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  • vmax of human muscle

    Wednesday, October 27, 2010, 4:59 PM

    hi everybody,

    in an attenmpt to estimate the maximum power muscle fibers of the
    human gastrocnemius and soleus are capable of, I came across a paper
    by bottinelli, where the vmax is denoted with values between 0.3 and
    1.2 L/s depending on fiber type. this seems quite in contrast with the
    generally assumed 6-16 L/s for skeletal muscle of vertebrates.
    also, the curvature of between 0.03 and 0.07 is almost one magnitude
    smaller than the generally assumed 0.25.
    is there something that I'm missing? I'm quite new to the field of
    muscle...

    comments are much appreciated.
    I'll be happy to submit a summary of all responses to the list.

    thanks a lot and have a great day,
    suzi lipfert


    reference:

    Bottinelli, R., Canepari, M., Pellegrino, M. A., Reggiani, C.,
    1996. Force-velocity properties of human skeletal muscle
    fibres: myosin heavy chain isoform and temperature de-
    pendence. J Physiol 495 ( Pt 2), 57386.


    ____________________________
    S u s a n n e L i p f e r t
    Lauflabor Locomotion Lab
    Friedrich Schiller University
    Jena, Germany
    +49 (0) 3641-945-746
    s.lipf@uni-jena.de
    www.lauflabor.de

  • #2
    summary: vmax of human muscle

    Friday, October 29, 2010, 11:22 AM

    thank you biomch-lers!

    here is the summary of relpies to my post regarding vmax and curvature
    of human skeletal muscle.
    I was wondering where the significant differences of values reported
    in the literature come from.

    first of all, and not surprisingly, it is very difficult to measure
    muscle parameters from intact human muscle other than using cadavers
    or ultrasound.
    second, for data available in the literature, one has to note the
    temperature at which measurements were taken and account for the
    thermal dependence of contraction speed.
    there are countless other points to note and account for, e.g. the
    used fiber preparations, modified hill functions or compensation
    errors in muscle models.


    I found reading these two papers very revealing:

    Bennett, A. F. (1984). Thermal dependence of muscle function. Am J
    Physiol 247, R217-229.

    Domire, Z. J. and Challis, J. H. (2010). A critical examination of the
    maximum velocity of shortening used in simulation models of human
    movement. Computer Methods in Biomechanics and Biomedical Engineering.


    a selection of replies are attached below.

    thanks again for your valuable help!
    cheers
    suzi :-)
    ____________________________
    S u s a n n e L i p f e r t
    Locomotion Lab
    University of Jena, Germany
    +49 (0) 3641-945-734/9 (desk/lab)
    s.lipf@uni-jena.de
    www.lauflabor.de


    --------------------------- Henry Astley ------------------------------

    As far as Vmax goes, the paper states the fibers are at 12C, far below
    human operating temperature of 37C (probably to prevent them from
    breaking down too rapidly). Using a ballpark estimate of 2 for Q10,
    that means a fiber operating at 1.2 L/s at 12C would be shortening at
    6.8 L/s at 37C. A higher Q10 would mean an even bigger increase with
    temperature, with the appropriate caveat that Q10 tends to level off
    near an organism's preferred operating temperature.

    Henry Astley

    -----------------------------------------------------------------------

    --------------------------- Daniel Hahn -------------------------------

    I think you should be very carefully when trying to estimate maximum
    power output of a human muscle, especially when activated voluntarily.
    However, it is not clear what kind of data you have. You are talking
    about muscle fibres, so is your data based on isolated muscle fibre
    experiments or do you like to estimate power output for intact
    muscle-tendon units in humans during naturally movements (where you
    only can asses muscle fascicles by ultrasound but not fibres)?
    To my knowledge, unfortunately there is no measurement of vmax of
    muscle fascicles for an intact in vivo human muscle. Moreover you
    should be aware that curvature of F-v curves changes depending several
    factors like e.g. muscle length and activation level. Thus, in my
    opinion Hills constant a can't be assumed to have a fix value (0.25).
    Moreover, already 1964 Hill himself modified his hyperbolic function
    by replacing constant a by the function a = 0.16F0 + 0.18F, with
    F0=maximum force and F=force at a given velocity. (However, I do not
    know why people usually do not use it, perhaps due to the simplicity
    of the original Hill-function).

    Cheers
    Daniel

    Hill AV. The Effect of Load on the Heat of Shortening of Muscle. Proc
    R Soc Lond B Biol Sci 159: 297-318, 1964.

    -----------------------------------------------------------------------

    --------------------------- Glen Lichtwark ----------------------------

    Two very important things to note about Bottinelli's data -

    1. These experiments are performed on skin fibre preparations, which
    don't always scale particularly well to the whole muscle level
    2. The experiments are performed at low temperatures - typically 10-15
    degrees. The lower the temperature the slower the peak contraction
    speed. You can estimate the Vmax from the known Q10 of approximately
    2-2.5 (Bennett, 1984). If we assume a Vmax of 0.8 measured at 12 deg
    we can work out the Vmax at 37 degrees.

    Q10 = (R2/R1)^[10/(T2-T1)]

    Rearranging - R2 = (Q10^(1/[10/(T2-T1)]))*R1

    Substitute values - Q10 = 2.5, R1 = 0.8, T2 = 37, T1 = 12
    R2 = 7.9 Lo/s

    Vmax of 7.9 Lo/s. This goes down to 4.5 Lo/s if we use a Q10 = 2.

    Q10 values are reported in Bottinelli's papers, however not for Vmax.
    I also think the values reported a little high compared to intact
    fibres.

    I hope this helps,

    Glen

    -----------------------------------------------------------------------

    --------------------------- At Hof ------------------------------------

    I have not read yet the Bottinelli paper, but I am afraid that their
    results must be incorrect. I was involved with the work of Van
    Zandwijk (1998, Biol Cybern 79:121-130) and still am convinced of the
    valid results. They give a = 0.13 - 0.30 and b = a.vmax = 1.4-3.0 rad
    /s = = 1.75 - 3.7 L/s for soleus. (This gives vmax around 12 L/s. )The
    parameter b = n.vmax is the most important for modeling. To measure
    maximum speed vmax, and thus n = b/vmax is very difficult for human
    muscles in ergometers. These values are in agreement with most other
    work that I know of, but you may be more familiar with recent work
    than I am. The values of Bottinelli are indeed incredibly low. Vmax =
    0.3 L/s and n = 0.03 would lead to a time constant for the isometric
    force of some 30 seconds, instead of 0.3 s.
    Success with your inquiry,

    At Hof

    -----------------------------------------------------------------------

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