Biarticular Thigh Muscles Research Articles

Enhancing postural stability in a musculoskeletal hopping robot through stretch reflex application on biarticular thigh muscles

Enhancing postural stability in a musculoskeletal hopping robot through stretch reflex application on biarticular thigh muscles

Sex influence on muscle synergies in a ballistic force-velocity test during the delayed recovery phase after a graded endurance run

The acute and delayed phases of the functional recovery pattern after running exercise have been studied mainly in men. However, it seems that women are less fatigable and/or recover faster than men, at least when tested in isometric condition. After a 20 km graded running race, the influence of sex on the delayed phase of recovery at 2–4 days was studied using a horizontal ballistic force-velocity test. Nine female and height male recreational runners performed maximal concentric push-offs at four load levels a week before the race (PRE), 2 and 4 days (D2 and D4) later. Ground reaction forces and surface electromyographic (EMG) activity from 8 major lower limb muscles were recorded. For each session, the mechanical force-velocity-power profile (i.e. theoretical maximal values of force (F¯ 0), velocity (V¯ 0), and power (P¯ max)) was computed. Mean EMG activity of each recorded muscle and muscle synergies (three for both men and women) were extracted. Independently of the testing sessions, men and women differed regarding the solicitation of the bi-articular thigh muscles (medial hamstring muscles and rectus femoris). At mid-push-off, female made use of more evenly distributed lower limb muscle activities than men. No fatigue effect was found for both sexes when looking at the mean ground reaction forces. However, the force-velocity profile varied by sex throughout the recovery: only men showed a decrease of both V¯ 0 (p < 0.05) and P¯ max (p < 0.01) at D2 compared to PRE. Vastus medialis activity was reduced for both men and women up to D4, but only male synergies were impacted at D2: the center of activity of the first and second synergies was reached later. This study suggests that women could recover earlier in a dynamic multi-joint task and that sex-specific organization of muscle synergies may have contributed to their different recovery times after such a race.

Biarticular muscles are most responsive to upper-body pitch perturbations in human standing

Balancing the upper body is pivotal for upright and efficient gait. While models have identified potentially useful characteristics of biarticular thigh muscles for postural control of the upper body, experimental evidence for their specific role is lacking. Based on theoretical findings, we hypothesised that biarticular muscle activity would increase strongly in response to upper-body perturbations. To test this hypothesis, we used a novel Angular Momentum Perturbator (AMP) that, in contrast to existing methods, perturbs the upper-body posture with only minimal effect on Centre of Mass (CoM) excursions. The impulse-like AMP torques applied to the trunk of subjects resulted in upper-body pitch deflections of up to 17° with only small CoM excursions below 2 cm. Biarticular thigh muscles (biceps femoris long head and rectus femoris) showed the strongest increase in muscular activity (mid- and long-latency reflexes, starting 100 ms after perturbation onset) of all eight measured leg muscles which highlights the importance of biarticular muscles for restoring upper-body balance. These insights could be used for improving technological aids like rehabilitation or assistive devices, and the effectiveness of physical training for fall prevention e.g. for elderly people.

Concerted Control of Stance and Balance Locomotor Subfunctions—Leg Force as a Conductor

In human locomotion, the complex structure of the human body is controlled such that conceptual models (e.g., the spring-loaded-inverted-pendulum model) can describe the significant features. This suggests that the interplay of the complex control and musculoskeletal systems projects into a low-dimensional space to perform different movements. Such simplification can involve splitting the task into different modular control subproblems (locomotor subfunctions) that can be solved individually. Here, we asked how two locomotor subfunctions, namely stance and balance, could be coordinated to generate repeatable and robust motor commands. We developed a simple neuromechanical hopping model, based on decoupling axial and perpendicular leg forces. For this, bouncing behaviors and trunk posture control can be addressed by a knee extensor muscle and biarticular thigh muscles, respectively. We suggest utilizing the leg force feedback as interplay among environment, body mechanics, and sensory control to synchronize the decoupled subfunctions. We evaluated this approach in push recovery, attenuating ground drop perturbations and by investigating its sensitivity to the reflex gain as the control parameter. Leg force feedback can improve robustness of hopping by generating rhythmic hopping patterns. Such a parsimony model-based control concept could simplify controlling assistive devices, such as exoskeletons and prostheses.

Ultrasound Features of the Proximal Hamstring Muscle-Tendon-Bone Unit.

The hamstring muscle complex is made by a group of posterior biarticular thigh muscles, originating at the ischial tuberosity, which extend the hip and flex the knee joint. Proximal hamstring injuries are frequent among athletes, commonly involving their long myotendinous junction during an eccentric contraction. In this pictorial essay, we describe the ultrasound technique to visualize the normal anatomy of the proximal hamstring muscle-tendon-bone complex and present ultrasound findings in patients with traumatic injuries and tendinopathies.

Unique muscularity in cyclists' thigh and trunk: A cross-sectional and longitudinal study.

This study examined the influence of regular training in competitive cycling on individual muscle volume of the thigh and psoas major cross-sectionally and longitudinally. T1-weighted magnetic resonance (MR) images of the trunk and right thigh were obtained from eight experienced varsity male cyclists (experience: > 4 years) and 10 untrained men (experiment 1), and from 12 (10 males, two females) varsity cyclists before and after competitive cycling training for 6 months (experiment 2). From the MR images, the volumes of each of the quadriceps femoris and hamstrings, total adductors, gracilis, sartorius, and psoas major were determined. The volumes of the monoarticular thigh muscles, semitendinosus, and psoas major muscles were significantly greater in the experienced cyclists than in the untrained men (experiment 1), and increased significantly after the competitive training for 6 months (experiment 2). In contrast, the volumes of the other biarticular thigh muscles were similar among the experienced cyclists and untrained men (experiment 1), and did not change by competitive cycling training (experiment 2). The results indicate that competitive cycling training induces muscle-specific hypertrophy of the synergistic muscles, especially between the monoarticular and biarticular muscles, leading to quantitative profiles of the musculature in experienced cyclists.

Electromyographic Amplitude vs. Concentric and Eccentric Squat Force Relationships for Monoarticular and Biarticular Thigh Muscles

This study examined the linearity of the electromyographic (EMG) amplitude vs. concentric and eccentric squat force relationships for monoarticular and biarticular thigh muscles. Fourteen resistance-trained men (mean age ± SD: 22 ± 2 years; estimated thigh muscle cross-sectional area: 221.9 ± 22.7 cm) performed concentric and eccentric squats using a novel testing device from 10 to 90% of their maximum average force. Surface EMG signals were detected from the right vastus lateralis, rectus femoris, and biceps femoris. Linear regression was used to examine the relationships between EMG amplitude and force, and repeated measures analyses of variance were used to assess differences among the muscles. Moderate-to-high coefficients of determination were found for the vastus lateralis for both concentric and eccentric testings (r = 0.587-0.992). For the biceps femoris, the mean linear slope coefficient was significantly greater for concentric vs. eccentric testing (0.044 vs. 0.013 μV RMS·N; p = 0.002; effect size = 1.44). Although EMG amplitude for the vastus lateralis and rectus femoris increased with changes in eccentric force output, the electrical activity of the biceps femoris remained stable. These results demonstrated that the EMG amplitude vs. force relationships for the vastus lateralis were linear, despite the fact that force production during the squat is related to the activation of muscles that must simultaneously function as agonists and antagonists. Our findings for eccentric force testing are in agreement with investigations showing reduced hip extensor activity during concurrent extension at the hip and knee joints.

Locomotor Strategy for Pedaling: Muscle Groups and Biomechanical Functions

A group of coexcited muscles alternating with another group is a common element of motor control, including locomotor pattern generation. This study used computer simulation to investigate human pedaling with each muscle assigned at times to a group. Simulations were generated by applying patterns of muscle excitations to a musculoskeletal model that includes the dynamic properties of the muscles, the limb segments, and the crank load. Raasch et al. showed that electromyograms, pedal reaction forces, and limb and crank kinematics recorded during maximum-speed start-up pedaling could be replicated with two signals controlling the excitation of four muscle groups (1 group alternating with another to form a pair). Here a four-muscle-group control also is shown to replicate steady pedaling. However, simulations show that three signals controlling six muscle groups (i.e., 3 pairs) is much more biomechanically robust, such that a wide variety of forward and backward pedaling tasks can be executed well. We found the biomechanical functions necessary for pedaling, and how these functions can be executed by the muscle groups. Specifically, the phasing of two pairs with respect to limb extension and flexion and the transitions between extension and flexion do not change with pedaling direction. One pair of groups (uniarticular hip and knee extensors alternating with their anatomic antagonists) generates the energy required for limb and crank propulsion during limb extension and flexion, respectively. In the second pair, the ankle plantarflexors transfer the energy from the limb inertia to the crank during the latter part of limb extension and the subsequent limb extension-to-flexion transition. The dorsiflexors alternate with the plantarflexors. The phasing of the third pair (the biarticular thigh muscles) reverses with pedaling direction. In forward pedaling, the hamstring is excited during the extension-to-flexion transition and in backward pedaling during the opposite transition. In both cases hamstrings propel the crank posteriorly through the transition. Rectus femoris alternates with hamstrings and propels the crank anteriorly through the transitions. With three control signals, one for each pair of groups, different cadences (or power outputs) can be achieved by adjusting the overall excitatory drive to the pattern generating elements, and different pedaling goals (e.g., smooth, or energy-efficient pedaling; 1- or 2-legged pedaling) by adjusting the relative excitation levels among the muscle groups. These six muscle groups are suggested to be elements of a general strategy for pedaling control, which may be generally applicable to other human locomotor tasks.

The role of cutaneous information in a contact control task of the leg in humans

The aim of this study was to examine the effect of loss of sensation in the plantar surface of the feet on the learning of a contact control task. It has previously been shown that the biarticular thigh muscles control the external force exerted by the feet by finely regulating the net knee and hip moments. Based on literature which demonstrates strong projections of cutaneous afferents on the motoneurones of biarticular muscles, it has been assumed that this regulation is controlled on the basis of information from the plantar mechanoreceptors of the feet. Subjects with diabetic neuropathy often exhibit marked sensory loss in the distal extremities and thus provide a useful model for studies of the role of afferent input in motor control. Twenty subjects with diabetes mellitus were divided equally between those who had significant peripheral neuropathy and those with no apparent signs of neuropathy. By means of quantitative sensory and motor testing it was possible to select two relatively homogeneous groups matched for age, gender, height, medication, leg strength, weight and duration of diabetes. The task was to learn to push on a force platform with the right foot in four given directions. The foot was not moved relative to the force platform. Visual feedback specifying the direction and magnitude of the ground reaction force was provided on a TV screen. Once subjects had learned to apply the correct force, they were required in the second part of the experiment to maintain a given force direction without visual feedback. Force data and position data were collected and EMG activity was recorded for six muscles of the upper leg. The results showed that all subjects from both groups increased the time they stayed on the targets as they repeated the task ( p < 0.01). The accuracy of the task was significantly lower for the neuropathic group than the group with normal sensation ( p < 0.05). There were no differences between the two groups in the rate of improvement and both groups showed the same amount of drift of the applied force when visual feedback was removed. There were no significant differences between the two groups in the activation patterns of the thigh muscles. The activation of the biarticular muscles was increased as performance of the task improved and the correlation co-efficients between the activation pattern and the net joint moments improved. The results suggest that mechanoreceptors of the plantar surface of the feet play an important role in the accurate coordination of contact control leg tasks, although the role of other afferent inputs, which may also be degraded in diabetic neuropathy, cannot be excluded. However, this study could not demonstrate that the regulation of the net joint moments by the biarticular thigh muscles is based on information from the mechanoreceptors of the feet. The strong projections of cutaneous afferents on the motoneurones of biarticular muscles do not appear to play a role in the organization of the activation of muscles on an ongoing basis and may be primarily used to allow fast adjustments as a response to unexpected disturbances.

Two functional muscle groupings during postural equilibrium tasks in standing cats.

1. This study examined the relation between electromyographic (EMG) activation and the contact force and joint torques of the left hindlimb during postural equilibrium tasks in the standing cat. It is the appropriate application of force by the limbs against the support surface that allows the animal to control its center of mass and maintain equilibrium. 2. Cats were trained to stand quietly on a moveable force platform. During quiet stance, the cat was perturbed by a platform translation in each of 12 directions evenly spaced in the horizontal plane. EMG activity of mono- and biarticular thigh muscles, three-dimensional ground reaction force under the paw (contact force), and kinematics of the hindlimb segments were recorded Net joint torques were computed using inverse dynamics. The analysis focused on the functional organization of the rapid, automatic postural response in relation to the sagittal plane contact force and joint torques. 3. The muscles of the thigh were subdivided into two functional groups, based on the relationship of the evoked response to the various components of the sagittal plane contact force or joint torques. The first group, consisting of the monoarticular and some biarticular muscles, was correlated with the vertical force component, Fz. The second group, consisting of a separate group of biarticular muscles, was correlated with the difference between knee and hip torque. This torque difference is a function of both sagittal plane force components, Fz and Fy, and is related to contact force direction. 4. It is suggested that this subdivision of muscle activations reflects a neural strategy of parallel control of the two muscle groups in relation to their influence on Fz and Fy. Such a control mechanism could be a strategy for simplifying the control of the multisegmented limb in contact force tasks such as maintaining postural equilibrium.

EMG activities in mono- and bi-articular thigh muscles in combined hip and knee extension.

8 male subjects were tested to elucidate the organization of EMG activities in mono- and bi-articular thigh muscles when hip and knee extension are combined. 2 types of isometric movement, single and dual joint movements, were studied: 1) 20% of maximal voluntary contraction (MVC) in separate hip extension (HE20) and knee extension (KE20), 2) simultaneous HE20 and KE20, combined voluntarily (HE20.KE20). In HE20.KE20, the value of the integrated EMG (IEMG) from the muscles tested was normalized as a percentage (%IEMG) of the IEMG of each muscle in HE20 for gluteus maximus (GM) and semimembranosus (SM), and KE20 for vastus medialis (VM) and rectus femoris (RF). The average %IEMG was 50.5 +/- 16.9% for GM, 42.1 +/- 6.1% for SM, 153.4 +/- 22.8% for VM and 66.6 +/- 18.7% for RF. These data suggest that the EMG activities of GM, SM and RF are inhibited and the EMG activity of VM is facilitated by combining hip extension with knee extension.