Resisted sprinting, specifically using light sleds, is growing in popularity for many reasons. The primary benefit of light sleds is the development of late acceleration, a Bermuda Triangle of speed development in many programs. Coaches are starting to wake up to the fact that a holistic training program will likely turn single variable approaches obsolete, especially with heavy sled loads. Don’t get me wrong, I have recommended heavy sleds for specific strength several times. However, chasing heavy loads may work acutely for attaining higher speeds, though years later those same subjects have yet to become world-beaters.
In this article I don’t mince words or pull punches—I bring up the inconvenient truths as to the limits of research and the glory of track and field history. If you are interested in applying available research, this article is for you, and if you are committed to going heavy, this may actually convince you to change your mind as well. Light sleds are not magical solutions—they are specific to athletes who need to improve their late acceleration and wish to break through peak velocity readings.
First Step Quickness or Fastest Step Velocity?
The early steps of acceleration potentially have the most graphic time loss, as the slowest time period in sprinting is likely the most trainable. Coaches love sled sprints and heavy weight training because they’re straightforward in helping acceleration with the untrained or deconditioned athlete. It makes sense on paper—go to the low-hanging fruit and reap quick rewards—but what about years 2 and 3? Top speed, on the other hand, is far more genetic and really about not screwing up the athlete, so coaches tend to hope and pray for results to come. Yet, in the long run, working on maximal speed will indirectly help your acceleration if organized properly.The purpose of light sleds is to work the late acceleration periods that seem to hold back peak velocity from growing, says @spikesonly. Click To Tweet
My main argument for light sleds is not that they help with early acceleration, as I don’t see any direct influence of light loads on early acceleration unless the athlete simply needs general training (non-practice) exposure. The purpose of light sleds is to work the late acceleration periods that seem to hold back peak velocity from growing. I already talked about floating sprints as a way to help raise the absolute ceiling with peak speed, but the distance and speed right before maximal velocity do need addressing more than the profession talks about. It seems that everyone is either chasing the first three steps or the fastest steps, but in between is seen as a means to an end, literally. This article covers the essential connection after step 3 and helps increase the athlete’s potential.
Athletes who do 6-8 reps of 50-meter sprints get in 300-400 meters of quality reps with light sleds and put in work that will reap benefits down the road. No matter your philosophy, a hard set of long acceleration sprints is serious training and will help nearly anyone. Still, it is essential that athletes preserve their elastic qualities during what is sort of mislabeled as “pushing,” as long-term adaptations tend to create an unwanted trade-off that is far from necessary. In my experience, the combination of conventional strength training and long, loaded acceleration is a better long-term solution than heavy sled pushes.
Without dropping names, one of the most successful track coaches on the planet over the last two Olympics was adamant about preserving elasticity during acceleration at nearly all costs. His rationale was that the steps would sustain the same contraction dynamics to rehearse specific qualities seen in racing—and overload the body so the adaptations could scale as they improved over time. I could get into specific ground contact times and cover the contact grid or IMU foot sensors, but speed is a better indicator of how training is trending with light sleds.
For the record, this article is not an attack on heavy sled use being effective or its research being valid, it’s just a case of focusing on the late acceleration of 35-50 meters. I have seen case studies of coaches improving maximal speed while decreasing early departure velocities, but I have yet to see a trade-off-like response improving late acceleration anywhere with anyone else using a conventional speed program. Take a look at the splits of outdoors versus indoors (100-meter splits versus 60), and it’s unlikely you will see a dip in acceleration as a compromise to peak velocity or even speed endurance. The combination of early departure, late acceleration, and peak velocity working in unison will develop a faster athlete everywhere.The combination of early departure, late acceleration, and peak velocity working in unison will develop a faster athlete everywhere, says @spikesonly. Click To Tweet
Alternative Means for Early Acceleration
I am not a huge fan of squats as a panacea for developing early acceleration, but I do appreciate the research. If you are a rugby or American football athlete, this is not directed at you, by the way. I mainly view weight training as injury reduction and a support for sprinting, so you will not see grinding recommendations from me in the weight room. In fact, the purpose of the squat is to help support the snatching and cleaning we may do in my program, but beyond that we don’t chase numbers.
I have written countless articles on why you should squat, but I don’t think you need any impressive numbers, just enough to be honest. Athletes who are in team sports must change direction, so linear speed has limits in training theory. I say this because a diminishing return occurs when athletes train for block starts, and coaches assume if they raise their squat 100 pounds, then they will drop a tenth in their first 10 meters. More block work does more than any weight room exercise, but disrespecting the weight room because it’s not a primary stimulus is self-defeating as well, and far too common.
If you were not able to use sleds at all for early acceleration development, would the world end? Of course not. If you took heavy lifting out of the equation, it would be harder to improve at a reasonable rate, but don’t forget throws and jumps! Horizontal exercises won’t put a slowpoke on the podium, but they are great for the system changes athletes need. Vertical exercises and combination patterns of jumping and throwing are great as well, but remember that the specificity trap is often about mimicking what we see with exercises rather than understanding adaptations you don’t observe with the naked eye. Kinematics are visible but physiological adaptations are not, so remember to prepare the biology of the athlete, not just the way they visibly move.
Finally, there are the reverse leg press and step-up exercises, which are slower and less specific than heavy sleds (pulling or pushing) but very useful. They overload the posterior and anterior chains with a flat foot, and this is a great way to increase overload without dulling the stretch reflex of the ankle. Several mentors suggested really focusing on ankle stiffness in plyometrics and not allowing for “foot mush” with extremely heavy sled pushing or pulling.
You are what your athlete learns, and this gets back to the earlier discussion of ground contact times and elasticity. When you kill an elastic reflex and tap into slower concentric contractions too much, be careful of what you ask for. The difference between the weight room and resisted training on the track is that strength training complements speed, but if you take away the speed by spilling over too much non-elastic work, athletes will adapt to the inputs you program.
I recommend the chapter by Pierre Samozino on sprint profiling promoted earlier, and that should be your testing compass but not your training map. When observing the force-velocity relationship in sprinting, look at how all your inputs interact, don’t just assume that modifying load or speed of direct means is the only way to get an athlete faster. The assessment information is fantastic, and the intervention recommendations are expected, but it’s an incomplete story.
Like all models, limitations exist, and if they were perfect, we would see more consistent performances that would render old records a joke. That has not been the case, and it’s mainly due to the low plasticity of the neuromuscular system after years of training. Again, it’s not that the research is wrong or not useful, it’s just that coaches have our own data that is longitudinal over years (read, entire career) instead of weeks, and that includes designs (read, workouts) that we actually use such as hills and other less understood modalities like plyometrics.
Who Is a Good Candidate for Light Sleds?
Not everyone needs or will respond well to light sleds. Some athletes will blossom without the external support of any sled use, while a majority of intermediate-level athletes will find success just training with light sleds during a preparation phase. Remember that a lot of resistance sled setups help athletes push in a posture that is mechanically effective, but the question is when does a technical model override gross force production improvements?Light sleds are for those athletes who want to augment their late acceleration and have made improvements to their early acceleration from any development path that worked, says @spikesonly. Click To Tweet
Nearly all sled protocols, regardless of loading, will improve horizontal forces over time. Light sleds are for those athletes who want to augment their late acceleration and have made improvements to their early acceleration from any development path that worked. Athletes who have great early acceleration but taper off and seem unable to use a good flying sprint ability are perfect fits. Generally, athletes who are good candidates:
- Have great mechanics at top speed and are consistent early accelerators with or without load.
- Are in a training environment where they can continue to develop speed qualities during the season or career.
- Are either a sprinter or fast enough that they accelerate unloaded without question for more than 30 meters.
- Have coaches who are able to use the right equipment and the right training interventions to improve them outside of the resisted sprint protocols.
Another benefit of light sleds is that the distance accelerating is longer than most sled sprints. Coaches who need overall sprint development should stop worrying about early acceleration that is likely addressed by other means outlined later in this article. Keep in mind that power peaks early, and the theoretical model of holding a sprint position for 10-20 meters at peak power is great on paper but doesn’t work if athletes are not able to hit greater peak velocities. A posture on the third step optimized may not help steps 7 and 8 and will likely do very little at full upright positions.
Also, accelerating means you are increasing velocity over time, and while light sleds allow for a longer acceleration and higher peak velocity, even that approach is limited. The goal of light sleds is to overload a vertical posture without slowing down the speed too much. Remember that top speed is harder to express in practice, so light sleds—even ones that look nearly silly—will slow down any sprinter more than expected, as vertical postures are poor strength positions. Late acceleration may look vertical, but the body angle has just enough lean to provide adequate power for a training effect.The goal of light sleds is to overload a vertical posture without slowing down the speed too much, says @spikesonly. Click To Tweet
Light Sled Workouts and Analysis
Now for what coaches want. If you trusted my arguments, skipped to this point in the article, and just want sets and reps, please at least read the section on who is a good candidate above. Some programs are forced into constrained environments where heavy short sled sprinting may be perfectly fine for them, but this section is mainly for skill positions in football and sprinters. Some soccer and rugby athletes who are blessed may respond to this plan. I will be upfront: Not everyone will benefit from the protocol, so it’s important to accept that if you don’t assess the athlete, you could be wasting your time.
Matt Cross really helped the sport science community get on one page with his work on using dynamic horizontal load measurement. The majority of sprint programs have used load percentage relative to body weight for decades, a method I am not a fan of. Coaches who had access to electronic timing could see speed decrement, but even splits don’t tell the story as well as a load cell.
This isn’t a shameless plug for that technology, it’s actually more of a call for understanding splits and knowing how acceleration and peak speed matter for calculating actual distances in training. While maximal effort will always be exhausting to athletes, how they run and how fast they run will be very different than how an athlete recovers before the next training bout. Coaches need to appreciate the acceleration path just as much as segment splits. Knowing your flying 10 and first 20-meter sprint is useful because they are reference points, but you have to understand the process of getting there.
It’s important to know the distance to peak velocity with an athlete, and that requires both racing information if they are a sprinter and running farther than 40-meter testing. An athlete may not increase speed much past 40 meters, but if they do, then find out the precise distance. Laser or radar systems work best, but video can help if you are able to use the right software.
Athletes are likely to hit peak velocity much earlier, but they can’t peak at less than 50% of their natural distance or it will be too heavy. Due to the fact that athletes can use a crouch or standing lean starting position that can create acceleration problems, it’s recommended the athlete use a typical three-point stance or blocks. This means athletes will need a motorized 1-kilogram resistance setting to perform the sprints, or theoretically be a very powerful sprinter who can use the Sprint Start Sled.
The velocity of resistance needs to be greater than 8 m/s and ideally 9 m/s for peak readings. Don’t use an average to represent the resisted runs, as the shorter distances will inflate the longer reps due to the “flaw of averaging.” Unload the sled until athletes are hitting higher speeds at taller positions. An ultra-light sled will be sufficient to challenge athletes due to the sensitivity of top speed being harder to train. We don’t know why scientifically, but high speeds are harder to achieve in practice compared to acceleration.
Coaches, scientists, and pundits will debate the influence of vertical and horizontal forces. I believe both contribute and are limited to maximal speed. Developing horizontal force at vertical positions may or may not help absolute top speed, but late acceleration is where the ability to generate horizontal force begins to diminish to the point a speed barrier is created.
In summary, the faster the athlete, the more likely they are positive responders to light sleds to a point. Eventually, the elite user will need meet situations and mental ruthlessness to improve training and adaptations rather than “optimized workouts” using sled load. Metabolically, many sled athletes who have used slower reps and heavier loads will become sluggish, in my experience, but that is likely due to the higher effort used. If an athlete feels balanced between posterior chain fatigue and quad exhaustion, then they likely did the workout properly. If athletes don’t report soreness or similar with the hamstrings and glutes, it’s likely they were not vertical or fast enough to create the favorable adaptations.
Go Light for the Long Run
Countless times in this article I made a case for early acceleration and focusing on heavy loads in various forms, so don’t shoot the messenger. I do think that in some circumstances going heavy helps, but my personal observations, along with performance records, make me think it’s not all that valuable.
If you find your athletes plateauing or stuck in development, start looking at the big picture and how fast they are globally rather than how much load they use for early acceleration. It’s easy to get trapped into a myopic view from looking at research studies showing great results over a short period of time with single variables, but time has shown that those methods don’t threaten world records.If your athletes are plateauing or stuck in development, start looking at the big picture and how fast they are globally rather than how much load they use for early acceleration. Click To Tweet
Light sleds were a wake-up call for me, showing that bucking the trend has value when all the pieces work seamlessly. If your athletes are improving, especially more than those of your contemporaries, then it’s fine to look at your own program to learn rather than rely on evidence that sometimes occurs in a vacuum.
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