As a drummer, I have always been working on my time. However, in the way I have been practicing & playing, one (or even two) of my limbs were always keeping time for me.
-the fixed swing beat on my right hand
-Hihat played with the left foot on beats 2 & 4, or on all the beats of the bar.
-‘Four on the floor’ on the bass-drum with my right foot.
In most parts of the transcribed material, drummers didn’t use a limb to keep time. Their INNER-TIME was so strong that allowed them to play or leave space (without the need of a ‘time-keeping limb’). Either they played or not, they felt the time.
So, I did my investigation and found some specific exercises that can help a musician strengthen his/her time-keeping: