Activation of the VMO and VL during dynamic mini-squat exercises with and without isometric hip adduction.

OBJECTIVE: the purpose of this study was to compare vastus medialis obliquus (VMO) and vastus lateralis (VL) activity while performing a mini-squat with and without isometric hip adduction. DESIGN AND SETTING: a repeated measures within subjects design was used. Subjects performed two sets of three repetitions of a traditional mini-squat and a mini-squat with concurrent hip adduction (squeeze). SUBJECTS: 20 recreationally active subjects (10 men, 10 women age=28.10+/-5.91 years, height=170.94+/-11.03 cm, mass=72.32+/-16.66 kg) with no history of patellofemoral pain (PFP), quadriceps injury, or other knee injury participated in the study. MEASUREMENTS: the EMG signal of the VMO and VL was recorded bilaterally during both exercises. EMG data were normalized to the maximal voluntary isometric contraction (MVIC) of the quadriceps produced during seated, isometric knee extension. RESULTS: results of repeated measures ANOVA's revealed that the squeeze squat produced significantly greater VMO and VL activity than the traditional squat (p=0.02). For both the traditional and squeeze squats, intrasession reliability from the first to the second set was calculated using intraclass correlation coefficient (ICC) formula (3:1) bilaterally for both the VMO and the VL. All ICC values were greater than 0.9. CONCLUSION: combining isometric hip adduction with a mini-squat exercise significantly increases the activity of the quadriceps. Performing mini-squats with isometric hip adduction will be beneficial to patellofemoral patients as they increase quadriceps activity, however, based on our data we cannot conclude that this exercise preferentially recruits the VMO. Further research is needed to determine the exact mechanism by which quadriceps function is altered.

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 orthotics on postural sway after fatigue of the plantar flexors and dorsiflexors.

OBJECTIVE: To examine the effects of orthotic intervention on unilateral postural sway after fatigue of the plantar flexor and dorsiflexor muscle groups. DESIGN AND SETTING: Subjects were assigned to both orthotic and nonorthotic testing conditions in a counterbalanced order, then assessed for postural sway before and after isokinetic fatiguing contractions of the plantar flexors and dorsiflexors. Postural stability was measured on the motor-dominant extremity. (Motor dominance was assessed as the foot the subject used to kick a ball.) SUBJECTS: Eleven active, healthy male subjects (mean age = 24 +/- 2.0 years, wt = 74.5 +/- 8.8 kg, ht = 180.3 +/- 8.4 cm) volunteered to participate in the study. MEASUREMENTS: Center-of-pressure postural sway was assessed via the force platforms of a Chattecx Dynamic Balance System and transformed via 4 transducers as values indicative of sway in the anterior-posterior and medial-lateral directions. The dependent measure was postural sway in centimeters. Fatigue was induced by consecutive concentric plantar flexiondorsiflexion contractions on a Kin-Com II isokinetic dynamometer. RESULTS: A repeated-measures analysis of variance revealed a significant orthotic-by-test interaction. Post hoc analysis with the Tukey honestly significant difference method revealed that postural sway values of the postfatigue nonorthotic condition were significantly greater when compared with the prefatigue orthotic, prefatigue nonorthotic, and postfatigue orthotic conditions. CONCLUSIONS: Our results suggest that molded orthotics may be an effective means of decreasing postural sway after an isokinetic fatigue protocol. Further research is needed to determine the exact mechanism of this improvement and whether orthotics are an effective means of preventing ankle injury.

Duration of maintained hamstring flexibility after cessation of an acute static stretching protocol.

OBJECTIVE: Increased muscle flexibility from static stretching is supported by the literature, but limited research has assessed the duration of maintained flexibility gains in knee joint range of motion after same-day static hamstring stretching. The purpose of our study was to determine the duration of hamstring flexibility gains, as measured by an active knee-extension test, after cessation of an acute static stretching protocol. DESIGN AND SETTING: All subjects performed 6 active warm-up knee extensions, with the last repetition serving as the baseline comparison measurement. After warm-up, the experimental group performed 4 30-second static stretches separated by 15-second rests. SUBJECTS: Thirty male subjects (age = 19.8 +/- 5.1 years, ht = 179.4 +/- 18.7 cm, wt = 78.5 +/- 26.9 kg) with limited hamstring flexibility of the right lower extremity were randomly assigned to control and experimental groups. MEASUREMENTS: Postexercise active knee-extension measurements for both groups were recorded at 1, 3, 6, 9, 15, and 30 minutes. RESULTS: Tukey post hoc analysis indicated significant improvement of knee-extension range of motion in the experimental group that lasted 3 minutes after cessation of the static stretching protocol. Subsequent measurements after 3 minutes were not statistically different from baseline. A dependent t test revealed a significant increase in knee-extension range of motion when comparing the first to the sixth active warm-up repetition. CONCLUSIONS: Our results suggest that 4 consecutive 30-second static stretches enhanced hamstring flexibility (as determined by increased knee-extension range of motion), but this effect lasted only 3 minutes after cessation of the stretching protocol. Future research should examine the effect of other stretching techniques in maintaining same-day flexibility gains.

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.

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.

Effects of strength training on strength development and joint position sense in functionally unstable ankles.

OBJECTIVE: To examine the effects of ankle-strengthening exercises on joint position sense and strength development in subjects with functionally unstable ankles. DESIGN AND SETTING: Subjects were randomly assigned to a training or control group. The training group participated in a 6-week strength-training protocol using rubber tubing 3 times a week throughout the training period. The control group did not participate in the strength-training protocol. SUBJECTS: Twenty healthy college students (10 females, 10 males, age = 20.6 +/- 2.23 years; ht = 176.40 +/- 7.14 cm; wt = 74.18 +/- 10.17 kg) with a history of functional ankle instability volunteered to participate in this study. MEASUREMENTS: We pretested and posttested dorsiflexor and evertor isometric strength with a handheld dynamometer and collected joint position sense (JPS) data at 20 degrees for inversion and plantar flexion and at 10 degrees for eversion and dorsiflexion. RESULTS: Statistical tests for strength and JPS revealed significant group-by-time interactions for dorsiflexion strength, eversion strength, inversion JPS, and plantar flexion JPS. Simple main-effects testing revealed improvements in training group strength and JPS at posttesting. There were no significant effects for eversion JPS, but the group main effect for dorsiflexion JPS was significant, with the experimental group having better scores than the control group. CONCLUSIONS: Ankle-strengthening exercises improved strength, inversion JPS, dorsiflexion JPS, and plantar flexion JPS in subjects with functionally unstable ankles.

Examination of balance measures produced by the biodex stability system.

OBJECTIVE: Our purpose was to establish normal patterns and relationships of stability using the Biodex Stability System. DESIGN AND SETTING: The design of this study used both nonexperimental and quasi-experimental methods. All testing was performed in a university sports medicine laboratory. SUBJECTS: Nineteen healthy subjects (8 males, 11 females, age = 24.4 +/- 4.2 years; wt = 70.5 +/- 20 kg; ht = 171.2 +/- 11.7 cm) with no history of lower extremity injury participated in this study. MEASUREMENTS: For data analysis, the medial/lateral stability index (MLSI), anterior/posterior stability index (APSI), overall stability index (OSI), and time-in-balance scores were recorded. RESULTS: Multiple regression revealed that APSI and MLSI significantly contributed to the OSI, with the APSI accounting for 95% of the OSI variance. Additionally, the percentage of time spent between 0 degrees and 5 degrees from level was significantly greater than the time spent between 6 degrees and 10 degrees , 11 degrees and 15 degrees , and 16 degrees and 20 degrees . Furthermore, the percentage of time spent between 6 degrees and 10 degrees was significantly greater than the time spent between 16 degrees and 20 degrees . CONCLUSIONS: These data suggest that uninjured individuals spent the majority of the time balanced within 0 degrees to 5 degrees from level and progressively less time at greater angles. Additionally, the data suggest that the OSI is very closely related to the APSI and receives a relatively small contribution from the MLSI. Because of this small contribution, if the clinician is interested in both anterior-posterior and medial-lateral motions, it may be best to use the MLSI and APSI separately rather than the OSI.

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.

Role of hyperpronation as a possible risk factor for anterior cruciate ligament injuries.

OBJECTIVE: The purpose of this study was to examine the relationship between hyperpronation and the occurrence of noncontact injury to the anterior cruciate ligament (ACL). DESIGN AND SETTING: Subjects were categorized as either ACL injured (ACLI) or ACL uninjured (ACLU). All ACLI subjects received their injuries from a noncontact mechanism. To justify using the ACLI subjects' uninjured legs as representative of their preinjury state, a t test was used to compare the differences between the left and right foot for the ACLU group on both measurements. Based on the results of the t test, a regression analysis was performed to determine whether group membership could be predicted from navicular drop. All measures were performed in a university athletic training room. SUBJECTS: Fourteen ACLI subjects (age = 21.07 +/- 0.83 yr, ht = 174.81+/-8.29 cm, wt = 72.32+/-13.47 kg) and 14 ACLU subjects (age = 21.14+/-2.03 yr, ht = 177.35+/-11.31 cm, wt = 72.99+/-14.81 kg) participated. MEASUREMENTS: Hyperpronation was assessed via the navicular drop test and the calcaneal stance test. RESULTS: No significant difference (p > .05) between feet for the navicular drop test was found. However, there was a significant difference (p < .05) between feet for the calcaneal stance test, and, thus, this measure was not used in the regression analysis. Using the navicular drop score, the regression analysis was unable to predict group membership. CONCLUSIONS: Hyperpronation as measured by the navicular drop test was not a predictor of ACL injury, and, thus, may not be a predisposing factor to noncontact ACL injuries.

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.

A review of selected blood-borne pathogen position statements and federal regulations.

One response to the AIDS epidemic has been the formation of blood-borne pathogen policy statements by medical associations, athletic governing bodies, and the federal government. The policy statements by medical associations and athletic governing bodies discuss a wide range of issues, including the eligibility of infected athletes and the right of infected health care workers to practice. In contrast, federal regulations are limited to employees in the work environment. Despite the apparent comprehensiveness of these documents, major deficiencies in the documents do exist. For example, employees exposed to body fluids are entitled to free, employer-provided HIV testing. Similarly, athletes exposed to body fluids also are entitled to voluntary HIV testing. However, it is unclear who should pay for this testing. Furthermore, AIDS testing of student athletic trainers is never discussed. Although there are deficiencies, these documents provide guidelines for resolving the deficiencies. For example, because student athletic trainers act as employees of their institution, it is reasonable to suggest that they receive the same protections that federal regulations provide to employees. Thus, the athletic trainer should find these documents useful for developing policies related to blood-borne pathogens.

The Reliability Of Three Isokinetic Knee-extension Angle-specific Torques.

To determine the reliability of concentric quadriceps muscle torque at 30 degrees , 60 degrees , and 75 degrees of knee extension, 25 female university students were studied. Each subject was tested on the Kin-Com isokinetic dynamometer on 2 separate days, 7 days apart. The dynamometer's speed was set at 60 degrees ls. Intraclass correlation coefficients for 30 degrees , 60 degrees , and 75 degrees were 0.84 (p<.01), 0.87 (p<.01), and 0.83(p<.01), respectively. The standard errors of the measure were 5.92 N.m, 7.65 N.m, and 7.35 N.m, respectively. Based on the instrumentation and protocol used in this study, we believe angle-specific torques have good reliability. Because of the error size, clinicians using similar methodology to determine angle-specific torques should be cautious when comparing differences between angle-specific torques of less than 12 to 16 N.m.

Differential transcription of Pgk genes during spermatogenesis in the mouse.

We have analyzed the occurrence of transcripts produced from the ubiquitously expressed, X-linked Pgk-1 gene and the testis-specific, autosomal Pgk-2 gene during spermatogenesis in the mouse. We found that tissue specificity, developmental specificity, and cell-type specificity of these mRNAs parallel that previously reported for the two protein isozymes of phosphoglycerate kinase (PGK) encoded by these two genes. This indicates that primary regulation of differential expression of the Pgk genes during spermatogenesis is exerted at the transcriptional level. We first detected Pgk-2 mRNA in preleptotene spermatocytes, indicating that transcription of Pgk-2 is initiated coincident with the onset of meiosis in male germ cells, and then continues to increase in later spermatocytes and postmeiotic round spermatids. This expression initiates prior to an initial decline in Pgk-1 transcript levels observed in pachytene spermatocytes, which apparently follows inactivation of the single X chromosome in spermatogenic cells. However, unlike cessation of Pgk-1 transcription from the inactivated X chromosome in female somatic cells, we show that inactivation of the Pgk-1 locus in spermatogenic cells is not followed by methylation of a key CpG dinucleotide in the promoter region. These results support the idea that specific expression of the Pgk-2 gene in meiotic and postmeiotic spermatogenic cells has evolved to compensate for reduced levels of Pgk-1 gene product caused by transient X-chromosome inactivation in these cells. They further suggest that reinitiation of transcription of the paternal Pgk-1 allele shortly after fertilization is facilitated by constitutive hypomethylation in the promoter region of this gene throughout spermatogenesis.

PCR-based quantitation of low levels of HIV-1 DNA by using an external standard.

Beginning with 10(3)-10(5) molecules of a purified HIV-1 target sequence as a starting template, we have examined the effects of starting template concentration and cycle number on the amplification efficiency of the polymerase chain reaction. An external standard DNA sequence has been designed that when added to a DNA sample enables a determination of the starting concentration of HIV-1 target sequence in that sample of DNA. Varying ratios of external standard and target DNA sequences were amplified for 22 cycles. When the starting concentration of the external standard was within 50-fold of the starting concentration of the target, the amplifications of both sequences were proportional. These same results were obtained when the two templates were amplified in the presence of an excess of heterogeneous genomic DNA. Using this quantitative method, the number of starting target molecules in a DNA sample can be calculated to within a two-fold range of accuracy.

Technique to locate the end of an endotracheal tube.

The use of metallic spinal instrumentation in the low-cervical and high-thoracic spine can impede radiographic verification of the position of an endotracheal tube. The method described here may be of value in solving this problem.

Routine postpartum treatment of dairy cattle with intrauterine neomycin sulfate boluses.

Within location, 119 dairy cattle from two experiment station herds, which had no problems associated with parturition, were randomly either treated by insertion of two intrauterine boluses containing a total of 1000 mg neomycin sulfate 24 h postpartum or maintained as a control. Uteri and ovaries of all cows were palpated 17 to 24 days postpartum and at 14 day intervals thereafter until inovulation of the uterus was judged complete and an estrus had been observed. All cows were inseminated at the first estrus after 60 days postpartum and at each estrus thereafter until conception. Cows treated with neomycin sulfate required more services per conception (1.7 to 1.4) and were open more days before conception (100.5 to 88.5) than the controls. The probable cause of the lowered reproductive efficiency is discussed. Treatment did not later significantly days to ovulation, estrus, involution, or first service. Three treated and five control animals needed additional uterine treatment. Routine intrauterine treatment of all cows with neomycin sulfate boluses should not be recommended.