Biomedical subjects

Brent L Arnold

Publications and source records attributed to Brent L Arnold.

13 recordsLinked to original sources

PubMed2006

Contralateral force sense deficits are related to the presence of functional ankle instability.

Residual symptoms that often follow lateral ankle sprains can lead to functional ankle instability. Proprioceptive deficits have been identified as one factor that may contribute to the presence of functional ankle instability. Sixty participants were recruited to participate in the study. Seven questions were used to determine the presence of functional ankle instability in each participant. A point was added for each "yes" response to produce an index that represents an interval data scale of functional ankle instability. Contralateral force sense and active joint reposition sense were measured in all participants. Pearson product moment correlations were calculated to determine the relationship between functional ankle instability and force sense and active joint reposition sense. We found a significant relationship with force sense and functional ankle instability. Specifically, force sense variable error at both test forces (10 and 30% of maximal voluntary isometric contraction) were positively correlated to the presence of functional ankle instability, r=0.26; p<or=0.05 and r=0.25; p<or=0.05, respectively. All other force sense correlations were not statistically significant. No significant correlations were identified between active joint reposition sense and functional ankle instability. This study indicates that participants with functional ankle instability have deficits in low load force sense, but not active joint reposition sense.

Adolescent↗

PubMed2005

Gender differences in leg stiffness and stiffness recruitment strategy during two-legged hopping.

The authors compared leg stiffness (K(VERT)), muscle activation, and joint movement patterns between 11 men and 10 women during hopping. Physically active and healthy men and women performed continuous 2-legged hopping at their preferred rate and at 3.0 Hz. Compared with men, women demonstrated decreased K(VERT); however, after the authors normalized for body mass, gender differences in K(VERT) were eliminated. In comparison with men, women also demonstrated increased quadriceps and soleus activity, as well as greater quadriceps-to-hamstrings coactivation ratios. There were no significant gender differences for joint movement patterns (p>.05). The relationship between the observed gender differences in muscle recruitment and the increased risk of anterior cruciate ligament injury in women requires further study.

Adult↗

PubMed2005

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 </= .01) and the figure-of-8 hop (r = .31, P </= .02).Conclusions: A positive relationship existed between functional ankle instability and performance deficits on the side hop and figure-of-8 hop. Conversely, a relationship did not exist between functional ankle instability and frontal-plane functional-performance activities.

Journal Article↗

PubMed2004

Bracing and rehabilitation--what's new.

Based on the recent evidence, ankle bracing and taping do appear to have positive effects on ankle support. For example, both bracing and taping restrict inversion range of motion, with tape and stirrup-style braces providing the best support. Although exercise reduces this restriction, the range remains consistent with levels considered to be within the normal range. Ankle supports also appear to improve the strength of the muscular response to perturbation, potentially providing a stronger muscular contraction. In contrast, ankle supports fail to improve the neuromuscular response time to unexpected perturbations. Thus, it appears that the stronger response may occur too slowly to protect the joint. This slowness of the neuromuscular response, however, may be offset by the support's ability to slow the inversion motion. The slowing of inversion appears to allow the neuromuscular system to respond at or before the point of ligament damage. Finally, ankle supports appear to improve balance only in individuals with previously injured ankles. This suggests that supports may have a selective effect in protecting injured but not uninjured individuals. Despite these positive effects, some cautions should be emphasized. First, most of the studies cited have been performed in the laboratory setting with joint velocities and loads much below what are encountered in the athletic and daily activities. Whether tape and braces can maintain their effectiveness under the more extreme conditions of functional activities remains unclear. Additionally, some evidence suggests that ankle supports may transfer loads to other joints putting them at risk for injury. Thus, further study is needed to determine the risk-to-benefit ratio of ankle supports. Finally, much of the research presented has been done only on uninjured ankles. Based on the current evidence, it seems possible that the effectiveness of ankle supports may differ depending on the population, and it seems clinically important to know whether we can expect the same results for injured and uninjured ankles. Proper and early rehabilitation is important in preventing residual ankle symptoms. Reports indicate that up to 73% of people who sustain a lateral ankle sprain have recurrent sprains, but it is unknown how many of these participants partake in rehabilitation. Proper immobilization and acute care of the injured ankle is imperative. An immobilization boot or strapping that can be removed during early non-weight bearing exercises seems to be most effective. Strength and balance training of the uninjured contralateral limb can be used to assist reaching full recovery in a shorter period of time. Functional exercises can also be performed earlier in the rehabilitation process by reducing the gravitational forces so patients can perform in a pain-free range and still receive the benefits of early activity. Evidence shows that daily ankle disk training assists in preventing ankle sprains, and is a relatively inexpensive and easy alternative to traditional rehabilitation protocols.

Ankle Injuries↗

PubMed2004

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.

Adult↗

PubMed2003

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.

Adult↗

PubMed2002

Acute Orthotic Intervention Does Not Affect Muscular Response Times and Activation Patterns at the Knee.

OBJECTIVE: To evaluate the short-term effect of a semirigid foot orthotic device on response times and activation patterns of knee musculature in individuals with hyperpronation after a lower extremity perturbation in a single-leg, weight-bearing stance. DESIGN AND SETTING: We used a lower extremity perturbation device designed to produce a forward and either internal or external rotation of the trunk and femur on the weight-bearing tibia to evoke a reflex response. Subjects were tested both with and without orthotic devices. SUBJECTS: Seventeen (13 male, 4 female) volunteers (age, 20.6 +/- 1.8 years; height, 181.0 +/- 8.1 cm; weight, 87.4 +/- 19.5 kg; navicular drop, 12.1 +/- 1.8 mm) with a navicular drop greater than 10 mm volunteered for this study. MEASUREMENTS: Long latency reflex times were recorded via surface electromyography for the medial and lateral hamstrings, gastrocnemius, and quadriceps muscles. RESULTS: A dependent-sample t test revealed a significant decrease in navicular drop with orthotic intervention (P <.0001). With that confirmed, separate repeated-measures analyses of variance with 2 within factors (orthotic condition and muscle) revealed no significant difference in muscle response time between orthotic and nonorthotic conditions for either internal or external rotation perturbation. Although we found a main effect for muscle for both internal (P <.0001) and external (P <.0001) rotation, indicating a preferred muscle activation order, this activation order did not differ between orthotic and nonorthotic conditions (internal rotation P =.674, external rotation P =.829). CONCLUSIONS: Our findings suggest that a short-term application of a semirigid orthotic device does not alter muscle response times or activation patterns of the muscles that stabilize the knee. Further research is needed to determine whether changes in activation patterns may occur over time since mechanical adaptations occur with long-term wear.

Journal Article↗

PubMed2002

The Effect of a Neoprene Shoulder Stabilizer on Active Joint-Reposition Sense in Subjects With Stable and Unstable Shoulders.

OBJECTIVE: To compare the effects of shoulder bracing on active joint-reposition sense in subjects with stable and unstable shoulders. DESIGN AND SETTING: Two subject groups, with stable and unstable shoulders, participated in an active joint-reposition test of the shoulder under braced and unbraced conditions. SUBJECTS: Forty subjects (22 men, 18 women; age = 21.85 +/- 3.12 years; height = 173.97 +/- 10.08 cm; weight = 71.27 +/- 11.68 kg) were recruited to participate in this study. Twenty Division I athletes were referred to us for shoulder instability, which was subsequently confirmed with clinical assessment. The remaining 20 subjects were recruited from a similar student population and assessed as having stable shoulders. MEASUREMENTS: Each subject's ability to perceive joint position sense in space was tested by actively reproducing 3 preset angles (10 degrees from full external rotation, 30 degrees of external rotation, and 30 degrees of internal rotation) with and without a shoulder brace. Full, active external-rotation range of motion was assessed before active joint-reposition sense testing. RESULTS: While wearing the shoulder brace, the group with unstable shoulders demonstrated significant improvement in the accuracy of active joint repositioning at 10 degrees from full external rotation in comparison with the stable group. Furthermore, those with unstable shoulders demonstrated significantly less full external rotation than did those with stable shoulders, and the brace reduced full external rotation only for those with stable shoulders. CONCLUSIONS: Our findings suggest that shoulder active joint-reposition sense in subjects with unstable shoulders can be improved at close to maximal external rotation by wearing a shoulder brace. This effect does not appear to be related to restriction of shoulder external rotation.

Journal Article↗

PubMed2002

Removal Tools are Faster and Produce Less Force and Torque on the Helmet Than Cutting Tools During Face-Mask Retraction.

OBJECTIVE: To investigate the retraction time, forces, and torques applied to the football helmet during removal of the face mask with different face-mask removal tools. DESIGN AND SETTING: Subjects retracted the face mask of a football helmet mounted to a force platform in a laboratory setting. They removed a standard face mask by cutting or removing (or both) the lateral plastic loop straps using 4 different tools: the Trainer's Angel (TA), FM Extractor (FM), power screwdriver (SD), and Quick Release System (QR) in a counterbalanced fashion. SUBJECTS: Eighteen certified athletic trainers participated in this study. MEASUREMENTS: We started measuring time when the subject picked up the tool and ended when the face mask was in a fully retracted position. Maximum forces and torques were measured from the force platform during the retraction process. RESULTS: The SD and QR retracted the face mask significantly faster than the TA and FM. Forces producing superior-inferior translation were least with the SD. The SD and QR produced less lateral translation and rotation and lateral flexion moment than the TA and FM. The FM produced less torque in the lateral flexion moment than the TA. CONCLUSIONS: Tools that removed the loop straps (SD, QR) were faster and produced less force and torque on the helmet than the tools that cut through the loop straps (TA, FM).

Journal Article↗

PubMedDate not supplied

Aberrant drug-taking behaviors and headache: patient versus physician report.

OBJECTIVE: To explore prevalence of aberrant medication-taking behaviors (AMTB) among headache patients and treating physician's awareness of such behaviors. METHODS: Fifty patientphysician dyads were surveyed on patients' AMTB. RESULTS: The most frequently endorsed behaviors by patients and physicians, respectively, were going to the ER for pain medication (n = 19) and continuing to take pain medication despite minimal relief (n = 23). For the majority of AMTB, phi coefficients indicating level of patient-physician agreement were equal to chance. CONCLUSIONS: Headache patients perform a wide range of AMTB. Low rates of patient-physician agreement indicate that physicians possess limited knowledge of patients' AMTB.

Adolescent↗

PubMedDate not supplied

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.

Journal Article↗

PubMedDate not supplied

Low-load eversion force sense, self-reported ankle instability, and frequency of giving way.

CONTEXT: Functional ankle instability has been attributed to proprioceptive loss. However, in previous studies of proprioception,authors have not investigated the ability to sense force at the ankle. Additionally, previous investigators have viewed functional ankle instability as either a present or absent condition,rather than a continuum. OBJECTIVE: To determine the relationship of ankle giving-way frequency and perceived ankle instability to ankle eversion force sense. DESIGN: Cohort design. SETTING: Sports medicine research laboratory. PATIENTS OR OTHER PARTICIPANTS: Twenty individuals (5 men,15 women) with a history of unilateral ankle instability. INTERVENTION(S): We tested subjects with 2 loads: 10% and 30% of maximal voluntary isometric contraction. MAIN OUTCOME MEASURE(S): We measured eversion force sense by calculating absolute, constant, and variable errors from a 3-trial force-matching procedure. Furthermore, subjects reported their frequency of giving way in units of times per day,week, or month, and these data were extrapolated to estimate annual giving-way frequency. Finally, subjects answers to 6 questions about ankle stability during typical daily or sports activities were summed to create a perceived ankle instability index. RESULTS: Significant relationships were found for only the 10% maximal voluntary isometric contraction. For absolute error,a positive relationship existed between the number of self reported episodes of giving way and eversion force sense for both ipsilateral (r .58) and contralateral (r .49) testing of the injured ankle. Constant error was correlated with giving way(r = -.56) for ipsilateral testing of the injured ankle. The ankle instability index was also positively correlated with eversion force sense absolute error (r .51) for ipsilateral testing only. CONCLUSIONS: Our results suggest that subjects with ankle instability had difficulty replicating eversion forces. Specifically,larger errors were related to both self-reported giving-way episodes and perceived ankle instability.

Journal Article↗

PubMedDate not supplied

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.

Journal Article↗