TriathlonResource.com |
|
All You Need For Swim, Bike, Run |
|
Creating Efficient Horizontal Propulsion © 2008 by Ken Mierke
Despite what most runners and their coaches believe, technique plays an enormous role in sustained fast running. Most runners subscribe to one of two basic paradigms of propulsion. Unfortunately, both are flawed. One creates more upward than forward propulsion; the other isolates a relatively small, weak muscle group instead of harnessing a number of muscles to work together to produce propulsion. Learning to use large muscle groups to create horizontal propulsion with minimal vertical oscillation will help you run further and faster.
Upward Thrust Method
One challenge for runners is creating propulsion as close to purely horizontal as possible. Excessive vertical displacement increases the energy cost of running dramatically. Most runners develop propulsion using the upward thrust method. At toe off, the knee is straightened forcefully, thrusting the body up and forward.
This technique wastes a tremendous amount of energy, leads to local muscular fatigue in the quadriceps, and slows turnover. It also increases impact stress which leads to more injuries.
As indicated by the large black arrow in the illustration, the direction of the force created by extending the knee is slightly forward, but mostly upward. The extended flight time decreases turnover, more than offsetting the slight increase in stride length, resulting in slower running speed and increased energy cost. This up and down method of running, employed to some degree by most runners, is extremely inefficient. If your quadriceps fatigue during long runs even at easy pace, you probably use the upward thrust method of propulsion.
The quadriceps muscles work primarily vertically. On flat ground, the quadriceps should only contract at the moment foot-strike to hold the body up. They minimize knee bend at foot-strike, catching bodyweight, but should not create propulsion. This is especially important for triathletes, who must run with quadriceps fatigued from the bike.
Pull Through Method
Another common error of propulsion is the pull through. This runner avoids the upward thrust push-off, instead creating propulsion by bending the knee and pulling his body forward with the hamstring muscles. This running style is reasonably energy efficient; it does minimize vertical displacement and landing impact. The problem with this running style is the demand that it places on the hamstring muscles.
The hamstring muscles are a relatively small and weak muscle group. When they are almost exclusively responsible for propulsion, they fatigue easily. Using larger muscles, along with the hamstrings, enables a runner to take advantage of the benefits of the energy-efficient (horizontal) style, but prevents local muscular fatigue in the hamstrings by spreading the workload over greater muscle mass.
If an athlete suffers from hamstring fatigue or cramping during long or hard runs, while the rest of the body feels fairly comfortable, he probably uses pull-through propulsion. Learning to engage more and larger muscles for propulsion while maintaining the horizontal movement will increase speed and endurance.
Foot Drag
The two common errors of creating propulsion for running involve movement at the knee. Using optimal technique for creating propulsion when running on flat ground, a runner neither straightens nor bends the knee, instead pivoting from the hip using a movement called the foot-drag.
Efficient runners pivoting the leg backward from the hip with the entire leg as a fixed unit. The knee should be slightly bent, but the knee angle should not change from just before foot-strike, through the period of contact with the ground, to the follow-through. Through the entire propulsion phase, the knee angle should be slightly bent and should nt change. This technique accomplishes a number of the goals of efficient, fast, sustained running.
First, the foot-drag movement creates almost perfectly horizontal propulsion. Vertical displacement, and all the problems associated with it, can be minimized. Newton’s Law states that “every action has an equal and opposite reaction”. It follows that, to create horizontal propulsion, we must pull straight back against the ground instead of pushing down into the ground. The foot-drag movement accomplishes this goal.
The foot-drag movement also takes advantage of the attachment points of the muscles on the posterior aspect of the hips and thighs and spreads the work of propulsion among a much larger muscle mass than other methods of propulsion. Using greater muscle mass to accomplish a certain amount of work decreases the relative intensity of the work for each muscle. If more muscles are doing the same amount of work, each muscle is working more easily.
The hamstring muscles are unusual in that they cross two major joints. The hamstrings attach above the hip, cross both the hip and the knee joints, and attach below the knee. Due to this unique attachment, they serve two major functions: extending the hip joint and flexing the knee joint. The gluteus maximus muscles, on the other hand, cross only one major joint, the hip. The glute muscles only major action is hip extension.
The pull-through method of propulsion creates nearly horizontal propulsion, but it fails to engage the largest and strongest muscle in the body, the glutes. Which do you think would be stronger, your hamstring muscles, or your hamstring muscles and your glutes working together? That answer is obvious. If knee flexion is the primary producer of propulsion, the hamstrings have to create the force by themselves. By using hip extension instead of knee flexion to create propulsion, the hamstrings work in conjunction with the glutes, therefore each muscle is required to produce less force. Obviously, this minimizes fatigue.
Pull-through runners frequently have extremely tight hip-flexors, preventing correct hip extension. Stretching these muscles will enable you to incorporate better technique for developing propulsion, allowing you to create high levels of horizontal propulsion without local muscular fatigue.
Developing a stride which uses hip extension as the primary method of propulsion will enable runners to move more horizontally and to use large muscle groups to do the work. This will allow you to run farther and faster that ever before.
Ken Mierke is author of The Triathlete’s Guide to Run Training and Evolution Running: Run Faster and Farther Without Injury ( due out 2008). Ken developed of Evolution Running, a system of running techniques that increases efficiency and injury resistance. Ken coaches several of the fastest runners in the sport of triathlon. Ken is Head Coach of Fitness Concepts www.Fitness-Concepts.com. His book, DVD, and even schedule are available at www.EvolutionRunning.com
===============================================================================
Maintaining High Turnover When Running Slowly © 2005 by Ken Mierke
Running with high turnover (at least 180-182 foot-strikes per minute) increases running efficiency and reduces the risk of injury. Many runners maintain high turnover during tempo runs, track workouts, and races, but fail to do so when running at a basic endurance pace. Learning to maintain the same turnover when running at any speed will improve your training and racing.
Elite runners of any height and leg length, generally run with a cadence between 180 and 182 steps per minute. Watch the lead pack in a road race the next time you get the opportunity. You will be amazed at the incredible synchronicity of the runner’s strides. Efficient runners of significantly different height and leg length consistently chose almost identical turnover rates. Why would a 6’2” professional runner use the same turnover rate and significantly shorter stride length (proportionate to height) than a 5’4” runner?
One major reason for this is caused by the nature of the elastic responses of human tissue. At a given pace, longer strides mean more contact time with the ground. This reduces the benefit of elastic recoil, causing the muscles to contract more forcefully. Even though a taller runner’s legs may be longer, his elastic tissues respond just like shorter runners’. When human tissue is stretched and released, it snaps back forcefully. This enables runners to store energy in the Plantar Fascia, the Achilles tendon, and the Soleus and Gastrocnemius muscles from one stride and return that energy as propulsion in the next stride. Optimal use of elastic recoil is a major difference in efficiency differences between runners.
Runners’ tissues snap back forcefully when stretched and released, but they do not when stretched and held, even for a very short time period. When the stretch is held, even for a fraction of a second, the stored energy dissipates, resulting in far less energy returned as elastic recoil. The taller runner must take strides that are proportionally shorter (compared to leg length) in order to keep contact time between the feet and ground short to enable the energy return from elastic recoil.
The second reason is that a longer stride necessitates greater vertical displacement. If I wanted to throw a baseball 20 feet, I could basically throw it on a straight line without much arc. To throw the ball 50 yards, however, I would have to arc it upward, because gravity would have a long time to act on the ball. In the same way, running with long strides forces runners to move up and down more than shorter strides.
Longer strides also require the muscles to contract more forcefully to create horizontal propulsion. First of all, to cover 20% more ground, even with optimal efficiency, 20% more force at push-off would be required. Factoring in the need for vertical displacement and the loss of power from elastic recoil, and the increase in force required at push-off is staggering.
Contracting muscles more forcefully fatigues them far more than contracting them frequently with less force. Each of our muscles is made up of thousands of different muscle fibers. These muscle fibers fall into two basic categories (though there are also several sub-categories), slow-twitch and fast-twitch. Fast-twitch fibers are tremendously powerful, but fatigue very quickly. Slow twitch muscle fibers have tremendous endurance, but are not very powerful. One major problem with taking long strides is that the slow-twitch fibers are not able to provide the majority of the power required for push-off and the fast-twitch fibers are required to contribute significantly. Running with longer strides and slower turnover requires much more power at push-off than the slow-twitch fibers can produce. This means the fast-twitch, sprint muscle fibers must contract to make up the difference, which leads to lactic acid accumulation and premature fatigue.
Running with a slow turnover requires increased vertical displacement, greater contact time with the ground, and more forceful contractions at push-off, all of which impair economy and lead to local muscular fatigue and greater risk of injuries. Improving this aspect of technique pays big dividends.
Our research has shown that, for durations of the range of triathlon race durations, optimal turnover is about 180 – 182 steps per minute, regardless of running speed. This is considerably higher turnover than most runners naturally use, especially on long, slow runs.
Learning to keep turnover higher on your easy runs is a critical part of efficient training. Good cyclists keep cadence relatively high even on an easy zone 1-2 ride. Keeping turnover high on easy runs is even more important because slow turnover training does not effectively train the elastic response that you need to run your best on race day. If a runner uses slow turnover for basic endurance training, he/she is asking his/her muscles to create force on race day in a way that has been trained for a small fraction of training mileage. That is not the way to produce optimal results.
Running with quick, short strides is unnatural for all runners, but especially for taller runners, who have been told to take advantage of their long legs by using a long strides. To gain the “free speed” of elastic recoil, tall runners must use the same high turnover as shorter runners. This means they must learn to use steps which seem proportionally shorter for their leg length. I have had tremendous success teaching tall runners to take quick, short strides and increase their efficiency. My wife, who is 6 feet tall, learned to run with high turnover and as a result won a triathlon national championship, turning in the fastest run split.
Certain biomechanical techniques are key to increasing turnover to maximize efficiency. Efficient runners have no pause at the completion of the leg’s follow through. The leg pulls back to provide propulsion and then immediately the knee drives forward. Leg recovery must be initiated as the leg is still moving backward in follow through from the propulsive phase.
During leg recovery, the knee is driven forward powerfully by the hip flexor muscles at the front of the upper thigh. The forward movement must be quick and powerful, with full knee bend, but the range of motion of leg recovery must be very short. The forward knee drive is completed when the knee is only slightly in front of the hip and the foot is directly beneath the knee.
The foot lands directly beneath the hips to prevent braking, instead of landing out in front.
Contact time between the feet and ground is minimized.
Push-off is not created by forceful contractions, but by light, quick movements. Bodybuilders don’t win 10Ks or marathons.
Extend the knee and foot well behind your hips, but never very far in front. Your feet should stay under and behind you all the time, even at slow paces.
All this is accomplished while maintaining relaxation.
Make sure that you do not attempt to increase turnover by pulling the leg back faster during the weight bearing phase of running. That will increase both turnover and stride length, leading to incorrect training intensity and possibly premature fatigue. That isn’t efficient running; that is going too hard. Work toward a significantly higher turnover with slightly shorter steps and you will increase speed without increasing energy expenditure.
Many of the athletes we coach use metronomes during running. A modern metronome is just slightly larger than a credit card and will beep at any rate you set it for. (Most music stores carry these devices) We usually have runners determine their natural turnover and gradually increase it over time, with the ultimate goal being approximately 180 steps per minute. We generally have runners increase turnover by three to five steps-per-minute each week until approximately 180 steps per minute feels natural.
Learning to run in a relaxed manner at high turnover with short to moderate stride length takes concentration, effort and patience, but these techniques will help almost every runner to maximize efficiency and minimize the risk for injuries. Take the time and effort to evolve your running and you will run faster with fewer injuries.
Ken Mierke,author of The Triathlete’s Guide to Run Training, is a two-time World Champion triathlete (Disabled Division, 1997,1998) an exercise physiologist, and developer of the techniques of Evolution Running. Two of Ken’s clients won world championships in 2005 and he has coached 13 National Champions and 28 Team USA athletes. Find more about Ken at www.Fitness-Concepts.com or www.EvolutionRunning.com
|
