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ABSTRACT: Spinal manipulative therapy (SMT) has been recognized as an effective treatment modality for many back, neck and musculoskeletal problems. One of the major issues of the use of SMT is its safety, especially with regards to neck manipulation and the risk of stroke. The vast majority of these accidents involve the vertebro-basilar system, specifically the vertebral artery (VA) between C2/C1. However, the mechanics of this region of the VA during SMT are unexplored. Here, we present first ever data on the mechanics of this region during cervical SMT performed by clinicians. VA strains obtained during SMT are significantly smaller than those obtained during diagnostic and range of motion testing, and are much smaller than failure strains. We conclude from this work that cervical SMT performed by trained clinicians does not appear to place undue strain on VA, and thus does not seem to be a factor in vertebro-basilar injuries.
Journal of electromyography and kinesiology: official journal of the International Society of Electrophysiological Kinesiology 04/2012; 22(5):740-6. · 2.00 Impact Factor
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Clinical Psychology & Psychotherapy 01/2012; · 1.66 Impact Factor
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ABSTRACT: The elicitation of delayed-type hypersensitivity (DTH) reactions in mice is due to the sequential action of two different, antigen-specific, Thy-1+ cells. We have previously cloned the early-acting DTH-initiating cell from nude mice that were immunized and boosted by contact sensitization with oxazolone (OX). This cell clone, WP-3.27, releases an antigen-specific factor (OX-F) that sensitizes mast cells such that specific antigen challenge will induce serotonin release which mediates the early phase of DTH. In normal mice contact sensitized with picryl chloride (PCl), a similar polyclonal factor (PCl-F) has a similar activity and is also known to bind to macrophages. Thus, we measured macrophage production of TNFα, IL-1, IL-6, and PGE2 in response to the hapten affinity-purified DTH-initiating factors OX-F and PCl-F. Both factors induced significant release of each cytokine and PGE2. The production of TNFα, IL-1, and IL-6 was measured by bioassays. Northern blot analysis showed rapid accumulation of cytokine mRNA (2–4 hr), while maximal production of PGE2 occurred at approximately 8 hr. These macrophage activating properties of OX-F and PCl-F were not due to contamination with LPS as determined by the low levels of LPS present in OX-F and PCl-F and by the failure of polymyxin B to inhibit factor-induced PGE2 and TNFα production. Also, macrophage activation was shown not to be due to the action of several lymphokines known to be produced by WP3.27. Separation of OX-F and PCl-F by preparative isoelectric focusing showed a similar pattern: there were two major peaks of PGE2-inducing activity observed for both factors (for PCl-F at pI of 2–3 and 5.0, and for OX-F at pI of 3.5–4 and 5.0), but not for a sham factor produced by WEHI-3 cells. The ability of DTH-initiating factors to rapidly induce macrophage cytokine release and PGE2 synthesis 4–6 hr later may suggest a role for these mediators during the respective early vascular and late cellular phases of inflammation in DTH.
Cellular Immunology.
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ABSTRACT: We recently found that force enhancement following active stretch in skeletal muscles is accompanied by an increase in passive force following deactivation (J. Exp. Biol. 205 (2002) 1275). However, it is not known if this increase in passive force contributes to the force enhancement observed in the active muscle, and if it is observed at all muscle lengths. The purposes of this study were to quantify the amount of passive force increase as a function of muscle lengths, and to determine if this passive force contributes to the force enhancement observed in the active muscle. Experiments were performed on cat soleus (n=24) using techniques published previously (J. Biomech. 30(9) (1997) 865). Conceptually, tests involved comparisons of force enhancement and passive force increase for a variety of stretch tests in soleus. Furthermore, in one test, activation of the soleus was interrupted for 1 s in the force-enhanced state, and soleus was then re-activated. We found that total force enhancement and passive force increase were positively correlated for all test conditions, that passive force increase following stretch of the active soleus only occurred at muscle lengths corresponding to the descending limb of the force–length relationship, that increases in passive force for a given stretch magnitude became greater at long muscle lengths, and that upon reactivation, there was a remnant passive force enhancement. We conclude from these results that the passive force enhancement following stretch of an active muscle contributes to the total force enhancement, that this passive contribution increases with increasing muscle length, and that there must be at least one other factor than passive force increase that contributes to the total force enhancement, as the passive force increase was always smaller than the total force enhancement. A by-product of this investigation was that we observed a shift in the passive force–length relationship that was dependent on muscle activation, stretch magnitude and muscle length. Therefore, the passive force–length relationship is not a constant property of skeletal muscle, but depends critically on the muscle's contractile history.
Journal of Biomechanics.
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ABSTRACT: The functional significance of tendons, and the differences in tendon properties among synergistic muscles, is not well established for normal locomotion. Previous studies have suggested that tendons may store mechanical energy during the early phase of support, and then release this energy during the late phase of support. The storage and release of mechanical energy by tendons may modify the velocity of shortening and elongation and the power produced by the muscle belly and the fibers, and may influence the metabolic cost of locomotion. The aims of this study were (1) to estimate the amount of negative and positive work done by the tendon and the muscle belly of the cat soleus (SO), gastrocnemius (GA), and plantaris (PL), and (2) to determine the relative contribution of the elastic energy stored in the tendons to the total mechanical work done by these three muscles during walking and trotting. Forces of SO, GA, and PL muscles were measured using standard force transducers in three cats walking and trotting at speeds of 0.4–1.8 m s−1 on a motor-driven treadmill. Video records and a geometrical model of the cat hindlimb were used for calculating the length of the muscle-tendon complexes of SO, GA, and PL during locomotion. Instantaneous lengths of the tendons of SO, GA, and PL during a step cycle were estimated from the stress-strain properties, the effective lengths, the cross-sectional areas, and the instantaneous forces of the tendons. Stress-strain properties for the tendons were obtained experimentally from one animal. The length of the belly was defined as the difference between the muscle-tendon complex length and the tendon length. Mechanical power of the tendon and the muscle belly was calculated as the product of the measured muscle force and the calculated rates of change in tendon and muscle belly lengths, respectively. Mechanical power and work of the tendons and bellies of SO, GA, and PL were calculated for 144 step cycles. During a step cycle, peak negative and peak positive velocities as well as peak powers of the muscle-tendon complexes of SO, GA, and PL were typically higher than those of the muscle bellies. Positive work done by the muscle-tendon complexes exceeded the positive work done by the muscle bellies. GA and PL tendons stored more mechanical energy than the SO tendon. The contributions of the elastic energy stored in the tendons to the positive work done by the muscle-tendon complexes decreased with increasing speeds of locomotion for two of the three cats studied and did not change for the third one. These contributions equaled 50-21%, 30-14%, and 25-18% for the three cats, respectively. The results of this study suggest that energy absorption and release by the tendons of cat SO, GA, and PL make up a substantial part of the total energy absorbed and generated by the corresponding muscle-tendon complexes.
Journal of Biomechanics.
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ABSTRACT: During normal, voluntary movements, skeletal muscles typically contract in a highly dynamic manner; the length of the muscle and the speed of contraction change continuously. In this study, we present an approach to predict the accurate behavior of muscles for such dynamic contractions using Huxley's cross-bridge model. A numerical procedure is proposed to solve, without any assumptions, the partial differential equation that governs the attachment distribution function in Huxley's cross-bridge model. The predicted attachment distribution functions, and the corresponding force responses for shortening and stretching, were compared with those obtained using Zahalak's analytical solution and those obtained using the so-called “distribution moment model” in transient and steady-state contractions. Compared to the distribution moment model, the solutions obtained using our model are exact rather than approximate. The solutions obtained using the analytical approach and the present approach were virtually identical; however, in terms of CPU times, the present approach was 250–300 times faster than Zahalak's. From the results of this study, we concluded that the proposed solution is an exact and efficient way for solving the partial differential equation governing the cross-bridge model.
Mathematical Biosciences.
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ABSTRACT: The purpose of this study was to quantify end-feel by evaluating instantaneous stiffness and change in stiffness of the tibiofemoral joint. Normal (n = 26), anterior cruciate ligament (ACL) deficient (n = 6), and posterior cruciate ligament (PCL) deficient (n = 2) subjects were tested using the KT 2000 knee ligament arthrometer. Analogue force and displacement data were digitized, filtered, and calibrated. Force-displacement curves in the region of anterior tibial displacement were approximated using 5th degree polynomial functions. Stiffness and change in stiffness were determined analytically by the first and second derivatives of these functions. Subjects with confirmed ACL deficiency had lower values for stiffness and change in stiffness in the region of the curves believed to be indicative of ACL function, compared to contralateral knees and control subjects.
Clinical Biomechanics.
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ABSTRACT: Objectives. This study was aimed at investigating muscle strength and quadriceps inhibition in patients with unilateral anterior knee pain syndrome.Design. Functional assessments were made before an arthroscopic knee surgery and 6 weeks and 6 months following the surgical intervention.Background. Traumatic knee injuries have been associated with severe muscle inhibition of the knee extensor muscles. Muscle inhibition is a serious hindrance in the rehabilitation process and prevents full functional recovery of the affected joint.Methods. 30 patients participated in the study. Isometric quadriceps strength was measured using a KinCom dynamometer. Muscle inhibition was assessed using the interpolated twitch technique which requires applying a single electrical twitch to the femoral nerve during a maximal isometric knee extensor contraction. Pain was assessed with a 100 mm visual analogue pain scale.Results. Pre-surgery, substantial muscle inhibition and pain was observed in the affected leg compared with the contralateral leg. Over the 6 month period there was a decrease in pain and muscle inhibition, although the decrease in muscle inhibition failed to reach statistical significance. Muscle strength showed a decrease 6 weeks post-surgery followed by an increase 6 months following surgery compared with pre-surgical values.Conclusions. The arthroscopic intervention was successful in reducing pain in patients with unilateral anterior knee pain syndrome. However, muscle inhibition was still substantial 6 months following surgery and was significantly higher in the affected and contralateral limb than in normal subjects.
Clinical Biomechanics.
