The aircraft took off from Uberlƒndia, MG (SBUL), at 23:32 UTC, bound for Confins, MG (SBCF) While at approximately FL200, on descent, at approximately 23:58 UTC, a pitch down occurred with an inadvertent acceleration. The Indicated Speed (IAS) approached the Maximum Operating Speed (VMO). To prevent an overspeed from occurring, the pilot manually applied pitch control in the CWS. This action caused variations in the aircraft’s vertical acceleration and the collision of two flight attendants, who were standing in the rear galley, against the trolleys. The aircraft landed at the destination airfield (SBCF) without further abnormalities. The aircraft had no damage. One flight attendant suffered serious injuries and the other suffered minor injuries. The other crew members and passengers were unharmed. First aid was given to the two flight attendants by the airport doctor, and later both were taken for observation to a local hospital. Contributing factors. – Application of the controls – contributed. There was a sudden and abrupt application of pitch in the CWS in both directions. This attitude caused a variation in vertical acceleration between +2.43G and +1.02G, which contributed to the flight attendants crashing into the trolleys, causing physical injury. – Attention – undetermined. The low level of attention in the cabin may have contributed to the abrupt action on the aircraft controls, as the pilots were not aware of the flight parameters and were thus surprised by the speed variation. – Piloting judgment – contributed. The choice of descent mode programming, selecting a speed in order to supposedly save fuel, contradicted the manual recommendations, showing that there was an inadequate assessment of parameters related to the operation of the aircraft. Furthermore, the recovery maneuver to avoid overspeed was not in accordance with the manufacturer’s manual and the company’s operational standards, denoting, likewise, inadequate evaluation of operation parameters.