2024 AHA/ASA Performance and Quality Measures for Spontaneous Intracerebral Hemorrhage: A Report From the American Heart Association/American Stroke Association.

The American Heart Association/American Stroke Association released a revised spontaneous intracerebral hemorrhage guideline in 2022. A working group of stroke experts reviewed this guideline and identified a subset of recommendations that were deemed suitable for creating performance measures. These 15 performance measures encompass a wide spectrum of intracerebral hemorrhage patient care, from prehospital to posthospital settings, highlighting the importance of timely interventions. The measures also include 5 quality measures and address potential challenges in data collection, with the aim of future improvements.

Measuring the Implementation Preferences of Emergency Medical Services Clinicians Using Discrete Choice Experiments.

INTRODUCTION: Prehospital research and evidence-based guidelines (EBGs) have grown in recent decades, yet there is still a paucity of prehospital implementation research. While recent studies have revealed EMS agency leadership perspectives on implementation, the important perspectives and opinions of frontline EMS clinicians regarding implementation have yet to be explored in a systematic approach. The objective of this study was to measure the preferences of EMS clinicians for the process of EBG implementation and whether current agency practices align with those preferences. METHODS: This study was a cross-sectional survey of National Registry of Emergency Medical Technicians registrants. Eligible participants were certified paramedics who were actively practicing EMS clinicians. The survey contained discrete choice experiments (DCEs) for three EBG implementation scenarios and questions about rank order preferences for various aspects of the implementation process. For the DCEs, we used multinomial logistic regression to analyze the implementation preference choices of EMS clinicians, and latent class analysis to classify respondents into groups by their preferences. RESULTS: A total of 183 respondents completed the survey. Respondents had a median age of 39 years, were 74.9% male, 89.6% White, and 93.4% of non-Hispanic ethnicity. For all three DCE scenarios, respondents were significantly more likely to choose options with hospital feedback and individual-level feedback from EMS agencies. Respondents were significantly less likely to choose options with email/online only education, no feedback from hospitals, and no EMS agency feedback to clinicians. In general, respondents' preferences favored classroom-based training over in-person simulation. For all DCE questions, most respondents (66.2%-77.1%) preferred their survey DCE choice to their agency's current implementation practices. In the rank order preferences, most participants selected "knowledge of the underlying evidence behind the change" as the most important component of the process of implementation. CONCLUSIONS: In this study of EMS clinicians' implementation preferences using DCEs, respondents preferred in-person education, feedback on hospital outcomes, and feedback on their individual performance. However, current practice at EMS agencies rarely matched those expressed EMS clinician preferences. Collectively, these results present opportunities for improving EMS implementation from the EMS clinician perspective.

Prehospital Stroke Care Part 1: Emergency Medical Services and the Stroke Systems of Care.

Acute stroke care begins before hospital arrival, and several prehospital factors are critical in influencing overall patient care and poststroke outcomes. This topical review provides an overview of the state of the science on prehospital components of stroke systems of care and how emergency medical services systems may interact in the system to support acute stroke care. Topics include layperson recognition of stroke, prehospital transport strategies, networked stroke care, systems for data integration and real-time feedback, and inequities that exist within and among systems.

Prehospital Stroke Care Part 2: On-Scene Evaluation and Management by Emergency Medical Services Practitioners.

The prehospital phase is a critical component of delivering high-quality acute stroke care. This topical review discusses the current state of prehospital acute stroke screening and transport, as well as new and emerging advances in prehospital diagnosis and treatment of acute stroke. Topics include prehospital stroke screening, stroke severity screening, emerging technologies to aid in the identification and diagnosis of acute stroke in the prehospital setting, prenotification of receiving emergency departments, decision support for destination determination, and the capabilities and opportunities for prehospital stroke treatment in mobile stroke units. Further evidence-based guideline development and implementation of new technologies are critical for ongoing improvements in prehospital stroke care.

Locomotor, ecological and phylogenetic drivers of skeletal proportions in frogs.

Frogs exhibit complex anatomical features of the pelvis, limbs and spine, long assumed to represent specialisations for jumping. Yet frogs employ a wide range of locomotor modes, with several taxa featuring primary locomotor modes other than jumping. Using a combination of techniques (CT imaging and 3D visualization, morphometrics, phylogenetic mapping), this study aims to determine the link between skeletal anatomy and locomotor style, habitat type and phylogenetic history, shedding new light on how functional demands impact morphology. Body and limb measurements for 164 taxa from all the recognised anuran families are extracted from digitally segmented CT scans of whole frog skeletons and analysed using various statistical techniques. We find that the expansion of the sacral diapophyses is the most important variable for predicting locomotor mode, which was more closely correlated with frog morphology than either habitat type or phylogenetic relationships. Predictive analyses suggest that skeletal morphology is a useful indicator of jumping but less so for other locomotor modes, suggesting that there is a wide range of anatomical solutions to performing locomotor styles such as swimming, burrowing or walking.

2022 Systematic Review of Evidence-Based Guidelines for Prehospital Care.

INTRODUCTION: Multiple national organizations and federal agencies have promoted the development, implementation, and evaluation of evidence-based guidelines (EBGs) for prehospital care. Previous efforts have identified opportunities to improve the quality of prehospital guidelines and highlighted the value of high-quality EBGs to inform initial certification and continued competency activities for EMS personnel. OBJECTIVES: We aimed to perform a systematic review of prehospital guidelines published from January 2018 to April 2021, evaluate guideline quality, and identify top-scoring guidelines to facilitate dissemination and educational activities for EMS personnel. METHODS: We searched the literature in Ovid Medline and EMBASE from January 2018 to April 2021, excluding guidelines identified in a prior systematic review. Publications were retained if they were relevant to prehospital care, based on organized reviews of the literature, and focused on providing recommendations for clinical care or operations. Included guidelines were appraised to identify if they met the National Academy of Medicine (NAM) criteria for high-quality guidelines and scored across the six domains of the Appraisal of Guidelines for Research and Evaluation (AGREE) II tool. RESULTS: We identified 75 guidelines addressing a variety of clinical and operational aspects of EMS medicine. About half (n = 39, 52%) addressed time/life-critical conditions and 33 (44%) contained recommendations relevant to non-clinical/operational topics. Fewer than half (n = 35, 47%) were based on systematic reviews of the literature. Nearly one-third (n = 24, 32%) met all NAM criteria for clinical practice guidelines. Only 27 (38%) guidelines scored an average of >75% across AGREE II domains, with content relevant to guideline implementation most commonly missing. CONCLUSIONS: This interval systematic review of prehospital EBGs identified many new guidelines relevant to prehospital care; more than all guidelines reported in a prior systematic review. Our review reveals important gaps in the quality of guideline development and the content in their publications, evidenced by the low proportion of guidelines meeting NAM criteria and the scores across AGREE II domains. Efforts to increase guideline dissemination, implementation, and related education may be best focused around the highest quality guidelines identified in this review.

Recommendations for Improving the Quality of Prehospital Evidence-Based Guidelines.

Evidence-based guidelines that provide recommendations for clinical care or operations are increasingly being published to inform the EMS community. The quality of evidence evaluation and methodological rigor undertaken to develop and publish these recommendations vary. This can negatively affect dissemination, education, and implementation efforts. Guideline developers and end users could be better informed by efforts across medical specialties to improve the quality of guidelines, including the use of specific criteria that have been identified within the highest quality guidelines. In this special contribution, we aim to describe the current state of published guidelines available to the EMS community informed by two recent systematic reviews of existing prehospital evidenced based guidelines (EBGs). We further aim to provide a description of key elements of EBGs, methods that can be used to assess their quality, and concrete recommendations for guideline developers to improve the quality of evidence evaluation, guideline development, and reporting. Finally, we outline six key recommendations for improving prehospital EBGs, informed by systematic reviews of prehospital guidelines performed by the Prehospital Guidelines Consortium.

Emergency Medical Services Leadership Perspectives on Implementation of Evidence-Based Guidelines: A Qualitative Study.

Introduction: Prehospital evidence-based guidelines (EBGs) are developed to optimize clinical outcomes for emergency medical services (EMS) patients. However, widespread implementation of EBGs is often inconsistent. Therefore, this study aimed to assess the baseline knowledge and practices of EMS leaders related to EBG implementation.Methods: This was a qualitative study using focus groups to assess prehospital implementation awareness and knowledge. Participants were EMS EBG authors, EMS medical directors, and EMS professional organization leaders. Focus groups were held via video conference, audio recorded, and transcribed. Thematic coding used domains and constructs of the Consolidated Framework for Implementation Research (CFIR).Results: Six focus groups were conducted with a total of 18 participants. A total of 1,044 codes were analyzed. "Process" was the CFIR domain with the most codes (n = 350, 33.5%), followed by the "inner setting" (the EMS agency; n = 250, 23.9%), "characteristics of the intervention" (n = 203, 19.4%), "outer setting" (the health care system and community the EMS agency serves, and the broader national EMS professional context; n = 141, 13.5%), and "characteristics of individuals" (n = 100, 9.6%). The ten most frequent constructs across all domains were: reflecting and evaluating, executing, cosmopolitanism, planning, external policy and incentives, design quality and packaging, learning climate, culture, complexity, and other personal attributes.Conclusion: EMS leadership and stakeholder views on EBG implementation identified dominant themes related to the process of implementation and the culture and learning/implementation climate of EMS agencies. Opinions were mixed on the utility of the CFIR as a potential guide for EMS implementation. Further work is required to gain the frontline EMS clinician perspective on implementation and tie key themes to quantitative prehospital implementation outcomes.

Outcomes of Patients Receiving Thrombolysis in a Mobile Stroke Unit: A 4-Year Retrospective, Observational, Single-Center Study.

BACKGROUND AND PURPOSE: Patients with acute ischemic stroke (AIS) eligible for thrombolysis benefit when thrombolysis is administered quickly, and mobile stroke units (MSU) can facilitate timely thrombolysis. We sought to compare time metrics and clinical outcomes of AIS patients receiving thrombolysis in an MSU compared with patients arriving via local emergency medical services (EMS). METHODS: We performed a retrospective, non-randomized, cohort study comparing MSU-arriving to EMS-arriving AIS patients from January 20, 2017 through November 30, 2020. The primary outcome was rate of return to baseline functional status as measured by the modified Rankin Score (mRS) 90 days after thrombolysis. Secondary outcomes included evaluation and treatment intervals from last known well, treatment rate in the first hour of symptoms, hospital length of stay, and mortality. Chi square and Student's t-test were used to compare groups. RESULTS: Of 1752 total patients with prehospital suspected stroke, 975 (55.7%) were transported via MSU, of whom 431 (44.2%) were diagnosed with stroke, including 368 (85.4%) with AIS, and 69 AIS patients (18.8%) received thrombolysis. Of 777 (44.3%) EMS-arriving patients, 373 (48%) were diagnosed with stroke, including 305 (81.8%) with AIS, and 74 (24.3%) received thrombolysis. Though not statistically significant, point estimates of the proportion of AIS patients treated with thrombolysis returning to baseline functional status were more commonly observed for MSU than for EMS transports when the baseline mRS was 0-2 (45.8% vs 33.3%), 0-3 (41.9% vs 33.3%), and 4-5 (71.4% vs 20.0%). MSU patients were more likely to receive thrombolysis in the first 60 minutes of symptom onset (31.9% vs 12.2%, p = 0.006). Overall mortality rates regardless of baseline mRS were similar between groups. CONCLUSIONS: AIS patients received thrombolysis faster in the MSU compared with EMS and more frequently within 60 minutes of stroke onset. Point estimates for 90-day clinical outcomes of AIS patients treated with thrombolysis favored MSU without a statistically significant difference.

Emergency Medical Service Time Intervals for Patients With Suspected Stroke in the United States.

BACKGROUND: Optimal care for patients with stroke relies on timely recognition and rapid transport to appropriate treatment, often by emergency medical services (EMS). Our primary objective was to describe EMS time intervals for patients with suspected stroke in the United States. We also sought to quantify the variation in EMS time intervals by geographic location and urbanicity. METHODS: We conducted a cross-sectional evaluation of EMS 9-1-1 activations (ie, calls for service) included in the 2018 and 2019 National EMS Information System datasets. We included ground or air EMS activations for a 9-1-1 scene response where a patient aged ≥18 years with suspected stroke was treated and transported by EMS. Time intervals for dispatch, response, scene, transport, and total prehospital time (ie, from dispatch to hospital arrival) were calculated, stratified by ground and air transport type. RESULTS: A total of 410 187 activations for suspected stroke were included, of which 98% were a ground transport. The median total prehospital time for ground transports was 35 minutes (interquartile range, 27-45, 90th percentile 58). Median total prehospital time for air transports was substantially longer at 56 minutes (interquartile range, 43-70, 90th percentile 86). Times varied by Census division and urbanicity with the shortest ground total prehospital times in the East North Central division and urban areas and longest times in the East South Central and rural and frontier areas. CONCLUSIONS: Timely EMS response and transport is critical for optimizing care of patients with suspected stroke. Using a large, national dataset of EMS activations, we found variations by geographic location and urbanicity in total prehospital time for ground and air EMS activations for patients with stroke.

In vivo and ex vivo range of motion in the fire salamander Salamandra salamandra.

Joint range of motion (RoM) analyses are fundamental to our understanding of how an animal moves throughout its ecosystem. Recent technological advances allow for more detailed quantification of this RoM (e.g. including interaction of degrees of freedom) both in ex vivo joints and in vivo experiments. Both types of data have been used to draw comparisons with fossils to reconstruct locomotion. Salamanders are often used as analogues for early tetrapod locomotion; testing such hypotheses requires an in-depth analysis of salamander joint RoM. Here, we provide a detailed dataset of the ex vivo ligamentous rotational joint RoM in the hindlimb of the fire salamander Salamandra salamandra, using a new method for collecting and visualising joint RoM. We also characterise in vivo joint RoM used during walking, via scientific rotoscoping and compare the in vivo and ex vivo data. In summary, we provide (1) a new method for joint RoM data experiments and (2) a detailed analysis of both in vivo and ex vivo data of salamander hindlimbs, which can be used for comparative studies.

Spherical frame projections for visualising joint range of motion, and a complementary method to capture mobility data.

Quantifying joint range of motion (RoM), the reachable poses at a joint, has many applications in research and clinical care. Joint RoM measurements can be used to investigate the link between form and function in extant and extinct animals, to diagnose musculoskeletal disorders and injuries or monitor rehabilitation progress. However, it is difficult to visually demonstrate how the rotations of the joint axes interact to produce joint positions. Here, we introduce the spherical frame projection (SFP), which is a novel 3D visualisation technique, paired with a complementary data collection approach. SFP visualisations are intuitive to interpret in relation to the joint anatomy because they 'trace' the motion of the coordinate system of the distal bone at a joint relative to the proximal bone. Furthermore, SFP visualisations incorporate the interactions of degrees of freedom, which is imperative to capture the full joint RoM. For the collection of such joint RoM data, we designed a rig using conventional motion capture systems, including live audio-visual feedback on torques and sampled poses. Thus, we propose that our visualisation and data collection approach can be adapted for wide use in the study of joint function.

Priorities for Prehospital Evidence-Based Guideline Development: A Modified Delphi Analysis.

Objective: Few areas of prehospital care are supported by evidence-based guidelines (EBGs). We aimed to identify gaps in clinical and operational prehospital EBGs to prioritize future EBG development and research funding. Methods: Using modified Delphi methodology, we sought consensus among experts in prehospital care and EBG development. Five rounds of surveys were administered between October 2019 and February 2020. Round 1 asked participants to list the top three gaps in prehospital clinical guidelines and top three gaps in operational guidelines that should be prioritized for guideline development and research funding. Based on responses, 3 reviewers performed thematic analysis to develop a list of prehospital EBG gaps, with participant feedback in Round 2. In Round 3, participants rated each gap's importance using a 5-point Likert scale, and participants' responses were averaged. In Round 4, participants rank-ordered 10 gaps with the highest mean scores identified in Round 3. In Round 5, participants indicated their agreement with sets of the highest ranked gaps. Results: Of 23 invited participants, 14 completed all 5 rounds. In Rounds 1 and 2, participants submitted 65 clinical and 58 operational gaps, and thematic analysis identified 23 unique clinical gaps and 28 unique operational gaps. The final prioritized list of clinical EBG gaps was: 1) airway management in adult and pediatric patients, 2) care of the pediatric patient, and 3) management of prehospital behavioral health emergencies, with 79% of participants agreeing. The final prioritized list of operational EBG gaps was: 1) define and measure the impact of EMS care on patient outcomes, 2) practitioner wellness, and 3) practitioner safety in the out-of-hospital environment, with 86% of participants agreeing. Conclusions: This modified Delphi study identifies gaps in prehospital EBGs that, if prioritized for development and research funding, would be expected to have the greatest impact on prehospital clinical care and operations.

Improving Prehospital Stroke Diagnosis Using Natural Language Processing of Paramedic Reports.

Background and Purpose: Accurate prehospital diagnosis of stroke by emergency medical services (EMS) can increase treatments rates, mitigate disability, and reduce stroke deaths. We aimed to develop a model that utilizes natural language processing of EMS reports and machine learning to improve prehospital stroke identification. Methods: We conducted a retrospective study of patients transported by the Chicago EMS to 17 regional primary and comprehensive stroke centers. Patients who were suspected of stroke by the EMS or had hospital-diagnosed stroke were included in our cohort. Text within EMS reports were converted to unigram features, which were given as input to a support-vector machine classifier that was trained on 70% of the cohort and tested on the remaining 30%. Outcomes included final diagnosis of stroke versus nonstroke, large vessel occlusion, severe stroke (National Institutes of Health Stroke Scale score >5), and comprehensive stroke center-eligible stroke (large vessel occlusion or hemorrhagic stroke). Results: Of 965 patients, 580 (60%) had confirmed acute stroke. In a test set of 289 patients, the text-based model predicted stroke nominally better than models based on the Cincinnati Prehospital Stroke Scale (c-statistic: 0.73 versus 0.67, P=0.165) and was superior to the 3-Item Stroke Scale (c-statistic: 0.73 versus 0.53, P<0.001) scores. Improvements in discrimination were also observed for the other outcomes. Conclusions: We derived a model that utilizes clinical text from paramedic reports to identify stroke. Our results require validation but have the potential of improving prehospital routing protocols.

Door-In-Door-Out Process Times at Primary Stroke Centers in Chicago.

STUDY OBJECTIVE: Acute stroke patients often require interfacility transfer from primary stroke centers to comprehensive stroke centers. Given the time-sensitive benefits of endovascular reperfusion, reducing door-in-door-out time at the primary stroke center is a target for quality improvement. We sought to identify modifiable predictors of door-in-door-out times at 3 Chicago-region primary stroke centers. METHODS: We performed a retrospective analysis of consecutive patients with acute stroke from February 1, 2018 to January 31, 2020 who required transfer from 1 of 3 primary stroke centers to 1 of 3 affiliated comprehensive stroke centers in the Chicago region. Stroke coordinators at each primary stroke center abstracted data on type of transport, medical interventions and treatments prior to transfer, and relevant time intervals from patient arrival to departure. We evaluated predictors of door-in-door-out time using median regression models. RESULTS: Of 191 total patients, 67.9% arrived by emergency medical services and 57.4% during off-hours. Telestroke was performed in 84.2%, 30.5% received alteplase, and 48.4% underwent a computed tomography (CT) angiography at the primary stroke center. The median door-in-door-out time was 148.5 (interquartile range 106 to 207.8) minutes. The largest contributors to door-in-door-out time, in minutes, were CT to CT angiography time (22 [7 to 73.5]), transfer center contact to ambulance request time (20 [8 to 53.3]), ambulance request to arrival time (20.5 [14 to 36]), and transfer ambulance time at primary stroke center (26 [21 to 35]). Factors associated with door-in-door-out time were (adjusted median differences, in minutes [95% confidence intervals]): CT angiography performed at primary stroke center (+39 [12.3 to 65.7]), walk-in arrival mode (+53 [4.1 to 101.9]), administration of intravenous alteplase (-29 [-31.3 to -26.7]), intubation at primary stroke center (+23 [7.3 to 38.7]), and ambulance request by primary stroke center (-20 [-34.3 to -5.7]). CONCLUSION: Door-in-door-out times at Chicago-area primary stroke centers average nearly 150 minutes. Reducing time to CT angiography, receipt of alteplase, and ambulance request are likely important modifiable targets for interventions to decrease door-in-door-out times at primary stroke centers.

In vitro virtual reality: an anatomically explicit musculoskeletal simulation powered by in vitro muscle using closed-loop tissue-software interaction.

Muscle force-length dynamics are governed by intrinsic contractile properties, motor stimulation and mechanical load. Although intrinsic properties are well characterised, physiologists lack in vitro instrumentation to account for combined effects of limb inertia, musculoskeletal architecture and contractile dynamics. We introduce in vitro virtual reality (in vitro-VR) which enables in vitro muscle tissue to drive a musculoskeletal jumping simulation. In hardware, muscle force from a frog plantaris was transmitted to a software model where joint torques, inertia and ground reaction forces were computed to advance the simulation at 1 kHz. To close the loop, simulated muscle strain was returned to update in vitro length. We manipulated (1) stimulation timing and (2) the virtual muscle's anatomical origin. This influenced interactions among muscular, inertial, gravitational and contact forces dictating limb kinematics and jump performance. We propose that in vitro-VR can be used to illustrate how neuromuscular control and musculoskeletal anatomy influence muscle dynamics and biomechanical performance.

Race, Socioeconomic Status, and Gastrostomy after Spontaneous Intracerebral Hemorrhage.

INTRODUCTION: Spontaneous intracerebral hemorrhage is a disabling form of stroke, and some patients will require nutritional interventions for dysphagia. We sought to determine if socioeconomic status indicators mediate whether minorities undergo gastrostomy tube placement. MATERIALS AND METHODS: Patients with spontaneous intracerebral hemorrhage were enrolled in a single center, observational cohort study from 2010 to 2017. A socioeconomic index score was imputed using neighborhood characteristics by patients' ZIP code, according to an established method utilizing 6 indicators of wealth/income, education, and occupation. Multivariable logistic regression models were generated and stratified by racial/ethnic groups to determine the association of socioeconomic status with gastrostomy tube placement. RESULTS: Among 512 patients, 93 (18.2%) underwent gastrostomy tube placement. There were 245 Whites, 220 Blacks, and 47 Hispanic. Blacks underwent the highest percentage of gastrostomy placement (22.7%), and Whites had the lowest percentage (13.5%). Among patients with gastrostomy, Blacks and Hispanics had lowest median socioeconomic index (-2.1 [IQR: -3.0, .7]; .7 [IQR: -1.6, 2.9], respectively, P < .001). Increasing intracerebral hemorrhage score was correlated with higher odds of gastrostomy across all groups (P values ≤ .01) but only Hispanics had reduced adjusted odds of gastrostomy with increasing socioeconomic index (OR .56; 95% .33-.84; P = .01). DISCUSSION: Racial/ethnic minorities had lower socioeconomic index and underwent more gastrostomy placement. Socioeconomic index was independently associated with gastrostomy only in Hispanics, in whom the odds of gastrostomy decreased with increasing socioeconomic index. Summary & Conclusion: Differences in utilization of gastrostomy were evident among minorities, and socioeconomic status may mediate this relationship among Hispanics.

Early Stroke Recognition and Time-based Emergency Care Performance Metrics for Intracerebral Hemorrhage.

BACKGROUND AND AIM: Performance measures have been extensively studied for acute ischemic stroke, leading to guideline-established benchmarks. Factors influencing care efficiency for intracerebral hemorrhage (ICH) are not well delineated. We sought to identify factors associated with early recognition of ICH and to assess the association between early recognition and completion of emergency care tasks. METHODS: Consecutive patients with spontaneous ICH were enrolled in an observational cohort study conducted from 2009 to 2017 at an urban comprehensive stroke center, excluding patient transferred from other hospitals. We used stroke team activation as the indicator of early recognition and measured completion times for multiple ICH-relevant performance metrics including door to computed tomography (CT) acquisition and door to hemostatic medication initiation. RESULTS: We studied 204 cases. All stroke-related performance times were faster in patients managed with stroke team activation compared to no activation, including quicker door to CT acquisition (median 24 versus 48 minutes, P < .001) and door to hemostatic medication initiation (63 versus 99 minutes, P = .005). These associations were confirmed in adjusted models. Stroke codes were activated in 43% of cases and were more likely in patients with shorter onset-to-arrival times, higher National Institutes of Health Stroke Scale scores, and higher Glasgow Coma Scale scores. CONCLUSIONS: Stroke team activation was associated with more rapid diagnostic and therapeutic interventions for patients with ICH, but activation did not occur in the majority of cases, implying absence of early recognition. A stroke team activation process improves care performance, but leveraging the advantages of existing systems will require improved triage tools to identify ICH in the acute setting.

A novel kinematics analysis method using quaternion interpolation-a case study in frog jumping.

Spherical Linear Interpolation (SLERP) has long been used in computer animation to interpolate movements between two 3D orientations. We developed a forward kinematics (FK) approach using quaternions and SLERP to predict how frogs modulate jump kinematics between start posture and takeoff. Frog limb kinematics have been studied during various activities, yet the causal link between differences in joint kinematics and locomotor variation remains unknown. We varied 1) takeoff angle from 8 to 60°; 2) turn angle from 0 to 18°; and 3) initial body pitch from 0 to 70°. Simulations were similar to experimentally observed frog kinematics. Findings suggest a fundamental mechanism whereby limb elevation is modulated by thigh and shank adduction. Forward thrust is produced by thigh and proximal foot retraction with little contribution from the shank except to induce asymmetries for turning. Kinematic shifts causing turns were subtle, marked only by slight counter-rotation of the left versus right shank as well as a 10% timing offset in proximal foot adduction. Additionally, inclining initial body tilt influenced the centre of mass trajectory to determine direction of travel at takeoff. Most importantly, our theory suggests firstly that the convergence of leg segment rotation axes toward a common orientation is crucial both for limb extension and for coordinating jump direction; and, secondly, the challenge of simulating 3D kinematics is simplified using SLERP because frog limbs approximately follow linear paths in unit quaternion space. Our methodology can be applied more broadly to study living and fossil frog taxa as well as to inspire new control algorithms for robotic limbs.