A pedal for bicycles comprising: a pedal pin which extends along a reference axis (A) and has a first axial end structured to be coupled to a pedal crank of a bicycle and a second axial end opposite to said first end , a pedal body which comprises a hub coupled in a freely rotatable manner to said pedal pin in order to be able to rotate around said reference axis (A), at least two inner chambers which have a circular section and are formed in said pedal pin and extend along said reference axis coaxial thereto, sensor means coupled to said pedal pin and designed to detect an electric parameter indicative of the mechanical deformation thereof, electronic means which are configured to determine, through said sensor means , the mechanical deformation of the pedal pin caused by the force exerted by the cyclist on the pedal pin during the pedalling, electric storage means which are arranged within at least one of said inner chambers and are designed to electrically power said electronic means , and wherein a first inner chamber is formed in the pedal pin so as to extend along said reference axis (A) starting approximately from the first end towards the second end , a second inner chamber is formed in the pedal pin so as to extend along said reference axis (A) between the first inner chamber and the second end , said second inner chamber being sized so as to have: a length comprised between approximately 15 mm and approximately 40 mm, an internal diameter comprised between approximately 7 mm and approximately 13 mm, and an axial end opposite to the first chamber , which is arranged at a distance of less than approximately 25 mm from said second end of said pedal pin . a pedal pin which extends along a reference axis (A) and has a first axial end structured to be coupled to a pedal crank of a bicycle and a second axial end opposite to said first end , a pedal body which comprises a hub coupled in a freely rotatable manner to said pedal pin in order to be able to rotate around said reference axis (A), at least two inner chambers which have a circular section and are formed in said pedal pin and extend along said reference axis coaxial thereto, sensor means coupled to said pedal pin and designed to detect an electric parameter indicative of the mechanical deformation thereof, electronic means which are configured to determine, through said sensor means , the mechanical deformation of the pedal pin caused by the force exerted by the cyclist on the pedal pin during the pedalling, electric storage means which are arranged within at least one of said inner chambers and are designed to electrically power said electronic means , and wherein a first inner chamber is formed in the pedal pin so as to extend along said reference axis (A) starting approximately from the first end towards the second end , a second inner chamber is formed in the pedal pin so as to extend along said reference axis (A) between the first inner chamber and the second end , a length comprised between approximately 15 mm and approximately 40 mm, an internal diameter comprised between approximately 7 mm and approximately 13 mm, and an axial end opposite to the first chamber , which is arranged at a distance of less than approximately 25 mm from said second end of said pedal pin . <EOS>