Eli Isakov

Effect of fatigue on leg kinematics and impact acceleration in long distance running

The eAect of fatigue on impact acceleration on the shank, stride rate, knee angle and hip vertical excursion was studied in 14 subjects in 30 minutes treadmill running above their anaerobic threshold (AT) speeds. Respiratory data were collected to determine the AT speed and to indicate the progressively developing fatigue. The following changesOP < 0:05U were obtained from the 1st to the 30th minute of running: average stride rate decreased from 1:46 0:05 to 1:39 0:03 seconds ˇ1 ; average angle at maximal knee extension position increased from 13:8 3:1∞ to 17:2 4:2∞; average knee flexion resulting from foot strike decreased from 13:6 6:3∞ to 8:1 3:0∞; average hip vertical excursion between highest position to peak acceleration position increased from 5:1 1: 5t o 6:2 1:2 cm. The average impact acceleration on the shank, measured by means of an accelerometer attached to the tibial tuberosity, increased from 6:9 2: 9t o 11:1 4:2 g. It was concluded that the obtained kinematic changes due to fatigue were consistent with the substantially higher impact accelerations, increasing the risk of overload injuries in the shank. ” 2000 Elsevier Science B.V. All rights reserved. PsycINFO classification: 2330; 2540; 4010

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, cocontracting 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 amputees gait.

Dynamic loading on the human musculoskeletal system —effect of fatigue

OBJECTIVE: A study was conducted to investigate the effects of fatigue on the ability of human musculoskeletal system to deal with the onslaught of the heel strike initiated shock waves. DESIGN: Running on a treadmill at the anaerobic threshold level for 30 min was used to acquire the experimental data on the foot strike initiated shock waves. BACKGROUND: Muscles act to lower the bending stress on bone and to attenuate the dynamic load on human musculoskeletal system. Fatigue may diminish their ability to dissipate and attenuate loading on the system. Knowledge of the effects of fatigue on the ability of the human musculoskeletal system to attenuate the shock waves may help in design of the training procedures and exercises. METHODS: Twenty-two young healthy males participated in this study. Each one was running on the treadmill at the speed corresponding to his anaerobic threshold for 30 min. The heel strike induced shock waves were recorded every 5 min on the tibial tuberosity and sacrum. The data obtained were analyzed in both temporal and frequency domains. RESULTS: The results reveal significant increase in the dynamic loading experienced by the human musculoskeletal system with fatigue. This may be attributed to the inability of the fatigued system to provide an efficient way to attenuate shock waves. CONCLUSIONS: The analysis of the recorded signals suggests that fatigue contributes to the reduction of the human musculoskeletal systems capacity to attenuate and dissipate those shock waves. This capacity appears to be a function not only of the fatigue level, but also of the vertical location along the skeleton. RELEVANCE: Fatigue during running may affect the ability of the human musculoskeletal system to attenuate and dissipate the heel strike induced shock waves. The study of the fatigue effect on shock wave attenuation provides information that may benefit the runner.

Shock Transmission and Fatigue in Human Running

The goal of this research was to analyze the effects of fatigue on the shock waves generated by foot strike. Twenty-two subjects were instrumented with an externally attached, lightweight accelerometer placed over the tibial tuberosity. The subjects ran on a treadmill for 30 min at a speed near their anaerobic threshold. Fatigue was established when the end-tidal CO2 pressure decreased. The results indicated that approximately half of the subjects reached the fatigue state toward the end of the test. Whenever fatigue occurred, the peak acceleration was found to increase. It was thus concluded that there is a clear association between fatigue and increased heel strike-induced shock waves. These results have a significant implication for the etiology of running injuries, since shock wave attenuation has been previously reported to play an important role in preventing such injuries.

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.

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.

Influence of speed on gait parameters and on symmetry in transtibial amputees

Normal gait is characterised by a high level of inter-leg symmetry of gait parameters. Therefore, efforts in rehabilitation of amputees are directed at the construction of a prosthesis which provides normal leg function and allows a more symmetrical gait. Analysis of the gait of trans-tibial amputees was performed when they were ambulating at their own freely selected speed and at a faster speed. The effect of speed on selected gait parameters in each leg was evaluated and the influence on symmetry established by comparing the inter-leg changes for each of the selected parameters. The faster gait trail affected significantly all temporal and distance parameters in both legs but not the level of symmetry between legs. At the faster speed, the hip angles at heel-strike and during swing and the knee angle during load response, in the normal leg, and the knee angle during swing in the amputated leg, all increased significantly. Speed of gait significantly affected symmetry between knee angles as reflected by the increased differences measured during load response (from 2.62 ±5.2 to 7.06 ±4.2 degrees) and during toe-off (from 1.80 ±7.4 to 9.50 ±9.1 degrees). Timing and sequence of selected gait events, as related to stride time, were not significantly affected by speed of gait. These results might contribute to a better understanding of gait characteristics in trans-tibial amputees and provide design guidance for prosthetic components.

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.

Muscle fatigue in interrupted stimulation: Effect of partial recovery on force and EMG dynamics.

Muscle fatigue is a major problem in functional electrical stimulation (FES); the understanding of fatigue and recovery processes is thus of great interest. In interrupted stimulation, fatigue and recovery occur in sequence, and the history-dependency of the muscles response to FES becomes significant. In this work, the force and electromyographical (EMG) fatigue characteristics of FES-activated paralysed muscles were studied, both in the initially unfatigued state (primary fatigue) and in the reactivated state, after rest periods of prescribed durations (post-recovery fatigue). Because the data were collected over weeks, longitudinal studies were also made to account for long-term training effects of the muscle. Mechanical and myoelectric profiles, the latter derived from the M-wave, were obtained from the right quadriceps of two paraplegic subjects under isometric stimulation. Force was found to correlate highly with peak-to-peak amplitude of the EMG M-wave. Training did not affect this correlation, but as the recovery duration increased, the force-EMG curves became less concave. Training was found to increase the muscle force and EMG peak-to-peak amplitude, as well as the residual force achieved, but it had no noticeable effects on the M-wave duration parameters. Both the force and EMG parameters demonstrated substantial recovery within the first 3 min of rest, and exhibited a consistent tendency to level off for higher periods of rest. After comparing this finding to those expected from previous metabolic models, it was concluded from the subjects studied and model developed that, in addition to metabolic factors, electrolytic factors may be significant in governing the dynamics of fatigue and recovery.

Anatomic sites of foot lesions resulting in amputation among diabetics and non-diabetics

OBJECTIVE To identify and quantify the anatomic sites of foot lesions resulting in amputation among patients suffering from peripheral arterial disease with and without diabetes mellitus. DESIGN A retrospective study. SETTING Department of Orthopaedic Rehabilitation. PATIENTS A total of 212 recent lower limb amputees with diabetes mellitus (158) or peripheral arterial disease only (54) admitted for prosthetic rehabilitation. RESULTS In 62.2% of all amputees the site of lesion that led to amputation was located in the digits. A lesion under the metatarsal heads was reported in 8.0%, along the mid-foot and heel in 8.5%, on the dorsum of the foot in 3.3%, around the ankle joint and lower leg in 5.7%. Finally, 12.3% reported multiple lesions or were unable to recall the exact anatomic location. CONCLUSIONS Most foot lesions resulting in amputation are located around the digits. These high-risk sites, therefore, need the patients and the health care teams special attention. The patient should be trained in self foot examination and meticulous daily care, whereas the role of the health care team is in foot evaluation and provision of protective foot wear.