Biomedical subjects

John P Scholz

Publications and source records attributed to John P Scholz.

At least 19 recordsLinked to original sources

PubMed2007

The use of flexible arm muscle synergies to perform an isometric stabilization task.

OBJECTIVE: To evaluate if functional synergies are comprised of flexible combinations of a small number of ensembles of upper limb muscles to stabilize a particular performance variable during a force production task. METHODS: Electromyographic (EMG) signals of wrist, elbow and shoulder muscles were recorded. Linear combinations of indices of the integrated EMG of nine muscles (muscle modes or M-modes) and their relationship to changes in the moment of force produced by the right arm of subjects about the horizontal axis of a handle were first determined. Uncontrolled manifold (UCM) analysis was performed to determine the extent to which variance of the M-modes acted to produce a consistent change in the moment of force. RESULTS: Subjects exhibited three M-modes, two of which were 'reciprocal' while the third mode was considered a co-contraction mode. The three M-modes were found to be combined to form synergies that produced a consistent change in the moment of force across repetitive trials. Variance in the M-mode space that led to consistent changes in the moment of force across repetitions was significantly higher than variance that tended to produce inconsistent changes in the moment of force. CONCLUSIONS: Flexible combinations of activations of ensembles of muscles are organized to stabilize the value of or produce consistent changes in the value of important performance variables. SIGNIFICANCE: The study of flexible muscle synergies in healthy individuals paves the way to understanding abnormal postural and movement patterns in individuals with neurological disorders.

Adult↗

PubMed2006

The role of kinematic redundancy in adaptation of reaching.

Although important differences exist between learning a new motor skill and adapting a well-learned skill to new environmental constraints, studies of force field adaptation have been used frequently in recent years to identify processes underlying learning. Most of these studies have been of reaching tasks that were each hand position was specified by a unique combination of joint angles. At the same time, evidence has been provided from a variety of tasks that the central nervous system takes advantage of the redundancy available to it when planning and executing functional movements. The current study attempted to determine whether a change in the use of joint motion redundancy is associated with the adaptation process. Both experimental and control subjects performed 160 trials of reaching in each of four adaptation phases, while holding the handle of a robot manipulandum. During the first and last adaptation phases, the robot motors were turned off. During phases 2 and 3 the motors produced a velocity-dependent force field to which experimental subjects had to adapt to regain relatively straight line hand movements during reaching to a target, while the motors remained off for the control group. The uncontrolled manifold (UCM) method was used to partition the variance of planar clavicle-scapular, shoulder, elbow and wrist joint movements into two orthogonal components, one (V(UCM)) that reflected combinations of joint angles that were equivalent with respect to achieving the average hand path and another (V(ORT)) that took the hand away from its average path. There was no change in either variance component for the control group performing 640 non-perturbed reaches across four 'pseudo-adaptation' phases. The experimental group showed adaptation to reaching in the force field that was accompanied initially by an increase in both components of variance, followed by a smaller decrease of V(UCM) than V(ORT) during 320 practice reaches in the force field. After initial re-adaptation to reaching to the null field, V(UCM) was higher in experimental than in control subjects after performing a comparable number of reaches. V(UCM) was also larger in the experimental group after re-adaptation when compared to the 160 null field reaching trials performed prior to initial force field introduction. The results suggest that the central nervous system makes use of kinematic redundancy, or flexibility of motor patterns, to adapt reaching performance to unusual force fields, a fact that has implications for the hypothesis that motor adaptation requires learning of formal models of limb and environmental dynamics.

Adaptation, Physiological↗

PubMed2006

Effects of movement frequency and joint kinetics on the joint coordination underlying bimanual circle drawing.

Ten healthy participants performed bimanual symmetric and asymmetric circle drawing at 4 frequencies. The authors partitioned the variance of the joint configuration across repetitions into 1 component representing equivalent joint configurations with respect to achieving stability of the mean hand path (i.e., goal-equivalent variance, GEV) and 1 component leading to a variable hand path (non-goal-equivalent variance, NGEV) across cycles. Higher frequencies led to increased NGEV related to control of the nondominant hand and to the relative position and orientation between the hands during asymmetric drawing. The results were related to differences in muscle and interaction moments between the arms, and they suggest a possible relationship between the ability to use intersegmental forces and the stability of interlimb synergy.

Adult↗

PubMed2005

Workspace location influences joint coordination during reaching in post-stroke hemiparesis.

The purpose of this study was to determine the influence of workspace location on joint coordination in persons with post-stroke hemiparesis when trunk motion was required to complete reaches beyond the arm's functional reach length. Seven subjects with mild right hemiparesis following a stroke and seven age and gender matched control subjects participated. Joint motions and characteristics of hand and trunk movement were measured over multiple repetitions. The variance (across trials) of joint combinations was partitioned into two components at every point in the hand's trajectory using the uncontrolled manifold approach; the first component is a measure of the extent to which equivalent joint combinations are used to control a given hand path, and reflects performance flexibility. The second component of joint variance reflects the use of non-equivalent joint combinations, which lead to hand path error. Compared to the control subjects, persons with hemiparesis demonstrated a significantly greater amount of non-equivalent joint variability related to control of the hand's path and of the hand's position relative to the trunk when reaching toward the hemiparetic side (ipsilaterally), but not when reaching to the less involved side. The relative timing of the hand and trunk was also altered when reaching ipsilaterally. The current findings support the idea that the previously proposed "arm compensatory synergy" may be deficient in subjects with hemiparesis. This deficiency may be due to one or a combination of factors: changes in central commands that are thought to set the gain of the arm compensatory synergy; a limited ability to combine shoulder abduction and elbow extension that limits the expression of an appropriately set arm compensatory synergy; or a reduction of the necessary degrees-of-freedom needed to adequately compensate for poor trunk control when reaching ipsilaterally.

Adaptation, Physiological↗

PubMed2005

Joint coordination during quiet stance: effects of vision.

Stabilization of the center of mass (CM) is an important goal of the postural control system. Coordination of several joints along the human "pendulum" is required to achieve this goal. We studied the coordination among body segments with respect to horizontal CM stabilization during a quiet stance task and the effects of vision on CM stability. Subjects were asked to stand quietly on a narrow wooden block supporting only the mid-foot, with either open (EO) or closed (EC) eyes on separate trials. Instant equilibrium points (IEPs) in the center of pressure (CP) trajectory were determined when the horizontal component of the ground reaction force was zero and the CP data were decomposed into their rambling and trembling components. The joint angle, CM and CP data were divided into short cycles (time-normalized to 100 data points) or longer segments (time-normalized to 1000 data points) of equal length beginning and ending in an IEP. Motor abundance with respect to patterns of joint coordination was evaluated using the uncontrolled manifold (UCM) approach. Here, a UCM is a subspace spanning all joint combinations resulting in a given CM position. All combinations of joint angles that lie within this subspace are equivalent with respect to that CM position while joint angle combinations lying in a subspace orthogonal to the UCM lead to deviation from that CM position. UCM analysis was performed on data organized either across time within longer segments or at each point in time across multiple segments or across multiple cycles. Regardless of method of analysis, most of the variance in joint space was constrained to be within the UCM, preserving the mean CM position in both the EO and EC conditions. Joint configuration variance was significantly higher in the EC than in the EO condition although this increase occurred primarily within the UCM rather than in the orthogonal subspace that would have led to variation of the CM position. These results demonstrate the ability of the control system to selectively "channel" motor variability into directions in joint space that stabilize the CM position. This effect was enhanced when the task was made more challenging in the absence of vision. There was also a significant relationship between joint variance that led to a change in the CM position and, in particular, the rambling component of the CP path, lending some support to the idea that the CNS prescribes a certain stable trajectory of the CP during quiet stance that leads to a small controlled movement of the CM.

Adult↗

PubMed2005

Unilateral vs. bilateral coordination of circle-drawing tasks.

The number of joint motions available in the upper extremity provides for multiple solutions to the coordination of a motor task. Making use of these abundant joint motions provides for task flexibility. Controlling bimanual movements poses another level of complexity because of possible tradeoffs between coordination within a limb and coordination between the limbs. We examined how flexible patterns of joint coordination were used to stabilize the hand's path when drawing a circle independently compared to a bimanual pattern. Across-trial variance of joint motions was partitioned into two components: goal-equivalent variance (GEV), representing variance of joint motions consistent with a stable hand path and non-goal-equivalent variance (NGEV) representing variance of joint motions that led to deviations of the hand's path. GEV was higher than NGEV in both unimanual and bimanual drawing, with one exception. Both GEV and NGEV, related to control of the individual hands' motion, decreased when engaged in the bimanual compared to unimanual drawing. Moreover, NGEV, leading to variability in the vectorial distance between the hands, was higher when the two hands drew circles in a bimanually asymmetric vs. symmetric pattern, consistent with reported differences in the relative phasing of the two hands. Our results suggest that the nervous system controls the individual hands' motions by separate intra-limb synergies during both unimanual and bimanual drawing, and superimposes an additional synergy to achieve stable relative motion of the two hands during bimanual drawing.

Adult↗

PubMed2005

The effect of workspace on the use of motor abundance.

The uncontrolled manifold approach was used to examine the effect of workspace location on the use of motor abundance to control the hand's path during reaching. Participants pointed to targets located in the contralateral and ipsilateral workspaces at two different distances. When reaching to all parts of the workspace, the component of joint configuration variance consistent with an identical hand path across trials was significantly higher than the component of joint configuration variance leading to a variable hand path. The relative magnitude of this difference was affected primarily by target orientation and minimally by target distance. The control of hand-path direction when reaching ipsilaterally was associated with more selective use of motor abundance compared to reaching contralaterally. The control of hand-path extent was not affected by target orientation. Biomechanical factors are discussed as possible reasons that lead to the observed selective workspace effects.

Adult↗

PubMed2005

Postural synergies and their development.

The recent developments of a particular approach to analyzing motor synergies based on the principle of motor abundance has allowed a quantitative assessment of multi-effector coordination in motor tasks involving anticipatory adjustments to self-triggered postural perturbations and in voluntary postural sway. This approach, the uncontrolled manifold (UCM) hypothesis, is based on an assumption that the central nervous system organizes covariation of elemental variables to stabilize important performance variables in a task-specific manner. In particular, this approach has been used to demonstrate and to assess the emergence of synergies and their modification with motor practice in typical persons and persons with Down syndrome. The framework of the UCM hypothesis allows the formulation of testable hypotheses with respect to developing postural synergies in typically and atypically developing persons.

Central Nervous System↗

PubMed2004

Muscle modes during shifts of the center of pressure by standing persons: effect of instability and additional support.

Muscle synergies in postural tasks have recently been studied using the framework of the uncontrolled manifold (UCM) hypothesis. A set of three hypothetical control variables, named M-modes, derived from the activity of 11 postural muscles, were identified. It was shown that postural synergies composed of these three M-modes preserve a certain shift of the center of pressure (COP) when subjects perform postural tasks while standing on a stable surface. In the present study we investigated the effects of support surface instability and availability of a light touch or grasp of a stable external support on the M-modes and their co-variation. The study was performed in two sessions. In the first session subjects released a load behind the body under four conditions: standing on a stable surface with no support (ST), standing on an unstable surface with no support (UN), standing on an unstable surface with a light touch (UN,T) and standing on an unstable surface with grasp of a stable object (UN,G). In the second session subjects performed two tasks: an arm movement backward and voluntary sway forward (towards the toes) under three conditions--ST, UN and UN,T. Principal component analysis was used to identify M-modes from data in the first session, and a UCM analysis was performed to study M-mode synergies in postural stabilization from data in the second session. A 'menu' of five M-modes was found, which were named either reciprocal M-modes or co-contraction M-modes based on the agonist-antagonist relationship of muscles comprising each mode. For a given task, subjects chose any three of these five M-modes in a subject- and task-specific manner. The reciprocal and co-contraction M-modes occurred equally frequently whether subjects stood on a stable or unstable support surface or whether a light touch was available or not. However, the co-contraction M-modes predominated when grasp of an object was available. In this condition, when the arm could be used for stabilization, there were M-modes uniting hip and shoulder muscles. However, the identified M-mode synergies were not found to lead to a consistent shift in the COP in any of the stability conditions. Possible reasons for this finding are discussed.

Adult↗

PubMed2004

Finger interaction during accurate multi-finger force production tasks in young and elderly persons.

We addressed a hypothesis that changes in indices of finger interaction during maximal force production (MVC) tasks are accompanied by changed coordination of fingers in multi-finger accurate force production tasks. To modify relative involvement of extrinsic and intrinsic hand muscles, the subjects produced force by pressing either at their distal phalanges or at their proximal phalanges. As in earlier studies, in MVC trials, the elderly subjects showed a greater force decline when pressing at the proximal phalanges as compared to pressing at the distal phalanges. Two methods were applied to analyze finger coordination during the task of four-finger force production from zero to 30% of MVC over 5 s, at the level of finger forces (performance variables) and at the level of modes (control variables). Our previous observations of higher indices of variability during the ramp task in elderly subjects have been generalized to both sites of force application. An index of finger force covariation (the difference between the variance of the total force and the sum of the variances of individual finger forces) revealed small age related differences, which did not depend on the site of the force application. In contrast, analysis of covariation of force modes within the uncontrolled manifold (UCM) hypothesis showed much better stabilization of the time profile of the total force by young subjects. The UCM hypothesis was also used to test stabilization of the pronation/supination moment during the ramp task. Young subjects showed better moment stabilization than elderly. Age related differences in both force- and moment-stabilization effects were particularly strong during force application at the proximal phalanges. We conclude that the drop in MVC is accompanied in elderly subjects with worse coordination of control signals to fingers in multi-finger tasks. The UCM analysis was more powerful as compared to analysis of force variance profiles in revealing significant differences between the groups. This general result underscores the importance of efforts to analyze motor coordination using control rather than performance variables.

Adult↗

PubMed2004

High-arched runners exhibit increased leg stiffness compared to low-arched runners.

Leg stiffness between high-arched (HA) and low-arched (LA) runners was compared. It was hypothesized that high-arched runners would exhibit increased leg stiffness, increased sagittal plane support moment, greater vertical loading rates, decreased knee flexion excursion and increased activation of the knee extensor musculature. Twenty high-arched and 20 low-arched subjects were included in this study. Leg stiffness, knee stiffness, vertical loading rate and lower extremity support moment were compared between groups. Electromyographic data were collected in an attempt to explain differences in leg stiffness between groups. High-arched subjects were found to have increased leg stiffness and vertical loading rate compared to low-arched runners. Support moment at the impact peak of the vertical ground reaction force was related to leg stiffness across all subjects. High-arched subjects demonstrated decreased knee flexion excursion during stance. Finally, high-arched subjects exhibited a significantly earlier onset of the vastus lateralis (VL) than the low-arched runners. Differences exist in leg stiffness and vertical loading rate between runners with different foot types. Differences in lower extremity kinetics in individuals with different foot types may have implications for new treatment strategies or preventative measures.

Adolescent↗

PubMed2003

Aspects of joint coordination are preserved during pointing in persons with post-stroke hemiparesis.

Understanding the fundamental deficits that underlie abnormal reaching movements in persons with hemiparesis is important to the development of rehabilitation approaches for these persons. The purpose of the present study was to investigate whether, and to what extent, persons with hemiparesis retain the ability to exploit motor abundance to coordinate their joint motions to control the hand's path during reaching--a general feature of joint coordination in age-matched control persons. Eight subjects with mild to moderate right hemiparesis following a stroke and seven age and gender matched control subjects performed pointing movements with each arm individually to targets in the contralateral and ipsilateral workspaces. Ten joint motions and characteristics of hand movement were measured over multiple repetitions. The variance (across trials) of joint combinations was partitioned into two components at every point in the hand's trajectory; joint variance that led to a consistent hand position and joint variance that led to an inconsistent hand position from trial to trial. All participants were able to limit joint configurations that would have led to trial-to-trial variance of the hand's path, while using a range of joint configurations consistent with a stable hand path. These results demonstrate that persons with mild to moderate hemiparesis and no measured sensory or perceptual deficits utilized available motor abundance to stabilize performance variables that were important to successful completion of a reaching task, just as was found for age-matched control persons. A principal components analysis of joint angle variance across several points in the movement cycle demonstrated that the persons with hemiparesis showed different patterns of joint couplings during reaching compared with the age-matched control persons; this was particularly evident for the more impaired individuals. These findings were related to the two features of synergy as proposed by other workers. It is suggested that these results support the idea that, while subjects with mild-to-moderate hemiparesis demonstrate differences in the feature of a synergy related to the specific patterns of joint coupling, they retain the feature of a synergy that is related to error compensation.

Aged↗

PubMed2003

Uncontrolled manifold analysis of single trials during multi-finger force production by persons with and without Down syndrome.

Recently, the framework of the uncontrolled manifold (UCM) hypothesis has been used to study multi-finger synergies based on analysis of motor variability across large sets of trials. We introduce a similar method of analysis, which can be applied to single trials, and hence may be more relevant to studies of atypical populations. In one experiment, results of across-trials and single-trial UCM analysis were compared for control participants who performed accurate ramp force production trials by pressing with four fingers of the hand. Both types of analysis revealed selective stabilization of total force by co-variations of individual finger forces. The stabilization was more pronounced at higher forces. When the participants purposefully varied the relative involvement of fingers during the ramp, significantly higher UCM effects were observed. However, high-pass filtering of the data at 4 Hz made these results similar to those observed in trials with natural patterns of force production. These observations allow assessment of the contribution of processes at two levels of a hypothetical hierarchical control system to the stabilization of total force. We also applied the single-trial UCM method to re-analyze previously published data from another experiment to study the motor variability in a group of persons with Down syndrome (DS) because these persons have difficulty in motor planning and timing as well as in force stabilization. Results of single-trial UCM analysis demonstrated force stabilization in these persons. The degree of force stabilization improved significantly after three days of practice. The analysis also showed that the total pronation/supination moment generated by the four fingers with respect to the midpoint was stabilized. The degree of moment stabilization did not change with practice. We conclude that the single-trial method of UCM analysis allows the analysis of hypotheses about stabilization of different performance variables by alleged multi-finger synergies in both typical individuals and individuals with DS.

Adolescent↗

PubMed2003

Muscle synergies during shifts of the center of pressure by standing persons.

Movements by a standing person are commonly associated with adjustments in the activity of postural muscles to cause a desired shift of the center of pressure (COP) and keep balance. We hypothesize that such COP shifts are controlled (stabilized) using a small set of central variables (muscle modes, M-modes), while each M-mode induces changes in the activity of a subgroup of postural muscles. The main purpose of this study has been to explore the possibility of identification of muscle synergies in a postural task using the framework of the uncontrolled manifold (UCM) hypothesis employing the following three steps in data analysis: (i) Identification of M-modes: Subjects were asked to release a load from extended arms through a pulley system, resulting in a COP shift forward prior to load release. Electromyographic (EMG) activity of eleven postural muscles on one side of the body was integrated over a 100 ms interval corresponding to the early stage of the COP shift, and subjected to a principal component (PC) analysis across multiple repetitions of each task. Three PCs were identified and associated with a 'push-back M-mode', a 'push-forward M-mode' and a 'mixed M-mode'. (ii) Calculation of the Jacobian of the system, which relates changes in the magnitude of M-modes to COP shifts using regression techniques: Subjects performed three different tasks (releasing different loads at the back, voluntarily shifting body weight forward and backward, at different speeds) to verify if the relationship between magnitudes of M-modes and COP shifts is task or direction specific. (iii) UCM analysis: Three tasks were chosen (load release in the front, arm movement forward and backward) which were associated with an early shift in COP. A manifold was identified in the M-mode space corresponding to a certain average (across trials) shift of the COP and variance per degree of freedom within the UCM (V(UCM)) and orthogonal (V(ORT)) to the UCM was computed. Across subjects, V(UCM) was significantly higher than V(ORT) when analysis at the third step was performed using a Jacobian computed based on a set of tasks associated with a COP shift in the same direction but not in the opposite direction. This result confirms our hypothesis that the M-modes work together as a synergy to stabilize a desired shift of the COP. Forward and backward COP shifts are associated with different synergies based on the same three M-modes.

Adult↗

PubMed2003

Effect of accuracy constraint on joint coordination during pointing movements.

Given the number of muscles and joints of the arm, more ways are available to produce an identical hand movement when pointing to a target than are strictly necessary. How the nervous system manages these abundant degrees of freedom was the focus of this study of pointing to targets of low and high indices of difficulty (ID). Two essential features of movement synergies were examined. The first reflects the preferred relations among the outputs of each movement element and was studied through principal component analysis. The second feature of synergy reflects the flexibility of those relationships evidenced by the use of multiple, goal-equivalent solutions to joint coordination. This second feature, which is the main focus of this report, was studied using the uncontrolled manifold approach. Motor abundance was defined operationally as the component of variance of joint combinations that left unchanged the value of important performance variables (goal-equivalent variability, GEV). This variance component was contrasted with the component of variance leading to a change in the value of these variables (non-goal-equivalent variability, NGEV). The difference between GEV and NGEV was evaluated with respect to the performance variables movement extent, movement direction, and path of the arm's center of mass. More than 90% of the variance of joint motions across the pointing trial were accounted for by one principal component, indicating a consistent temporal coupling among most joint motions in a single functional synergy. The flexible nature of this synergy was revealed by the variability analysis. All subjects had significantly higher GEV than NGEV for most of the movement path. Thus, variable patterns of joint coordination did not represent noise but the use of equivalent coordinative solutions related to stabilizing important performance variables. Higher GEV than NGEV was present regardless of the task's ID. One exception was at the time of peak velocity, leading to poorer control of movement extent than movement direction. Increasing the task's ID led to an overall reduction of joint configuraion variance, particularly GEV. These results support earlier work indicating that the use of goal-equivalent solutions to joint coordination is a common feature of the control of this and many other motor tasks. Functionally important performance variables appear to be controlled through flexible but task-specific coordination among the motor elements.

Adult↗

PubMed2003

A mode hypothesis for finger interaction during multi-finger force-production tasks.

Finger forces are known to change involuntarily during multi-finger force-production tasks, even when a finger's involvement in a task is not consciously changed (the enslaving effect). Furthermore, during maximal force-production (MVC) tests, the force produced by a given finger in a multi-finger task is smaller than the force generated by this finger in its single-finger MVC test (the force-deficit effect). A set of hypothetical control variables - modes - is introduced. Modes can be estimated based on individual finger forces during single-finger MVC tests. We show that a simple formal model based on modes with only one free parameter accounts for finger forces during a variety of multi-finger MVC tests. The free parameter accounts for the force-deficit effect, and its value depends only on the number of explicitly involved fingers. This approach offers a simple framework for the analysis of finger interaction during multi-finger actions.

Biomechanical Phenomena↗

PubMed2002

Understanding finger coordination through analysis of the structure of force variability.

Most common motor acts involve highly redundant effector systems. Understanding how such systems are controlled by the nervous system is a long-standing scientific challenge. Most proposals for solving this problem are based on the assumption that a particular solution, which optimizes additional constraints, is selected by the nervous system out of the many possible solutions. This study attempts to address this question in the context of coordinating individual finger forces to produce a controlled total force oscillation between 5% and 35% of each subject's maximum force of voluntary contraction, under two different combinations of four fingers. The structure of variability of individual finger forces was evaluated with respect to hypotheses that, at each instance in time, subjects attempt to: (1) stabilize the value of total force and (2) stabilize the total moment created by the fingers about the long axis passing through the forearm and midline of the hand. The results provide evidence that a range of goal-equivalent finger force combinations is generated to stabilize the values of total force and the total moment. The control of total force was specified explicitly by the task. However, it was stabilized only near the time of peak force. In contrast, the total moment was stabilized throughout most of the force cycle. The results lead to the suggestion that successful task performance is achieved, not by selecting a single optimal solution, but by discovering an appropriate control law that selectively stabilizes certain combinations of degrees of freedom relevant to the task while releasing from control other combinations.

Adult↗

PubMed2002

Coordination underlying the control of whole body momentum during sit-to-stand.

The stability of linear and angular momentum of the center of mass (CM) and the underlying coordination of body segments was investigated for a sit-to-stand task to better understand how the nervous system organizes the redundant degrees of freedom available to accomplish this task. From the effector geometry, we derived a mathematical model relating body segment angles and their angular velocities (i.e. state space) to CM angular and linear momentum. We used this model to partition the variability of joint angle and joint velocity configurations into combinations that leave CM momentum invariant and combinations that do not leave CM momentum invariant. The results revealed that subjects used a range of different state-space combinations from trial to trial that were equivalent with respect to producing a stable value of angular and linear momentum. In contrast, body segment combinations that changed the value of momentum were more restricted. Most interesting was the finding that, when standing up under more challenging support surface conditions, the range of state-space combinations used to stabilize momentum was increased. That is, variability increased most strongly for those angle and angular velocity combinations that left CM momentum invariant, with smaller increases registered for combinations that affected CM momentum.

Adult↗