The athletic component of agility is, both figuratively and literally, multi-dimensional. The uneducated coach spreads out a bunch of cones, hurdles or ladders and gets their players to move around/through/between/over them in some pattern that they saw on a video, or used to do when they were players. It often looks cool, and can be fun for the players, but such a haphazard approach does not do much to making them more agile. Sure, they may get a bit quicker at that obstacle course, and might see some improvements in dynamic balance. But their ability to produce speed in three dimensions is not enhanced, because they do not improve their ability to generate and absorb forces with this careless training like this1. A more systematic approach to developing the component movement skills, and neuromuscular output is necessary to improve athletic agility.
Putting aside changes of locomotion (shuffling, backpedaling, crawling, hopping, jumping, diving, sliding, rolling, etc.) for another time, this article will look at agility that is exclusively comprised of sprinting along multiple paths.
First a distinction must be made between a redirection and a change of direction. A redirection is less than 45°, and a change of direction is 45° or more. Why? Trigonometry. Assuming you have some momentum generated and are actually moving with some speed and purpose in the initial direction2, a breaking force is required to change that direction by more than 45°. Without that braking force, you cannot generate a lateral force that is large enough to disrupt the path of travel by more than 45°.
REDIRECTION
Redirecting can be —and is often best done— without loosing speed: a lateral force is added to the forward motion. This propulsion can be applied at any angle up to 90° relative to the current path of travel (resulting in a deflection in motion up to 45°). If the redirection is initiated while in the flight phase, it is achieved by aiming the next footfall to the side of the centre of mass (COM) away from the intended direction of movement. This is usually accompanied by a lean (rotation of the body in the frontal plane) towards the new direction.
If the redirection is initiated during the ground contact of the foot away from the new direction, its hip abductors and external rotators will increase activity to push in the COM to the new direction. Conversely, if the foot in contact is the one towards the new direction (inside leg), its hip adductors and internal rotators increase activity.
From a defensive perspective, redirection is often used to close down space, or to steer an opponent. Offensively, redirection is used to evade an opponent or obstacle while still advancing towards the target. It is also what happens when running along a curved path, which is actually a series of redirections.
CHANGE OF DIRECTION
On the field and court, changes of direction are involved when executing (or defending against) jukes, cuts, fakes, as well as upon reacting to a sudden change of possession. To change direction, the initial forward motion must also be slowed, so ground contact must occur in front of the COM. This is the only way to get beyond a 45° deflection in motion. When this deliberate over-stride is done properly, forward momentum is absorbed through eccentric muscle contraction along with the series and parallel elastic components. When done improperly, ligaments are stressed instead of the muscle-tendon complex, therefore little energy is conserved. This can also be dangerous when ground contact forces are higher than planned, such as when traction is better than expected, or the athlete is off-balance.
With optimal technique —and provided the athlete has developed appropriate levels of strength and power— most of this energy can be returned through the stretch-shortening cycle (SSC) during the rebounding concentric phase3.
Concurrently, a combination of synergists are recruited to direct that returned energy, and the COM, along the new path. As such, the braking force of the change of direction is not wasted. Consequently, the athlete moves faster and with less energy. Furthermore, there is no trade-off between minimizing injury risk and maximizing performance outcomes, because the optimal biomechanics are the same.
Obviously changing direction demands more power than redirecting due to the greatly enhanced eccentric component. It also necessitates the coordination of more complex movement patterns. A deficiency of either is a non-contact injury waiting to happen, which underscores the importance of first using preplanned agility drills for teaching and developing these abilities prior to adding reactive components to agility training4.
Do you know what the optimal techniques for redirecting, and for three-dimensional changes of direction are? Is it the same on a basketball court as it is on a soccer pitch? What about when it is raining or the field is frozen? Is it different for tall players than it is for short ones? How is it influenced by sports equipment, like when holding a stick or racquet? How it is influenced by sneakers, cleats, or skates? We can teach you.
-CG
1 Take a look at where their head is pointing, their lousy posture, and how poorly aligned their extremities are —they can’t be expected improve their athletic abilities if they are not in athletic positions.
2 Even a single explosive step in the initial direction cannot be changed by more than 45° without a breaking force on the next step. This is because (barring any major asymmetry —like a para-athlete may experience, for example) the maximum force that either leg can exert in a single step should be equal. So the first step is already generating “some momentum”.
3 Some energy is inevitably dissipated as heat.