The Effect of Antagonist Muscle Sensory Input on Force Regulation.
ABSTRACT: The purpose of this study was to understand how stretch-related sensory feedback from an antagonist muscle affects agonist muscle output at different contraction levels in healthy adults. Ten young (25.3 ± 2.4 years), healthy subjects performed constant isometric knee flexion contractions (agonist) at 6 torque levels: 5%, 10%, 15%, 20%, 30%, and 40% of their maximal voluntary contraction. For half of the trials, subjects received patellar tendon taps (antagonist sensory feedback) during the contraction. We compared error in targeted knee flexion torque and hamstring muscle activity, with and without patellar tendon tapping, across the 6 torque levels. At lower torque levels (5%, 10%, and 15%), subjects produced greater knee torque error following tendon tapping compared with the same torque levels without tendon tapping. In contrast, we did not find any difference in torque output at higher target levels (20%, 30%, and 40%) between trials with and without tendon tapping. We also observed a load-dependent increase in the magnitude of agonist muscle activity after tendon taps, with no associated load-dependent increase in agonist and antagonist co-activation, or reflex inhibition from the antagonist tapping. The findings suggest that at relatively low muscle activity there is a deficiency in the ability to correct motor output after sensory disturbances, and cortical centers (versus sub-cortical) are likely involved.
Project description:BACKGROUND:In older persons, lower hand grip strength is associated with poorer cognition. Little is known about how the rate of muscle contraction relates to cognition and upper extremity motor function, and sex differences are understudied. METHODS:Linear regression, adjusting for age, race, education, body mass index, appendicular lean mass, and knee pain, assessed sex-specific cross-sectional associations of peak torque, rate of torque development (RTD), and rate of velocity development (RVD) with cognition and upper extremity motor function. RESULTS:In men (n = 447), higher rate-adjusted peak torque and a greater RVD were associated with faster simple finger tapping speed, and a greater RVD was associated with higher nondominant pegboard performance. In women (n = 447), higher peak torque was not associated with any measures, but a greater RTD was associated with faster simple tapping speed and higher language performance, and a greater RVD was associated with higher executive function, attention, memory, and nondominant pegboard performance. In women with low isokinetic peak torque, RVD was associated with attention and memory. CONCLUSIONS:RVD capacity may reflect neural health, especially in women with low muscle strength.
Project description:Introduction:The effect of chronic patellar tendinopathy on tissue function and integrity is currently unclear and underinvestigated. The aim of this cohort comparison was to examine morphological, material, and mechanical properties of the patellar tendon and to extend earlier findings by measuring the ability to store and return elastic energy in symptomatic tendons. Methods:Seventeen patients with chronic (>3 months, VISA-P < 80), inferior pole patellar tendinopathy (24 ± 4 years; male = 12, female = 5) were carefully matched to controls (25 ± 3 years) for training status, pattern, and history of loading of the patellar tendon. Individual knee extension force, patellar tendon stiffness, stress, strain, Young's modulus, hysteresis, and energy storage capacity, were obtained with combined dynamometry, ultrasonography, magnetic resonance imaging, and electromyography. Results:Anthropometric parameters did not differ between groups. VISA-P scores ranged from 28 to 78 points, and symptoms had lasted from 10 to 120 months before testing. Tendon proximal cross-sectional area was 61% larger in the patellar tendinopathy group than in the control group. There were no differences between groups in maximal voluntary isometric knee extension torque (p = 0.216; d < -0.31) nor in tensile tendon force produced during isometric ramp contractions (p = 0.185; d < -0.34). Similarly, tendon strain (p = 0.634; d < 0.12), hysteresis (p = 0.461; d < 0.18), and strain energy storage (p = 0.656; d < 0.36) did not differ between groups. However, patellar tendon stiffness (-19%; p = 0.007; d < -0.74), stress (-27%; p< 0.002; d < -0.90) and Young's modulus (-32%; p = 0.001; d < -0.94) were significantly lower in tendinopathic patients compared to healthy controls. Discussion:In this study, we observed lower stiffness in affected tendons. However, despite the substantial structural and histological changes occurring with tendinopathy, the tendon capacity to store and dissipate energy did not differ significantly.
Project description:PURPOSE:To develop a 3D adiabatic T1? prepared ultrashort echo time cones (3D AdiabT1? UTE-Cones) sequence for whole knee imaging on a clinical 3T scanner. METHODS:A train of adiabatic full passage pulses were used for spin locking, followed by time-efficient multispoke UTE acquisition to detect signals from both short and long T2 tissues in the whole knee joint. A modified signal model was proposed for multispoke UTE data fitting. The feasibility of this 3D AdiabT1? UTE-Cones technique was demonstrated through numerical simulation, phantom, and ex vivo knee sample studies. The 3D AdiabT1? UTE-Cones technique was then applied to 6 in vivo knee joints of healthy volunteers to measure T1? values of quadriceps tendon, patellar tendon, anterior cruciate ligament (ACL), posterior cruciate ligament (PCL), meniscus, patellar cartilage, and muscle. RESULTS:Numerical simulation, phantom and ex vivo knee sample studies demonstrated the feasibility of whole knee imaging using the proposed multispoke 3D AdiabT1? UTE-Cones sequence. The healthy volunteer knee study demonstrated an averaged T1? of 13.9?±?0.7 ms for the quadriceps tendon, 9.7?±?0.8 ms for the patellar tendon, 34.9?±?2.8 ms for the ACL, 21.6?±?1.4 ms for the PCL, 22.5?±?1.9 ms for the meniscus, 44.5?±?2.4 ms for the patellar cartilage, and 43.2?±?1.1 ms for the muscle. CONCLUSION:The 3D AdiabT1? UTE-Cones sequence allows volumetric T1? assessment of both short and long T2 tissues in the knee joint on a clinical 3T scanner.
Project description:OBJECTIVES:The purpose of this study was to compare the duration of high-intensity static stretching on flexibility and strength in the hamstrings. METHODS:Fourteen healthy males (20.8 ± 0.6 years, 170.7 ± 6.5 cm, 66.4 ± 9.9 kg) underwent high-intensity static stretching for three different durations (10, 15, and 20 seconds). The intensity of static stretching was set at the maximum point of discomfort. To examine the change in flexibility and strength, range of motion, peak passive torque, relative passive torque, muscle-tendon unit stiffness, peak torque of isokinetic knee flexion, and knee angle at peak torque of isokinetic knee flexion were measured. To evaluate a time course of pain, a numerical rating scale was described. RESULTS:Range of motion (P < 0.01), peak passive torque (P < 0.01), and knee angle at peak torque were increased at all interventions. Relative passive torque (P < 0.01) and muscle-tendon unit stiffness (P < 0.01) were decreased at all interventions. Peak torque decreased after 10 seconds of stretching (P < 0.05). Numerical rating scale during stretching was 8-9 levels in all interventions, the pain disappeared immediately after the post-measurements (median = 0). CONCLUSION:The results suggested that muscle-tendon unit stiffness decreased regardless of duration of high-intensity static stretching. However, peak torque of isokinetic knee flexion decreased after 10 seconds of high-intensity static stretching, though it was no change after for more than 15 seconds of stretching.
Project description:The bone-patellar tendon-bone has been widely used and considered a good graft source. The quadriceps tendon was introduced as a substitute graft source for bone-patellar tendon-bone. We compared the clinical outcomes of anterior cruciate ligament reconstructions using central quadriceps tendon-patellar bone and bone-patellar tendon-bone autografts. We selected 72 patients who underwent unilateral anterior cruciate ligament reconstruction using bone-patellar tendon-bone between 1994 and 2001 and matched for age and gender with 72 patients who underwent anterior cruciate ligament reconstruction using quadriceps tendon-patellar bone. All patients were followed up for more than 2 years. We assessed anterior laxity, knee function using the Lysholm and International Knee Documentation Committee scores, and quadriceps strength, the means of which were similar in the two groups. More patients (28 or 39%) in the bone-patellar tendon-bone group reported anterior knee pain than in the quadriceps tendon-patellar bone group (six patients or 8.3%). Anterior cruciate ligament reconstruction using the central quadriceps tendon-patellar bone graft showed clinical outcomes comparable to those of anterior cruciate ligament reconstruction using the patellar tendon graft, with anterior knee pain being less frequent in the former. Our data suggest the quadriceps tendon can be a good alternative graft choice.Level III Therapeutic study.
Project description:Habitual loading and resistance training (RT) can lead to changes in muscle and tendon morphology as well as in its mechanical properties which can be measured by Shear Wave Elastography (SWE) technique. The objective of this study was to analyze the Vastus Lateralis (VL) and patellar tendon (PT) mechanical properties adaptations to an 8-week RT protocol using SWE. We submitted 15 untrained health young men to an 8-week RT directed for knee extensor mechanism. VL and PT shear modulus (?) were assessed pre and post intervention with SWE. PT thickness (PTT), VL muscle thickness (VL MT) and knee extension torque (KT) were also measure pre and post intervention to ensure the RT efficiency. Significant increases were observed in VL MT and KT (pre = 2.40 ± 0.40 cm and post = 2.63 ± 0.35 cm, p = 0.0111, and pre = 294.66 ± 73.98 Nm and post = 338.93 ± 76.39 Nm, p = 0.005, respectively). The 8-week RT was also effective in promoting VL ? adaptations (pre = 4.87 ± 1.38 kPa and post = 9.08.12 ± 1.86 kPa, p = 0.0105), but not in significantly affecting PT ? (pre = 78.85 ± 7.37 kPa and post = 66.41 ± 7.25 kPa, p = 0.1287) nor PTT (baseline = 0.364 ± 0.053 cm and post = 0.368 ± 0.046 cm, p = 0.71). The present study showed that an 8-week resistance training protocol was effective in adapting VL ? but not PT ?. Further investigation should be conducted with special attention to longer interventions, to possible PT differential individual responsiveness and to the muscle-tendon resting state tension environment.
Project description:Residual torque enhancement (rTE) is a history-dependent property of muscle, which results in an increase in steady-state isometric torque production following an active lengthening contraction as compared to a purely isometric (ISO) contraction at the same muscle length and level of activation. Once thought to be only an intrinsic property of muscle, recent evidence during voluntary contractions indicates a neuromechanical coupling between motor neuron excitability and the contractile state of the muscle. However, the mechanism by which this occurs has yet to be elucidated. The purpose of this study was to investigate inhibition arising from tendon-mediated feedback (e.g., Golgi tendon organ; GTO) through tendon electrical stimulation (TStim) in the ISO and rTE states during activation-matching and torque-matching tasks. Fourteen male participants (22 ± 2 years) performed 10 activation-matching contractions at 40% of their maximum tibialis anterior electromyography amplitude (5 ISO/5 rTE) and 10 torque-matching contractions at 40% of their maximum dorsiflexion torque (5 ISO/5 rTE). During both tasks, 10 TStim were delivered during the isometric steady state of all contractions, and the resulting tendon-evoked inhibitory reflexes were averaged and analyzed. Reflex amplitude increased by ~23% in the rTE state compared to the ISO state for the activation-matching task, and no differences were detected for the torque-matching task. The current data indicate an important relationship between afferent feedback in the torque-enhanced state and voluntary control of submaximal contractions. The history-dependent properties of muscle is likely to alter motor neuron excitability through modifications in tension- or torque-mediated afferent feedback arising from the tendon.
Project description:Recent evidence suggests the patellar tendon undergoes buckling during normal knee flexion, which likely contributes to the functioning of the extensor mechanism. Thus, evaluating buckling in patients following total knee arthroplasty (TKA), where extensor mechanism dysfunction remains a common complication, may be relevant. The study goals were to identify whether post-TKA patients exhibit differences in patellar tendon buckling from healthy, similarly-aged adults and whether such buckling correlates with knee and patellar tendon health. Patellar tendon buckling was assessed during passive knee flexion using ultrasound in post-TKA patients (n?=?20; 12M, 68 ± 8 years) and compared with previously reported data from healthy adults (n?=?12; 12M; 70 ± 8 years). Patients exhibited significantly larger (p < 0.01) buckling magnitude and angles than healthy adults, and reduced distal buckling was linked with better Knee Society Scores (p?=?0.04, R2 = 0.24). The greater patellar tendon buckling observed in post-TKA patients could arise due to factors related to the surgery itself (e.g. infrapatellar fat pad resection) or it may be that post-TKA patients had greater patellar tendon buckling before their procedure. Alterations in patellar tendon buckling may predispose individuals to post-surgical complications including instability, anterior knee pain, and extensor mechanism dysfunction, with further work necessary to elucidate potential links.
Project description:It is believed that hormonal changes during pregnancy lead to an increased compliance in ligaments and tendons, increasing the risk to suffer from connective tissue injuries particularly during exercise. While the laxity of the pelvic ligaments may increase to facilitate childbirth, to our knowledge no study has ever investigated the mechanical properties of human tendons in different stages of pregnancy. Thus, the purpose of our longitudinal study was to investigate the mechanical properties of the patellar tendon in different stages of pregnancy and postpartum. Nineteen pregnant women (30 ± 4 years) and 11 non-pregnant controls (28 ± 3 years) performed maximum isometric knee extension contractions on a dynamometer. Muscle strength and mechanical properties of the patellar tendon were determined integrating ultrasound, kinematic, and electromyographic measurements. In pregnant women, measurements were performed in the 16 ± 4th week of pregnancy (EP), the 29 ± 4th week of pregnancy (LP) and 32 ± 9th weeks postpartum (PP). On average, muscle strength as well as patellar tendon stiffness, force, and relative strain did not change during pregnancy and did not differ from non-pregnant controls. Tendon length measured at 90° knee flexion continuously increased during and after pregnancy (tendon length PP>EP; PP>controls). Our results indicate that patellar tendon stiffness is not universally affected by pregnancy. We found no evidence to support the often stated assumption that tendons would become more compliant during pregnancy. However, variability between individuals as well as the progressive increase in tendon rest length during and after pregnancy and its implications on injury risk need to be further examined.
Project description:Synovial lipoma of the patellar tendon is a very rare entity. It can be associated with rupture of the patellar tendon. We present a case of synovial lipoma that was successfully resected endoscopically. The other indications for patellar tendoscopy include chronic patellar tendinitis and tendinosis, recalcitrant bursitis around the tendon, Osgood-Schlatter disease, and jumper's knee. The major potential danger of this endoscopic procedure is iatrogenic damage to the patellar insertion during endoscopic debridement in patients with jumper's knee or the tibial insertion during endoscopic debridement in patients with Osgood-Schlatter disease.