Date: Sun, 15 Jun 1997 11:57:42 -0600 (MDT) Subject: Re: (Weights-2) Knee Extensions & Powerlifting In a message dated 6/15/97 8:51:25 AM, rmuller@javanet.com (Richard Muller) wrote: >What do "open kinetic chain" and "closed kinetic chain" mean? Open Kinetic Chain involve motions where the end of the limb IS NOT fixed and is freely movable such as throwing motions and kicking motions. These movements are typically single joint or isolation movements that utilize a limited number of muscles. Thus, the knee extension. Closed Kinetic Chain involve motions where the end of the limb IS fixed and stable, such as squats and the leg press. These movements are generally multi joint movements utilizing many muscle groups to act as stabilizers and antagonists during the motion. >I don't have access to the original article, so I'll have to ask Tom for >some clarification on the study he's reporting. The finding seems to be >that leg press training did increase (isometric) leg press strength by 29 >%, did not increase knee extension strength, and did increase quad size. >OK. But then Tom says: >>Sale suggested that the failure to increase strength despite the increase >>in >muscle size [snip] >Huh? Wasn't one of the findings that strength *did* increase? Yes, strength was increased in the leg press (CKC) by 29% and quadriceps size was also increased, yet knee extension strength did NOT increase over the pre-test figures. So what Sale has found is that size and strength increases from doing CKC movements don't seem to have much of a carry over effect to strength in OKC movements. This was demonstrated in his findings. >The issue here seems to be whether extensions help build squat strength. >This study doesn't involve squats at all. Squats and leg presses have something in common....they are both closed kinetic chain exercises and they both use many of the same muscles. Now you are partially right. This study didn't use the squats in their comparison. So what we don't know at this point is how much leg press strength will actually transfer to squat strength. As reported by Fahey (1993) in an 8 week study, while lifters improved their squat strength by 75%, they only improved their leg press strength by 47% and knee extension strength by 3%. This further shows that the leg press is not a very good way to increase squat strength, but it also shows once again that the knee extension is a terrible way to increase squat strength and leg press strength. Fahey concluded that specific motor units are recruited for specific tasks. So obviously the body uses totally different motor units to preform the knee extension compared to the squat. >>the muscle and neural actions involved in the leg press are not the >>same as the muscle and neural actions in the knee extension. >should we assume that the muscle and neural actions in the leg press and >the squat *are* the same? In other words, if what we've got here is >support for the "specificity of training" principle, wouldn't that suggest >that we should be hesitant to accept leg press as a research proxy for >powerlifitng squats? That depends on what school fo thought you come from. I personally believe in the "specificity of training" principle, both from my formal education and my many years in the trenches. I haven't done a knee extension in over a decade and have a exceptional squat. I also remember in graduate school taking those concentric and eccentric leg tests. While mine was more than everyone else's, they weren't that high, being that I could squat so much weight. Why? Because these test showed OKC strength not CKC strength. I don't do leg curls or knee extensions and squat strength has been shown to not have much of a carry over effect to OKC movements. Now how does this happen? During a squat the hamstrings have a different leverage point from say the leg curl. This can be related back to the pulley effect which would give the hamstrings greater leverage than the quads. So the hams/glutes are much bigger movers in a squat then the quads. During a squat the hamstrings will extend the hip rather than flex the knee (as in a leg curl). So naturally the hamstrings would demonstrate much more strength when tested by performing hip extension than knee flexion. During the concentric phase (up) of the squat the, as the hams contract and extend the hip, the stretch of the quads cause it to extend the knee. So the hams and quads work much differently during a squat or leg press than they do in a leg curl or knee extension. The hams preform as hip extenders instead of knee flexors. So naturally neural activation patterns are much different for the quadriceps and hamstrings when they preform CKC movements then when they preform OKC movements. During the squat the hams and quads are activated at the same time to extend the hip and knee. >And: does the finding that leg press doesn't build knee extension >strength necessarily mean that the reverse wouldn't be true? If the latter >link (extensions --> squat strength) was the hypothesis under study, I >wonder why it wasn't tested directly? And does the fact that the strength >measured here was *isometric* really carry over to a powerlifting context? We are dealing with two different movements, different motor recruitment, and different neural activations. Also realize the leverage and force are much different in the knee extension and leg press of squat. The knee extension's force is applied at the shin which puts all of the compressive forces on the knee area. In fact it actually places stress on the ACL. This also increases patello-femoral compression. During the squat or leg press, the forces are directed through the tibia with less forward pressure on the knee area. This in turn places the stress higher up on the quadriceps (more in the belly of the muscle) as opposed to the teardrop area. Which explains why bodybuilders love extensions. Furthermore, in a CKC movement, the muscle contractions are sequenced across the joints to produce movement. Hope this explains the Sale study a little more. Tom McCullough MEd., MSS ------------------------------ From: Paul Chek Date: Mon, 16 Jun 1997 06:35:16 -0600 (MDT) Subject: (Weights-2) Open vs Closed chain exercise **NBAF WEIGHTS-2** Regarding Richard Muller's question: >What do "open kinetic chain" and "closed kinetic chain" mean?< The terms "Open and Closed Kinetic Chain" were developed by Dr. Steindler and my recollection of the first published item referring to the terms is "Text Book Of Kinesiology", published in 1956. Because I am currently in Australia lecturing and running internships I don't have access to my library and can't give you the publisher although it is long out of print. To simplify the terms, OPEN KINETIC CHAIN exercises are those exercises in which the force applied by the body is great enough to overcome the resistance. An example of an open chain exercise would be a bench press, or any leg press which allows the force applied to move the load away from the body. In contrast, CLOSED KINETIC CHAIN EXERCISES are those in which the force applied is not great enough to overcome the resistance. Examples would be the push-up and squat exercises. To clarify for the novice list reader, even though the load applied during the squat is on the body, the force generated is applied to the ground, not the bar. To move the bar, the lifter must apply a force against the earth great enough to overcome the resistance created by the load on the bar. How this information is relevant to Richard Muller's questions regarding knee extensions as a means of improving squat strength: The knee extension is performed such that the thigh is fixed to the machine, while the knee extension force generated by the quadriceps serves to move the tibia across the femur. In a squat, the trunk, hip and knee extensors act as prime movers, moving the femur across the tibia, which is the fixed distal segment (along with the foot) in this closed kinetic chain exercise. The relevance here lies in the fact that the motor recruitment patternsfor the knee extension are 180 degrees out of phase with the recruitment patterns activated by the CNS to perform the squat. Another classic exampleis the difference between performing a lat pull down and a chin-up. Any serious climber will tell you that there is a huge difference in the strength quality necessary to perform a closed chain pull-to-press over a rock ledge and an open chain lat pull down." It is this very point which must be considered when designing resistance training programs for athletes. If for example you use an open chain leg press in attempt to develop explosive strength for sprinting, you will NEVER achieve optimal performance. To shed further light on this potentially "very deep subject", when training a cyclist, you have carryover from both open chain and closed chain exercises due to the very nature of cycling (pushing the pedal down from a seated position vs. standing and driving a big gear or during an intense hill climb). I choose this example because this is where Open and Closed Chain have a grey area: Initially, when the cyclist stands up to drive downward on the pedal, his body may momentarily move away from the pedal, until the arms counter the upward movement of the body - turning the movement into an open chain movement as the pedal descends away from the body. The same scenario can be developed for a boxer punching an opponent in the head; the chain is closed upon contact, yet opens as the force of the arm overcomes the momentary resistance created by the head (a concept I am very familiar with by the way!). This is why boxers can be seen doing both open and closed chain exercises in their training programs, if their coach knows what he is doing! In bodybuilding, the concept of open and closed chain is far less relevant because there is no athletic component to bodybuilding; the goal being to have the biggest muscles, the best proportions and a good posing routine. Bodybuilders can benefit greatly from this information though, as alternating between open and closed chain exercises serves to more fully develop both the nervous system and musculature due to the variety of recruitment patterns needed. To give another illustration that may help clear the confusion, consider that running is a closed chain dominant exercise (you apply force against the earth and you move), while cycling is predominantly an open chain exercise (press on the pedal and it moves away from you). If there was any real transfer of strength qualities and skills developed, Carl Lewis would make a hell of a track cyclist and the Race Across America would probably be won by an ultra distance runner, or vice versa. There are many other factors I could go into but it is dinner time! This information should be standard to all who prescribe exercises. The reasons above should make it obvious why!! Sincerely, Paul Chek MSS, HHP, NMT PAUL CHEK SEMINARS US - 1-800-552-8789 New Zealand and Australia 64-9-478-2111 FOR SEMINAR & VIDEO INFORMATION www.paulchekseminars.com