Squat Jump (SJ)

The squat jump (SJ) is a complimentary assessment tool to the CMJ for lower body power starting from a semi-squat position.

About:
The SJ, similar to CMJ, measures the ability to accelerate the COM vertically, but does so from a stationary semi-squat position rather than utilizing an initial downward movement. This change in the starting position minimizes the influence of the stretch shortening cycle and stored elastic energy, resulting in a reliably reduced jump height compared to the CMJ. Because of the emphasis on the propulsive phase of the jump, the SJ is good choice to measure lower body power and has been demonstrated to be sensitive to changes due to accumulated neuromuscular fatigue, making it an ideal tool to monitor player training load.

References:
[1] Harris, N. K., Cronin, J. B., Hopkins, W. G., & Hansen, K. T. (2008). Relationship Between Sprint Times and the Strength/Power Outputs of a Machine Squat Jump. Journal of Strength and Conditioning Research, 22(3), 691–698. https://doi.org/10.1519/JSC.0b013e31816d8d80
[2] Linthorne, N. P. (2001). Analysis of standing vertical jumps using a force platform. American Journal of Physics, 69(11), 1198–1204. https://doi.org/10.1119/1.1397460
[3] Loturco, I., D’Angelo, R. A., Fernandes, V., Gil, S., Kobal, R., Cal Abad, C. C., Kitamura, K., & Nakamura, F. Y. (2015). Relationship Between Sprint Ability and Loaded/Unloaded Jump Tests in Elite Sprinters. Journal of Strength and Conditioning Research, 29(3), 758–764. https://doi.org/10.1519/JSC.0000000000000660
[4] Sams, M. L., Sato, K., DeWeese, B. H., Sayers, A. L., & Stone, M. H. (2018). Quantifying Changes in Squat Jump Height Across a Season of Men’s Collegiate Soccer. Journal of Strength and Conditioning Research, 32(8), 2324–2330. https://doi.org/10.1519/JSC.0000000000002118
[5] Vanezis, A., & Lees, A. (2005). A biomechanical analysis of good and poor performers of the vertical jump. Ergonomics, 48(11–14), 1594–1603. https://doi.org/10.1080/00140130500101262