What makes a good isometric strength test using AxIT Dynamometers and Force Plates?
Good testing makes for great outcomes. To ensure you get the best information about the people you work with, it is important to make sure that your Isometric Strength Testing protocols are standardized and accurate to ensure you are testing and tracking the same movements. This is particularly important for tests involving Stomp-IT Force Plates and Pull-IT tension dynamometers where sudden shock forces from impact against resistance can dramatically affect results.
Here are some tips to ensure your results are accurate.
Accurate Isometric Test
- Pretension: The client begins the test by taking up the slack in the test. This could involve pulling into the bar to tension an IMTP test or applying some tension across a strap for a knee extension test using the Pull-IT. This limits any shock loading that could give inaccurate Peak Force and RFD data.
- Table Top Shape: Ideally, an isometric test force trace should resemble a "table top" shape. That is they apply force quickly, sustain the force for the duration of the test, and then relax. If the shape of the force trace is different to this it could be due to poor testing technique or maybe a fatigue or lack of control in the contraction.
- Adequate Test Duration: For greatest accuracy, isometric strength tests are best performed across a 3-5 second duration of sustained effort.
Inaccurate Isometric Test
- No Pretension: The client applies no pretension across the testing device and rapidly accelerates until impact and sudden stop against a resistance they cannot overcome.
- Shock Loaded Peak: Usually due to a lack of pretension before commencing the rep the sudden impact of the movement as the client hits resistance results in a Shock Loaded Peak. This peak will typically look like multiple peaks rapidly moving up and down at the start of the movement and will result in artificially enhanced results in both Peak Force and RFD as the acceleration meets the sudden braking force.
- Inconsistent Effort: Ideally the client sustains the effort in the rep for the full duration. If the force trace moves up and down through the effort the client may alter their effort back and forth resulting in an inconsistent result.
- Inadequate Test Duration: Isometric testing is best performed across a minimum of a 3-second sustained effort. Any less than this may result in inconsistent results.