Abstract
This study examined the effects of four different lower extremity kinetic chain states (KCS) on spinal flexor and extensor muscle performance during concentric isokinetic activity. The KCS involved different combinations of joint stabilization: ankle, knee, and hip/pelvis (Closed), knee and hip/pelvis (Open 1), ankle and hip/pelvis (Open 2), and hip/pelvis (Open 3). Twenty volunteer subjects (11 males, 9 females; age range 15–23 yr) were tested on a Cybex TEF isokinetic spinal dynamometer at the speed of 60 deg/sec in a sequential repeated measures design of four different test sessions, each separated by a period of 48 h. Testing involved five maximal spinal flexion/extension repetitions through a 0–60 deg motion arc as peak torque data were collected by the device's computer system. ANOVA failed to show significant differences between test motions (p = 0.668) or the factors of test motion x KCS (p = 0.955), but did show a difference between individual KCS (p < 0.001). Post hoc Scheffe tests showed significant differences between Closed and all Open KCS, between Open 3 and the other Open KCS, but failed to show a difference between the Open 1 and Open 2 KCS. It was concluded that a Closed KCS had a greater influence on lumbar muscle output than Open KCS and that the output influence decreased as KCS became progressively less constrained.