Playing the offensive and defensive line in football requires size, strength and guts but returns very little glory. For a lineman, almost every play is a battle of standing combat.
Whether your job is to protect the quarterback or flatten him like a pancake, size and strength matter. That's why the Sled Push Pull is such a great exercise. Execution requires high force and explosive power output, the same attributes you need on the line of scrimmage.
I can sum up the importance of the Sled Push Pull in two words: dynamic correspondence. Dynamic correspondence exercises enhance performance by simulating the amplitude, direction, force production, movement dynamics and muscular contractions of the movements you make on the gridiron. 
Why the Sled Push Pull is a dynamic correspondence exercise
Direction of the movement. Unlike seated or prone exercises like the Bench Press, the Sled Push Pull is performed standing, mimicing the direction of a tackle. Did you ever lie down on the line of scrimmage and bench-press a running back? Probably not.
Increased force production. The pushing or pulling done during this exercise works your body in a motion similar to making a tackle. Force also involves using a load (e.g., weight) similar to what you encounter when tackling. So if you need to be able to tackle a 200-pound wide receiver, using similar loads will increase your sport-specific transfer.
Speed of Movement. You need to be explosive on the field, so you need to train explosively. A Pull-Up does not come into play when tackling, whereas an explosive pull does.
Muscle Contraction. Tackling requires you to use type II muscle fibers, the ones for power and explosiveness. To recruit these, you need to train explosively. If you train like a marathoner, your muscle fiber types (type I, the slow twitch fibers) respond, adapt and grow. The Sled Push Pull requires power and explosiveness. This makes your explosive muscle fibers (type I, fast twitch fibers) respond, adapt and grow. (Learn more about the difference in STACK Science: Developing Slow- and Fast-Twitch Muscle Fibers.)
How to perform the Sled Push Pull
- First attach a rope to a sled with a weight load that resembles what you will be facing on the field (see below for weight selection guidelines).
- Linemen should start in a squat stance (like you would assume on the field).
- Other defensive positions (e.g., tight end and corners) set up in a lunge stance.
- These variations are examples of amplitude of movement and will transfer better onto the field.
- Start with hands on sled in front with body at 45-degree angle
- Powerfully drive legs to begin sprinting
- Push sled as fast as possible for around 30 meters
- Immediately follow with a Sled Pull
- Grasp rope handles and assume an athletic stance
- Lean back slightly to remove slack from the rope
- Jog backward to start
- Maintain a steady position and do not change your body angle
Sets/Reps/Distance: 3-5x2-4x30 meters
For ultimate conditioning, time your rest periods to conform with the intervals between plays (the average time between football plays is 32 seconds).
Weight Selection Guidelines
As mentioned above, you want the load on your sled to resemble the weight you face on the field. If the weight is too low, you will not develop enough force. If it's too high, your biomechanics will change and the exercise will not really be a dynamic correspondence exercise. Large loads often greatly alter movement biomechanics, which, in turn, reduces the efficiency of the exercise .
You can achieve similar benefits by performing a Standing Cable Push-Pull combination! Use a single hand attachment and rope.
This exercise has a time and place, just like everything else in a well-designed strength and conditioning program. I use it during the pre-season in my "explosive strength and power" phase with my advanced athletes. This phase happens immediately after an off-season of developing functional movement, hypertrophy and strength.
You need to have sufficient physical attributes (e.g., strength), optimized skill techniques (e.g., functional movement patterns), and the right neuromuscular adaptations before attempting the Sled Push Pull. If you go for it before you are fully ready, your long-term athletic development will suffer.
 Myszka, S. "Hot topic: Dynamic correspondence - the key to strength training transfer." National Strength and Conditioning Association. (Retrieved online on 06/22/13 at http://www.nsca.com/ContentTemplates/PublicationArticleDetail.aspx?id=2147486471 06/22/13.)
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