Resisting Temptation: Are We Placing Too Much Emphasis on Resisted Sprinting Modalities for Improving Acceleration?

acceleration resistance training speed sprinting Sep 05, 2024

Derek M. Hansen - September 2024

As more and more coaches and organizations are placing an emphasis on movement speed as part of physical preparation, strategic planning and athlete recruitment, we are seeing a greater commitment to protocols and programs directed at profoundly improving acceleration and sprint abilities. Speed development has become an industry in itself in the last decade with new ‘experts’ arriving on the scene every year. However, in the pursuit of enhanced performances and an expanded industry, we often see the pendulum swing too far to one side, with prior conventional wisdom potentially left behind as new ‘innovations’ are introduced. The hype around an approach or new exercise protocol often precedes and overwhelms the true path to high performance and sustainable results.

In the case of improving sprint acceleration and top speed, it appears the last 15 years has seen an overwhelming shift to resisted acceleration methods being used as a primary stimulus for attempting to advance performance. On the surface, it is borne out of a reasonable hypothesis. Adding resistance to any activity or movement is assumed to automatically make that movement better, primarily be addressing strength deficiencies. We are constantly working to oppose the pull of gravity in our daily lives as well as the resistance provided by an opposing player or team, and adding weight or resistance to the human body is presumed to result in a positive adaptation. Even my old Super Man comic books explained that this superhero originated from a planet (Krypton) with significantly greater gravity than earth, and when he was rocketed to our planet he now possessed immense strength and speed, as well as the ability to fly. It made perfect sense to a child. “Gravitational magnification is the answer to enhanced abilities.”

Let me be clear. This article is not intended to demonize the use of resistance methods with sprint efforts and acceleration. I see this resource as more of a ‘market correction’ in response to this overwhelming and unwarranted shift to resisted training methods as a sole means of improving acceleration. I recently attended a performance conference where one of the presenters claimed that acceleration could only be significantly improved by adding resistance to sprint efforts. Additionally, I have also attended sprint training sessions of other coaches simply as an observer and noted that their ‘acceleration day’ involved over 80% of their sprint efforts either dragging sleds, pushing sleds or being resisted by elastic bands. Unresisted efforts were sprinkled here and there, but did not form the majority or even equal share of acceleration work. These instances have made me think harder about this recent trend and whether or not it is a positive innovation or just a passing fad that may have consequences to the health and movement quality of athletes.

Examining the Past

I have been involved in sprinting in the sport of Track and Field since before 1980, when I was a youth track athlete. I trained and competed in the 100m, 200m, 400m, long jump, triple jump, hurdles, relays and several other events. At a young age, we participated in drills, sprints, technical work and, of course, competition. The training was unsophisticated, but we constantly improved as we experienced growth spurts and an accumulation of overall fitness qualities. I joined a track club in 1981 and was even more involved in frequent training and a greater number of competitions. Every year, I dropped my times significant and jumped farther and higher.

In my development as a speed oriented track athlete, we only participated in hill sprints periodically. This represented our only exposure to what may have been deemed ‘resisted’ sprints. It is also important to note that these resisted sprint efforts were only performed as part of a general physical preparation (GPP) phase and could be classified as general strength work or included as part of a fitness circuit or general conditioning regiment. I do not recall any coaches characterizing our hill runs as speed work during this time.

As I progressed to higher levels of competition and training in the latter part of the 1980s, in my collegiate career, we were not exposed to any types of equipment-based resisted sprinting work. Hill runs continued to be performed as conditioning work in the GPP phase of training and we relied heavily on our maximum strength work in the gym and medicine ball throws for strength and power development. Plyometrics were also a significant part of our physical preparation and development. We would periodically hear amusing stories of oddball coaches forcing their athletes to drag tethered car tires full of rocks or shot puts the length of a soccer field, again used primarily as a conditioning tool or torture method. These stories tended to provide comic relief between our boring repetitions of basic – but proven – training techniques.

As a coach in the 1990’s, we continued to use hills as our primary resisted acceleration method early in the training season. I did see the emergence of parachutes in this decade, but you would often see athletes using them for upright sprints over longer distances, not short accelerations. A heavy cross wind would ultimately turn those sprints into a meandering agility session. It wasn’t until the turn of the century that I started to see more use of sleds and similar devices for acceleration training.

When I discussed the use of resisted accelerations with Charlie Francis over 20 years ago, he liked the idea of including them in a program, albeit under certain conditions. He had a special resisted cable device on a flywheel back in the 1980s that they used periodically with his track sprinters in an indoor track setting. He also promoted the use of the Isorobic Exerciser for resisted sprint efforts, with the device using a friction-based cylinder to resist a rope attached to an athlete. Use of either of these devices was a bit of a labor-intensive exercise that did not work well with larger groups of athletes. Hence, they were used sparingly in Charlie Francis’ programs, almost appearing periodically as a novelty and departure from the regular training practices.

Charlie was adamant that any resisted sprinting they would perform should only be done at a 10% decrement of their best unresisted time. Thus, an athlete capable of running a 4.40 second forty yard dash, would be running – at worse – a 4.84 second effort under a resisted condition. If the loads were excessive, he could instantly spot sprint technique flaws including longer ground contact times, over-pushing on the back-side of the stride cycle, hip height dropping and a noticeable heel drop on ground contact. It is also important to note that he always had a robust gym-based strength training program, as well as explosive and elastic power training methods included in his overall program. When athletes graduated to any resisted sprinting, there were rarely, if any, strength or power deficits present.

Benefits of Resisted Sprinting

It is not a stretch to understand that improving strength in athletes, more often than not, creates a better prepared athlete. We also know that when it comes to speed development, strength has a point of diminishing returns. In many cases, it is not that more strength is bad. More so, it is the pursuit of greater strength levels that creates the problem. The additional time, energy and recovery required to continually improve in strength has the real possibility of robbing an athlete of the energy required to elicit greater improvements in running speed. Chasing numbers in the weight room is a common downfall for speed athletes, leaving them wondering why weight-room strength improvements often did not translate into meaningful improvements in sprint times. A linear relationship between weight room strength and running performance does not exist.

In athletes that are lacking strength and power, resisted sprint efforts in training will result in improvements in sprint-related strength over time. This can easily be realized in younger athletes who have not been introduced to a conventional strength and conditioning program. Resisted sprints may also be applicable with mature athletes who have deficiencies in their strength and power. In some cases, these athletes may have had an incomplete training program, with inadequate or non-existent strength and conditioning programming supporting the sprint work. In other cases, an athlete may be deficient in strength due to a previous injury, suffering from detraining effects during their layoff. The physiological adaptations achieved from performing resisted sprints can fill those gaps and sprint performance gains will be seen on the stopwatch or timing gates, as well as many other metrics demonstrated in various studies.

“At the end of six weeks, the 50% velocity decrement group (VDG) significantly improved their performance in all 30-m intervals. Post-training, the 50% VDG showed significantly increased maximal horizontal power, force, and maximal ratio of horizontal-to-resultant force, compared with pre-training. The 50% VDG achieved higher step frequency, whereas flight time decreased post-intervention. No significant changes were found in the performance and mechanical and spatiotemporal variables in the other groups.”

Stavridis et al. 2023

Some athletes may be lacking technical proficiency in acceleration that can be rectified by adding resistance to their sprint efforts. Athletes who prematurely stand up in early acceleration may cut short their drive phase and diminish their full acceleration potential. Resisted acceleration work – particularly when fastened via a waist belt – has the ability to keep athletes in a more advantageous acceleration posture for longer periods of time during a sprint repetitions. Athletes can strengthen the correct muscle groups in his acceleration position, as well as give the athletes a proprioceptive awareness of the correct position, supported by a sled or other resistance method.

Resisted sprinting has also been a useful tool for me in return-to-play scenarios where athletes have been deficient in extension of joints. This is very common in post-ACL surgical rehabilitation cases where athletes are lacking full knee extension under dynamic conditions. Adding resistance in sprint drills or acceleration encourages an athlete to push to full extension at toe off and break through that inhibition barrier. The postural support provided by the resistance devices builds confidence and allows an athlete to perform the desired technique with less stress and anxiety.

In my opinion, one of the biggest advantages of resisted sprinting – whether it’s running up a hill or pulling a sled – is that the movement is slowed down – just enough – to allow the athlete to comprehend what they are doing – in terms of posture, limb positioning, step placement and step frequency – during execution of the acceleration. An athlete can focus on very specific technical elements much more coherently and make corrections from step-to-step and repetition-to -repetition. The intensity of work can still be high while the overall movement is slowed down. While other coaches may be using resisted sprints for physiological benefits, I’m solely focusing on the technical, cognitive and proprioceptive awareness benefits of adding resistance to the athlete. These subtle benefits cannot be understated. And, if you work with resisted sprints long enough, you will find that often “less is more” with lower resistance loads yielding exceptional results.

Cautionary Tales

As I mentioned previously, the shift to more resisted acceleration work has, in my mind, created some concerns at all levels of training and performance. When coaches and athletes shift toward one type of training, this also means that they shift away from other types of training. In the case of acceleration training, repetitions used at one time for unresisted sprints are now occupied by resisted sprints. One may ask, “Why is this a problem?”

Adding weight or resistance to an activity has the dual impact of creating positive adaptations for strength, but also an increased risk of creating injury if performed in excessive volumes and biomechanics are altered significantly. If we closely examine the implementation of sprinting in training sessions, if all of the sudden at least 40-50% of those steps being taken are loaded with an extra 35-40lbs of resistance, there is a possibility of both over-reaching (within a session) and over-training (over multiple sessions) to occur. Sprint training volumes (total distance covered) may not change, but overall training loads and bodily wear-and-tear can be increased significantly with the addition of resistance.

Ideally, the ‘perfect’ program would have a progressive increase in both volume and intensity graded over time to on-board athletes to the resisted sprint program. This program may be sequenced over a 8-12 week program to allow for both general and specific adaptations to take place. Loads for resisted sprinting would be adjusted to fit the body size, weight, strength, training history and age of the subjects. Resisted work would be interspersed with unresisted work to make sure that an athlete was provided with ample repetitions to integrate new postures and limb movements attained in resisted runs, transferring to regular sprint efforts.

Practically, we know that perfect planning, gradual progressions and precise execution rarely happen with resisted sprinting. Athletes are typically assigned a sled with the same weight used for the majority of athletes or, at best, a smaller training group. Training windows of opportunity are much shorter, and coaches are forced to employ a ‘trial by fire’ approach that gets athletes into shape as soon as possible. Recovery periods are likely shorter than need be. And, footwear and training surfaces place more stress on the lower limbs than ever before. Because athletes are not given more time to accommodate both resisted and unresisted repetitions (much less assisted reps), coaches tend to perform more resisted reps because it simply adds up to more work and, on the surface, looks more productive to sport coaches.

While many people would simply chalk this up to less than ideal training, there are other repercussions. Whether or not the data supports my anecdotal findings, I am hearing more and more about lower leg and foot injuries occurring in both off-season training, training camp and regular season competitions. We have all seen the reports of rising cases of Achilles tendon ruptures at all age groups and in numerous sports. Unfortunately, I have been hearing more and more about actual Achilles tendon, plantar fascia and calf injuries occurring during speed training, with the majority of those cases involving resisted sprinting modalities. Perhaps the increase in lower leg injuries and the gaining popularity of resisted sprinting is just a coincidence. I do think the issue deserves a much closer look, with practitioners taking stock of how they are implementing their sprinting programs, with or without resistance. Excessive volumes and loads, as well as rapid progressions, may be part of the problem.

At a recent Strength and Conditioning conference in Fort Worth, Texas, I had the pleasure of speaking with Jake Tuura, a coach that is heavily invested in studying tendon health and injury prevention. We both agreed that the recent uptick in tendon injuries is not the result of healthy tendons spontaneously rupturing under heavy loads. It is more the result of long-term degeneration of the tendon tissue ultimately leading to a tissue failure, with almost every ruptured tendon exhibiting fraying and necrotized fibers at the injury site. The combination of over-use, wear-and-tear, inappropriate recovery and other localized ischemic issues within the tendon are contributing factors, and are not just limited to older athletes any longer. Equipment innovations, training changes, limited recovery and environmental conditions can all combine to contribute to this chronic tendon wear-and-tear. The choices we make as coaches can also have an impact on how we find our way out of this epidemic.

Aside from injury concerns, I also have noticed that athletes who perform a higher volume of resisted sprints at heavy loads tend to retain the global muscle tension and overall tightness in their running form when performing unresisted runs and other dynamic movements. I believe this tightness creates excessive background noise in the nervous system that impairs overall coordination, harming performance potential for high-speed movement and creating more problems for muscle mobility as it relates to athlete health. Some studies have suggested that excessive loads can disrupt running mechanics and coordination.

“Heavier loads led to significantly lower biceps femoris long head activation and higher rectus femoris activity (p, 0.01–0.05). Significant reductions in leg stiffness were observed as loading increased (p, 0.001–0.05). Kinematic variables showed substantial changes with higher loads during the acceleration and max velocity phase. In conclusion, the heavier the sled load, the higher the disruptions in muscle activity, leg stiffness, and kinematics. When coaches and practitioners intend to conduct training-resisted sprint training sessions without provoking great disruptions in sprint technique, very-heavy sled loads (greater than 30% velocity loss) should be avoided.”

Zabaloy et al. 2020

Teaching relaxation as part of maximal efforts, particularly for high velocity movements, is an underrated concept. Unbridled maximal effort can lead to all sorts of problems when executing skill-intensive movements. Bruce Lee wrote about the concept of relaxation in relation to executing his martial arts techniques. “The more relaxed the muscles are, the more energy can flow through the body. Using muscular tensions to try to ‘do’ the punch or attempting to use brute force to knock someone over will only work to opposite effect.” I see the same thing happening with sprint technique and athlete responses following heavy resisted sprint methods. Athletes are experiencing a diminished ability to relax muscle quickly and efficiently, thereby disruption inter-muscular and intra-muscular coordination.

“Everything you do, if not in a relaxed state will be done at a lesser level than you are proficient. Thus the tensed expert marksman will aim at a level less than his/her student.”

Bruce Lee

Alternative Options

Whenever I reflect on the resisted sprinting issue, I start to look at other areas of research and anecdotal discussion as it relates to velocity improvements. One of the most prominent sporting activities involving contrasting conditions is the use of over-weight baseballs versus under-weight baseballs for improving throwing velocity and mechanics. A significant amount of research has been completed on this activity, but there still seems to be some questions around the key variables of how much and how often. Here is an example of a few excerpts on the subject:

“A 15-week pitching training program with lighter baseballs significantly improved pitching velocity without causing any injuries, specifically to the shoulder or elbow. Lighter baseballs should be considered as an alternative to weighted baseballs when attempting to increase a pitcher's velocity.”

Erickson et al. 2020

“The inconsistency in the methodology of weighted ball programs and studies has made it challenging to draw (scientifically) meaningful conclusions. Nevertheless, several studies have offered empirical evidence in support of the claim that weighted ball programs can increase pitching velocity through improved throwing mechanics. At the same time, these studies have emphasized the improvements in performance, while the potential effects on injury mechanisms have been less well understood.”

Melugin et al. 2021

Due to the lack of consistency around protocols, we can only draw general conclusions around the use of underweight versus overweight throwing practices for improving velocity. It appears that both underweight and overweight throwing can have a positive impact on throwing velocity. As with any physiological research, the choice of subjects for the study can have a significant impact on our general interpretation of results. Poorly trained or moderately trained subjects will almost always have more positive effects from loading or unloading schemes than highly trained, elite-level subjects. Overweight throwing also seems to carry higher risks of injury. Thus, choosing the right amount, proportion and frequency of overweight versus underweight baseball throwing repetitions might be the magic bullet in this scenario. Slight variations in weighted or unweighted throws, combined with consistent, biomechanically efficient foundational work with a standard weight baseball may be the best answer.

I also remember having a conversation with an ex-discus thrower who competed at a high level and how he would often conduct technical sessions with an implement that was lower in weight that his competition discus. These sessions allowed him to relax, work on arm speed and refine technical elements of his throwing mechanics much more effectively than constantly working with the standard discus, or using a heavier implement. He also found that that the slightly lighter discus allowed him to incorporate a higher volume of throws – working on precise biomechanical issues – with less wear-and-tear on his shoulder and the rest of his body.

In a recent article on the former NFL defensive lineman standout, Mark Gastineau, he was quoted as saying he worked on his speed by sprinting downhill in his driveway for numerous repetitions in the off-season while in college. His 40 yard dash time at 265lbs was recorded at 4.59 seconds. Coach Al Vermeil told me that he would have his football athletes run down the crown slope of the older Astroturf football fields to fit in some faster accelerations. I’ve heard of other 20^th Century athletes doing these types of workouts back in the day as well. While not a training staple of most of these athletes, it was a technique that was employed periodically to provide variation.

These types of results and anecdotal information make me wonder if more experimentation and research needs to be done in the area of “assisted” acceleration. The benefits – if done correctly and not excessively – seem to be credible. By unloading some of the resistance encountered in the early stages of acceleration, athletes have the opportunity to relax their muscles and execute the required biomechanics for optimal acceleration. The reduction in excess muscle tension – which can often get in the way of rapid execution of limb movements – can be a valuable learned skill as part of a consistent assistance based program completed periodically in a specific preparation or pre-competitive phase.

Similar to the underweight baseball and discus examples, an assisted sprint experience executed precisely, has the ability to minutely unload the athlete in manner that diverts energy to muscular coordination – enhancing excitation and inhibition reflexes – to execute more rapid limb repositioning with shorter ground contacts. As with resisted sprinting work, this cannot be implemented haphazardly. An optimal assistance level must be implemented to ensure that the athlete is still actively involved in propulsion and not forced to brake on every step as they are pulled into the ground.

One of my colleagues – Carl Valle – has worked extensively with Muscle Lab’s DynaSpeed device to implement extremely precise resisted and overspeed sessions to train acceleration abilities. His findings on the assisted-sprinting side of the equation have been profound and give me the impression that this may be the new frontier for providing low risk variations in acceleration training that improves relaxation and mechanical efficiency for speed athletes. Obviously, more research into this area needs to be undertaken before we can precisely assemble an optimal assisted-acceleration program for athletes.

It Always Comes Back to Planning, Education and Execution

Good coaches will always implement novel techniques in a subtle manner so as not to detract from tried and true techniques that have endured the test of time. Chasing fads and quick fixes is generally not considered a sound long-term solution, particularly if athletes are hoping to experience longevity at the top of their sport. My reasons for writing this article fall back on the concepts of sustainability of performance and athlete health. All coaches should be basing their programs on precisely planned training methods that yield a combination of improved performances along with enhanced health and resiliency.

Figure 1: Prioritizing Acceleration Training Methods for Maximum Benefits

Different training methods and associated tools will come and go. In many cases, they are recycled every 10-20 years, making comebacks when people get bored of proven techniques. But, sweeping changes must be avoided at all costs. Time must be taken to gradually expose athletes to a new method, with observations being made on a consistent basis to precisely determine the impacts of an intervention.

The difference between a successful intervention – particularly one that brings the benefit of longevity – and a tragic intervention often involves contextual changes, progressive introduction and appropriate dosing. I myself use resisted sprinting methods with my athletes. However, I am acutely aware of the risks and benefits of using such methods and carefully weigh my decisions around implementation of these methods. Newly onboarded athletes may only use low to moderate resistance with drills for a few weeks as a means of acclimating tissues gradually, before we engage in more aggressive horizontal projection and actual resisted sprinting. The primary intent is to provide postural support and core-engagement awareness. Resistance intensities may be very low for initial introduction into a program, with a frequency of exposure at only session per week. These exposures and intensities grow over time, while we monitor movement execution and relaxation levels, as well as muscle soreness.

Establishing a foundation of movement and running volume that does not involve any resistance or assistance must be present in every training program. If we had to put a number on it, I would say that 80-85% of all sprinting and acceleration volume should be unresisted and unassisted in an overall program. In a GPP phase, resisted/assisted work might comprise 30% of your total sprint volume, as strength development is prioritized and technical goals for acceleration mechanics are established. As you approach a competitive phase, this number may drop down to 10-15% simply to maintain postural qualities and refine mechanics under higher speed conditions. But, every coach should understand that ‘unaltered’ sprinting must build a solid base of work for your speed program.

Figure 2: Planning and Periodization of Acceleration Methods

I get it. We live in an age where we want to make a tangible difference with our athletes. If we simply give them sprint cues as part of our training sessions, it may not seem like enough ‘engagement’ for athletes. If we strap something to the athletes, collect large spreadsheets of data and show them 4k slow motion videos of every repetition, perhaps coaches feel like they are making more of a contribution to that athlete’s development. Is it necessary? I don’t think so. Is it desireable? Certainly. However, I have come from a different generation of coaching and athlete development that prioritized hard work, precision and simplicity. Call me boring.

As such, a good friend of mine who also works with world class sprinters has coined the recent trend of using resistance for speed development the “Strength and Conditioning-ification of sprint training.” The Strength and Conditioning industry has carried a good deal of influence in the last 20 years over all aspects of sport preparation and the commercialization of training techniques, equipment, technology and revenue generation. Sometimes, the potential to make money and attract ‘views’ can distract individuals from simpler means of achieving a goal. A good sprint coach knows that improvements in acceleration ability can be achieved by a simple combination of technical coaching, repetition and subtle manipulation of starts, volume accumulation and recovery. Some of the best sprinters in history never resorted to extensive resisted sprinting methods. Most of the recent improvements in sprint performance can be more attributed to equipment and surface enhancements, not ground breaking coaching methods.

Sometimes, you have to fight the desire to feel relevant and instantly rewarded as a coach. Resist temptation. Embrace delayed gratification and nuance. In a world filled with AI, video-shorts, binge-streaming and virtual reality, the patience to see a process through and achieve subtle improvements over an extended period of time must be glorified and lauded. I firmly believe that those who choose this path of patience and purposefulness will be rewarded with sustainable performance abilities and greater overall health and longevity in their sport and life.