Application of a force-velocity-endurance model to in situ muscle evaluation in mouse model.
Résumé
Introduction. The muscular contractile capacity is essential for human and animal movement and locomotion.
Owing to their molecular structure, striated skeletal muscle cells produce a force that is a function of
their rate of shortening. When the force production capacity of the neuromuscular system on an isolated muscle
is explored, this relationship can be formulated mathematically by a rational function F(V ) [1]. Moreover, the
intensity of this force decreases as a function of the duration F(t), and converges towards a characteristic critical
intensity [2]. The interaction between these two fundamental relationships has been studied only through
independent comparisons. Considering them as two projections of a single force-velocity-time relationship [3]
would make it possible to describe the force production capacities and their interactions in their entirety. The
aim of this conceptual framework is to use an integrative model to unify a new Force-Velocity-Endurance (FVE)
relationship that can define muscle properties and fatigability.
Methods. This new theoretical framework proposes a model that is a function of two variables (time t and
velocity V ), and seven major parameters to describe muscle properties: initial fatigue-free capacities (initial
force (F0i ), initial velocity (V0i ), initial curvature (Ci) coefficients), critical capacities (F0c , V0c , Cc) and a
characteristic time τ corresponding to the rate of capacity decline. To measure these parameters, a new 3 min
all-out test with velocity variation was developed on an isokinetic ergometer (Aurora Scientific 300C) to scan
the maximum capacities of the FVE surface, on both the velocity and time dimensions. The model was tested
on 12 wild-type mice (six males and sixfemales) for the tibialis anterior (TA) and gastrocnemius (GA) muscles.
Results and discussion. The goodness of fit of the model from the experimental data was excellent for all
muscles (r² > 0.97). The proposed model revealed significant differences between the TA and GA muscle groups.
For males, F0i , F0c and τ were higher for GA compared to TA. Considering females, F0i was significantly higher
for GA but relative F0c was higher for TA. This new model also revealed differences in the muscle capacity as
a function of sexual dimorphism. For instance, F0i was sgnificanlty higher for males compared to female only
for TA but not GA muscles.
Conclusions and perspectives. These results demonstrate that it is possible to determine the individual
parameters of the proposed model (F0i , V0i , Ci, F0c , V0c , Cc and τ ) from the experimental data obtained from
the proposed all-out test. Validating the existence of a universal FVE relationship and its theoretical foundations
would open a new conceptual framework for improving our understanding of muscle function. Although this
project is fundamental, the practical applications resulting from this new framework could be numerous, such
as functional analysis of gene therapy in myology or the impairment of neuromuscular function in patients.
Domaines
Sciences du Vivant [q-bio]Origine | Fichiers produits par l'(les) auteur(s) |
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