This is an excerpt from Developing Speed.
Starts and Initial-Acceleration Drills
As outlined in chapter 1, acceleration is the rate of change in velocity (speed) with respect to time. Whole-body acceleration involves the subtle coordination of the acts of accelerating and decelerating the athlete's limbs to increase the speed at which they move. Although acceleration technique may vary from athlete to athlete because of size and other physical characteristics, there are coachable technical factors that all athletes can develop.
Because acceleration is critical to most sports, understanding and developing acceleration technique is important. One of the primary principles involved in acceleration technique is the forward lean. This forward lean allows the pushing action and other technical considerations outlined in chapter 2. As discussed, during full extension of the leg, a straight line can be drawn from head to foot through the hip and knee (refer to figure 2.4). The stronger and more powerful an athlete, the more forward lean the athlete is able to use, bearing in mind that the greater the rate of acceleration, the greater the forward lean. Therefore, it is important for coaches to increase the strength and power of their athletes, in particular the leg and back muscles, in order to achieve the desired forward lean and full triple extension of the hip, knee, and ankle.
As with any speed session, the importance of high-quality repetitions means that relatively long recovery periods be used between repetitions and sets of drills. When using acceleration-oriented drills that involve running, use distances of 10 to 30 meters. When using explosive drills and those that involve significant sprint movement, perform only a few repetitions in each set. This allows enough rest between sets to maintain high-quality training. A sample session for incline sprints on a five-degree slope would include one or two sets of three or four repetitions of 10 to 30 meters. Rest after each rep would be 3 minutes and rest after each set 5 minutes.
Aim To teach or reinforce the posture and leg action in the lean position.
Action The athlete leans into a wall assuming an acceleration posture, a forward lean with both feet on the ground with weight distributed on the balls of the feet. The athlete alternates bringing the left and right legs forward and up as in a running action. Initially this should be slow and controlled, but as competence increases, the athlete can increase the speed. Athletes who pop up soon after beginning a sprint, thereby using very little forward lean, can benefit greatly from this drill and the associated coaching cues that promote better technique.
Aim To develop general leg extensor power and to promote the forward lean.
Action The athlete sprints up a low incline (5-10 degrees), emphasizing effective acceleration action. The added resistance of the incline provides a safe and effective way to stress the strength and power demands of acceleration drills. The upward slope of the surface may also promote an increased awareness of knee drive and full extension while in the forward-lean position. The athlete should walk slowly back to the start to ensure full recovery between efforts.
Sprint Starting From the Ground
Aim To teach effective forward lean in accelerating.
Action The athlete begins lying facedown on the ground with palms on the ground near the shoulders (photo a). On the coach's command, the athlete gets up and sprints as fast as possible to a set point straight ahead (photos b and c). This distance to the point can vary depending on the aim of the drill, but the distance is normally relatively short, about 5 to 30 meters). Because the athletes begin on the ground, as they raise their body from the facedown position, they will begin striding while the body is low to the ground, pushing back and assuming a forward lean.
Read more from Developing Speed by NSCA and Ian Jeffreys.