View Single Post
Old 02-22-2013, 07:32 AM   #118
Hall Of Fame
Join Date: Dec 2006
Location: Bedford,Massachusetts,US
Posts: 3,131
Default 500 fps

The one I saw are 500 fps
At some moment (very close to contact) the BOTTOM hand is straight.
It is a DIFFERENT model that SOME SHOTS by Agassi
It is complicated because:
on ONE HAND (pun attempted) one would like to have a hand straight
(after coming OUT of THE FLIP but very close to the CONTACT).
So we would like to employ SSC of biceps here
Some references related to SSC below
PS #1
J Appl Physiol. 1999 May;86(5):1445-57.
Length dependence of active force production in skeletal muscle.
Rassier DE, MacIntosh BR, Herzog W.

Human Performance Laboratory, Faculty of Kinesiology, The University of Calgary, Calgary, Alberta, Canada T2N 1N4.

The sliding filament and cross-bridge theories of muscle contraction provide discrete predictions of the tetanic force-length relationship of skeletal muscle that have been tested experimentally. The active force generated by a maximally activated single fiber (with sarcomere length control) is maximal when the filament overlap is optimized and is proportionally decreased when overlap is diminished. The force-length relationship is a static property of skeletal muscle and, therefore, it does not predict the consequences of dynamic contractions. Changes in sarcomere length during muscle contraction result in modulation of the active force that is not necessarily predicted by the cross-bridge theory. The results of in vivo studies of the force-length relationship suggest that muscles that operate on the ascending limb of the force-length relationship typically function in stretch-shortening cycle contractions, and muscles that operate on the descending limb typically function in shorten-stretch cycle contractions. The joint moments produced by a muscle depend on the moment arm and the sarcomere length of the muscle. Moment arm magnitude also affects the excursion (length change) of a muscle for a given change in joint angle, and the number of sarcomeres arranged in series within a muscle fiber determines the sarcomere length change associated with a given excursion.

PS #2
J Biomech. 2003 Sep;36(9):1309-16.
Stretch-induced, steady-state force enhancement in single skeletal muscle fibers exceeds the isometric force at optimum fiber length.
Rassier DE, Herzog W, Wakeling J, Syme DA.

Faculty of Kinesiology, Human Performance Laboratory, University of Calgary, 2500, University Dr. N.W Calgary, AB T2N 1N4, Calgary, Canada.

Stretch-induced force enhancement has been observed in a variety of muscle preparations and on structural levels ranging from single fibers to in vivo human muscles. It is a well-accepted property of skeletal muscle. However, the mechanism causing force enhancement has not been elucidated, although the sarcomere-length non-uniformity theory has received wide support. The purpose of this paper was to re-investigate stretch-induced force enhancement in frog single fibers by testing specific hypotheses arising from the sarcomere-length non-uniformity theory. Single fibers dissected from frog tibialis anterior (TA) and lumbricals (n=12 and 22, respectively) were mounted in an experimental chamber with physiological Ringer's solution (pH=7.5) between a force transducer and a servomotor length controller. The tetantic force-length relationship was determined. Isometric reference forces were determined at optimum length (corresponding to the maximal, active, isometric force), and at the initial and final lengths of the stretch experiments. Stretch experiments were performed on the descending limb of the force-length relationship after maximal tetanic force was reached. Stretches of 2.5-10% (TA) and 5-15% lumbricals of fiber length were performed at 0.1-1.5 fiber lengths/s. The stretch-induced, steady-state, active isometric force was always equal or greater than the purely isometric force at the muscle length from which the stretch was initiated. Moreover, for stretches of 5% fiber length or greater, and initiated near the optimum length of the fiber, the stretch-enhanced active force always exceeded the maximal active isometric force at optimum length. Finally, we observed a stretch-induced enhancement of passive force. We conclude from these results that the sarcomere length non-uniformity theory alone cannot explain the observed force enhancement, and that part of the force enhancement is associated with a passive force that is substantially greater after active compared to passive muscle stretch.

Last edited by julian; 02-22-2013 at 08:05 AM.
julian is offline   Reply With Quote