If you’ve read speed training articles, watched most presenters and DVDs, and gone through coaching education, you’ve heard it—the rule. Ten percent. That’s the most you want to load for resisted sprinting, according to conventional wisdom. Ten percent of body weight. Of course, that’s a bit arbitrary because we may be talking a sled or parachute. Grass or track or turf? So it’s evolved a bit to be no more than ten percent decrement in speed.

 

Only ten percent
It’s been handed down over the last few decades like a prized heirloom from mentor to apprentice, coach to athlete. Ten percent. No more or else! If you use more, you risk detriment to sprint technique.Almost all coaches will agree without thinking twice. State it and everyone just shakes their head in agreement. This is blanket rule for sleds and other resistance training, and it’s applied broadly to both acceleration and maximum velocity.

Why? I stuck to this ten percent rule in my early sprint training days because it’s what other track coaches taught me and it made some sense. However, over time, I couldn’t find the full logic and my background as a weightlifting coach probably made me biased toward more load. As I did graduate work in biomechanics and motor control, I developed a new lens to analyze it. For many years now, I’ve used heavy resistance (50–100 percent body weight) to improve acceleration in team sport athletes. It has worked great.


One way to add weight for Mark Sanchez…

If you ask most proponents of the ten percent limit why, you won’t get many solid answers.  Maybe it’s because people aren’t asking the right questions. Let me help ask some.

Are you training acceleration or maximum velocity?
Big difference. The kinetics and kinematics are not the same in acceleration and max velocity.

Quick review: Kinetics is about motion and causes (torque, force, impulse, rate of force development, etc.), and kinematics (velocity, acceleration, joint angles, alignment, etc.) describes the motion. From a technique standpoint, it’s chicken and egg. Each impacts the other.

In terms of force production, here’s what we know today—the vertical force component is always significantly greater than the horizontal. Easy to understand. The first requirement of running is staying on your feet and off the ground. In terms of relative importance, the horizontal component is larger in pure acceleration, but the vertical component is much larger in maximum velocity.

It can be argued that in most team sport settings, it is acceleration that is more common and therefore more important. Right now, what I’m talking about is focusing on improving acceleration. Since we are talking about acceleration and most of the research on resisted sprinting is on max velocity, throw it out.

So what if it acutely changes some kinematics?
Sprinting with resistance changes the kinetics and kinematics. So what? Is that inherently bad? Isn’t that often a goal of training drills? In coaching athletes, I’m often trying to change kinematics. That can be the main point. I may be trying to develop a greater arm action or a larger horizontal force component or a higher stride frequency. It isn’t whether or not heavy sleds change things. For the coach, it’s a question of is it the change you want?

Speaking of different kinematics, what about some other drills that we use? Wall drills change the upper body kinematics, but we decide that the value of training the core and lower body motion is worth the temporary change in the upper body. Plyometrics have different kinematics as do many “technical” drills. Why are those OK but heavy resisted sprinting isn’t?

Remember—of the little data there is on acceleration and resisted sprinting, most is measuring an acute change while doing the resisted run. The question is what does it do to the actual acceleration mechanics without resistance? Chronic unresisted change is what matters, not acute.

What are you using it for?
This is a key question that should drive your decision to use any drills. I like to classify drills as technical, training, or applied. This helps guide my selection based on athlete and training session goals.

Technical drills are designed to improve motor control, build kinesthetic awareness, and teach the athlete how to move. Training drills are designed to elicit a training effect such as force characteristics or energy system development. Applied drills are focused on motor control and are intended to add variability and let the athlete discover the movement solutions to different problems.

In a movement training session, I will have some of each but with a focus on one area more than others. Resisted sprint drills can be used in different ways. An athlete may get a technical benefit out of heavy sled resistance if it brings about kinesthetic awareness and helps him understand the feel of driving back. In working on 40-yard dash starts, I’ll use that heavy sled to build awareness of what it feels like to have tension in the start position.

It also can be a training drill. I may use it to build special strength and work on the impulse components. When used in a contrast method (which for me is almost always), it has a potentiating effect on the following unresisted accelerations.

What research says it’s detrimental?
There is research, almost all of it on maximum velocity sprinting, which shows changes in kinematics with heavier resistances. Does that mean it causes negative adaptation? I don’t care if the athlete’s time over a distance is 1000 percent longer if the technique is correct.

Let’s imagine I have a very heavy load on the sled. The athlete goes for 6–10 steps. If it only moves a few inches on each stride, so what? As long as the mechanics are correct and the contact time is good, why not? You are getting a stimulus even if it didn’t move.


Not exactly what I had in mind.

I definitely think you can cause detriment to acceleration technique if you use it poorly. Add a lot of resistance to the athlete and his form could fall apart. Allowing this while yelling “drive harder!” isn’t what I consider good coaching.

Tips to best use heavy sleds for acceleration
Enough questions already. Bottom line—I question the proposed rationale for limiting sled resistance to ten percent when training pure acceleration. You might want to question it too. Here are some tips I use for sled resisted acceleration.

  • Use heavy sleds for pure acceleration: After using these techniques and analyzing video, I advocate using loads greater than 50 percent and sometimes up to 100 percent for the first five steps of acceleration and that’s it. If you’re getting into longer distances, I think you need lower resistance. As a matter of fact, we barely ever use any horizontal resistance during max velocity. I might be more inclined to add a weight vest to influence the vertical component.
  • Make sure you get the effect you’re looking for: Heavy sleds are going to change something. Whether it’s kinetics or kinematics, consider how the change will influence the adaptation you like. If I have a very strong athlete who is a plodder with long ground contact times already, I need to be wary of very heavy sleds because the change may not be what I was looking for.
  • Contrast with free accelerations: Always follow heavy resisted acceleration with free acceleration. If you are using it as a technical exercise, this clearly makes sense. If you are using it for a training effect, it may not be as clear cut, but I still follow with free accelerations. I advocate a “guided learning” approach to movement training. I introduce technical and training effect elements and then allow the athlete to solve movement problems. These applied drills are key for the individual to adapt the technique to his personal and environmental constraints. I think it’s a key to get a transfer effect into actual sport competition and prevent that robotic look to movement.

  • Use waves for more reps: With an athlete who can handle a higher training load and will benefit from more reps, use contrast waves. Just by increasing overall volume, you could add more reps in each set of resisted runs and then go to more reps of unresisted accelerations. I don’t do this. Instead, I suggest doing multiple waves. Each wave would include 2–5 reps with resistance and then do at least as many assisted. These contrast sets can then be repeated by going back to resistance and finishing with assisted. I find this helps with the motor control adaptation better. I prefer a series of waves where each wave has fewer resisted reps.

Go use it
So now it’s time to figure out what you’re going to use. Ask the questions and analyze the acute effect and the chronic results. Review training adaptations and decide what works. That’s what coaches do!

The sled is an excellent tool, and resisted sled work with 50–100 percent load can be an effective method for working on pure acceleration in the first few steps.