We've been working on running speed with our 12U team for about six months. We have several girls that just don't get HOW to run.
Agility ladder is great and it is fun. It has really helped our girls to move to the ball quicker. I highly recommend agility ladders. But I don't think it has helped our base running.
For my team, I've had to teach the girls the physical movements associated with running - almost like we teach batting. There are three ways that I've been working with that seem to be sinking in. I found all of this on the internet, but I'm not sure of the right links anymore.
1. Standing running motion. Balance yourself against a wall. Stand straight up on one foot. On the up foot, raise the knee so that the thigh is horizontal, ankle flexed. Quickly sweep the foot to the floor, bushing the ground and return the knee to the start position. 3 reps of 10. This strengthens your hip flexors and gets the kids in the habit of driving the knees high. It seems easy, but our non-runners really struggled.
2. Run against the wall. Lean against the wall at approximately 45 degrees. Straight line from head-shoulders-hips-heel. Lift one knee so that the thigh is horizontal. Quickly switch leg positions. Do it slowly at first, checking form. Non-runners will tend to stand upright or to bend at the waist. Once they get the form, 3 sets of 10 at running speed. Make sure they keep the knees up.
3. Running with resistance. Use a bike innertube- you can get them for free at any bike shop. Make sure you pick the ones from a mountain bike so that they don't break. Loop it around your body with someone holding the back. Loop a large rubber band from thumb to elbow. Make sure kids keep the good straight, angled form. Remind them that when they are challenged, they should move their legs more quickly - many will go slower looking for more power from each step. Remind them to drive with their arms - arms go straight forward/back and not crossing the body. The rubber band will pop off of their arms when they straighten the arms too much. We do 3 sprints with resistence followed by one normal sprint. The kids love feeling like superman at the end.
All total, these drills including the agility ladder take 15 minutes at the start of practice. They could also be broken up into small amounts as the girls are getting back in line, but they really need a coach to check the form until they get the body position. We did the agility ladder work for 4 months with no real impact to run times. These three drills started making a difference within a month.
I've heard other coaches reference arm swing only drills, but haven't added them yet. Basically, you sit on the ground, legs in front of you. Move the arms vigorously until you get a good butt-bump going. Coming up off of the ground is a good indicator that you have a good strong arm pump.