NOTE: End date changed to 5/31/2017 per NSBRI (Ed., 3/8/17)

NOTE: Start/End dates changed to 3/1/2015 and 2/28/2017, respectively (original start/end dates were 12/1/2014 and 11/30/2016, respectively) per NSBRI (Ed., 7/27/15)

Original Project Aims/Objectives: This project aims to develop a biomechanical model of a human performing the deadlift exercise on the Hybrid Ultimate Lifting Kit (HULK) device in order to inform exercise prescriptions for astronauts so that their musculoskeletal health can be maintained during extended periods of spaceflight. To create this model, which has been developed using the OpenSim software platform, it was necessary to collect data (including motion capture, ground reaction force, and EMG) from human subjects performing the deadlift exercise. Trials using different combinations of load, load configuration, exercise cadence, and stance width were performed. Inverse kinematics and inverse dynamics analyses have been performed and are ongoing, and subsequent steps of analysis include residual minimization and potentially static optimization.

Key Findings: To date, we have collected motion capture, electromyography (EMG), force plate, and device load cell data from 5 human subjects performing 73 trials of the deadlift exercise with varying load, load configuration, stance width, and exercise cadence. We report the joint angle characteristics resulting from inverse kinematics analysis for selected joints in the biomechanical model, inverse dynamics analyses reporting joint moments, as well as EMG results for 16 muscles recorded. We are currently able to draw tentative conclusions about how the exercise configuration parameters affect the kinematic and kinetic properties of a subset of the subjects being modeled, but more extensive analyses of the collected data (and, potentially, additional data collection) will be necessary before stronger conclusions can be reached.

Impact of Key Findings on Hypotheses, Technology requirements, Objectives and Specific Aims of the Original Proposal: As previously mentioned, the current set of key findings includes the kinematic, kinetic, and muscle activity properties of the human subjects being modeled as the deadlift load, load configuration, stance width, and cadence are varied. Based on the analyses completed to date, we are able to draw tentative relationships between these deadlift exercise parameters and the joint angles, joint moments, and EMG activities that result. This will eventually permit our Digital Astronaut Project team to make predictions about how particular exercise devices and prescriptions are likely to benefit the musculoskeletal health of the astronauts performing these exercises. This will assist us in optimizing exercise prescriptions for astronauts exposed to microgravity environments for extended periods.

Research Plan for Coming Year: Not applicable since this is the final report for this 2-year project. The Digital Astronaut Project's Biomechanics team will continue data collection and analysis pursuant to the objectives described above.

I completed Step 2, Perform Data Processing and Reduction, on the collected data. This processing included data filtering, interpolation, tracking, and downsampling.

In Step 3, with members of the Digital Astronaut Project, three different versions of a biomechanical model of the human body performing the deadlift exercise were developed on the OpenSim software platform; one version excludes arms and represents the upper-extremity forces as being concentrated in the shoulders; the second version includes full musculature in the arms; and the third version simplifies the arms by including torque actuators rather than muscles. The latter two models address Step 4. We selected the third model for use in subsequent analyses due to its computational efficiency and the requirement when modeling in OpenSim that the deadlift, which is a closed-kinetic-chain exercise, include arms in its model to enable attachment to the model's bar.

In Step 5, I performed Inverse Kinematics analysis to yield descriptive kinematics. For selected trials and subjects, progress has been made on Step 6, Inverse Dynamics (ID) analysis, which involves formulating and solving the system's equations of motion, to determine the generalized forces (e.g., net joint forces and torques, ground reaction forces, and residual forces and moments on the pelvis) that produce the deadlift movement; this permits the inference of how muscle groups are activated in order to produce this movement. Work is ongoing to complete ID analyses.

Step 7, minimizing the residuals (errors resulting from the process of computational modeling) of the system, is performed following ID analysis, which still remains to be completed for all subjects and trials.

Step 8, performing static optimization, will require modifications to the model to allow it to accurately predict muscle force values at joints where extreme flexion occurs during the exercise.

Part of Step 9, creating data reports, has been completed, while its other component, performing sensitivity analysis, will follow once the preceding steps have been completed.

Finally, Step 10 involves conducting verification and validation (V&V) analyses for this modeling effort. I have created a detailed verification and validation plan for this project, which has been and will be implemented as the stages of the project are completed. My lab members plan to use this deadlift modeling V&V plan as the reference for their own V&V planning work when studying other exercises.

NOTE: End date changed to 5/31/2017 per NSBRI (Ed., 3/8/17)

NOTE: Start/End dates changed to 3/1/2015 and 2/28/2017, respectively (original start/end dates were 12/1/2014 and 11/30/2016, respectively) per NSBRI (Ed., 7/27/15)

Original Project Aims/Objectives: This project aims to develop a biomechanical model of a human performing the deadlift exercise on the Hybrid Ultimate Lifting Kit (HULK) device in order to inform and ultimately optimize exercise prescriptions for astronauts so that their musculoskeletal health can be maintained during extended periods of spaceflight. To create this model, which has been developed using the OpenSim software platform, it was necessary to collect data (including motion capture, ground reaction force, and EMG) from human subjects performing the deadlift exercise. Trials using different combinations of load, load configuration, exercise cadence, and stance width were performed. Inverse kinematics and inverse dynamics analyses are in the process of being performed, and will be followed by residual minimization and static optimization.

Key Findings: To date, we have collected motion capture, electromyography (EMG), force plate and load cell data from 2 human subjects performing 26 trials of the deadlift exercise with varying load, load configuration, stance width, and exercise cadence. We report the joint angle characteristics resulting from inverse kinematics analysis for selected joints in the biomechanical model, as well as the EMG results for all 16 muscles recorded. We are currently able to draw tentative conclusions about how the exercise configuration parameters affect the kinematic and muscle activation properties of the subject being modeled, but more extensive analyses of the collected data (and, potentially, additional data collection) will be necessary before stronger conclusions can be reached.

Impact of Key Findings: As previously mentioned, the current set of key findings includes the kinematic and muscle activity properties of the human subjects being modeled as the deadlift load, load configuration, stance width, and cadence are varied. We are able to draw tentative relationships between these deadlift exercise parameters and the joint angles and EMG activities that result. This will eventually permit our Digital Astronaut Project team to make predictions about how particular exercise devices and prescriptions are likely to benefit the musculoskeletal health of the astronauts performing these exercises. This will assist us in optimizing exercise prescriptions for astronauts exposed to microgravity environments for extended periods.

Research Plan for Coming Year: In the coming year, I will continue to conduct inverse kinematics (IK) analysis for the collected deadlift data. Subsequent to IK analysis, inverse dynamics (ID) analysis will be performed in order to determine the generalized forces that produce the deadlift exercise. This will allow the inference of how muscle groups are activated to produce this movement. Next, residual reduction will be performed to minimize errors associated with the modeling process. Static optimization analysis will follow, in which the calculated net joint moments are resolved into muscle forces at each time step based on the minimization of joint angle errors and muscle force magnitude. Sensitivity analyses will then be performed to determine how key parameters influence the behavior of the system as a whole. Data reports will be produced that describe these sensitivity analyses, as well as each preceding step in this project. Finally, verification and validation of the model, which is an ongoing process throughout the modeling effort, will be concluded in order to assess the credibility of this biomechanical deadlift model to optimize astronaut exercise prescriptions.

I completed Step 2, Perform Data Processing and Reduction, on the collected data. This processing included data filtering, interpolation, tracking, and downsampling. Subsequently, in Step 3, in consultation with my lab members, I developed a biomechanical model of the human body performing the deadlift exercise, using the OpenSim software platform. Further development of the model is currently being performed to improve shoulder stability of the model and to optimize efficiency. Using that model, in Step 4, I scaled this model by matching the model's virtual markers to the collected motion capture data.

In Step 5, I have been performing inverse kinematics analysis to yield the descriptive kinematics of the subject-specific model performing the deadlift exercise on the HULK device. This work is ongoing, as it needs to be performed for each of the trials collected. For selected trials, I have also started work on Step 6, inverse dynamics analysis, which involves formulating and solving the system's equations of motion, to determine the generalized forces (e.g., net joint forces and torques, ground reaction forces, and residual forces and moments on the pelvis) that produce the deadlift exercise; this will permit the inference of how muscle groups are activated in order to produce this movement.

I have not yet started on Step 7, minimizing the residuals (errors resulting from the process of computational modeling) of the system, nor have I undertaken Step 8, performing static optimization. Step 9, performing sensitivity analysis and creating data reports, will follow once I have completed the preceding steps. Finally, Step 10 involves conducting verification and validation (V&V) analyses for this modeling effort. I have created a detailed verification and validation plan for this project, which will be implemented as the stages of the project are completed. My lab members plan to use this V&V plan for the deadlift exercise as a reference for their own V&V planning work when studying other exercises.

Spaceflight subjects astronauts to microgravity conditions, and extended exposure to these environments causes muscle atrophy and loss of bone density that can lead to loss of function during missions, as well as harmful effects that endure after return to Earth. Resistive exercise is an essential microgravity countermeasure that has been shown to mitigate the harmful effects of reduced gravity on the human musculoskeletal system. The Hybrid Ultimate Lifting Kit (HULK) device (ZIN Technologies, Inc.) has recently been developed to provide astronauts with a range of resistive exercises within a mission-ready footprint. Among the movements permitted by the HULK device, the deadlift is central to an effective exercise regimen, as it works the leg, hip, torso, and back muscles, which often suffer the most significant declines during spaceflight missions. The ability to model the deadlift movement in a simulated environment will permit the development of customized prescriptions of exercise on the HULK device for astronauts, through analysis of variations in device configuration and human posture, stance, grip, and cadence, resulting in the prediction of configuration that will result in optimal countermeasure exercise. Gravity in the simulated environment can be reduced in order to predict the system modifications necessary to achieve optimal exercise results in a microgravity environment, without requiring the collection of data during spaceflight, which is expensive and difficult to acquire. In pursuit of a predictive musculoskeletal model that will ultimately permit the prescription of device configuration properties and human exercise techniques to achieve effective deadlift exercise on the HULK device, we propose to create a descriptive musculoskeletal model based on collected human motion capture data. Recorded human data will be used to create a full-body musculoskeletal model using the OpenSim software platform. Analyses will be performed using this musculoskeletal simulation, and we will compare the model’s evaluations against experimental values of deadlift performance. Sensitivity of the model to its key parameters, as well as verification and validation analyses, will be performed to assess the ability of the model to provide useful information for the purpose of optimizing deadlift exercise training on the HULK device.