Fitness Truth or Fiction: Pre-Workout Stretching

Many athletes find it necessary to incorporate low-intensity activities into their pre-workout routine, in order to improve flexibility and the movements of their joints. Stretching of the muscles, to the point of slight discomfort for a stipulated amount of time, is seen as a primary mechanism for accomplishing this. A copious amount of athletes are conditioned to believe that it is essential to stretch prior to a workout to prevent muscle damage and soreness, despite the lack of factual evidence. This paper addresses the inaccurate ideology that stretching before exercise will reduce the risk of injury.

Due to the elasticity of muscles, they are able to contract, lengthen, and stretch. Stretching is based on the neurophysiological phenomenon associated with the stretch reflex. A stretch stimulates muscle spindles and results in a reflex contraction of agonist muscles and a reflex inhibition of antagonist muscles (Kenney et al., 2015, p. 92). This is known as the stretch reflex and prevents a further stretch from occurring.

In order to further investigate the validity of the common belief that stretching before exercise will prevent injury, I analyzed and compared the results of three separate experiments.

The first study, “Impact of Stretching on the Performance and Injury Risk of Long-Distance Runners,” focused specifically on static stretching, which generally has to do with only slightly lengthening the muscle of one muscle group until a tight pressure is felt (Baxter et al., 2017).

The second study, “A randomized trial of pre-exercise stretching for prevention of lower-limb injury,” was conducted with the hypothesis that no evidence exists to suggest that stretching before exercising reduces injury risk, using already trained individuals and a variety of passive, active, and no warm-up prior to exercise (Pope et al., 2000).

The final experiment, “Effects of warm-up before eccentric exercise on indirect markers of muscle damage,” tested whether active and passive warm-up conducted before eccentric exercise attenuates clinical markers of muscle damage (Evans et al., 2002). Each study focused on a unique aspect or methodology of stretching, with very diversified sample populations, each functioning to clarify whether or not stretching before exercise is beneficial.

STUDY #1

Baxter et al. distinctly looked at both the acute and chronic nature of the stretching and their effects on performance delayed onset muscle soreness and injury on endurance runners. The authors defined acute stretching as “a temporary activity that is performed in a discrete capacity immediately before exercise,” and chronic stretching as “that which is performed outside of the warm-up regime as a tool of increasing long-term flexibility” (2017). They hypothesized that as a result of hypertrophy of muscle, endurance runners would see a decreased range of motion of the joints and therefore less flexibility (Baxter et al., 2017).

Studies were conducted on a group of untrained individuals that looked at the range of motion of the transverse and frontal physiological planes, showing that the decrease of this led to the balance of the pelvic region once a foot was touching the ground (Baxter et al., 2017). This ultimately resulted in a decreased range of motion and increased requirement of energy to stabilize the muscular activity (Baxter et al., 2017). It was deduced that the participants who had the “most economical running styles” were the ones with the least flexibility (Baxter et al., 2017).

When analyzing the capacity and “running economy” of the endurance runners, the studies looked at both performance potential, being metabolic, cardiorespiratory, and biomechanical characteristics such as aerobic capacity (VO2 max) and lactate threshold, as well as efficiency (Baxter et al., 2017). The objects of performance potential embodied cardiac output, hemoglobin levels, blood flow, muscle oxygen extraction, and the percentage of VO2 max in which lactic acid levels increase greatly (the greater the percentage, the greater the performance potential) (Baxter et al., 2017).

As for efficiency, this tends to correlate with performance and differs about thirty to forty percent in athletes (Baxter et al., 2017). This efficiency relates the muscles’ ability to use available energy with the athlete’s body composition, using factors dependent upon muscle morphology, elastic elements, and joint mechanics (Baxter et al., 2017).

STUDY #2

The second study was conducted using 1538 male participants between the ages of 17-35 from the Australian army (Pope et al., 2000). This specific group was chosen for the study because the recruits go through a very rigorous and regulated exercise program and see a high rate of lower-limb injury (Pope et al., 2000).

The control group did not stretch prior to workout for the duration of the study, while the participants in the stretch group engaged in one 20 second static stretch that focused on a variety of lower-limb muscles and was anticipated to induce an increase in the joint’s range of motion, such as the gastrocnemius, soleus, hamstring, quadriceps, hip adductor, and hip flexor (Pope et al., 2000). Instructors ensured that each stretch was performed correctly and for the allotted amount of time (Pope et al., 2000).

These were executed along with four minutes of dynamic stretching in which movement was involved, like jogging (Pope et al., 2000). Any injury was reported and analyzed immediately by area and type, which could be recorded as anything from the foot, ankle joint, tibia to the femur, ilium, pubis, etc., while the type referred to whether it was bone (i.e. stress fracture), ligament sprain, muscle strain, joint pain, etc. (Pope et al., 2000).

STUDY #3

In the study of “effects of warm-up before eccentric exercise on indirect markers of muscle damage,” Evans et al. studied 43 college students ranging between 17-28 randomly assigned to five conditions: high-heat passive warm-up without eccentric exercise (CONTROL), eccentric exercise without warm-up (ECC), low-heat passive warm-up preceding eccentric exercise (PW LOECC), active warm-up preceding eccentric exercise (AWLOECC), or high-heat passive warm-up preceding eccentric exercise (PWHIECC) (2002).

The effects of this study were analyzed through observations in the change of creatine kinase activity, isometric strength, resting elbow extension, active elbow flexion, circumference at the biceps, muscle belly, and distal biceps tendon region, and muscle soreness with extension and flexion (Evans et al., 2002). The group undergoing high-heat passive warm-up without eccentric exercise did not see any marker of muscle damage and was therefore used as the control group (Evans et al., 2002).

There weren't any discernible differences between the groups that participated in a warm-up before eccentric exercise versus those who did not participate in a warm-up before exercise (Evans et al., 2002). This included no critical differences recognized in the range of motion, circumferential change, and subjective pain levels (Evans et al., 2002).

The groups that completed the active warm-up displayed a larger circumferential increase than the control group, however, this was not observed after the group that completed the passive warm-up (Evans et al., 2002).

CONCLUSION

The studies reviewed concluded that no evidence exists to suggest that stretching before exercise could improve performance, provide clinical benefits, or reduce injury in endurance runners (Baxter et al., 2017). There was found to be no correlation or causation between stretching prior to exercising and a lessened risk of lower-limb injury, and results were not able to confirm that warm-up preceding eccentric exercise would result in a smaller number of clinical signs of muscle damage than participating in eccentric exercise without any prior warm-up (Pope et al., 2000; & Evans et al., 2002).

Nonetheless, the studies examined provided sufficient evidence in support of the hypothesis that stretching before exercise to prevent injury is inaccurate.

References:

Baxter, C., McNaughton, L. R., Sparks, A., Norton, L., & Bentley, D. (2017). Impact of Stretching on the Performance and Injury Risk of Long-Distance Runners. Research in Sports Medicine An International Journal,25(1), 78-90. Retrieved April 6, 2018, from https://www.tandfonline.com/doi/full/10.1080/15438627.2016.1258640

Evans, R. K., Knight, K. L., Draper, D. O., & Parcell, A. C. (2002). Effects of warm-up before eccentric exercise on indirect markers of muscle damage. Official Journal of the American College of Sports Medicine, 34(12), 1892-1899. DOI:10.1249/01.MSS.0000038895.14935.C8

Kenney, W. L., Wilmore, J. H., Costill, D. L., & Osterberg, K. (2015). Physiology of sport and exercise (6th ed.). Champaign, IL: Human Kinetics.

Pope, R. P., Herbert, R. D., Kirwan, J. D., & Graham, B. J. (2000). A randomized trial of preexercise stretching for prevention of lower-limb injury. Medicine & Science in Sports & Exercise, 32(2), 271. Retrieved April 6, 2018, from https://journals.lww.com/acsm-msse/Fulltext/2000/02000/A_randomized_trial_of_preexercise_stretching_for.4.aspx.