Effects of a Six Week Gastrocnemius PNF Stretching Intervention on Structural Properties of Muscle and Neural Adaptations of Muscle in Young Women
Semanderes, Alex Emanuel
Muscle injuries account for nearly one-third of sport medicine clinic visits in the United States (Woods et al, 2007) and amass financial burden on both athletes and their respective sports clubs. It is unclear whether stretching prevents injury, but it is practiced due to the common notion that the ability to move through a full range of motion (ROM) with ease makes it less likely to experience muscular injury as a result of rapid/extreme movements (Akagi et al, 2013a&b; Zakas etal, 2006; Haskell et al, 2007). The physiological characteristics which are thought to adapt as a result of stretching include: cross-sectional area (CSA) of muscle and muscle strength, muscle fascicle length, material stiffness, structural stiffness, and neuromuscular activity. The purpose of this research is to assess physiological changes related to structural and material properties of muscle as well as neural adaptations of the gastrocnemius as a result of a 6 week PNF stretching program in young women. Similar studies involve solely men or a mix of men and women - none involve exclusively young women; we will study women to determine if adaptations previously observed in men occur in a different fashion. We hypothesized that after a 6 week PNF stretching intervention, ankle range of motion will increase in the participants as a result of increases in fascicle length, decreases in CSA, decreases in material stiffness, and decreased muscle activation. A total of 8 subjects between 18 and 31 years of age were recruited for this study. Each subject underwent PNF stretching which targeted the gastrocnemii in their right leg (experimental leg) while their left leg remained un-stretched (serving as internal control) for a total of 6 weeks with a minimum of 16 stretching sessions. Pre-test and post-test measurements included: material stiffness, CSA of muscle, and muscle fascicle length using ultrasound imaging; structural stiffness and isokinetic strength using a dynamometer, and neural activity using EMG electrodes. The factors of time (pre-test and post-test) vs. group (stretch and control) were tested with a mixed model repeated measures on time and between group comparisons ANOVA (P [less than] .05), in addition to regression analyses performed on various characteristics. ROM significantly increased by about 9° for the treatment leg; subjects also had a significant cumulative increase of 1mm in the fascicles of the gastrocnemius in the treatment leg. There were no changes in CSA, strength, material stiffness, structural stiffness, and muscle activation of the experimental leg. In conclusion, a stretching intervention has a clear effect on increasing ROM, but a full understanding for the physiological mechanisms increasing ROM must be further examined. Increases in gastrocnemius fascicle length slightly contribute to increases in ROM, but not enough to fully explain a significant increase in ROM. It is likely the soleus is the calf muscle responsible for increasing/limiting ROM in the ankle, however, since no analytical measures were taken on this muscle, we have no information on the magnitude each physiological mechanism plays in restricting ROM. By building off this research and comprehensively monitoring adaptations in the soleus after chronic stretching, we can continue to understand the effects of stretching and tailor better stretching interventions.
Semanderes, Alex Emanuel. (May 2018). Effects of a Six Week Gastrocnemius PNF Stretching Intervention on Structural Properties of Muscle and Neural Adaptations of Muscle in Young Women (Master's Thesis, East Carolina University). Retrieved from the Scholarship. (http://hdl.handle.net/10342/6912.)
Semanderes, Alex Emanuel. Effects of a Six Week Gastrocnemius PNF Stretching Intervention on Structural Properties of Muscle and Neural Adaptations of Muscle in Young Women. Master's Thesis. East Carolina University, May 2018. The Scholarship. http://hdl.handle.net/10342/6912. August 17, 2019.
Semanderes, Alex Emanuel, “Effects of a Six Week Gastrocnemius PNF Stretching Intervention on Structural Properties of Muscle and Neural Adaptations of Muscle in Young Women” (Master's Thesis., East Carolina University, May 2018).
Semanderes, Alex Emanuel. Effects of a Six Week Gastrocnemius PNF Stretching Intervention on Structural Properties of Muscle and Neural Adaptations of Muscle in Young Women [Master's Thesis]. Greenville, NC: East Carolina University; May 2018.
East Carolina University