillatory technique. RESULTS The Myotonometer demonstrated good intrasession (ICC3,1 = .807) and interrater reliability (ICC2,k = .830) and moderate intersession reliability (ICC2,k = .693). However, it did not provide a valid measurement of MTS compared with the damped oscillatory technique (r = .346, P = .061). CONCLUSIONS The Myotonometer does not provide a valid measure of active hamstring MTS. Although the Myotonometer does not measure active MTS, it possesses good reliability and portability and could be used clinically to measure tissue compliance, muscle tone, or spasticity associated with multiple musculoskeletal disorders. Future research should focus on portable and clinically applicable tools to measure active hamstring MTS in efforts to prevent and monitor injuries.
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Schmidt JD, Guskiewicz KM, Blackburn JT, Mihalik JP, Siegmund GP, Marshall SW. The influence of cervical muscle characteristics on head impact biomechanics in football. Am J Sports Med 2014; 42:2056-66. [PMID: 24928761 DOI: 10.1177/0363546514536685] [Citation(s) in RCA: 66] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
BACKGROUND An athlete is thought to reduce head acceleration after impact by contracting the cervical musculature, which increases the effective mass of the head. PURPOSE To compare the odds of sustaining higher magnitude in-season head impacts between athletes with higher and lower preseason performance on cervical muscle characteristics. STUDY DESIGN Cohort study; Level of evidence, 2. METHODS Forty-nine high school and collegiate American football players completed a preseason cervical testing protocol that included measures of cervical isometric strength, muscle size, and response to cervical perturbation. Head impact biomechanics were captured for each player using the Head Impact Telemetry System. A median split was used to categorize players as either high or low performers for each of the following outcome measures: isometric strength (peak torque, rate of torque development), muscle size (cross-sectional area), and response to cervical perturbation (stiffness, angular displacement, muscle onset latency). The odds of sustaining moderate and severe head impacts were computed against the reference odds of sustaining mild head impacts across cervical characteristic categorizations. RESULTS Linemen with stronger lateral flexors and composite cervical strength had about 1.75 times' increased odds of sustaining moderate linear head impacts rather than mild impacts compared with weaker linemen. Players who developed extensor torque more quickly had 2 times the increased odds of sustaining severe linear head impacts (odds ratio [OR], 2.10; 95% CI, 1.08-4.05) rather than mild head impacts. However, players with greater cervical stiffness had reduced odds of sustaining both moderate (OR, 0.77; 95% CI, 0.61-0.96) and severe (OR, 0.64; 95% CI, 0.46-0.89) head impacts compared with players with less cervical stiffness. CONCLUSION The study findings showed that greater cervical stiffness and less angular displacement after perturbation reduced the odds of sustaining higher magnitude head impacts; however, the findings did not show that players with stronger and larger neck muscles mitigate head impact severity.
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Oyama S, Yu B, Blackburn JT, Padua DA, Li L, Myers JB. Improper trunk rotation sequence is associated with increased maximal shoulder external rotation angle and shoulder joint force in high school baseball pitchers. Am J Sports Med 2014; 42:2089-94. [PMID: 24944296 DOI: 10.1177/0363546514536871] [Citation(s) in RCA: 90] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
BACKGROUND In a properly coordinated throwing motion, peak pelvic rotation velocity is reached before peak upper torso rotation velocity, so that angular momentum can be transferred effectively from the proximal (pelvis) to distal (upper torso) segment. However, the effects of trunk rotation sequence on pitching biomechanics and performance have not been investigated. PURPOSE The aim of this study was to investigate the effects of trunk rotation sequence on ball speed and on upper extremity biomechanics that are linked to injuries in high school baseball pitchers. The hypothesis was that pitchers with improper trunk rotation sequence would demonstrate lower ball velocity and greater stress to the joint. STUDY DESIGN Descriptive laboratory study. METHODS Three-dimensional pitching kinematics data were captured from 72 high school pitchers. Subjects were considered to have proper or improper trunk rotation sequences when the peak pelvic rotation velocity was reached either before or after the peak upper torso rotation velocity beyond the margin of error (±3.7% of the time from stride-foot contact to ball release). Maximal shoulder external rotation angle, elbow extension angle at ball release, peak shoulder proximal force, shoulder internal rotation moment, and elbow varus moment were compared between groups using independent t tests (α < 0.05). RESULTS Pitchers with improper trunk rotation sequences (n = 33) demonstrated greater maximal shoulder external rotation angle (mean difference, 7.2° ± 2.9°, P = .016) and greater shoulder proximal force (mean difference, 9.2% ± 3.9% body weight, P = .021) compared with those with proper trunk rotation sequences (n = 22). No other variables differed significantly different between groups. CONCLUSION High school baseball pitchers who demonstrated improper trunk rotation sequences demonstrated greater maximal shoulder external rotation angle and shoulder proximal force compared with pitchers with proper trunk rotation sequences. CLINICAL RELEVANCE Improper sequencing of the trunk and torso alter upper extremity joint loading in ways that may influence injury risk. As such, exercises that reinforce the use of a proper trunk rotation sequence during the pitching motion may reduce the stress placed on the structures around the shoulder joint and lead to the prevention of injuries.
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Blackburn JT, Norcross MF, Cannon LN, Zinder SM. Hamstrings stiffness and landing biomechanics linked to anterior cruciate ligament loading. J Athl Train 2014; 48:764-72. [PMID: 24303987 DOI: 10.4085/1062-6050-48.4.01] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
CONTEXT Greater hamstrings stiffness is associated with less anterior tibial translation during controlled perturbations. However, it is unclear how hamstrings stiffness influences anterior cruciate ligament (ACL) loading mechanisms during dynamic tasks. OBJECTIVE To evaluate the influence of hamstrings stiffness on landing biomechanics related to ACL injury. DESIGN Cross-sectional study. SETTING Research laboratory. PATIENTS OR OTHER PARTICIPANTS A total of 36 healthy, physically active volunteers (18 men, 18 women; age = 23 ± 3 years, height = 1.8 ± 0.1 m, mass = 73.1 ± 16.6 kg). INTERVENTION(S) Hamstrings stiffness was quantified via the damped oscillatory technique. Three-dimensional lower extremity kinematics and kinetics were captured during a double-legged jump-landing task via a 3-dimensional motion-capture system interfaced with a force plate. Landing biomechanics were compared between groups displaying high and low hamstrings stiffness via independent-samples t tests. MAIN OUTCOME MEASURE(S) Hamstrings stiffness was normalized to body mass (N/m·kg(-1)). Peak knee-flexion and -valgus angles, vertical and posterior ground reaction forces, anterior tibial shear force, internal knee-extension and -varus moments, and knee-flexion angles at the instants of each peak kinetic variable were identified during the landing task. Forces were normalized to body weight, whereas moments were normalized to the product of weight and height. RESULTS Internal knee-varus moment was 3.6 times smaller in the high-stiffness group (t22 = 2.221, P = .02). A trend in the data also indicated that peak anterior tibial shear force was 1.1 times smaller in the high-stiffness group (t22 = 1.537, P = .07). The high-stiffness group also demonstrated greater knee flexion at the instants of peak anterior tibial shear force and internal knee-extension and -varus moments (t22 range = 1.729-2.224, P < .05). CONCLUSIONS Greater hamstrings stiffness was associated with landing biomechanics consistent with less ACL loading and injury risk. Musculotendinous stiffness is a modifiable characteristic; thus exercises that enhance hamstrings stiffness may be important additions to ACL injury-prevention programs.
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Blackburn JT, Pamukoff DN, Sakr M, Vaughan AJ, Berkoff DJ. Whole body and local muscle vibration reduce artificially induced quadriceps arthrogenic inhibition. Arch Phys Med Rehabil 2014; 95:2021-8. [PMID: 25083559 DOI: 10.1016/j.apmr.2014.07.393] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2014] [Accepted: 07/10/2014] [Indexed: 11/24/2022]
Abstract
OBJECTIVE To evaluate the effects of whole body vibration (WBV) and local muscle vibration (LMV) on quadriceps function after experimental knee effusion (ie, simulated pathology). DESIGN Randomized controlled trial. SETTING Research laboratory. PARTICIPANTS Healthy volunteers (N=43) were randomized to WBV (n=14), LMV (n=16), or control (n=13) groups. INTERVENTIONS Saline was injected into the knee to induce quadriceps arthrogenic muscle inhibition (AMI). All groups then performed isometric squats while being exposed to WBV, LMV, or no vibration (control). MAIN OUTCOME MEASURES Quadriceps function was assessed at baseline, immediately after effusion, and immediately and 5 minutes after each intervention (WBV, LMV, control) via voluntary peak torque (VPT) and the central activation ratio (CAR) during maximal isometric knee extension on a multifunction dynamometer. RESULTS The CAR improved in the WBV (11.4%, P=.021) and LMV (7.3%, P<.001) groups immediately postintervention, but they did not improve in the control group. Similarly, VPT increased by 16.5% (P=.021) in the WBV group and 23% (P=.078) in the LMV group immediately postintervention, but it did not increase in the control group. The magnitudes of improvements in the CAR and VPT did not differ between the WBV and LMV groups. CONCLUSIONS Quadriceps AMI is a common complication following knee pathology that produces quadriceps dysfunction and increases the risk of posttraumatic osteoarthritis. Quadriceps strengthening after knee pathology is often ineffective because of AMI. WBV and LMV improve quadriceps function equivocally after simulated knee pathology, effectively minimizing quadriceps AMI. Therefore, these stimuli may be used to enhance quadriceps strengthening, therefore improving the efficacy of rehabilitation and reducing the risk of osteoarthritis.
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Norcross MF, Shultz SJ, Weinhold PS, Lewek MD, Padua DA, Blackburn JT. The influences of sex and posture on joint energetics during drop landings. Scand J Med Sci Sports 2014; 25:e166-75. [PMID: 24995548 DOI: 10.1111/sms.12263] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/07/2014] [Indexed: 01/14/2023]
Abstract
Previous observations suggest that females utilize a more erect initial landing posture than males with sex differences in landing posture possibly related to sex-specific energy absorption (EA) strategies. However, sex-specific EA strategies have only been observed when accompanied by sex differences in initial landing posture. This study (a) investigated the potential existence of sex-specific EA strategies; and (b) determined the influences of sex and initial landing posture on the biomechanical determinants of EA. The landing biomechanics of 80 subjects were recorded during drop landings in Preferred, Flexed, and Erect conditions. No sex differences in joint EA were identified after controlling for initial landing posture. Males and females exhibited greater ankle EA during Erect vs Flexed landings with this increase driven by 12% greater ankle velocity, but no change in ankle extensor moment. No differences in hip and knee EA were observed between conditions. However, to achieve similar knee EA, subjects used 7% greater mean knee extensor moment but 9% less knee angular velocity during Flexed landings. The results suggest that sex-specific EA strategies do not exist, and that the magnitude of knee joint EA can be maintained by modulating the relative contributions of joint moment and angular velocity to EA.
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Goerger BM, Marshall SW, Beutler AI, Troy Blackburn J, Wilckens JH, Padua DA. Asymmetry Of Joint Coordination And Variability In Those With Prior ACL Injury. Med Sci Sports Exerc 2014. [DOI: 10.1249/01.mss.0000496384.08103.f8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Schmidt JD, Blackburn JT, Siegmund GP, Mihalik JP, Marshall SW, Guskiewicz KM. Stronger Necks Do Not Attenuate Football Head Impacts. Med Sci Sports Exerc 2014. [DOI: 10.1249/01.mss.0000493217.65056.1e] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Pamukoff DN, Ryan ED, Blackburn JT. Acute Effects of Different Local Muscle Vibration Frequencies on Quadriceps Function. Med Sci Sports Exerc 2014. [DOI: 10.1249/01.mss.0000493761.95261.bf] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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98
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Bell DR, Blackburn JT, Hackney AC, Marshall SW, Beutler AI, Padua DA. Jump-landing biomechanics and knee-laxity change across the menstrual cycle in women with anterior cruciate ligament reconstruction. J Athl Train 2014; 49:154-62. [PMID: 24568229 DOI: 10.4085/1062-6050-49.2.01] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
CONTEXT Of the individuals able to return to sport participation after an anterior cruciate ligament(ACL) injury, up to 25% will experience a second ACL injury. This population may be more sensitive to hormonal fluctuations, which may explain this high rate of second injury. OBJECTIVE To examine changes in 3-dimensional hip and knee kinematics and kinetics during a jump landing and to examine knee laxity across the menstrual cycle in women with histories of unilateral noncontact ACL injury. DESIGN Controlled laboratory study. SETTING Laboratory. PATIENTS OR OTHER PARTICIPANTS A total of 20 women (age = 19.6 ± 1.3 years, height = 168.6 ± 5.3 cm, mass = 66.2 ± 9.1 kg) with unilateral, noncontact ACL injuries. INTERVENTION(S) Participants completed a jump-landing task and knee-laxity assessment 3 to 5 days after the onset of menses and within 3 days of a positive ovulation test. MAIN OUTCOME MEASURE(S) Kinematics in the uninjured limb at initial contact with the ground during a jump landing, peak kinematics and kinetics during the loading phase of landing, anterior knee laxity via the KT-1000, peak vertical ground reaction force, and blood hormone concentrations (estradiol-β-17, progesterone, free testosterone). RESULTS At ovulation, estradiol-β-17 (t = -2.9, P = .009), progesterone (t = -3.4, P = .003), and anterior knee laxity (t = -2.3, P = .03) increased, and participants presented with greater knee-valgus moment (Z = -2.6, P = .01) and femoral internal rotation (t = -2.1, P = .047). However, during the menses test session, participants landed harder (greater peak vertical ground reaction force; t = 2.2, P = .04), with the tibia internally rotated at initial contact (t = 2.8, P = .01) and greater hip internal-rotation moment (Z = -2.4, P = .02). No other changes were observed across the menstrual cycle. CONCLUSIONS Knee and hip mechanics in both phases of the menstrual cycle represented a greater potential risk of ACL loading. Observed changes in landing mechanics may explain why the risk of second ACL injury is elevated in this population.
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Goerger BM, Marshall SW, Beutler AI, Blackburn JT, Wilckens JH, Padua DA. Anterior cruciate ligament injury alters preinjury lower extremity biomechanics in the injured and uninjured leg: the JUMP-ACL study. Br J Sports Med 2014; 49:188-95. [DOI: 10.1136/bjsports-2013-092982] [Citation(s) in RCA: 79] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
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Blackburn JT, Norcross MF. The effects of isometric and isotonic training on hamstring stiffness and anterior cruciate ligament loading mechanisms. J Electromyogr Kinesiol 2013; 24:98-103. [PMID: 24268874 DOI: 10.1016/j.jelekin.2013.10.010] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2013] [Accepted: 10/18/2013] [Indexed: 10/26/2022] Open
Abstract
Greater hamstring musculotendinous stiffness is associated with lesser ACL loading mechanisms. Stiffness is enhanced via training, but previous investigations evaluated tendon rather than musculotendinous stiffness, and none involved the hamstrings. We evaluated the effects of isometric and isotonic training on hamstring stiffness and ACL loading mechanisms. Thirty-six healthy volunteers were randomly assigned to isometric, isotonic, and control groups. Isometric and isotonic groups completed 6 weeks of training designed to enhance hamstring stiffness. Stiffness, anterior tibial translation, and landing biomechanics were measured prior to and following the interventions. Hamstring stiffness increased significantly with isometric training (15.7%; p=0.006), but not in the isotonic (13.5%; p=0.089) or control (0.4%; p=0.942) groups. ACL loading mechanisms changed in manners consistent with lesser loading, but these changes were not statistically significant. These findings suggest that isometric training may be an important addition to ACL injury prevention programs. The lack of significant changes in ACL loading mechanisms and effects of isotonic training were likely due to the small sample sizes per group and limited intervention duration. Future research using larger sample sizes and longer interventions is necessary to determine the effects of enhancing hamstring stiffness on ACL loading and injury risk.
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