A ventilation measurement device, comprising: a fastening mechanism capable of permanently or detachably fastening the ventilation measurement device to a belt which can be worn around a part of a subject's torso that expands as a function of inhalation; a substrate (4, 4', 4") coupled to the fastening mechanism and capable of receiving tensional forces transmitted from the belt through the fastening mechanism; a strain gauge mounted on said substrate and configured to output a signal with a functional relationship with said tensional forces; a controller unit configured to receive and process said signal and produce processed data therefrom; and a transmitter configured to be controlled by said controller to transmit processed data to an external receiver; characterized in that it further comprises a casing; and wherein said fastening mechanism includes two parts, the first of which is attached directly to a first end of said substrate and the second of which is attached either - directly to a second end of said substrate in order to transmit tensional forces directly to the substrate, or - directly to the casing in order to transmit tensional forces to an other end of said substrate, said second end of said substrate being attached directly to the casing; and the attachment of the first part of said fastening mechanism passes through a flexible ring which connects the fastening mechanism to the casing while allowing the first part of the fastening mechanism to move relatively to the casing in order to transmit tensional forces to the substrate. a fastening mechanism capable of permanently or detachably fastening the ventilation measurement device to a belt which can be worn around a part of a subject's torso that expands as a function of inhalation; a substrate (4, 4', 4") coupled to the fastening mechanism and capable of receiving tensional forces transmitted from the belt through the fastening mechanism; a strain gauge mounted on said substrate and configured to output a signal with a functional relationship with said tensional forces; a controller unit configured to receive and process said signal and produce processed data therefrom; and a transmitter configured to be controlled by said controller to transmit processed data to an external receiver; characterized in that it further comprises a casing; and wherein said fastening mechanism includes two parts, the first of which is attached directly to a first end of said substrate and the second of which is attached either - directly to a second end of said substrate in order to transmit tensional forces directly to the substrate, or - directly to the casing in order to transmit tensional forces to an other end of said substrate, said second end of said substrate being attached directly to the casing; and - directly to a second end of said substrate in order to transmit tensional forces directly to the substrate, or - directly to the casing in order to transmit tensional forces to an other end of said substrate, said second end of said substrate being attached directly to the casing; and the attachment of the first part of said fastening mechanism passes through a flexible ring which connects the fastening mechanism to the casing while allowing the first part of the fastening mechanism to move relatively to the casing in order to transmit tensional forces to the substrate.