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The Sled: Resisted Sprint Training Considerations

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James Smith

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James Smith is a coach, consultant, and writer. Smith has coached at all levels including Olympic, professional, university, high/secondary school, and private sector. Smith has expertise in a range of sports including track and field, rugby, luge, football, water polo, martial arts, volleyball, and other disciplines. Smith was most recently Senior National Physical Preparation Coach with Performance Director responsibility for the Portuguese Rugby Federation. Smith writes for blogs on the websites Global Sports Concepts and Athlete Consulting and he recently published the book, Applied Sprint Training.

Tools to Develop Sprint Speed

There are a variety of tools available for those engaged in the endeavor to develop an athlete’s sprint speed. Sprinting, particularly the rate of change of velocity (acceleration), is one of the most profound constituents that is shared across a spectrum of sport disciplines. When one assumes an exploded view of sport structures, one then observes the many movement commonalities shared between them.

One sport observation, taken from such a global perspective, is that the ability for an athlete to accelerate their limbs, their body, an implement, or the implement which transports their body, across, or through, the competition surface is a shared requirement irrespective of sport. This holds true regardless if the competition occurs on a mat, track, field/pitch, court, ice, rink, Velodrome, snow, sand, or in the water, a ring, or a cage.

More specifically, the ability for an athlete to accelerate themselves, via the land based bipedal sprint action, is often a determining factor closely linked to the sport outcome of a sprinter, jumper, field, or court sport athlete. The act of sprint acceleration is the most potent unifier regarding the specific commonalities shared between athletes competing in those domains. Taken from my book Applied Sprint Training.

Once this fact is accepted the next question is how to most optimally address the training of speed for any particular population; ranging from world class 100 m sprinters to school age field sport athletes.

Weight Sled

A near household training implement, familiar to any sprint coach, is a sled. The sled is one of many means of introducing external load via which the sprinter must exert against in order to achieve locomotion.

There are some critical points of consideration that one must recognize prior to introducing sled sprints in the training of athletes.

  • Magnitude of External Resistance (Sled Frame Weight, additional load) — Not only must the weight of the sled itself be accounted for, in addition, the load placed on top of it.
  • Surface Friction — the nature of the sprint surface combined with the architecture of the sled has profound implications on the surface friction.
  • Acceleration Implications — the greatest change in the rate of velocity occurs over distances specific to each athlete and their associated force: velocity characteristics.
  • Mechanisms of Speed Potential — every athlete possesses a unique composite of attributes that, together, constitute their speed potential.

One of the primary considerations one must take into account when using a sprint sled is how much it will decrease the athlete’s speed over that distance relative to what they are capable of generating in an unresisted fashion. This must then be weighed against that athlete’s mechanism of speed potential as well as his or her current speed potential.

There are effectively three broad categories of speed foundations in any athlete:

  • Force Based (Bob Hayes, Ben Johnson, Maurice Green)
  • Reactive/Elastic (Tommy Smith, Bob Beamon, Carl Lewis)
  • Some Combination of the two

Athletes from all three categories may achieve world class levels of sprint speed and their training must be individualized to their attributes.

A force based athlete is one in whom their speed potential is largely credited to their muscle/mechanical attributes. These athletes are, usually, the most proficient in the weight room as well as talented accelerators due to the predominance of volitional force generating efforts that contribute to acceleration; particularly short accelerations.

A reactive/elastic athlete is, alternatively, one in whom their speed potential is largely a function of their reflexive/reactive/elastic attributes. These athletes, on the whole, are generally less impressive in the weight room yet most talented in the ranges/distances heavily weighted in speed endurance (i.e., 80-150 m) and special endurance (+150 m) (both distance ranges illustrated with respect to world class level male sprinters).

A combination athlete, as the name suggests, represents a relatively proportional assembly of force based and reactive/elastic qualities.

Due to these factors, a force based athlete possesses a greater potential to benefit from comparatively heavier sled loads than a reactive/elastic athlete. The muscle/mechanical attributes of the force based athlete will allow him or her to negotiate a heavier loaded sled at a higher speed, relative to their unresisted maximum, then the reactive/elastic athlete. In this way, the heavier sled will serve as more of speed stimulus for the force based athlete and a strength stimulus for the reactive/elastic athlete.

The existing speed potential, irrespective of the athlete’s mechanism of speed potential, is another factor of paramount importance. Speed, due to its highly synchronized neuromuscular interplay of relaxation and contraction qualities, is a motor ability that necessitates high levels of stimulation, relative to the maximum, in order to advance. That said, the magnitude of stimulation is always relative to the athletes ability.

The question as to what sort of stimulus is required to advance speed lies in knowing that athletes existing maximum (over whatever distance) weighed against the speed of the desired training activity- such as a sled sprint. Critically important, is that the coach/athlete has the means to accurately measure the athlete’s speed of movement such that objective, and not subjective, indicators may be used for assessment; something which the Freelap units are well designed for.

It is generally accepted, that pure speed training requires a stimulus in excess of 90%, some would argue +95%, of that athletes current PB over a given distance. For example, if a sprinter is capable of 10.00 in the 100 m then they would need to manage at least 11.11 (90%) or 10.53 (95%) in order for that training rep to count as a speed stimulus. This reflects maximum velocity and speed endurance work. Anything slower cannot be accounted for as true speed training.

The same rules apply for acceleration work. For example: Usain Bolt ran 3.78 sec 30 m splits in both his Beijing (9.69) and Berlin (9.58) performances. By definition, Bolt would need to manage a minimum of 4.2 (90%) or 3.98 (95%) in a 30 m training rep if the objective is acceleration development. Anything slower would not qualify as a true speed training exercise. This is not to state that anything slower is not a viable training activity; however. What is important is to recognize the nature of training efficacy and while a variety of training activities may be beneficial it is essential to understand the nature of their transfer to the competition outcome.

The sled is an acceleration tool as the nature of the external load requires that the athlete produce an angle of extension that is closer to the ground. The heavier the load, and/or greater the friction, the more steep the angle. Implications on acceleration are such that faster athletes accelerate longer. In this way, an athlete who is able to accelerate to 50 m will benefit from longer sled sprints than an athlete who can only accelerate to 30 m. Again, an accurate means of timing is central to making such determinations.

Generally, males are able to accelerate longer than females and track athletes are able to accelerate longer than field sport athletes. Further, even elite male 100 m athletes (sub 9.8) achieve the lion’s share of their acceleration within 30 m; after which they continue to accelerate yet their rate of change in velocity is much more gradually sloped between 30 m and the point at which they reach maximum velocity (which is in excess of 60 m for the fastest male sprinters).

The fact that <30 m represents the bulk of acceleration in the fastest athletes in the world bodes well for field sport athletes whose speed requirements are nearly entirely rooted in acceleration; in that the methods of acceleration development for elite track athletes should absolutely be absorbed by non-track athletes. As the bulk of acceleration occurs inside of 30 m it then stands to reason that the bulk of acceleration development training may take place inside of 30 m; including sled sprints. Sled sprints are commonly used in the beginning of yearly preparations for T&F sprinters and this may be assimilated into any field or court sport athlete's training for the same purpose. In addition, the sled serves as one of many viable options for a field or court sport athlete to drill acceleration development mechanics at a lesser cost than an unresisted sprint; even during the competition calendar. The sled slows down the runner, even if only by a small margin, however, small margins account for substantial neuromuscular stress within the sprint training paradigm. For example, while the difference between Bolt's 3.98 and 4.2, 95% and 90%, 30 m training reps seems like a nearly insignificant difference on paper; we may be assured that the 0.22 difference that he feels between 3.98 and 4.2 is profound. The field/court sport athlete's in-season preparations are heavily weighted in specific technical-tactical workloads. While acceleration sprints are part of most technical-tactical training during team sport preparations, particularly scrimmages, we must question the quality of those accelerations. A small volume of mechanically sound sled sprints may prove useful, pre-practice, during competitive stages of the year and the reduced neuromuscular stress vastly lowers the physical cost. The sled represents one of many tools that may be effectively integrated into the acceleration development of any athlete. It is important to recognize the implications of the weight of the sled and its load, as well as the friction, relative to the athletes' mechanisms of speed potential and their existing speed potential. These factors are central towards making wise coaching decisions and the distinction between what is true speed training and what is not. Please share this article so others may benefit. [mashshare]

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