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Re: Re: kinetic chain...jack, your view, please

Posted by: SteveT () on Wed Jul 26 09:23:48 2000

It is not necessary to subscribe to linear mechanics to accept that the kinetic chain is at work. It is involved in virtually all high-speed sporting events from the pole vault, to throwing, to golf, etc. It is merely the sequential contraction of progressively smaller muscles. Here is the absract of a study which shows the sequence I'm referring to:

Clin Orthop 1993 Jul;(292):285-93
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Baseball batting. An electromyographic study.

Shaffer B, Jobe FW, Pink M, Perry J

Department of Orthopaedics, Georgetown Medical Center, Washington, D.C.

The muscle firing pattern in 12 muscles throughout the lower extremity, trunk, and upper extremity during the
batting swing is described in this study. The two hamstring muscles studied and the gluteal muscle had a similar
pattern of high muscle activity during pre-swing and early swing, and then rapidly diminished. The vastus medialis
demonstrated peak activity between 95 and 110% maximum muscle test (MMT) throughout the swing phases and
follow-through. The erector spinae demonstrated activity from 85 to 185% MMT during the swing phases. The
abdominal obliques showed greater than 100% MMT during the swing phases and follow-through. The
supraspinatus and serratus anterior showed relatively low muscle activity (less than 40% MMT). These results
show that batting is a sequence of coordinated muscle activity, beginning with the hip, followed by the trunk, and
terminating with the arms. Power in the swing is initiated in the hip, and therefore exercises that emphasize such
strength development are indicated. The maintained, high muscle activity in the trunk muscles indicates a need for
back and abdominal stabilization and rotation exercises. The relatively low level of activity in the four
scapulohumeral muscles tested indicated that emphasis should be placed on the trunk and hip muscles for a
batter's strengthening program.


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