When the Stick Shaker kicked in he could have thought it was due to his over-enthusiastic take-off (perhaps because of shortish runway and heavy load)
Sorry but what is an enthusiastic takeoff ? There is only one correct technique irrespective of all the myriad factors at play. The aircraft is loaded up to the max permitted weight for the r/w length, temperature, altitude etc and no more. Takeoff is then normal and the same margin as at sea level.