The Effect of Initial Knee Angle on Concentric-Only Squat Jump Performance.
OBJECTIVE
There is uncertainty as to which knee angle during a squat jump (SJ) produces maximal jump performance. Importantly, understanding this information will aid in determining appropriate ratios for assessment and monitoring of the explosive characteristics of athletes.


METHODS
This study compared SJ performance across different knee angles-90º, 100º, 110º, 120º, 130º, and a self-selected depth-for jump height and other kinetic characteristics. For comparison between SJ and an unconstrained dynamic movement, participants also performed a countermovement jump from a self-selected depth. Thirteen participants (Mage= 25.4 ± 3.5 years, Mheight= 1.8 ± 0.06 m, Mweight= 79.8 ± 9.5 kg) were recruited and tested for their SJ performance.


RESULTS
In the SJ, maximal jump height (35.4 ± 4.6 cm) was produced using a self-selected knee angle (98.7 ± 11.2°). Differences between 90°, 100°, and self-selected knee angles for jump height were trivial (ES ± 90% CL = 90°-100° 0.23 ± 0.12, 90°-SS -0.04 ± 0.12, 100°-SS -0.27 ± 0.20; 0.5-2.4 cm) and not statistically different. Differences between all other knee angles for jump height ranged from 3.8 ± 2.0 cm (mean ± 90% CL) to 16.6 ± 2.2 cm. A similar outcome to jump height was observed for velocity, force relative to body weight, and impulse for the assessed knee angles.


CONCLUSIONS
For young physically active adult men, the use of a self-selected depth in the SJ results in optimal performance and has only a trivial difference to a constrained knee angle of either 90° or 100°.
a Australian Institute of Sport.|b University of Canberra.
Lachlan J
LJ
Mitchell
b University of Canberra.|c Brumbies Super Rugby.
Christos K
CK
Argus
d Cycling Australia.
Kristie-Lee
KL
Taylor
e Surfing Australia Hurley High Performance Centre.|f Edith Cowan University.
Jeremy M
JM
Sheppard
a Australian Institute of Sport.|f Edith Cowan University.
Dale W
DW
Chapman
D000328:Adult; D001696:Biomechanical Phenomena; D006801:Humans; D007719:Knee Joint / Q000033:anatomy & histology* / Q000502:physiology*; D008297:Male; D009068:Movement; D059385:Plyometric Exercise
Concentric-only jump; knee angle; relative net impulse; squat depth