In the cruise there will
be a speed range within which you can safely operate and you will be flying at
the upper end of that range.
In turbulence the
aircraft’s speed will fluctuate and to prevent the speed going above the
maximum or below the minimum the aircraft speed should be reduced to the middle
of the permitted range of speeds.
Turbulence caused by
convective currents reduces with altitude so climb, rather than descend, to get
out of it.