A sports implement including an electroactive element, such as a piezoceramic sheet attached to the implement and a circuit attached to the electroactive element. The circuit may be a shunt, or may include processing such as amplification and phase control to apply a driving signal which may compensate...http://www.google.fr/patents/US5857694?utm_source=gb-gplus-shareBrevet US5857694 - Adaptive sports implement
