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Dear Colleagues,
I would like to immediately respond to the posting of Dr. Tashman
because I feel that his most impressive and to-the-point description of
the current situation in clinical gait analysis deserves special
attention.
Here are my (brief) comments:
1. The "holy grail" of clinical gait analysis (use of
neuromusculoskeletal system models in conjunction with optimization
techniques for designing individualized optimal treatment strategies for
various populations of patients with neuromuscular disorders) does not
have to remain a distant dream. Already in 1975, I performed the first
complete, and experimentally verified, optimization of a human motion
(Hatze, H. (1976) The complete optimization of a human motion. Mathem.
Biosciences 28, 99-135) after being told by everyone that this would be
impossible at the present (1975) state of the art. I used a (then)
rather complex neuromusculoskeletal system model of the leg, devised new
methods for parameter identification to individualize the model, and
successfully solved the optimal control problem. The optimal solution of
the (time-optimal) kicking motion was verified by training the subject
for optimal performance. Prior to this it was ascertained that the
subject was unable to find the optimum himself within a reasonable
period of time. (I did not want to mention this project in my previous
posting to avoid giving the impression of advertising my work in this
discussion forum).
I am convinced that by using more sophisticated models and techniques,
the "holy grail" of clinical gait analysis can also become reality in a
concerted effort of several high-level research institutions combined,
for instance, in a biomechanics network.
2. I am glad Dr. Tashman underlined the importance of understanding the
performance criteria underlying the execution of a given task. (Not too
many researchers recognize this importance). This will be one of the
discussion topics to come.
3. His remark that neuromuscular disorders alter essentially all aspects
of the motor control system is very much to the point and highlights the
significance of a generally neglected phenomenon.
4. It is also true, and highly significant, that properties of tissue
determined in vitro must not (and generally do not) conform to tissue
properties in vivo. (This is why in my models, the values of the
relevant parameters are always determined by noninvasive experimental
in-vivo methods, knowing that these parameter values are VALID FOR A
VERY LIMITED TIME PERIOD ONLY).
5. An excellent remark of Dr. Tashman concerns the whole problem of
biological adaption of tissue after translocations. This issue is
frequently ignored despite its importance. It certainly has to be
considered in advanced modeling.
I cordially thank Dr. Tashman for his excellent and detailed
contribution, and for his positive and progressive opinion on the
subject.
Herbert Hatze
************************************************** ******
Prof. Dr. Herbert Hatze
Head, Department and Laboratory of Biomechanics, ISW,
University of Vienna
Auf der Schmelz 6 Tel: + 43 1 4277 48880
A-1150 WIEN Fax: + 43 1 4277 48889
AUSTRIA e-mail: herbert.hatze@univie.ac.at
************************************************** ******
---------------------------------------------------------------
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For information and archives: http://isb.ri.ccf.org/biomch-l
---------------------------------------------------------------
I would like to immediately respond to the posting of Dr. Tashman
because I feel that his most impressive and to-the-point description of
the current situation in clinical gait analysis deserves special
attention.
Here are my (brief) comments:
1. The "holy grail" of clinical gait analysis (use of
neuromusculoskeletal system models in conjunction with optimization
techniques for designing individualized optimal treatment strategies for
various populations of patients with neuromuscular disorders) does not
have to remain a distant dream. Already in 1975, I performed the first
complete, and experimentally verified, optimization of a human motion
(Hatze, H. (1976) The complete optimization of a human motion. Mathem.
Biosciences 28, 99-135) after being told by everyone that this would be
impossible at the present (1975) state of the art. I used a (then)
rather complex neuromusculoskeletal system model of the leg, devised new
methods for parameter identification to individualize the model, and
successfully solved the optimal control problem. The optimal solution of
the (time-optimal) kicking motion was verified by training the subject
for optimal performance. Prior to this it was ascertained that the
subject was unable to find the optimum himself within a reasonable
period of time. (I did not want to mention this project in my previous
posting to avoid giving the impression of advertising my work in this
discussion forum).
I am convinced that by using more sophisticated models and techniques,
the "holy grail" of clinical gait analysis can also become reality in a
concerted effort of several high-level research institutions combined,
for instance, in a biomechanics network.
2. I am glad Dr. Tashman underlined the importance of understanding the
performance criteria underlying the execution of a given task. (Not too
many researchers recognize this importance). This will be one of the
discussion topics to come.
3. His remark that neuromuscular disorders alter essentially all aspects
of the motor control system is very much to the point and highlights the
significance of a generally neglected phenomenon.
4. It is also true, and highly significant, that properties of tissue
determined in vitro must not (and generally do not) conform to tissue
properties in vivo. (This is why in my models, the values of the
relevant parameters are always determined by noninvasive experimental
in-vivo methods, knowing that these parameter values are VALID FOR A
VERY LIMITED TIME PERIOD ONLY).
5. An excellent remark of Dr. Tashman concerns the whole problem of
biological adaption of tissue after translocations. This issue is
frequently ignored despite its importance. It certainly has to be
considered in advanced modeling.
I cordially thank Dr. Tashman for his excellent and detailed
contribution, and for his positive and progressive opinion on the
subject.
Herbert Hatze
************************************************** ******
Prof. Dr. Herbert Hatze
Head, Department and Laboratory of Biomechanics, ISW,
University of Vienna
Auf der Schmelz 6 Tel: + 43 1 4277 48880
A-1150 WIEN Fax: + 43 1 4277 48889
AUSTRIA e-mail: herbert.hatze@univie.ac.at
************************************************** ******
---------------------------------------------------------------
To unsubscribe send SIGNOFF BIOMCH-L to LISTSERV@nic.surfnet.nl
For information and archives: http://isb.ri.ccf.org/biomch-l
---------------------------------------------------------------