Cross-Cutting Computational Modeling Project: Exploration Medical Station Analysis

Astronauts will be away from Earth-based medical care for long periods during future exploration missions. Thus, it will be necessary for the astronauts to perform various medical tasks to monitor and maintain their health in the microgravity environment of space. Performance of these tasks will be constrained due to the limited volume available to perform the task, the absence of gravity and the limited resources and capabilities available in the medical work area. It is therefore necessary to evaluate exploration medical workstation designs for how well the designs will support crew performance of medical tasks. This evaluation featured two trained medical caregivers (99th percentile male, 26th percentile female) performing emergent care procedures (alone and in tandem) on a medical manikin. The procedures came from the The procedures came from the International Space Station Medical Checklist, and they are designed for spaceflight. The objectives of the evaluation included determining the operational volume required to perform the tasks, examining the effect of constraining the operational volume with partitions, determining candidate locations for foot restraints and equipment placements and determining the effect of single vs. dual caregiver on the operational volume.A marker-based motion capture system collected the motion data, which enabled computation of operational volumes and foot placement maps using custom Python code. Additional data collected included heart rate, time to perform the procedures, and feedback from the caregivers in the form of the NASA Task Load Index (TLX), the US Government System Usability Survey, and an open-ended questionnaire

The Digital Astronaut Project Bone Remodeling Model

Under the conditions of microgravity, astronauts lose bone mass at a rate of 1% to 2% a month, particularly in the lower extremities such as the proximal femur: (1) The most commonly used countermeasure against bone loss has been prescribed exercise, (2) However, current exercise countermeasures do not completely eliminate bone loss in long duration, 4 to 6 months, spaceflight, (3,4) leaving the astronaut susceptible to early onset osteoporosis and a greater risk of fracture later in their lives. The introduction of the Advanced Resistive Exercise Device, coupled with improved nutrition, has further minimized the 4 to 6 month bone loss. But further work is needed to implement optimal exercise prescriptions, and (5) In this light, NASA's Digital Astronaut Project (DAP) is working with NASA physiologists to implement well-validated computational models that can help understand the mechanisms of bone demineralization in microgravity, and enhance exercise countermeasure development

Effect of Loading Configuration on Kinematics and Kinetics for Deadlift and Squat Exercises: Case Study in Modeling Exercise Countermeasure Device for Astronauts

This study compares squat and deadlift exercises performed with two different loading configurations: 1) on a novel single-cable resistance exercise countermeasure device (ECD) for spaceflight and 2) with free weights. The results compare joint kinematics and kinetics between different loading configurations for each exercise, and also between the two exercises for each loading configuration. Single-cable versions of the squat (using a harness) and deadlift (using a T-bar) performed on the Hybrid Ultimate Lifting Kit (HULK) ECD have significantly different sagittal plane joint angle kinematics (both peak angle and range of motion) as well as joint kinetics (both peak joint moment and joint impulse) vs. their free weight equivalents at the same load. Differences also exist in hip abduction and rotation. Overall, the single-cable configurations tend to reduce peak joint angles, ranges of motion, peak joint moment and joint impulse vs. free weights. A notable exception is the lumbar joint, which is more heavily loaded for single-cable squats vs. free weight squats. This may have implications for both training benefit and possible risk of injury. Deadlift and squat exercises work the lower body musculature in different ways, with the deadlift emphasizing hip and lumbar extension and the squat emphasizing knee extension. Based on these findings, we would advocate the use of both movements in the exercise prescriptions of astronaut crews on deep-space missions

Digital Astronaut Project Biomechanical Models: Biomechanical Modeling of Squat, Single-Leg Squat and Heel Raise Exercises on the Hybrid Ultimate Lifting Kit (HULK)

The NASA Digital Astronaut Project (DAP) implements well-vetted computational models to predict and assess spaceflight health and performance risks, and to enhance countermeasure development. The DAP Musculoskeletal Modeling effort is developing computational models to inform exercise countermeasure development and to predict physical performance capabilities after a length of time in space. For example, integrated exercise device-biomechanical models can determine localized loading, which will be used as input to muscle and bone adaptation models to estimate the effectiveness of the exercise countermeasure. In addition, simulations of mission tasks can be used to estimate the astronaut's ability to perform the task after exposure to microgravity and after using various exercise countermeasures. The software package OpenSim (Stanford University, Palo Alto, CA) (Ref. 1) is being used to create the DAP biomechanical models and its built-in muscle model is the starting point for the DAP muscle model. During Exploration missions, such as those to asteroids and Mars, astronauts will be exposed to reduced gravity for extended periods. Therefore, the crew must have access to exercise countermeasures that can maintain their musculoskeletal and aerobic health. Exploration vehicles may have very limited volume and power available to accommodate such capabilities, even more so than the International Space Station (ISS). The exercise devices flown on Exploration missions must be designed to provide sufficient load during the performance of various resistance and aerobic/anaerobic exercises while meeting potential additional requirements of limited mass, volume and power. Given that it is not practical to manufacture and test (ground, analog and/or flight) all candidate devices, nor is it always possible to obtain data such as localized muscle and bone loading empirically, computational modeling can estimate the localized loading during various exercise modalities performed on a given device to help formulate exercise prescriptions and other operational considerations. With this in mind, NASA's Digital Astronaut Project (DAP) is supporting the Advanced Exercise Concepts (AEC) Project, Exercise Physiology and Countermeasures (ExPC) laboratory and NSBRI-funded researchers by developing and implementing well-validated computational models of exercises with advanced exercise device concepts. This report focuses specifically on lower-body resistance exercises performed with the Hybrid Ultimate Lifting Kit (HULK) device as a deliverable to the AEC Project

Estimation of Lower-Body Kinetics from Loading Profile and Kinematics Alone, Without Measured Ground Reaction Forces

Biomechanical models of human motion can estimate kinetic outcomes, such as joint moments, joint forces and muscle forces. Typically, one performs an inverse dynamics (ID) analysis to compute joint moments from joint angles and measured external forces. Sometimes it is impractical to measure ground reaction forces and moments (GRF&M). We devised an empirical method for performing ID analysis of resistance exercises without measured GRF&M. The method solves the multibody dynamics equations of motion with four key assumptions about the GRF&M that reduce the number of unknowns. The assumptions are 1) negligible ground reaction moments, 2) fixed lateral/medial location of the center of pressure (COP), 3) equal fore/aft location of the COP between the feet, and 4) constant angle of the GRF vector relative to the vertical axis in the frontal plane. We used evaluation trials from a spaceflight countermeasure resistance training device to test this approach. Four participants performed squat and deadlift exercises at various loads. We compared results from traditional ID analysis to results without measured GRF&M using our method. We found that joint moment trajectories in the sagittal plane were qualitatively similar in shape between the two methods, and the amount of root mean squared error (RMSE), measured by difference in joint moment impulse, was typically under 10 percent. Non-sagittal joint moment trajectories, which are much lower in overall magnitude, were not qualitatively similar in shape between the two methods. Non-sagittal moments displayed much higher RMSE, with typical values well over 50 percent. These findings were further supported by validation metrics (Sprague and Geers' P and M metrics, Pearson's r correlation coefficient). Based on these findings, we concluded that useful kinetic results are obtained from ID analysis of squat and deadlift exercises, even when GRF&M are not measured, as long as the outcomes of interest lie in the sagittal plane

Human Factors and Simulation in Emergency Medicine

This consensus group from the 2017 Academic Emergency Medicine Consensus Conference Catalyzing System Change through Health Care Simulation: Systems, Competency, and Outcomes held in Orlando, Florida, on May 16, 2017, focused on the use of human factors (HF) and simulation in the field of emergency medicine (EM). The HF discipline is often underutilized within EM but has significant potential in improving the interface between technologies and individuals in the field. The discussion explored the domain of HF, its benefits in medicine, how simulation can be a catalyst for HF work in EM, and how EM can collaborate with HF professionals to effect change. Implementing HF in EM through health care simulation will require a demonstration of clinical and safety outcomes, advocacy to stakeholders and administrators, and establishment of structured collaborations between HF professionals and EM, such as in this breakout group

Preliminary Comparison of Two-Way Satellite Time and Frequency Transfer and GPS Common-View Time Transfer During the INTELSAT Field Trial

For a decade and a half Global Positioning System (GPS) common-view time transfer has greatly served the needs of primary timing laboratories for regular intercomparisons of remote atomic clocks. However, GPS as a one-way technique has natural limits and may not meet all challenges of the comparison of the coming new generation of atomic clocks. Two-way satellite time and frequency transfer (TWSTFT) is a promising technique which may successfully complement GPS. For two years, regular TWSTFT's have been performed between eight laboratories situated in both Europe and North America, using INTELSAT satellites. This has enabled an extensive direct comparison to be made between these two high performance time transfer methods. The performance of the TWSTFT and GPS common view methods are compared over a number of time-transfer links. These links use a variety of time-transfer hardware and atomic clocks and have baselines of substantially different lengths. The relative merits of the two time-transfer systems are discussed

Uncertainty, Validation and Sensitivity Analyses of the OpenSim Muscle Model for Pre- and Post-Flight Strength Predictions

No abstract availabl