The skipping drill: low to medium knee lift, active ball contact under the body and high frequency. How to build on ankle work cleanly without stomping.
The honest answer up front: in skipping you alternately raise the knees with medium knee lift, set the ball of the foot down actively toward the center of mass and extend through leg and hip, at high frequency. BASPO and Swiss Athletics describe the "low and medium skippings" with the focus on a powerful push-off from the feet [1]. In plain words: you are not jumping high, you leave the ground quickly and powerfully.
Why is it worth it? The active foot strike under the body is the core. In a lab study of 14 runners, braking forces rose when the foot landed farther in front of the hip [4]. That does not prove that skipping leads you to a better landing. There is no study on the exercise itself. But it explains why the exercise collection stresses foot strike "under the center of mass" [3]. Important: this means foot position relative to the body, not whether you land on heel or forefoot. Research does not give a blanket rule for the right landing.
How hard is it? You learn the basic idea in one session. Frequency and rhythm take a few weeks, in experience terms. Skipping builds directly on the ankle drill. You know you are ready when you manage 20 meters of ankle drill without the knee giving way.
Who is it for? For beginners who want to improve running technique playfully, and for experienced runners who wake up their rhythm before speed sessions. You always raise tempo, knee lift and distance one at a time, never everything at once.
Begin with the ankle drill over the first meters. Then raise the knee a little more without losing frequency. Milestone: you manage 20 meters of ankle drill without wobbling.
In low skipping the knee lift stays low. The ball of the foot sets down actively toward the center of mass [1]. One foot lands while the other goes up, in quick alternation. The torso stays upright.
In medium skipping the knee lift is higher, described as "medium knee lift" [1]. Legs and hips extend during push-off [1]. The foot lands not in front of the body but under it [3].
BASPO names as characteristics: powerful foot push, powerful push-off phase, high frequency [1]. Anchor: it sounds like a fast drum roll, not like stomping. Variation: do the exercise in place [1].
The running drills run over 20 to 30 meters, then you walk or jog back easily, 2 to 3 repetitions [2]. Milestone: 3 clean passes without the rhythm collapsing.
Film yourself from the side and count the steps over 20 meters. Compare with the ankle drill: if the step count drops sharply as knee lift rises, the lift is too high. In the Lieberman study, a step frequency of about 85 stride cycles per minute, roughly 170 steps, was on average the most energy-efficient [4]. That is an average, not a target for skipping, but it helps you put things in perspective. Also do a test: if you run 100 meters easily after skipping, the steps often feel lighter. That is a feeling, not a measurement, but it shows whether the exercise wakes you up.
An exercise with medium knee lift, active setting of the ball of the foot toward the center of mass and extension through leg and hip at high frequency [1].
Low skipping has a low knee lift, medium skipping a higher one, both focusing on a powerful push-off [1]. The high-knee run, in contrast, raises the knee up to horizontal [3].
There is no study on that. The exercise trains rhythm and foot strike; what that means for your time is unproven.
BASPO advises 10 to 20 minutes of running drills per session, 20 to 30 meters each and 2 to 3 repetitions [2].
A-Skip: Knee Drive, Double Hop and the Tap on the Ground