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1.  Different Exercise Training Interventions and Drop-Landing Biomechanics in High School Female Athletes 
Journal of Athletic Training  2013;48(4):450-462.
Anterior cruciate ligament (ACL) injuries are common in female athletes and are related to poor neuromuscular control. Comprehensive neuromuscular training has been shown to improve biomechanics; however, we do not know which component of neuromuscular training is most responsible for the changes.
To assess the efficacy of either a 4-week core stability program or plyometric program in altering lower extremity and trunk biomechanics during a drop vertical jump (DVJ).
Cohort study.
High school athletic fields and motion analysis laboratory.
Patients or Other Participants:
Twenty-three high school female athletes (age = 14.8 ± 0.8 years, height = 1.7 ± 0.07 m, mass = 57.7 ± 8.5 kg).
Independent variables were group (core stability, plyometric, control) and time (pretest, posttest). Participants performed 5 DVJs at pretest and posttest. Intervention participants engaged in a 4-week core stability or plyometric program.
Main Outcome Measure(s):
Dependent variables were 3-dimensional hip, knee, and trunk kinetics and kinematics during the landing phase of a DVJ. We calculated the group means and associated 95% confidence intervals for the first 25% of landing. Cohen d effect sizes with 95% confidence intervals were calculated for all differences.
We found within-group differences for lower extremity biomechanics for both intervention groups (P ≤ .05). The plyometric group decreased the knee-flexion and knee internal-rotation angles and the knee-flexion and knee-abduction moments. The core stability group decreased the knee-flexion and knee internal-rotation angles and the hip-flexion and hip internal-rotation moments. The control group decreased the knee external-rotation moment. All kinetic changes had a strong effect size (Cohen d > 0.80).
Both programs resulted in biomechanical changes, suggesting that both types of exercises are warranted for ACL injury prevention and should be implemented by trained professionals.
PMCID: PMC3718347  PMID: 23768121
anterior cruciate ligament; plyometrics; core stability
Physical inactivity is common in patients with knee osteoarthritis (OA) and has been linked to serious comorbidities such as cardiovascular disease, obesity, and diabetes. The purpose of this study was to examine the association between quadriceps strength and self‐reported physical activity in patients with radiographically confirmed knee OA. Secondarily, the authors' sought to determine if there were differences in quadriceps strength between knee OA patients with low physical activity (LPA) and knee OA patients with higher physical activity (HPA). A tertiary aim of this study was to examine the effect of gender on physical activity and quadriceps strength in patients with knee OA.
Thirty‐six patients with radiographically diagnosed tibiofemoral knee OA participated (15 males, 21 females; age = 59.9±11.6 yrs; height = 171.2±9.2 cm; mass = 84.3±18.9 kg; body mass index (BMI)= 28.9±6.9;Godin Leisure‐Time questionnaire =32.5±25.01). Maximal isometric knee extensor strength was assessed with a Isokinetic dynamometer in 70° of knee flexion. Knee extension torque values were normalized to body mass (Nm*kg−1). Physical activity was evaluated using the Godin Leisure‐Time questionnaire. A Godin‐Leisure time score of 32.5, which was the mean score in the current dataset, was what was used to categorize subjects into LPA and HPA subgroups. Independent t‐tests were used to determine differences in strength between HPA and LPA subgroups, as well as differences in strength and physical activity between genders. Pearson Product Moment and Spearman rank correlations were used to analyze associations between normally and non‐normally distributed variables.
Quadriceps strength was positively correlated with physical activity (r=0.44, r2=0.18, p=0.01). The HPA subgroup had significantly greater quadriceps strength (n=15, 2.01±0.84) compared to the LPA subgroup (n=21, 1.5±0.59, p=0.04). Strength was significantly correlated with physical activity in the HPA subgroup (ρ=0.53, p=0.04), but not in the LPA subgroup (ρ=−0.21,p=0.35). Males reported significantly more physical activity (43.0±28.5 vs 25.1±19.64; p=0.03) and greater strength than females in the entire cohort (2.15±0.73 Nm*kg−1 vs 1.40±0.57 Nm*kg−1; p= 0.002), and the HPA subgroup (2.4±0.65 Nm*kg−1 vs 1.4± 0.68 Nm*kg−1; P=0.02). There were no gender differences for strength in the LPA subgroup.
Higher levels of quadriceps strength correlate with higher physical activity in knee OA patients. The association between higher strength and increased physical activity is stronger in the HPA subgroup compared to the entire sample. Additionally, the HPA subgroup demonstrated greater quadriceps strength compared to the LPA subgroup.
Level of Evidence:
PMCID: PMC4060309  PMID: 24944850
Inactivity; maximum voluntary isometric contraction; physical function; quadriceps
4.  The Bactericidal And Cytotoxic Effects Of Antimicrobial Wound Cleansers 
Journal of Athletic Training  2002;37(1):51-54.
Objective: Wound care is a part of daily activity for many athletic trainers. Knowing which cleansers are effective against the bacteria that most commonly cause infection and whether they are toxic to healthy cells enables athletic trainers to make educated decisions on which cleanser to use. We compared the bactericidal effectiveness and cytotoxicity to human fibroblast cells of 4 cleansers at various dilutions.
Design and Setting: A 4 × 4 factorial design was used for the cytotoxicity testing. The independent variables were type and dilution of cleanser. The dependent variable was cell viability of the human fibroblast cells. We used a 2 × 3 × 4 × 4 factorial design for the bacterial testing. The independent variables were type and dilution of bacteria and type and dilution of cleanser. The dependent variable was the bactericidal action of the cleanser on the bacteria.
Subjects: Human foreskin samples were used to obtain a line of fibroblast cells. Bacterial samples were obtained from an athletic training clinic, isolated from swabs of a whirlpool water supply valve (Pseudomonas aeruginosa) or skin surface (Staphylococcus aureus).
Measurements: We obtained bactericidal measurements by testing isolated Gram-negative (Pseudomonas aeruginosa) and Gram-positive (Staphylococcus aureus) bacteria. Minimum and maximum concentrations were identified according to bactericidal effectiveness. Cytotoxicity measurements were obtained from spectrophotometer readings of a neutral red assay for fibroblast cell viability. Final dilutions tested were determined by pilot testing.
Results: At the 1:5 dilution of product in sterile 0.9% saline, both Cinder Suds and Nitrotan and hydrogen peroxide were different from the control with regard to Pseudomonas aeruginosa. At the 1:10 dilution, both Betadine and hydrogen peroxide were different from the control with regard to Pseudomonas aeruginosa. These 2 cleansers were also different from each other. At the 1:10 dilution, only Betadine was not different from the control for the cytotoxicity testing.
Conclusions: Betadine was both effective against bacteria and not harmful to human fibroblast cells at a 1:10 dilution of a commercially purchased solution.
PMCID: PMC164308  PMID: 12937444
wound cleansers; cytotoxicity; bactericidal; antimicrobial
5.  Lumbopelvic Joint Manipulation and Quadriceps Activation of People With Patellofemoral Pain Syndrome 
Journal of Athletic Training  2012;47(1):24-31.
Quadriceps weakness and inhibition are impairments associated with patellofemoral pain syndrome (PFPS). Lumbopelvic joint manipulation has been shown to improve quadriceps force output and inhibition, but the duration of the effect is unknown.
To determine whether quadriceps strength and activation are increased and maintained for 1 hour after high-grade or low-grade joint mobilization or manipulation applied at the lumbopelvic region in people with PFPS.
Randomized controlled clinical trial.
University laboratory.
Patients or Other Participants:
Forty-eight people with PFPS (age = 24.6±8.9 years, height = 174.3 ± 11.2 cm, mass = 78.4 ± 16.8 kg) participated.
Participants were randomized to 1 of 3 groups: lumbopelvic joint manipulation (grade V), side-lying lumbar midrange flexion and extension passive range of motion (grade II) for 1 minute, or prone extension on the elbows for 3 minutes.
Main Outcome Measure(s):
Quadriceps force and activation were measured using the burst superimposition technique during a seated isometric knee extension task. A 2-way repeated-measures analysis of variance was performed to compare changes in quadriceps force and activation among groups over time (before intervention and at 0, 20, 40, and 60 minutes after intervention).
We found no differences in quadriceps force output (F5,33,101,18 = 0.65, P = .67) or central activation ratio (F4.84,92.03 = 0.38, P= .86) values among groups after intervention. When groups were pooled, we found differences across time for quadriceps force (F2.66,101.18 = 5.03, P = .004) and activation (F2.42,92.03 = 3.85, P = .02). Quadriceps force was not different at 0 minutes after intervention (t40 = 1.68, P = .10), but it decreased at 20 (t40 = 2.16, P = .04), 40 (t40 = 2.87, P = .01) and 60 (t40 = 3.04, P = .004) minutes after intervention. All groups demonstrated decreased quadriceps activation at 0 minutes after intervention (t40 = 4.17, P <.001), but subsequent measures were not different from preintervention levels (t40 range, 1.53–1.83, P >.09).
Interventions directed at the lumbopelvic region did not have immediate effects on quadriceps force output or activation. Muscle fatigue might have contributed to decreased force output and activation over 1 hour of testing.
PMCID: PMC3418111  PMID: 22488227
force output; knee pain; manual therapy; muscle activation
6.  Arthrogenic Muscle Response of the Quadriceps and Hamstrings With Chronic Ankle Instability 
Journal of Athletic Training  2007;42(3):355-360.
Context: An arthrogenic muscle response (AMR) of the soleus and peroneal muscles has been previously demonstrated in individuals with chronic ankle instability (CAI), but the presence of AMR in muscles acting on joints proximal to unstable ankles has not been previously explored.
Objective: To determine if AMR is present in the quadriceps and hamstrings muscles of those with and without unilateral CAI.
Design: Case control.
Setting: University research laboratory.
Patients or Other Participants: Twenty subjects with unilateral CAI (12 males, 8 females: age = 19.9 ± 3.7 years; height = 170.3 ± 15.6 cm; mass = 78.0 ± 23.1 kg) and 21 controls (16 males, 5 females: age = 23.2 ± 5.4 years; height = 173.9 ± 12.7 cm; mass = 87.2 ± 24.6 kg) with no previous ankle injuries.
Main Outcome Measure(s): The central activation ratio (CAR), a measure of motoneuron pool excitability during maximal voluntary isometric contraction, for the hamstrings and quadriceps muscles was measured in both limbs using the superimposed burst technique.
Results: The CAI group demonstrated quadriceps CARs that were significantly larger in their involved limbs (.87 ± .09), as compared with their uninvolved limbs (.84 ± .08), whereas no significant side-to-side difference was seen in the control group (sham involved = .80 ± .11, sham uninvolved = .81 ± .11). When values from both the involved and uninvolved limbs were averaged, the hamstrings CAR was significantly lower for the CAI group (.94 ± .03) than for the control group (.96 ± .03).
Conclusions: Arthrogenic inhibition of the hamstrings muscles bilaterally and facilitation of the quadriceps muscle ipsilateral to the involved limb were noted in subjects with unilateral CAI. Motoneuron pool excitability appears to be altered in muscles that act on joints proximal to the ankle in those with unilateral CAI.
PMCID: PMC1978472  PMID: 18059990
ankle sprain; functional ankle instability; muscle inhibition
7.  Blisters on the Anterior Shin in 3 Research Subjects After a 1-MHz, 1.5-W/cm 2, Continuous Ultrasound Treatment: A Case Series  
Journal of Athletic Training  2007;42(3):425-430.
Context: Clinicians should consider multiple factors when estimating tissue-heating rates.
Objective: To report 3 separate occurrences of blisters during an ultrasound treatment experiment.
Background: While we were conducting a research experiment comparing the measurement capabilities of 2 different intramuscular temperature devices, 3 female participants (age = 26.33 ± 3.79 years, height = 169.34 ± 3.89 cm, mass = 63.39 ± 3.81 kg) out of 16 healthy volunteers (7 men: age = 22.83 ± 1.17 years, height = 170.61 ± 7.77 cm, mass = 74.62 ± 19.24 kg; 9 women: age = 24.22 ± 2.73 years, height = 171.88 ± 6.35 cm, mass = 73.99 ± 18.55 kg) developed blisters on the anterior shin after a 1-MHz, 1.5-W/cm 2 continuous ultrasound treatment delivered to the triceps surae muscle.
Differential Diagnosis: Allergies; chemical reaction with cleaning agents; sunburn; negative interaction between the temperature measurement instruments and the ultrasound field; the ultrasound transducer not being calibrated properly, producing a nonuniform field and creating a hot spot or heating differently when compared with other ultrasound devices; the smaller anatomy of our female subjects; or a confounding interaction among these factors.
Treatment: Participants were given standard minor burn care by a physician.
Uniqueness: (1) The development of blisters on the anterior aspect of the shin as a result of an ultrasound treatment to the posterior aspect of the triceps surae muscle and (2) muscle tissue heating rates ranging from 0.19°C to 1.1°C/min, when ultrasound researchers have suggested tissue heating in the range of 0.3°C/min with these settings.
Conclusions: These adverse events raise important questions regarding treatment application and potential differences in heating and quality control among different ultrasound devices from different manufacturers.
PMCID: PMC1978465  PMID: 18060000
muscle heating; burn; spatial average intensity; beam nonuniformity ratio; therapeutic modalities
8.  Lower Extremity Neuromuscular Control Immediately After Fatiguing Hip-Abduction Exercise 
Journal of Athletic Training  2011;46(6):607-614.
Fatigue of the gluteus medius (GMed) muscle might be associated with decreases in postural control due to insufficient pelvic stabilization. Men and women might have different muscular recruitment patterns in response to GMed fatigue.
To compare postural control and quality of movement between men and women after a fatiguing hip-abduction exercise.
Descriptive laboratory study.
Controlled laboratory.
Patients or Other Participants:
Eighteen men (age = 22 ± 3.64 years, height = 183.37 ± 8.30 cm, mass = 87.02 ±12.53 kg) and 18 women (age = 22 ± 3.14, height = 167.65 ± 5.80 cm, mass = 66.64 ± 10.49 kg) with no history of low back or lower extremity injury participated in our study.
Participants followed a fatiguing protocol that involved a side-lying hip-abduction exercise performed until a 15% shift in electromyographic median frequency of the GMed was reached.
Main Outcome Measure(s):
Baseline and postfatigue measurements of single-leg static balance, dynamic balance, and quality of movement assessed with center-of-pressure measurements, the Star Excursion Balance Test, and lateral step-down test, respectively, were recorded for the dominant lower extremity (as identified by the participant).
We observed no differences in balance deficits between sexes (P > .05); however, we found main effects for time with all of our postfatigue outcome measures (P ≤ .05).
Our findings suggest that postural control and quality of movement were affected negatively after a GMed-fatiguing exercise. At similar levels of local muscle fatigue, men and women had similar measurements of postural control.
PMCID: PMC3418937  PMID: 22488185
gluteus medius muscle; postural control; balance
9.  Quadriceps Function After Exercise in Patients with Anterior Cruciate Ligament–Reconstructed Knees Wearing Knee Braces 
Journal of Athletic Training  2011;46(6):615-620.
Knee braces and neoprene sleeves are commonly worn by people with anterior cruciate ligament reconstructions (ACLRs) during athletic activity. How knee braces and sleeves affect muscle activation in people with ACLRs is unclear.
To determine the effects of knee braces and neoprene knee sleeves on the quadriceps central activation ratio (CAR) before and after aerobic exercise in people with ACLRs.
Crossover study.
Patients or Other Participants:
Fourteen people with a history of ACLR (9 women, 5 men: age = 23.61 ± 4.44 years, height = 174.09 ± 9.82 cm, mass = 75.35 ± 17.48 kg, months since ACLR = 40.62 ± 20.41).
During each of 3 sessions, participants performed a standardized aerobic exercise protocol on a treadmill. The independent variables were condition (brace, sleeve, or control) and time (baseline, pre-exercise with brace, postexercise with brace, postexercise without brace).
Main Outcome Measure(s):
Normalized torque measured during a maximal voluntary isometric contraction (TMVIC) and CAR were measured by a blinded assessor using the superimposed burst technique. The CAR was expressed as a percentage of full muscle activation. The quadriceps CAR and TMVIC were measured 4 times during each session: baseline, pre-exercise with brace, postexercise with brace, and postexercise without brace.
Immediately after the application of the knee brace, TMVIC decreased (P = .01), but no differences between bracing conditions were observed. We noted reduced TMVIC and CAR (P < .001) after exercise, both with and without the brace. No differences were seen between bracing conditions after aerobic exercise.
The decrease in TMVIC immediately after brace application was not accompanied by differences between bracing conditions. Wearing a knee brace or neoprene sleeve did not seem to affect the deterioration of quadriceps function after aerobic exercise.
PMCID: PMC3418938  PMID: 22488186
neuromuscular function; aerobic exercise; central activation ratio
10.  Electrode Type and Placement Configuration for Quadriceps Activation Evaluation 
Journal of Athletic Training  2011;46(6):621-628.
The ability to accurately estimate quadriceps voluntary activation is an important tool for assessing neuromuscular function after a variety of knee injuries. Different techniques have been used to assess quadriceps volitional activation, including various stimulating electrode types and electrode configurations, yet the optimal electrode types and configurations for depolarizing motor units in the attempt to assess muscle activation are unknown.
To determine whether stimulating electrode type and configuration affect quadriceps central activation ratio (CAR) and percentage-of-activation measurements in healthy participants.
Crossover study.
Research laboratory.
Patients and Other Participants:
Twenty participants (13 men, 7 women; age = 26 ± 5.3 years, height = 173.85 ± 7.3 cm, mass = 77.37 ± 16 kg) volunteered.
All participants performed 4 counter-balanced muscle activation tests incorporating 2 different electrode types (self-adhesive, carbon-impregnated) and 2 electrode configurations (vastus, rectus).
Main Outcome Measure(s):
Quadriceps activation was calculated with the CAR and percentage-of-activation equations, which were derived from superimposed burst and resting torque measurements.
No differences were found between conditions for CAR and percentage-of-activation measurements, whereas resting twitch torque was higher in the rectus configuration for both self-adhesive (216 ± 66.98 Nm) and carbon-impregnated (209.1 ± 68.22 Nm) electrodes than in the vastus configuration (209.5 ± 65.5 Nm and 204 ± 62.7 Nm, respectively) for these electrode types (F1,19 = 4.87, P = .04). In addition, resting twitch torque was greater for both electrode configurations with self-adhesive electrodes than with carbon-impregnated electrodes (F1,19 = 9.33, P = .007). Bland-Altman plots revealed acceptable mean differences for agreement between electrode type and configuration for CAR and percentage of activation, but limits of agreement were wide.
Although these electrode configurations and types might not necessarily be able to be used interchangeably, differences in electrode type and configuration did not seem to affect CAR and percentage-of-activation outcome measures.
PMCID: PMC3418939  PMID: 22488187
burst superimposition; interpolated twitch technique; central activation ratio; knee; motor neurons
11.  Peripheral Ankle Cooling and Core Body Temperature 
Journal of Athletic Training  2006;41(2):185-188.
Context: Exposure of the human body to cold is perceived as a stressor and results in a sympathetic response geared at maintaining core temperature. Application of ice to the periphery may lead to a decrease in core temperature, which may counteract the therapeutic effects of cryotherapy.
Objective: To determine if core temperature is lowered by the application of an ice bag to the ankle joint complex.
Design: A within-subjects, repeated-measures design.
Setting: The University of Virginia General Clinical Research Center.
Patients or Other Participants: Twenty-three healthy adults aged 19 to 39 years.
Intervention(s): Subjects were admitted to the hospital on 2 separate occasions. During one admission, subjects had a 20-minute ice treatment applied to their ankles; in the other admission, a bag of marbles was applied. Temperature measurements were recorded at 6 time intervals: baseline (before ice application), immediately after ice application, 10 and 20 minutes after ice application, and 10 and 20 minutes after ice removal.
Main Outcome Measure(s): We measured core temperature and ankle and soleus muscle surface temperatures. A mixed-effects model analysis of variance with repeated measures was used to determine if differences existed in core temperature and ankle and soleus surface temperatures between conditions (cryotherapy and control) and over time.
Results: Core temperature did not change after ice application or ice removal ( P > 0.05). The average core temperatures during the cryotherapy and control conditions were 36.72°C ± 0.42°C and 36.45°C ± 1.23°C, respectively.
Conclusions: A 20-minute cryotherapy treatment applied to the ankle did not alter core temperature.
PMCID: PMC1472654  PMID: 16791304
cryotherapy; cold; ice; temperature
12.  Sex Differences in Valgus Knee Angle During a Single-Leg Drop Jump 
Journal of Athletic Training  2006;41(2):166-171.
Context: Sex differences in lower extremity landing mechanics and muscle activation have been identified as potential causative factors leading to the increased incidence of anterior cruciate ligament injuries in female athletes. Valgus knee alignment places greater strain on the anterior cruciate ligament than a more neutral alignment. Gluteus medius (GM) activation may stabilize the leg and pelvis during landing, limiting valgus knee motion and potentially preventing anterior cruciate ligament injury.
Objective: To determine if frontal-plane knee angle and GM activation differ between the sexes at initial contact and maximal knee flexion during a single-leg drop landing.
Design: Between-groups design.
Setting: Motion analysis laboratory.
Patients or Other Participants: Thirty-two healthy subjects between the ages of 18 and 30 years.
Intervention(s): The independent variables were sex (male or female) and position (initial contact or maximal knee flexion).
Main Outcome Measure(s): Frontal-plane knee angle and GM average root mean square (aRMS) amplitude.
Results: At initial contact, women landed in knee valgus and men landed in knee varus ( P < .025). At maximal knee flexion, both men and women were in a position of knee varus, but the magnitude of varus was less in women than in men ( P < .025). The GM aRMS amplitude was greater at maximal knee flexion than at initial contact ( P < .025); however, male GM aRMS did not differ from female GM aRMS amplitude at either position ( P > .025).
Conclusions: Women tended to land in more knee valgus before and at impact than men. The GM muscle activation did not differ between the sexes and, thus, does not appear to be responsible for the sex differences in knee valgus. The excessive valgus knee angles displayed in women may help to explain the sex disparity in anterior cruciate ligament injury.
PMCID: PMC1472649  PMID: 16791301
biomechanics; kinematics; landing; electromyography; anterior cruciate ligament
13.  Reduced Quadriceps Activation After Lumbar Paraspinal Fatiguing Exercise 
Journal of Athletic Training  2006;41(1):79-86.
Context: Although poor paraspinal muscle endurance has been associated with less quadriceps activation (QA) in persons with a history of low back pain, no authors have addressed the acute neuromuscular response after lumbar paraspinal fatiguing exercise.
Objective: To compare QA after lumbar paraspinal fatiguing exercise in healthy individuals and those with a history of low back pain.
Design: A 2 × 4 repeated-measures, time-series design.
Setting: Exercise and Sport Injury Laboratory.
Patients or Other Participants: Sixteen volunteers participated (9 males, 7 females; 8 controls and 8 with a history of low back pain; age = 24.1 ± 3.1 years, height = 173.4 ± 7.1 cm, mass = 72.4 ± 12.1 kg).
Intervention(s): Subjects performed 3 sets of isometric lumbar paraspinal fatiguing muscle contractions. Exercise sets continued until the desired shift in lumbar paraspinal electromyographic median power frequency was observed. Baseline QA was compared with QA after each exercise set.
Main Outcome Measure(s): An electric burst was superimposed while subjects performed a maximal quadriceps contraction. We used the central activation ratio to calculate QA = (FMVIC/[FMVIC + FBurst])* 100, where F = force and MVIC = maximal voluntary isometric contractions. Quadriceps electromyographic activity was collected at the same time as QA measurements to permit calculation of median frequency during MVIC.
Results: Average QA decreased from baseline (87.4% ± 8.2%) after the first (84.5% ± 10.5%), second (81.4% ± 11.0%), and third (78.2% ± 12.7%) fatiguing exercise sets. On average, the group with a history of low back pain showed significantly more QA than controls. No significant change in quadriceps median frequency was noted during the quadriceps MVICs.
Conclusions: The quadriceps muscle group was inhibited after lumbar paraspinal fatiguing exercise in the absence of quadriceps fatigue. This effect may be different for people with a history of low back pain compared with healthy controls.
PMCID: PMC1421484  PMID: 16619099
superimposed burst technique; quadriceps muscle inhibition; low back pain
14.  Quadriceps Inhibition After Repetitive Lumbar Extension Exercise in Persons With a History of Low Back Pain 
Journal of Athletic Training  2006;41(3):264-269.
Context: A neuromuscular relationship exists between the lumbar extensor and quadriceps muscles during fatiguing exercise. However, this relationship may be different for persons with low back pain (LBP).
Objective: To compare quadriceps inhibition after isometric, fatiguing lumbar extension exercise between persons with a history of LBP and control subjects.
Design: A 2 × 3 factorial, repeated-measures, time-series design with independent variables of group (persons with a history of LBP, controls) and time (baseline, postexercise set 1, postexercise set 2).
Setting: University research laboratory.
Patients or Other Participants: Twenty-five subjects with a history of LBP were matched by sex, height, and mass to 25 healthy control subjects.
Intervention(s): Electromyography median frequency indexed lumbar paraspinal muscular fatigue while subjects performed 2 sets of isometric lumbar extension exercise. Subjects exercised until a 15% downward shift in median frequency for the first set and a 25% shift for the second set were demonstrated.
Main Outcome Measure(s): Knee extension force was measured while subjects performed an isometric maximal quadriceps contraction. During this maximal effort, a percutaneous electric stimulus was applied to the quadriceps, causing a transient, supramaximal increase in force output. We used the ratio between the 2 forces to estimate quadriceps inhibition. Quadriceps electromyographic activity was recorded during the maximal contractions to compare median frequencies over time.
Results: Both groups exhibited significantly increased quadriceps inhibition after the first (12.6% ± 10.0%, P < .001) and second (15.2% ± 9.7%, P < .001) exercise sets compared with baseline (9.6% ± 9.3%). However, quadriceps inhibition was not different between groups.
Conclusions: Persons with a history of LBP do not appear to be any more or less vulnerable to quadriceps inhibition after fatiguing lumbar extension exercise.
PMCID: PMC1569566  PMID: 17043693
superimposed burst technique; neuromuscular activity; knee
15.  A Functional Fatiguing Protocol and Deceleration Time of the Shoulder From an Internal Rotation Perturbation 
Journal of Athletic Training  2006;41(3):275-279.
Context: Muscular fatigue impedes sensorimotor function and may increase the risk of shoulder injury during activity. The effects of fatigue on the sensorimotor system of the shoulder have been studied with various results. Deceleration times have been used to study neuromuscular control of the shoulder; however, no studies involving the effects of fatigue on deceleration times have been reported.
Objective: To compare shoulder deceleration times after a shoulder internal rotation perturbation before and after a repetitive throwing exercise protocol.
Design: A 2 × 2 repeated-measures design.
Setting: Exercise and sport injury laboratory.
Patients or Other Participants: Twenty healthy, recreationally active men (age = 24.76 ± 4.03 years, height = 178.41 ± 8.36 cm, mass = 80.16 ± 15.20 kg) volunteered to participate in the study. To ensure familiarity with the overhead motion, all subjects chosen had previously participated in an overhead throwing sport.
Intervention(s): The independent variables were time (preintervention and postintervention) and session (experimental and control). The intervention consisted of continuous overhead throwing. The subjects were considered fatigued when a 10% decrease in velocity was noted on 3 consecutive pitches.
Main Outcome Measure(s): Time necessary to decelerate from an internal rotation perturbation.
Results: Deceleration time was significantly increased by the fatiguing intervention ( P = .001).
Conclusions: The decreased ability to decelerate may be an adaptive response by the subjects to dissipate a lower percentage of force per second.
PMCID: PMC1569554  PMID: 17043695
shoulder fatigue; shoulder neuromuscular control; throwing fatigue protocol
16.  Neuromuscular Changes After Aerobic Exercise in People with Anterior Cruciate Ligament– Reconstructed Knees 
Journal of Athletic Training  2011;46(5):476-483.
Anterior cruciate ligament (ACL) reconstructions are common, especially in young, active people. The lower extremity neuromuscular adaptations seen after aerobic exercise provide information about how previously injured patients perform and highlight deficits and, hence, areas for focused treatment. Little information is available about neuromuscular performance after aerobic exercise in people with ACL reconstructions.
To compare dynamic balance, gluteus medius muscle activation, vertical jump height, and hip muscle strength after aerobic exercise in people with ACL-reconstructed knees.
Case-control study.
Research laboratory.
Patients or Other Participants:
Of 34 recreationally active volunteers, 17 had a unilateral primary ACL reconstruction at least 2 years earlier and 17 were matched controls.
All participants performed 20 minutes of aerobic exercise on a treadmill.
Main Outcome Measure(s):
We recorded dynamic, single-legged balance electromyographic gluteus medius muscle activation, single-legged vertical jump height, and maximum isometric strength for hip abduction, extension, and external rotation preexercise and postexercise.
Participants with ACL reconstructions exhibited shorter reach distances during dynamic balance tasks, indicating poorer dynamic balance, and less gluteus medius muscle electromyographic activation. Reductions in hip abduction and extension strength after exercise were noted in all participants; however, those with ACL reconstructions displayed greater hip extensor strength loss after aerobic exercise than did the control group.
Neuromuscular changes after aerobic exercise exist in both patients with ACL reconstructions and controls. The former group may experience greater deficits in hip extensor strength after aerobic exercise. Reduced reach distances in people with ACL reconstructions may represent a protective mechanism against excessive tibiofemoral rotation during dynamic balance. Clinicians should identify weaknesses in the resting state and after aerobic exercise in recreationally active patients and those with ACL reconstructions.
PMCID: PMC3418953  PMID: 22488134
skeletal muscle adaptations; fatigue; strength; isometric activity; isokinetic activity
17.  The Hoffmann Reflex: Methodologic Considerations and Applications for Use in Sports Medicine and Athletic Training Research 
Journal of Athletic Training  2004;39(3):268-277.
To discuss the proper methods used to elicit the Hoffmann reflex (H-reflex) and to present different situations in which this tool can be used in sports medicine research.
Data Sources:
We searched MEDLINE and SPORT Discus from 1960 to 2004 using the key words Hoffmann reflex, H-reflex, and methodology. The remaining citations were collected from references of similar papers.
Data Synthesis:
Numerous authors have used the H-reflex as a tool to examine neurologic conditions. However, few have used the H-reflex to examine neuromuscular impairments after sport injuries. Several studies were available describing the appropriate methods to elicit the H-reflex and examining the reliability of this measurement in different muscles.
The H-reflex is a valuable tool to evaluate neurologic function in various populations. However, because of the sensitivity of this measurement to extraneous factors, care must be taken when eliciting the H-reflex. We discuss recommendations on how to elicit the H-reflex and how to appropriately present methods in a manuscript.
PMCID: PMC522151  PMID: 16558683
H-reflex; neuromuscular system; motor neuron; injury; muscle
18.  The Spectral Qualities of Postural Control are Unaffected by 4 Days of Ankle-Brace Application 
Journal of Athletic Training  2002;37(3):269-274.
Objective: To determine if the spectral qualities of medial-lateral (ML) and anterior-posterior (AP) center of pressure during a 1-legged stance are affected by 4 days of ankle-brace application.
Design and Setting: The study, which consisted of a pretest-posttest randomized group design, took place in the Sports Injury Research Laboratory at Indiana State University.
Subjects: Twenty-eight Indiana State University students, who had not suffered from any ankle injuries within the past 2 years and were free of any neurologic or vestibular disorders, participated in the study.
Measurements: The effects of 3 independent variables on mean frequency amplitude for both ML and AP center of pressure were examined: (1) treatment (brace, control), (2) frequency bin (0%–20%, 20%–40%, 40%–60%, 60%–80%, and 80%–100% of area), and (3) time (pretest, immediately after brace application, and after 1, 2, 3, or 4 days of brace wear).
Results: We detected no difference (P > .05) for the ML or AP mean frequency when comparing the brace and control groups.
Conclusions: Application of an ankle brace may not require modifications in the postural-control strategies during a 1-legged stance in subjects with healthy ankles.
PMCID: PMC164355  PMID: 12937584
fast Fourier transformation; somatosensation; frequency analysis; balance
19.  Efficacy of Prophylactic Ankle Support: An Experimental Perspective 
Journal of Athletic Training  2002;37(4):446-457.
Objective: To provide a comprehensive review of the literature regarding the role of external ankle support on joint kinematics, joint kinetics, sensorimotor function, and functional performance.
Data Sources: We searched MEDLINE and SPORT Discus databases from 1960–2001 for the key words ankle bracing, ankle support, ankle taping, and ankle prophylaxes. We also used personal libraries based on our own research to complement the existing literature.
Data Synthesis: The effects of external ankle support have been studied on a plethora of dependent measures. Here, we specifically discuss the role of external ankle support on joint kinematics, joint kinetics, sensorimotor function, and functional performance and present a general consensus regarding the overall effects of these prophylactic devices.
Conclusions/Recommendations: The effects of ankle support on joint kinematics during static joint assessment and on traditional functional-performance measures (ie, agility, sprint speed, vertical jump height) are well understood. However, the potential effects of ankle support on joint kinetics, joint kinematics during dynamic activity (eg, a cutting maneuver), and various sensorimotor measures are not well known. Future research investigating the role of external ankle bracing needs to focus on these areas.
PMCID: PMC164376  PMID: 12937566
ankle bracing; joint mechanics; sensorimotor function; functional performance
20.  Cryotherapy and Transcutaneous Electric Neuromuscular Stimulation Decrease Arthrogenic Muscle Inhibition of the Vastus Medialis After Knee Joint Effusion 
Journal of Athletic Training  2002;37(1):25-31.
Objective: Arthrogenic muscle inhibition (AMI) is a presynaptic, ongoing reflex inhibition of joint musculature after distension or damage to the joint. The extent to which therapeutic interventions affect AMI is unknown. The purpose of this study was to verify that the vastus medialis (VM) is inhibited using the knee joint effusion model and to investigate the effects of cryotherapy and transcutaneous electric nerve stimulation (TENS) on AMI using this model.
Design and Setting: A 3 × 6 analysis of variance was used to compare Hoffmann-reflex data for treatment groups (cryotherapy, TENS, and control) across time (preinjection, postinjection, and 15, 30, 45, and 60 minutes after injection).
Subjects: Thirty neurologically sound volunteers (age = 21.8 ± 2.4 years; height = 175.6 ± 9.6 cm; mass = 71.5 ± 13.3 kg) participated in this study.
Measurements: Hoffmann-reflex measurements were collected using a percutaneous stimulus to the femoral nerve and surface electromyography of the VM.
Results: Hoffmann-reflex measurements from the cryotherapy and TENS groups were greater than measurements from the control group at 15 and 30 minutes after injection. Measurements from the cryotherapy group were greater than for the TENS group, and measurements for the TENS group were greater than those for the control group at 45 minutes. At 60 minutes, the cryotherapy group measurements were greater than the TENS and control group measures. Measurements at 15, 30, 45, and 60 minutes after injection were reduced compared with the preinjection and postinjection measurements in the control group. Measurements in the cryotherapy group at 30, 45, and 60 minutes were greater than the preinjection, postinjection, and 15-minute data. No differences between time intervals existed in the TENS group.
Conclusions: Artificial knee joint effusion results in VM inhibition. Cryotherapy and TENS both disinhibit the quadriceps after knee joint effusion, and cryotherapy further facilitates the quadriceps motoneuron pool. Cryotherapy treatment resulted in facilitation of the VM motoneuron pool during the post-treatment phase. The TENS treatment failed to disinhibit the VM motoneuron pool by 30 minutes postinjection.
PMCID: PMC164304  PMID: 12937440
Hoffmann reflex; joint effusion; neuromuscular
21.  Scholarly Productivity of Athletic Training Faculty Members 
Journal of Athletic Training  2001;36(2):156-159.
To compare the scholarly productivity index (SPI) among the levels of academic appointment, degree type, and percentage of academic appointment of athletic training faculty members.
Design and Setting:
We used a 5 × 6 × 4 factorial design for this study. A survey instrument was used to determine the number of publications and the number of years in their current appointment.
Subjects were faculty members in Commission on Accreditation of Allied Health Education Programs-accredited athletic training education programs.
The SPI was calculated by dividing the total number of publications (peer-reviewed and non–peer-reviewed journal articles, peer-reviewed abstracts, books written or edited, book chapters, platform presentations, published book reviews, and external funding) by the number of years in the productivity period.
The SPIs were different for the levels of academic rank. Full professors had a higher SPI than all other groups (Tukey honestly significant difference, P ≤ .05). Associate professors had higher SPIs than instructors or lecturers and clinical specialists, equivalent SPIs to assistant professors, and lower SPIs than full professors. Assistant professors had lower SPIs than full professors but were equivalent to all other groups. There were no differences among the levels of degree type or percentage of academic appointment.
The scholarly productivity of athletic training educators was affected by their academic rank but not by the percentage of time they were assigned to academics or their academic degree type.
PMCID: PMC155527  PMID: 12937457
scholarly productivity index; athletic training education; tenure; promotion
22.  An Investigation of Undergraduate Athletic Training Students' Learning Styles and Program Admission Success 
Journal of Athletic Training  2001;36(2):130-135.
The phrase learning style refers to the method one uses to obtain and use information to learn. Personal learning styles can be assessed by specifically designed inventories. We conducted this study to determine if undergraduate athletic training students possess a dominant learning style, according to the Kolb Learning Style Inventory IIA (KLSI IIA), the newest version of the Kolb Learning Style Inventory (KLSI), and whether this style is related to education program admission success.
Design and Setting:
A 1 × 4 factorial design was used. The independent variable was learning style type with 4 levels (converger, diverger, assimilator, or accommodator). The dependent variable was successful versus unsuccessful admission into selected programs.
Forty undergraduate students (21 men, 19 women) from 3 institutions (mean ± SD age, 20.7 ± 1.7 years; mean ± SD grade point average, 3.26 ± 0.43) participated in this study. No subjects had previously taken the KLSI IIA, and none had a diagnosed learning disability.
The KLSI IIA was administered to the participants at their respective institutions. We used 2 separate χ2 analyses to determine if the observed distribution of learning styles differed from the expected distribution. Additionally, a Mann-Whitney U test was performed to determine if the learning style distributions of those subjects who were successfully admitted to the selected programs differed from those who were not.
No significant differences existed between the observed distribution and the expected distribution for those admitted and those not admitted (χ23 = 3.8, P = .28; and χ23 = 3.1, P = .4, respectively). Also, no significant differences existed between the learning style distributions of the groups when compared with each other (Mann-Whitney U = 158, P = .5).
Learning styles can be easily identified through the use of the KLSI IIA. We found no dominant learning style among undergraduate athletic training students and no particular learning style led to program admission.
PMCID: PMC155522  PMID: 12937452
inventory; athletic training education program
23.  Therapeutic Magnets Do Not Affect Tissue Temperatures 
Journal of Athletic Training  2001;36(1):27-31.
Manufacturers of commercially available “therapeutic” magnets claim that these magnets cause physiologic thermal effects that promote tissue healing. We conducted this study to determine if skin or intramuscular temperatures differed among magnet, sham, and control treatments during 60 minutes of application to the quadriceps muscle.
Design and Setting:
A 3 × 3 mixed-model, factorial design with repeated measures on both independent variables was used. The first independent variable, application duration, had 3 random levels (20, 40, and 60 minutes). The second independent variable, treatment, had 3 fixed levels (magnet, sham, and control). The dependent variable was tissue temperature (°C). Measurement depth served as a control variable, with 2 levels: skin and 1 cm below the fat layer. Data were collected in a thermoneutral laboratory setting and analyzed using a repeated-measures analysis of variance.
The study included 13 healthy student volunteers (8 men, 5 women; age, 20.5 ± 0.9 years; height, 176.8 ± 10.4 cm; weight, 73.8 ± 11.8 kg; anterior thigh skinfold thickness, 16.9 ± 6.5 mm).
Temperatures were measured at 30-second intervals using surface and implantable thermocouples. Temperature data at 20, 40, and 60 minutes were used for analysis. Each subject received all 3 treatments on different days.
Neither skin nor intramuscular temperatures were different across the 3 treatments at any time. For both skin and intramuscular temperatures, a statistically significant but not clinically meaningful temperature increase (less than 1°C), was observed over time within treatments, but this increase was similar in all treatment groups.
No meaningful thermal effect was observed with any treatment over time, and treatments did not differ from each other. We conclude that flexible therapeutic magnets were not effective for increasing skin or deep temperatures, contradicting one of the fundamental claims made by magnet distributors.
PMCID: PMC155398  PMID: 12937511
intramuscular temperature; Hall voltage; biomagnetism
24.  Motor-Neuron Pool Excitability of the Lower Leg Muscles After Acute Lateral Ankle Sprain 
Journal of Athletic Training  2011;46(3):263-269.
Neuromuscular deficits in leg muscles that are associated with arthrogenic muscle inhibition have been reported in people with chronic ankle instability, yet whether these neuromuscular alterations are present in individuals with acute sprains is unknown.
To compare the effect of acute lateral ankle sprain on the motor-neuron pool excitability (MNPE) of injured leg muscles with that of uninjured contralateral leg muscles and the leg muscles of healthy controls.
Case-control study.
Patients or Other Participants:
Ten individuals with acute ankle sprains (6 females, 4 males; age = 19.2 ± 3.8 years, height = 169.4 ± 8.5 cm, mass = 66.3 ±11.6 kg) and 10 healthy individuals (6 females, 4 males; age = 20.6 ± 4.0 years, height = 169.9 ± 10.6 cm, mass = 66.3 ± 10.2 kg) participated.
The independent variables were group (acute ankle sprain, healthy) and limb (injured, uninjured). Separate dependent t tests were used to determine differences in MNPE between legs.
Main Outcome Measure(s):
The MNPE of the soleus, fibularis longus, and tibialis anterior was measured by the maximal Hoffmann reflex (Hmax) and maximal muscle response (Mmax) and was then normalized using the Hmax:Mmax ratio.
The soleus MNPE in the ankle-sprain group was higher in the injured limb (Hmax:Mmax = 0.63; 95% confidence interval [CI], 0.46, 0.80) than in the uninjured limb (Hmax:Mmax = 0.47; 95% CI, 0.08, 0.93) (t6 = 3.62, P = .01). In the acute ankle-sprain group, tibialis anterior MNPE tended to be lower in the injured ankle (Hmax:Mmax = 0.06; 95% CI, 0.01, 0.10) than in the uninjured ankle (Hmax:Mmax = 0.22; 95% CI, 0.09, 0.35), but this finding was not different (t9 = −2.01, P = .07). No differences were detected between injured (0.22; 95% CI, 0.14, 0.29) and uninjured (0.25; 95% CI, 0.12, 0.38) ankles for the fibularis longus in the ankle-sprain group (t9 = −0.739, P = .48). We found no side-to-side differences in any muscle among the healthy group.
Facilitated MNPE was present in the involved soleus muscle of patients with acute ankle sprains, but no differences were found in the fibularis longus or tibialis anterior muscles.
PMCID: PMC3419554  PMID: 21669095
arthrogenic muscle response; Hoffmann reflex; fibularis longus; soleus; tibialis anterior
25.  The Effects of Selected Ankle Appliances on Postural Control 
Journal of Athletic Training  1997;32(4):300-303.
Although ankle braces supposedly protect the ankle by providing mechanical support of the joint and enhancing proprioceptive input, their proprioceptive effects are unclear. Measuring the center of pressure during posture provides a reasonably well-controlled evaluation of proprioceptive input at the ankle. We, therefore, compared the changes in the center of pressure resulting from wearing ankle braces and wearing no brace (control).
Design and Setting:
Center-of-pressure variables were measured during a one-legged modified Romberg test with six variations. The six test conditions systematically altered the three sensory modalities that control posture: visual input, vestibular input, and proprioceptive input. Subjects performed three 16-second trials of each Romberg variation for each brace condition.
Twenty-four male volunteers (age = 18 to 26 yr) with no history of ankle injuries in the past 5 years and no difficulty with balance.
Center of pressure, transmitted through the bottom of the foot, was monitored during each trial and transformed into total distance traveled, anterior-posterior (AP) position, and medial-lateral (ML) position.
Average AP and ML center-of-pressure positions were increased only during brace wearing when all sensory modalities were functioning normally (control condition). Total center-of-pressure distance was the same for all three brace conditions.
Our results do not support or refute the concept that bracing enhances proprioception. The fact that subjects relocated their center of pressure only during the control condition is perplexing. If braces were to enhance proprioception, one would expect to see lower average ML and average AP center-of-pressure values when comparing the braced with the unbraced conditions. Alternatively, the relocated position may represent a more stable position resulting from enhanced proprioception.
PMCID: PMC1320344  PMID: 16558462
ankle braces; balance; center of pressure; proprioception

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