Relationship between hip muscle imbalance and occurrence of low back pain in collegiate athletes: a prospective study.

OBJECTIVE: To assess whether athletes with strength imbalance of the hip musculature would be more likely to require treatment for low back pain (LBP) over the ensuing year. DESIGN: The study population included 163 National Collegiate Athletic Association Division I college athletes (100 males and 63 females) undergoing preparticipation sports physicals. Institutional review board approval was obtained to acquire and analyze hip muscle strength data. A commercially available dynamometer (Chatillon, Lexington, KY) incorporated into a specially designed anchoring station was used for testing the hip extensors and abductors. The maximum force generated for the hip abductors and extensors was used to calculate a percentage difference between the right and left hip extensors and abductors. Treatment of athletes by the athletic trainers for LBP unrelated to blunt trauma over the ensuing year was recorded. RESULTS: Of all athletes, 5 of 63 females and 8 of 100 males required treatment for LBP. Logistic regression analysis indicated that for female athletes, the percentage difference between the right and left hip extensors was predictive of whether treatment for LBP was required over the ensuing year (P = 0.05). There was no significant association noted for the percentage difference between the right and left hip abductors in females and for the percentage difference between both the right and left hip abductors and right and left hip extensors in males requiring treatment for LBP. CONCLUSIONS: These data support our results from our previous cohort study, adding validity to the concept of hip muscle imbalance being associated with LBP occurrence in female athletes. This research further supports the need for the assessment and treatment of hip muscle imbalance in individuals with LBP.

Effect of topical heat on electromyographic power density spectrum in subjects with myofascial pain and normal controls: a pilot study.

OBJECTIVE: To investigate the influence of superficial heat on the fatigue cascade of the upper trapezius muscle in subjects with myofascial pain and matched normal controls. DESIGN: In a prospective randomized block crossover pilot study, eight female subjects, ages 20-35 yr, with upper trapezius muscle trigger points and eight matched female control subjects without pain were studied. Subjects performed six 100-sec shoulder shrug contractions to fatigue, with subjects randomly chosen to receive heat during the first three or last three trials. The initial median frequency and the slope of the median frequency decline were calculated from the data. RESULTS: In the subjects with pain, the slope of the median frequency was elevated in ambient room temperature as compared with controls. There was no difference in slope of the median frequency under heated conditions. Heat application in controls before fatiguing exercise caused an increase in initial median frequency, whereas exercise before heat treatment resulted in a significantly lower initial median frequency. Subjects with myofascial pain had no significant change in initial median frequency. CONCLUSIONS: Heat seems to have a positive effect on muscle function in normal individuals when applied before exercise. Subjects with myofascial pain respond differently to exercise and heat challenge, which suggests a difference in their muscle physiology.

A study of thyrotropin-releasing hormone for the treatment of spinal muscular atrophy: a preliminary report.

OBJECTIVE: To determine whether thyrotropin-releasing hormone (TRH) can increase muscle strength in children with spinal muscular atrophy types 2 and 3. DESIGN: A randomized, double-blinded, controlled, 5-wk drug trial of six subjects and three controls. Subjects and controls ranged from 4 to 8 yr of age and were randomly assigned to treatment and placebo groups in a ratio of 2:1. TRH (protirelin) or placebo was delivered intravenously through percutaneous intravenous catheters at a dose of 0.1 mg/kg (in 50 ml of normal saline) for a total of 29 days. Patients were evaluated using electromyography and handheld dynamometry of the deltoids, biceps, triceps, wrist extensors, hip flexors, quadriceps, hamstrings, and grip strength before and immediately after 5 wk of treatment. A unidirectional t test was used to compare mean values. RESULTS: Dynamometry improved significantly only for the six treated subjects (P < 0.02). Peroneal nerve conduction velocities were significantly faster in the treatment group (paired t test, P = 0.036). The parents of the treated children also provided anecdotal evidence of improvements in function. Improvements lasted 6-12 mo. CONCLUSIONS: TRH may be a useful treatment for spinal muscular atrophy. A larger, crossover design group comparison study is warranted.

Portable dynamometer anchoring station for measuring strength of the hip extensors and abductors.

OBJECTIVE: To assess the reliability of a specially designed dynamometer anchoring station in the measurement of hip muscle strength. DESIGN: Prospective study using test-retest design. SETTING: Outpatient clinic setting. PARTICIPANTS: Ten subjects, ages 25 to 35yrs. MAIN OUTCOME MEASURES: Using the apparatus, three consecutive measures were recorded for hip abduction and extension by an inexperienced examiner. Two weeks later, the same subjects were retested, with the evaluator blinded to the initial results. In both the test and retest, average and maximal values of strength were calculated for each muscle. Reliability of the device was assessed by computing the intraclass correlation coefficients and coefficients of variation (CVs). RESULTS: Intraclass correlation coefficients ranged from .94 to .98. The average CV for the maximal and average abduction strength had values of 4.77% and 4%, respectively. The maximal and average extension strength had average CV values of 8.06% and 7.83%, respectively. CONCLUSION: This specially designed dynamometer anchoring station has been found to be highly reliable in the measurement of hip girdle strength and has the advantage of easy adjustability and portability for large-scale screenings. This device enhances the reliability of the dynamometer, which may be subject to considerable variability when applied by hand to the powerful hip girdle musculature.

The relationship between lower extremity injury, low back pain, and hip muscle strength in male and female collegiate athletes.

OBJECTIVE: To determine the relationship of previous lower extremity (LE) injury and/or low back pain (LBP) on hip abduction and extension strength. DESIGN: Cohort study of college athletes at time of preparticipation screening physical. SETTING: An NCAA Division I college. PARTICIPANTS: Two hundred ten college athletes (140 males and 70 females) from an NCAA Division I school. MAIN OUTCOME MEASURES: Mean and maximal hip abduction and extension strengths were recorded using a specially designed dynamometer anchoring station. Previous injury to the LE or LBP in the past year was recorded via personal interview at the time of screening and verified by review of previous injury records. RESULTS: A significant difference in side-to-side symmetry of maximum hip extension strength was observed in female subjects who reported LE injury or LBP as compared to those who did not. Side-to-side difference in hip strength, however, did not differ between male athletes, regardless of reported LE injury or LBP status. CONCLUSION: Female athletes appear to have a differing response of the proximal hip musculature to LE injury or LBP, as compared with their male counterparts. Research is under way to further validate these findings. CLINICAL RELEVANCE: This study provides some reasoning to support the screening of hip strength during the preparticipation physical, as it may be important in the prevention of LE injury and LBP in collegiate athletes.