There are plenty
of toys out there designed for speed development, but one of the most
effective and easiest to use is a weighted sled. The research on resisted sprinting using these sleds is way behind the actual use of the device, but that’s usually how it goes. More
recent information has shown that proper use of these sleds can have a
positive effect on an athlete’s ability to accelerate – one of the most
important aspects of speed in many sports.
Most of the early research on resisted sprinting was focused on kinematics. They wanted to see if using a sled would change sprinting mechanics significantly enough to cause problems. Through
experimentation of different loads, it turns out that using a
relatively low weight (8-20% of bodyweight) will not have a
significantly negative impact on mechanics.
The old research also focused on maximal velocity running instead of acceleration. 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. The studies showed that maximal velocity training with no resistance may be better than using resistance.
A more recent
study by Harrison and Bourke out of Limerick, Ireland showed that
training with the weighted sled significantly improved scores on the
time to 5 meters test. The study had subjects
perform two resisted sprinting sessions per week for six weeks, using
13% of their bodyweight as the load. This load was based on an earlier study by Lockie et al that recommended using 12.6-13% of bodyweight. All subjects had experience with resisted sprinting and all were competitive rugby players. They weren’t using untrained individuals, making this much more useful information for sports performance coaches.
After warming up, subjects performed six 20-meter sprints with 4 minutes of rest between bouts. They did this twice a week for 6 weeks and had significantly positive results on their ability to accelerate.
This study,
along with the experience of many coaches, provides evidence that use
of a weighted sled may be beneficial for improving an athlete’s ability
to accelerate. Of course, one of the keys to this kind of training is adequate coaching in the mechanics involved in accelerating. We often see athletes trying to accelerate without a proper forward lean or taking small, lower-power steps. The
sled can be a helpful tool in the learning/coaching process because it
can help an athlete get into a steeper forward lean without falling. It
can also help an athlete alter his/her turnover slightly in favor of
producing as much power as possible on the first 2-8 steps of a sprint.
An extremely important aspect of acceleration training is the use of proper mechanics. Without
quality instruction and the plenty of reps with optimal mechanics, the
use of weighted sleds or any other type of acceleration training will
be marginalized. A qualified coach who can
analyze the athlete’s movements and utilize individualized cues and
feedback to improve mechanics is absolutely essential to this process. Lower-quality instruction will yield lower-quality results no matter what kind of apparatus, toy or method is used.
Knee drive is
another important aspect of acceleration, and information from another
study by Alcaraz et al suggests that a weighted sled may help athletes
exaggerate knee drive. This could be a result of having to pull extra weight or the additional forward lean they observed. Either way, it’s a good thing and can benefit athletes who want to increase their acceleration performance.
Based on the
scientific evidence and years of coaching experience, use of a weighted
sled for improving acceleration performance is recommended as long as
adequate coaching is available so mechanics are optimized during the
process. I recommend focusing your efforts on the first 5-10 yards of a sprint since this is where the most benefit is seen.
We’re still kind of guessing in regards to the optimal load used, but you certainly want to keep it fairly low for most people. The
research does not take into account the abilities of each athlete, so a
more powerful athlete may be able to use higher loads than 13% of
bodyweight and still reap the benefits. Since
the research suggests that resisted sprinting somehow strengthens the
musculature at high velocities, using the heaviest weight possible
without a negative effect on mechanics or joint rotational velocities
seems to be the goal.
I also highly encourage the use of contrast training when using a sled. First, do a few reps without a sled, then perform 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 could simply be a trick,
but it has been suggested that this kind of contrast training can
actually get the nervous system to “up-regulate” with consistent
training over time. When using resistance, the body is forced 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.
Other
professionals, including well-respected trainer Mike Boyle, use
weighted sleds with much higher loads as more of a movement-specific
strength training exercise. You can load the
sled up and have athletes “march” forward, driving the knees upward,
pushing backward as hard as possible and getting into a steep
forward-lean position. There is no real
scientific evidence that this works, but the principle of specificity
would suggest that this could be a good way to add strength when the
goal is to improve acceleration speed.
There seems to
be enough evidence that a weighted sled works to warrant its use when
training for improvements in acceleration speed. Because
there is limited research available, we’re still searching for the
optimal training volume and loads, but some guidelines are being
created through the literature and experience.
· 2-3 days/week
· 8-20% bodyweight as the load
· 4-10 short-distance sprints (5-20 yards) per workout
· Relatively long rest periods between bouts (1 – 4 minutes)
· Utilize contrast training
· Possibly use the sled as a strength training exercise
Try using a weighted sled with your athletes, and be sure to focus on mechanics. While it is just one tool in a trainer’s toolbox, it does seem to have merit. As long as the athlete is giving high effort, using appropriate loads and practicing proper mechanics, you should enjoy the results of faster acceleration after a period of training.