I came upon an article the other day about speed development where the author stated several times that increased strength development always results in increased speed if weight and technique remain the same. So an athlete that lifts 300 lbs. will be faster if he improves to 400 lbs., and faster at 500 lbs., and so on.
At novice levels there is a high correlation between all motor abilities. I remember Coach Joe Kenn use to joke that he could take a young kid and do walking lunges for a quarter-mile every day and the kid would get faster. This just speaks to the extent of how easily a novice athlete can make gains.
As an athlete advances there becomes less and less correlation between maximal strength and speed. At some point there is no correlation and it can eventually become a negative correlation.
Maximal strength work can be a hindrance to speed development in the slowing down of the nervous system. The human body adapts to how it is trained. When athletes focus on slow heavy lifting day after day, the body can and will adapt to the slowness it continually repeats.
Athletes must always remember speed and maximal strength are separate motor abilities. Early in training, the correlation between strength and speed is high, but as the athlete advances, the correlation becomes less and less. If you were to take Usain Bolt and increase his squat 50 lbs., many individuals think this would make him faster. If it were only that easy. Taking him from a 450-500 lbs. squat would yield no improvement in his world record times. At some point, continuing to train maximal strength for an athlete is not worth the time of training invested. When an athlete reaches a certain point, energy should be directed toward maintaining that strength while focusing on improving other key motor abilities.
Many coaches believe that Olympic lifts have a direct correlation with speed since the O-lifts are performed with speed. However a good Olympic lift velocity may only reach 1.3 meters per second, where-as maximal speed may be around 7 meters per second.
It takes time to develop maximal force, and this is a common area of misunderstanding. Sprinting ground contact times are measured in the hundredths of a second. This is the time that an athlete has to display force in sprinting. Being able to grind through a four-second rep means nothing when your foot has .08 seconds to display as high a force as possible. As I have stated throughout, after a certain level of strength has been achieved, the focus should change. Athletes should be more concerned about the speed at which they can display strength than at the sheer magnitude of how much more they can lift.
Take a competitive powerlifter, or an elite level Olympic lifter. These athletes would be world record sprinters if strength were the main determinant of speed. While these athletes may be fast they do not progress in speed at the same level their maximum strength progresses over the course of years.
There are so many more things involved in speed than just strength alone. Speed is more dependent on the stretch-shortening cycle, reactive ability, elasticity, nervous system efficacy, tendon attachment, and limb length, among many others.
photo credit: Singapore