A WDB IN HOLDING AT FL330 DSNDED TO FL290 BECAUSE OF SPD DECAY. AT FL290 IN A TURN THE STICK SHAKER AND AUTO SLAT EXTEND ACTIVATED AS THE ACFT STALLED.

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ENRTE TO ZZZ AT FL330 (OPTIMUM ALT WAS FL350) AND WE WERE ASKED TO ENTER HOLDING AT WAYPOINT AS PUBLISHED. WE ENTERED THE INFO IN THE MCDU AND THE FMS CALCULATED A HOLDING SPD OF 230 KTS; 5 KTS ABOVE THE V MINIMUM (LOWER FOOT) SPD. I ELECTED AND REQUESTED TO HOLD AT 240 KTS TO ALLOW 15 KTS OF AIRSPD HIGHER THAN VMIN. UPON ENTRY INTO HOLDING; THE AIRSPD STARTED TO DEGRADE AND CONTINUED TO DEGRADE BELOW VMIN. IT WAS APPROX 5 KTS BELOW VMIN WHEN IT FIRST ROLLED OUTBOUND IN HOLDING TO LEVEL FLT AND WE CONTINUED TO MONITOR EXPECTING THE AIRSPD TO ACCELERATE BACK ABOVE VMIN. THE PWR SETTING WAS AT CLB PWR BUT THE ACCELERATION RATE WAS SLOW UNTIL IT GOT TO THE INBOUND TURN WHERE THE AIRSPD AGAIN CONTINUED TO DEGRADE. THE ACFT BANKED AT AN ANGLE OF APPROX 23 DEGS AT WHICH TIME I SELECTED LIMITING THE AUTOBANK CTLR TO 15 DEGS TO ATTEMPT TO PREVENT THE AIRSPD FROM FURTHER DEGRADING. REALIZING THAT WE WOULD BE UNABLE TO MAINTAIN ALT WE REQUESTED AN IMMEDIATE DSCNT TO FL290 AND A HDG OF 220 DEGS WHICH WE IMMEDIATELY RECEIVED FROM ATC. I SELECTED LEVEL CHANGE TO FL290 AND ALSO SELECTED A HDG OF 220 DEGS. THE AUTOPLT REMAINED COUPLED BUT THE AIRSPD CONTINUED TO DEGRADE AND CONSEQUENTLY WE GOT A STICK SHAKER AND AN AUTO SLAT EXTENSION DURING OUR DSCNT TO FL290. THE AUTOPLT REMAINED COUPLED AND NO ABRUPT INPUTS WERE MADE TO BOTH THROTTLES AND FLT CTLS DURING THE STICK SHAKER CONDITION. UPON LEVELOFF AT FL290 I SELECTED A SPD OF 300 KTS AND RECEIVED A NEW CLRNC FROM ATC FOR THE NE ARR INTO ZZZ. ACFT FLEW NORMAL THROUGHOUT THE ARR DSCNT; APCH AND LNDG WITH NO FLT CTL ISSUES NOTED.