A measuring device for monitoring a posture and/or a performance of a cyclist during pedalling, comprising: at least a support structure configured such as to support a frame of a bicycle of a type comprising: ∘ at least a main body extending along a prevalent development plane; ∘ at least a front fork connected to the main body and exhibiting an engaging portion configured such as to constrain a hub of a wheel; ∘ at least a rear fork connected to the main body and exhibiting an engaging portion configured such as to constrain a hub of a wheel; ∘ at least a saddle connected to the main body and predisposed to enable a cyclist to sit; ∘ at least a handlebar connected to the main body and to the front fork, the handlebar being configured to enable the cyclist to move the front fork and consequently adjust the manoeuvrability of the bicycle; ∘ a first and a second pedal (10; 11) connected to the main body and configured to enable, following application of a torque force thereon, rotation of a wheel connected to the rear fork; said support structure comprising: ∘ at least a base adapted to enable the support structure to lean on a ground surface; ∘ at least a first constraining portion connected to the base and exhibiting an engaging portion able to connect to the engaging portion of the front fork of a bicycle; ∘ at least a mechanism predisposed to receive the torque transmitted on the first and second pedal (10, 11); ∘ at least a power sensor connected to the mechanism and configured such as to generate a signal relating at least to the torque reaching said mechanism and transmitted from said first and second pedal (10, 11); ∘ at least a control unit connected to the power sensor and configured such as: ∘ to receive the signal from the first sensor; ∘ to process the signal to enable to define at least the power dispensed by the pedalling of the cyclist; wherein the first constraining portion of the support structure comprises at least a connecting element engaged to the base and configured such as to define, between the base and the first constraining portion, a hinge-type constraint; characterised in that the support structure comprises: at least a second constraining portion connected to the base and exhibiting an engaging portion able to connect to the engaging portion of the rear fork of a bicycle; wherein the second constraining portion of the support structure comprises at least a connecting element engaged to the fixed body and configured such as to define between the support structure and the second constraining portion a hinge-type constraint; and in that the connecting element of the first constraining portion comprises a spherical joint predisposed such as to enable any type of relative rotation between the portion and the base and the connecting element of the second constraining portion comprises a spherical joint predisposed to allow any type of relative rotation between the portion and the base. at least a support structure configured such as to support a frame of a bicycle of a type comprising: ∘ at least a main body extending along a prevalent development plane; ∘ at least a front fork connected to the main body and exhibiting an engaging portion configured such as to constrain a hub of a wheel; ∘ at least a rear fork connected to the main body and exhibiting an engaging portion configured such as to constrain a hub of a wheel; ∘ at least a saddle connected to the main body and predisposed to enable a cyclist to sit; ∘ at least a handlebar connected to the main body and to the front fork, the handlebar being configured to enable the cyclist to move the front fork and consequently adjust the manoeuvrability of the bicycle; ∘ a first and a second pedal (10; 11) connected to the main body and configured to enable, following application of a torque force thereon, rotation of a wheel connected to the rear fork; ∘ at least a main body extending along a prevalent development plane; ∘ at least a front fork connected to the main body and exhibiting an engaging portion configured such as to constrain a hub of a wheel; ∘ at least a rear fork connected to the main body and exhibiting an engaging portion configured such as to constrain a hub of a wheel; ∘ at least a saddle connected to the main body and predisposed to enable a cyclist to sit; ∘ at least a handlebar connected to the main body and to the front fork, the handlebar being configured to enable the cyclist to move the front fork and consequently adjust the manoeuvrability of the bicycle; ∘ a first and a second pedal (10; 11) connected to the main body and configured to enable, following application of a torque force thereon, rotation of a wheel connected to the rear fork; ∘ at least a base adapted to enable the support structure to lean on a ground surface; ∘ at least a first constraining portion connected to the base and exhibiting an engaging portion able to connect to the engaging portion of the front fork of a bicycle; ∘ at least a mechanism predisposed to receive the torque transmitted on the first and second pedal (10, 11); ∘ at least a power sensor connected to the mechanism and configured such as to generate a signal relating at least to the torque reaching said mechanism and transmitted from said first and second pedal (10, 11); ∘ at least a control unit connected to the power sensor and configured such as: ∘ to receive the signal from the first sensor; ∘ to process the signal to enable to define at least the power dispensed by the pedalling of the cyclist; ∘ to receive the signal from the first sensor; ∘ to process the signal to enable to define at least the power dispensed by the pedalling of the cyclist;