Calculating Striking Mechanics: Water-filled Punching Bag

Combat sports incorporate two types of motions: striking and grappling. In striking-focused combat sports, strikes include punches, elbows, kicks, and knees. Measuring striking forces can provide valuable information to improve the performance of combat sport athletes. 

Recently, a boxing and fitness company based in New York revealed its Aqua Training Bag: a water-filled punching bag that “integrates a pressure sensor to provide a real-time kinetic assessment of peak impact forces.” Shelley N. Diewald and colleagues conducted a study to evaluate the validity and reliability of this sensor for measuring peak impact force during striking motions.

A pendulum design with an attached kettlebell was set up to swing and create contact with the Aqua Training Bag, simulating the human punch. The pendulum’s mass load (kettlebell) and arc of travel (height) was changed throughout the experiment to gather more data. For each of the different pendulum setups, the momentum of the kettlebell mass at impact with the Aqua Training Bag was calculated. This data was compared with the measured impact forces from the Aqua Training Bag’s pressure sensor.

The researchers found that “peak force output detected by the pressure sensor was very strongly associated with calculated momentum.” In addition, researchers observed “low systematic error and high absolute and relative consistency … across all loading conditions,” demonstrating good reliability. Overall, the Aqua Training Bag provided reliable and valid measurements of peak impact forces. 

However, the researchers cite limitations that may necessitate further research and evaluation of the Aqua Training Bag. In this study, the pendulum and its mass were always set in a “stationary and standardized condition” to control impact momentum. This “represents a relatively narrow view of striking” in combat sports training, as, for example, an athlete may repeatedly punch a moving bag that continues to swing back and forth. Therefore, further research should be conducted to evaluate the practical utility of the Aqua Training Bag for measuring the striking kinetics of athletes.

Image was obtained from the mentioned paper authored by Shelley N. Diewald and colleagues (article is open access and licensed under a Creative Commons Attribution 4.0 International License)