Measures of functional limitation as predictors of disablement in athletes with acute ankle sprains.

STUDY DESIGN: Prospective multivariate design. OBJECTIVES: To determine the usefulness of activity scores, self-reported athletic ability, and selected measures of physical impairment as predictors of disability duration in athletes with ankle inversion sprains. BACKGROUND: Although several measures of physical impairment and functional limitation are used to assess the consequences of injury following ankle sprain, researchers have yet to establish which measures provide the most accurate predictions of disability duration. METHODS AND MEASURES: Physical impairment, activity limitation, and disability duration were measured in 21 athletes (13 men and 8 women; mean age = 20.3 +/- 1.7 years) with acute ankle sprains. Sagittal plane ankle range of motion and volumetric displacement were used as impairment indicators. Weight-bearing activity scores (task completion count) and self-reported athletic ability (visual analog scale) were used to represent functional limitation. Elapsed time from injury to return to full athletic participation was used as the criterion measure of disability duration. RESULTS: The impairment measures accounted for approximately one-third of the variance in disability duration (R2 = 0.342). Adding the activity limitation measures to the regression model improved predictions of disability duration (R2 = 0.670; stepwise R2 change = 0.328). The measures of activity limitation alone, however, accounted for approximately 67% (R2 = 0.665) of the total variance in the number of days lost due to injury. CONCLUSION: Measures of activity limitation were the strongest predictors of elapsed time from injury to return to full athletic participation.

Assessment of neuromuscular response characteristics at the knee following a functional perturbation.

Previous research indicates that both the extent and timing of muscular activation at the knee can be influenced by muscle activity state, joint angle, weight-bearing status and trunk position. However, little research to date has evaluated protective neuromuscular response times and activation patterns to an imposed perturbation with the knee joint in a functional, weight-bearing stance. Hence, we designed a lower extremity perturbation device to produce a sudden, forward and either internal or external rotation moment of the trunk and femur relative to the weight-bearing tibia. Surface electromyography (EMG) recorded long latency reflex times of the medial and lateral quadriceps, hamstring and gastrocnemius muscles in 64 intercollegiate lacrosse and soccer players in response to both internal and external rotation perturbation. We found the gastrocnemius fired significantly faster that the hamstring, which in turn fired significantly faster than the quadriceps. There was also a significant difference in activation times of the medial and lateral hamstring not found for the quadriceps or gastrocnemius muscles. Our findings confirmed that reactive neuromuscular responses following this functional perturbation differ markedly from those previously reported using seated, partial weight-bearing and/or uni-planar models under relaxed conditions.

Effect of coupling medium temperature on rate of intramuscular temperature rise using continuous ultrasound.

OBJECTIVE: We determined the effects of coupling medium temperature on the rate of intramuscular temperature rise (RTR) during continuous ultrasound. DESIGN AND SETTING: Ultrasound was applied in a continuous mode at a frequency of 1 MHz and intensity of 1.5 W/cm(2). Each subject received 3 treatments, using water-based coupling gel at temperatures of 18 degrees C, 25 degrees C, and 39 degrees C. All treatments were performed in an athletic training room under controlled environmental conditions. SUBJECTS: Eighteen healthy male subjects (mean age = 23.6 +/- 3.5 years; height = 177.8 +/- 6.9 cm; weight = 76.6 +/- 8.2 kg; calf size = 37.6 +/- 2.4 cm) participated in this study. MEASUREMENTS: A thermistor was inserted into the left medial triceps surae at a depth of 5 cm, and baseline tissue temperatures were recorded before treatment. Intramuscular temperature was recorded every 30 seconds until the temperature rose 4 degrees C above baseline or until discomfort was felt. RTR was calculated by dividing the absolute temperature change by treatment time. RESULTS: A 1-way, repeated-measures analysis of variance revealed a significant difference in RTR among gel temperatures, RTR was significantly faster using the 25 degrees C gel compared with the 18 degrees C and 39 degrees C gels. There was no difference between the 18 degrees C and 39 degrees C gel treatments. CONCLUSIONS: These results suggest that the use of a cooled or heated gel may be counterproductive when maximal thermal effects are desired within a given time frame.

Eversion strength analysis of uninjured and functionally unstable ankles.

OBJECTIVE: Functional ankle instability (FAI) afflicts many athletes. Several causes of FAI have been implicated, including peroneal muscle weakness. Traditional musculoskeletal rehabilitation programs have focused on concentric muscle strength. The purpose of our study was to compare concentric and eccentric isokinetic and isometric eversion ankle strength measurements between subjects identified as having unilateral FAI and subjects having no history of inversion ankle sprain. DESIGN AND SETTING: Employing a matched-pairs technique, subjects with no history of ankle injury were compared with subjects with unilateral FAI using isokinetic and isometric measures of eversion ankle strength. Strength testing was performed in a sports medicine clinic setting. SUBJECTS: Forty-two subjects volunteered for this study: 21 subjects suffered from unilateral FAI (age = 19.3 +/- 1.1 years, wt = 84.0 +/- 9.5 kg, ht = 181.5 +/- 9.2 cm), while 21 subjects served as matched-paired controls (age = 19.5 +/- 1.2 years, wt = 82.5 +/- 10.9 kg, ht = 179.5 +/- 7.9 cm). MEASUREMENTS: Ankle eversion concentric and eccentric strength (peak torque) was assessed at 0 degrees /s, 30 degrees /s, 60 degrees /s, 90 degrees /s, 120 degrees /s, 150 degrees /s, and 180 degrees /s using an isokinetic dynamometer. RESULTS: We found no significant differences in concentric, eccentric, or isometric eversion ankle strength between the 2 groups of subjects. CONCLUSIONS: The exact cause of FAI remains elusive. Based on our results, those who suffer from unilateral FAI do not appear to have eversion strength deficits. Unless clear evidence of weakness exists, clinicians may find that eversion strength training exercises are unnecessary. Future research should examine other causes of FAI, including reciprocal muscle group strength ratios and proprioception deficits.

Reliability and responsiveness of disablement measures following acute ankle sprains among athletes.

The minimum amount of change which represents clinical improvement following ankle sprains is unknown. This study considers the usefulness of physiological and behavioral measures commonly employed for this purpose in sports rehabilitation settings. Thirteen collegiate athletes of both genders were measured at approximately 3 and 10 days post-grade I or II ankle sprain. Volumetric displacement and sagittal plane ankle range of motion measures were used as impairment indicators. Motor ability scores (activity count) and a perceived athletic ability measure (visual analog scale) were used to indicate functional limitations. Volumetric displacement and both functional limitation measures demonstrated responsiveness to change between two occasions of measurement separated by 1 week. Observed changes in range of motion deficits could not be distinguished from measurement error. The results of this study suggest that behavioral measures of motor activity and perceived athletic ability may be at least as useful as physical measures of organic dysfunction for assessing clinical improvement following acute ankle sprains among athletes.

Effect of Trunk Position on Anterior Tibial Displacement Measured by the KT-1000 in Uninjured Subjects.

OBJECTIVE: Clinicians may obtain false-negative Lachman tests for tibial displacement when the trunk position of the athlete varies as the anterior cruciate ligament injury is assessed on the field, on the sideline, and in the clinic. We examined the influence of supine, semireclined, and sitting trunk positions on arthrometric laxity measurements of the knee. DESIGN AND SETTING: Subjects in the 3 trunk-thigh test positions (15 degrees , 45 degrees , and 90 degrees of hip flexion) were passively supported and tested in a counterbalanced order. The right knee was maintained at 29.0 degrees +/- 3.1 degrees of flexion. A 133-N (30-1b) anterior force was applied to the right knee using a modified KT-1000 knee arthrometer equipped with a strain gauge that allowed for digital display of the displacement force. SUBJECTS: Ten males and 5 females without present knee injury or history of knee ligament repair to the right lower extremity. MEASUREMENTS: Three tibial displacement (mm) trials at each trunk position were averaged and used for analysis. RESULTS: A 1-factor (trunk-thigh position) repeated-measures analysis of variance revealed no significant difference in anterior tibial displacement values among the 3 trunk-thigh positions (P > .05). Group means for displacement were 7.9 +/- 2.3 mm (supine), 8.1 +/- 2.5 mm (semireclined), and 8.3 +/- 2.6 mm (sitting). CONCLUSIONS: These findings suggest that alterations in trunk position are not a problem in the instrumented assessment of anterior tibial displacement in an uninjured population. Further research should determine the relevance of these findings, as well as "end-feel" (ie, stiffness) in subjects with injury to the anterior cruciate ligament. Further research should also determine if these findings can be applied when comparing passive versus active (eg, propped on elbows or hands) trunk support in subjects with anterior cruciate ligament-injured knees.

Importance of selected athletic trainer employment characteristics in collegiate, sports medicine clinic, and high school settings.

OBJECTIVE: We examined employer importance ratings of 35 employee characteristics in the collegiate, sports medicine clinic, and high school settings and made comparisons among these settings. DESIGN AND SETTING: All prospective employers were sent a survey. Of the 472 surveys mailed, 282 (60%) were returned, with a sample error rate of 1.9%. SUBJECTS: All prospective employers listed on the NATA position vacancy notices from January 1, 1994 to October 1, 1994. MEASUREMENTS: Employers were asked to rate 35 employee characteristics as "not important" " minimally important," " important." or "very important." Additionally, employers chose 1 of 15 job descriptors that best identified their position vacancy. These 15 descriptors were then categorized into collegiate, sports medicine clinic, and high school settings. Discriminant analysis and analysis of variance procedures were used to determine if the 35 employee characteristics differed across the 3 settings. RESULTS: The discriminant analysis produced 2 significant discriminant functions (P < .05) with 23 of the original 35 characteristics remaining in the analysis. The first function discriminated between the collegiate setting and the other settings, with the collegiate setting scoring the highest. The second function discriminated among all 3 groups, with the sports medicine clinic and high school settings scoring the highest and lowest, respectively. Additionally, the analyses of variance (ANOVAs) revealed that 21 of the characteristics remaining in the discriminant analysis differed across the 3 settings. CONCLUSIONS: Employers from all 3 settings rated educational program reputation, written recommendations, job interview performance, and NATA-BOC certification eligibility as important to very important. For the collegiate setting, 7 characteristics were rated above important and included such characteristics as possession of a master's degree and collegiate experience. For the sports medicine clinic, 8 characteristics were rated above important and included sports medicine clinic experience, high school experience, and sport-specific experience. Finally, for the high school setting, 5 characteristics were rated above important. These included NATA-BOC certification, a bachelor's degree, and high school experience.

A trend analysis of the in vivo quadriceps femoris angle-specific torque-velocity relationship.

To adequately assess isokinetic human muscle performance, it is important for clinicians to understand how the muscle functions across a range of velocities. Thus, the purpose of this study was to re-examine the in vivo quadriceps torque-velocity relationship using trend analysis. Twelve uninjured university-age females performed three concentric and eccentric contractions at velocities of 0, 25, 50, 75, 100, 125, 150, 175, and 200 degrees/sec on the Kin-Com isokinetic dynamometer. A trend analysis was performed on the angle-specific torques at 30, 60, and 75 degrees of knee flexion. The results indicated that the concentric and eccentric relationships at 30 degrees and the concentric relationship at 60 degrees were represented by a third-order polynomial, and a linear relationship was found for concentric contractions at 75 degrees. There were no significant trends for the eccentric relationship at 60 and 75 degrees, suggesting that they were best described by the grand mean. These results suggest that muscular torque production varies across velocities and contraction modes and that this relationship varies depending on the joint angle of torque measurement.

Effect of mild head injury on postural stability in athletes.

OBJECTIVE: Athletic trainers and team physicians are often faced with the dilemma of when to return athletes to participation following mild head injury. Unfortunately, clinicians rarely have quantitative information on which to base their decisions. The purpose of this investigation was to identify postural stability changes in athletes with acute mild head injury. DESIGN AND SETTING: High school and college male athletes were prescreened for postural stability before the start of their season. Subjects suffering injury during the season returned for testing on days 1, 3, 5, and 10 following injury, and 1 month postseason. Control subjects were selected for comparisons. SUBJECTS: Ten prescreened subjects (age = 17.4 +/- 2.2 yr; ht = 183.8 + 8.1 cm; wt = 87.7 + 17.3 kg) returned for testing following an injury. Ten matched control subjects (age = 18.6 +/- 2.6 yr; ht = 185.7 +/- 6.7 cm; wt = 84.5 +/- 19.5 kg) were selected for comparisons. Additionally, nine subjects (eight male and one female) (age = 19.9 +/- 4.2 yr; ht = 182.3 + 10.9 cm; wt = 89.6 +/- 25.2 kg) who had sustained a mild head injury from other varsity sports teams were recruited. Nine matched controls (age = 22.1 +/- 3.3 yr; ht = 181.0 +/- 9.9 cm; wt = 84.9 +/- 25.6 kg) were again utilized. MEASUREMENTS: Sway index and center of balance were measured using the Chattecx Balance System during three eye conditions and three surface conditions for all subjects. RESULTS: Repeated measures analyses of variance (ANOVA) for each prescreened subject's sway index revealed significant differences between injured subjects and control subjects on day 1 postinjury as compared with the prescreening and/or subsequent tests. The analysis for sway index and center of balance inclusive of all 19 subjects with mild head injury and all 19 control subjects demonstrated increased postural sway compared with control subjects on day 1 postinjury during all plafform conditions, and on day 3 during the foam platform condition. The analysis for center of balance using the same subjects revealed that injured subjects maintained their center of balance farther away on day 1 postinjury compared with subsequent tests (p < .05). CONCLUSIONS: These findings suggest that computerized dynamic posturography is a useful tool in objectively assessing postural stability in subjects with mild head injuries. Subjects with mild head injury appear to demonstrate impaired postural stability 1 to 3 days following injury. This information should aid clinicians in determining when an athlete can safely return to participation.

1994 athletic trainer employment and salary characteristics.

OBJECTIVE: THE PURPOSE OF THIS STUDY WAS TO DETERMINE: 1) demographics and professional credentials of recently hired athletic trainers, 2) the association between these characteristics and the high school, clinical, and collegiate setting, and 3) which of these factors best predicted salary. DESIGN AND SETTING: A survey was sent to all prospective employers. Of the 472 surveys sent, 282 (60%) were returned. SUBJECTS: Prospective employers who were listed on the NATA job vacancy notices from January 1, 1994 to October 1, 1994. MEASUREMENTS: Employers selected a job description for their position opening and indicated the characteristics of the people they hired. The job descriptions were placed into three categories. A chi-square analysis was used to determine the degree of association between applicant characteristics and job descriptions. Employee characteristics were coded and a stepwise multiple regression analysis was performed to determined which of the characteristics best predicted salary. Analyses of variance were performed to determine differences among the three practice settings and as follow-up analyses to the multiple regression. An analysis of variance was also performed to compare salaries based on job description and teaching responsibilities. RESULTS: No association was found between the employment setting and gender, ethnicity, marital status, educational route, physical therapy, credential, or EMT certification. There was an association between the CPR instructor's credential and employment setting and between highest degree attained and employment setting. CONCLUSIONS: The results suggest that these factors were most closely associated with employment in the collegiate setting. With regard to salary, it was determined that a doctoral degree, a master's degree, and marital status were the best predictors of salary.

Effect of ACL Reconstruction and Tibial Rotation on Anterior Knee Laxity.

The anterior cruciate ligament (ACL) is the primary restraint to anterior translation of the tibia on the femur. Research suggests that resistance to anterior translation changes as the tibia is rotated internally and externally. This study assessed the degree to which ACL reconstruction and tibial rotation affects anterior knee laxity. Nine subjects with ACL lesions and functional instabilities participated in the study. Subjects were measured 1 to 10 days before surgery and 6 to 8 months after ACL reconstruction using the KT-1000 knee arthrometer. A mechanical leg stabilizer was used to assess anterior translation at 20 degrees of knee flexion in three positions: internal rotation of 15 degrees , neutral, and external rotation of 15 degrees . Subjects were measured at 89 and 67 N of anterior force. Data were analyzed with a three-factor (test x position x force) repeated measures ANOVA. Following surgery, reduction in laxity (mm) for the three positions (internal rotation, neutral, and external rotation) was 1.9, 2.8, and 3.4, respectively, at 89 N and 1.5, 2.0, and 2.6, respectively, at 67 N. The degree of reduction in laxity (presurgery to postsurgery) was dependent upon rotation and force, and was greatest in external rotation and least in internal rotation pre- to postsurgery. We concluded that ACL reconstruction using a patellar tendon graft significantly decreased anterior tibial translation at all three positions, but a greater amount of reduction was observed postsurgically at the externally rotated position. This supports the theory that mechanical blocks and secondary restraints such as a taut mid-third of the iliotibial tract may interfere with clinical laxity tests in some positions of tibial rotation. Fixing the tibia in an externally rotated position may decrease the effect of secondary restraints and improve sensitivity in testing for ACL laxity.

Comparison of isokinetic strength and flexibility measures between hamstring injured and noninjured athletes.

The purpose of this study was to compare isokinetic strength and flexibility measures between hamstring injured and noninjured athletes. Sixteen university athletes with history of hamstring injury were matched by motor dominance, sport, and position to sixteen university athletes without history of hamstring injury. Each subject was tested for concentric and eccentric quadriceps and hamstring peak torque and reciprocal muscle group ratios on a Kinetic Communicator(R) (KIN-COM) dynamometer at 60 degrees /sec and 180 degrees /sec. Each subject's hamstring flexibility was determined by passively extending the knee while the hip was maintained at 90 degrees of flexion. Analysis of variance indicated that the injured extremity was significantly less flexible than the noninjured extremity within the hamstring injured group, and the hamstring injured group was less flexible than the noninjured group. No significant strength differences existed between the hamstring injured and noninjured group on any isokinetic measure evaluated. The importance of assessing hamstring flexibility is emphasized. J Orthop Sports Phys Ther 1991;13(3):118-125.