Erin K. Nasson and Dr. Iain Hunter, Physical Education
The economy of running is very important to both competitive and recreational runners. A runner wants to perform as economically as possible to minimize metabolic costs and in order to do this the running technique must be optimized. To minimize metabolic costs refers to ones oxygen uptake, which is the amount of oxygen that is consumed throughout an activity. When large amounts of oxygen are used, the athlete will fatigue in a shorter amount of time so by minimizing the oxygen uptake, one will be able to increase the time to fatigue. Optimizing technique is something that we all do on a regular basis. It involves critiquing a specific part of a skill to produce the greatest performance of that skill.
One part of the running technique, stride length, is easy to manipulate and has a large effect on the running performance. It has been found that runners naturally settle into a preferred stride length for any given speed and grade. Studies have shown that among experienced distance runners in level-ground running the preferred stride length matches up with the optimal stride length, which minimizes metabolic costs.1 Dr. Iain Hunter found that this optimization continues throughout a fatiguing run even when the initial and final stride lengths differ. The question as to whether this ability to optimize continues while running uphill remains unknown. The value of answering this question lies in helping athletes and coaches manipulate their stride length to train their neuromuscular pathways, which will enable them to minimize their oxygen uptake.
For this study, we used members of the BYU Women’s Track and Field Team. In order to volunteer, the athlete must have been running an average of 25 miles per week for the last two years. The study was conducted in the Exercise Physiology lab using a treadmill, oxygen uptake machine, metronome, and a video camera. Each athlete visited the lab on three occasions.
On the first visit, each subject had a preliminary run where she could practice running on the treadmill while matching her stride rate to a metronome. Also during this run, the subject would find the speed that matched 70% of her predicted VO2 max while running on an uphill and level surface. This data was used with the succeeding trials. The next two trials consisted of running at either a 0% or 6% grade at the predetermined speed for a period of 20 minutes. The first five minutes of the run were conducted without any manipulation of stride rate where the subject could match her stride to that of the metronome. The remaining 15 minutes consisted of manipulating this stride rate with the cadence of the metronome that was set at their preferred stride rate and at plus and minus 8% and 16% of that rate. The order in which the stages were run was randomly chosen for each subject and each was run for a period of three minutes. Each trial was also video taped to ensure that the subject matched her stride rate with that of the metronome. The data from the last two trials were recorded and entered into a spreadsheet that included predetermined formulas to help with our analysis.
At this point in time, all of the data has been collected and is entered into the spreadsheet; however, we have not completed our final analysis of this data. Figure 1 shows an example of data that was collected for one of the subjects on an uphill run.
We were very lucky throughout the study in that we did not encounter many problems. The occasional time when a subject would forget her scheduled trial was our main set back in that we may not be able to get her back in the lab for a week because of a track meet or other commitments she might have had. Two additional problems were that, on a few occasions, the oxygen uptake machine was not calibrated correctly which meant that we had to re-collect the data and a couple of girls sustained injuries throughout the season which also meant that we had to push back the collection of their data.
We plan on having our final analysis of the data completed by the end of the summer and will submit our research for publication in Medicine and Science in Sports and Exercise and present at the 2003 Southwest ACSM meeting.
References
- Cavanagh, P. R., & Williams, K. R. (1982). The effect of stride length variation on oxygen uptake during distance running. Med Sci Sports Exerc, 14(1), 30-35.