Solomonow

No abstract text is available yet for this article.

PURPOSE: Repetitive Lumbar Injury (RLI) is common in individuals engaged in long term performance of repetitive occupational/sports activities with the spine. The triggering source of the disorder, tissues involved in the failure and biomechanical, neuromuscular, and biological processes active in the initiation and development of the disorder, are not known. The purpose is, therefore, to test, using in-vivo feline model and healthy human subjects, the hypothesis that RLI due to prolonged exposure to repetitive lumbar flexion-extension is triggered by an acute inflammation in the viscoelastic tissues and is characterized by lingering residual creep, pronounced changes in neuromuscular control and transient changes in lumbar stability...

Cumulative lumbar disorder is common in individuals engaged in long term performance of repetitive and static occupational/sports activities with the spine. The triggering source and of the disorder, the tissues involved in the failure and the biomechanical, neuromuscular, and biological processes active in the initiation and development of the disorder are not known. The hypothesis is forwarded that static and repetitive (cyclic) lumbar flexion-extension and the associated repeated stretch of the various viscoelastic tissues (ligaments, fascia, facet capsule, discs, etc...

Spine stability of the behaving human in health or disorder is a complex, multi-factorial and time variable index. The major components of stability are the properties of the external load, passive viscoelastic tissues (ligaments, discs, facet capsules and dorso-lumbar fascia) combined with the properties of the active tissues (muscles and their sensory-motor control, co-activation and associated intra-abdominal pressure) as well as the pro-inflammatory status of the tissues. Each of the many components' contribution is time variable with dependence on the dose-duration of the work stimulus and the associated rest...

BACKGROUND CONTEXT: Cumulative (repetitive) lumbar disorder is common in the workforce, and the associated epidemiology points out high risk for lifting heavy loads, performing many repetitions, and performing movements at high velocity. Experimental verification of viscoelastic tissue degradation and a neuromuscular disorder exist for cyclic work under heavy loads. Experimental validation for a disorder because of cyclic loads under high-velocity movement is missing. PURPOSE: Obtain experimental verification that high-velocity lumbar flexion-extension results in significant increase of proinflammatory cytokines in the viscoelastic tissues...

Surface and wire myoelectric activity of the medial gastrocnemius (MG), lateral gastrocnemius (LG) and tibialis anterior (TA) of the cat were recorded during supramaximal stimulation applied via their nerves before and after the muscle nerve to the LG and TA were cut in order to determine the amount of EMG crosstalk amongst neighbouring muscles. It was shown that the peak-to-peak (p-p) amplitude and mean absolute value (MAV) of crosstalk M waves recorded from the LG and TA after their nerve was cut did not exceed 5% of their maximal value for surface electrodes and 2...

No abstract text is available yet for this article.

No abstract text is available yet for this article.

A computerized radiographic technique was used to determine the effect of hamstring antagonist co-contraction on the stability of the joint during isometric knee extension. Data collected from 12 cadaver knees showed that significant anterior displacement and internal rotation of the tibia occurred during isolated quadriceps loading, whereas significant reduction in anterior displacement and rotation occurred upon simultaneous low-level loading of the hamstrings in the range of motion of 15°-80° flexion. Hamstrings co-contraction was ineffective in the range of 0°-15° of flexion...

No abstract text is available yet for this article.

No abstract text is available yet for this article.

The purpose of this study was to determine if differences exist between the control strategies of the elbow flexor and extensor muscles performing stepwise and linearly increasing isometric contractions, and to determine their control strategy when active as antagonists to each other. The electromyogram (EMG) from the biceps brachii and triceps brachii were recorded during stepwise and linearly increasing contractions in flexion and extension. The power density spectrum of the EMG was determined and the median frequency (MF) for each spectrum was calculated for assessment of changes in the average conduction velocity, which reflects motor unit recruitment and derecruitment, and thereby the control strategy of the muscle...

The separate contributions of the recruitment level and of the firing rate of the motor units on the soundmyogram and electromyogram time domain parameters were investigated during stimulation of the motor nerve of the cat gastrocnemius muscle. Upon orderly increase in the number of active motor units at a fixed firing rate, both the peak to peak amplitude (P-P(max)) and the root mean square (RMS) of the sound myogram increased. At full recruitment the increase in firing rate from 2.5 to 50 Hz induced an exponential decline in the P-P(max)...

The effects of indirect stimulation at 500-1,000 Hz on force production by the cat's slow-fibered soleus and mixed-fiber medial gastrocnemius (MG) muscles were compared for their relevance to the use of such "high-frequency" stimulation to modulate spasticity or the induced contraction of a centrally paralyzed muscle. Severe loss in force was seen in both muscles, and slow (S) motor units (MUs) within the MG showed about the same susceptibility as fast (FF) units. Both muscles and isolated fast and slow MUs within the MG exhibited an initial spike of tension and throughout stimulation a low level of residual tension...

The electromyogram (EMG)-force relations of a single skeletal muscle (soleus) acting on a joint set isometrically at various flexion angles was studied using electrical nerve stimulation as the experimental method. The EMG-force relationships were linear at extremes of joint extension and became progressively nonlinear as the flexion angle increased. Joint angles at extreme extension showed the least passive and active force whereas their corresponding EMG versus force relations were linear. At extremes of joint flexion large passive force was accompanied by minimal active force...

Repetitive or overuse disorders of the lumbar spine affect the lives of workers and athletes. We hypothesize that repetitive anterior lumbar flexion-extension under low or high load will result in significantly elevated pro-inflammatory cytokines expression several hours post-activity. High loads will exhibit significantly higher expression than low loads. Lumbar spine of in vivo feline was subjected to cyclic loading at 0.25 Hz for six 10-min periods with 10 min of rest in between. One group was subjected to a low peak load of 20 N, whereas the second group to a high peak load of 60 N...

BACKGROUND: Cumulative trauma disorder is commonly reported by workers engaged in prolonged repetitive/cyclic occupational activities. Recent experimental evidence confirms that relatively short periods of cyclic lumbar flexion at high loads result in substantial creep of viscoelastic tissues, prolonged periods of its recovery to baseline together with a neuromuscular disorder and exposure to instability. The biochemical process associated with the creep and neuromuscular disorder are not well explored...

The motor control system may compensate for lumbar instability following cyclic work with differential response to load magnitude. In vivo felines were exposed to a cumulative 1 h of cyclic work at 0.25 Hz. One group exposed to light whereas the second to heavy load while recording lumbar displacement and multifidus EMG during work and in single test cycles over 7 h rest post-work. Significant laxity and reduced reflexive EMG activity were evident immediately post-work in both groups. EMG and laxity recovered over 7 h rest in the group exposed to light load whereas in the group exposed to heavy load, motor control compensation was triggered within 1-2 h post-work...

The mechanical and neurological properties of ligaments are reviewed and updated with recent development from the perspective which evaluates their role as a source of neuromusculoskeletal disorders resulting from exposure to sports and occupational activities. Creep, tension-relaxation, hysteresis, sensitivity to strain rate and strain/load frequency were shown to result not only in mechanical functional degradation but also in the development of sensory-motor disorders with short- and long-term implication on function and disability...

Neuromuscular control of lumbar stability following exposure to prolonged static work, under low and high loads, was assessed in the in vivo feline model. Six sessions of 10 min work at 20N with 10 min between rest was compared to a group subjected to the same protocol but carrying high loads of 60N. Displacement and tension developed in the spine at the instant the multifidus muscles applied stabilizing contractions, and their amplitudes were obtained from their electromyogram (EMG). Significant (P < 0...