Promoting community preparedness: lessons learned from the implementation of a chemical disaster tabletop exercise.

Health educators are frequently called on to facilitate community preparedness planning. One planning tool is community-wide tabletop exercises. Tabletop exercises can improve the preparedness of public health system agencies to address disaster by bringing together individuals representing organizations with different roles and perspectives in specific disasters. Thus, they have the opportunity to identify each other's roles, capabilities, and limitations and to problem-solve about how to address the gaps and overlaps in a low-threat collaborative setting. In 2005, the North Carolina Office of Public Health Preparedness and Response developed a series of exercises to test the preparedness for chemical disasters in a metropolitan region in the southeastern United States. A tabletop exercise allowed agency heads to meet in an environment promoting inter- and intraagency public-private coordination and cooperation. The evaluation results reported here suggest ways in which any tabletop exercise can be enhanced through recruitment, planning, and implementation.

Ankle bracing and the neuromuscular factors influencing joint stiffness.

CONTEXT: Health care professionals commonly prescribe external stabilization to decrease the incidence and severity of ankle sprains. The mechanism for this decrease is not clearly understood. Examining the effects of ankle bracing on biomechanical stability and influencing factors may provide important information regarding the neuromuscular effects of bracing. OBJECTIVE: To study the effects of 2 different ankle braces on the neuromuscular factors influencing ankle stiffness. DESIGN: Mixed-model repeated-measures design. SETTING: Research laboratory. PATIENTS OR OTHER PARTICIPANTS: Twenty-eight physically active participants composing 2 groups: 14 with unilateral functional ankle instability (age = 26.19 +/- 6.46 years, height = 166.07 +/- 12.90 cm, mass = 69.90 +/- 13.46 kg) and 14 with bilaterally stable ankles (age = 23.76 +/- 5.82 years, height = 174.00 +/- 11.67 cm, mass = 68.60 +/- 13.12 kg). INTERVENTION(S): Participants were fitted with surface electromyography electrodes over the peroneus longus, peroneus brevis, tibialis anterior, and soleus muscles. Each participant received transient motion oscillations to his or her ankle on a custom-built medial-lateral swaying cradle in each of 3 conditions: no ankle brace (NB), lace-up brace (LU), and semirigid brace (SR). MAIN OUTCOME MEASURE(S): Ankle stiffness as measured by the cradle and preactivation levels (percentage of maximal voluntary isometric contraction) of the 4 test muscles. RESULTS: Stiffness levels increased across brace conditions (NB = 24.79 +/- 6.59 Nm/rad, LU = 28.29 +/- 7.05 Nm/rad, SR = 33.22 +/- 8.78 Nm/rad; F(2,52) = 66.185, P < .001). No differences were found between groups for rotational stiffness (stable = 27.36 +/- 6.17 Nm/rad, unstable = 30.18 +/- 8.21 Nm/rad; F(1,26) = 1.084, P = .307). Preactivation levels did not change for any of the tested muscles with the application of an ankle brace (F(2,52) = 1.326, P = .275). CONCLUSIONS: The increase in ankle rotational stiffness with the addition of an ankle brace and the lack of any demonstrable neuromuscular changes suggested ankle braces passively contributed to the stability of the system.

Validity and reliability of a new in vivo ankle stiffness measurement device.

This investigation was designed to test the validity and reliability of a new measure of inversion/eversion ankle stiffness on a unique medial/lateral swaying cradle device utilizing a test/retest with comparison to a known standard. Ankle stiffness is essential to maintaining joint stability. Most ankle injuries occur via an inversion mechanism. To date, very little information is available regarding stiffness of the evertor muscles in the prevention of excessive inversion joint rotation. Transient oscillation data representing inversion/eversion stiffness was obtained in a bipedal weight-bearing stance with an upright posture. Using commercially available springs with stiffness of 4.80N/cm the measured value recorded by the cradle was 4.87N/cm. Mean active stiffness values of the ankle were 35.70Nm/cm (SD 9.45). The trial-to-trial reliability ICC (2,1) coefficient was 0.96 with an SEM of 2.05Nm/rad, and the day-to-day reliability ICC (2,k) coefficient was 0.93 and an SEM of 3.00Nm/rad. The results demonstrate that inversion/eversion ankle stiffness measures on this device are a valid, repeatable and consistent measure. This is relevant because the ability to accurately quantify inversion/eversion ankle stiffness will improve our understanding of biomechanical stability and factors that influence it. It will also enable identification of ankle injury risk factors that will lead to more efficient rehabilitation programs and injury prevention strategies.

The independent and interactive effects of navicular drop and quadriceps angle on neuromuscular responses to a weight-bearing perturbation.

CONTEXT: Little is known about the effects of static alignment on neuromuscular control of the knee during dynamic motion. OBJECTIVE: To evaluate the isolated and combined effects of quadriceps angle (QA) and navicular drop (ND) on neuromuscular responses to a weight-bearing perturbation. DESIGN: Mixed-model, repeated-measures design. SETTING: Sports medicine and athletic training research laboratory. PATIENTS OR OTHER PARTICIPANTS: Seventy-nine National Collegiate Athletic Association Division I collegiate female athletes, classified with below-average ND and QA (LND-LQA); below-average ND and above-average QA (LND-HQA); above-average ND and below-average QA (HND-LQA); or above-average ND and QA (HND-HQA). INTERVENTION(S): A lower extremity perturbation device produced a forward and either internal or external rotation of the trunk and femur on the weight-bearing tibia to evoke a reflex response. MAIN OUTCOME MEASURE(S): Neuromuscular responses were examined in the quadriceps, hamstrings, and gastrocnemius muscles: preperturbation amplitude 50 milliseconds before the perturbation, reflex time, and postperturbation amplitude 150 milliseconds immediately postperturbation. RESULTS: Navicular drop had the greatest effect on preperturbation amplitude of the lateral hamstrings and postperturbation amplitude of all muscles, with greater activation amplitude noted in subjects in the HND classifications. Quadriceps angle primarily affected reflex time of the quadriceps; in subjects with LQA, reflex time was faster for internal rotation than external rotation perturbations. The interaction between ND and QA had the greatest effect on reflex time of the lateral hamstrings. For internal rotation perturbations, subjects in the LND classifications had faster reflex times in the lateral hamstrings if they had HQA values rather than LQA values. With external rotation perturbations, HND-LQA subjects had slower reflex times than those in all other alignment classifications. CONCLUSIONS: Navicular drop and QA have both independent and interactive effects on neuromuscular responses to a weight-bearing, rotational perturbation. These interactive effects highlight the importance of considering the entire lower extremity posture rather than a single alignment characteristic, given the potential for one alignment factor to compensate for or interact with another.

Quadriceps inhibition after repetitive lumbar extension exercise in persons with a history of low back pain.

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 x 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.

Fatigue, vertical leg stiffness, and stiffness control strategies in males and females.

CONTEXT: Fatigue appears to influence musculoskeletal injury rates during athletic activities, but whether males and females respond differently to fatigue is unknown. OBJECTIVE: To determine the influence of fatigue on vertical leg stiffness (K (VERT)) and muscle activation and joint movement strategies and whether healthy males and females respond similarly to fatigue. DESIGN: Repeated-measures design with all data collected during a single laboratory session. SETTING: Laboratory. PATIENTS OR OTHER PARTICIPANTS: Physically active males (n = 11) and females (n = 10). INTERVENTION(S): Subjects performed hopping protocols at 2 frequencies before and after fatigue, which was induced by repeated squatting at submaximal loads. MAIN OUTCOME MEASURE(S): We measured K (VERT) with a forceplate and peak muscle activity of the quadriceps, hamstrings, gastrocnemius, soleus, and anterior tibialis muscles with surface electromyography. Sagittal-plane kinematics at the knee and ankle were recorded with an electrogoniometer. RESULTS: After fatigue, K (VERT) was unchanged for all subjects. However, both males and females demonstrated reduced peak hamstrings ( P = .002) and anterior tibialis ( P = .001) activation, coupled with increased gastrocnemius ( P = .005) and soleus ( P = .001) peak activity, as well as increased quadriceps-hamstrings ( P = .005) and gastrocnemius/soleus-anterior tibialis coactivation ratios ( P = .03) after fatigue. Overall, females demonstrated greater quadriceps-hamstrings coactivation ratios than males, regardless of the fatigue condition ( P = .026). Only females showed increased knee flexion at initial contact after fatigue during hopping ( P = .03). CONCLUSIONS: Although K (VERT) was unaffected, the peak muscle activation and joint movement strategies used to modulate K (VERT) were affected after fatigue. Once fatigued, both males and females used an ankle-dominant strategy, with greater reliance on the ankle musculature and less on the knee musculature. Also, once fatigued, all subjects used an antagonist inhibition strategy by minimizing antagonist coactivation. Overall, females used a more quadriceps-dominant strategy than males, showing greater quadriceps activity and a larger quadriceps-hamstrings coactivation ratio. Changes in muscle activation and coactivation ratios because of fatigue and sex are suggested to alter knee joint stability and increase anterior cruciate ligament injury risk.

Development and reliability of the ankle instability instrument.

CONTEXT: Functional ankle instability has been defined in a variety of ways. Factors that are frequently used in this definition include a history of a severe ankle sprain, a history of multiple ankle sprains, and a recurrent feeling of instability or "giving way." With all the variations in defining functional ankle instability, it becomes increasingly important to develop a more consistent framework for assessing this instability. OBJECTIVE: To develop a new ankle instability assessment tool, the Ankle Instability Instrument, and evaluate the reliability of this instrument. DESIGN: Test-retest reliability was evaluated using intraclass correlation coefficients (2,1) for each item, each factor, and the total score between test days 1 and 2. Cronbach alpha was calculated to estimate internal consistency of the 12 items. SETTING: Classrooms, offices, athletic fields, and private residences. PATIENTS OR OTHER PARTICIPANTS: College students (29 males, 72 females, age = 20.7 +/- 2.7 years), including 73 (72%) with and 28 (28%) without a history of ankle injury. MAIN OUTCOME MEASURE(S): Subjects were asked to complete the Ankle Instability Instrument on 2 occasions approximately 1 week apart. RESULTS: An exploratory factor analysis of the Instrument produced 3 factors and reduced it from 21 to 12 items. The factors accounted for 32.3%, 10.7%, and 7.0% of the variance, respectively. Together, these factors accounted for 50.0% of the variance in the responses to the Instrument. Test-retest reliability ranged from .70 (SEM = 0.28) to .98 (SEM = 0.06) for the individual items and .95 (SEM = 1.85) for the Instrument overall. The Cronbach alpha coefficient was .92 for factor 1 (severity of initial ankle sprain), .87 for factor 2 (history of ankle instability), .81 for factor 3 (instability during activities of daily life), and .89 for the Instrument overall. CONCLUSIONS: The creation of the Ankle Instability Instrument is a first step in recognizing a more objective way of identifying patients suffering from functional ankle instability. The high reliability we found shows that self-reporting of ankle symptoms is a feasible, appropriate way to obtain information on the presence of instability symptoms. Additionally, through this preliminary study, we found 3 factors that represent unique and important components of functional ankle instability. Clinicians and researchers can, therefore, use these 12 items, either alone or in combination with other information, to determine if functional ankle instability is present.

Reduced quadriceps activation after lumbar paraspinal fatiguing exercise.

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 x 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 = (F(MVIC)/[F(MVIC) + F(Burst)])* 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.

Absolute serum hormone levels predict the magnitude of change in anterior knee laxity across the menstrual cycle.

This study aimed to determine whether absolute sex hormone concentrations predict the magnitude of knee joint laxity changes across the menstrual cycle. Twenty-two females (18-30 years, body mass index

Functional-Performance Deficits in Volunteers With Functional Ankle Instability.

Context: Although functional-performance tests are dynamic measures used to assess general lower body function, studies investigating these tests for ankle instability have yielded conflicting results.Objective: To determine if a relationship exists between a measure of functional ankle instability and deficits in functional performance.Design: A case-control study correlating subject performance on a set of lower extremity functional-performance tests with a measure of ankle instability.Setting: University athletic training research laboratory.Patients or Other Participants: We recruited 60 participants (43 females, 17 males, age = 22.4 +/- 4.9 years, height = 169.9 +/- 9.7 cm, mass = 72.6 +/- 16.3 kg; 42 injured, 18 uninjured) to participate in the study. Six questions were used to determine if functional ankle instability was present in each participant. A point was added for each yes response to produce an index that represents a continuous variable of functional ankle instability.Main Outcome Measure(s): Four unilateral hopping tests were used in this study: figure-of-8 hop, side hop, up-down hop, and single hop. For the first 3 tests, the total time was recorded with a handheld stopwatch to the nearest 0.01 second; for the single hop-for-distance test, the distance was recorded to the nearest 0.01 m. Correlations were computed with the functional ankle instability index and each of the 4 functional-performance tests.Results: No relationship was revealed between the functional ankle instability index and single hop for distance or up-down hop, with r values of -.008 and .245, respectively. A significant relationship was found between the functional ankle instability index and the side hop (r = .35, P

Effects of Pronated and Supinated Foot Postures on Static and Dynamic Postural Stability.

Context: The foot is the most distal segment in the lower extremity chain and represents a relatively small base of support on which the body maintains balance (particularly in single-leg stance). Although it seems reasonable that even minor biomechanical alterations in the support surface may influence postural-control strategies, the implications of a hypermobile or hypomobile foot on balance have received little attention to date.Objective: To determine if supinated and pronated foot types influence measures of static and dynamic balance.Design: Participants were assigned to 1 of 3 groups depending on foot type, as defined by navicular-drop measures: pronated (>/=10 mm), neutral (5-9 mm), or supinated (

Functional Fatigue Decreases 3-Dimensional Multijoint Position Reproduction Acuity in the Overhead-Throwing Athlete.

OBJECTIVE: To determine the effects of functional fatigue on active multijoint position reproduction in overhead-throwing athletes. DESIGN AND SETTING: A standard, repeated-measures, randomized-ordered, counterbalanced, 2-period (crossover) design was used. During the first test session, we randomly assigned subjects to either the nonfatigue or fatigue condition. Subjects underwent pretest measurements and then either a functional fatigue protocol or rest period, followed by posttest measurements. After a recovery period, subjects crossed over to the opposing condition for the second testing session. SUBJECTS: Thirteen overhead-throwing athletes competing in National Collegiate Athletic Association Division I or club baseball, with no history of upper extremity or central nervous system disorders, volunteered for this study. MEASUREMENTS: We measured active multijoint position reproduction accuracy in 3 dimensions using an electromagnetic tracking device. We noted each subject's ability to reproduce 3 positions corresponding with distinct moments of his throwing motion. A variable error score was calculated to compare the locations of the reproduced points with reference to the target point. RESULTS: A significant difference occurred between the pretest and posttest error scores in the fatigue condition. Comparisons between positions indicated that more errors were seen in the arm-cocked position than in the follow-through position under both fatigue and nonfatigue conditions. CONCLUSIONS: Functional fatigue decreased joint position sense acuity in overhead-throwing athletes. Our findings using this novel testing measurement method are in agreement with past research, with one exception. The trend toward higher error scores in the arm-cocked position would appear to contradict findings that sensorimotor system acuity increases toward end ranges of motion.

Knee ligament behavior following a controlled loading protocol does not differ by menstrual cycle day.

BACKGROUND: Females experience a disproportionate number of anterior cruciate ligament injuries compared to males. Increased estradiol concentration has been suggested to alter ligament properties and strength. Determining whether the knee responds differently to an external load at various hormonal levels may be helpful in further explaining the gender disparity. METHODS: Estradiol, progesterone and testosterone were quantified at menses, near ovulation and at the mid-luteal phase. With one knee serving as the control limb and the other as the experimental limb, displacement at 134N and stiffness between 90 and 134N were recorded with a knee ligament arthrometer on both knees before and after a loading protocol. The protocol consisted of three, 3-min, posterior to anterior normalized loads directed to the posterior calf with a ligament testing device. FINDINGS: The loading protocol produced a measurable increase in displacement but not stiffness. Neither displacement nor stiffness measures however were affected by day of the menstrual cycle. No consistent relationships between hormonal concentrations and displacement or stiffness were evident. INTERPRETATION: Following a controlled, static external load, displacement and stiffness were not affected differently by day of the menstrual cycle.

Balance Recovers Within 20 Minutes After Exertion as Measured by the Balance Error Scoring System.

OBJECTIVE: To determine a balance recovery timeline after a functional exertion protocol using the Balance Error Scoring System (BESS). DESIGN AND SETTING: Five subject groups (4 test, 1 control) were tested 3 times during 1 session: once before the exertion protocol (pretest) and twice after the exertion protocol (posttest I and posttest II). Posttest I occurred at staggered intervals of 0, 5, 10, and 15 minutes, depending on experimental group assignment, and posttest II occurred at 20 minutes. SUBJECTS: One hundred subjects (80 test, 20 control) volunteered to participate in this study. None of the subjects had a balance disorder, mild head injury, or lower extremity injury in the 6 months before testing. MEASUREMENTS: We assessed balance using the BESS, assigning a score for each stance-surface condition. RESULTS: We found a significant decrease in BESS performance after the exertion protocol in all test groups, with exertion having the greatest effect on the tandem and single-leg stance conditions. All subjects recovered by posttest II, which was administered 20 minutes after cessation of the exertion protocol. CONCLUSIONS: Athletic trainers need to be aware of the effect of exertion when administering the BESS after physical activity. Athletic trainers can expect the BESS performance of healthy athletes to return to baseline levels within 20 minutes of rest.

Serial administration of clinical concussion assessments and learning effects in healthy young athletes.

OBJECTIVE: To determine if serial administration of the Standardized Assessment of Concussion (SAC) and Balance Error Scoring System (BESS) would elicit a learning effect in young athletes and to determine the intratester reliability of scoring the BESS. DESIGN: A prospective study of 50 healthy young athletes who were assigned to either the control or practice group. All subjects were administered the assessments on 2 occasions, 60 days apart. In addition, subjects in the practice group received serial administration of the assessments on 3 occasions in the week following the initial assessment. SETTING: University Sports Medicine/Athletic Training Research Laboratory. SUBJECTS: Fifty uninjured young athletes between 9 and 14 years of age. MAIN OUTCOME MEASURED: Scores on 2 clinical concussion assessments, the SAC and the BESS. RESULTS: We found a significant learning effect upon serial BESS testing in the practice group. BESS error scores were significantly lower than baseline (15.0 +/- 4.6) on days 5 (11.3 +/- 5.33), 7 (12.4 +/- 6.2), and 60 (12.6 +/- 6.2). We also found a significant learning effect upon the day 60 BESS administration across all subjects. We did not find a practice or learning effect with serial SAC test administration. The intratester reliability of the investigator's ability to score repeated observations of the same BESS test ranged from 0.87 to 0.98. CONCLUSIONS: Our results demonstrated that serial administration of the BESS elicited a learning effect, which was more prominent during the tandem conditions. Clinicians utilizing the BESS as a measure of postural stability should be aware of the potential for improvement with repeated testing. Clinicians should not expect improvement with the SAC, as scores remained relatively stable across all trials.

Performance on the Balance Error Scoring System Decreases After Fatigue.

OBJECTIVE: To determine the immediate effects of a whole-body fatigue protocol on performance of the Balance Error Scoring System (BESS), a postural-stability test commonly used as part of a concussion-assessment battery. DESIGN AND SETTING: Subjects were assigned to a fatigue or control group and were assessed before and immediately after a 20-minute fatigue protocol or rest period. SUBJECTS: Fourteen fatigue subjects and 13 control subjects participated in this study. All subjects were male and free of vestibular disorders, and none had suffered a mild head injury or lower extremity injury in the preceding 6 months, as described through self-report. MEASUREMENTS: We measured performance on the BESS for 9 stance-surface conditions and summed each condition to obtain a total score. Using the Borg scale, we also measured ratings of perceived exertion before, during, and after the fatigue protocol or rest period. RESULTS: We found a significant increase in total errors from pretest to posttest in the fatigue group (14.36 +/- 4.73 versus 16.93 +/- 4.32), a significant decrease in errors in the control group (13.32 +/- 3.77 versus 11.08 +/- 3.88), and a significant difference between groups on the posttest. The rating of perceived exertion scores were significantly different between the fatigue and control groups at the middle (13.29 +/- 1.59 versus 6.23 +/- 0.83) and end (15.86 +/- 2.38 versus 6.15 +/- 0.55) of the fatigue or rest period. CONCLUSIONS: The BESS error scores increased immediately after the fatigue protocol, demonstrating that balance ability diminished. Clinicians who use the BESS as part of their sideline assessment for concussion should not administer the test immediately after a concussion due to the effects of fatigue.

Relationship between two proprioceptive measures and stiffness at the ankle.

Previous research has investigated the role of proprioception and stiffness in the control of joint stability. However, to date, no research has been done on the relationship between proprioception and stiffness. Therefore, the purpose of this study was to determine the relationship between force sense, joint reposition sense, and stiffness at the ankle. A heterogeneous sample was obtained for this study; 20 of the 40 participants had a history of ankle sprains, and 13 of the 20 had been diagnosed by a physician (two mild ankle sprains, seven moderate sprains, four severe sprains). All subjects were asymptomatic and active at the time of the study. Active joint reposition sense was measured using a custom-built ankle goniometer, force sense was measured unilaterally and contralaterally with a load cell, and ankle muscle stiffness was measured via transient oscillation using a custom-built inversion-eversion cradle. We found no significant correlations between stiffness and joint reposition sense, with values of r ranging from 0.01 to 0.21. Significant correlations were found between stiffness and force sense. Specifically, contralateral force sense reproduction was significantly correlated to stiffness in the injured or "involved" ankle (r's ranging from 0.47 to 0.65; P< or =0.008). Whether the decreased ability to appropriately sense force (increased error) sends information to the central nervous system to increase muscle stiffness in response to an unexpected loss of stability, or whether these two phenomena function independently and both change concurrently as a result of injury to the system requires further investigation.

Rate of force application during knee arthrometer testing affects stiffness but not displacement measurements.

STUDY DESIGN: Repeated-measures counterbalanced design. OBJECTIVES: To determine the effect of rate of force application on anterior tibial displacement and anterior tibial stiffness when measured with the KT-2000 knee arthrometer. BACKGROUND: Clinicians and researchers frequently use the KT-2000 to quantify anterior tibial displacement and stiffness. While many factors (ie, tibial rotation, alignment of the arthrometer, etc) have been identified to affect KT-2000 measurements, the effect of the rate of force application has not been studied. METHODS AND MEASURES: Seventeen recreationally active males between the ages of 19 and 36 years (mean age +/- SD, 27.8 +/- 5.3 years) with no previous history of knee injury participated. With the knee in 25 degrees of flexion, the KT-2000 was applied to the participants' anterior tibia. While the distal femur was stabilized, the first author applied a posterior-to-anterior force at a fast and slow rate. Three trials for the slow and fast rates of force application were averaged and used for statistical analysis. Anterior tibial displacement (mm) was measured at 133 N and the related anterior tibial stiffness (N/mm) values were calculated between 89 and 133 N. Separate paired t tests with Bonferroni adjustment were used to determine if differences in displacement and stiffness between rates of force application were present. RESULTS: Stiffness was significantly greater in the slow (mean +/- SD, 58 +/- 22 N/mm) as compared to the fast trials (mean +/- SD, 47 +/- 19 N/mm) (P = .005). Differences in displacement, however, were small and not significant (P = .132) between the slow (mean +/- SD, 3.9 +/- 1.5 mm) and fast (mean +/- SD, 4.0 +/- 1.6 mm) trials. CONCLUSION: The rate of force application affects anterior tibial stiffness but not anterior tibial displacement when measured with the KT-2000. This suggests that to ensure reliable results when using the KT-2000, the rate of force application must be controlled when measuring stiffness between 89 and 133 N, but not when measuring anterior tibial displacement at 133 N.

Reliability and validity of the Biodex system 3 pro isokinetic dynamometer velocity, torque and position measurements.

This study quantitatively assessed the mechanical reliability and validity of position, torque and velocity measurements of the Biodex System 3 isokinetic dynamometer. Trial-to-trial and day-to-day reliability were assessed during three trials on two separate days. To assess instrument validity, measurement of each variable using the Biodex System 3 dynamometer was compared to a criterion measure of position, torque and velocity. Position was assessed at 5 degrees increments across the available range of motion of the dynamometer. Torque measures were assessed isometrically by hanging six different calibrated weights from the lever arm. Velocity was assessed (30 degrees/s to 500 degrees/s) across a 70 degrees arc of motion by manually accelerating the weighted lever arm. With the exception of a systematic decrease in velocity at speeds of 300 degrees/s and higher, the Biodex System 3 performed with acceptable mechanical reliability and validity on all variables tested.

Active knee joint velocity replication measures are stable and accurate in healthy individuals.

The purpose of this study was to determine the stability and accuracy of active knee joint velocity replication methods in healthy subjects. We used a repeated measures design with 14 healthy volunteers. Measures of velocity replication were performed in two ranges of knee joint flexion (0 degrees -30 degrees and 60 degrees -90 degrees ), across four testing velocities (5, 10, 15, and 30 degrees /s) in two movement directions (flexion and extension). Statistical analysis included intraclass correlation coefficients (ICCs; 2, k) and associated standard error of the measures calculated between day 1 and 2. We performed z-tests between all possible combinations of ICC pairs using Fisher's Z transformations to determine if any significant differences existed between observed ICCs. We also calculated correlation ratios (eta2) to explain the source of variability in the calculated ICCs. To assess measurement accuracy, we calculated constant error and absolute error between criterion and replication velocities. Results on ICCs and standard error of the measurements (SEMs) ranged from r = -0.44 +/- 7.00 to 0.88 +/- 0.72 degrees /s. Calculated z-tests indicated six paired ICCs were significantly different ( p < 0.1). In all six pairs, the faster test velocity had a lower ICC magnitude. The eta2 calculations demonstrated that inconsistent performance between day 1 and 2 caused the low ICC magnitudes observed with faster testing velocities. Significantly more absolute error occurred at 30 and 15 degrees /s compared with 5 degrees /s. Significantly less constant error was observed for 30 degrees /s compared with 15 degrees /s. A significant direction by range of motion interaction indicated less constant error for flexion movements in the 60 degrees -90 degrees range of motion (ROM) as compared with extension movements in either ROM. Healthy individuals could actively replicate slower criterion velocities in the mid and end ranges of knee joint motion in both movement directions with an acceptable amount of consistency and accuracy. The data support the use of velocity replication in future investigations on proprioceptive function.