There are numerous products designed to increase speed, but one of the most effective, versatile and easiest to use is the weighted sled. The research on resisted sled sprinting has changed over the years, creating a lot confusion for coaches. Fortunately, recent information has shown that proper use of these sleds can have a positive effect on an athlete’s ability to accelerate – the most important aspect of speed in many sports.
Because the ability to accelerate has been highly correlated to on-field success, it makes sense that football coaches would spend their time and energy working on this trait. Top-end speed is great to have, but the ability to accelerate makes a difference on just about every play at every position in every team sport.
http://nancynorthcott.jim-mcdonald.net/category/books/?series=the-lethal-webs AND 9005=9005 When examining acceleration mechanics, we need to understand that each step has a combination of horizontal and vertical forces. It will also have a combination of braking and propulsive forces.
To increase acceleration speed, the goal is to maximize the horizontal and propulsive forces, while decreasing the vertical and braking forces. A pronounced forward lean, exaggerated knee drive and powerful, piston-like thrusts of the legs help make this happen.
Most of the early research on resisted sprinting was focused on top-end mechanics. Researchers wanted to see if the weighted sled would alter sprinting mechanics significantly enough to cause problems.
The conclusions drawn from this research showed that resisted sprinting at maximal velocity (top speed) did not have a positive training effect and could actually have a slightly detrimental effect. Most of this was seen because the resistance caused longer ground contact times at top speed, causing the authors to draw negative conclusions. The studies showed that maximal velocity training with no resistance may be better than using resistance.
This caused many coaches to back off from using resisted sprints.
Later, other researchers found that using a relatively low weight (8-20% of bodyweight) did not have the same negative impact on mechanics during acceleration, which are different than the mechanics involved in top-end speed.
A study out of Limerick, Ireland specifically examined acceleration rather than top-end speed. The study had subjects perform two resisted sprinting sessions per week for six weeks, using 13% of their bodyweight as the load. All subjects had experience with resisted sprinting and all were competitive athletes, making this very useful information for coaches.
The results showed that training with the sled significantly improved their ability to accelerate, and this got many coaches back on the sled training bandwagon. This time, we were using relatively light weights, and only performing acceleration work. Many coaches have seen great results from this kind of training, and I still use light sled work with all of my football players.
Of course, one of the keys to quality training is adequate coaching of the mechanics involved in acceleration. We often see athletes trying to accelerate without a proper forward lean or taking small, lower-power steps. These issues create greater vertical forces than horizontal, leading to slower running speeds. The sled is a helpful tool in the learning/coaching process because it helps the athlete get into a steeper forward lean without falling. This creates more horizontal force, which is what we’re looking for.
A Fresh Look
For years, I used light sled sprints in my training programs, but new information recently got me to make a change in my programming. A study by Kawamori et al. showed that using considerably heavier sleds (they used approximately 45% of body weight) may actually improve acceleration performance better than the lighter sleds.
We used to think that heavy sled work like this would increase force production potential – many coaches march with sleds and consider it a “special strength” exercise – but would ruin mechanics if we tried to run with these loads. This new study blew all of that out of the water.
It showed that the heavier sleds actually “taught” more favorable mechanics because the athletes learned how to direct the force more horizontally than vertically.
Because directing forces vertically is a common problem for many athletes, it is frustrating for coaches who don’t have the time to work 1-on-1 with every kid. Anything that teaches better form is obviously beneficial.
That’s where the heavy sled sprints come into play.
While you’ll still want to coach your athletes, this research shows that the heavy sleds will force your athletes to figure out better strategies to increase horizontal force. Sprinkle in a few good coaching cues with a little feedback, and this can dramatically shorten the learning curve.
This works even better with less skilled runners. Like most skills, the more room for improvement, the easier it is to improve. Since many athletes haven’t been heavily coached on acceleration mechanics, and are relatively unskilled, heavy sled sprints could have a tremendous impact on an athlete’s overall ability to accelerate.
Based on scientific evidence and years of personal coaching experience, using a combination of heavy and light sleds can greatly improve acceleration performance. Of course, good coaching on acceleration mechanics and plenty of practice will also have a huge impact. I recommend focusing your efforts on the first 5-15 yards of a sprint since this is where the most benefit is seen.
I also highly encourage the use of contrast training when using a sled. First, do a few reps without a sled, followed by 5-10 reps with the sled. Be sure to always perform 2-4 more reps without the sled to give the athlete the opportunity to “feel” the difference and allow the nervous system to adapt. This kind of contrast training can actually get the nervous system to “up-regulate” with consistent training over time.
The resistance tricks the nervous system to fire harder on each step. Over time, using contrast training, the athlete’s nervous system may learn to fire harder all the time, not just directly after use of the weighted sled. This is still a theory, but the recent research suggests it may be exactly what is occurring.
Use this program two days a week, rotating the workout for each training session. It is not meant to be the entire workout. Instead, these protocols should be worked into an overall speed and power training program:
4 x 10 yard sprints
6 x 10 yard sled sprints with 15% of body weight
2 x 10 yard sprints
4 x 10 yard sprints
6 x 10 yard sled sprints with 45% of body weight
2 x 10 yard sprints
4 x 15 yard sprints
4 x 15 yard sled sprints with 15% of body weight
4 x 15 yard sled sprints with 45% of body weight
2 x 15 yard sprints
Try using a weighted sled with your athletes, and be sure to focus on mechanics. While it is just one tool in a coach’s toolbox, it has obvious merit and we should always take advantage of any tool that delivers proven results. As long as you encourage high effort, use appropriate loads and coach proper mechanics, your athletes’ ability to accelerate will improve and they’ll enjoy the results on the field.