sticking point...
passt vielleicht zum thema:
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 <dsandler@ix.netcom.com>
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)
