Before even beginning, lets clear up one point.
Sport is about acceleration, not speed.
We have a problem in sports. Coaches consistently use the wrong term when discussing the quantity they covet most. Tests like the ten, twenty and forty yard dash are actually tests of acceleration not speed. You only need to look at world-class sprinters to realize that top speed is not even achieved until approximately 60 meters.
As coaches our interest is not in top speed but, rather in acceleration, the zero to sixty of the auto world. How rapidly an athlete accelerates will determine success in team sports, not what the athletes absolute speed is.
Why does this matter?
A great deal of the research on speed development focuses on speed in a track and field context and not in a sport context. In track the shortest event is the 55 meters, in sport the long event is a forty yard dash (although baseball will go to 60). The track influence may in fact have a limited application to sport due to sports frequent use of acceleration mechanics versus speed mechanics and the lack of true sprint positioning in most sports.
In training for track, coaches frequently make reference to the pulling action in running and work on drills to develop a pawing action against the ground. In sport the action is primarily pushing with the center of gravity slightly ahead of the feet, kind of a reverse Michael Johnson. This may mean that much of what we currently view as speed development may have limited application to team sport athletes.
Numerous studies have discredited the weighted sled as a tool for speed development citing the sleds limited effect on top speed. In truth, the evidence that weighted sleds may not improve top speed running, does not apply to acceleration and may have led us to undervalue a potentially valuable piece of equipment. In fact many authors who have stated that the weighted sled did not improve speed, do indicate that it will improve acceleration.
Our problem has been that we misinterpreted the results of the research. Most coaches spend time working on form running and technique to improve speed. These same coaches also include lower body strength workouts to improve strength.
Although these are both obviously important there may be a missing link. The development of specific strength. How often do we see athletes who run "pretty" but not fast? In my opinion many coaches attempting to develop speed spend far too much time on technique drills and far too little time on developing the specific power and specific strength necessary to run faster.
In fact in 2000 The Journal of Applied Physiology published an article called Mechanical Basis of Human Running Speed. The article synopsis begins with the line "faster top running speeds are achieved with greater ground forces, not more rapid leg movements". This has become known as the Weyand study after lead researcher Peter Weyand. Weighted sled drills target the specific muscles used in sprinting and seek to help bridge the gap between form running drills and weight room exercises like squats and Olympic lifts.
Many athletes can squat large amounts of weight. Far fewer athletes seem to be able to run fast. Any student of speed will tell you that many of the strength exercises commonly recommended for speed development work hip extension but, not hip hyperextension. The ability to apply force to the ground and create forward movement can only occur when the foot is placed under the center of mass and pushed back. Although squats etc. will train the muscles involved, the training is not specific to the act of sprinting. This may be one reason we see a higher correlation to vertical jump improvement than to speed improvement through strength training.
A weighted sled teaches strong athletes how to produce the type of force that moves them forward. The sports scientists like to break this down into special strength and specific strength. Although I believe the difference is minimal. It is important to understand the difference between the two quantities.
Special Strength - movements with resistance that incorporate the joint dynamics of the skill. Sled marching would fall into the special strength category. I believe that sled marching may in fact be the best tool available for speed development. An athlete's inability to produce force in the action of sprinting becomes glaringly obvious in sled marching.
Specific Strength - movements with resistance that are imitative of the joint action. I would place sled running in the specific strength category.
In the past coaches have recommended that resisted speed development work must not slow the athlete down more than 10% or must not involve more than 10% of the athletes bodyweight. These recommendations seem to be based on motor learning research that indicated that excessive loads would alter the motor patterns of activities like sprinting or throwing.
I have always felt that there was a missing link to speed development but, until a few years ago this so called "10% rule" kept me from aggressively pursuing my gut feeling. Presently, my feeling is that loads far exceeding an athletes' bodyweight can be used for special strength work as long as the athlete exhibits a similar motor pattern. Think of sled marching as a special type of leg press. Athletes incorporate the joint dynamics of sprinting through hip extension/ hyperextension against resistance. This can be an extremely heavy movement as long as we get a technically sound march action (perfect posture)
With sled running, the approach moves toward specific strength. In sled running the loads will obviously be lighter but, I still do not follow the 10% rule. The main variable in sled training is not the weight on the sled but, the motor pattern. If an athlete can hold an acceleration position and run without altering mechanics than this is a specific strength exercise for sprinting.
Why should we be limited by arbitrary guidelines like a 10% load or a 10% decrease in speed. Over twenty yards, ten percent is 2 one-hundreths of a second. The key should be to look at the athletes posture and motor pattern. If the athlete has to alter the mechanics to produce the desired action than the load is too heavy. The so-called 10% rule does not allow us to apply progressive resistance concepts to this form of training.
Another obvious but overlooked variable that alters the so-called 10% rule is the surface being run on. Loads placed on the sled will be lighter on grass and heavier on Astro turf. This simply relates to coefficient of friction. Less weight produces a large amount of friction as the sled moves through grass. On Astro turf or a similar surface, the same weight would be too light.
Another variable is a flat sled versus a double runner sled. A flat sled will again produce greater friction and as a result will necessitate a lighter load on the sled to get a similar effect. I have gone so far as to surf on towels indoors behind our athletes in a well-waxed hallway.
The reality is that we may have misinterpreted the message when it comes to resistance training for sprints. Although research shows that sled training may not improve the athletes ability to run at top speed, it will help the athlete to get faster. Remember, sport is about acceleration, not top speed. Very few team sport athletes ever get to the what track coaches like to call absolute speed mechanics. The sled may be the most underrated tool for speed development due to our misinterpretation and misunderstanding of the research and terminology surrounding speed development.
Below are some questions that were asked on the forum.
Q- 1 In what part of the workout should sled work be done ? Is it after speed work and before strength work ?
Our first two phases ( heavy sled pushes) are done after strength work and really would fall into the category of specific strength. In phases 3 and 4, we would either run sled sprints after our sprints and plyos ( and before strength) or, use them as part of a posterior chain complex in a complex training phase.
Q- 2 What would be the number of repetitions and distance for each rep ?
For heavy pushs we start with 4 sets of 20 steps ( 10 each leg) in week 1 and add one set per week ( 5 sets in week 2 and 6 sets in week 3) We have begun to prioritize steps vs distance.
Q- 3 Since MBSC does not follow the 10% rule ( using 10% of bodyweight on the sled) how do you determine the weight for a 1st time athlete using the sled ?
Think of the sled as set of 10 reps for each leg. You want steps 9 and 10 to be somewhat difficult in the heavy pushing phase.
Q- 4 – When you move from heavy pushes to sled sprints how do you decide how much weight to use in the 2nd 6 weeks. These are obviously with lighter weight? Do reps and distance remain the same ?
We do this by time. If we want to increase time by 10% we select a load that does that. That means the sled sprint should be roughly .2 sec slower than the 10 yd sprint. ( using an average time of 2.0 for 10 yds)
Q -5 Do you also incorporate sled marches into the workout ?
As mentioned in answer 1, Phase 1 and 2 are heavy marches, not sprints. There are no sled sprints in phase 1 and 2.
Q- 6 Should an athlete have a solid strength base before doing sled work or can anyone do it ?
Anyone can do it. As I said earlier, think of the heavy sled pushes as another posterior chain exercise. Charlie Francis used to use a reverse leg press done on an old Universal Gym to emphasize posterior chain. The weighted sled is just a better version of this.
Q- 7 What are your thoughts on doing light sled sprints followed by unresisted sprints for speed development. eg - 4 sled sprints followed by 4 x 10 meters all out unresisted sprints.
I would prefer to contrast in this situation. In other words, do one sled sprint and them follow up with a 10 M sprint. Do that four times
Q-8 At MBSC are all the sled sprints done with pushing sleds ? What are your thoughts on the sleds that you is strapped around your waist and the weight is behind you ?
For our lighter sprints we are switching to towing. So our heavy pushes will use the push sleds and our lighter sprints will use the towing sleds.
Q-9 Is there any particular reason you don't do contrast at MBSC in the 12 week program ?
The major reason is logistics. I worry about people pushing/ pulling sleds while others are sprinting.
Q-10 What are your thoughts on doing contrast sprints by sprinting 10 meters with the towing sled and releasing the sled and printing a further 10 meters ? I have seen this being done a lot with sprint athletes.
Again, there are two logistical issues.
1- You need specially designed harnesses for this.
2- You need a larger area than we have
Q-11 From your experience has contrast also benefited in development of speed in athletes?
To be honest, I think that is hard to answer? Most of what we do seems great in theory.
Q-12 Is it ok to do the heavy sled sprints with towing. We don't have much access to pushing sleds over here ?
A- We do not do heavy sled sprints. We either do heavy marches or light sprints. I think it's the in-between stuff that can be a problem.
Q-13 Do you do the sled work twice a week over 12 weeks ?
We do sled work 4 times per week for 10-12 weeks, yes. However only two days are linear. The other two days are crossovers.
Q-14 Is conditioning done soon after the sled marches in the first 6 weeks ?
Yes, we condition right after the heavy marches.
Q-15 So the first 6 weeks it's sled marches for all 4 days ? Week 7 to 12 I assume you do sled sprints twice a week on the 2 linear days. Is that correct ?
For the first 6 weeks it's 2 marches ( linear days) and 2 crossovers ( lateral).
I am not a fan of the sled as a conditioning tool.
We do sprint but, the loads tend to be in the 10-15% of bodyweight range.
Most sprint coaches feel that trying to sprint against a heavy sled can disrupt motor patterns. You want about a 10% differential which means for 20 yds sprints you would be slowed down by about .3 sec .
Q- 16. What about sleds as a conditioning tool or finisher?
As I said previously, we do some variation of push, crossover and/or sprint every day but, we don't like using conditioning against heavy loads. The exception in my mind might be football linemen as that is what they do?
Every other athlete uses primarily bodyweight in their sport. I feel like conditioning with a loaded sled is hard but, relatively non-specific.
When it comes time to condition we bike, run and slideboard.
Q- 17 When you say steps is it 1 right and left? Because if you progress to 5 stepsyou will push more with one leg then another? Would you do the same for crossovers? And the 30 steps for carries you count the same way?
It is steps per leg. We are just trying to find a way to equalize things. Using distance ( yards) favors the taller athlete. If we just say 5 steps or 10 steps per leg it is like doing a five or ten rep set.
Q-18 In Advances in Functional Training you indicate pushes, not drags. Is there a reason for not doing any dragging? I use it personally and find it a great upper back along with the quads and glutes. I use a Woss strap so I can get some distance between myself and the sled. I get low, keep the torso upright walking backwards. I also plant both feet and do a row, re-set and do it again. I also do a carioca lateral move with the straps with a light weight on the sled. I also work with some law enforcement people who at times have to drag objects off of roads or pull someone out of a vehicle. Since the book primarily is addressing athletes perhaps there is no athletic application to dragging/pulling.
I dislike dragging because of the prolonged lumbar flexion loads. I think in a general sense it's not good for you.
First responders might need small amounts for short distances but, very few first responders are dragging great distances.
I love pushes, am ok with harnessed forward pulls, I hate drags ( reverse), and love crossovers. PS- I can't see any reason for a carioca?
Q-19 I was trying to figure out how you'd get excessive lumbar flexion with sled dragging, because I have not seen that. I guess if you have a really short rope attached very low on the sled, it might cause it...?
I googled 'sled dragging exercise' looking for pictures/videos that might show it and happened to get a reference to a Ben Bruno blog post (from 2011): http://benbruno.com/2011/02/exercise-of-the-week-reverse-sled-drags/ I don't know if he still feels this way, but he certainly liked them then.
Just to be sure, we are talking about the same exercise, correct?
I know Ben likes them. ( and he's an MBSC guy). However, his client demographic is almost exclusively young, healthy and wealthy. In that crowd, done for short distance, with great form, it might be fine.
We do them with athletes particularly with knee issues but use belts vs. handles.
My concern is people putting it into adult fitness programs. Most adults live in flexion and don't need any more flexion.
It's important to realize that we are talking about flexion loads ( loads that pull with flexion forces)