That servo will operate on 5 volts but it could draw more current than the onboard regulator can provide, particularly as you are refreshing it twice as fast as normal.
Try changing
delay(10); // refresh cycle of typical servos (20 ms)
to
delay(20); // refresh cycle of typical servos (20 ms)
I have found that high torque servos like the one you are using need to be operated from a separate power supply. You can use 6 volts if you want the highest torque and speed but it should work on any decent power supply within the voltage range Ben posted. Don't forget to connect the grounds together.
Have fun!