Maybe this will sound a little too simplistic, but…
Specific and immediate feedback.
Does increasing one’s absolute or relative strength improve speed? Might increase one’s potential to increase speed, but I would say it probably does not directly.
But in response to Carl’s question of S & C coaches routinely getting linebackers to squat over 400, but how many are getting them to run 4.4’s?
In the weightroom, the athlete has immediate feedback, did I, or am I completing the task? i.e. squatting 405 for 1 rep. For the athlete there is always a “gauge”; the weight. Strength training becomes a skill for which there is constant and immediate feedback, for quality “learning” to take place… increasing one’s myelin production.
With speed work/sprinting, how often does one have an immediate feedback mechanism or “gauge”? Is the athlete always sprinting against or after a measurable indicator that is immediately available to the athlete’s sensory systems for adjustments and corrections, or in the case of something as fast as a sprint, “I need to be moving faster”; like a lure or ‘rabbit’ in greyhound racing. Or racing an individual who is slightly faster, which gives the athlete the IMMEDIATE FEEDBACK; is success being attained or not. This would allow for the skill development or ‘learning’ of speed, using greater intention to accomplish a specific task.
Without an immediate, obvious, and available indicator, the athlete has not much direction to channel intention. With the available feedback, i.e. racing an individual slightly faster or going after a lure, may also shift attentional focus from an INTERNAL FOCUS, to an EXTERNAL FOCUS, which has been shown in motor learning to enhance performance.
In Massachusetts, every so often an exceptional high school sprinter comes along. They usually end up being limited by coaching and competition. The net result is when it’s time to shine at big meets, they don’t do well because they’re used to winning by 5-10 meters and they’re not prepared to race against more talented athletes. The coaches of these athletes need to expose them to higher, but appropriate, levels of competition.