Length-tension Relationship Of Muscle Research Articles

Offset Considerations in Total Hip Arthroplasty.

To perform total hip arthroplasty (THA) successfully, a surgeon must be able to place the implants in a position that will restore and duplicate the patient's baseline anatomy and soft-tissue tension. One of the critical factors is the restoration of femoral offset. It is the goal of this review to precisely define measurement of offset in THA, describe its role in hip joint biomechanics, outline alterations that can be performed intraoperatively, and explain how it can create potential pathologic states. If there is a lack of offset restoration, it can result in a host of complications, including bony impingement with pain, edge loading or prosthetic joint instability, and alterations in the muscle length-tension relationship leading to reduced motor performance. Excessive femoral offset can increase hip abductor muscle and iliotibial band tension resulting in greater trochanteric pain regardless of the surgical approach. The purpose of this review was to analyze intraoperative surgical factors, choice of prosthetic implant type and position that are required to maximize stability, and dynamic motor performance after THA.

Achilles Tendon Ruptures: Anatomy and Physiology

Together, the muscle bellies of the medial and lateral gastrocnemius along with the soleus conjoin to make the Achilles tendon. The Achilles tendon is the most commonly ruptured tendon. It is important to take into account the length-tension relationship of muscle and anatomic positioning of the Achilles when treating Achilles tendon ruptures.Level of Evidence:Level V, expert opinion.

Recording of length-tension relationship of elbow flexors and extensors by varying elbow angle in human

Objectives: The concept of length-tension relationship in skeletal muscle can be studied in a living person by demonstrating the relationship between isometric strength and joint angles. There is lack of an effective practical module to demonstrate this concept in living person, hence the study was planned. Materials and Methods: A simple, feasible and novel practical is designed using a custom-made isometric elbow flexion-extension exercising instrument, in which isometric elbow strength is measured using a dynamometer against various elbow joint angles measured using a goniometer. Result: Elbow isometric strength varied across its joint angles and was maximum at the optimum angle, which was 90°. Conclusion: We propose a simple and novel practical to understand the skeletal muscle length-tension relationship in a living person partly, by using the angle-strength relationship for undergraduate teaching in physiology.

Immediate effect of Chest Proprioceptive Neuromuscular Facilitation on Respiratory Rate, Chest Expansion and Peak Expiratory Flow Rate in patients with Chronic Obstructive Pulmonary Disease

Background: In Chronic Obstructive Pulmonary Disease (COPD), as result of dynamic hyperinflation, primary respiratory muscles go into weakness and length tension relationship of muscles is altered. This leads to decreased ability of primary respiratory muscles to generate muscle tension. COPD patients mostly use accessory muscle for breathing and there is lack of facilitation of intercostal muscle and weakness of diaphragm. Few studies are conducted to assess the immediate effect of Chest Proprioceptive Neuromuscular Facilitation (PNF) i.e. intercostal stretch among COPD patients. Therefore, there is need to find out immediate effect of chest PNF- intercostal stretch on respiratory rate (RR), chest expansion, peak expiratory flow rate (PEFR) among patient with COPD. Objective: To find out immediate effect chest PNF on respiratory rate, chest expansion and peak expiratory flow rate. Methodology: Ethical clearance and participant consent was taken. Study design was Qausi experimental study. The 65 subjects were taken by convenient sampling. Intercostal stretch was applied over 2nd and 3rd rib bilaterally for 10 breaths with 1 minute rest with a 10 repetitions and Outcome measures were assessed before and immediately after giving chest PNF. SPSS 16 software was used to analyse the data. The normality of the data was assessed using parametric paired t test. Significance level was set at 0.05 and 95% Confidence Interval. Outcome Measures: Respiratory rate, Chest expansion, Peak expiratory flow rate. Result: Immediate effect of chest PNF showed that there was statistically significant increase in PEFR and chest expansion at three level (P=0.000) and there was statistically significant decrease in RR (P=0.000). Conclusion: There is immediate effect of Chest PNF- intercostal stretch on, Respiratory rate, Chest expansion at three level that is axillary, nipple and xiphisternal and Peak expiratory flow rate. It is an easy to use, less time consuming, easy to understand and cost effective technique. KEY WORDS: Chest PNF, intercostal stretch, COPD.

ISOKINETIC TRUNK STRENGTH, VALIDITY, RELIABILITY, NORMATIVE DATA AND RELATION TO PHYSICAL PERFORMANCE AND LOW BACK PAIN: A REVIEW OF THE LITERATURE

Isokinetic testing of the trunk is ubiquitous in the literature and with training, however, there is a lack of normative data for adolescents and adult athletes. The purpose of the current review is to present and summarize data about isokinetic trunk strength assessment relative to young, adolescent and adult athletes. Testing position variations, reliability values by age groups, utilization of strength measures and normative data by age groups have been discussed. The information presented within this review are of practical importance for assessment of isokinetic trunk strength to appraise the athlete's current strength level and provide suitable conditioning training program. Literature review. NCBI-PubMed, Web of Science, and SPORTDiscus were searched to identify relevant correlation and intervention studies/trials related to isokinetic testing of the trunk. Forty-two studies meeting the inclusion criteria were included in this literature review. The validity of isokinetic trunk measures (i.e. peak torque; flexion/extension ratios) can be affected by a number of factors including whether the individual is tested in seated or standing position, which can alter the muscle length-tension relationship. Reliability is excellent for some strength measures and moderate to high for muscle endurance. Extension and concentric measures tend to have better reliability than flexion and eccentric measures respectively, while females show typically higher reliability scores than men due to the difficulty in controlling men's body position when testing. Normative data for various populations are provided. Muscle assessment methods using an isokinetic dynamometer are considered reliable with high correlations to peak strength values and flexor/extensor ratios over age groups. However, caution should be exercised when interpreting position-specific isokinetic test results that measure trunk flexion (standing vs seated position). Still, there are indications that low-velocity movements are more reliable for measuring trunk strength. In adolescence, boys appear stronger than girls, with higher values for trunk extensors. Trunk flexors and extensors ratios decrease with growth. Data of isokinetic trunk muscle performance seems to be correlated not only to anthropometric parameters but also to sports discipline and training volume. The effects of sport on the muscular strength of the trunk may have both a preventive factor and a possible risk factor for low back pain. There is evidence for an association between high physical workloads and back injury. 5.

Reconstruction of Chronic Distal Biceps Tendon Rupture With Autogenous Semitendinosis Graft Using the “Anatomic Length Method” and Concomitant Bicipital Aponeurosis Repair

We present a novel variation of a surgical technique for reconstruction of chronic distal biceps tendon ruptures using the “Anatomic Length Method.” Graft length for chronic distal biceps tendon rupture reconstruction is extremely variable and typically empirically determined by elbow position during final fixation. These techniques do not account for chronicity and varying degrees of retraction and muscle shortening. For this unique variation in the surgical technique, the graft length used is based on previous anatomic cadaveric measurements done in our center with an external distal biceps tendon length mean of 6.3 cm. In addition, our technique routinely reconstructs the bicipital aponeurosis. This allows for a highly reproducible surgical technique and restores a more normal biceps anatomy and muscle length-tension relationship.

Dry needling equilibration theory: A mechanistic explanation for enhancing sensorimotor function in individuals with chronic ankle instability

ABSTRACT Patients with chronic ankle instability (CAI) experience a dynamic interplay between impaired mechanical structures and sensorimotor deficiencies that contribute to recurrent sprains and sensations of instability. Concomitantly, muscular trigger points (MTrPs) are known to occur following trauma, maximal or submaximal concentric contractions, and unaccustomed eccentric loads. Additionally, MTrPs are theorized to be exacerbated in low-load and repetitive strain activities. MTrPs located within a muscle are associated with altered motor control, reaction delay, and decreased strength, deficits also found among those with CAI. Dry needling (DN) is reported to improve muscle range of motion, motor control, and pain in a myriad of neuromusculoskeletal conditions by decreasing spontaneous electrical activity and stiffness of taut muscle bands while improving filament overlap. Building on evidence supporting neuromechanical decoupling in chronic ligamentous injury with what is known about the development of MTrPs, this paper proposes a centrally mediated mechanism for improved sensorimotor function following DN for individuals with CAI. Dry needling equilibration theory (DNET) states that proprioception is improved following DN in the lower extremity by changing the muscle’s length–tension relationship and leveraging minor acute discomfort to improve muscle spindle afferent information via the gamma motor system. The application of DNET for individuals with CAI may provide a mechanistic explanation for improved descending cortical output, resulting in enhanced sensorimotor function.

Release of fascial compartment boundaries reduces muscle force output.

Most limb muscles operate within a compartment defined by fascial layers that enclose a muscle or groups of muscles within a defined space. These compartments are important clinically, because fluid accumulation can cause ischemia and tissue necrosis if untreated. Little is known, however, about how fascial enclosures influence healthy muscle function. One previous study showed that removing a fascial covering reduced the force output of a muscle under maximal stimulation. We hypothesized that such reduction in force output was due to a change in the muscle length following fasciotomy and that a reduced force output could be explained by the length-tension relationship of muscle. Thus we predicted that the maximum force across a range of lengths would be unchanged following fasciotomy. We measured maximal tetanic force output in a wing muscle in wild turkeys both before and after removal of fascia that enclosed the muscle in a compartment. Our hypothesis was not supported. The length-tension curve of this muscle showed that removal of fascia reduced maximum force output to 72 ± 10% of the prefascial release condition. Thus a reduction in muscle force following fasciotomy was not explained by a change in muscle length. The mechanism underlying reduction in force is unclear, but it suggests that the assumption underlying most isolated muscle experiments, i.e., removal of a muscle from its situation in vivo does not influence its maximal mechanical output, may need reexamining. NEW & NOTEWORTHY Most limb muscles are enclosed within compartments bound by robust fascial sheets. The mechanical significance of the close packing of muscle and fascia is largely unexplored. We used an animal model to show that removal of a fascial covering reduces the maximal force developed during contraction. These results raise questions about the use of isolated muscles to estimate muscle performance and suggest that a muscle's mechanical surrounding influences performance by mechanisms that are not understood.

Joint angle-torque characteristics of the knee extensors following eccentric exercise-induced muscle damage in young, active women

Functional disruption following eccentric exercise-induced muscle damage is characterized by an immediate and prolonged loss in force-generating capacity, a disproportionate loss of strength at short muscle lengths, and a rightward shift in muscle length-tension relationship, in favor of a longer muscle length for optimal force generation. The purpose of this study was to examine progressive changes in muscle joint angle-torque characteristics following strenuous eccentric exercise in the quadriceps group, in female athletes. Seventeen physically active female athletes completed eccentric exercise designed to induce muscle damage. Isokinetic dynamometry was used to determine characteristics of muscle strength loss for the following dependant variables: change in maximal force, force at optimal and short muscle lengths, and shift in length-tension relationship at 1 hour, 24 hours, 48 hours, 72 hours, and 96 hours following damaging exercise. Perceived soreness and creatine kinase activity were also measured at these times. Significant increases in perceived soreness and creatine kinase activity, and a significant reduction in force-generating capacity were observed. A greater strength loss at short muscle lengths was observed following damaging exercise [17.2% vs. 25.7% relative force reduction for optimal and short (71° and 21° from full extension) muscle lengths, respectively]. A significant rightward shift in optimal joint angle for force generation was also observed, indicating that maximal force was generated at a longer muscle length subsequent to damaging exercise. This paper demonstrates a progressive rightward shift in the muscle length tension relationship.

December 2011 Letters to the Editor-in-Chief

Letters to the Editor-in-Chief of JOSPT as follows: ‘Early Prognostic Factors in Patients With Whiplash’ and Author's Response ‘Staying Current in the Use of Ultrasound Imaging’ and Author's Response ‘Differentiating the Soleus From the Gastrocnemius With the Heel Raise Test’ and Author's Response J Orthop Sports Phys Ther 2011;41(12):983–987. doi:10.2519/jospt.2011.0202

Whole muscle length-tension relationships are accurately modeled as scaled sarcomeres in rabbit hindlimb muscles

An a priori model of the whole active muscle length-tension relationship was constructed utilizing only myofilament length and serial sarcomere number for rabbit tibialis anterior (TA), extensor digitorum longus (EDL), and extensor digitorum II (EDII) muscles. Passive tension was modeled with a two-element Hill-type model. Experimental length-tension relations were then measured for each of these muscles and compared to predictions. The model was able to accurately capture the active-tension characteristics of experimentally-measured data for all muscles (ICC=0.88±0.03). Despite their varied architecture, no differences in predicted versus experimental correlations were observed among muscles. In addition, the model demonstrated that excursion, quantified by full-width-at-half-maximum (FWHM) of the active length-tension relationship, scaled linearly (slope=0.68) with normalized muscle fiber length. Experimental and theoretical FWHM values agreed well with an intraclass correlation coefficient of 0.99 ( p<0.001). In contrast to active tension, the passive tension model deviated from experimentally-measured values and thus, was not an accurate predictor of passive tension (ICC=0.70±0.07). These data demonstrate that modeling muscle as a scaled sarcomere provides accurate active functional but not passive functional predictions for rabbit TA, EDL, and EDII muscles and call into question the need for more complex modeling assumptions often proposed.

Die subtrochantäre End-zu-Seit-Valgisation zur Therapie der schweren kindlichen Coxa vara

Healing of the frequently associated femoral neck pseudarthrosis. Restoration of a proper length-tension relationship of muscles and lever arms of the hip. Regulation of forces acting on the femoral neck. Realignment of the leg length. Adjustment of the greater trochanter apophysis to allow regular growth. Severe infantile coxa vara (CCD [collodiaphyseal] angle<or=100 degrees) with or without femoral neck pseudarthrosis. All coxae varae based on local or systemic bone diseases, especially coxa vara in osteogenesis imperfecta, rickets, osteomalacia and meningomyelocele. Secondary coxa vara combined with dysplastic acetabulum. Preoperative planning. Standard lateral approach to the proximal femur. Insertion of a guide wire according to the preoperative planning followed by a cannulated chisel. After removal of both the chisel and the guide wire, insertion of the plate chosen in the preoperative planning. Subtrochanteric osteotomy (one femoral shaft width distal to the plate) in an anterior-posterior direction. Reposition of the bone fragments (end-to-side) and securing of the plate to the femoral shaft using standard cortical screws. Closure of the wound. 6-week spica casting till the age of 7 years or further on depending on compliance. 13 children with 20 affected hips (13 developmental coxae varae/spondyloepi-metaphyseal dysplasias, five postosteomyelitic coxae varae, two coxae varae following avascular necrosis) underwent the above procedure at an average age of 7.1 years. Responder rate at follow-up (mean age of 13.4 years) was 100%. All femoral neck pseudarthroses healed. One hip developed a recurrent coxa vara requiring reoperation.

Cardiac Tissue Engineering in an In Vivo Vascularized Chamber

Cardiac tissue engineering offers the prospect of a novel treatment for acquired or congenital heart defects. We have created vascularized pieces of beating cardiac muscle in the rat that are as thick as the adult rat right ventricle wall. Neonatal rat cardiomyocytes in Matrigel were implanted with an arteriovenous blood vessel loop into a 0.5-mL patented tissue-engineering chamber, located subcutaneously in the groin. Chambers were harvested 1, 4, and 10 weeks after insertion. At 4 and 10 weeks, all constructs that grew in the chambers contracted spontaneously. Immunostaining for alpha-sarcomeric actin, troponin, and desmin showed that differentiated cardiomyocytes present in tissue at all time points formed a network of interconnected cells within a collagenous extracellular matrix. Constructs at 4 and 10 weeks were extensively vascularized. The maximum thickness of cardiac tissue generated was 1983 microm. Cardiomyocytes increased in size from 1 to 10 weeks and were positive for the proliferation markers Ki67 and PCNA. Connexin-43 stain indicated that gap junctions were present between cardiomyocytes at 4 and 10 weeks. Echocardiograms performed between 4 and 10 weeks showed that the tissue construct contracted spontaneously in vivo. In vitro organ bath experiments showed a typical cardiac muscle length-tension relationship, the ability to be paced from electrical field pulses up to 3 Hz, positive chronotropy to norepinephrine, and positive inotropy in response to calcium. In summary, the use of a vascularized tissue-engineering chamber allowed generation of a spontaneously beating 3-dimensional mass of cardiac tissue from neonatal rat cardiomyocytes. Further development of this vascularized model will increase the potential of cardiac tissue engineering to provide suitable replacement tissues for acquired and congenital defects.

Effects of Multi-Joint Angle Changes on EMG Activity and Force of Lower Extremity Muscles during Maximum Isometric Leg Press Exercises

The objectives of this study were to identify the position where optimal leg muscle force occurs and to analyze the lower extremity muscle activity by comparing different hip and knee joint angle positions using a newly developed closed kinetic chain (CKC) leg press exercise device. Muscle force and electromyogram (EMG) measurements during maximum voluntary isometric leg presses (MVC-CKC) were performed on 6 healthy women in 6 different knee flexion angles (15°, 30°, 45°, 60°, 75°, 90°) and 2 different postures (supine and trunk upright posture). Results showed that the muscle force of MVC-CKC reached its peak at 60° knee flexion angle in both postures. Significant knee angle-dependent differences in EMG activity for both rectus femoris and gastrocnemius muscles were observed, while posture-dependent differences in EMG were found in biceps femoris. These particular joint-dependent EMG activities may be explained by the architectural characteristics of bi-articular muscles and muscle length-tension relationship theory. Co-activation of an antagonist muscle may appear with activation of the gastrocnemius muscle when the knee approaches full extension. Consequently, measurement of isometric CKC leg extension muscle force at 60° knee flexion angle in the trunk upright posture seems to be the optimal position.

Stretch‐induced force deficits in murine extensor digitorum longus muscles after cardiotoxin injection

A leftward shift in a muscle's length-tension relationship is thought to impair myofilament overlap. We hypothesized that left-shifted muscles would incur greater eccentric contraction-induced damage compared to controls. We evaluated contractile properties and force deficits in regenerating murine extensor digitorum longus (EDL) muscles 7, 14, and 21 days after cardiotoxin (CTX) injection. Specific tension recovered to control values by 21 days. CTX-injected muscles demonstrated left-shifted length-tension curves and incurred greater contraction-induced force deficits than controls (P < 0.001) on day 7. We speculate that increased contraction-induced damage in 7-day CTX-injected muscles results from changes in myofilament overlap that occurs during early regeneration.

Posture-dependent trunk extensor EMG activity during maximum isometrics exertions in normal male and female subjects

Posture-dependent trunk function data are important for appropriate normalization of submaximal trunk exertions, and is also necessary to define a more precise and specific use for strength testing in the prevention and diagnosis of spinal disorders. The aim of the current study was to quantify maximal effort trunk muscle extensor activity and trunk isometric extension torque over a functional range of sagittal standing postures. Twenty healthy, young adult male and female subjects performed isometric extension tasks over a sagittal posture range of –20° extension to +50° flexion, in 10° increments. Erector spinae muscle activity was recorded bilaterally at the level of L3 using surface EMG electrodes. Isometric trunk extension torque was measured using a trunk dynamometer. EMG and trunk torque differed significantly between genders, but there were no differences between male and female subjects when the data were normalized with respect to the upright posture. For the combined male and female population, upright posture normalized L3 EMG activity (EMG n) and trunk extension torque (T n) increased 1.7-fold and 3.5-fold, respectively, over the 70° range of sagittal postures examined. The ratio (T n/EMG n) increased two-fold (0.83 to 1.67) from –20° extension to +50° flexion, indicating that the neuromuscular efficiency increases with flexion. Trunk extension torque normalized with respect to the upright posture was linearly and positively correlated ( r=0.59, P<0.001) to similarly normalized L3 EMG activity. This relatively weak correlation suggests that trunk muscle synergism and/or intrinsic muscle length-tension relationships are also modulated by posture. This study provides data that can be used to estimate trunk extensor muscle function over a broad range of sagittal postures. Our findings indicate that appropriate postural normalization of trunk extensor EMG activity is necessary for studies where submaximal trunk exertions are performed over a range of upright postures.

Anatomic evaluation of the subcoracoid pectoralis major transfer in human cadavers

Subcoracoid transfer of the pectoralis major has recently been described as a reconstruction for subscapularis insufficiency. The purpose of this study was to examine the surgically relevant anatomy of this transfer. The importance of understanding this anatomy was recently highlighted to us following our encounter with musculocutaneous neuropraxia in 2 patients after transfer of the entire pectoralis major, one deep to the musculocutaneous nerve. Dissections were performed on 20 fresh, whole human cadavers in which the entire pectoralis major muscle, medial and lateral pectoral nerves, and musculocutaneous nerve were explored and quantified. The relationship between the pectoralis major and the conjoined tendon was studied in situ and after simulated transfers. The medial and lateral pectoral nerves were located far medial to the pectoralis major tendon insertion and appeared to be safe from injury as long as surgical dissection remained lateral to the pectoris minor and less than 8.5 cm from the humeral insertion. Transfer of the pectoralis major superficial to the musculocutaneous nerve created less tension than transfer deep to the musculocutaneous nerve. Because proximal innervation of the coracobrachialis and short head of the biceps is not an uncommon occurrence, a split pectoralis major transfer, release of the proximal musculocutaneous branches, or debulking of the pectoralis major muscle belly may be required in some instances to prevent tension on the nerve. Because of the variability and location of the musculocutaneous nerve, it should always be visualized operatively. Transfer of the pectoralis major tendon lateral to the biceps tendon appeared to best restore the muscle length-tension relationship. (J Shoulder Elbow Surg 2001;10:453-9.)

Selected contribution: effect of chronic passive length change on airway smooth muscle length-tension relationship.

The ability of rabbit trachealis to undergo plastic adaptation to chronic shortening or lengthening was assessed by setting the muscle preparations at three lengths for 24 h in relaxed state: a reference length in which applied force was approximately 1-2% of maximal active force (P(o)) and lengths considerably shorter and longer than the reference. Passive and active length-tension (L-T) curves for the preparations were then obtained by electrical field stimulation at progressively increasing muscle length. Classically shaped L-T curves were obtained with a distinct optimal length (L(o)) at which P(o) developed; however, both the active and passive L-T curves were shifted, whereas P(o) remained unchanged. L(o) was 72% and 148% that of the reference preparations for the passively shortened and lengthened muscles, respectively. The results suggest that chronic narrowing of the airways could induce a shift in the L-T relationship of smooth muscle, resulting in a maintained potential for maximal force production.

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Study of Influence Factor on Maximal Mouth Pressure. Part II. Influence of Trunk Flexion.

We studied the influence of posture on maximal mouth pressure in Part I. The study of Part II was aimed at determining the influence of trunk flexion on maximal mouth pressure. Nineteen healthy, young adult students from WCMAS comprised a STANDING study group, and 27 healthy, young adult students from IUHW comprised a LYING study group (same subjects of Part I). Maximal expiratory mouth pressure (PEmax) and maximal inspiratory mouth pressure (PImax) were measured at 0, 30, and 60 degrees of trunk flexion. Posture changes were significantly related to maximal mouth pressure values, and trunk flexion from the standing posture statistically influenced maximal mouth pressure. PEmax and PImax in standing were enhanced with trunk flexion. Respiratory muscle strength changes with trunk flexion, because respiratory muscle tension occurs with the change in interabdominal pressure and the muscle length-tension relationship.