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Biomedical subjects

Jay Hertel

Publications and source records attributed to Jay Hertel.

At least 19 recordsLinked to original sources
PubMed2007

Fatigue of the plantar intrinsic foot muscles increases navicular drop.

Our purpose was to assess the effect of foot intrinsic muscle fatigue on pronation, as assessed with navicular drop, during static stance. Twenty-one healthy young adults participated. Navicular drop was measured before and after fatiguing exercise of the plantar foot intrinsic muscles. Surface electromyography of the abductor hallucis muscle was recorded during maximum voluntary isometric contractions (MVIC) in order to find the baseline median frequency (MedF). Subjects then performed sets of 75 repetitions of isotonic flexion contractions of the intrinsic foot muscles against a 4.55 kg weight on a custom pulley system. After each set an MVIC was performed to track shifts in MedF. After a MedF shift of at least 10%, navicular drop measurements were repeated. Subjects exhibited 10.0+/-3.8mm of navicular drop at baseline and 11.8+/-3.8mm after fatigue (p<0.0005). The change in navicular drop was significantly correlated with change in MedF (r=.47, p=.03). The intrinsic foot muscles play a role in support of the medial longitudinal arch in static stance. Disrupting the function of these muscles through fatigue resulted in an increase in pronation as assessed by navicular drop.

Adult↗
PubMed2006

Anterior positional fault of the fibula after sub-acute lateral ankle sprains.

Recent evidence has suggested a positional fault of the fibula exists in chronically unstable ankles. However, there has been little research examining positional faults after a sub-acute lateral ankle sprain (LAS). Our purpose was to measure the position of the distal fibula in relation to the distal tibia in subjects with sub-acute LASs and to determine if there is a relationship between the amount of swelling and fibular position. Eleven subjects with a unilateral sub-acute LAS and 11 healthy controls participated. The Wilcoxon signed rank test revealed a significant (p=0.008) difference within the ankles of the injured group. The sprained ankles had a mean fibular position of 14.2+3.4 mm and were positioned significantly more anteriorly than the contralateral uninjured ankles (17.0+3.2 mm). The Mann-Whitney test revealed a significant difference (p=0.045) between the sprained ankle and the side-matched limbs of the controls (16.8+2.3) Pearson product moment correlations revealed a strong positive correlation between fibular position and swelling (r=0.793, p=0.004). Those ankles with more swelling had the most anteriorly positioned fibulae. The fibulae in sub-acutely sprained ankles appear to be positioned more anteriorly compared to the contralateral ankles. This positional fault may be maintained acutely by swelling.

Adult↗
PubMed2006

Neuromuscular performance and knee laxity do not change across the menstrual cycle in female athletes.

Female athletes incur anterior cruciate ligament ruptures at a rate at least twice that of male athletes. Hypothesized factors for the increased injury risk in females include biomechanical, neuromuscular, and hormonal differences between genders. A wealth of literature exists examining these potential predispositions individually, but the interactions between these factors have not been examined extensively. Our purpose was to investigate changes in neuromuscular control and laxity at the knee across the menstrual cycle of healthy females. Fourteen female collegiate athletes with normal, documented ovulatory menstrual cycles, confirmed ovulation, and no history of serious knee injury participated. The presence and timing of ovulation was determined during a screening cycle with ovulation detection kits and during an experimental cycle with collection of daily urine samples and subsequent analysis of urinary estrone-3-glucuronide (E3G) and pregnanediol-3-glucoronide (PdG), which correlate with circulating estrogen and progesterone. Each subject had measures of knee neuromuscular performance and laxity once during the mid-follicular, ovulatory, and mid-luteal stages of her menstrual cycle. The test battery included assessments of knee flexion and extension peak torque, passive knee joint position sense, and postural control in single leg stance. Knee joint laxity was measured with an arthrometer. Analyses of variance revealed that E3G and PdG levels were significantly different across the three testing sessions, but there were no significant differences in the measures of strength, joint position sense, postural control, or laxity. No significant correlations were found between changes in E3G or PdG levels and changes in the performance and laxity measures between sessions. These results suggest that neuromuscular control and knee joint laxity do not change substantially across the menstrual cycle of females despite varying estrogen and progesterone levels.

Adult↗
PubMed2006

Deficits in time-to-boundary measures of postural control with chronic ankle instability.

Our purpose was to examine postural control in single leg stance in subjects with and without unilateral chronic ankle instability (CAI) using traditional center of pressure (COP)-based and time-to-boundary (TTB) measures. Fifteen physically active females with self-reported unilateral chronic ankle instability (CAI) and nine healthy female controls performed three 10-s trials of eyes open single limb quiet standing on a force plate on both their legs. The traditional measures were mean COP velocity, standard deviation of COP, range of COP, and percent of available range utilized. The TTB measures were absolute minimum TTB, mean of the minimum TTB samples, and standard deviation of the minimum TTB samples. All measures were calculated in both the mediolateral (ML) and anteroposterior (AP) directions. A 2x2 group (CAI, control) by side (involved, uninvolved) design was utilized. The CAI group had significantly lower scores for five of the six TTB measures compared to the control group, however only one (AP COP velocity) of the eight traditional measures was different between groups. The TTB measures appear to detect postural control deficits related to CAI that traditional measures do not.

Adult↗
PubMed2006

Time-to-boundary measures of postural control during single leg quiet standing.

A novel approach to quantifying postural stability in single leg stance is assessment of time-to-boundary (TTB) of center of pressure (COP) excursions. TTB measures estimate the time required for the COP to reach the boundary of the base of support if it were to continue on its instantaneous trajectory and velocity, thus quantifying the spatiotemporal characteristics of postural control. Our purposes were to examine: (a) the intrasession reliability of TTB and traditional COP-based measures of postural control, and (b) the correlations between these measures. Twenty-four young women completed three 10-second trials of single-limb quiet standing on each limb. Traditional measures included mean velocity, standard deviation, and range of mediolateral (ML) and anterior-posterior (AP) COP excursions. TTB variables were the absolute minimum, mean of minimum samples, and standard deviation of minimum samples in the ML and AP directions. The intrasession reliability of TTB measures was comparable to traditional COP based measures. Correlations between TTB and traditional COP based measures were weaker than those within each category of measures, indicating that TTB measures capture different aspects of postural control than traditional measures. TTB measures provide a unique method of assessing spatiotemporal characteristics of postural control during single limb stance.

Adult↗
PubMed2006

Mechanical contributions to chronic lateral ankle instability.

Lateral ankle sprains are one of the most common athletic injuries. Even more concerning is the high recurrence rate after an initial sprain. The development of repetitive ankle sprains and persistent symptoms after injury has been termed chronic ankle instability (CAI). One of the purported causes of CAI is mechanical ankle instability (MAI).MAI results in abnormal ankle mechanics. Both hypermobility and hypomobility may change a joint's axis of rotation and result in abnormal joint mechanics. The role of hypermobility, or laxity, has been examined extensively in the literature, but more recently the role of hypomobility has also been examined. There may be a relationship between the two, with implications at the talocrural, subtalar, and inferior tibiofibular joints.Assessment and treatment should focus on both hypermobility and hypomobility and although injury may seem to be isolated to the talocrural joint, the inferior tibiofibular and subtalar joints should also be thoroughly examined.

Ankle Injuries↗
PubMed2006

Fibular position in individuals with self-reported chronic ankle instability.

STUDY DESIGN: Case control study. OBJECTIVES: The purpose of this study was to assess the position of the distal fibula in individuals with chronic ankle instability (CAI). BACKGROUND: Recent literature has suggested that a positional fault of the fibula on the tibia may contribute to CAI; however, there is a lack of objective scientific evidence to support this claim. METHODS AND MEASURES: Thirty subjects with unilateral CAI (mean +/- SD age, 20.3 +/- 1.3 years) and 30 subjects with no previous history of ankle injury (mean +/- SD age, 21.3 +/- 3.8 years) participated in this study. Subjects completed a pair of subjective functional scales and fluoroscopic lateral images of both the right and left ankles were recorded. The distance from the anterior margin of the distal tibia to the anterior margin of the distal fibula was measured in millimeters. Nonparametric statistics were used to assess the relationship between fibular position and CAI status. RESULTS: There were significant differences between the CAI and control group ankles (P = .045) and within the involved and uninvolved sides of the CAI group (P = .006). Those with CAI had a significantly more anterior fibular position on their involved ankle in relation to their uninvolved limb, and the ankles of the control group. CONCLUSIONS: The fibula was positioned significantly more anterior in relation to the tibia in subjects with unilateral CAI. It is unclear if repetitive bouts of ankle instability caused the anterior fibular position or if the more anterior position was a predisposing factor to injury.

Adult↗
PubMed2006

Simplifying the star excursion balance test: analyses of subjects with and without chronic ankle instability.

STUDY DESIGN: Case control study. OBJECTIVES: The objectives of this study are: (1) to perform factor analyses on data from the 8 components of the star excursion balance test (SEBT) in subjects with and without chronic ankle instability (CAI) in an effort to reduce the number of components of the SEBT, (2) to assess the relationships between performance of the different reach directions using correlation analyses, and (3) to determine which components of the SEBT are most affected by CAI. BACKGROUND: The SEBT is a series of 8 lower-extremity-reaching tasks purported to be useful in identifying lower extremity functional deficits. METHODS AND MEASURES: Forty-eight young adults with unilateral CAI (22 males, 26 females; mean +/- SD age, 20.9 +/- 3.2 years; mean +/- SD height, 173.6 +/- 11.1 cm; mean +/- SD mass, 80.1 +/- 22.1 kg) and 39 controls (23 males, 16 females; mean +/- SD age, 20.7 +/- 2.4 years; mean +/- SD height, 174.1 +/- 12.9 cm; mean +/- SD mass, 75.1 +/- 18.6 kg) performed 3 trials of the 8 tasks with each of their limbs. Separate exploratory factor analyses were performed on data for involved limbs of the CAI group, uninvolved limbs of the CAI and control groups, and both limbs of the CAI and control groups. Pearson product moment correlations were calculated to identify the relationships between the different reach directions. A series of eight 2 x 2 analyses of variance were calculated to determine the influence of group (CAI, control) and side (involved, uninvolved) on performance of the 8 tasks. RESULTS: For all 3 factor analyses, only 1 factor in each analysis produced an eigenvalue greater than 1 and the posteromedial reach score was the most strongly correlated task with the computed factor (alpha > .90), although all 8 tasks produced alpha scores greater than .67. Bivariate correlations between specific reach directions ranged from .40 to .91. Subjects with CAI reached significantly less on the anteromedial, medial, and posteromedial directions when balancing on their involved limbs compared to their uninvolved limbs and the side-matched limbs of controls. CONCLUSIONS: The posteromedial component of the SEBT is highly representative of the performance of all 8 components of the test in limbs with and without CAI. There is considerable redundancy in the 8 tasks. The anteromedial, medial, and posteromedial reach tasks may be used clinically to test for functional deficits related to CAI in lieu of testing all 8 tasks. There is a need for a hypothesis-driven study to confirm the results of this exploratory study.

Adolescent↗
PubMed2005

Effect of foot orthotics on quadriceps and gluteus medius electromyographic activity during selected exercises.

OBJECTIVE: To compare electromyographic activity of the vastus medialis, vastus lateralis, and gluteus medius during functional activities in subjects with different foot types while wearing various off-the-shelf foot orthotics. DESIGN: Experimental, controlled; 3 foot-type groups (pes planus, pes cavus, pes rectus) each tested in 4 orthotic conditions while performing 3 different exercises. SETTING: Laboratory. PARTICIPANTS: Thirty healthy young adults, 10 with each foot type. INTERVENTIONS: Four conditions: no orthotic, 7 degrees medial rearfoot post, 4 degrees lateral rearfoot post, and neutral rearfoot post. MAIN OUTCOME MEASURE: Surface electromyographic activity for the vastus medialis, vastus lateralis, and gluteus medius during single-leg squatting, lateral stepdown, and maximum vertical jump exercises. RESULTS: Greater vastus medialis and gluteus medius activity was found with all 3 orthotic conditions, regardless of subject foot type, during the single-leg squat and lateral stepdown. Less vastus lateralis activity was found with the vertical jump with all orthotic conditions, again regardless of foot type. CONCLUSIONS: During slow controlled exercises such as the single-leg squat and lateral stepdown, vastus medialis and gluteus medius activity may be enhanced with an off-the-shelf orthotic, regardless of posting or foot type. These same findings do not appear to carry over to a more explosive task such as the maximal vertical jump.

Adult↗
PubMed2005

Reliability and Sensitivity of the Foot and Ankle Disability Index in Subjects With Chronic Ankle Instability.

Context: Despite the importance of patient's subjective reports of function, little research has addressed their use in the athletic population.Objective: To examine the following measurement properties of the Foot and Ankle Disability Index (FADI) and the FADI Sport: (1) intersession reliability during 1- and 6-week intervals, (2) sensitivity to differences between healthy subjects and subjects with chronic ankle instability (CAI), and (3) sensitivity to changes in function in those with CAI after rehabilitation.Design: Test-retest design.Setting: Laboratory setting.Patients or Other Participants: Fifty recreationally active subjects.Main Outcome Measure(s): FADI and FADI Sport.Results: Intraclass correlation coefficients (ICC 2,1) for the FADI and FADI Sport at 1 week were 0.89 and 0.84, respectively, for the involved limbs. Over 6 weeks, the ICC values for the involved limb of subjects who did not complete rehabilitation were 0.93 and 0.92, respectively. For both surveys, scores were significantly less for the involved limbs of subjects with CAI compared with their uninvolved limbs (P < .05). No significant side-to-side differences were noted among the healthy subjects. Scores on both surveys increased significantly after rehabilitation (FADI: P < .05, effect size = 0.52; FADI Sport: P < .05, effect size = 0.71).Conclusions: The FADI and FADI Sport appear to be (1) reliable in detecting functional limitations in subjects with CAI, (2) sensitive to differences between healthy subjects and subjects with CAI, and (3) responsive to improvements in function after rehabilitation in subjects with CAI.

Journal Article↗
PubMed2004

Effect of lower-extremity muscle fatigue on postural control.

OBJECTIVE: To examine the effects of fatigue of the lower extremity on postural control during single-leg stance. DESIGN: Pretest-posttest. SETTING: University research laboratory. PARTICIPANTS: Fourteen healthy volunteers (age, 21+/-2y) with no history of lower-extremity injury or neurologic deficits. INTERVENTIONS: Testing consisted of isokinetically fatiguing the sagittal plane movers of the ankle, knee, or hip with measures of static postural control. Postural control was assessed with three 30-second trials during unilateral stance with eyes open. MAIN OUTCOME MEASURES: Center of pressure excursion velocity (COPV) in the frontal and sagittal planes. RESULTS: Fatigue at the knee and hip led to postural control impairment in the frontal plane, whereas fatigue at the ankle did not. In the sagittal plane, fatigue at all 3 joints contributed to postural control impairment. CONCLUSIONS: Our results suggest that there is an effect of localized fatigue of the sagittal plane movers of the lower extremity on COPV. It appears that fatigue about the hip and knee had a greater adverse affect on COPV.

Adult↗
PubMed2004

Effect of hip and ankle muscle fatigue on unipedal postural control.

Fatigue and deficits in postural control may predispose musculoskeletal injury. The purpose of this study was to examine the effects of fatigue at the hip and ankle during frontal plane movements on postural control during single-leg stance. Thirteen healthy volunteers completed two testing sessions 1 week apart consisting of isokinetic fatigue of the frontal plane movers of either the ankle or hip with measures of static unipedal postural control taken before and after fatigue. Postural control was assessed during three 30-s trials of unilateral stance with eyes open before and after the fatigue protocol at each testing session. Mean center of pressure (COP) excursion velocity in the sagittal and frontal planes was compared between pre- and post-fatigue across the two joints. Fatigue of the hip musculature led to postural control impairments in the frontal and sagittal planes, while fatigue of the ankle musculature did not significantly impair postural control in either plane. Our results suggest that there is a greater effect of localized fatigue of the frontal plane movers of the hip compared to the ankle on maintenance of a postural control in single-leg stance.

Adult↗
PubMed2004

Bilateral deficits in postural control following lateral ankle sprain.

BACKGROUND: Although postural control deficits have been identified after lateral ankle sprains, objective and subjective comparisons of data before and after injury are limited. The purpose of this project was to prospectively assess and compare the changes in postural control and self-reported functional status in athletes who suffer acute lateral ankle sprains. We evaluated postural control and self-reported functional status before injury and at 1, 7, 14, 21, and 28 days after acute lateral ankle sprain. METHODS: Postural control in single-limb stance and self-reported functional status were evaluated in 460 collegiate athletes during preseason examinations. Twenty-eight athletes suffered a lateral ankle sprain during the competitive season and participated in testing at 1, 7, 14, 21, and 28 days after injury. RESULTS: Significant deficits in postural control were noted in both the injured and the uninjured ankles at 1 day after injury compared to the baseline measurements taken during the preseason examinations. Significant differences (p < .05) also were noted between the uninjured and injured ankles at 1, 7, and 21 days after injury. CONCLUSIONS: After lateral ankle sprain, postural control deficits occur in the injured and uninjured ankles, suggesting a central impairment in neuromuscular control. Changes in self-reported functional status followed a trend of deficit and improvement that was similar to that shown by the postural control data taken after injury, but the two measures did not strongly correlate.

Acute Disease↗
PubMed2004

Changes in postural control during a 48-hr. sleep deprivation period.

Sleep deprivation has detrimental effects on cognitive abilities; however, there has been limited investigation into the effects of sleep deprivation on postural control or influence of time of day on postural control measures. Therefore, we measured postural control on a force plate every 6 hr. in 24 subjects (11 women, 13 men; M age 20 +/- 2.1 yr.; M height 1.68+/-0.29 m; body mass 63.3 +/- 28.7 kg) participating in a 48-hr. dance marathon. During the first 24-hr. period, postural control significantly worsened. Rather than a steady decrease in postural control, during the second day of the event a repeating oscillatory trend of fluctuations in postural control was observed for both days of the event. We hypothesize that the repeating oscillation of postural control followed a circadian rhythm pattern, suggesting that sleep deprivation for 48 hr. does not influence measures of postural control in a consistent manner. The apparent influence of time of day on postural control measures warrants consideration of this factor when conducting studies with repeated measures of postural control across different days.

Adult↗
PubMed2004

Surface Electromyographic Activity of the Abdominal Muscles During Pelvic-Tilt and Abdominal-Hollowing Exercises.

OBJECTIVE: To investigate surface electromyographic (EMG) activity of the rectus abdominus and external oblique abdominus muscles during pelvic-tilt and abdominal-hollowing exercises performed in different positions. DESIGN AND SETTING: 2 x 3 (exercise by position) within-subjects design with repeated measures on both factors. All testing was performed in a university laboratory. SUBJECTS: Twenty-six healthy, active young adult females. MEASUREMENTS: Surface EMG activity was recorded from the left and right rectus abdominus and external oblique muscles while the 2 exercises (pelvic tilt and abdominal hollowing) were performed in different positions (standard, legs supported, and legs unsupported). The standard position was supine in the crook-lying position, the supported position was with hips and knees flexed to 90 degrees and legs supported on a platform, and the unsupported position was with hips and knees flexed to 90 degrees without external support. Peak EMG activity was normalized to a maximum voluntary isometric contraction for each muscle. RESULTS: For the rectus abdominus, there was an interaction between position and activity. Abdominal hollowing produced significantly less activity than the pelvic tilt in all positions. The difference between the 2 exercises with the legs unsupported was of a greater magnitude than the other 2 positions. For the external obliques, there was significantly lower activity during the abdominal hollowing compared with the pelvic tilting. The greatest muscle activity occurred with the legs-unsupported position during both exercises. CONCLUSIONS: Abdominal-hollowing exercises produced less rectus abdominus and external oblique activity than pelvic-tilting exercises. Abdominal hollowing may be performed with minimal activation of the large global abdominal muscles.

Journal Article↗