Biomedical subjects

E Isakov

Publications and source records attributed to E Isakov.

At least 19 recordsLinked to original sources

PubMed2006

Gait rehabilitation: a new biofeedback device for monitoring and enhancing weight-bearing over the affected lower limb.

AIM: Gait rehabilitation programs often require either partial weight-bearing (PWB) or encourage full weight-bearing (FWB) on the affected limb. Until recently, there was no objective and practical way to measure correct weight-bearing during ambulation. The present study evaluates a new in-shoe device (SmartStep, Andante Medical Devices Ltd.) for measuring the amount of weight on the affected limb and for biofeedback gait training. METHODS: The first part of the study aimed to establish the validity of the SmartStep by comparing the results obtained from this device with the results obtained from a force plate. The second part aimed to evaluate the effectiveness of the SmartStep as a biofeedback method in patients who have been referred for FWB gait rehabilitation. Analysis was based on independent samples t-test and chi squared test for evaluating statistically significant differences between the 2 gait rehabilitation modes. RESULTS: The SmartStep could repeat the same results with 0.53 kg error of mean. Statistically significant correlation was found between results obtained from the SmartStep and from the force plate (R2=0.9067 and P=0.004). The use of the SmartStep auditory biofeedback, significantly (P=0.00031) improved patients' weight-bearing over the affected limb in the experimental group (7.9 kg +/-5.28) as compared to the control group (0.7+/-2.41 kg). CONCLUSIONS: The SmartStep proved to be very reliable since it generated significant repeatable results which correlated significantly with those obtained from a force plate. Patients recommended for FWB gait can significantly improve body weight loading over the affected limb by the use of the SmartStep auditory biofeedback.

Aged↗

PubMed2006

Muscle enhancement using closed-loop electrical stimulation: volitional versus induced torque.

In cases of partial deficiency of muscle activation capacity, force augmentation can be achieved by hybrid activation, i.e., by combining electrical stimulation (ES) with volitional activation. In this activation modality the shares of the volitional and induced torques within the overall hybrid torque are unknown. The purpose of this study was to suggest a computational approach to parcel out the volitional and stimulation induced components of joint torque generated during combined voluntary and electrical activation of the Tibialis Anterior muscle (TA). For this purpose, isometric contraction of the TA was studied on 5 healthy subjects, using an activation protocol involving ES alone, volitional activation alone and hybrid activation. Ankle torque and TA EMG were measured. A computational algorithm was developed to dissociate the volitional from the overall torque, based on EMG filtering and on pre-measured calibration curves of volitional torque versus EMG. The results indicated that for a certain hybrid torque there is a linear decaying relationship between the induced torque and the volitional torque shares. Moreover, based on a defined enhancement ratio, the results indicate that within the range of stimulation intensities, there exist regions of increased facilitation, in which the stimulation efficiency is higher under combined compared to isolated conditions.

Adult↗

PubMed2004

Improving functional skills and physical fitness in children with Rett syndrome.

BACKGROUND: To investigate the feasibility of a physical exercise programme with treadmill for persons with Rett syndrome (RS) in order to promote fitness and health. METHODS: A daily training programme on a treadmill was designed for four females with RS over a period of 2 months with tests performed in three intervals, at time 1, 2 and 3, 2 months apart with intervention taking place between tests 2 and 3. Participants were four girls with RS aged 8.5-11 years (mean: 10 years) attending the educational facility Beit Issie Shapiro, Raanana, Israel, all with independent mobility and with typical characteristics of RS stage III. The training took place at the educational facility, on a 1400 model treadmill (Trimline, capable of very low speeds < 0.5 k/h), with very long side rails. Special low side rails were adapted to the treadmill in order to fit the height of the children and velcro straps were added to assist in safely placing the hands. Pulse was monitored constantly during exercise by an A3 polar pulse belt. Pulse measurements at rest during training were considered as evaluators of aerobic physical condition. Functional measurement was based on a scale specially established for the present study. The scale was a 31-item motor-functioning tool that measures the ability of participants to knee walk and knee stand, to get up to a standing position, duration of walking different paths, and to go up and down stairs and slopes. RESULTS: The study showed that physical fitness of the children at the end of the training programme had improved considerably (P < 0.05). Tests showed that general functional abilities had improved considerably (P < 0.0001). Although all items of the functional ability measure showed impressive positive change, some of the 31 items on it showed statistically significant improvement (knee walking, going up and down stairs and speed of walking for 25 m. Pearson correlation showed high linkage (r = -0.76) between functional improvement and change in physical fitness. CONCLUSIONS: Physical fitness programme executed on a daily basis is capable of improving functional ability of children with RS. Nonprofessional personnel can execute such a programme under supervision of a qualified physical therapist.

Activities of Daily Living↗

PubMed2003

The influence of prosthetic foot alignment on trans-tibial amputee gait.

An optimally aligned prosthesis, as accomplished by the subjective judgment of the prosthetist, guarantees the best quality of gait. Yet, amputees can adapt to a large variety of geometrical configurations of the prosthetic components. Different external rotation angles of the foot in trans-tibial (TT) prostheses were investigated. The study tried to identify (a) the relationship between foot angle and other gait parameters and (b) the compensating pattern of the amputees to excessive external rotation of the foot. Eight (8) TT amputees, fitted with an identical type of prosthesis, were investigated during ambulation. The prosthetic foot was externally rotated as follows: optimal angle (10.94 x degrees +/- 5.21 degrees), optimal angle plus another 18 degrees, and optimal angle plus another 36 degrees. Analysis of gait was performed with the aid of an electronic walkway. Speed of gait, stance and swing time, and foot angle were monitored in 4 runs for each of the three foot angles. Speed of gait remained almost constant in the three tests. Stance and swing time, as well as step length, significantly changed when 36 degrees were added to the optimal foot angle. This foot position significantly influenced inter-legs time difference and symmetry between the legs. During ambulation, prosthetic foot external rotation was decreased by internal rotation of the limb at the hip joint level. It is concluded that TT amputees can maintain an efficient speed of gait even when the prosthetic foot is malpositioned in excessive external rotation. Although such a malalignment significantly influences other gait parameters during walking, amputees are able to adapt themselves by internal rotation of the hip joint in the amputated leg.

Adult↗

PubMed2001

Fatigue-induced changes in decline running.

OBJECTIVE: Study the relation between muscle fatigue during eccentric muscle contractions and kinematics of the legs in downhill running. DESIGN: Decline running on a treadmill was used to acquire data on shock accelerations, muscle activity and kinematics, for comparison with level running. BACKGROUND: In downhill running, local muscle fatigue is the cause of morphological muscle damage which leads to reduced attenuation of shock accelerations. METHODS: Fourteen subjects ran on a treadmill above level-running anaerobic threshold speed for 30 min, in level and -4 degrees decline running. The following were monitored: metabolic fatigue by means of respiratory parameters; muscle fatigue of the quadriceps by means of elevation in myoelectric activity; and kinematic parameters including knee and ankle angles and hip vertical excursion by means of computerized videography. Data on shock transmission reported in previous studies were also used. RESULTS: Quadriceps fatigue develops in parallel to an increasing vertical excursion of the hip in the stance phase of running, enabled by larger dorsi flexion of the ankle rather than by increased flexion of the knee. CONCLUSIONS: The decrease in shock attenuation can be attributed to quadriceps muscle fatigue in parallel to increased vertical excursion of the hips.

Adult↗

PubMed2001

Knee muscle activity during ambulation of trans-tibial amputees.

Gait analysis of trans-tibial amputees brings to light asymmetries of different gait parameters between the amputated and sound legs. The present study investigated the activity of the vastus medialis and biceps femoris muscles during ambulation of trans-tibial amputees. Peak activities of the vastus medialis were reached similarly in both legs (6.06+/-4.9% and 8.84+/-3.6% of gait cycle, in the sound and amputated leg, respectively). Biceps femoris peak activities were reached at 92.43+/-6.6% of gait cycle in the sound leg, and significantly later (at 9.81+/-4.8% of gait cycle) in the amputated leg (p < 0.05). Integrated EMG activity ratios, between swing and stance periods, were similar for the vastus medialis (0.33 in the sound and 0.35 in the amputated leg). However, these ratios differed significantly for the biceps femoris since the amputated leg presented a substantial (p < 0.05) smaller ratio (0.22) compared with the sound leg (0.83). The use of prosthesis in trans-tibial amputees requires further activity of the biceps femoris during stance period to improve support of the amputated leg knee joint.

Adult↗

PubMed2000

Shock accelerations and attenuation in downhill and level running.

OBJECTIVE: A study was conducted to investigate the possible effects of fatigue on the heel strike-initiated shock accelerations and on attenuation of these shocks along the body during eccentric muscle contractions. DESIGN: Level and decline running on a treadmill were used to acquire the experimental data on the foot strike-initiated shock accelerations. BACKGROUND: Eccentric contractions of the lower limb muscles in combination with shock generation and propagation during downhill running and muscle fatigue may diminish their ability to dissipate and attenuate loading on the system. METHODS: Fourteen young healthy males ran on a treadmill at a speed exceeding their anaerobic threshold by 5% for 30 min, as follows: (a) level running and (b) downhill running with a decline angle of -4 degrees. The foot strike-induced shock accelerations were recorded every five minutes on the tibial tuberosity and sacrum. Fatigue was monitored by means of the respiratory parameters. RESULTS: The downhill running related with eccentric muscle contractions was associated with increased shock propagation from the tibial tuberosity to the sacrum levels, even though fatigue did not develop. CONCLUSIONS: Shock propagation from the tibial tuberosity to the sacrum is augmented due to the eccentric action of the muscles, without metabolic fatigue development. RELEVANCE: Eccentric muscle contraction in downhill running reduces the musculoskeletal ability to attenuate the heel strike-induced shock waves. Knowledge about the effect of fatigue on the shock propagation between the shank and the sacrum levels may help in understanding the mechanism of stress fractures and joint damage.

Acceleration↗

PubMed2000

Transcutaneous FES of the paralyzed quadriceps: is knee torque affected by unintended activation of the hamstrings?

This study addresses the question whether unintended response of the knee flexors (hamstrings) accompanies transcutaneous functional electrical stimulation (FES) of the quadriceps and whether the knee torque is hereby affected. Transcutaneous FES of the right quadriceps of two paraplegic subjects was applied and measurements were made of the net torque and of the myoelectric activities of the quadriceps and hamstrings muscles of the right leg. A low correlation was obtained between the peak-to-peak amplitudes of the M-waves of the two muscles. This correlation decreased further with the development of fatigue, which indicated that the electromyography (EMG) signals from the hamstrings were not the result of cross-talk between adjacent recording sites. The force profile of each muscle was determined from a developed model incorporating EMG-based activation, muscle anthropometry as obtained from in vivo magnetic resonance imaging of the thigh, and metabolic fatigue function, based on data acquired by 31P nuclear magnetic resonance spectroscopy. A sensitivity analysis revealed that the muscle specific tension and the muscle moment arms have a major influence on the resulting muscle forces and should therefore be accurately provided. The results show that during the unfatigued phase of contraction the estimated maximal force in the hamstrings was lower than 20% of that in the quadriceps and could be considered to be practically negligible. As fatigue progressed the hamstrings-to-quadriceps force ratio increased, reaching up to 45%, and the effect of co-activation on the torque partition between the two muscles was no longer negligible.

Adult↗

PubMed2000

Trans-tibial amputee gait: time-distance parameters and EMG activity.

Gait analysis of trans-tibial (TT) amputees discloses asymmetries in gait parameters between the amputated and sound legs. The present study aimed at outlining differences between both legs with regard to kinematic parameters and activity of the muscles controlling the knees. The gait of 14 traumatic TT amputees, walking at a mean speed of 74.96 m/min, was analysed by means of an electronic walkway, video camera, and portable electromyography system. Results showed differences in kinematic parameters. Step length, step time and swing time were significantly longer, while stance time and single support time were significantly shorter on the amputated side. A significant difference was also found between knee angle in both legs at heel strike. The biceps femoris/vastus medialis ratio in the amputated leg, during the first half of stance phase, was significantly higher when compared to the same muscle ratio in the sound leg. This difference was due to the higher activity of the biceps femoris, almost four times higher than the vastus medialis in the amputated leg. The observed differences in time-distance parameters are due to stiffness of the prosthesis ankle (the SACH foot) that impedes the normal forward advance of the amputated leg during the first half of stance. The higher knee flexion at heel strike is due to the necessary socket alignment. Unlike in the sound leg, the biceps femoris in the amputated leg reaches maximal activity during the first half of stance, cocontracting with the vastus medialis, to support body weight on the amputated leg. The obtained data can serve as a future reference for evaluating the influence of new prosthetic components on the quality of TT amputee's gait.

Adult↗

PubMed2000

Isokinetic strength and endurance of the knee extensors and flexors in trans-tibial amputees.

Significant levels of muscular fatigue alter the co-ordination patterns and the ability to accomplish proper daily functions, especially in patients with initial low levels of strength. The purpose of this study was to evaluate the strength and endurance of the quadriceps and hamstring muscles in trans-tibial amputees. Concentric strength and endurance of the thigh muscles were measured bilaterally by an isokinetic dynamometer. The measured variables were torque and angle. For the endurance test, a fatigue index was calculated. Peak torque for extension and flexion was significantly higher in the sound limb (p<0.01). The fatigue index for extension was not significantly different in the sound limb from the amputated limb. The fatigue index for flexion is significantly higher in the sound limb (p<0.01). The finding may imply that from a metabolic point of view, the muscles of the amputated limb function properly. It is of great importance to reduce the bilateral deficit and the degree of atrophy as soon as possible in order to improve the level of performance. By choosing a correct strength and endurance training programme, one may expect to get a significant and good reaction from the muscles of the amputated limb as is expected from training the muscles of a sound limb.

Adaptation, Physiological↗

PubMed2000

Fatigue-related loading imbalance on the shank in running: a possible factor in stress fractures.

In previous reports we have shown that in long distance running the impact acceleration on the shank increases with progressing fatigue. The aim of the present study was to test whether, in parallel to this increase, an imbalance in the activities between the ankle plantar and dorsi flexor muscles develops. The tests were made on fourteen subjects during 30 min treadmill running above their anaerobic thresholds. Respiratory data were collected to determine the anaerobic threshold speed and to indicate the progressively developing metabolic fatigue. Surface electromyogram (EMG) was monitored to indicate the changing activity of the shank muscles. In the tibialis anterior the average integrated EMG (iEMG) and the mean power frequency (MPF) significantly decreased from the beginning to the end of running. In the gastrocnemius iEMG did not change, while MPF increased during the course of running. The impact acceleration, measured by means of an accelerometer attached to the tibial tuberosity, significantly increased during the course of running. It was concluded that, with developing fatigue, an imbalance in the contraction of the shank muscles develops in parallel to an increase in shank shock acceleration. The combination of these two changes may hamper the loading balance on the tibia since the bone becomes exposed to excessive bending stresses and to higher risk of stress injury.

Acceleration↗

PubMed1997

Predicted and measured muscle forces after recoveries of differing durations following fatigue in functional electrical stimulation.

Using 31P nuclear magnetic resonance (NMR) spectroscopy, the bioenergetics of paralyzed muscles activated by functional electrical stimulation (FES) were studied in vivo during fatigue and recovery on paraplegic subjects. During the activation phase of the muscle, the muscle force was also monitored. The phosphorus metabolites were found to vary systemically during the fatigue and to recover slowly to their rest state values after cessation of FES. During fatigue, a good correlation was found between the decaying force and each of the profiles of phosphocreatine, inorganic phosphorus, and intracellular pH. A musculotendon 5 element model was proposed for the activated muscle to predict its force generation capacity. A fatigue recovery function, based on the metabolic profiles, was introduced into the model. This model allowed us to predict the force expected to be developed as a function of the time after recovery of given time durations. Validation experimental measurements of force were carried out and included recurrent fatigue tests, both in the initially unfatigued state and at various times in the postfatigue stage of the muscle. Comparison of the predicted and measured forces indicated satisfactory agreement of the results. The developed model of muscle dynamics should help to design a strategy for reducing muscle fatigue under FES.

Electric Stimulation Therapy↗

PubMed1997

Is balance impaired by recurrent sprained ankle?

OBJECTIVE: To evaluate uninjured and recurrent sprained ankles during single leg standing, both with and without visual input, and the contribution of related proprioceptive feedback in this event. METHODS: A force measuring system was used for monitoring reaction forces in the anteroposterior and mediolateral directions during single leg standing. Differences between selected variables obtained in the uninjured and sprained ankles were analysed using two way analysis of variance. RESULTS: Foot-ground reaction forces in both anteroposterior and mediolateral directions were the same in normal and sprained ankles of each subject while standing with either open or closed eyes. However, standing with closed eyes, irrespective of the ankle status, always produced significantly higher reaction forces than those obtained with open eyes (P < 0.05). CONCLUSIONS: The amount of postural sway during single leg standing is similar in the chronically sprained and the uninjured ankle joint.

Adolescent↗

PubMed1997

Effect of ingested sodium bicarbonate on muscle force, fatigue, and recovery.

The influence of acute ingestion of NaHCO3 on fatigue and recovery of teh quadriceps femoris muscle after exercise was studied in six healthy male subjects. A bicycle ergometer was used for exercising under three loading conditions: test A, load corresponding to maximal oxygen consumption; test B, load in test A + 17%; test C, load in test B but performed 1 h after acute ingestion of NaHCO3. Functional electrical stimulation (FES) was applied to provoke isometric contraction of the quadriceps femoris. The resulting knee torque was monitored during fatigue (2-min chronic FES) and recovery (10-s FES every 10 min, for 40 min). Quadriceps torques were higher in the presence of NaHCO3 (P < 0.05): with NaHCO3 the peak, residual, and recovery (after 40 min) normalized torques were, respectively, 0.68 +/- 0.05 (SD), 0.58 +/- 0.05, and 0.73 +/- 0.05; without NaHCO3 the values were 0.45 +/- 0.04, 0.30 +/- 0.06, and 0.63 +/- 0.06. The increased torques obtained after acute ingestion of NaHCO3 indicate the possible existence of improved nonoxidative glycolysis in isometric contraction, resulting in reduced fatigue and enhanced recovery.

Administration, Oral↗

PubMed1997

Mobility of persons after traumatic lower limb amputation.

The objective of this study was to determine the influence of time span since amputation on mobility of persons experiencing traumatic lower limb amputation. A special questionnaire was sent to such persons and responses were analysed statistically. The subjects comprised 223 persons after traumatic lower limb amputation, residents of Slovenia. We discovered that 186 (74.2%) are using their prosthesis for more than 7 hours per day, 109 (52.2%) are able to walk outdoors without crutches, and 129 (57.8%) climb more than 20 stairs per day. In addition, those who are walking without crutches, walking longer distances, still cycling and driving a care are, on average, 5-10 years younger than the others. However, around one-third of persons who were young at the time of amputation face limitations of mobility later in life. A total of 76 (35.3%) are able to walk only up to 500 m out of doors, 38 (18.2%) can walk only with a pair of crutches, 62 (29.7%) need a cane or one crutch, and 37 (16.6%) cannot climb stairs. We conclude that successful fitting and usage of a prosthesis by persons after lower limb amputation promotes independent walking and mobility in everyday life. The level of independence achieved is related to time span since amputation.

Activities of Daily Living↗

PubMed1997

Double-limb support and step-length asymmetry in below-knee amputees.

The sequence of gait events and symmetry of kinematic parameters between both lower limbs are compromised in below-knee amputees. In the present study the periods of double-limb support and the step length in below-knee amputees were investigated. The symmetry of the two periods of double-limb support occurring in each stride was obviously abnormal (ratio: 0.74) among temporal and distance parameters. The time of double-limb support (0.211 +/- 0.05 seconds) measured from heel-strike of the amputated leg until toe-off of the normal leg was significantly longer (p = 0.011) when compared with the contralateral leg (0.173 +/- 0.04 seconds). The step length of the normal leg (0.709 +/- 0.07 m) was significantly (p = 0.045) shorter than that of the amputated leg (0.752 +/- 0.08 m). Most of these differences between measured kinematic parameters can be explained by the limited ability of the prosthesis ankle-foot component to reproduce the normal functions of both foot and ankle.

Adult↗

PubMed1996

Isokinetic and isometric strength of the thigh muscles in below-knee amputees.

OBJECTIVE: The strength of the quadriceps and hamstring muscles of the amputated limb in below-knee amputees was evaluated. DESIGN: A descriptive study based on clinical measurements of muscle strength. BACKGROUND: The residual limb of below-knee amputees is less active in daily functions. As a result, atrophy of the thigh muscles in the affected limb is a common finding. Quality of standing and gait performances depend on the strength of these muscles, which activate the knee of the amputated limb. METHODS: Isokinetic concentric and eccentric, as well as isometric, strength of thigh muscles was measured by means of a dynamometer. Parameters of peak torque and maximal average torque of the quadriceps and hamstring muscles were considered. RESULTS: Significant decreases (P < 0.01) in strength of the quadriceps and hamstrings were observed in the amputated limb. Thigh muscle strength in amputees over 7 years was not significantly weaker when compared with amputees where amputation had been performed more recently. CONCLUSIONS: In below-knee amputees, the thigh muscle strength of the amputated limb decreases significantly during the first years after amputation. RELEVANCE: In so far as the ultimate goal in rehabilitation of amputees is to return the patient to an acceptable level of function, it is recommended that the amputee should be trained and encouraged in self-strengthening exercises for the thigh muscles of the amputated limb.

Journal Article↗

PubMed1996

Stump length as related to atrophy and strength of the thigh muscles in trans-tibial amputees.

Stump length and the thigh muscles strength of the amputated limb are among the major factors influencing outcome of prosthetic rehabilitation of trans-tibial amputees. In the present study the authors evaluated and compared the strength of quadriceps and hamstrings muscles of both limbs in trans-tibial amputees, as measured by means of an electrical dynamometer. The obtained results showed that the thigh muscles of the sound limbs are significantly stronger than those of the amputated limbs (p < 0.01). The results obtained for amputees with shorter stumps were compared with those with longer stumps. In the group of amputees (n = 9) with a stump shorter than 15.1 cm, values of peak torque (in isokinetic contraction) and maximal average torque (in isometric contraction) were significantly (p < 0.5) weaker when compared to those (n = 9) with a stump longer than 15.1 cm. The results obtained for amputees with a higher rate of thigh muscle atrophy were compared to those with lesser atrophy. In the group of amputees where muscle atrophy was accompanied by decrease in thigh girth of over 5.9 cm, muscles strength did not significantly decrease (p < 0.5) as compared to amputees where thigh girth decrease was less than 5.9 cm. It is concluded that atrophy of the thigh muscles of trans-tibial amputees is accompanied with a significant decrease in strength. In amputees with a short stump, the short lever action provided by the stump interferes with the ability of the thigh muscles to control the prosthesis efficiently during daily activities such as standing and walking.

Activities of Daily Living↗