110317 Posture and the relationship to strength
The display of strength is influenced by the joint angles of the operating links in the chain. These angles, as would be expected, change with movement. Because of this change, the length of the muscles varies throughout the movement, as does the angle of attachment to the bone.
This means the muscles ability to produce more, or less, force is determined by the angle as the leverages and “moment of muscular force changes the mechanical conditions of work.” This postural condition may benefit strength output if the “force potential of the muscles is used fully” but it can also be “hindrance when only part of their maximal tension can be used.”
Based strictly on observation it is clear that strength is affected either negatively or positively by various postural changes. As an example, most athletes are able to lift more weight in the dead lift than in a straight leg dead lift. This is a classic case of minor changes in the positioning of the links in the chain leading to tremendous strength advantages. In other words if the legs are bent and allowed to participate in the lift much more is hoisted up. It only stands to reason that the more muscles involved the more will be lifted.
Maximal force output at the working joints is truly dependent “upon the position of the system’s links relative to the proximal joints.” For example, the force developed in extension or flexion of the knee joint is determined by the angle at the hip joints. Thus, maximal force in hip extension in the seated position was found to be at an angle of 160° in the knee joint.
“In the leg press (lying on the back)” there was no difference “in knee extension force”…found at hip angles of 100° up to and including 140°’s. “Knee extension strength increases by 10%-12% if the torso is inclined 20° to 25° backward from the vertical with the subject seated in a rowing position. Thus, to produce maximal force in a movement, one must consider anatomical stability and ensure that at crucial moments posture enables the muscles to develop maximal external force.
Try different stances, different hand grips, and different joint angles during your lifts to increase your power output capacity. Just because Ed Coan or Fred Hatfield squats, a certain way does not mean it will be as effective or efficient for you to do likewise.
Postural changes, however slight, may make big differences in how much maximal force you are able to produce. Try it and see for yourself.
Final note: If you are considering a personal trainer or are training in a local health club, ask about the certification status of the staff. The qualified trainers will be happy to show you their credentials. Remember, it’s your money and more importantly your body, so go with the qualified instructors so you get correct guidance.
* The source of the information comes from the American Physical Therapy Association book entitled BODY MAINTENANCE AND REPAIR. The authors are Marilyn Moffat, PT, Ph.D., FAPTA and Steve Vickery. It is an excellent book that discusses the many systems of the human body.