By Carl Valle
A large number of track and field coaches found SimpliFaster’s two articles on overspeed to be very thought-provoking, and several experts in sports performance had the same curiosity. I made an argument for fresh ideas with my assisted speed article, and dove into the science with the first article on overspeed. Towing is now growing in popularity again, due to the increase in very precise systems on the market, but we still have a long way to go.
My goal here in this third and final installment is to get into the details that could make a program better or could potentially waste time and energy. Enough new science and a year under my belt with the latest towing solutions taught me a few things about overspeed, and I will share everything I know to this point.
This is not a how-to article, as some ideas on planning and implementing overspeed have already been covered. In fact, I think this last part on overspeed may have been a better fit as the second in the series, as it covers the nuances of what happens during overspeed. The main reason I include this at the end is that it was sluggish and painstaking to measure stride parameters with video, but now equipment like contact grids and laser tracking automate it.Together, athlete velocity technology and overspeed can help athletes who have hit a speed ceiling. Click To Tweet
If used together properly, athlete velocity technology and overspeed can make a big difference with athletes who have hit a speed ceiling. Down the road, interventions and coaching programs will be more effective in profiling what an athlete needs, and in delivering the right dose of training to improve maximal velocity.
Braking Forces and Propulsion: What Happens During Foot Contact
A lot of unnecessary debates have surfaced over the decades on how to view sprinting scientifically. There were a lot of failed efforts focusing on either vertical forces to overcome gravity or horizontal forces to help with forward propulsion. I understand and respect the efforts to be innovative, but in the sprinting community force analysis was not only old news—the findings never changed the sport.
Most of the science seen in sprinting or speed development is fascinating and explanatory, but it has failed to live up to earlier methods simply because not much can be done to get people faster besides lifting, jumping, and, of course, sprinting. Some exercises like the hip thrust have helped in particular cases, but for the most part, specific strength is extremely individualized and very limited.
Instead of focusing on the weight room, let’s get back to sprinting and loading the right way on the track. When the foot hits the ground, there are three primary challenges the body must overcome. The first is obvious, as gravity will always be a factor and the body is designed to make vertical force demands a priority. We call early man Homo Erectus, and not Homo Horizontus, as speed horizontally isn’t as valuable as efficiency.
We do see some conflict in the role of muscles like the hip extensors. Lieberman’s investigations into the responsibility of the glute system support the role of maintaining torso pitch, but I believe the study from Kram and colleagues may be more useful for sprint coaches. What muscles can do and what they are best designed for are not the same thing, and it may be that sprinting faster than “hunting speeds” is just an artistic pursuit.
The second priority is the braking forces of the foot rapidly pulling back and colliding with the ground, a necessary event but hardly perfect for speed. Finally, the athlete creates propulsion during the second part of the foot contact, and the hope here is that the body can create greater output than the previous stride or at least maintain it as much as possible. When an athlete hits velocities past 12 meters per second, it forces coaches to find a way to be more productive in developing specific power during a time frame of about 80 milliseconds. So much is happening in a very small period of time that strength training and even plyometrics may not be enough to add speed to an athlete.
So, the problem is clear: In order to run faster, more force must be produced during propulsion. Accomplishing this requires a shrewd coach who can alter his or her recipe a bit to ensure an athlete’s stride will be more effective from training and teaching. An athlete working on power may find strength training works at first, but as the athlete becomes faster, it’s harder and harder to tap into raw force production from a weight room movement. Teaching an athlete to be more efficient during high-velocity running is difficult, as practice velocities are nowhere close to the end-of-year peaking speeds seen in championships. Overspeed might be the only frontier that coaches can use to ensure athletes are exposed to environments that their nervous systems can adapt to.
Stiffness and Overspeed: Thoughts to Consider
It is fair to ask about the existence of “optimal stiffness” in sprinting, as several athletes have succeeded with very different strategies and talents. Stiffness is a tricky quality to describe and calculate, because gait models are only summaries or estimates of theoretical concepts. The human body is not a spring mass model, but a far more complex and sophisticated organism. Still, for practical purposes, we need a simple construct or a coach can be stuck with abstract ideas on Sunday evening and fail to address getting faster for Monday’s practice.
Stiffness is exactly what it sounds like: the ability to rapidly create tension and brace forces in order to rapidly redirect momentum. Unfortunately, having great stiffness doesn’t mean you run faster, as you require propulsion to do more than recycle energy.Great stiffness doesn’t mean you run faster, as you need propulsion to do more than recycle energy. Click To Tweet
Athletes like Usain Bolt have poor stiffness values compared to slower athletes, but his contact and stride lengths are so long that the trade-off is worth the compromise. If Usain Bolt was more stiff, would he have run faster or would he have simply run the same times with different stride parameters? Would he have run slower if he had more stiffness, giving up his hip power in favor of more vertical qualities? Nobody has a good answer yet, but eventually someone will have similar talents with more stiffness, creating a more-effective athlete for running in the 9.4 territory.
It’s hard to say, based on the force analysis from earlier work with Mero and Komi, but it’s my belief that towed athletes overload their knee and ankle joints, as the demands of supramaximal speed are powerful stimuli to sprinters. If an athlete has poor reactive strength, they may need more than just overspeed training. Plyometrics may be enough to prepare an athlete for the demands of vertical forces, as the oscillation of sprinting is about inches and not feet.If an athlete has poor reactive strength, they may need more than just overspeed training. Click To Tweet
The likely issue is that foot speed backwards and the demands of keeping the knee and ankle braced and compliant are too much at high speed, so even athletes with great reactive qualities may not be able transfer a good rebound jump test into horizontal speed. Like maximal strength and peak power, those qualities may not be easily transferred into sprinting, but having a solid capacity to handle vertical stiffness generally might be a way to increase the potential to have appropriate stiffness levels during maximal velocity.
Ideal or optimal stiffness is similar to ideal stride rate and stride length, as it’s more a result of the way an athlete uses their gifts for speed, rather than something you can control through training. Generally, the records are clear that most athletes will improve both stride length and stride frequency over time, and sometimes one parameter will evolve more than the other. The goal is to have a stride that provides maximum speed, and evaluating what is optimal for an athlete is still trial and error until more studies and coaching practices reveal better strategies. In the meantime, measuring stride length and contact time, along with contact length, should be enough to see whether a stride is maxed out or there is more room to grow.
Contact Length: Should We Worry?
Several coaches, many of them thought leaders in the world of sprinting, have expressed their concerns about overstriding causing injury or poor results. I have written about contact length a few times, most notably with a recent suggestion to film and measure it for better outcomes in development.
Like stride length and stride frequency, contact length is connected to the body structure and the ability to create propulsion with an athlete’s nervous system. Some athletes have longer contact lengths, as they need more time to create propulsion or they are mechanically suited to reach and push further away from their center of mass relative to the ground. Contact length is the total distance from initial contact of the foot to toe-off, so it’s not granular enough to know, on video, where an athlete is gifted during the stance phase of sprinting.
We require force analysis, specifically three-dimensional evaluation, to tease out how well an athlete handles braking forces and then creates propulsion afterward. Athletes do not consciously try to overcome braking forces and then immediately place their efforts into pushing off harder. What happens at 12 meters per second is reflexive and, based on sprinting research, muscle groups are highly active even during the recovery phase of sprinting—a time when the foot doesn’t even touch the ground. The contraction speed and relaxation rate are so fast that a cue or conscious effort to enhance technique may not be possible outside of purposely slowing down.
One theoretical idea is that if contact length increases from overspeed training, this specific eccentric training will help maximal velocity abilities later. This is only if the contact length increases during initial contact though, as longer contact distance behind the body isn’t going to have a chance to improve eccentric capabilities. There is no data on the kinematics of longer posterior contact lengths demonstrating a better recovery result mechanically, so it could be that the artificial increase in horizontal speed has little value in backside mechanics.
The takeaway for contact length is that overspeed will likely increase and the reason this happens is subject to debate. Does a longer pre-stretch during hip extension create a longer recovery strategy? Does the rapid horizontal motion cut the vertical demands with some running styles so that early touchdown occurs?The takeaway for contact length is that overspeed will likely increase. Click To Tweet
Because each athlete is unique, I don’t know if true stride adjustments are possible. However, I believe that the proposed contact length is from the overload being too rapid for a sprinter to handle without resorting to a self-preservation style of sprinting that may create possible adaptations or may be incongruent to their development. The likely solution is to profile an athlete with extreme granularity and adjust overspeed to fit the needs of their gait signature.
Thoughts on EMG and Overspeed
The research on sprinting, whether from the 1980s or the present, still can’t solve what is going on during towed overspeed. While advancements in EMG systems have increased over the years, not much can be done to see differences in the very subtle changes to assisted towing, such as a single kilogram of unloading. A mere 5-10% of an athlete’s body weight may increase an athlete’s peak velocity by an entire meter per second—an enormous amount of speed. Most of those changes are only flight distance, a quality that has very little value in actually improving an athlete’s ability to generate speed when not towed. On the other hand, the decrease in contact time and the demand on the neuromuscular system are such a contrast that subtle changes may be enough to show up as improvements in performance later and in EMG readings.
Co-contraction and inhibition are tricky, as the rise and fall on the EMG chart isn’t easy data to work with. Mean and peak values are convenient, but subtle patterns of a line plot may be interesting from a timing standpoint. The scientific community does not yet fully understand temporal changes with EMG. It will take a lot of time before we crack the code in sprinting, so overspeed is a long way off. A rapid rise in RFD and EMG, along with an earlier pretension period, could be a theoretical adaptation, but so far very little data demonstrates this outside of a few jump landing studies with depth jumps.It will take a lot of time before we crack the code in sprinting, so overspeed is a long way off. Click To Tweet
Actual work versus activity is not the same with EMG, so a muscle group firing at certain times, such as stride recovery, is not the same as during stance phase. Force analysis is great, but it requires enormous resources since maximal speed must not allow targeting to occur. Based on what we know physiologically, overspeed could be increasing work while improving neuromuscular firing demands. Usually, an increase in work is a healthy sign of contribution to the body, but the question is where most of the work is during the stance phase.
Additional Ideas on Rehabilitation and Technique Development
AlterG treadmills are used for return to play after injury, as well as to re-educate the body after injury. Reducing vertical forces does have some merit, but reducing or supporting horizontal forces has value as well. Like aquatic rehabilitation, AlterG is similar to an underwater treadmill, as unloading a joint until fully strengthened gives the athlete some locomotive exposure. The issue is that jogging on a treadmill is far from perfect, but it’s better than an athlete stuck doing clamshell exercises and marching in place.
My idea of having athletes use towing as a part of rehabilitation shocked some sports medicine professionals, as some of them felt it would be a risk re-injury. It’s true that any exercise has its risk, but an athlete not having to worry about propulsion can focus on staying rhythmically coordinated during sprinting or fast running. Overspeed is great for developing maximal abilities, while overspeed training used at slower speeds with submaximal effort are assisted speed methods. Using assisted and resisted speed during return to play is new and needs more clinical research, but so far it has worked well enough to warrant inclusion in this article.
Next to rehabilitation, technique development also deserves a mention. Changes to sprinting mechanics at high speed are highly reflexive, as mentioned earlier. Coaches commonly give athletes some general instruction, like maintaining posture and allowing motion to areas that need to respond to torque. Old ideas of heel recovery and casting the foot out at maximal velocity have proven to be more mythical than possible.Overspeed is not a freebie speed development—you must put the work in. Click To Tweet
An athlete can likely improve their technique by allowing a central pattern generator to work when being pulled, instead of trying to do too much all at once. Creating propulsion, focusing on posture, and removing tension in areas that need to be compliant are all very demanding tasks, which is the reason so few can do it. If an athlete can be exposed at high speeds and reduce the burden of horizontal propulsion, they can theoretically learn to shut off muscle groups quickly so that when they are more prepared without assistance, they can replicate those qualities. Just getting towed is not a solution to running faster; you must instill qualities that the athlete can use later without overspeed. Just as wind-aided performances show up later in legal wind conditions, overspeed is not freebie speed development—you must put the work in.
I don’t think that early development is a great fit for overspeed training. There is plenty of time available for youth athletes to grow into their natural stride, and speeding up the process with towing doesn’t make sense. However, I do believe that, due to a combination of recent experimentation and reasoning, intermediate and advanced athletes are good candidates to use overspeed towing methods. My rationale is this: Athletes can improve from basics during the first stages of development, and waiting for overspeed makes sense as it’s potentially the final part to elite performance if implemented properly.
Budgeting and Other Considerations
Any towing system is going to cost money, and a good system can run anywhere from $15-20K. Most coaches will see this as a luxury because plenty of athletes have run very fast without overspeed. The main argument against this type of thinking is that in order to progress, a change is often necessary. The prerequisites for the use of towing are foundational work and the procurement of data such as contact times and horizontal speed from a laser or timing gates. Without knowing the stride parameters, it’s hard to prescribe the perfect assistance for sprinters.Without knowing the stride parameters, it’s hard to prescribe the perfect assistance for sprinters. Click To Tweet
A great coach can only refine a great program so much; innovation and new ideas must surface. Relying on talent is like relying on luck—it runs out eventually. Even talent has a ceiling of potential. I believe that towing, if done right, gives an athlete valuable training experience.