@article {11567,
	title = {Acute Improvement of Vertical Jump Performance After Isometric Squats Depends on Knee Angle and Vertical Jumping Ability.},
	journal = {J Strength Cond Res},
	volume = {30},
	year = {2016},
	month = {2016 Aug},
	pages = {2250-7},
	abstract = {Tsoukos, A, Bogdanis, GC, Terzis, G, and Veligekas, P. Acute improvement of vertical jump performance after isometric squats depends on knee angle and vertical jumping ability. J Strength Cond Res 30(8): 2250-2257, 2016-This study examined the acute effects of maximum isometric squats at 2 different knee angles (90 or 140{\textdegree}) on countermovement jump (CMJ) performance in power athletes. Fourteen national-level male track and field power athletes completed 3 main trials (2 experimental and 1 control) in a randomized and counterbalanced order 1 week apart. Countermovement jump performance was evaluated using a force-plate before and 15 seconds, 3, 6, 9, and 12 minutes after 3 sets of 3 seconds maximum isometric contractions with 1-minute rest in between, from a squat position with knee angle set at 90 or 140{\textdegree}. Countermovement jump performance was improved compared with baseline only in the 140{\textdegree} condition by 3.8 {\textpm} 1.2\% on the 12th minute of recovery (p = 0.027), whereas there was no change in CMJ height in the 90{\textdegree} condition. In the control condition, there was a decrease in CMJ performance over time, reaching -3.6 {\textpm} 1.2\% (p = 0.049) after 12 minutes of recovery. To determine the possible effects of baseline jump performance on subsequent CMJ performance, subjects were divided into 2 groups ("high jumpers" and "low jumpers"). The baseline CMJ values of "high jumpers" and "low jumpers" differed significantly (CMJ: 45.1 {\textpm} 2.2 vs. 37.1 {\textpm} 3.9 cm, respectively, p = 0.001). Countermovement jump was increased only in the "high jumpers" group by 5.4 {\textpm} 1.4\% (p = 0.001) and 7.4 {\textpm} 1.2\% (p = 0.001) at the knee angles of 90 and 140{\textdegree}, respectively. This improvement was larger at the 140{\textdegree} angle (p = 0.049). Knee angle during isometric squats and vertical jumping ability are important determinants of the acute CMJ performance increase observed after a conditioning activity. },
	keywords = {Adult, Athletes, Athletic Performance, Exercise, Humans, Isometric Contraction, Knee Joint, Male, muscle fatigue, Track and field, Young Adult},
	issn = {1533-4287},
	doi = {10.1519/JSC.0000000000001328},
	author = {Tsoukos, Athanasios and Bogdanis, Gregory C and Terzis, Gerasimos and Veligekas, Panagiotis}
}
