(And really anywhere during multi-directional movement)
We see it all the time nowadays, on tennis courts and in many other sports…the bungee, positioned around the waist of the player as he or she performs multi-directional movements. And therein lies the problem. The resistance is being applied in one direction, while the player is moving in more than one direction. Furthermore, the force being applied is a sheer (i.e., lateral) force, pulling on the player’s mid-section. This is not a force a player will ever experience on a court, unless perhaps, they are playing during a hurricane.
The simplest way to explain “what’s wrong with this picture,” are lateral movements attached to a sheer force bungee. As the player moves in a lateral direction against the resistance, the case can certainly made that the resistance being generated is providing beneficial functional resistance as the player moves laterally against the resistance. It is not ideal resistance, because a sheer force applied against a player’s mid-section is disrupting his or her center of gravity, for which they must compensate as they are moving. So the neuromuscular feedback is programming the player a bit unnaturally, against a force they will never experience in a match.
(The lateral force disrupts the player’s center of gravity, often pulling them into a too upright position.)
And when the bungee is removed, and the player makes the same movements, the neuromuscular system must now adjust back to normal forces, essentially deprogramming what the resistance was just teaching the athlete. Are these conflicting stimuli helping or hurting the athlete? But granted, it can be argued that the benefits derived from the lateral force more than offsets the fact that the neuromuscular stimuli of the bungee is not exactly consistent with what the player experiences when the bungee is removed. So some coaches may feel that “it may not be precise functional resistance training, but it’s better than not doing it.”
Fair enough. But where that logic breaks down completely is when a player changes direction, and is no longer moving directly against the resistance. The worst case is when they move directly back in the direction of the resistance. Now they are being taught to be worse movers, not better, slower, not faster. If you slow down the film of any lateral bungee drill, it becomes clear that with each stride, now being pulled, not resisted, by the bungee, the player’s body position is backwards: He or she is now leaning away from the direction they are going, and with each stride they are bracing against the resistance, actually breaking with their lead foot, otherwise they’ll get pulled over by the resistance.
[Just when the player should be pushing off her outside leg to propel her back to the center of the court, she is leaning away from the resistance, breaking with her inside leg against it]
And at the most important moment of all, the moment they are changing direction, at the exact moment you want resistance to reverse, and be applied away from the center of the court, the bungee is assisting them, actually making it easier to change direction, not harder. The training effect as they change direction is not only lost, it is diminished. These drills are not helping the player change direction and get back to center court faster. They are actually programming the player’s neuromuscular system to do the opposite of what it should be doing.
[Instead of applying maximum force to her outside leg to train her deceleration and change of direction, the resistance is assisting her, diminishing the training effect]
A similar phenomenon occurs with movement in any direction that is not directly opposite the direction of the sheer force. The player’s neuromuscular system must respond, not only to the natural forces placed upon them as they propel themselves in the direction that want to go in, but it must also adjust to the unnatural sheer force being placed upon them, which can disrupt posture and balance.
Faster, more efficient movement in any sport is a function of the neuromuscular system’s ability to work as one to accelerate, decelerate, change direction and accelerate again in the opposite direction. If there is a positive training effect, which most agree there is, from applying resistance to sport-specific movements, then that resistance must be applied consistently, continuously and always from a vector consistent with what the athlete would actually experience when the resistance is removed.
If functional resistance training is designed to reinforce and amplify the neuromuscular connection, which allows both brain and body to work together to move more efficiently, then any forces which are applied to an athlete’s movement patterns, which send conflicting or downright counter stimuli, are not accomplishing the fundamental purpose of functional resistance training, and is likely doing more harm than good to your athletes.