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Biomedical subjects

V Baltzopoulos

Publications and source records attributed to V Baltzopoulos.

10 recordsLinked to original sources
PubMed1996

Comparison of gait patterns between healthy and scoliotic patients using time and frequency domain analysis of ground reaction forces.

STUDY DESIGN: The walking gait in 20 healthy adolescent girls and 20 adolescent girls with idiopathic scoliosis was compared using time and frequency domain analysis of the ground reaction forces. OBJECTIVES: To investigate the support phase mechanics of walking gait in health subjects and those with scoliosis. SUMMARY OF BACKGROUND DATA: Previous studies have demonstrated the important role of gait in the etiology of scoliosis, although, to date, there are no detailed reports that examine kinetic gait parameters. METHODS: Selected force-time parameters were used to investigate time domain patterns. The frequency content of the vertical, anterior-posterior, and medial-lateral components was used to examine frequency characteristics. Inter- and intrasubject variability and bilateral symmetry also were examined. RESULTS: The findings indicated no significant difference between the two groups for the time domain variables. However, the frequency content of the group with scoliosis was significantly higher han that of the control group, especially in the medial lateral component, suggesting presence of a balance control misfunction. In addition, substantially higher inter- and intrasubject variability and asymmetry was found within the frequency content of the group with scoliosis compared with the control group in the medial-lateral and anterior-posterior directions. CONCLUSIONS: Patients with scoliosis exhibit balance problems during the stance phase of gait and have significant asymmetry in the frequency characteristics. These findings could be a primary effect that contributes to the medial-lateral deformity of the spine and its initiation and progression.

Adolescent↗
PubMed1996

Muscle tenderness and peak torque changes after downhill running following a prior bout of isokinetic eccentric exercise.

Unaccustomed exercise (usually of an eccentric nature) is often followed by delayed onset muscle soreness (DOMS). Previous studies have found that prior eccentric activity produces a training effect which reduces DOMS and morphological changes. The aim of this study was to examine the effects of a prior bout of maximal isokinetic eccentric exercise on DOMS, strength loss and plasma creatine kinase (CK) changes following a downhill run. Ten male subjects with a mean (+/- S.D.) age of 22.5 +/- 2.8 years, body mass of 62.67 +/- 0.05 kg and height of 176 +/- 3 cm were allocated to either a treatment group or a control group. The treatment group performed 100 maximal eccentric activations of the knee extensors in the dominant leg at 0.52 rad s-1. Two weeks later, the downhill run was performed on a motor-driven treadmill. This consisted of five bouts of 8 min at a gradient of -10% at a speed corresponding to 80% of the predicted maximal heart rate. The untrained group performed the downhill run as above but without the prior isokinetic session. Tenderness measurements, plasma CK activity and concentric and eccentric isokinetic peak torque measurements of the knee extensors at 0.52 and 2.83 rad s-1 were recorded prior to, immediately following and 2, 4 and 7 days after each protocol. The isokinetic protocol caused an increase (P < 0.01) in CK and tenderness and a decrease (P < 0.05) in concentric and eccentric torque at both speeds in the treatment group. Following the downhill run, a reduction in peak torque (P < 0.01) was observed in the eccentric and concentric modes at both isokinetic speeds in the control group. For the treatment group, the decrease in peak torque occurred only at the faster eccentric speed. With the exception of the faster eccentric speed, the decrement in peak torque was greater in the control group in all post-exercise isokinetic strength tests. There was less tenderness (P < 0.01) in the trained knee extensor muscle group. Peak torque also returned to pre-downhill values earlier for the trained group. Although plasma CK activity increased in both groups after downhill running, it was much lower (P < 0.01) in the trained group. The results suggest that a prior bout of isokinetic eccentric training reduces muscle damage, reduces the amount of strength loss and decreases the sensation of DOMS after downhill running.

Adult↗
PubMed1996

Gravitational moment correction in isokinetic dynamometry using anthropometric data.

The purpose of this study was to compare different methods of gravity correction in isokinetic dynamometry. The gravitational moment of the left leg-foot segment of 25 males was measured on a Biodex dynamometer at 30 degrees of knee flexion statically, and as the segment was passively falling from 0 degree to 90 degrees with a constant velocity of 0.035 rad.s-1. The tests were performed in a supine and a seated position. The gravitational moments were also estimated from anthropometric data and directly, using a reaction board method that was considered as the criterion measurement. Furthermore, the isokinetic maximum moment output of the knee flexors and extensors was measured and corrected for gravity using the above methods at angular velocities of 0.52 rad.s-1 and 2.62 rad.s-1 during eccentric, and at 0.52 rad.s-1, 2.62 rad.s-1, and 4.71 rad.s-1 during concentric activations. One-way repeated-measures analysis of variance tests revealed significant differences (P < 0.05) between the gravitational moments obtained on the isokinetic dynamometer and those estimated from anthropometric data or by the reaction board method. The maximum extensor and flexor moments were significantly different, corrected using the gravity correction methods on the dynamometer relative to the anthropometric model or the reaction board (P < 0.05). These results suggest that the determination of gravitational moments based on anthropometric data is more accurate than current gravity correction methods. This new proposed method should be implemented in isokinetic dynamometry applications.

Analysis of Variance↗
PubMed1996

Resistive eccentric exercise: effects of visual feedback on maximum moment of knee extensors and flexors.

One of the most important features of isokinetic dynamometry is the accurate assessment of muscular function. One of the main factors affecting the accuracy of isokinetic parameters during maximum activation efforts is visual feedback. The purpose of this study was the examination of the effects of visual feedback on maximum moment measurements of the knee extensors and flexors during isokinetic eccentric activations. Twenty-five males performed five maximal efforts at angular velocities of 30 degrees/sec and 150 degrees/sec with and without visual feedback on a Biodex dynamometer. Visual feedback was provided as real time display of the moment output. A three-factor analysis of variance test revealed significant differences between the moments recorded with visual feedback and the nonvisual feedback maximum moments of knee extensors and flexors at both speeds. The mean extension peak moments at 30 degrees/sec and 150 degrees/sec under visual feedback condition were approximately 7.2 and 6.4% higher than the nonvisual feedback moments, respectively. The increase for the knee flexor moment was 8.7 and 9% for slow and fast speeds, respectively. These findings suggest that visual feedback can improve maximum eccentric output and should be provided during assessment of maximum eccentric strength on an isokinetic dynamometer.

Adult↗
PubMed1995

Eccentric activation and muscle damage: biomechanical and physiological considerations during downhill running.

An eccentric muscle activation is the controlled lengthening of the muscle under tension. Functionally, most leg muscles work eccentrically for some part of a normal gait cycle, to support the weight of the body against gravity and to absorb shock. During downhill running the role of eccentric work of the 'anti-gravity' muscles--knee extensors, muscles of the anterior and posterior tibial compartments and hip extensors--is accentuated. The purpose of this paper is to review the relationship between eccentric muscle activation and muscle damage, particularly as it relates to running, and specifically, downhill running.

Biomechanical Phenomena↗
PubMed1995

Isokinetic eccentric exercise.

The development of active isokinetic dynamometers has allowed the assessment of muscular moment under eccentric activations that have different characteristics to concentric actions. It is well documented that at a given angular velocity the eccentric moment is greater than the corresponding concentric moment. The moment-velocity relationship under eccentric conditions has been investigated, with conflicting results. Particularly, eccentric moment was reported to remain similar to, or to increase or decrease with, increasing angular velocity. As with concentric actions, the reliability of isokinetic eccentric measurements is influenced by a number of factors such as gravity, preload force and testing position. The velocity-specific effects of eccentric training have not been extensively investigated. Based on current knowledge, eccentric exercise does not appear to be velocity-specific. Although the mode specificity of both concentric and eccentric exercises have been investigated, the resultant observations are conflicting. Eccentric training has been found to improve both concentric and eccentric strength: yet, it has also been reported to improve only concentric or eccentric strength. The reciprocal muscle group ratios under eccentric actions were found not to be influenced by angular velocity, but the significant role of the eccentric/concentric moment ratio of each muscle has not been examined thoroughly. It is well documented that eccentric activations are associated with delayed muscle soreness and muscle damage. A limited number of studies have reported that isokinetic eccentric efforts may result in a lower amount of muscle soreness compared with other exercise modalities. Isokinetic dynamometers provide some unique characteristics for rehabilitation applications. Examination of the clinical application of eccentric exercise is limited. Consequently, the use of this exercise modality in prevention and assessment of musculoskeletal injuries should be investigated further.

Athletic Injuries↗
PubMed1993

Early mobilization after operative repair of ruptured Achilles tendon.

The results of 19 patients in a pilot study in which early mobilization after operative repairs of ruptured Achilles tendons are presented. Serial ultrasound scanning of the repaired tendon showed satisfactory healing. Muscle function was analysed isokinetically and gait symmetry was examined using kinetic analysis. Normal strength of plantarflexion and dorsiflexion was achieved with almost normal range of ankle movement. All patients had normal gait kinetic parameters and symmetry. Normal activities were regained rapidly, and 15 out of 19 patients returned to their pre-injury status. There were no reruptures.

Achilles Tendon↗
PubMed1992

Effect of very low calorie diet on body composition and exercise response in sedentary women.

The effect of very low calorie diet (VLCD) on fat-free mass (FFM) and physiological response to exercise is a topic of current interest. Ten moderately obese women (aged 23-57 years) received VLCD (1695 kJ.day-1) for 6 weeks. FFM, estimated by four conventional techniques, and heart rate (fc), blood lactate (la(b)), mean arterial pressure (MAP), respiratory exchange ratio (R) and rating of perceived exertion (RPE) were measured during a submaximal cycle ergometry test 1 week before, in the 2nd and 6th week, and 1 week after VLCD treatment. Strength and muscular endurance of the quadriceps and hamstrings were tested by isokinetic dynamometry. The 11.5-kg reduction in body mass was approximately 63% fat and 37% FFM. The latter was attributed largely to the loss of water associated with glycogen. Whilst exercise fc increased by 9-14 beats.min-1 (P < 0.01), there were substantial decreases (P < 0.01) in submaximal MAP (1.07-1.73 kPa), la(b) (0.75-1.00 mmol.l-1 and R (0.07-0.09) during VLCD. R and fc returned to normal levels after VLCD. Gross strength decreased (P < 0.01) by 9 and 13% at 1.05 rad.s-1 and 3.14 rad.s-1, respectively. Strength expressed relative to body mass (Nm.kg-1) increased (P < 0.01) at the lower contraction velocity, but there was no change at the faster velocity. Muscular endurance also decreased (P < 0.01) by 62 and 82% for the hamstrings and quadriceps, respectively. We concluded that the strength decrease was a natural adaptation to the reduction in body mass as the ratio of strength to FFM was maintained.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1989

Isokinetic dynamometry. Applications and limitations.

Isokinetic contraction is the muscular contraction that accompanies constant velocity limb movements around a joint. The velocity of movement is maintained constant by a special dynamometer. The resistance of the dynamometer is equal to the muscular forces applied throughout the range of movement. This method allows the measurement of the muscular forces in dynamic conditions and provides optimal loading of the muscles. However, during movements in the vertical plane, the torque registered by the dynamometer is the resultant torque produced by the muscular and gravitational forces. The error depends on the angular position and the torque potential of the tested muscle group. Several methods have been developed for the correction of gravitational errors in isokinetic data. The torque output also contains artefacts that are associated with the inertial forces during acceleration and deceleration periods before the development of the constant preset angular velocity. For an accurate assessment of muscle function, only constant velocity data should be analysed. The most frequently used isokinetic parameters are the maximum torque and the angular position where it was recorded, the torque output at different angular velocities of movement, the torque ratio of reciprocal muscle groups and the torque output during repeated contractions. The unique features of isokinetic dynamometry are optimal loading of the muscles in dynamic conditions and constant preselected velocity of movement. These features provide safety in the rehabilitation of patients with muscular and ligamentous injuries. Isokinetic dynamometry has also been used for the training of various muscle groups in order to improve the muscular performance in dynamic conditions. The movement velocity of different activities can be simulated during training in order to improve the training effect. Data acquisition and analysis have been improved by using computer systems interfaced to isokinetic dynamometers. Recently developed computer systems provide correction for gravitational and inertial errors, accurate computation of isokinetic parameters and real-time display of the torque output.

Biomechanical Phenomena↗