A computer-implemented method of determining a value of one or more parameters of a respiratory effort of a subject, the method comprising: obtaining a thoracic signal, the thoracic signal being an indicator of a thoracic component of the respiratory effort, the thoracic signal being a thoracic respiratory inductive plethysmograph signal; obtaining an abdomen signal, the abdomen signal being an indicator of an abdominal component of the respiratory effort, the abdomen signal being an abdomen respiratory inductive plethysmograph signal; and determining the value of the one or more parameters of the respiratory effort by using a model of a respiratory system of the subject, the model including a plurality of components, each of the plurality of components of the model being used to represent parts of the respiratory system of the subject, setting or using constraints and/or relationships of the plurality of components of the model of the respiratory system of the subject, and fitting the components of the model of the respiratory system of the subject with data from the obtained thoracic signal and data from the obtained abdomen signal, wherein the one or more parameters include one or more of: an airway resistance Rr of the subject, an intercostal muscle drive force FTm, a diaphragm drive force FAm, an intrathoracic pressure PIt, respiratory drive, a thoracic negative pressure force FTp, and an abdomen negative pressure force FAp, and wherein the value of the one or more parameters of the respiratory effort are determined based on adjusting the plurality of components of the model of the respiratory system without directly measuring the value of the one or more parameters of the respiratory effort. obtaining a thoracic signal, the thoracic signal being an indicator of a thoracic component of the respiratory effort, the thoracic signal being a thoracic respiratory inductive plethysmograph signal; obtaining an abdomen signal, the abdomen signal being an indicator of an abdominal component of the respiratory effort, the abdomen signal being an abdomen respiratory inductive plethysmograph signal; and determining the value of the one or more parameters of the respiratory effort by using a model of a respiratory system of the subject, the model including a plurality of components, each of the plurality of components of the model being used to represent parts of the respiratory system of the subject, setting or using constraints and/or relationships of the plurality of components of the model of the respiratory system of the subject, and fitting the components of the model of the respiratory system of the subject with data from the obtained thoracic signal and data from the obtained abdomen signal, using a model of a respiratory system of the subject, the model including a plurality of components, each of the plurality of components of the model being used to represent parts of the respiratory system of the subject, setting or using constraints and/or relationships of the plurality of components of the model of the respiratory system of the subject, and fitting the components of the model of the respiratory system of the subject with data from the obtained thoracic signal and data from the obtained abdomen signal, wherein the one or more parameters include one or more of: an airway resistance Rr of the subject, an intercostal muscle drive force FTm, a diaphragm drive force FAm, an intrathoracic pressure PIt, respiratory drive, a thoracic negative pressure force FTp, and an abdomen negative pressure force FAp, and an airway resistance Rr of the subject, an intercostal muscle drive force FTm, a diaphragm drive force FAm, an intrathoracic pressure PIt, respiratory drive, a thoracic negative pressure force FTp, and an abdomen negative pressure force FAp, and wherein the value of the one or more parameters of the respiratory effort are determined based on adjusting the plurality of components of the model of the respiratory system without directly measuring the value of the one or more parameters of the respiratory effort.