Accelerometry Feedback

Using Real-time Accelerometry feedback to Improve Recoil Management

Recoil management plays an integral role in shooting accuracy, timing, and safety. Recoil is the end result of a transfer of energy beginning with the ignition of chemical propellant, transferring to the cartridge case, the breach, and finally to the hands. Although the initial energy wave lasts roughly just 1 millisecond (based on an approximate projectile velocity of 123.4 m/s), the resultant physical impulse will last over a significantly longer period of time, up to several 100 milliseconds. As visible via high-speed photography, recoil first compresses the soft tissue of the hand over approximately 20-50 ms as energy is transferred from the point of contact, the grip. Only after this initial compression does energy begin to transfer to the rigid bio mechanical components of the arm, the wrist, elbow, and shoulder. This will ultimately result in both rearward and rotational motion, in other words, muzzle lift.

The magnitude of the effects of recoil on the body are heavily influenced by alignment and bracing with small biomechanical adjustments resulting in significant changes in kinematics. However, even when correct presentation and shooting techniques are taught, repeated practice is vital. As with all motor learning, subtle individual differences must be accounted for by the practitioner themselves in order to create an efficient and effective motor pattern. Unfortunately, adequate feedback is not always available. A trainee may not correctly gauge the degree to which recoil is affecting them and shot accuracy is not always the best determinant, especially in single fire drills. Likewise, a trainer cannot be present constantly to make corrections nor should they be since too much criticism can have detrimental effects on learning.

We propose an integrated hardware/software system to enable improved recoil management by providing objective feedback. The system is comprised of a wireless accelerometer with a sampling rate of 800 Hz detecting forces up to 16 gs. This sensor will be worn around the wrist of the shooting hand, sending a signal to a mobile device worn on the upper arm. We will develop software that will run on this device, detecting acceleration data, calculating peaks, and presenting them to both the user and trainer. Improvements in recoil management via biomechanical changes will be reflected in reduced acceleration readings since proper bracing will attenuate the forces transmitted through the hand-wrist complex. Participants will be able to quickly review the impact of different, often subtle, changes in stance, upper body orientation, arm alignment, and hand positioning on recoil immediately after individual shooting drills. We predict real-time feedback of this sort will facilitate better learning, improved attention to critical details, and decrease the time necessary to learn proper recoil management skills.

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