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AIM: To elucidate the hormonal influences on sex differences in knee joint behavior, normal-menstruating females were compared to males on serum hormone levels and anterior knee joint laxity (displacement at 46N, 89N and 133N) and stiffness (Linear slope of deltaForce/deltaDisplacement for 46-89N and 89-133N) across the female menstrual cycle. METHODS: Twenty-two females were tested daily across one complete menstrual cycle, and 20 males were tested once per week for 4 weeks. Five days each representing the hormonal milieu for menses, the initial estrogen rise near ovulation, and the early and late luteal phases (total of 20 days) were compared to the average value obtained from males across their 4 test days. RESULTS: Sex differences in knee laxity were menstrual cycle dependent, coinciding with significant elevations in estradiol levels. Females had greater laxity than males on day 5 of menses, days 3-5 near ovulation, days 1-4 of the early luteal phase and days 1, 2, 4 and 5 of the late luteal phases. Within females, knee laxity was greater on day 5 near ovulation compared to day 3 of menses, and days 1-3 of the early luteal phase compared to all days of menses and day 1 near ovulation. On average, differences observed between sexes were greater than those within females across their cycle. There were no differences in anterior knee stiffness between sexes or within females across days of the menstrual cycle.

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STUDY DESIGN: One-group discriminant analysis. OBJECTIVE: To determine whether 1 MHz of continuous ultrasound can identify tibial stress fractures in subjects. BACKGROUND: Stress fractures can lead to loss of function or to more serious nonunion fractures. Early diagnosis is important to reduce the risk of further injury and to assure a safe return to activity. Therapeutic ultrasound has been reported to be an accessible, less expensive alternative in diagnosing stress fractures compared with other diagnostic techniques. METHODS AND MEASURES: Twenty-six subjects (12 men, 20.33 +/- 1.37 years; 14 women, 20.78 +/- 3.8 years) with unilateral tibia pain for less than 2 weeks volunteered to participate in the study. Continuous, 1 MHz ultrasound was applied to the uninvolved and involved tibias at 7 increasing intensities for 30 seconds each. Subjects completed a visual analog scale after the application of each intensity to assess the pain response to ultrasound. Results from the visual analog scale were compared to magnetic resonance imaging (MRI) findings to determine if continuous ultrasound could predict whether subjects had a normal MRI, increased bone remodeling, or advanced bone remodeling consistent with a stress fracture. RESULTS: Discriminant analysis on the visual analog scale correctly classified subjects into 1 of 3 clinical classification groups in 42.31% of the cases. None of the subjects found to have a stress fracture by MRI were correctly identified by continuous ultrasound. This resulted in a predicted sensitivity of 0% and a predicted specificity of 100%. CONCLUSIONS: A protocol using visual analog scores after the application of 1 MHz continuous ultrasound is not sensitive for identifying subjects with tibial stress fractures.

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PURPOSE: Previous studies have documented the lack of ultrasound's non-thermal effects on nerve conduction using frequencies of 1 MHz and 870 kHz. The analyses and conclusions were reached, despite only one study incorporating pulsed ultrasound. The purpose of this study was to determine the biophysical effects of continuous wave (CW) and pulsed wave (PW) ultrasound on median nerve motor and sensory latencies using common frequencies of 1.0 and 3.0 MHz. SUBJECTS: Fifteen healthy subjects (8 males, 7 females, age = 23.5 + 4.44 yrs, height = 171.2 + 10.7 cm, weight = 67.5 + 7.9 kg) without a history of neurological or musculoskeletal injury to their non-dominant arm volunteered for testing. METHODS AND MATERIALS: Subjects were exposed in counterbalanced order to five ultrasound treatment conditions: (1) 1 MHz, 1.0 W/cm2, 8 min., (2) 1 MHz, 1.0 W/cm2, 50% PW, 8 min., (3) 3.0 MHz, 1.0 W/cm2, CW, 8 min., (4) 3.0 MHz, 1.0 W/cm2, 50% PW, 8 min., (5) placebo, 0.0 W/cm2, 8 min. Dependent measures for motor and sensory latencies, and subcutaneous temperatures were taken pretreatment, at 2, 4 and 6 minutes during treatment, and immediately post-treatment. Separate two within repeated measures ANOVA were used for each dependent measure. RESULTS: Analysis revealed significant interactions for motor latencies [F (16,224) = 52.77, p < .001], sensory latencies [F (16,224) = 41.10, p < .001], and subcutaneous temperatures [F (16,224) = 52.77, p < .001]. Tukey's HSD post hoc analyses confirmed that nerve latencies responded similarly to subcutaneous temperature changes during and after ultrasound treatment. CONCLUSIONS: Alterations in nerve latencies from ultrasound on healthy nerves appeared to be related to temperature changes induced by ultrasound's thermal effects, and not by non-thermal or mechanical effects.

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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.

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OBJECTIVE: To determine the efficacy of the National Athletic Trainers' Association Board of Certification (NATABOC) clinical experience requirements and individual student characteristics to predict candidate outcomes on the NATABOC certification examination. DESIGN AND SETTING: For all subjects, we gathered survey information and examination scores. The survey information included age, sex, route to certification, previous athletic training and allied health experience, and clinical education experiences. SUBJECTS: A total of 269 subjects, 22.25% of all first-time candidates for the June and November 1993 NATABOC examinations, were included in this study. MEASUREMENTS: Data were analyzed for standard descriptive statistics and parametric linear regression and correlational relationships. RESULTS: Total clinical hours, high-risk sport experiences, and previous athletic training experience were not predictive of examination outcomes. Although our results indicated a relationship between previous allied health experience and both outcome on the written section of the examination and age and outcome on the oral/practical section, these characteristics also were not predictive of examination outcomes. CONCLUSIONS: Gaining clinical experience hours in excess of 400 hours beyond the 800-or 1500-hour requirement may yield no greater benefit for an entry-level professional than less time. The quality, rather than the quantity, of clinical experiences should be evaluated. More emphasis should be placed on the achievement of an entry level of clinical competency, rather than on total hour collection. Also, because high-risk sport experiences did not predict outcomes on the NATABOC examination, the emphasis of clinical education should be on students' receiving a more structured clinical experience, in which they are progressively required to assume greater responsibilities integrating both cognitive and psychomotor skills, while working under the supervision of a certified athletic trainer.

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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.

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OBJECTIVE: To provide an overview of the continuum of muscular responses that typically occur with joint perturbation. The applications and limitations of surface electromyography (sEMG) in evaluating these responses are also addressed. Research applications assessing sex differences in these neuromuscular response characteristics are discussed along with suggestions for future research. DATA SOURCES: MEDLINE was searched from 1969 through 1998. Sport DISCUS was searched from 1975 through 1998. Terms searched included "anterior cruciate ligament," "epidemiology," "neuromuscular control," "neuromuscular performance," "electromyography," "latency," "reflex," "electromechanical delay," "dynamic stability," "intrinsic stiffness," "short-range stiffness," "muscle," "mechanoreceptors," and "reaction time." DATA SYNTHESIS: It is widely accepted that efficient neuromuscular control is essential to dynamic joint stability and protection. Many studies have established the significant role of the muscles, and particularly the hamstrings, in providing knee stability. By observing the timing, phasing, and recruitment of reflexive muscular activation after a loading stress to the knee, we can better understand the coordinative mechanisms necessary to protect the joint and prevent ligament injury. A number of research models have employed the use of sEMG to evaluate neuromuscular responses at the knee after joint loading or perturbation. However, very few studies have specifically addressed potential sex differences in these response characteristics. CONCLUSIONS/RECOMMENDATIONS: From the limited research available, it appears that a sex difference may exist in some aspects of neuromuscular responses. However, further research is needed to explore these differences at the knee and their potential role as predisposing factors to the higher incidence of anterior cruciate ligament injuries in females. Future studies should examine sex differences in neuromuscular response characteristics at the knee under functional, weight-bearing conditions while controlling for training and other confounding variables. The limitations of sEMG should be considered when interpreting neuromuscular response studies.

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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.

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OBJECTIVE: To examine the efficacy of microcurrent electrical neuromuscular stimulation (MENS) treatment on pain and loss of range of motion (ROM) associated with delayed-onset muscle soreness (DOMS). DESIGN AND SETTING: We assigned subjects to 1 of 2 groups. Group 1 received treatment with microcurrent stimulation (200 muA, 30 Hz, for 10 minutes, then 100 muA, 0.3 Hz, for 10 minutes) 24, 48, and 72 hours after DOMS induction. Group 2 served as a sham group and was treated using a machine altered by the manufacturer so that no current could flow through the electrodes. SUBJECTS: DOMS was induced in the biceps brachii of the nondominant arm of 18 subjects (3 males, 15 females: age = 20.33 +/- 2.3 years, ht = 170.81 +/- 7.3 cm, wt = 69.61 +/- 13.1 kg). Dominance was defined as the arm used by the subject to throw a ball. MEASUREMENTS: Subjective pain and active elbow extension ROM were evaluated before and after treatment each day. Two methods were used to assess pain: constant pressure using a weighted Orthoplast sphere and full elbow extension to the limit of pain tolerance. Subjective pain was measured with a graphic rating scale and active elbow extension ROM using a standard, plastic, double-armed goniometer. Three repeated-measures ANOVAs (between-subjects variable was group, within- subjects variables were day and test) were used to assess ROM and pain scores for the 2 groups. RESULTS: We found no significant difference in the measurement of subjective pain scores or elbow extension ROM when the MENS group was compared with the sham group. CONCLUSIONS: Our results indicate that the MENS treatment, within the parameters used for this experiment, was not effective in reducing the pain or loss of ROM associated with delayed-onset muscle soreness.

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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.

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Exercises to improve joint proprioception and coordination of the functionally unstable ankle are advocated throughout the literature, yet there is little evidence that these exercise have any effect on proprioception and balance. The purpose of this study was to determine the effects of a 6-week coordination and balance training program on proprioception of subjects with functional ankle instability. Forty-five subjects (age = 22.53 +/- 3.95 years, height = 172.04 +/- 10.0 cm, weight = 71.72 +/- 15.7 kg) were randomly placed into a control (Group 1), sham (Group 2), or experimental (Group 3) group. The experimental group trained 3 days per week, 10 minutes each day, performing various balance and proprioception exercises. Postural sway and active and passive joint position sense were assessed. Analysis of variance for postural sway modified equilibrium score for anterior and posterior sway, as well as medial and lateral sway revealed significant four-way interactions. Tukey post hoc analyses revealed that Group 3 performed significantly better (p < .05) than Group 1 and Group 2 on the posttests. There were no significant differences for joint position sense or postural sway index. Results suggest that balance and coordination training can improve some measures of postural sway. It is still unclear if joint position sense can be improved in the functionally unstable ankle.

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