This week we're talking about a new classification approach for the stretch-shortening cycle! The original distinction of fast vs slow movements based on a ground contact time of 250 ms was developed in the 90's, and has not been subjected to much critique since it was introduced. Therefore, the authors aim to confirm the validity of the 250 ms threshold value by investigating factors relating to ground contact time during a drop jump test. They recruited 46 recreationally active, college age men who were sports science students to perform one day of drop jump testing and one day of shear wave elastography to determine muscle and tendon parameters, like penattion angle, stiffness, and thickness. They used a classification and regression tree analysis (CART analysis) using machine learning to analyze their 27 different variables. They created three threshold criteria based on ground contact time: short GCT < 188 ms, mid GCT 188-222 ms, and long GCT >222 ms. It is interesting that all of their thresholds are considered "fast" according to the classical distinction. Listen to the podcast to learn our critiques of this article, and possible paths forward from this!

The abstract can be found here: https://pubmed.ncbi.nlm.nih.gov/39317922/

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