Comparison of the Effect of Dynamic Stretching and Cardio Warm Up Procedures on the Peak Torque Output at the Knee Joint Alexandra K Hickox; Heather Gulgin, Ph.D, ATC Grand Valley State University, Allendale, MI 49401 Introduction Discussion Results Table 1. Dynamic Stretches Stretching is part of the common pre-exercise routine that has long been believed to increase flexibility, reduce risk of injury, and increase muscle performance. There have been several studies on the effects of static stretching versus dynamic stretching, many of which conclude that static stretching can actually be detrimental to athletic performance. Other studies have shown that a light cardio warm-up elevates core temperature, increases heart rate and oxygen efficiency, and accelerates other processes to prepare the body for exercise. However, most experiments have not made a clear distinction between dynamic stretching and warming up (cardio). Both cardio warm-ups and dynamic stretching have been claimed to increase muscle performance, but there have not been many studies comparing the effects of these approaches independently. Purpose and Hypothesis The purpose of this study was to compare the effects of dynamic stretching and cardio warm-up on muscle performance. It was hypothesized that dynamic stretching would have a greater impact on peak torque output compared to a cardio warm-up. The pilot study found significant differences in peak extension and flexion torque between the cardio warm-up and dynamic conditions versus the control condition. The left leg had significant differences in peak flexion torque while the right leg had differences in peak extension torque. The peak extension torque data for the left leg did show a large difference between the control condition and the other two experimental conditions. However, this difference was not significant, as it was in the right leg, due to the large variation (standard deviation) of the control condition (Table 2). The reason for the differences being inconsistent between legs is unknown. It could have been a matter of which leg was tested first or some difference in the way the subject was performing the tests. It is likely that with a larger study group, there would be enough data to negate variances like this or provide more evidence to explain the results. Future research should include more subjects to determine if there is a true bilateral effect. A study performed by Pablo B. Costa , Trent J. Herda , Ashley A. Herda, and Joel T. Cramer found a decrease in peak flexion torque with dynamic stretching as compared to a control test. Thus , they cautioned against using dynamic stretching before activity. However, another study done by Danny J. Mcmillian, Josef H. Moore, Brian S. Hatler, and Dean C. found that a dynamic stretching routine actually enhanced the performance of 30 military cadets during several training activities. This study concluded that a dynamic warm-up routine (combining dynamic stretches with sprints and squats) was more effective at increasing performance than static stretching and no warm-up at all. Our results are more similar to this study, in that a warm-up is better than no warm-up at all, but the difference is that they combined dynamic stretching and cardio warm-up. The previous study couldn’t answer whether dynamic or cardio warm-up is better, (since they combined them), and that is what we sought to do was look at the effects independently. With our results showing no significant difference in peak extension and flexion torque between a cardio warm-up and dynamic stretching (Table 2 &3), one may conclude that choosing either one of those warm-ups would improve muscle function. However, we didn’t determine if there is a greater effect by combining these warm- ups, and thus, future studies should examine the effect of combined cardio- warm-up and dynamic stretching to determine if it is more beneficial to utilize both in the warm-up routine, or is simply one would suffice to achieve optimal muscle performance.   Walking quad stretch 5 per leg Butt kicks Over 10 yard distance Walking hamstring stretch High knee pull Carioca with high knee Walking lunge with twist High skip 3 per leg Rear leg swing 10 per leg Lateral shuffle-dominant leg leading Lateral shuffle-non dominant leg leading Table 2. Peak Extension Torques (Mean ± SD) Peak Extension Torque Control Cardio-Warm-up Dynamic Stretching Right 96.17 + 7.00 114.11 + 7.03* 121.34 + 2.84* Left 88.46 + 25.00 115.59 + 2.54 121.34 + 2.84 *Significantly different from control condition Peak extension torque: There were no significant differences in the peak torque between the control, jog, and dynamic conditions for the left leg (Table 2). The right leg exhibited significant differences between the jog and control condition (p = 0.031), as well as for the dynamic and control condition (p = 0.006). There was no significant difference between dynamic stretching and cardio warm-up conditions on either leg (p =1.0). Methods This pilot study was performed on one subject (21 year old athletic female). The Biodex dynamometer (Figure 1) in the Biomechanics and Motor Performance lab at the Center for Health Sciences on the Grand Valley State University campus was utilized for the experiment. Three separate isokinetic tests were performed to test quadricep and hamstring peak torque: control (no warm-up), with dynamic stretching, and with cardio warm-up. The cardio warm-up consisted of lightly jogging on a treadmill for five minutes. The dynamic stretching performed is listed in Table 1. Both the right and left legs were tested (randomly), concentrically at a set angular velocity of 60 degrees per second for 3 reps per test. An extension and flexion range of motion limit, weight of the leg, and 90 degree reference angle were reset before each test. Each test was performed during the same time of day and within five days to reduce variation between tests. Data collection began within two minutes of ending the cardio warm-up or dynamic stretching. Peak torques for each repetition were found from the Biodex raw data and entered into IBM SPSS 20.0 (Armonk, New York). In order to compare the peak torque means for significant difference, a One-way ANOVA statistical test was performed, with significance set at 0.05. A post-hoc Bonferoni test was also carried out to determine which means were significantly different. Figure 2. Walking Quad Stretch Table 3. Peak Flexion Torques (Mean ± SD) Peak Flexion Torque Control Cardio-Warm-up Dynamic Stretching Right 69.06 + 5.08 75.36 + 6.07 74.02 + 3.39 Left 53.78 + 10.16 74.13 + 1.44* 74.92 + 2.05* *Significantly different from control condition Peak flexion torque: There were no significant differences between any of the conditions for the right leg (Table 3). Significant differences were seen between jog and control (p = 0.019), as well as between dynamic and control (p = 0.015) for the left leg. Figure 3. Lateral Shuffle (non dominant leg) Literature cited Costa, P. B., Herda, T. J., Herda, A. A., & Cramer, J. T. (2014, August). Effects of dynamic stretching on strength, muscle Imbalance, and muscle activation. American college of sports medicine, 46(3), 586-593. McMillian, D. J., Moore, J. H., Hatler, B. S., & Taylor, D. C. (2006, May). Dynamic vs. static-stretching warm up: the effect on power and agility performance. Journal of strength and conditioning research,20(3), 492-499. For further information regarding this study, please contact Alexandra Hickox at hickoxa@mail.gvsu.edu. Acknowledgments We thank the Physical Therapy Department of GVSU for allowing us access the Biodex dynamometer used in this study . We also thank Professor Lauren Hickox for her assistance with data collection. Figure 1. Set up for Biodex extension and flexion test Figure 4. Rear Leg Swing (left)