Patent Application
20230157581
The present invention relates to a method of, and a device for characterizing the metabolic response of a subject or an individual to exercise.
State of the Art
The study of the response to exercise is an old subject covering many fields of researches, from physiology, and more specifically sports physiology, to biomechanics.
Energy expenditure has been known and studied since the end of the 19th century, including from a thermodynamic point of view via a calorimetric approach, and then a metabolic and nutritional approach.
Studies on ventilation and ventilatory adaptation are also widespread and are integrated into exercise testing.
The book by the authors Monod, Flandrois, and Vandewalle (Physiologie du sport 6th edition Masson (2007)), makes an exhaustive review of these issues for the humans. Equivalent review can be found, for example, for the horse, in the book “The Athletic Horse, Principles and Practice of Equine Sports Medicine”, edited by David R. Hodgson, Kenneth Harrington McKeever and Catherine M. McGowan.
To date, there is no single protocol for obtaining this characterization directly. The existing measurements and protocols are carried out separately and do not allow a synthetic mapping of the response to exercise of an individual or a subject. It should be noted that the main protocols for identifying an individual's energy potential are based on the following measurements requiring specific equipment:
Moreover, producing a synthetic mapping is only accessible at the cost of multiple protocols on different equipment,
In addition, the publication (Goupil et al. 2019. New J. Phys. 21, 023021 “Thermodynamics of metabolic energy conversion under muscle load”) builds the thermodynamic foundation for the response of a muscle, or a set of muscles, under stress.
It demonstrates that two metabolic parameters can be estimated on the basis of the classical measurement of the force-movement speed response of the muscle: the isometric force Fiso, on the one hand, and a feedback resistance, Rfb, on the other hand.
One purpose of the invention is to allow the quantification of the health condition and performance in terms of energetic potential of an individual from an experimental protocol comprised of two tests. The key innovative character of this invention emerges from the thermodynamic description of the response to exercise, that provide the possibility to bring together the results of these tests in a single descriptive framework.
The method and device of the invention allow for the mapping of a subject's performance and energetic potential in a single test protocol by directly identifying muscular response coupled with ventilatory response of the subject.
To date, there is no single protocol for obtaining this characterization directly. The existing measurements and protocols are carried out separately and do not allow a synthetic mapping of the response to exercise of an individual or a subject.
At the end of the proposed protocol carried out with the device, the synthetic mapping involves 5 traits that are easily calculated:
All these parameters together give value of metabolic merit factor, Fm=(Fiso Rfb IT)/(B RM), which is the main indicator of the individual's potentiality.
As such, the proposed device can be used both for monitoring sports performance and for functional rehabilitation.
More specifically, the present invention presents a method of determining metabolic parameters of one or several muscle motor units of any subject by coupling muscle response with ventilatory response of the subject.
Comprising the following steps:
the COT curve being coupled to the muscle response by the following equation:
with B the basal power of one or several muscle motor units
RM the flow resistance of one or several muscle motor units
Indeed, the COT curve has a vertical asymptote at the origin and an oblique asymptote also called the oblique asymptote at high intensities. Alternatively, the step of acquiring a movement speed value of one or several muscular motor units of a subject v(t) and an oxygen flow rate value φO2(t) can be replaced by a step of performing exercise (i) using a test device and a step of instantaneously measuring (ii) the movement speed of one or several muscular motor units of the subject v(t) and the oxygen flow rate φO2(t). Alternatively, the step of acquiring may be preceded by a step of instantaneously measuring the movement speed of one or several muscle motor units of the subject v(t), and of the oxygen flow rate φO2(t) of the subject. In addition, these values can be measured instantaneously during the performance of exercise by the subject performing an exercise test or a stress test on a test device.
governed by the following equation from Hill's muscle model:
(F+a) (v+b)=c
Alternatively, the step of instantaneously measuring (ii) the movement speed of one or more muscular motor units of the subject v(t), and of the oxygen flow rate φO2(t) may be completed by a step of acquiring a value of developed power P(t) and/or force F(t).
The organism being represented by the isometric force and the resistance impedance of the organism such that:
F(p)=Fiso*Z(p)/(ZIM(p)+Z(p))
V(p)=Fiso/(ZIM(p)+Z(p))
Alternatively, the step of acquisition as a function of time may correspond to or be preceded by a step of performing exercise, with the subject moving and being subjected to a variable load which is an instantaneous time-modulated load, as well as to a step of instantaneous measurement, measuring the movement speed of one or several assemblies of muscular motor units, of the developed power or force and of the oxygen flow.
R
in
=R
M
+R
fb
=R
M+(Fiso+a0)/(vT+v),
the measured values being the mechanical force FM and the movement speed v, and
with the force Fiso=FB constant, Rin is determined by modulating a load RL (imposed effort)
According to another embodiment, the invention relates to a device for determining metabolic parameters of one or several muscle motor units coupling muscle response to ventilatory response of a subject, comprising:
the COT curve being coupled to the muscle response by the following equation:
with B the basal power of one or several muscle motor units;
RM the flow resistance of one or several muscle motor units;
the processor being configured to determine the following metabolic parameters from the COT curve:
According to other optional features of the device:
(F+a) (v+b)=c
F(p)=Fiso*Z(p)/(ZIM(p)+Z(p))
V(p)=Fiso/(ZIM(p)+Z(p))
Other objectives, features and advantages become apparent from the following detailed description with reference to the drawings given for illustrative and non-exhaustive purposes:
The present invention relates to the determination of intrinsic and extrinsic metabolic parameters of one or several muscular motor units consisting of one or several muscles defining an identity card of a subject's physical condition. The determination is based on:
Each muscular motor unit thus consists of a muscle, and the metabolic parameters are generally determined on several motor units considered.
Preferably, the method according to the invention is implemented by at least one computing means 3, such as a processor 3 associated with a memory. With the one or more processors being adapted to, preferably configured to plot a COT curve :the subject's oxygen flow rate against the subject's movement speed v(t), and to determine metabolic parameters from the curve. In addition, the one or more processors are capable of, preferably configured to execute the various steps of a method according to the invention.
Furthermore, by “means for acquiring” 2a & 2b, is meant, within the meaning of the invention, a test device 1 and/or measurement means. The terms “subject” and “individual” in the present invention, refer to humans but also to any animal species, domestic or wild. In the present invention, the terms “subject” and “individual” are used without distinction.
The core of the modeling is based on metabolic power production by a body (or an organism) and is derived from the publication (Christophe Goupil et al. 2019 New J. Phys. 21, 023021 “Thermodynamics of metabolic energy conversion under muscle load”).
A metabolic power can be broken down into a metabolic force and a metabolic intensity, the product of which gives the metabolic power.
It is considered that the metabolic power is transmitted, via the limbs, in the form of mechanical power and movement speed which are the quantities actually measured experimentally.
The thermodynamic model developed is in perfect agreement with Hill's phenomenological modeling, for which it provides the thermodynamic foundations.
Metabolic power production results from the difference in input, Φ+, and output, Φ−, powers of the organism.
Φ+ corresponds to nutrient supply (mainly glucose), while Φ− is a waste stream that includes excess heat and especially the production of lactic acid-like reaction metabolites.
The point is key, because it follows that the flow Φ− can be considered, to a large extent, proportional to the flow of oxygen consumed by the organism.
The theoretical model leads to the following expressions:
With:
These concepts were introduced in the publication (Christophe Goupil et al. 2019 New J. Phys.21 023021 “Thermodynamics of metabolic energy conversion under muscle load”).
The metabolic power results from the difference between the input and the output powers, and is written:
The metabolic power involves two additional terms compared to the previous ones, they are RM and Rfb, with:
The five-parameter parameterization thus contains both metabolic (IT, B) and mechanical (Fiso,RM) parameters. As regards the term Rfb, it has a metabolic origin but it translates mechanically.
All the parameters can be combined into a metabolic merit factor which is, in a way, the summary scalar of the subject's health condition,
All the parameters are now established, there remains to specify some relationships and experimental methods.
Hill's Parameterization
As mentioned above, the metabolic model provided the thermodynamic basis for Hill's muscle model.
Hill proposes a phenomenological expression of the force-movement speed response of one or several muscle motor units, according to:
(F+a) (v+b)=c
F mechanical force (measured);
v: movement speed of contraction (measured).
The theoretical model developed resulted in the following correspondences:
a=R
fbIT+RMIM=a0+RMIM≈a0=cte
b=IT=cte
c=(Fiso+RfbIT) IT=cte
The typical force-movement speed response curve can be traced back to the values of the three parameters, since the overall shape is defined by two extreme points, Fiso and the movement speed at zero force.
The characteristic dip of the curve defines IT.
The following parameters are therefore extracted:
Balance of the Parameters
We have five parameters:
And we have a force-movement speed experiment (
There are still two to be determined. This is the role of the COT measurement.
COI and COT
Using the proportion between the oxygen flow rate and ϕ−, the missing terms can be extracted.
The Cost of Oxygen Index (COI) is defined as:
The shape of the plot is shown in
It should be noted that the curve has a vertical asymptote at the origin, and an oblique asymptote at high intensities. These two asymptotes allow the extraction of, respectively:
It should also be noted that that the y-intercept also makes it possible to find Hill's parameter a0. All five parameters characterizing the organism are therefore accessible.
In the case of movement, and using the proportion between IM and movement speed, the oxygen Cost of Transport (COT) can be defined, which is a quantity widely used in the literature.
In fact, from a dimensional point of view, the COT corresponds to the amount of energy waste produced to move body of the subject over a unit length.
Its expression is:
The form of the COT is therefore isomorphic to that of the COI.
Conclusion: by means of an exercise test measuring powers, movement speeds and oxygen flows, it is possible to calculate the five metabolic parameters that define the mapping of a subject's condition and performance. In addition, the merit factor provides a summary of the subject's state.
From an experimental point of view, a treadmill or bicycle type exercise test device 1 should be considered, as shown in
The quantities to be measured will be:
Protocol
Principle
From a practical point of view, the measurements are equivalent to extracting the mechanical output impedance of the organism.
Indeed, the equivalent schematic according to a nodal approach is illustrated in
The actual mechanical power available is at the end of the chain. The power results from the product of the force available at the end of the chain, multiplied by the movement speed of movement of the limbs.
The mechanical output resistance is written
R
in
=R+R
H(v)=RM+(Fiso+a0)/(vT+v)
Knowing that the measured quantities are the mechanical force FM and the movement speed v, on the one hand, and that the force Fiso=FB is constant, on the other hand, the value Rin can be extracted by modulating the load RL. Depending on the type of protocol envisaged, the load may be a braking force that prevents movement, or a mass that opposes movement, as in the case of so-called “leg-press” devices.)
The one skilled in the art will understand that the experimental embodiment can be carried out by means of various devices (treadmill, bicycle, leg press), depending on whether the determination of the metabolic parameters relates to a limb, a portion or all of the organism.
Let us consider the case of a training bike type device, as shown in
The experimental procedure is equivalent to a harmonic load as encountered in impedance spectroscopy measurements. The electrical analog of the mechanical protocol is the impedance spectroscopy technique used in electrochemistry to determine the performance of electric batteries.
The shape of the modulation signals of the load RL can be of different types, following the tradition of impedance spectroscopy analyses:
Thus, at the end of the protocol carried out on the equipment, the synthetic mapping is composed of the following elements:
Measured under stationary stress, these quantities have real values.
On the other hand, when measured under transient stress, the viscosity parameters have an imaginary part which accounts for the elastic and inertial terms.
All of these parameters together are used to obtain the value of the metabolic merit factor, which is the main indicator of the individual's potentiality. As such, the proposed equipment can be used both for monitoring sports performance and for functional rehabilitation. It makes it possible to obtain a synthetic mapping of the response of an individual to exercise, which is not possible to obtain using the state of the art where the measurements and the existing protocols are carried out separately.
As shown in
Individual I1 has a fairly low basal power, high threshold isometric strength and metabolic intensity. These last two quantities show that the individual I1 is capable of subjecting organism of the subject to a significant physical effort. Low basal power of the subject characterizes a dominant of slow type muscles. It is thus an individual adapted to an endurance type effort, rather than an explosive one. The fairly high values of the flow and feedback resistances show that there is room for improvement both physically, through training (lowering of the flow resistance), and possibly metabolically (lowering of the feedback resistance) through better metabolization of nutrients.
Individual I2 has high basal power, low threshold intensity and low isometric strength. The resistances are also of low value. In this case it is about an individual having presumably a very good potential for explosive effort (important Basal), but who is strongly reduced by the weakness of the threshold intensity. This contradiction can be explained by the presence of an injury that does not allow a normally performing body to express its full potential. It can therefore be observed that the collection of the five parameters makes it possible to distinguish between the measured performance and an individual's potentialities.
