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Biomedical subjects

J M Rothstein

Publications and source records attributed to J M Rothstein.

At least 55 records · Page 3Linked to original sources
PubMed1995

Muscular adaptation to concentric and eccentric exercise at equal power levels.

The effect of training with concentric and eccentric contractions on fiber hypertrophy and isometric torque production was investigated in 20 healthy subjects. One group (eight female and two male subjects) performed concentric contractions of their quadriceps femoris muscles at an intensity of 90% of their maximal concentric power. The other group (six female and four male subjects) performed eccentric contractions at the same relative power level. Both groups exercised three times per week for 4 wk at a constant speed of 60 degrees.s-1 on a Kin-Com dynamometer. Needle biopsies were obtained from the vastus lateralis before and after the exercise program. Fiber-type differentiation was performed using a myosin ATPase stain at a preincubation of 10.5. Maximal isometric knee extension torque was also measured before and after the exercise program. An analysis of covariance was used to determine whether there were significant differences between the exercise groups in: 1) the post-exercise fiber areas and 2) maximal isometric torque (MIso), while controlling for initial differences. Results showed a significant difference between the Type II fiber areas (P < 0.01) and the MIso (P = 0.01). These data indicate that, when exercising at the same relative power level, a subject performing concentric contractions will show greater muscle hypertrophy and improve in MIso production more than a subject training with eccentric contractions.

Adaptation, Physiological↗
PubMed1994

Effect of lordosis on the position of the nucleus pulposus in supine subjects. A study using magnetic resonance imaging.

STUDY DESIGN: Healthy young women (N = 20) underwent magnetic resonance imaging while supine with their hips and knees flexed (flexed position) and supine with a lumbar roll under the low back (extended position). The posterior and anterior margins of the nucleus pulposus (NP) relative to posterior and anterior margins of the adjacent vertebral bodies were calculated from mid-sagittal T2-weighted images to determine the position change of the NP as a function of two supine postures. OBJECTIVES: This study describes the effect of two commonly used supine postures on the position of the NP. SUMMARY OF BACKGROUND DATA: Management of patients with low back pain is often based on theorized positional changes of the NP during spinal extension and flexion. Data describing NP positional changes have not been reported for noninvasive measurements. RESULTS: The distance of the posterior margin of the NP to the posterior margins of the adjacent vertebral bodies was greater in the extended compared with the flexed position. There was no difference in the anterior distance. Eight of the 20 subjects had at least one degenerative disc in the lower lumbar spine. The NPs of the degenerative discs did not move the same as normal discs. CONCLUSIONS: The use of a lumbar roll under the low back when supine causes an increase in the distance from the posterior margin of the NP to the posterior portions of the vertebral bodies in normal discs of healthy young females. Degenerative discs deform differently from nondegenerative discs.

Adult↗
PubMed1994

Say it ain't so.

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Clinical Trials as Topic↗
PubMed1994

Performance characteristics of the Kin-Com dynamometer.

BACKGROUND AND PURPOSE: The purpose of this study was to assess the performance characteristics of a Kin-Com dynamometer (model #500-11) under controlled conditions. METHODS: Comparisons were made between measurements of force, angle, and velocity obtained from the Kin-Com and measurements acquired from an external recording system of known weights, angles, and user-set velocities. The strength of the linear relationships between measurements obtained with the different recording systems was analyzed using a coefficient of determination (r2). An intraclass correlation coefficient (ICC[2,1]) was used to examine the reliability of the force, angle, and velocity measurements obtained with each recording system on 2 different days. RESULTS: In all conditions, the coefficient of determination for the force, angle, and velocity comparisons was above .99. The ICC for between-day comparisons for all force, angle, and velocity measurements was above .99. CONCLUSION AND DISCUSSION: Our results indicate that the static measurements of force and angle that are necessary for use in the gravity-correction procedure and isometric testing are accurate and replicable between days. The Kin-Com dynamometer's control system regulating lever arm velocity is also accurate and replicable under a no-load condition. It was ascertained during the velocity testing that the use of any acceleration and deceleration mode other than "high" resulted in a loss of excursion of the lever arm.

Acceleration↗
PubMed1994

Evaluation of the gravity-correction feature of a Kin-Com isokinetic dynamometer.

BACKGROUND AND PURPOSE: Torques reflecting muscle performance must be corrected for the effects of gravity if error-free ratio-scaled data are to be obtained. Ratio-scaled data are necessary, for example, to report muscle performance characteristics in terms of ratios or percentages or in the form of ratios with another muscle (eg, ratio of hamstring to quadriceps femoris muscle peak torque). The purpose of this study was to determine the error associated with the gravity-correction procedure of the Kin-Com dynamometer when a weight or limb segment is weighed at different lever arm positions. METHODS: A known weight was suspended from the lever arm of the Kin-Com dynamometer. The rotational component of gravitational forces on the weight was measured at 11 different angular positions. We compared the force measurement obtained from the Kin-Com with the predicted rotational component at each angular position. The gravitational forces on a subject's limb segment (leg) were then measured at 12 different angular positions in each of two trunk positions (sitting and supine). We compared the force measurement obtained from the Kin-Com with the predicted rotational component for each position. Forces measured for the two trunk positions with the lever arm horizontal were compared. Forces measured with the knee extended were compared with forces measured with the lever arm horizontal. RESULTS: The dynamometer accurately recorded the rotational component of gravitational forces for the weight suspended from the lever arm. There was a progressively greater discrepancy between measured forces and predicted forces for the leg as the lever arm was moved from horizontal to 50 degrees below the horizontal. The force recorded with the Kin-Com was greater when the subject's knee was in full extension than when the lever arm was horizontal, which placed the subject's knee in a flexed position. A small difference was noted between the measured forces with the lever arm horizontal when the subject was sitting compared with when the subject was positioned supine. CONCLUSION AND DISCUSSION: When weighing a leg with this dynamometer, we recommend that the lever arm be as close to the horizontal position as possible. Positions of proximal joints should be chosen that do not put two joint muscles in stretched positions.

Adult↗
PubMed1994

The relationships among knee extensor torques produced during maximal voluntary contractions under various test conditions.

BACKGROUND AND PURPOSE: The purpose of this study was to describe the relationships among measurements of torque produced during selected maximal voluntary contractions of the quadriceps femoris muscles. SUBJECTS: Twenty nondisabled women, ranging in age from 21 to 33 years (X = 25, SD = 3.5), volunteered to participate in the study. METHODS: The subjects were tested on a dynamometer. Subjects performed isometric contractions at 40 and 60 degrees of knee flexion and concentric and eccentric isokinetic contractions at velocities of 30 degrees, 90 degrees, 120 degrees, and 180 degrees/s. Isometric knee extensor torques, concentric knee extensor peak torques, and eccentric knee extensor peak torques were determined for each subject. Coefficients of determination (r2) and linear regression equations were calculated to determine the strength and nature of the relationships among the measurements. RESULTS: The coefficients of determination ranged from .60 to .94. CONCLUSION AND DISCUSSION: The torque measurements were moderately to highly correlated, suggesting that the measurements obtained during different maximal voluntary contractions may be assessing similar components of performance.

Adult↗
PubMed1994

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Journalism, Medical↗