Biomechanics of the Sticking Point Originally posted to the weights mail list Dec. 14, 1995 Subject: Bench Press Sticking Point Date: Thu, 14 Dec 95 From: David Sandler A few people have asked me to pursue the reason why a sticking a point exists in the bench press movement. I have two versions: the short for those who do not wish to read the whole article and the long for those interested in the biomechanical reason. The Short: there is point in the movement, where leverage of certain muscles acting about the shoulder joint, are at a mechanical disadvantage. The Long: Excerpts from my thesis on a Biomechanical Analysis of the Bench Press (thesis is not yet published, name may change, of course it has to be published first :) Note: this is only parts on the sticking region from my thesis. The bar path during the bench press moves along arc rotating about the shoulder axis. There are three important characteristics: First, the shoulder joint lacks stability being a ball in socket because a force exerting muscle must act with others to avoid dislocation (Zuckerman & Madsen III, 1989). Thus a force couple is necessary between the muscles. Secondly, some muscles span two joints, and forces must work together to move both joints. And thirdly, studies by Celli (1985), Ekholm(1978), Sigholm (1984) and Zuckerman & Madsen III (1989) show eight muscles involved in shoulder movement. These are: anterior, posterior, and medial delts, the traps, and the four rotator cuff muscles. EXTRA: it is suggested and proven that the more linear path the bar makes, rather than arc movement, will work forces more effectively (Madsen & McLaughlin, 1984). further, the more experienced lifters generally followed a more linear path. (found by slow motion cinematography). Sticking point occurs because of this non linear movement. Elliot, Wilson & Kerr (1989) found the sticking region to be at the transition phase of the muscles, creating a disadvantageous moment arm at that particular point, which decreases the force potential and deceleration to the bar. Transition from the chest, deltoid, and tricep explosion, has been shown by EMG data by Elliot, Wilson & Kerr (1989) and Sandler (1992), that tricep & deltoid force EMG patterns began to weaken just shortly after the initial burst of force output (at the chest). This occurred generally about 4in - 6in off the chest. Furthermore Lander et. al. (1985) states "a failed lift is likely to occur if an insufficient impulse is supplied during the acceleration phase or if strength in the mid range is insufficient to overcome the deficit in the sticking region." That is to say that if not enough force is produced at the chest to move the weight through the sticking region, that a lifter will fail his attempt at this point. Note this doesn't necessarily have bearing on the lockout phase of the lift! Also it is important to say that the above statement has not been proven in every instance. It has been proven as OFTEN the reason why, and my test subjects also proved this point, but there is not enough evidence to support this entirely! Finally, Elliot, Wilson & Kerr (1989) and Sandler (1992) found that as load increased, the lifters attempted to use more triceps and deltoids to overcome this area. Basically, there were many forces that appeared to be counteracting productivity, and the deltoid and tricep began firing eractically, probably due to loss of control. In summary, I found that my results(in the sticking region) were very similar to others who have tested this before. There is definitely a sticking area, and simple biomechanics can show all the different forces acting on the joint. Also, due to the nature of the joint, it is more likely to incur a sticking point when trying resolve the arc motion to a linear movement. However, force production is greater following a linear path. Lastly, due to the mechanical leverage of the joints, and angle at which the various shoulder muscles act on the joint will cause a sticking point at some point. There are many theories on training the sticking region, and further research is definitely necessary, however, like any movement, training will improve the performance at this segment which in turn will increase the performance of the entire lift. >From research and testing I have found the best way to ATTEMPT to overcome the sticking region is to work on the explosive start and let momentum overcome this area along with continued acceleration, to prevent the deceleration to occur from any other means other than gravity. Remember this has theory has not been substantiated with enough evidence (although evidence is mounting) and therefore can only be considered an argument. Hope that explained something. If it is too complicated for some, you can email me directly and I can try to shed some light in a different format. Also comments from others who may have ideas, proof or even speculation are very welcomed: of course so are flames :) David Sandler dsandler@ix.netcom.com References (abreiviated for space but I will send full references if anyone is upset): Elliot, Wilson & Kerr " A biomechanical analysis of the sticking region in the bench press". Medicine & Science in Sport & Exercise Vol.21, No.4, pp450 -462 (1989) Lander, Bates, Sawhill, and Hamil "A comparison between free weight & isokinetic bench pressing". Med & Sci.... Vol.17, no.3,pp344-353 (1985) Madsen & McLaughlin "Kinematic factors influencing performance & injury risk in the bench press exercise". Med & Sci...vol.16, no.4, pp376-381 (1984) Zuckerman & Madsen " Biomechanics of the shoulder". pp225-248 from chapter 12 of: Nordin & Frankel, eds. Basic Biomechanics of Musculosketal System. 2nd ed. Phil: Lea & Febiger (1989) ------------------------------