Running in humans has been described as “controlled falling”. It is accomplished with a coordinated combination of stride length and stride frequency in the lower limbs, with balance and stabilization help from the upper limbs. Over the past century there has been considerable scientific effort put forth in understanding the nervous system control of both stride frequency and stride length in achieving the individual’s optimum balance points in achieving greater velocity in running From this effort, humans have gained substantial understanding of the mechanisms involved in generation and regulation of the rhythmic alternating pattern of muscle flexion and extension that is required to propel the body forward, swing the legs to the next foot location, and regulate the transitions between these states. An inability by the runner’s neural system to maintain ideal balance limits the capacity for optimum stride length in forward progression at mid to maximum velocity, such as VO2 max pace. Stability and balance achieved while running at VO2 max pace is achieved through reactive and proactive strategies to control the motion of the center of mass and formulation of the next base of support. Sensory input will in effect, regulate stride length, as the body continues to struggle for balance and stability as the center of mass passes over the supporting limb.
When an endurance runner becomes more efficient through training, running economy improves. The body creates its own combination of stride length and stride frequency to achieve the desired velocity at the least amount of metabolic cost.
It has been shown in high-speed motion analysis studies that too much time in the air and too much time on the ground hinder summative velocity in a runner. Time on the ground is regulated by stride rate. Time in the air is regulated by stride length. Studies by scientists have shown that for both sprinters and distance runners: reducing contact time, thus improving stride rate, is the key to improving performance. For a distance runner to reduce contact time by .02 seconds per stride would lead to marked improvement at any distance. The chief biomechanical means for achieving this reduction is to shorten the stride length, thus reducing braking forces.
Stride length in the 100 meter race is shorter than the 400 meter race. Stride rate is more crucial than stride length in this race, and a faster stride rate follows a shorter stride length. However, as the runner shifts from sprinting to distance running, there is a shift from power to economy, and the stride will lengthen to reflect this change. This inevitably leads to some braking forces in distance running that are not present in the 100 meters.
Identification of proper stride length to minimize braking forces by the athlete is a coaching demand. Front-side mechanical improvement is essential. This can be achieved through core strength improvement, joint mobility increases, and drills designed to improve balance and stability such as lunges, craning, and limited bounding. Distance runners need to learn active recovery after foot take-off, or there will be too much backside extension of the take-off leg. If extension occurs, the trunk will lean too far forward and the runner’s arms will also extend too far forward in order to maintain balance. This will create too much time in the air during transition from take-off to toe-down.
If distance runners were to do training sessions of maximum velocity work, such as flying 30 meter repeats, they would learn to move their weight further forward on the foot, thus helping to reduce ground contact time, breaking forces, and ultimately over-striding. They would get faster.
The positioning of the trunk in order to achieve proper balance is also a developmental skill. Leaning back too far does not allow for extension of the lead foot and will create under-striding. Again, maximum velocity work will naturally improve this posture as the runner’s sensory input tries to locate proper balance.
The real practice key may be the use of more barefoot running on grass surfaces. This type of physical demand will promote hypertrophy in the many foot muscles, as well as greater dexterity in the Achilles tendon, and create a stronger push-off while leaving the ground. This action will create a quick, efficient stride pattern that will not cause metabolic fatigue to occur as rapidly. Prescribing a session once per microcycle of barefoot running in the Special Endurance 2 category, such as 6 x 500 meters would be useful in building foot strength for a stronger toe push-off by an endurance runner.
The human foot has rightfully been called the most characteristic peculiarity in the human body. We are the only primate to give up the foot as a grasping organ. This was a huge evolutionary sacrifice. The human foot is designed to only do two things, propel the body forward and absorb the shock of doing so. Bipedality has freed the hands, but it has yoked the feet. Sophisticated running shoes have taken natural shock absorption away from the foot and caused atrophy of the foot muscles which has hindered strong toe push-off. This hinders the stride pattern of the runner and thus the metabolic economy of the effort. With greater use of barefoot running in practice at a fast pace, the athlete can improve the action of the foot in a better biomechanical running technique.
Again, this is another principal I learned from Vasily Grischenkov back in 2003, and I use it with my kids at least once per week at the end of a session to complete a few 150s or 200s on grass. It's actually pretty refreshing too.