Tehran University Medical Journal

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The aim of this investigation is to compare the effect of applying two transcutaneous electrical nerve stimulation (TENS) current with different frequencies (2 Hz & 100 Hz) on Hoffmann reflex recorded from gastrosoleus muscle of healthy people. Forty female subjects between 20 to 30 years of age were participated in this quasi-experimental design. Twenty of them were exposed to the 100 Hz current and the remaining 20 to 2 Hz current on dermatome S1 root. The excitability of the alpha motoneurone was measured by H-reflex amplitude (peak to peak max/2) before and after the application of the TENS current for 30 minutes. The reflex was recorded and at measured before (TO) and after the application of TENS at different times (T1, T% and T10) up to 10 minutes. The mean values were compared by multiple paired T test (alpha=0.00825). The results indicate a considerable decrement in Hoffmann reflex amplitude after application of 100 Hz current in comarison with that of before the application. The effect last for 10 minutes after the TENS application, whereas the application of 2 Hz current results in increment of the Hoffmann reflex amplitude. The 5 and 10 minutes interval test dose not show any significance and the results were attenuated befor 5 minutes. As a conclusion high frequency of TENS (100 Hz) has an inhibitory effect on excitability of alpha motor neurone reflex lasting for 10 minutes, while low frequency of TENS (2 Hz) has an facilatory effect on the same motoneurone with short lasting effect.

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The aim of this investigation is to compare the effect of applying two transcutaneous electrical nerve stimulation (TENS) current with different frequencies (2 Hz & 100 Hz) on Hoffmann reflex recorded from gastrosoleus muscle of healthy people. Forty female subjects between 20 to 30 years of age were participated in this quasi-experimental design. Twenty of them were exposed to the 100 Hz current and the remaining 20 to 2 Hz current on dermatome S1 root. The excitability of the alpha motoneurone was measured by H-reflex amplitude (peak to peak max/2) before and after the application of the TENS current for 30 minutes. The reflex was recorded and at measured before (TO) and after the application of TENS at different times (T1, T% and T10) up to 10 minutes. The mean values were compared by multiple paired T test (alpha=0.00825). The results indicate a considerable decrement in Hoffmann reflex amplitude after application of 100 Hz current in comarison with that of before the application. The effect last for 10 minutes after the TENS application, whereas the application of 2 Hz current results in increment of the Hoffmann reflex amplitude. The 5 and 10 minutes interval test dose not show any significance and the results were attenuated befor 5 minutes. As a conclusion high frequency of TENS (100 Hz) has an inhibitory effect on excitability of alpha motor neurone reflex lasting for 10 minutes, while low frequency of TENS (2 Hz) has an facilatory effect on the same motoneurone with short lasting effect.

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Background: The purpose of this study was to measure isokinetic maximum and average peak torque of internal and external rotators of glenohumeral joint in volley ball and tennis players
Methods: This study was performed on 17 professional female athletes (7 tennis players &10 volleyball players) with age ranged 18-28 years. The subjects had played in a skilled team for more than 3 years. They were free from injury to their dominant shoulder in the past year. Subjects performed a five minute warm up by shoulder wheel and Maximum average Peak Torque (APT) were obtained unilaterally by a Biodex System 3 with the arm of players in 90 degree abduction at 120,180 & 210 o/s. Players performed five trails of concentric movements with 30 second rest between them.
Results: Maximum and average of maximum torques of shoulder rotator, in both groups, expect for internal rotators of tennis players, reduced by increase of movement speed (P<0.05). There are not significant difference between two groups in maximum, average of maximum torques and normalized data (ratio of maximum torque to weight). There is significant difference between two groups in percentage of APT of External rotator / Internal rotator ratio at 210 o/s (P<0.05).
Conclusion: Volleyball and tennis have no effect on isokinetic strength of shoulder rotators. In high speed, ratio of External rotator / Internal rotator is reduced. This indicates that increase in movement speed increase internal rotator in comparison to external rotator in these professional female athletes.

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Background: Both isokinetic testing and functional tests are commonly used to evaluate anterior cruciate ligament reconstructed (ACLR) patients. The object of this study was to evaluate motor performance of the knee and determine the relationship of isokinetic test scores to scores on a variety of lower extremity functional tests.
Methods: Ten healthy subjects and eleven ACLR patients at least six months after surgery performed the following: knee isokinetic tests at 60 and 180 deg/sec three functional tests including leg vertical jump, single hop, and triple cross-over hop for distance. The International Knee Document Committee Subjective Knee Evaluation Form (IKDCSKEF) was used to score the self-assessment of each study participant. Paired T-test was used to compare the involved and uninvolved knee. Pearson correlation coefficients were used to determine the relationship between the scores on the isokinetic test and functional tests. Significance was determined by P<0.05.
Results: IKDCSKEF score was significantly lower in patients than control subjects. Quadriceps peak torque and functional test scores were significantly lower in the involved knee of the ACLR subjects compared to the uninvolved knee. Correlation coefficients of isokinetic peak torque to body weight and functional testing were not significant in patients or control subjects, whi1e the limb symmetry index (LSI) of the quadriceps isokinetics peak torque to body weight and the LSI of the functional tests were significant (r = 0.54 to 0.97).
Conclusion: These results indicate a significant relationship between the LSI of various functional tests and the LSI of isokinetic testing among ACLR patients. Thus, in situations where an isokinetic dynamometer is not available, the LSI of functional tests can be used to estimate quadriceps deficiency for ACLR patients.

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Background: The changes in motor control after the use of a supportive belt can contribute to the understanding of its effects on performance. The aim of this study is to quantify motion pattern values relative to the spinal column during the use of a lumbosacral belt.
Methods: For fifty healthy female volunteers, the range of motion, maximum isometric torque and changes of phase angle of maximum torque and velocity in two positions, standing and sitting, in two directions, flexion and extension, following the use of a lumbosacral belt were measured using an isoinertial dynamometer (Isostation B200) and compared.
Results: Range of motion in both directions in both positions was reduced significantly (P<0.05). Significant reduction of maximum isometric torque was observed in flexion while sitting and in extension while standing and sitting (P<0.05). Phase angle of maximum torque and velocity also changed significantly in both directions and both positions (P<0.05).
Conclusion: The lumbosacral belt can act in different ways to prevent injury. It reduces the forces applied to lumbar vertebra and, by changing the maximum torque and velocity phase angles at the onset of range of motion, provides greater stability for joints. Furthermore, the belt can reduce stress imposed on the posterior joints of the spine and limits several momentary forces at the onset of joint movement. Under these conditions, joint injuries can be reduced and prevent some of the mechanical stress that causes lumbar joint disease.