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PubMed2003

The effect of age and movement speed on maximum forward reach from an elevated surface: a study in healthy women.

OBJECTIVE: To test the hypotheses (1) that the maximum distance reached by young or older women when standing on a raised platform is independent of movement speed, and (2) the maximum forward momentum generated at comfortable and fast reaching speeds is independent of age. DESIGN: Repeated measures case-control study in a university laboratory setting.Background. Maximum forward reach distance is often part of a geriatric mobility assessment. The effect of movement speed, and hence momentum, on forward reaching behavior is unknown in young or older subjects, despite the fact that excess momentum might increase the risk of fall-related injuries, especially from an elevated surface. METHODS: Ten healthy young women (mean age 23.7 years) and 10 healthy older women (mean age 70.5 years) participated. Subjects stood on an instrumented force platform and forward reach body segment kinematics were measured optoelectronically. Whole-body center of reaction and center of mass trajectories were calculated during six maximum forward reach trials: three performed "at a comfortable speed", and three performed "as fast as possible". RESULTS: Subjects reached slightly further at a comfortable speed than when reaching as fast as possible (P=0.016). Fast reaches were associated with a 25% increase in momentum (P<0.001; however, under both speed conditions, older women developed less whole-body momentum than did young controls (for example, 4.1 vs. 6.1 kgm/s at comfortable speed, P<0.05). Three young and one older women lost their balance in at least one trial. CONCLUSIONS: Independent of age, these women reached further when reaching slowly than when reaching rapidly, and older women restricted peak forward momentum under both speed conditions when standing on the elevated surface. RELEVANCE: Interventions designed to reduce falls from raised surfaces might utilize the insights gained from these women that (1) at any age, one cannot expect to reach as far when reaching fast as one can when reaching slowly; and (2) comfortable reaching speed is reduced in older individuals.

Adult↗

PubMed2005

Postural instability during reaching tasks in Parkinson's disease.

BACKGROUND AND PURPOSE: Reaching, like turning and rising from sitting, is an activity commonly associated with falls by people with Parkinson's disease. We set out to: (a) identify how people with moderate and severe Parkinson's disease performed high and low reaches and (b) to explore in detail the standard functional reach (functional reach) test and the fall histories of those who appeared unstable when reaching. METHOD: In this cross-sectional study, people with moderate or severe Parkinson's disease (Hoehn and Yahr Grade III or IV) were video-recorded at home, reaching above shoulder height and below knee level. Blinded observers rated stability, alignment, foot position, floor contact, use of support and reach type. Functional reach was also measured and participants were interviewed about falls. RESULTS: Of 51 participants, 33 (65%) had moderate Parkinson's disease and 18 (35%) severe. A greater proportion of the latter used support when reaching high (p = 0.029) and aligned forward when reaching low (p = 0.015); otherwise, strategies were similar across groups. Six people (all with severe Parkinson's disease) appeared unstable when reaching: they had a shorter functional reach than the others (median 10 cm versus 18 cm; p = 0.042) and had fallen frequently (median five falls in a year), although rarely when reaching. CONCLUSIONS: Reaching tasks challenge postural stability in severe Parkinson's disease. People who appear unstable when reaching are likely to be repeat-fallers and at risk of further falls during more demanding activities. Research should address whether discouraging potentially destabilizing manoeuvres (such as squatting and toe-standing) and promoting safety-enhancing strategies (such as using support and facing forward), with or without balance retraining, reduces the risk of falling among people with severe Parkinson's disease.

Accidental Falls↗

PubMed1996

Adaptive behavioral reactions of reaching in rats following discrete somatosensorimotor cortex lesions.

To test the effects of lesions of forelimb somatosensorimotor subareas on the reaching behavior, the rats were trained to reach for food pellets in a horizontal tube and through a grid. Reaching attempts were monitored by continual movement recording using magnetic induction and reaching success was quantitatively evaluated. In rats with bilateral lesions centered over the forelimb motor subarea (FMCL), reaches with the preferred forepaw were accompanied by reaching attempts with the nonpreferred forelimb. The latter declined over the recording period but larger residual movements were still observed at the end. Relative to control group, the performance of rats with FMCL was significantly decreased in both reaching tasks, however the reaching success into tube was significantly lower than through a grid. Rats with lesions centered over forelimb cutaneous representation (FCRL) showed signs of tactile deficit. Chosen reaching tactic represented an attempt to compensate for the tactile deficit. No reaches with the nonpreferred forepaw were observed. Relative to controls, the reaching success in rats with FCRL was decreased by the same amount in both reaching tasks. When reaching into the tube, the rats with FCRL performed significantly better than rats with FMCL over the whole recording period; when reaching through the grid no statistical difference in performance was observed between groups though the rats with FMCL performed better than the rats with FCRL. The discrete somatosensorimotor cortex lesions did not only result in different direct reaching deficits and performance, but also resulted in different behavioral reactions.

Animals↗

PubMedDate not supplied

Elderly nursing home and day care participants are less likely than young adults to approach imbalance during voluntary forward reaching.

The goal of this study was to determine whether differences exist between young and elderly adults in cautiousness or tendency to approach imbalance during a forward reaching task. Young (n = 26) and elderly (n = 25) adults participated in trials that required them to reach forward as quickly as possible to contact a target that moved back and forth, in and out of reach. "Voluntary reach" was calculated as the 75th percentile in reach distance over 20 trials. Measures were also acquired separately of "maximum attainable reach." Voluntary reach averaged 53% smaller in elderly than young subjects. This was due to differences in maximum attainable reach, and to increased cautiousness among elderly in approaching maximum attainable reach (voluntary reach averaged 65% +/- 23% of maximum attainable reach in elderly, and 95% +/- 5% in young; p < .001). Thus, cautiousness in approaching imbalance reduces voluntary reach in elderly but not young subjects. Furthermore, physical capacity (as measured by maximum attainable reach) and capacity utilization (as measured by voluntary reach) are independent predictors of reaching behavior among nursing home elderly.

Adult↗

PubMed2002

Cerebellar subjects show impaired coupling of reach and grasp movements.

We examined how cerebellar deficits in isolated reaching or grasping movements contribute to abnormalities in a combined reach and grasp movement, and whether people with cerebellar damage show abnormalities in the spatiotemporal relationships of reach and grasp movements. We studied subjects with cerebellar damage and matched controls as they performed a combined reach and grasp, an isolated reach, and an isolated grasp. These movements were performed under slow-accurate and fast speed conditions. Subjects were also tested for their ability to correctly estimate the target size based on visual information. We measured the three-dimensional position of the index finger, thumb and wrist joint during all tasks. Results showed that cerebellar subjects overestimated the target size to a greater extent than did controls. During movement testing, cerebellar subjects were impaired on isolated reach and isolated grasp. However, they did not worsen parameters of reach or grasp movements during the combined reach and grasp. Instead there were distinct deficits in the coupling of the reach and grasp movement. Compared with controls, cerebellar subjects showed abnormalities in the sequence of the reach and grasp movement and highly variable timing of peak grip aperture. In the slow-accurate condition, cerebellar subjects decomposed the reach and grasp movement into separate reach then grasp components, and produced multiple peaks in grip aperture. In the fast condition, cerebellar subjects did not decompose, produced a single peak grip aperture, and dropped the target more often. These results indicate that cerebellar damage can cause a specific breakdown in the coupling of reach and grasp movements. The cerebellum may be involved in combining reach and grasp movements into a single motor program.

Adult↗

PubMed2004

How do strength, sensation, spasticity and joint individuation relate to the reaching deficits of people with chronic hemiparesis?

Hemiparetic subjects present with movement deficits including weakness, spasticity and an inability to isolate movement to one or a few joints. Voluntary attempts to move a single joint often result in excessive motion at adjacent joints. We investigated whether the inability to individuate joint movements is associated with deficits in functional reaching. Controls and hemiparetic subjects performed two different reaching movements and three individuated arm movements, all in the parasagittal plane. The reaching movements were a sagittal 'reach up' (shoulder flexion and elbow flexion) and 'reach out' (shoulder flexion and elbow extension). Joint individuation was assessed by getting each subject to perform an isolated flexion-extension movement at each of the shoulder, elbow and wrist joints. In addition, we measured strength, muscle tone and sensation using standard clinical instruments. Hemiparetic subjects showed varying degrees of impairment when performing reaching movements and individuated joint movements. Reaching impairments (hand path curvature, velocity) were worse in the reach out versus the reach up condition. Typical joint individuation abnormalities were excessive flexion of joints that should have been held fixed during movement of the instructed joint. Hemiparetic subjects tended to produce concurrent flexion motions of shoulder and elbow joints when attempting any movement, one explanation for why they were better at the 'reach up' than the 'reach out' task. Hierarchical regression analysis showed that impaired joint individuation explained most of the variance in the reach path curvature and end point error; strength explained most of the variance in reaching velocity. Sensation also contributed significantly, but spasticity and strength were not significant in the model. We conclude that the deficit in joint individuation reflects a fundamental motor control problem that largely explains some aspects of voluntary reaching deficits of hemiparetic subjects.

Adult↗

PubMed2001

Role of primate magnocellular red nucleus neurons in controlling hand preshaping during reaching to grasp.

Reaching to grasp is of fundamental importance to primate motor behavior and requires coordinating hand preshaping with limb transport and grasping. We aimed to clarify the role of cerebellar output via the magnocellular red nucleus (RNm) to the control of reaching to grasp. Rubrospinal fibers originating from RNm constitute one pathway by which cerebellar output influences spinal circuitry directly. We recorded discharge from individual forelimb RNm neurons while monkeys performed a reach-to-grasp task and two tasks that were similar to the reach-to-grasp task in trajectory, amplitude, and direction but did not include a grasp. One of these, the device task, elicited reaches while holding a handle, and the other, the free-reach task, elicited reaches that did not require any specific hand use for task performance. The results demonstrate that coordinated whole-limb reaching movements are associated with large discharge modulations of RNm neurons predominantly when hand use is included. Therefore RNm neurons can at best only make a minor contribution to the control of reaching movements that lack hand use. We evaluated relations between the discharge of individual RNm neurons and electromyographic (EMG) activity of forelimb muscles during the reach-to-grasp task by comparing times of peak RNm discharge to times of peak EMG activity. The results are consistent with the view that RNm discharge may contribute to EMG activity of both distal and proximal muscles during reaching to grasp especially digit extensor and limb elevation muscles. Relations between the discharge of individual RNm neurons and movements of the metacarpi-phalangeal (MCP), wrist, elbow, and shoulder joints during individual trials of task performance were quantified by parametric correlation analyses on a subset of neurons studied during the reach-to-grasp and free-reach tasks. The results indicate that MCP extensions were consistently preceded by bursts of RNm discharge, and strong correlations were observed between parameters of discharge and the duration, velocity, and amplitude of corresponding MCP extensions. In contrast, relations between discharge and movements of proximal joints were poorly represented, and RNm discharge was not related to the speed of limb transport. Based on our data and those of others, we hypothesize that cerebellar output via RNm is specialized for controlling hand use and conclude that RNm may contribute to the control of hand preshaping during reaching to grasp by activating muscle synergies that produce the appropriate MCP extension at the appropriate phase of limb transport.

Animals↗

PubMed1985

The organization of eye and limb movements during unrestricted reaching to targets in contralateral and ipsilateral visual space.

The spatial and temporal organization of unrestricted limb movements directed to small visual targets was examined in two separate experiments. Videotape records of the subjects' performance allowed us to analyze the trajectory of the limb movement through 3-dimensional space. Horizontal eye movements during reaching were measured by infrared corneal reflection. In both experiments, the trajectories of the different reaches approximated straight line paths and the velocity profile revealed an initial rapid acceleration followed by a prolonged period of deceleration. In Experiment 1, in which the target light was presented to the right or left of a central fixation point at either 10 degrees or 20 degrees eccentricity, the most consistent differences were observed between reaches directed across the body axis to targets presented in the contralateral visual field and reaches directed at ipsilateral targets. Ipsilateral reaches were initiated more quickly, were completed more rapidly, and were more accurate than contralateral reaches. While these findings suggest that hemispherically organized neural systems are involved in the programming of visually guided limb movements, it was not clear whether the inefficiency of the contralateral movements was due to reaching across the body axis or reaching into the visual hemifield contralateral to the hand being used. Therefore, in Experiment 2, the position of the fixation point was varied such that the effects of visual field and body axis could be disembedded. In this experiment, the kinematics of the reaching movement were shown to be independent of the point of visual fixation and varied only as a function of the laterality of the target position relative to the body axis. This finding suggests that the kinematics of a reaching movement are determined by differences in the processing of neural systems associated with motor output, after the target has been localized in space. The effect of target laterality on response latency and accuracy, however, could not be attributed to a single frame of reference, or to a simple additive effect of both. These findings illustrate the complex integration of visual spatial information which must take place in order to reach accurately to goal objects in extrapersonal space. Comparison of ocular and manual performance revealed a close relationship between movement latency for both motor systems. Thus, rightward-going eye movements to a given target were initiated more quickly when accompanied by reaches with the right hand than when they were accompanied by reaches with the left hand.(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗

PubMed2006

Effect of bilateral reaching on affected arm motor control in stroke--with and without loading on unaffected arm.

PURPOSE: To investigate the effect of bilateral reaching, with/without inertial loading on the unaffected arm, on hemiparetic arm motor control in stroke. METHODS: Twenty unilateral stroke patients were recruited. A three-dimensional optical motion capture system was used to measure the movement trajectory of the hemiparetic arm while performing three tasks: affected limb reaching forward; two-limb reaching forward; and two-limb reaching forward with inertia loading of 25% upper limb weight on the unaffected limb, respectively. Kinematical parameters were utilized to quantify the reaching performance of the affected arm. RESULTS: No matter whether loading was applied on the unaffected arm or not, the bilateral reaching task did not significantly facilitate smoother and faster movement. Furthermore, during bilateral reaching task with/without loading on the unaffected arm, stroke patients showed slower movement, lower maximal movement velocity, feedback control dominant and discontinuous movements in the affected arm than the same task with unilateral reaching. Subjects showed the greatest active upper extremity range of motion in proximal joints during the bilateral reaching task without unaffected arm loading. The amount of trunk movement also increased during bilateral reaching either with or without loading on the unaffected arm. Patients with moderate upper extremity motor impairment performed more discontinuous movements and less active elbow range of motion during bilateral reaching tasks; however, those with mild upper extremity motor impairment performed smoother movements and demonstrated greater active elbow range of motion during bilateral reaching tasks. CONCLUSIONS: Bilateral reaching tasks with/without loading on the unaffected arm could be considered as adding challenges during motor control training. Training with bilateral arm movements may be considered as a treatment strategy, and can be incorporated in stroke rehabilitation to facilitate greater arm active movement and improve motor control performance in the affected arm.

Adult↗

PubMed2003

Coordinated turn-and-reach movements. I. Anticipatory compensation for self-generated coriolis and interaction torques.

When reaching movements involve simultaneous trunk rotation, additional interaction torques are generated on the arm that are absent when the trunk is stable. To explore whether the CNS compensates for such self-generated interaction torques, we recorded hand trajectories in reaching tasks involving various amplitudes and velocities of arm extension and trunk rotation. Subjects pointed to three targets on a surface slightly above waist level. Two of the target locations were chosen so that a similar arm configuration relative to the trunk would be required for reaching to them, one of these targets requiring substantial trunk rotation, the other very little. Significant trunk rotation was necessary to reach the third target, but the arm's radial distance to the body remained virtually unchanged. Subjects reached at two speeds-a natural pace (slow) and rapidly (fast)-under normal lighting and in total darkness. Trunk angular velocity and finger velocity relative to the trunk were higher in the fast conditions but were not affected by the presence or absence of vision. Peak trunk velocity increased with increasing trunk rotation up to a maximum of 200 degrees /s. In slow movements, peak finger velocity relative to the trunk was smaller when trunk rotation was necessary to reach the targets. In fast movements, peak finger velocity was approximately 1.7 m/s for all targets. Finger trajectories were more curved when reaching movements involved substantial trunk rotation; however, the terminal errors and the maximal deviation of the trajectory from a straight line were comparable in slow and fast movements. This pattern indicates that the larger Coriolis, centripetal, and inertial interaction torques generated during rapid reaches were compensated by additional joint torques. Trajectory characteristics did not vary with the presence or absence of vision, indicating that visual feedback was unnecessary for anticipatory compensations. In all reaches involving trunk rotation, the finger movement generally occurred entirely during the trunk movement, indicating that the CNS did not minimize Coriolis forces incumbent on trunk rotation by sequencing the arm and trunk motions into a turn followed by a reach. A simplified model of the arm/trunk system revealed that additional interaction torques generated on the arm during voluntary turning and reaching were equivalent to < or =1.8 g (1 g = 9.81 m/s(2)) of external force at the elbow but did not degrade performance. In slow-rotation room studies involving reaching movements during passive rotation, Coriolis forces as small as 0.2 g greatly deflect movement trajectories and endpoints. We conclude that compensatory motor innervations are engaged in a predictive fashion to counteract impending self-generated interaction torques during voluntary reaching movements.

Adult↗

PubMed1992

Properties of reach-related neuronal activity in cortical area 7A.

1. In protocol 1, two macaque monkeys were trained to reach to illuminated buttons with the right arm as reach-related unit activity was monitored in area 7a of the left hemisphere. 2. Of 402 neurons recorded in area 7a, 109 changed their discharge rates during the reach task. The change could occur early or late in the trajectory, or during the return movement of the arm to the rest plate. Spatial preferences were seen in 59/109 reach-related cells, usually for the right or center buttons. 3. In protocol 2, another monkey was trained to reach with either arm to targets displayed on a touch-sensitive video monitor. Of 273 neurons sampled in area 7a (both hemispheres) during the bilateral task performance, 84 were reach-related: 33 responded similarly to reaches of either arm. Most of the rest had a contralateral arm preference. When bilateral reach-related cells had a spatial preference, that preference was the same for both arms. 4. With the use of two target sequences in either protocol, it was found that spatial preferences were observable only for primary reaches from the side of the body up to the target. Relatively few cells responded to other trajectories, and those that did usually failed to discriminate movement direction. Movement extent did not influence discharge rates. 5. Although a total of 125/270 reach cells had observable visual responses, only 4 out of 18 cells tested in both dark and light conditions showed a significant drop in reach-related activity in the dark. Thus visual input from the moving hand probably is responsible for only part of the reach activity in area 7a. 6. Reach-related activity in area 7a appears to signal specific phases of the motor performance and is often restricted to distinct spatial regions. As such, it could be used by the frontal lobe to facilitate upcoming elements of a motor sequence, including terminal corrections.

Animals↗

PubMed1999

Impaired reaching and grasping after focal inactivation of globus pallidus pars interna in the monkey.

The purpose of this study was to test the hypothesis that the basal ganglia output from globus pallidus pars interna (GPi) contributes to inhibition of competing motor patterns to prevent them from interfering with a volitional movement. To test this hypothesis, the kinematics of a natural reach, grasp, and retrieval task were measured in the monkey before and after focal inactivation in GPi with the GABA(A) agonist muscimol. Two rhesus monkeys were trained to reach in a parasagittal plane to grasp a 1-cm cube of apple and retrieve it. Reflective markers were applied to the shoulder, elbow, wrist, and index finger. Movements were videotaped at 60 fields/s, digitized, and analyzed off-line. In each session the monkey performed 12-15 reaches before and 12-15 reaches after injection of 0.5 microl of 8.8 mM muscimol. Muscimol was injected into 22 separate locations in the "arm" area of GPi. Inactivation of the GPi with muscimol produced movement deficits in a reach-grasp-retrieve task that can be summarized as follows: 1) decreased peak wrist velocity during the reach to target; 2) decreased elbow and shoulder angular velocities, with elbow angular velocity relatively more impaired than shoulder angular velocity; resulting in 3) higher maximum vertical wrist and index finger positions at the apex of the reach; 4) prolonged latency from the end of the reach to the completion of grasp; and 5) less impairment of retrieval than reach, with inactivation at the majority of sites causing no impairment and some actually speeding up retrieval despite slow reaching. The results of this study show that reaching movements are impaired in a specific way after focal inactivation of GPi in previously normal monkeys. The slowing of the reach with normal (or fast) retrieval suggests that there is difficulty inhibiting the posture holding mechanisms that were active before the reach, but that assist the retrieval. The nature of the impairment supports the hypothesis that GPi lesions disrupt the ability to inhibit competing motor mechanisms to prevent them from interfering with desired voluntary movement.

Animals↗

PubMed1999

Neuronal activity in rat red nucleus during forelimb reach-to-grasp movements.

The activity of 259 task-related red nucleus neurons was recorded using chronic electrophysiological methods in free moving rats. Modulations in activity were analysed in relation to onset (first detected wrist movement) and end (arrival of the paw over the food) of a reach-to-grasp movement. Excitatory peaks were found to begin before, during and after the reach, but there were clear peaks in the distribution of onset times after reach-onset and before reach-end, reflecting the fact that one third of all peaks began specifically during the reach, although this occupied only a small fraction of the analysis time. Both excitations and inhibitions showed a strong tendency to end in close temporal association with reach-end. Analysis of excitatory modulation amplitudes showed that the largest peaks were formed when data was aligned to reach-end, and that these largest peaks nearly all began during the reach and ended precisely at the time the paw would have been about to grasp the food. The spread of neural activation onset times throughout the course of the complex reach-to-grasp movement is consistent with a relationship of individual neurons in the rat red nucleus with movements of all parts of the forelimb, as would be expected if all limb muscle groups are represented in the nucleus. On the other hand the disproportionate number of modulations that occur during the reach and their strong alignment with time of reach-end suggests there is a bias in red nucleus function towards the control of distal motions associated with accurate grasp, consistent with the result of recent lesion studies. This provides indirect evidence that functionally the rat red nucleus may be organized in a similar way to that of monkeys, in which an important role in control of accurate distal movements is well established. The possibility is discussed that red nucleus offers a timing signal for co-ordination of movements across joints, in particular the precise distal-proximal binding normally seen in accurate reach-to-grasp movements.

Action Potentials↗

PubMed2005

Ankle muscle activation during functional reach in hemiparetic and healthy subjects.

OBJECTIVE: To compare the differences of reaching ability and electromyography of ankle muscles between healthy and hemiparetic subjects. DESIGN: This is a cross-sectional control trial. A total of 31 subjects with hemiparesis and 31 age-matched healthy adults meeting our selection criteria participated in this study. Subjects performed forward reach and lateral reach, in random sequence, in a sitting position. The average reaching velocity, reaching distance, and onset time and mean muscle activity of bilateral tibialis anterior and soleus were recorded. RESULTS: Subjects with hemiparesis had slower movement velocity and less reaching distance than that of healthy subjects (P < 0.05). The distance for the lateral reach was shorter than that of the forward reach (P < 0.05). The high correlations between contralateral tibialis anterior and soleus were noted in forward (r = 0.66, P < 0.01) and lateral (r = 0.68, P < 0.01) reaching in healthy subjects, but such correlations were not established in subjects with hemiparesis. Except for the ipsilateral soleus, normalized electromyographic activities (percentage of maximal voluntary isometric contraction) during forward and lateral reach were higher for the hemiparetic subjects than that for the healthy subjects (P < 0.05). CONCLUSION: The functional reach abilities and the ankle electromyographic activity patterns in hemiparetic subjects were significantly different from those of healthy subjects. The muscles in the affected ankle cannot be recruited timely and efficiently for the reaching task, even with relative recovery.

Ankle↗

PubMed2005

Spatial tuning of reaching activity in the medial parieto-occipital cortex (area V6A) of macaque monkey.

We recorded neural activity from the medial parieto-occipital area V6A while three monkeys performed an instructed-delay reaching task in the dark. Targets to be reached were in different spatial positions. Neural discharges were recorded during reaching movements directed outward from the body (towards visual objects), during the holding phase (when the hand was on the target) and during inward movements of the hand towards the home button (which was near the body and outside the field of view). Reach-related activity was observed in the majority of 207 V6A cells, during outward (78%) and inward (65%) movements as well as during the holding phase (62%). Most V6A reaching neurons (84%) were modulated in more than one phase of the task. The reach-related activity in V6A could depend on somatosensory inputs and/or on corollary discharges from the dorsal premotor cortex. Although visual and oculomotor inputs are known to have a strong influence on V6A activity, we excluded the possibility that the reach-related activity which we observed was due to visual stimulation and/or oculomotor activity. Reach-related activity for movements towards different locations was spatially modulated during outward (40%) and inward (47%) reaching movements. The position of the hand/arm in space modulated about 40% of V6A cells. Preferred reach directions and spatial locations were represented uniformly across the workspace. These data suggest that V6A reach-related neurons are able to code the direction of movement of the arm and the position of the hand/arm in space. We suggest that the V6A reach-related neurons are involved in the guidance of goal-directed arm movements, whether these actions are visually guided or not.

Action Potentials↗

PubMedDate not supplied

Concerning the pectoralis major in active reaching exercise.

This study was designed to address an active reaching exercise on the purpose of determining the individual and interaction effects of reaching directions, assistance conditions and the muscles. The activity of the muscles, the Serratus Anterior and Pectoralis Major, in 20 healthy male subjects was recorded in parallel by surface electrode of electromyography. Four conditions of reaching, upward reaching in shoulder flexion 90(0) and sideward reaching in shoulder abduction 90(0) with and without arm support were tested. The results showed a significant decrease in the muscle activity in the sideward reaching when compared with the upward addition to with arm support when compared with without arm support. The Pectoralis Major was significantly less activated than the Serratus Anterior. There was a significant decrease in the Pectoralis Major and Serratus Anterior activation during sideward reaching when compared with the upward. Furthermore, Pectoralis Major and Serratus Anterior muscles during reaching with arm support were less activated than without the support. The interaction between reaching directions, assistance conditions and muscles revealed that the least activation for Pectoralis Major muscle was the sideward reaching with arm support whilst for Serratus Anterior was the sideward reaching with and without arm support. It is suggested that in clinical application, particularly in the spastic Pectoralis Major muscle patients, an active reaching exercise should be first done in the sideward direction with support.

Adolescent↗

PubMed1999

Modifications to the Standard Sit-and-Reach Flexibility Protocol.

OBJECTIVE: To present several modifications of the standard sit-and-reach protocol. BACKGROUND: Many exercises designed to increase strength and aerobic capacity tend to decrease the flexibility of the erector spinae and hamstrings musculature. Less-than-ideal flexibility in these soft tissues may increase the risk of injury during training, competition, or activities of daily living. The most widely used measures of flexibility have been either the stand-and-reach or the sit-and-reach, but both are limited to a single measure. DESCRIPTION: Using the new multitest flexometer, we were able to take 6 flexibility measures beyond the stand-and-reach test: standard active sit-and-reach, standard passive sit-and-reach, modified active sit-and-reach with external rotators slackened, modified passive sit-and-reach with external rotators slackened, modified active sit-and-reach with the hamstrings, gastrocnemii, and external rotators slackened, and modified passive sit-and-reach with the hamstrings, gastrocnemii, and external rotators slackened. CLINICAL ADVANTAGES: This modified sit-and-reach protocol allows the indirect assessment of the influence of the 4 major muscle groups that affect sit-and-reach scores: erector spinae, hip rotators, hamstrings, and gastrocnemii.

Journal Article↗

PubMed1997

Arm-movement-related neurons in the primate superior colliculus and underlying reticular formation: comparison of neuronal activity with EMGs of muscles of the shoulder, arm and trunk during reaching.

Neuronal activity was recorded from the superior colliculus (SC) and the underlying reticular formation in two monkeys during an arm reaching task. Of 744 neurons recorded, 389 (52%) clearly modulated their activity with arm movements. The temporal activity patterns of arm-movement-related neurons often had a time course similar to rectified electromyograms (EMGs) of particular muscles recorded from the shoulder, arm or trunk. These reach cells, as well as the muscles investigated, commonly exhibited mono- or biphasic (less frequently tri- or polyphasic) excitatory bursts of activity, which were related to the (pre-)movement period, the contact phase and/or the return movement. The vast majority of reach cells exhibited a consistent activity pattern from trial to trial as did most of the muscles of the shoulder, arm and trunk. Similarities between the activity patterns of the neurons and the muscles were sometimes very strong and were especially notable with the muscles of the shoulder girdle (e.g. trapezius descendens, supraspinatus, infraspinatus or the anterior and medial deltoids). This high degree of co-activation suggests a functional linkage, though not direct, between the collicular reach cells and these muscles. Neuronal activity onset was compared with that of 25 muscles of the arms, shoulders and trunk. The majority of cells (78.5%) started before movement onset with a mean lead time of 149+/-90 ms, and 36.5% were active even before the earliest EMG onset. The neurons exhibited the same high degree of correlation (r=0.97, Spearman rank) between activity onset and the beginning of the arm movement as did the muscles (r=0.98) involved in the task. The mean neuronal reach activity (background subtracted) ranged between 7 and 193 impulses/s (mean 40.5+/-24.2). The mean modulation index calculated [(reach activity background activity)/reach activity+background activity)] was 0.75+/-0.23 for neurons (n=358) and 0.87+/-0.14 for muscles (n=25). As the monkeys fixated the reach target constantly during an arm movement, neuronal activity which was modulated in this period was not related to eye movements. The three neck muscles investigated in the reach task exhibited no reach-related activity modulation comparable to that of either the reach cells or the muscles of the shoulder, arm and trunk. However, tonic neck muscle EMG was monotonically related to horizontal eye position. The clear skeletomotor discharge characteristics of arm-movement-related SC neurons revealed in this study agree with those already known from other sensorimotor regions (for example the primary motor, the premotor and parietal cortex, the basal ganglia or the cerebellum) and are consistent with the possible role of this population of reach cells in the control of arm movements.

Animals↗