This week’s EXSS Impact Post represents the work of Helen Sheperd, recent graduate (2015) from the EXSS undergraduate specialization area. This work was done as part of Helen’s senior honors thesis under the direction of Dr. Claudio Battaglini.
Why did you do this study?
Most people use static stretching as a way to loosen tight muscles and improve flexibility. This form of stretching has several positive benefits, such as increasing range of motion, reducing unnecessary muscular tension and soreness after exercise. Most recently, research has shown positive effects of self-myofascial release (SMR) using a foam roller on muscle stiffness, but it is limited to data looking at range of motion. Therefore, the purpose of this study was to examine the effects of static stretching and self-myofascial release on range of motion and muscle stiffness in the calf as an attempt to evaluate if one method would provide better results than the other on reducing muscle stiffness and range of motion.
What did you do and what did you find in this study?
This was a pre-post intervention study that examined the acute effects of two different stretching techniques (static stretching and self-myofascial release) on range of motion and stiffness of the calf muscle in college-aged subjects. It was hypothesized that there would be no significant difference in range of motion between static stretching and self-myofascial release; however, self-myofascial release would cause a greater decrease in stiffness as compared to static stretching.
Twenty-six males and females between 18-28 years of age who were free of any lower leg injury or dysfunction and recreationally active (exercise but did not compete at a competitive level) were enrolled in the study and visited the UNC Neuromuscular Research Laboratory on two separate occasions lasting ~ 20 minutes in duration. On each visit, subjects were assessed to identify trigger points based on four criteria including: A palpable band taught within the skeletal muscle, 2) A hypertensive tender spot/module within a taut band, 3) Recognition of current pain complaint by pressure on the tender nodule, and 4) Painful limit to full stretch range of motion (Travell and Simons, 1993; Gerwin et al., 1997). The two visits consisted of either a static stretching or self-myofascial release protocol and there were no more than five days between each session. Each session was randomized and counter balanced.
The passive ROM of the plantar flexors was determined for each subject on every testing day using a Humac Norm isokinetic dynamometer programmed in the passive mode. Subjects were seated with the leg extended and restraining straps over the pelvis, shoulders, and contralateral thigh and the lateral malleolus aligned with the axis of rotation of the dynamometer. The foot was secured to a foot plate through a thick rubber heel cup and straps over the toes and metatarsals (distal to the malleoli so that they did not impede any passive foot movement). The dynamometer lever arm passively dorsiflexed the foot at an angular velocity of 5°·sec-1 until the participants maximum tolerable ROM was reached then immediately returned to -20° of plantar flexion.
Passive stiffness was quantified using a fourth-order polynomial regression model that was fit to the gravity corrected passive angle-torque curves generated during the passive ROM assessment according to the procedures described by Nordez et al.(2008). Passive stiffness values (Nm·deg-1) were determined at 15° dorsiflexion, and at 80% of maximum ROM.
The static stretching was performed using an incline board. The subjects stood with the right foot on the incline board and then leaned forward with their knee straight until they reached a maximum amount of tension without pain. This position was held for 1 minute. Subjects then stepped off the incline board for 1 minute then repeated the process of a total of 3 minutes (2 sessions of 1 minute of stretching). Range of motion and stiffness were measured immediately following the 3 minutes of stretching.
A Multilevel Rigid Roller was used to conduct the self-myofascial release technique, following a study protocol conducted by Healey et al. (2014). The right calf was rolled for two, one-minute bouts with one minute of rest in between bouts. Subjects were instructed to cross the left leg over the right leg and roll the foam roller down the calf using short kneading like motions. The starting position for the foam roller was at the base of the knee and it was rolled all the way down to the ankle then quickly rolled back to initial position. Subjects were told to roll down the calf 3-4 times within each minute. Range of motion and stiffness were measured immediately following the 3 minutes of foam rolling.
Calf muscle ROM delta scores (Δ=Post-intervention ROM score in degrees – Pre-intervention ROM score in degrees) and stiffness delta scores (Δ=Post-intervention stiffness score in Nm·deg-1 – Pre-intervention stiffness score in Nm·deg-1) between static stretching and self- myofascial release obtained via an isokinetic dynamometer were analyzed using dependent samples t-tests.
Twenty-six subjects, ages 18-28 years old (Mean = 20.8, SD = 1.79; Males n=6 and Females n=20), Height (cm) (166.7, SD = 8.2), and weigh (kg) (64.9, SD = 13.08) completed the study protocol. All of the subjects were students from the University of North Carolina at Chapel Hill, were apparently healthy, and participated regularly in physical activity.
Descriptive statistics on changes (Post – pre static stretching and self-myofascial release interventions) in ROM and muscular stiffness at 15˚ and Stiffness at 80% of Maximum ROM are presented in Table 1 below:
Table 1. Descriptive Statistics of Changes (Post-pre static stretching and self-myofacial release Interventions) in ROM and Muscular Stiffness at 15˚ and Stiffness at 80% of Maximum ROM
No significant differences in changes in ROM (p = .50) and muscular stiffness measured at 15˚ and at 80% of maximum ROM (p > .05) were observed between the static stretching and self-myofascial release techniques. However, at 15˚ the results of the statistical analyses approached significance (p = .06) favoring self-myofascial release over static stretching, indicating a potential for more efficient alleviation on muscular stiffness.
How do these findings impact the public?
Static stretching is a common way to loosen tight muscles but recently self-myofascial release using a foam roller has become popular. Currently, there is significantly more literature that looks at the chronic effects of self-myofascial release, not on the potential acute effects (MacDonald et al., 2013). Another issue is that most studies to date (Kuruma et al., 2013; MacDonal et al., 2013; Spernoga et al., 2001; Grieve et al., 1997) have only examined range of motion measured with a goniometer. The issue with only measuring range of motion is that it yields no information about the material property of the muscle, which does not address the stiffness component of the muscle. An increase in range of motion could be due to an increased stretch tolerance, not a change in muscle property, which is why stiffness data is paramount. ROM is also hard to measure because of a subjective end-point at which the goniometer reading is recorded due to the subject’s stretch tolerance (Magnusson, 1998). There is also no current literature that has compared the effects of static stretching and self-myofascial release on muscle stiffness or range of motion using an isokinetic dynamometer (MacDonald et al., 2013).
In this study, an isokinetic dynamometer was used to measure both stiffness and ROM before and after the stretching interventions. Each subject completed two minutes of static stretching on an incline board and two minutes of foam rolling on separate days. Results showed no significant difference between the two stretching techniques, however, an increase in ROM and reduction in muscle stiffness were observed using static stretching and SMR with a foam roller. Therefore, it was concluded that both static stretching and foam rolling increase range of motion and decrease muscle stiffness somewhat similarly.
Recommendations for Future Research
- Similar study with athletes (football players) as subjects. Athletes are more likely to have fascial restrictions than the general population due to exercise.
- Similar study with gymnasts as subjects. Gymnastics are flexible, so they may benefit more from foam rolling than static stretching.
- Modify self-myofascial release protocol to hold the foam roller on restrictions rather than continuous rolling.
- Similar study protocol with a different muscle groups other than calves, such as hamstrings.
- Similar study with stiffness and ROM measurements taken at various time intervals after stretching intervention to see if static stretching of self-myofascial release leads to longer lasting results.