There seems to be more and more buzz surrounding training loads as they relate to speed and power development. I've had young athletes tell me that they don't want to lift heavy because they're afraid it will make them slower.
Sprinters seem to be the most concerned with the impacts that weight lifting will have on their performance. I understand their concern here. If you're going to spend time in the gym, you want to make sure that you're gaining an edge, not regressing.
So the question we want to answer to is - are heavier loads better for developing speed, or should athletes focus on moving sub-maximal loads more quickly?
MUSCLE FIBER TYPES:
Understanding how muscle fiber types respond to increasing loads is an important step in understanding how to improve the sprint training process in the weight room.
There are three types of muscle fibers in the human body:
- Type-I (Slow-Twitch Fibers) - characterized by slow contraction times, a small motor neuron, and high resistance to fatigue
- Type-IIA (Fast-Twitch Fibers) - characterized as moderately resistant to fatigue
- Type-IIB/X (Fast-Twitch Fibers) - characterized as highly sensitive to fatigue but able to produce higher amounts of force than either Type-IIA or Type-I fibers (Research has shown that Type-IIX fibers contract up to ten times faster than Type-I fibers.)
Fast-twitch fibers are characterized by fast contraction times, large motor neurons (with Type-IIX being larger than Type-IIA) and low resistance to fatigue.
It's well documented that sprinters have a higher proportion of fast-twitch fibers than do endurance athletes (1,2). Increasing the number of fast-twitch fibers - specifically Type-IIX - would be advantageous, because they facilitate high-force production activities.
FORCE OUTPUT AND FIBER TYPE:
As we discussed in Simple Hamstring Exercises to Develop Superhuman Speed, "Speed and force have an inverse relationship. As the speed of a movement increases, the amount of force produced decreases." As force increases, so does the recruitment of higher twitch muscle fibers. Slow-twitch fibers are called upon with lighter loads because they have the lowest firing threshold. Fast-twitch fibers, on the other hand, are called upon when large amounts of force are required to move a heavy load.
This supports the argument for using heavy training to develop speed. Heavier loads require more force production from high-force production fibers like Type-IIA and Type-IIX. It would be advantageous for those looking to improve speed to train with heavy loads because it promotes recruitment of Type-IIX muscle fibers.
TRAINING WITH LIGHTER LOADS:
Specificity refers to an exercise's ability to translate to the field (e.g., if you want to train volleyball players to jump higher, what exercises should they do - back squat, power clean, etc.?). Dr. Bryan Mann of the University of Missouri wanted to answer this question.
Dr. Mann initially assumed that Olympic Lifts would have the greatest impact on vertical jump. This assumption makes a lot of sense, because Olympic Lifters typically have very impressive vertical jump numbers. However, Dr. Mann ending up finding that Bench Press was more positively correlated than Olympic Lifts to impressive vertical jump numbers.
Dr. Mann was faced with a perplexing question: "Why aren't these lifts making my athletes more explosive? Olympic Lifts inherently develop explosive power, right?"
ENTER VELOCITY-BASED TRAINING (DYNAMIC TRAINING):
Dr. Mann turned his focus towards the speed at which athletes were moving the bar. He predicted, based on research, that his athletes were moving the bar too slowly to elicit the necessary adaptations to improve speed and power production. So he focused on increasing bar speeds and reevaluated the correlations between vertical jumping ability and Olympic Lifts. After shifting his focus from weight to speed, he found that Olympic Lifts were more highly correlated with jump height.
TO SPEED OR NOT TO SPEED - THAT IS THE QUESTION:
Increases in load helped recruit the necessary Type-IIa and IIx fibers that we need to facilitate explosive movements like sprinting and jumping, but as we saw with Dr. Mann, increased loads don't always translate to improvements in sport-specific movements. Other aspects - like velocity - need to be accounted for as well.
Technical proficiency may determine how successfully a lift translates to on-field performance. Olympic Lifts are very technical movements that require years of practice to perform safely and effectively. One of the observations that Dr. Mann made with his athletes using heavy loads to train Olympic Lifts was that, as the weight increased, the athlete's form continued to break down. Mann noticed greater amounts of lateral foot movement, little hip extension and unbalanced bar catches with heavier loads. Replacing Olympic Lifts with less technical lifts may be advantageous to power, speed and strength development until athletes learn to master their form. For more on this, check out Exercises to Replace Olympic Lifting.
At the end of the day, following or designing a training program that is too myopically focused will yield sub-optimal speed results. It's important to have a program that focuses on both maximal strength and velocity-based movements. If you're already doing this, you're definitely moving the right direction with your training.
MORE ON SPEED DEVELOPMENT:
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