Biomechanical Strategies Research Articles

Dynamics of body kinematics of freely flying houseflies responding to air turbulence

Abstract From the world's tiny flying bugs to gigantic dobsonflies, inflight locomotion of a flying creature requires complex biomechanical strategies to cope with air turbulence. These unpredictable changes in ambient airflow strength and direction may destabilize body posture and orientation. To record this behaviour in further detail, we scientifically examined how houseflies (Musca domestica) respond to air turbulence. We then, three-dimensionally reconstructed body and wings motion of continuously perturbated houseflies using high-speed videography under laboratory condition. The findings confirmed that houseflies, in general, do not initiate flight when average ambient air speed exceeds ~0.63 ms−1 at approximately ~2% of relative turbulent intensity. This finding contrasts with flies which immediately take-off after being released. During mild turbulent conditions, flies performed take-off but with severe and active modulation of body postures. In addition, the body roll angle fluctuates more severely (18.5-fold increase) compared to yaw (7-fold of increment) and pitch (6.4-fold of increment) during turbulence, highlighting that body roll stability is highly sensitive. This research extends our current knowledge on flies' behaviours during turbulence and how insects achieve their superior flight performance.

Reactive gait and postural adjustments following the first exposures to (un)expected stepdown

This study evaluated the reactive biomechanical strategies associated with both upper- and lower-body (lead and trail limbs) following the first exposures to (un)expected stepdown at comfortable (1.22 ± 0.08 m/s) and fast (1.71 ± 0.11 m/s) walking velocities. Eleven healthy adults completed 34 trails per walking velocity over an 8-m, custom-built track with two forceplates embedded in its center. For the expected stepdown, the track was lowered by 0-, −10- and −20-cm from the site of the second forceplate, whereas the unexpected stepdown was created by camouflaging the second forceplate (−10-cm). Two-way repeated-measurement ANOVAs detected no velocity-related effects of stepdown on kinematic and kinetic parameters during lead limb stance-phase, and on the trail limb stepping kinematics. However, analyses of significant interactions revealed greater peak flexion angles across the trunk and the trail limb joints (hip, knee and ankle) in unexpected versus expected stepdown conditions at a faster walking velocity. The −10-cm unexpected stepdown (main effect) had a greater influence on locomotor behavior compared to expected conditions due mainly to the absence of predictive adjustments, reflected by a significant decrease in peak knee flexion, contact time and vertical impulse during stance-phase. Walking faster (main effect) was associated with an increase in hip peak flexion and net anteroposterior impulse, and a decrease in contact time and vertical impulse during stepdown. The trail limb, in response, swung forward faster, generating a larger and faster recovery step. However, such reactive stepping following unexpected stepdown was yet a sparse compensation for an unstable body configuration, assessed by significantly smaller step width and anteroposterior margin-of-stability at foot-contact in the first-recovery-step compared with expected conditions. These findings depict the impact of the expectedness of stepdown onset on modulation of global dynamic postural control for a successful accommodation of (un)expected surface elevation changes in young, healthy adults.

Anaerobic capacity assessment in elite swimmers through inertial sensors

Objective: The present study aimed to assess if changes in speed and stroke parameters, as measured by an inertial sensor during a maximal effort swimming test, could provide an effective detection of anaerobic capacity in elite swimmers. Approach: Fourteen elite swimmers performed a 75 m maximal swimming test. Changes in speed and stroke parameters, estimated by a body-worn inertial sensor, were analysed to provide insight into stroke mechanics during swimming. Their relationships with the output of the Wingate Anaerobic Test were analysed. Best times in competition were also considered to assess swimmer’s performance. Main results: Mean power measured using the Wingate cycle ergometer test highly correlated with mean speed attained by the swimmers during the proposed 75 m swimming test (R range: .700–.809, p < .05). Mean power in the Wingate Anaerobic Test and mean speed in the 75 m swimming test highly correlated with best times attained by the swimmers (R range: .736–.855, p < .01; R range: .659–.952, p < .05, for Wingate and 75 m swimming test, respectively). Moreover, stroke variables were investigated: in this regard, a significant decrease in stroke rate and swimming speed and a significant increase in stroke length were observed between the first and the third lap (p < .01). Significance: The present in-water free swimming test provided insight into specific physiological/mechanical aspects of elite swimmers. The correlation of the swimming and the Wingate tests with swimmer’s performance in competition confirms that they both reflect the skills and anaerobic qualities a swimmer uses in a race. The wearable inertial sensor could represent a feasible solution to evaluate stroke parameters, allowing a timely follow-up of variations in swimming biomechanics along the course of the test and the identification of differences in biomechanical strategy between swimmers. This analysis is of great interest for swimmers and coaches to characterise swimmer’s technique weakness and strength, and to plan individual race pacing strategy.

Differences In Biomechanical And Electromyographic Strategies Between Young And Old Persons During The Timed Up-and-go

Differences In Biomechanical And Electromyographic Strategies Between Young And Old Persons During The Timed Up-and-go

Exploring Upper Quarter Y-Balance Test Biomechanical Strategies in Active College Students

Exploring Upper Quarter Y-Balance Test Biomechanical Strategies in Active College Students

ISSLS PRIZE IN BIOENGINEERING SCIENCE 2019: biomechanical changes in dynamic sagittal balance and lower limb compensatory strategies following realignment surgery in adult spinal deformity patients

Study designA longitudinal cohort study.ObjectiveTo define a set of objective biomechanical metrics that are representative of adult spinal deformity (ASD) post-surgical outcomes and that may forecast post-surgical mechanical complications.Summary of background dataCurrent outcomes for ASD surgical planning and post-surgical assessment are limited to static radiographic alignment and patient-reported questionnaires. Little is known about the compensatory biomechanical strategies for stabilizing sagittal balance during functional movements in ASD patients.MethodsWe collected in-clinic motion data from 15 ASD patients and 10 controls during an unassisted sit-to-stand (STS) functional maneuver. Joint motions were measured using noninvasive 3D depth mapping sensor technology. Mathematical methods were used to attain high-fidelity joint-position tracking for biomechanical modeling. This approach provided reliable measurements for biomechanical behaviors at the spine, hip, and knee. These included peak sagittal vertical axis (SVA) over the course of the STS, as well as forces and muscular moments at various joints. We compared changes in dynamic sagittal balance (DSB) metrics between pre- and post-surgery and then separately compared pre- and post-surgical data to controls.ResultsStandard radiographic and patient-reported outcomes significantly improved following realignment surgery. From the DSB biomechanical metrics, peak SVA and biomechanical loads and muscular forces on the lower lumbar spine significantly reduced following surgery (− 19 to − 30%, all p < 0.05). In addition, as SVA improved, hip moments decreased (− 28 to − 65%, all p < 0.05) and knee moments increased (+ 7 to + 28%, p < 0.05), indicating changes in lower limb compensatory strategies. After surgery, DSB data approached values from the controls, with some post-surgical metrics becoming statistically equivalent to controls.ConclusionsLongitudinal changes in DSB following successful multi-level spinal realignment indicate reduced forces on the lower lumbar spine along with altered lower limb dynamics matching that of controls. Inadequate improvement in DSB may indicate increased risk of post-surgical mechanical failure.Graphical abstractThese slides can be retrieved under Electronic Supplementary Material.

Biomechanics performance in 30-s chair stand test in patients with medial knee osteoarthritis

Knee osteoarthritis (OA) is characterised by weakness and knee joint pain which may affect the performance in some activities of daily life like sit-to-stand. The aim of this study is to evaluate the strategies used by patients with knee OA when performing the 30-second chair stand test (30s-CST), and its association with their well-being. Twenty-one patients with knee OA were recruited. A 3D motion analysis system and two force plates were used to capture the kinematics and kinetics during the 30s-CST. The sit-to-stand and the stand-to-sit phases of the test were analysed independently. Significant differences were found (p < 0.05) between the first three and the last three repetitions in the 30s-CST for knee joint moment and power. No significant differences have been found between the most painful knee and the contralateral knee. The correlations found between the subscales of the knee injury and osteoarthritis outcome score (KOOS) and biomechanical parameters were significant (p < 0.05). Patients with the best score in KOOS subscales also showed better performance in the 30s-CST. Assistive technologies that maximise biomechanical strategies could be a valuable contribution to improve the well-being of these patients.

True Orthodontic Intrusion Using Three-Piece Intrusion Arch for Correcting Excessive Gingival Exposure

The combination of proclined upper anteriors with high gingival exposure is challenging for the orthodontist. Correction of proclined upper anteriors sometimes leads to deepening of the bite and loss of posterior anchorage resulting in worsening of gingival exposure. Routinely correction of high gingival exposure was done prior to space closure resulting in increased treatment duration. However, application of sound biomechanical strategies can help us overcome these challenges without compromising treatment time. This presentation will describe the meticulous orthodontic biomechanics using a 3-piece intrusion arch to simultaneously correct excessive gingival exposure as well as accomplish space closure. The patient presented with Class I malocclusion with proclined upper anterior teeth, crowding in upper and lower arches and an excessive gingival exposure. Fixed orthodontic therapy was initiated with first premolar extractions and the primary strategies after correcting of the crowding was the effective use of a 3-piece intrusion arch for simultaneous intrusion and retraction of proclined anterior teeth. Biomechanics strategies utilizing the 3 piece intrusion arch effectively aided in closure of spaces, correction of high gingival exposure, intrusion of the upper anteriors and controlling posterior anchorage. All desired treatment outcomes were achieved without prolonging treatment time. Proper biomechanics strategies can effectively bring about true intrusion of the upper anteriors as well as correct the upper incisor proclination without prolonging treatment time. The use of threepiece intrusion arch to achieve orthodontic correction assures the attainment of predictable treatment results. Loss of anchorage is seldom observed because of the tip back moment on the posterior teeth. Another advantage of intrusion mechanics is the control of the vertical dimension.

Biomechanical Strategies Underlying the Robust Body Armour of an Aposematic Weevil.

Robust body armor is one of many anti-predator strategies used among animal taxa. The exoskeleton of insects can serve as the secondary defense mechanism in combination with the primary defense such as warning color. Aposematic Pachyrhynchus weevils advertise their unprofitability and use their robust exoskeleton for effective defense against lizard predators. While the mature weevils survive after the predatory attack, the soft teneral ones can easily be consumed. To reveal how the mature weevils achieve such effective protection, we investigated the ontogenetic changes in the microstructure and material properties of the exoskeleton of the adult weevils. We also tested the functional role of a weevil-specific structure, the fibrous ridge, in the robustness of the elytral cuticle of the mature weevils. The results showed that the mature weevils have thicker, stiffer and more sclerotized cuticle than the teneral ones. The fibrous ridges in the endocuticle considerably increase the overall stiffness of their cuticle. Together these biomechanical strategies enable Pachyrhynchus weevils to achieve robust body armor that efficiently protects them from lizard predation.

Features of the Support Function of the Feet in Children with Congenital Abnormalities and Acquired Deformities of the Mandibular Bones

Various types of dental disocclusion lead to disorders in the temporomandibular joint (TMJ) and subsequent abnormalities in the tone of the muscles of mastication. Prolonged dysfunction of the stomatognathic system leads to disorders in adaptation of the total musculoskeletal system, while the mechanism of this effect remains unclear. Plantographic characteristics of the feet were studied in nine children with stable deformities of the mandibular bones of a congenital or acquired genesis, and the distribution of plantar pressure was examined after reconstructive operations on the jaws and partial correction of occlusion. The plantographic characteristics were compared with those obtained in the same tests for 15 healthy children of the same age. Before surgery, the planthograms in tests with increasing load in the children with combined dentofacial and facial deformities differed in stiffness of all arches from the plantograms of the healthy children. Stiffness resulted in a significant increase in lateral support index, while the frontal and medial support indices were unchanged. After reconstructive surgery on the jaw(s) with restoration of the size, shape, and spatial position in the facial part of the skull, the support function of the external longitudinal arch of the foot recovered in the patients, but its recovery was accompanied by an increase in the rigidity of the transversal and internal longitudinal arches. Thus, the support function of the arches of the feet was disordered in children with stable deformity of the mandibular bones, and a change in biomechanical strategy was observed after reconstructive surgery.

The effects of mental practice based on motor imagery for mobility recovery after subacute stroke: Protocol for a randomized controlled trial

Background and purposeMental practice of motor imagery has shown beneficial effects in stroke recovery. However, there are few clinical trials investigating it on the subacute phase. This study will investigate the effects of mental practice in the mobility of patients with subacute stroke. Materials and methodsRandomized controlled trial including persons with subacute stroke (<3 months). All participants will receive physical exercises and will be randomly allocated into an experimental group (Mental Practice) or into a control group (cognitive training) for 4 weeks(12 sessions). ResultsPrimary outcomes will be assessed at baseline and after intervention and will be related to mobility, using Timed Up and Go test and 5 m walking speed test. Whereas secondary outcomes will be muscular strength, biomechanical strategies, mental health and quality of life. ConclusionThe beneficial effects that may be found in this trial can be greatly relevant in clinical practice, justifying this scientific question.

Does functional mobility vary among individuals with up to one year after stroke? An analysis using the TUG-ABS

The Timed “Up and Go” Assessment of Biomechanical Strategies (TUG-ABS) analyses functional mobility activities of Timed “Up and Go” (TUG) test, showing to be valid and reliable for individuals with stroke. The aim of this study was to evaluate if the performance of functional mobility activities varies between subjects within the first year poststroke. Thirty-eight stroke subjects (mean age 56.5 years) of both genders and with up to one year of first stroke that caused gait deficits (gait speed < 0.8 m/s) participated in the study. Participants were instructed to perform the following activities: standing up from a chair without armrests, walking and circling (180° turns) a cone placed at the 1.35-m mark, walking back and sitting down. The performances of these activities were registered by the Qualisys Motion Capture System. By analyzing the images, TUG-ABS was applied to evaluate: sit-to-stand (STSt), walking (W), turn (T) and stand-to-sit (STSi). For statistical analysis, participants were divided into: one group with up to 3 months poststroke ( n = 21), and another group with 4 to 12 months poststroke ( n = 17). Study groups were compared with Mann Whitney test for TUG-ABS activities and total TUG-ABS score (TS). The groups were homogeneous with regard to middle age, cognitive level (Mini-Mental State Examination), neurological status (National Institute of Health Stroke Scale) and walking ability (Functional Ambulatory Category). For TUG-ABS, there was also no difference between groups for the activities: STSt: P = 0.161; W: P = 0.383; T: P = 0.052; STSi: P = 0.542, and for TS: P = 0.144. Although motor recovery can be influenced by lesion time, the performance of functional mobility activities did not appear to be different among subjects in the first year poststroke. This suggests that biomechanical strategies for performing these activities are developed within the first three months following stroke, indicating the importance of early intervention for rehabilitation.

Simulated microgravity induces a cellular regression of the mature phenotype in human primary osteoblasts

Decreased mechanical loading on bones, such as prolonged bed rest and microgravity during space flights, leads to the development of an osteoporotic-like phenotype. Although osteoblast hypo-functionality is reported to be involved in the progression of bone pathological conditions, the cellular mechanisms of this process remain largely unknown. The combined application of mass spectrometry “–omics” and histochemical and ultrastructural approaches have been employed to investigate the effects of the gravitational unloading on human bone-cell biology. Here we show, ex vivo, that simulated microgravity (Sμg) on human primary osteoblasts (hpOB) induces an alteration of pro-osteogenic determinants (i.e., cell morphology and deposit of hydroxyapatite crystals), accompanied by a downregulation of adhesive proteins and bone differentiation markers (e.g., integrin beta-1, protein folding Crystallin Alpha B (CRYα-B), runt-related transcription factor 2 (RUNX-2), bone morphogenic protein-2 (BMP-2), and receptor activator of nuclear factor kappa-B ligand (RANK-L)), indicating an impairment of osteogenesis. Further, we observed for the first time that Sμg can trigger a transition toward a mesenchymal-like phenotype, in which a mature osteoblast displays an hampered vitamin A metabolism, loses adhesive molecules, gains mesenchymal components (e.g., pre-osteoblast state marker CD44), morphological protrusions (filopodium-like), enhances GTPase activities, which in turn allows it to acquire migrating properties. Although this phenotypic conversion is not complete and can be reversible, Sμg environment proves a plasticity potential hidden on Earth. Overall, our results suggest that Sμg can be a powerful physical cue for triggering ex vivo a dedifferentiation impulse on hpOBs, opening a new scenario of possible innovative therapeutical biomechanical strategies for the treatment of osteo-degenerative diseases.

Change-of-Direction Biomechanics: Is What's Best for Anterior Cruciate Ligament Injury Prevention Also Best for Performance?

Change-of-direction maneuvers (e.g., side-step cutting) are an important aspect of performance in multi-directional sports, but these maneuvers are also associated with anterior cruciate ligament (ACL) injury. Despite this, the impact of biomechanics on ACL injury risk and performance is often examined in isolation. The purpose of this review was to examine the alignment between biomechanical recommendations for ACL injury prevention and performance with regard to change-of-direction maneuvers. Several studies linking change-of-direction biomechanics to both ACL injury risk and performance were examined. A degree of overlap was identified between biomechanical strategies that could both reduce ACL injury risk and enhance performance during change-of-direction maneuvers. A fore-foot footfall pattern along with trunk rotation and lateral flexion in the intended cutting direction were identified as biomechanical strategies that could both reduce potentially hazardous knee joint moments and enhance change-of-direction speed. Minimizing knee valgus during change-of-direction maneuvers may also reduce ACL injury risk, with this biomechanical strategy found to have no impact on performance. Certain biomechanical strategies proposed to reduce ACL injury risk were linked to reduced change-of-direction performance. A narrow foot placement and "soft" landings with greater knee flexion were identified as ACL injury prevention strategies that could have a negative impact on performance. The findings of this review emphasize the need to consider both ACL injury risk and performance when examining the biomechanics of change-of-direction maneuvers.

Establishing the relationship between loading parameters and bone adaptation

Cyclic and low-magnitude loading is considered effective in arresting the bone loss as it promotes osteogenesis (i.e. new bone formation) at the sites of elevated normal strain magnitude. In silico models assumed normal strain as the stimulus to predict the sites of new bone formation. These models, however, may fail to fit the amount of newly formed bone. Loading parameters such as strain, frequency, and loading cycle decide the amount of new bone formation. The models did not incorporate this information. In fact, there is no unifying relationship to quantify the amount of new bone formation as a function of loading parameters. Therefore, the present work aims to establish an empirical relationship between loading parameters and a new bone formation parameter i.e. mineral apposition rate (MAR). A neural network model is used to serve the purpose. Loading parameters are supplied as input, whereas, MAR served as output. The model is trained and tested with experimental data. The model establishes an empirical relationship to estimate MAR as a function of loading parameters. The model's predictions of MAR align with in vivo experimental results. The model's response is analyzed which indicates that the bone adaptation characteristics are successfully captured in the relationship. The relationship established may be incorporated further to improve qualitative and quantitative prediction capabilities of computer models. These findings can be extended in future to design and develop effective biomechanical strategies such as prophylactic exercise to cure bone loss.

An occupational perspective in hand therapy: A scoping review

Introduction There have been calls for the occupational therapy profession to realign with its values around occupation. However, the profession faces challenges in practice areas that have historically been underpinned by a biomechanical approach, such as hand therapy. The aim of this scoping review was to describe what is known about an occupational perspective in the hand therapy literature. Method This scoping review utilised a recognised five-step approach. A search was conducted in four databases for papers published between 2005 and 2016. Numerical and thematic analyses were employed, using the Canadian Practice Process Framework as a theoretical framework. Results Fifty papers were included in the scoping review. Six themes were identified: the centrality of occupation; inconsistencies in terminology; where in the occupational therapy process?; informal discussion as a key occupational strategy; occupational therapists’ expectations of patients; and a bottom-up approach focusing on biomechanical strategies to implementing the plan. Conclusion Whilst there has been some integration of an occupational perspective into hand therapy literature, there are still challenges. Inconsistent terminology, the lack of an occupational perspective throughout the occupational therapy process and a bottom-up approach to interventions all demonstrate the continuing tensions between the biomechanical approach and an occupational perspective.

Relationships of hamstring muscle volumes to lateral tibial slope

BackgroundGreater posterior–inferior directed slope of the lateral tibial plateau (LTS) has been demonstrated to be a prospective ACL injury risk factor. Trainable measures to overcome a greater LTS need to be identified for optimizing injury prevention protocols.It was hypothesized that Healthy individuals with greater LTS who have not sustained an ACL injury would have a larger lateral hamstring volume. MethodsEleven healthy females (mean +/- standard deviation) (1.63±0.07m, 62.0±8.9kg, 22.6±2.9years) & 10 healthy males (1.80±0.08m, 82.3±12.0kg, 23.2±3.4years) underwent magnetic resonance imaging of the left knee and thigh. LTS, semitendinosus muscle volume, and biceps femoris long head muscle volume were obtained from imaging data. ResultsAfter controlling for potential sex confounds (R2=.00; P=.862), lesser semitendinosus volume and greater biceps femoris-long head volume were indicative of greater LTS (R2∆=.30, P=.008). ConclusionsHealthy individuals with greater LTS have a muscular morphologic profile that includes a larger biceps femoris-long head volume. This may be indicative of a biomechanical strategy that relies more heavily on force generation of the lateral hamstring and is less reliant on force generation of the medial hamstring. Level of evidenceLevel IV.

Warm-up for Sprint Swimming: Race-Pace or Aerobic Stimulation? A Randomized Study.

Neiva, HP, Marques, MC, Barbosa, TM, Izquierdo, M, Viana, JL, Teixeira, AM, and Marinho, DA. Warm-up for sprint swimming: race-pace or aerobic stimulation? A randomized study. J Strength Cond Res 31(9): 2423-2431, 2017-The aim of this study was to compare the effects of 2 different warm-up intensities on 100-m swimming performance in a randomized controlled trial. Thirteen competitive swimmers performed two 100-m freestyle time-trials on separate days after either control or experimental warm-up in a randomized design. The control warm-up included a typical race-pace set (4 × 25 m), whereas the experimental warm-up included an aerobic set (8 × 50 m at 98-102% of critical velocity). Cortisol, testosterone, blood lactate ([La]), oxygen uptake (V[Combining Dot Above]O2), heart rate, core (Tcore and Tcorenet) and tympanic temperatures, and rating of perceived exertion (RPE) were monitored. Stroke length (SL), stroke frequency (SF), stroke index (SI), and propelling efficiency (ηp) were assessed for each 50-m lap. We found that V[Combining Dot Above]O2, heart rate, and Tcorenet were higher after experimental warm-up (d > 0.73), but only the positive effect for Tcorenet was maintained until the trial. Performance was not different between conditions (d = 0.07). Experimental warm-up was found to slow SF (mean change ±90% CL = 2.06 ± 1.48%) and increase SL (1.65 ± 1.40%) and ηp (1.87 ± 1.33%) in the first lap. After the time-trials, this warm-up had a positive effect on Tcorenet (d = 0.69) and a negative effect on [La] (d = 0.56). Although the warm-ups had similar outcomes in the 100-m freestyle, performance was achieved through different biomechanical strategies. Stroke length and efficiency were higher in the first lap after the experimental warm-up, whereas SF was higher after control warm-up. Physiological adaptations were observed mainly through an increased Tcore after experimental warm-up. In this condition, the lower [La] after the trial suggests lower dependency on anaerobic metabolism.

Three dimensional motion capture applied to violin playing: A study on feasibility and characterization of the motor strategy

Background and ObjectivePlaying string instruments requires advanced motor skills and a long training that is often spent in uncomfortable postures that may lead to injuries or musculoskeletal disorders. Thus, it is interesting to objectively characterize the motor strategy adopted by the players. In this work, we implemented a method for the quantitative analysis of the motor performance of a violin player. MethodsThe proposed protocol takes advantage of an optoelectronic system and some infra-red reflecting markers in order to track player's motion. The method was tested on a professional violin player performing a legato bowing task. The biomechanical strategy of the upper limb and bow positioning were described by means of quantitative parameters and motion profiles. Measured quantities were: bow trajectory, angles, tracks, velocity, acceleration and jerk. ResultsA good repeatability of the bowing motion (CV < 2%) and high smoothness (jerk < 5 m/s3) were observed. Motion profiles of shoulder, elbow and wrist were repeatable (CV < 7%) and comparable to the curves observed in other studies. Jerk and acceleration profiles demonstrated high smoothness in the ascending and descending phases of bowing. High variability was instead observed for the neck angle (CV ∼56%). Conclusions“Quantitative” measurements, instead of “qualitative” observation, can support the diagnosis of motor disorders and the accurate evaluation of musicians’ skills. The proposed protocol is a powerful tool for the description of musician's performance, that may be useful to document improvements in playing abilities and to adjust training strategies.

Data sample size needed for analysis of kinematic and muscle synergies in healthy and stroke populations.

Multiple studies have suggested the central nervous system (CNS) generates motions by using modular control of muscles and joints (synergies). However, the synergies reported by these studies are task dependent and might not reflect the true control strategies adopted by the CNS. Studying exploratory motions (EMs) can reveal biomechanical constraints and motor control strategies in healthy and clinical populations. The first logical step to consider EMs in study of motor synergies is to determine how much data is required to reliably and fully profile the motion patterns of an individual. Here we present how the quality of motor synergies analysis depends on the amount of EM data included in the analysis. We recruited 10 healthy and 10 post-stroke participants and collected electromyography (EMG) and joint motion data of their arms as they completed a motor exploration task. We compared the effects of clinical status and limb strength/dominance on the amount of data required to identify synergies. Clinical status had a significant elïect on the required amount of data for both datasets. Limb strength had a significant effect only for kinematic data. We determined the upper bound 95% confidence interval to set the amount of data required for synergy analysis in both populations: 235 sec for EMG data and 265 sec for kinematic data. Our results provide an important step toward using motor exploration in the study of healthy motor synergies and how stroke alters them.