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One of the pushes in strength and conditioning in recent years has been creating more functional lifts that attempt to mimic and enhance game/sport performance. The theory is that the more an individual task can be recreated in a gym or weight room setting, the more likely it is to carry over to performance on the field. One of the biggest drawbacks to the gym setting is that it is often too static to have enough carry over to a dynamic environment such as the playing field. In an attempt to create more dynamic environments, unilateral weights or single-leg exercises have been employed. These are often variations of traditional movements such as a clean or snatch. The explosive jumping and core stability that is incorporated in these lifts have been shown to be beneficial in increasing vertical jump (4) and other generic movements. Creating more sport-specific and situation-specific lifts by recreating similar force vectors may create more realistic and dynamic environments in the gym. This may help create “neural repetitions” (activation of the nervous system as similar to the actual activity as possible) similar to practice repetitions as well as train specific muscle groups needed to perform these activities at a high level.
Tackling in football is a specific skill that needs repetitions to be mastered. However, it is often not practiced for fear of injury. The single-leg squat/step-up with asymmetrical load bilateral bicep curl with adduction (D1 diagonal proprioceptive neuromuscular facilitation pattern) can mimic the force vectors seen in tackling. When analyzing a “head up” one-on-one tackle at the moment of contact, you will often find the tackler in single-leg stance with a forward body lean with arms flexing and adducting horizontally (from an extended and abducted position) to “wrap up” the ball carrier, all while continuing to drive the stance leg into hip and knee extension with ankle plantar flexion (from a dorsiflexed position). Then step and drive with the other leg. As a defender is often moving laterally to position himself for a tackle, his force vectors are often at a slight angle to the ball carrier and the desired resultant force vector, so using an asymmetric pull will also help mimic this situation.
The pulleys should be set at or below the height of the athlete's knee to create both vertical and horizontal resistances. To begin the lift, the athlete is standing on a box (6-8 inches tall), arms extended slightly behind the body, elbows slightly flexed, knee flexed, with a slight forward trunk lean (Figure 1). The weight in the contralateral upper extremity of the stance leg being squatted should be heavier than the ipsilateral upper extremity. The athlete extends the stance hip and knee while simultaneously flexing the elbows and shoulders with combined shoulder adduction horizontally. The athlete then steps through with the nonstance leg to create the “run through” or “leg drive” that is stressed with tackling. Emphasis should be placed on preventing medial rotation (caving in) of the stance knee and hip during the squat (Figure 2). Also, emphasis should be placed on keeping the head and shoulders up to protect against spearing and head first contact while bringing the hips forward. As the athlete's skill with the exercise progresses, the overall weight and difference between the contralateral and ipsilateral upper extremities should also increase. The weight should not be so heavy as to dramatically slow the player's motions. Although it may be a slow motion when first learning the exercise, as the skill and comfort of the athlete grow, the speed and cadence of the exercise should increase as well. This should be performed 2-3 times per week, 3-5 sets of 5-8 repetitions per leg. Once the lift has been mastered, the contralateral arm should use 50-75% of 1 repetition maximum (RM) for a unilateral bicep curl and the ipsilateral arm should use 40-60% of 1RM for a unilateral bicep curl.
This exercise is best performed using a double cable pulley system and can create a variety of angles and situations to recreate on the field situations. The situation previously mentioned is more of a “straight on” tackle or an “in the hole” tackle. Open field tackles or angle tackles can also be simulated, by rotating the box at an angle to pulleys (Figures 3 and 4). The ipsilateral arm is abducted more at the beginning of the lift and is adducted in more of a horizontal plane than the original lift, by raising the pulley on that side if possible. If only 1 cable pulley is available, the contralateral hand to the stance leg should hold the pulley and a lighter hand weight should be used in the ipsilateral hand to the stance leg (Figures 6 and 7). If cable pulleys are not available, free weights may be substituted (Figure 8). A further progression would be to use towels or pieces of jersey instead of handles to work on grip strength and the “grab cloth” mentality that is often stressed by coaches with wrapping up during tackling (Figure 5).
This novel lifting technique is designed to increase tackling performance by increasing the lower extremity power and increasing the rate it is transferred into the opposing player. The proposed benefits of performing a single-leg squat/box step-up maneuver are high levels of quadriceps contraction (2) and hip abductor and core musculature activity should be further increased with the heavier weight in the contralateral upper extremity. All these muscle groups should be trained to perform a tackle with decreased risk of injury and increased performance. Hip abductor and core musculature are important to increase conservation of energy. If the kinetic energy created in the lower extremities is dissipated throughout the trunk because of instability, the kinetic energy cannot be transferred at a high percentage into the opposing player and produce the desired result. Squats with resistance have already been shown to have a high electromyographic (EMG) activity for core musculature (5). Wahl and Behm (6) showed that athletes who are already highly trained in free weights or weightlifting did not increase core musculature EMG when moderate instability was added; however, this was done in double-leg stance. These results were similar in a study on bilateral upper extremity lifting with unstable platforms, but unilateral upper extremity lifting resulted in much higher core muscle activation (1). Thus, it is postulated that an asymmetrical upper extremity load and unilateral squat/step-up should produce a high enough level of neuromuscular challenge to elicit higher core musculature EMGs. Butcher et al. (3) showed that trunk stabilization and lower extremity strengthening for more than 9 weeks showed significant increase in vertical jump velocity versus a control group. By combining both high levels of core musculature activity and lower extremity strengthening, this lift may help with explosive power as well.
By recreating similar forces seen in the playing field in a way that is challenging to the neuromuscular systems, this should help create “neural repetitions” and enhance the player's power and performance for this sport-specific task.
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37: 223-231, 2007.
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22: 1522-1527, 2008.
5. Hamlyn N, Behm D, Young W. Trunk muscle activation during dynamic weight-training exercises and isometric instability activities. J Strength Cond Res
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© 2011 by the National Strength & Conditioning Association
6. Wahl M and Behm D. Not all instability training devices enhance muscle activation in highly resistance-trained individuals. J Strength Cond Res
22: 1360-1370, 2008.