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This summary was written by Richie Mercado.
>> Click here (or right click and save as) for the Neuro-Biomechanics of Maximum Velocity paper (17 pages, PDF format)
Neuro-Biomechanics of Maximum Velocity
by Loren Seagrave
Videos of High Level Sprinting
Loren Seagrave then showed some video of sprinters to focus on aspects of sprint mechanics. The first example was of Andre Cason one week prior to 1992 Zurich meet. He said that most people would see a little short guy running fast! Coaches and observers do not have their minds ready to analyze and break down the key components at regular speed, so he froze certain frames and slowed down other parts.
Important in understanding sprinting are the Cyclical Movement Phases: these occur over and over and over again throughout the course of a race! This is much different from an acyclical movement; the quality of each one of the phases of the movement depends on the quality of the phase that precedes it. The ground phase is the most important, yet the quality of the ground phase is determined by all phases that come before it!
Residual Phase – from the moment the toe leaves the track (T.O.) until the thigh begins moving forward in recovery.
Recovery Phase – from the moment the thigh begins moving forward until the thigh stops (blocking)
Transition Phase – from the moment the thigh blocks until the thigh begins to accelerate in a negative direction.
Ground Preparation Phase – from the acceleration of the thigh in a negative direction until touch down (T.D.).
Frontside Ground Phase – From the instant of T.D. until the COM is over the base of support (contact point of foot).
Backside Phase – from the midstance of support over the foot until the Takeoff (T.O.) into the next Residual Phase.
Vital to the development of maximum velocity sprinting skills is a proper understanding by coach and athlete of the following: there is a big difference between quality and intensity. Intensity is the % of maximum, say 90% of Vmax (90% of 10meters/second = 9meters/second). Quality is a measure of the % of perfection – even if not done at 100% of intensity! There is no excuse to do any work at less than 100% of quality, no matter what speed or intensity.
The practical applications for coaches and athletes developing the appropriate skills in each of these phases include neuro-biomechanical cues to allow for proper positioning and muscular response in the cyclical phase.
The prime example comes in the transition into the Residual Phase, where the brain must send the message to dorsiflex the foot before T.O. into the Residual Phase. German studies have shown EMG messages occurring while the foot is still in contact prior to T.O. At T.O. there is stored elastic energy if the foot is dorsiflexed, thus reducing the amount of time required to recover the leg (i.e. get the thigh and leg moving forwards sooner after T.O. to save time in the Recovery Phase.
The cue for therapists when reteaching someone to walk is not to lift the knee, but lift the top of the foot! This evokes the “triple response”; by curling the toe up (lifting the top of the foot) the knee and hip also respond! Those with too pronounced backside mechanics and slow recovery do not send this message of dorsiflexion soon enough. Since recovery requires velocities of over 400 degs/sec, the smaller muscles must do it, not the larger ones.
The Gastrocnemius (begins above the knee and goes down to achilles) becomes an extremely fast knee flexor! Joint position dictates muscle recruitment (this is the Speed Dynamics principle), with dorsiflexion of the foot and other joint movements. If one raises their arm and holds their biceps, then rotates the palm, it is obvious that pronation turns on, and supination turns off the biceps (this is why it is easier to do closed-grip rather than open-grip pullups).
In cyclical motions, part of time muscles must contract, and part of the time they must relax. Hip extension from ground contact through the Drive Phase is vital, and requires hamstring contraction. If the hamstring contracts during the Recovery Phase then it does not have time to relax, and the result is either premature fatigue or worse, injury! By reducing the moment of inertia through dorsiflexion of the toe, then Recovery is quicker and allows the hamstring to relax and recover for the next contraction during the Drive Phase.
When young people learn to bat in baseball and they swing the bat too slowly to hit the ball, the appropriate adjustment is to choke up on the bat and thus be able to swing faster. If the length of the leg is shorter, then it too can swing faster! The same principle also works in sprinting. Just before the Transition Phase – when the thigh blocks – coaches will often observe athletes floating in the air in a blocked motion. The legs work in concert and in opposition, so a blocked leg cannot go down until the opposite leg begins to move forward – in other words, they need to work on the Recovery Phase to enhance the Transition Phase! Coaches can drill athletes to use a maximum acceleration of the hip flexors and a maximum deceleration of hip extensors by means of a fast leg drill.
Coaches and athletes must understand and identify key regulatory factors (Maraj) that are going to limit performance and develop learning and skill routines that will enhance sprinting skills. In this fast leg drill, the cues are for the athlete to get the ankle cocked and step over the opposite knee to thigh block, then accelerate the thigh backwards into extension. It must be a short lever: shorter = faster!
Athletes can control when they send the neurological message to the quadriceps to extend the knee. Insure that the quad muscles stay relaxed, and remember that the lower leg stays in the same position and neither adds to length or mass of the leg lever. Sprinters should first accelerate the long lever, then accelerate this long lever against the ground by contracting the quadriceps. According to Mann, top sprinters maintain a lower angle longer, thus maintaining greater speed at the knee and foot going backwards. There are also smaller distances from the COG to TD in elite sprinters; beginners have bigger distances, thus creating greater breaking forces and loss of Vmax with each TD.
The cue should be to keep the ankle cocked (dorsiflexed) thus preparing the Gastrocnemius and Soleus muscles for contact. This muscular resistance upon TD will reduce amortization (collapse and loss of energy) prevent the toe pointing down, which tends to place TD even farther in front of the COG.
The stretch reflex from dorsiflexion turns the ankle joint into a mechanism akin to the horse’s fetlock joint: no muscles cross the joint, just a thick non-elastic ligament. The gastroc-soleus-Achilles complex in humans stores energy and projects us forward more quickly, minimizing amortization.
Another cue to look for as a coach is the angle between the thighs at the moment the foot touches the ground. The knees should be at least together: an excellent measure of quality and perfection of leg recovery mechanics. If there is light, i.e. some angle between the legs at TD, then a forward TD and braking is occurring, thus Vmax is reduced. In drills, sprinters should shift the hip forward – this avoids stress on the ham from hip back. The shoulders should remain directly above the hips, and the athlete should use the lower two abdominals to stabilize the pelvis (the upper four are used for breathing). This is a skill, and like any it can be unlearned and overridden by bad technique!
The sprinting action can be practiced in a Whole Method by maintaining a stable and upright torso, then dorsiflexing the foot (thus initiating the triple reflex of the ankle-knee-hip joints), then drive the thigh down and grab back into the ground and end up tall with the hip over the knee. Excellent strength exercises that will enhance the specific strength of the sprint cycle are squats, lunges, stepups, and bounding.
In sprinting, arms are like operating a vehicle on a one way street – they only drive one way – backwards! The arm action should take place in a loose 90% angle, with the athlete driving the arm back to store elastic energy in the shoulder and biceps. Do not paddle with the hand palm-down, because it will relax the biceps!
Some important drills to teach sprinting skills include:
Ankling – maintain body position (posture) and dorsiflexion(keep the bottom of the foot pointing down to the track and do not push from the ankle) while stepping over opposite ankle!
Cue – tie your big toe up to your knee joint! use tape and FEEL the proper movement! There may be a problem: the new, more optimal way does not feel right, but it is vital to feel it anyway.
Butt Kicks – dorsiflex ankle, use gastrocnemius as the knee flexor (initiate the triple flexor response), preserve good body position and proper pelvic tilt, crash calf into ham and see knee move forward ever so slightly as knee is flexed. One athletes described it as trying to comb their hair with their spikes! A Series – dorsiflex ankle (initiate the triple flexor response) and block thigh, then accelerate.