Detecting altered postural control after cerebral concussion in athletes with normal postural stability.

OBJECTIVE: To determine if approximate entropy (ApEn), a regularity statistic from non-linear dynamics, could detect changes in postural control during quiet standing in athletes with normal postural stability after cerebral concussion. METHODS: The study was a retrospective, case series analysis of centre of pressure (COP) data collected during the Sensory Organization Test (SOT) from NCAA Division I (USA) athletes prior to and within 48 h after injury. Subjects were 21 male and six female athletes from a variety of sports who sustained a cerebral concussion between 1997 and 2003. After injury, athletes displayed normal postural stability equivalent to preseason levels. For comparison, COP data also were collected from 15 male and 15 female healthy non-athletes on two occasions. ApEn values were calculated for COP anterior-posterior (AP) and medial-lateral (ML) time series. RESULTS: Compared to healthy subjects, COP oscillations among athletes generally became more regular (lower ApEn value) after injury despite the absence of postural instability. For AP time series, declines in ApEn values were much larger in SOT conditions 1 and 2 (approximately three times as large as the standard error of the mean) than for all other conditions. For ML time series, ApEn values declined after injury in all sensory conditions (F(1,55) = 6.36, p = 0.02). CONCLUSIONS: Athletes who demonstrated normal postural stability after concussion nonetheless displayed subtle changes in postural control. Changes in ApEn may have represented a clinically abnormal finding. ApEn analysis of COP oscillations may be a valuable supplement to existing concussion assessment protocols for athletes.

Ruptures of the pectoralis major muscle. An anatomic and clinical analysis.

We evaluated 12 patients with 14 ruptures of the pectoralis major muscle to compare surgical and conservative management of this injury. Because 9 of the injuries occurred while weight lifting, we performed an anatomic study on human hemithorax specimens during a simulated bench press to determine the mechanism of this rare occurrence. Excursion of individual pectoralis muscle fibers was measured at seven points along the broad muscle origin by the use of fine wires connected to the humeral insertion and to dial gauges on the study apparatus. Excursions in the concentric and eccentric phases of the lift were expressed as a percentage of resting fiber length. The short, inferior fibers of the muscle lengthened disproportionately during the final 30 degrees of humeral extension. We concluded that the inferior fibers have a mechanical disadvantage in the final portion of the eccentric phase of the lift, and application of high loads to these maximally stretched fibers produces rupture. We repaired five acute and two chronic ruptures, and measured peak torque and work production against the contralateral side using Cybex isokinetic testing. Surgically treated patients showed comparable torque and work measurements, while conservatively treated individuals demonstrated and marked deficit in both peak torque and work/repetition. We recommend repair of complete pectoralis muscle ruptures in active patients who require maximum strength in vocational or avocational activities.

Kinematic characterization of standing reach: comparison of younger vs. older subjects.

OBJECTIVE: To characterize typical spinal motions that occur during standing reach and to describe differences in spinal motions and center of pressure displacements during reach between younger and older healthy adults. DESIGN: Exploratory, cross sectional investigation utilizing video motion and biomechanics force platform analysis. BACKGROUND: Standing reach provides a means for assessing both arm function and balance control in the context of a common functional activity. The interaction between age-related declines in spinal mobility and the spinal motion occurring during reach is poorly understood. The characterization of spinal motions during task performance for healthy subjects of different age groups is an important first step for understanding the relationship between impairments and physical performance in disabled populations. METHODS: Thirty-four subjects ages 20-36 and 33 subjects ages 60-76 participated. Video motion and force plate analysis were used to characterize spinal motion and center of pressure displacements during the functional reach test for younger and older subjects. RESULTS: Spinal motion during standing reach was characterized by forward trunk flexion, lateral trunk flexion, thoracolumbar rotation, and lower body rotation. Younger and older subjects differed (P = 0.05) in the amount of forward trunk flexion and thoracolumbar rotation which occurred but not lower body rotation. Younger subjects displaced their center of pressure further forward (P = 0.0001) and through a greater percentage of their initial base of support (P = 0.0001) than older subjects. CONCLUSION: This study provides the first multiplanar characterization of spinal motion used during standing reach. Significant differences for a number of variables existed between younger and older subjects.

Short crank cycle ergometry.

The change in knee angle during cycling was mathematically analyzed. It was determined that if the crank length of the cycle ergometer was shortened, the arc of knee motion necessary to cycle could be reduced. A computer program was written to represent the above mathematical model utilizing a patient's lower limb lengths to generate an individualized, range of motion profile. A custom cycle ergometer was built with interchangeable crank lengths of 80 mm, 110 mm, 140 mm, and 170 mm. This device can be adjusted to achieve a desired range of motion for a specific patient. The above custom cycle ergometer can be used on early postoperative knee patients who are unable to ride a conventional cycle ergometer because of a lack of knee motion or on patients who require a limited arc of motion in their postoperative therapy protocol. J Orthop Sports Phys Ther 1991;13(2):95-100.

Which measures of physical function and motor impairment best predict quality of life in Parkinson's disease?

INTRODUCTION: Our objective was to compare the relative value of elements of the motor system in predicting the physical mobility domain of health related quality of life in patients with Parkinson's disease in order to specify targets for intervention. METHODS: In this cross-sectional study, the Parkinson's disease questionnaire-39 was administered to 263 subjects with Parkinson's disease to assess health related quality of life. Demographics, motor impairments and physical function were assessed using the Unified Parkinson disease rating scale, 10-m walk test, 6-min walk test, Freezing of gait questionnaire, Timed up & go, functional gait assessment, Berg balance test, functional reach and 9-hole peg test. RESULTS: The results revealed that demographic factors accounted for 19.7% of the variance in Parkinson disease questionnaire-39 mobility score. When motor impairments were added to the model, the bradykinesia composite score contributed a significant portion of the variance (R(2) change = 0.12, p < 0.001). The tremor and rigidity composite scores did not contribute significantly. The Freezing of gait questionnaire was the strongest predictor (R(2) change = 0.23, p < 0.001) of the physical function tests followed by Functional gait assessment (R(2) change = 0.06, p < 0.001) and 6-min walk test (R(2) change = 0.01, p = 0.01). Collectively, 61% of the variance in Parkinson disease questionnaire-39 mobility score and 41.5% of the Parkinson disease questionnaire-39(total) score was accounted for. DISCUSSION: These results suggest greater value of physical function tests, and not tests of motor impairments, in predicting health related quality of life.