The Effect of Stride Length and Knee Rise on Efficiency in Runners  


Running Efficiency

Introduction | Method | Lab Setup | Results | Discussion | Links |
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Introduction | Go Up

Background Information: Running is one of the oldest sports known to mankind. Ever since the ancient Greeks have been competing in sports, we have been trying to figure out ways to run more efficiently, and people have tried everything from intense training to performance-enhancing drugs. What most runners don’t realize is that they can vastly improve their efficiency and speed by doing simple things like running a warm-up before a race or slightly modifying their form. Of course, if one is a novice runner, strong evidence suggests that the quickest way to improve speed and endurance is through a drastic increasing in the intensity of one’s training regimen. However, when a runner becomes more experienced, the evidence also shows that he or she will respond less to a mere increase in training.

Because I am a more experienced runner and wish to conduct a study which provides information useful to both myself and other experienced athletes, I am going to focus my research on aspects of running that “elite” athletes can improve on (outside of an increase in training). There are many such factors such as terrain, heel rise, body mass, body composition, caloric intake, running form, etc. However, many of these factors are also very difficult to measure accurately, impossible to assess in the time frame given, or are unpredictable. Therefore, I have chosen three aspects of running which are both easily measurable (using heart rate to determine an increase or decrease in energy use) and can be experimented within given time frame.

Statement of Problem: The purpose of my investigation is to discover what the effect of stride length, knee rise, and running a warm-up prior to vigorous activity (such as racing or working out) has on a runner’s heart rate (and thereby energy use).

A Brief definition of terms:

Elite Athlete: An athlete will who is in high school and who has participated in the state meet.

Running Form: Anything pertaining to variations in position of the “head, neck, shoulders, arms, hands, chest, abdomen, hips, spine, legs, [and] feet” (Chi Running).

Energy Use: The amount of energy needed to run at a constant speed for thirty seconds, and measurable by the intensity of one’s heart rate.

Review of Literature: Running, as defined by Amy Southall in her study of Clarence Moore’s running form, is “going faster than a walk, a steady springing step so that both feet leave the ground at the same time for an instant.” According to Jack Daniels, PhD., experienced high school, NCAA cross country coach, and author of Daniel’s Running Formula, “as you increase the amount of stress in your training, you get less benefit from that training. This is why beginning runners make vast improvements in their fitness as compared to elite runners” (Daniels, 26). This is also why elite runners must become more concentrated on form than novice runners. Chi Running, an internet site written by experienced marathoner Danny Dreyer, tells us that our “head, neck, shoulders, arms, hands, chest, abdomen, hips, spine, legs, [and] feet” (and much more) all affect our running form. In addition to form, Time Outdoors’ Neil Black also says that “In order to get the best out of your running from both a performance and an enjoyment basis, it is vital to adopt a routine which provides for effective warm up, stretching, and cool down.” Although this study does not include the importance of cooling down, I do not deny that it also is a vital aspect to running efficiently (and injury-free). Finally, according to Clive Maxwell Prestt (an experienced runner of over 40 years and running specialist)

“a warm up should consist of:

a) Walking for 60-90 seconds, building up the pace every 10 seconds or so before breaking into a gentle jog for half a mile (or whenever your body is beginning to warm up) before stopping and going into your stretching routine.

b) The gentle jog is used to circulate blood and oxygen supplying the muscles with more energy to work with.

c) Stretching to increase the range of motion at joints. Emphasis should be placed on stretching the hip flexor muscles, quadriceps, hamstrings, lower back, adductor muscles as well as those on the outside of the hips.”

He adds that a “good” warm-up will last in the neighborhood of 10-15 minutes, but that the effects of the warm-up are lost after about half an hour of inactivity, so one should begin working out soon after warming up.

Hypothesis: I believe that if an athlete runs a warm-up before running a workout and runs without over- or under- exaggerating stride length and knee rise, ones heart rate after jogging for 30 seconds will be lower than if one were to not do the above.

Method | Go Up

The model of this experiment will follow closely a model already used for a previous study which I conducted in order to determine how variations in running form affect the amount of energy used by the athlete. However, this data was only gathered for knee rise and stride length. I will devise a new method for finding the usefulness of running a warm-up prior to racing or working out.

Method for collecting data on stride length and knee rise:

Setup and preparation: First, I must find two subjects who are both willing to participate in the experiment and who have met the requirements of an “elite” runner outlined in the introduction. In order to avoid any inaccuracies that may be caused by variations in gender, I will have one male and one female subject. Having accomplished that, I will then go to Club Sport (a local gym) to use one of their treadmills. Also, the two subjects must both be wearing running shorts, running shoes, and a T-shirt in order to reduce the amount of error caused by other variables. The running surface of the treadmill must be horizontal – that is, perpendicular to gravity – for both subjects. In addition, the subjects must not be touched in any way outside the contact of their foot to the surface of the treadmill. The treadmill must have a digital read-out of how fast the subject is going, as well as how much time has elapsed. Finally, in order to be prepared for data collection, I will create a spreadsheet on which I can quickly record during the experiment.

Conduction of the Experiment: After the setup has been completed, I can begin to conduct my experiment. I will begin by having my first subject (the female) step onto the treadmill. Next, I am going to instruct her to take her resting pulse, which I will record. I will tell the subject to increase her speed to a comfortable 7 miles per hour (3.12928 meters per second). I will instruct her to run how she feels is most natural; how she would “normally” run. Once the desired velocity is achieved, the subject will jog steadily for 30 seconds. At seven miles per hour for thirty seconds, the subject will have run approximately 308 feet or approximately 93.9 meters. After the 30 seconds of running has been completed, I will tell her to stop running. I will instruct her to take her pulse for 30 seconds and multiply it by two (to simulate taking her pulse for 60 seconds), then record it on my data sheet. Afterwards I will allow her pulse to return to normal before running again, in order to avoid error. This process will be repeated two more times so that I will have multiple trials in order to increase validity. After she has finished running the “normal” set, the same procedures will then be followed for the male subject. The second set will be “high knees,” and will again begin with the female subject and be followed by the male subject (as will all of the sets). In this one, the same procedures will be followed except that I will ask the subject to raise her knees as close to parallel with the treadmill’s surface as possible while still keeping with the 7 mile per hour pace.

The third set will be the opposite of the second in terms of form, but follow all of the other procedures the same. It will be titled “low knees” and will require the participants to run at the same pace while lifting their knees as little as possible. The next set will again follow all of the same procedures as the first three with the exception of form. I will tell the subjects to lengthen their stride as much as they can (that is, to get the most distance possible with each stride). The fifth set will be the opposite of the fourth in terms of stride length (and, like all the trials, keeping every other aspect the same). The participants will be instructed to run with as short of stride as possible (covering the least amount of distance possible while keeping pace with the treadmill).

The sixth and seventh sets will differ from the others in that it will not be measuring a variation in form and will include only the male subject (because the female subject was not available for this test). However, it will still measure the affect on efficiency (heart rate). For set #5, the subject will complete a warm-up according to the model outlined by Mr. Prestt in the introduction. Afterwards, I will instruct him to wait until his pulse returns to normal. Then he will get on the treadmill and run for 30 seconds at 7 miles per hour (running with “normal” form). When he is done, I will record his pulse. This entire process will be repeated three times (allowing time for the body to cool down), including the warm-up. The seventh and final set will be run without having completed a warm-up beforehand. The exact same procedure will be followed here as with the very first set (the “normal” set).
*Note: only set #6 included a warm-up beforehand.

Lab Setup: | Go Up

Go to Lab Setup Diagram

Results: | Go Up

The results of the data gathered showed that there was a general increase in heart rate when the athlete either over- or under- exaggerated their stride length and knee rise. Although it does seem to show that under- exaggeration has a less profound effect on heart rate than over-exaggeration. Also, the data shows that having done a warm-up before engaging in activity actually produces a much lower heart rate than not doing one at all.

Heart Rate Chart (female):

Type Trial #1 Trial #2 Trial #3
Normal (set 1) 118 120 122
High Knees (set 2) 152 146 148
Low Knees (set 3) 140 140 126
Long Strides (set 4) 140 148 144
Short Strids (set 5) 136 140 134
Warm-up (set 6) N/A N/A N/A
No Warm-up (set 7) N/A N/A N/A

Other notes for the female subject: weight: 132 pounds (59.9 kilograms), resting heart rate: 84 beats per minute

Heart Rate Chart (Male):

Type Trial #1 Trial #2 Trial #3
Normal (set 1) 110 116 112
High Knees (set 2) 136 142 158
Low Knees (set 3) 122 132 128
Long Strides (set 4) 146 150 152
Short Strides (set 5) 140 140 132
Warm-up (set 6) 98 102 100
No Warm-up (set 7) 114 112 116

Other notes for the male subject follows: weight: 124 pounds (56.2 kilograms), resting heart rate: 57 beats per minute

The following is a graph which charts the averages of the heart rates in all 3 trails of all of the sets. Its purpose is to show how the subject’s heart rate was affected by the various set types.

Go To Graph Of Averages

Discussion | Go Up

Interpreting the data: As the data shows, my hypothesis was correct. It was supported in all three areas (that is, with all three variables: knee rise, stride length, and warming-up). As shown by the graph and the chart, the subject’s heart rate was considerably higher in both high and low knees and long and short strides. Also, as I predicted, running a warm-up before running the trial actually decreased heart rate. In fact, aside from resting heart rate, the warm-up set produced the lowest heart rate of all.

Explanation of results: There are several explanations for the results that I obtained from my experiment. First, there is a very simple explanation to account for the change in heart rate within the sets that varied the subject’s form. In the sets where the stride was over-exaggerated (long strides and high knees), the subject used more energy because he or she bounced more (as cited in my Extended Essay using video analysis). Using the formula mass (M) times Gravity (G) times height (H) (where M is mass of the subject, G is the gravitational constant 9.8N, and H is the height that the subject’s hip rises), we can see that if H increases, so does the product. Therefore, as the subject bounces more, the amount of gravitational potential energy used per stride increases. As for the under-exaggerated strides (low knees and short strides), they can be explained in a similar manner (using the same formula: MGH). However, there is a key difference that needs to be noted: with the under-exaggerated stride, the bounce height is actually lower than the “normal” set and, consequently, than the “over-exaggerated” sets. So the increase in energy use does not come from the bounce height but, rather, the sheer amount of strides taken in order for the subject to be able to keep pace with the treadmill. Since the amount of strides taken outweighs the decrease in bounce height, the subject uses more energy (and therefore experiences an increase in heart rate).

Finally, I will address the warm-up and non warm-up sets. For the non-warmup set, as noted above, the exact same procedures were followed in it as were followed in the “normal” set (which accounts for the similarity in heart rates between the no warm-up and normal sets). As for the warm-up set, the logical justification for the decrease in heart rate is simply explained by the fact that the body is prepared to do work. In biological terms (as suggested by Mr. Black and Mr. Prestt), after doing a warm-up run and some light stretching, the muscles have done a number of things. Among them are: attained more flexibility than normal, become “warm” due to the increase of blood-flow to the are, and become more relaxed.

The implication of increased flexibility is that the muscles then have to exert less energy lifting the legs as compared to normal (if the leg were to be lifted to the same height without being preceded by a warm-up). The importance of having “warm” muscles prior to working out is that there is already increased blood flow to the local area (the legs, in this case) there is therefore an increased amount of oxygen in the legs for the muscles to burn on demand (to put it simply). It has also has primed the leg muscles with a small amount of adrenaline which increases efficiency and power. Finally, the significance of having muscles that are semi-relaxed is similar to the importance of having stretched-out legs. It allows the legs to be moved with more ease and less resistance (which may otherwise be caused by tense or “cold” muscles). The other indirect benefits of having relaxed muscles (although this does not affect heart rate) is that it makes the likelihood of obtaining a muscular injury much less likely (because the muscles have become more elastic and thereby less prone to being over-stretched or strained).

Possible Errors: Of course, as with any non-laboratory-oriented experiment, this study has much room for error (and improvement). For one thing, the treadmill was not one hundred percent secured to the ground. This may have caused the subject to have exerted more energy than necessary in compensating for the treadmill’s “give.” Another possible error is the fact that the participant’s heart rate was only taken for 30 seconds, then multiplied by two (to get an educated estimation of what his/her heart rate might be if taken for a solid 60 seconds). More likely than not, the actual 60-second heart rate of the participant was slower by a few beats than it was recorded to be. However, in this study, there was a significant enough difference between the sets that this small difference can be ruled (perhaps) obsolete. One more possible area of error is human. This could be in anything from accurately counting the number of heart beats the subject felt when taking his/her pulse to the mathematics involved in the calculations (such as taking the arithmetic mean [averages] of the hear rates).

Links | Go Up

Warming up and Cooling Down - this site contains valuable information regarding what to stretch, how to stretch it, and how to get the best out of your stretching routinge. It also includes resons why it is beneficial to stretch before running, why it is a good idea to be properly warmed up, and why it is a poor idea not to be.

ChiRunning: The Physics of Running - This site provides an interesting look into the art of relaxing your form while you run in order to maximize efficency. Interestingly, it takes almost a spiritual look at running.

Benefits of Warming Up and Cooling Down - Contains specific information on the benefits of warming up and stretching, as well as a cut-and-dry, simple routine that should suit a great majority of people's needs in terms of properly preparing for physical exertion.

Amy Southal's Running Project - This is a link to another experiment done on running efficiency. Amy Southal has put together an analysis of Clarence Moore's long jump, things such as knee rise, form, and energy output.

Posture Perfect - here you will find a somewhat abbreviated (yet very informative) look how to run with "perfect" posture.


click here to download the raw data from my experiment  

Text .:. Excel

Lab Setup Diagram | Back to Lab Setup  


Graph Of Averages | Back To Discussion



Site created by Lane Johnson, 5/30/06.