Stretching is a critical component of many regimens seen in clinical and fitness settings. Whether you’re a person who prefers to stretch before/after your routine, many people will attest to the physiological benefits of stretching. Proponents of stretching believe that it improves performance during exercise and prevents injuries and soreness. Some would go so far as to say that an individual may not be stretching enough when they repeatedly experience pain or injury after their workouts with no signs of improvement. Despite these enduring beliefs, the science behind the benefits of stretching is questionable. For the purposes of this blog post, we will focus on the acute, short-term effects of stretching on performance during exercise.
Three forms of stretching used in exercise and rehabilitation settings include dynamic stretching, ballistic stretching, and static stretching. Dynamic stretching is a type of stretching which involve fluid-exaggerated movements. Ballistic stretching utilizes fast countermovements. Static stretching involves extending target muscles to a limit point, and maintaining that position for an interval between 10 and 30 seconds. In order to minimize injuries, static stretching is encouraged for non-athletes.
Numerous scientific studies have shown that have shown that static stretching results in an improved joint range of motion (ROM) and greater flexibility in the muscles targeted by this technique. Conversely, research has also shown that stretching before exercises can result in a lower force output generated in the muscles that are targeted. Compliance is the lengthening of muscle fibers in response to an applied force. According to an article cited by the the National Institute of Health (Anderson, 2005), increased compliance (which occurs a result of stretching) has been linked to a decreased ability to absorb force at rest, whereas decreased compliance results in a muscle being able to withstand higher tension. This is significant because, when sarcomeres are stretched to the point that the actin and myosin filaments do not overlap, the force absorbed is transmitted to the muscle fiber cytoskeleton; resulting in fiber damage (regardless of a muscle’s joint ROM). Thus, compliance may result in decreased performance depending on the type of exercise performed. Another issue that arises related to the use of stretching before exercise is the type of stretching utilized. Science has shown that muscle fibers can experience tension when stretched as little as 20% of their total length1. Thus, it is difficult to establish a universal standard describing correct stretching techniques. In addition, improved joint ROM can be attributable to extraneous factors (such as increased pain tolerance); making the strength of its relationship to stretching highly questionable.
There are a plethora of studies conducted that attempt to quantify the effect of stretching on performance. One study, conducted by researchers at Sahmyook University in 20182 examined the effects of stretching on muscle strength, endurance, and endurance in a non-athletic sample of 13 active collegiate male students. These subjects were separated into three groups: those who did not perform any warm ups before exercise (NWU), those who performed aerobic warm ups in the form of power walking for ten minutes (AWU) before exercise, and those who performed aerobic warm ups with static stretching for ten minutes (ASU). All three groups performed isokinetic muscle testing. The stretching used in the study consisted of straddling, seated calf stretching, and standing quadriceps stretching for the lower body. Two repetitions of each stretching motion were performed for 20 sec each and the entire stretching program took 5 min to perform. All subjects rested for 1 min after warming up and then underwent isokinetic muscle testing of the knee joints. The sequence of performance of each warm-up exercise was individually randomized. In the successive weeks, each group was tested according to the type of warm-up performed. The testing was conducted for 3 weeks, and all groups were allowed a week to rest in between tests.
In order to quantify the results in each group, a knee extension/flexion isokinetic dynamometer was used. Participants were asked to extend and flex the knee by exerting their maximum strength as fast as possible while keeping their trunk up against the backrest during the test and to hold onto the handles. The subjects performed the maximal test of four repetitions. Each maximal test was conducted with an angular speed of 60°/sec to measure isokinetic muscle strength and an angular speed of 180°/sec to measure isokinetic muscle power. In addition, the muscle endurance test was conducted with an angular speed of 240°/sec. The exercise was conducted twice prior to testing to familiarize the subjects with the test, thereby achieving optimal results. The subjects were verbally encouraged and allowed to view their torque graphs during testing as a form of visual feedback to increase motivation. To analyze muscle strength, power and endurance, measurements of the left and right knee joints were divided into each independent variable before data processing was performed. In addition, psychological evaluations in the form of questionnaires were administered to subjects before and after workouts for individuals in all three groups. These assessments utilized a 5-point Likert scale (1, very bad; 2, bad; 3, average; 4, good; 5, very good). The Kruskal–Wallis rank test were used to examine the differences of variables among groups and the Wilcoxon test was used to investigate psychological conditions before and after warm-ups within times in each group. A Mann–Whitney post hoc test was implemented to detect any significant differences in the Kruskal–Wallis test. The significance of all data was established at p ≤0.05. The results from the table have been included in figures attached to this post. The data is shown in the bottom of this point via a hyperlink.
Based on the results of this experiment, the researchers concluded that there was no significant effect of the type of warm-up activity on performance in any of the tests performed in this study. Shown in Table 2, at 60°/sec (which is an angular speed for rating muscle strength), the NWU showed higher rates for both the extensor and flexor. However, the researchers determined that the difference was not statistically significant Shown in Table 3, at 180°/sec (an angular speed associated with rating muscle power), AWU and ASW groups attained higher rates for the flexor and extensor, respectively, although the difference was not statistically significant. The total work at 240°/sec (which reflects muscle endurance) was higher in ASW for both the flexor and extensor than NWU and AWU, though not statistically significantly. These results are shown in Table 4. In a similar manner to the trends seen when evaluating athletic performance, the individuals in the ASW group marked higher scores on their psychological assessments than the AWU and NWU groups. The results are shown in Table 5. However, the researchers determined that the result were not statistically significant.
Overall, while there appears to be some merit to the psychological benefits of stretching before exercising, its effect on athletic performance remains inconclusive. However, if you find that stretching helps improve your outlook/state-of-mind during the course of your workout, I would highly encourage you to continue your routine.
Questions to Consider
- Based on the experiment, do you believe that stretching before a workout provides any benefits/advantages towards performance?
- Does this post affect your views towards stretching?
- Would you encourage someone seeking to exercise more frequently to stretch before/after their exercises?
References
- Andersen JC. Stretching before and after exercise: effect on muscle soreness and injury risk. J Athl Train. 2005;40(3):218–220.
- Park HK, Jung MK, Park E, et al. The effect of warm-ups with stretching on the isokinetic moments of collegiate men. J Exerc Rehabil. 2018;14(1):78–82. Published 2018 Feb 26. doi:10.12965/jer.1835210.605
