Acute Effects of Different Intensity and Duration of Static Stretching on the Muscle-Tendon Unit Stiffness of the Hamstrings

Acute and chronic effects of static stretching of different target muscles on shear elastic modulus: A narrative review

We investigated the acute and chronic effects of static stretching on shear elastic modulus and assessed whether these effects could differ among various target muscles. PubMed, Scopus, and Google Scholar databases were searched for articles published up to 2023, using the terms "stretch," "stretching," "static stretching," "shear elastic modulus," "shear modulus," and "shear wave elastography." Thirty-seven original studies measured the shear elastic modulus after stretching: 32 and five evaluated acute and chronic effects, respectively. Acute stretching significantly decreased the shear elastic modulus in various muscles as follows: infraspinatus and pectoralis minor (2/2 studies, 100 %); medial gastrocnemius (15/17 studies, 88.2 %); lateral gastrocnemius (4/6 studies, 66.7 %); semimembranosus and semitendinosus (4/5 studies, 80 %); biceps femoris (3/5 studies, 60 %); and rectus femoris (3/4 studies, 75 %). No significant changes were found in the soleus, vastus lateralis, vastus medialis, teres minor, and posterior deltoid muscles, highlighting the variability in the effects of stretching on shear elastic modulus across different muscles. The difference in the effect depends on the stretching methods, including the position, duration, and intensity and position at which the shear elastic modulus is measured. Therefore, we should establish stretching methods for each muscle and investigate chronic effects on the shear elastic modulus.

Effects of Conditioning Contractions on Lower-Body Explosive Force Post-Static Stretching

The present study assessed the impacts of two distinct protocols, static stretching (StS, 4 sets of 30 seconds) and static stretching combined with conditioning contractions (10 repetitive drop jumps) (SC), on neuromuscular response and rate of force development (RFD) in the lower limbs during squat jumps (SJs) at varying initial knee-joint angles (60°,90°,120°). Twelve participants completed three randomized experimental trials (no intervention, StS intervention, and SC intervention). Except for the intervention segments, each trial included standardized warm-ups and SJs at three different angles. Data were collected using a 3-dimensional injury motion capture system, an electromyography (EMG) recording system, and a force platform. The collected EMG data were subjected to amplitude calculations, while force-time data were used for RFD computation. Neither StS nor SC significantly impacted the average or peak EMG amplitudes of the five muscles examined (p>0.05). However, at an initial knee-joint angle of 120°, the StS group demonstrated significantly lower RFD values at three distinct phases (0-50 ms, 50-100 ms, and 0-peakforce) compared to those seen in the SC and control groups (p<0.05). For activities starting with a knee-joint angle of 120°, it is recommended to either avoid StS or combine it with ten repetitive drop jumps to mitigate any potential negative impact on explosiveness.

Combined Effects of Static and Dynamic Stretching on the Muscle-Tendon Unit Stiffness and Strength of the Hamstrings

ABSTRACT

Takeuchi, K, Nakamura, M, Matsuo, S, Samukawa, M, Yamaguchi, T, and Mizuno, T. Combined effects of static and dynamic stretching on the muscle-tendon unit stiffness and strength of the hamstrings. J Strength Cond Res 38(4): 681-686, 2024-Combined static and dynamic stretching for 30 seconds is frequently used as a part of a warm-up program. However, a stretching method that can both decrease muscle-tendon unit (MTU) stiffness and increase muscle strength has not been developed. The purpose of this study was to examine the combined effects of 30 seconds of static stretching at different intensities (normal-intensity static stretching [NS] and high-intensity static [HS]) and dynamic stretching at different speeds (low-speed dynamic [LD] and high-speed dynamic stretching [HD]) on the MTU stiffness and muscle strength of the hamstrings. Thirteen healthy subjects (9 men and 4 women, 20.9 ± 0.8 years, 169.3 ± 7.2 cm, 61.1 ± 8.2 kg) performed 4 types of interventions (HS-HD, HS-LD, NS-HD, and NS-LD). Range of motion (ROM), passive torque, MTU stiffness, and muscle strength were measured before and immediately after interventions by using an isokinetic dynamometer machine. In all interventions, the ROM and passive torque significantly increased (p < 0.01). Muscle-tendon unit stiffness significantly decreased in HS-HD and HS-LD (both p < 0.01), but there was no significant change in NS-HD (p = 0.30) or NS-LD (p = 0.42). Muscle strength significantly increased after HS-HD (p = 0.02) and NS-LD (p = 0.03), but there was no significant change in HS-LD (p = 0.23) or NS-LD (p = 0.26). The results indicated that using a combination of 30 seconds of high-intensity static stretching and high-speed dynamic stretching can be beneficial for the MTU stiffness and muscle strength of the hamstrings.

Functional connections between the temporomandibular joint and the hip joint

Introduction. Some of the factors in the formation of temporomandibular joint disorders are changes in the central and peripheral nervous systems. In the context of creating connections between two joints, fascia and the concept of biotensegration are important. The tension created in the tissue is linearly distributed along the entire body. The creation of excessive tension within one structure can lead to the creation of identical tension in a distant structure. Aim of the study. The research hypothesis was that soft tissue manual treatments of the temporomandibular joint, with a duration of 7 minutes per side would affect increased mobility in the hip joint for the motion of the abduction. Results. The obtained value for the right and left hip joint shows a strong and positive correlation. This proves that the therapy performed had an effect on increasing the range of motion. Conclusions. Myofascial release of the tissues of the temporomandibular joint had a positive effect on the increase in the range of motion for hip abduction.

The effect of stretching exercises on the mobility of the spine in the sagittal plane in people using digital devices – preliminary observations

Introduction. Digital devices and a sedentary lifestyle pose significant health risks in today’s society, further exacerbated by the regular adoption of incorrect posture. Prolonged adoption of an incorrect posture can result in pain and impaired spinal mobility. Aim of the study. The study aims to evaluate the impact of stretching exercises on improving cervical, thoracic and lumbar spine mobility in the sagittal plane. Furthermore, it sought to examine the potential correlation between the occurrence of pain and the duration of digital equipment usage. Study materials and methodology. The study was conducted on a sample group of 22 individuals aged 18 to 21 (20.11 ± 1.56) years. Linear measurements, including the Schober and Otto-Wurm tests, were used to examine spinal mobility in the sagittal plane. The subjects were given a 10-day programme comprising six stretching exercises to perform autonomously daily. After ten days, line measurements were retaken. Results. Significant statistical values were observed for spinal ranges of motion in the sagittal plane; no statistically significant value was obtained for the incidence of pain and the duration of use of digital devices. Conclusions. The subjects demonstrated improvement in cervical, thoracic, and lumbar spine mobility in the sagittal plane following the implementation of stretching exercises. Additionally, a decrease in spinal pain was observed.

Acute and Long-Term Effects of Static Stretching on Muscle-Tendon Unit Stiffness: A Systematic Review and Meta-Analysis

Static stretching can increase the range of motion of a joint. Muscle-tendon unit stiffness (MTS) is potentially one of the main factors that influences the change in the range of motion after static stretching. However, to date, the effects of acute and long-term static stretching on MTS are not well understood. The purpose of this meta-analysis was to investigate the effects of acute and long-term static stretching training on MTS, in young healthy participants. PubMed, Web of Science, and EBSCO published before January 6, 2023, were searched and finally, 17 papers were included in the meta-analysis. Main meta-analysis was performed with a random-effect model and subgroup analyses, which included comparisons of sex (male vs. mixed sex and female) and muscle (hamstrings vs. plantar flexors) were also performed. Furthermore, a meta-regression was conducted to examine the effect of total stretching duration on MTS. For acute static stretching, the result of the meta-analysis showed a moderate decrease in MTS (effect size = -0.772, Z = -2.374, 95% confidence interval = -1.409 - -0.325, p = 0.018, I2 = 79.098). For long-term static stretching, there is no significant change in MTS (effect size = -0.608, Z = -1.761, 95% CI = -1.284 - 0.069, p = 0.078, I2 = 83.061). Subgroup analyses revealed no significant differences between sex (long-term, p = 0.209) or muscle (acute, p =0.295; long-term, p = 0.427). Moreover, there was a significant relationship between total stretching duration and MTS in acute static stretching (p = 0.011, R2 = 0.28), but not in long-term stretching (p = 0.085, R2 < 0.01). Whilst MTS decreased after acute static stretching, only a tendency of a decrease was seen after long-term stretching.

Long-term static stretching can decrease muscle stiffness: A systematic review and meta-analysis

Stretch training increases the range of motion of a joint. However, to date, the mechanisms behind such a stretching effect are not well understood. An earlier meta-analysis on several studies reported no changes in the passive properties of a muscle (i.e., muscle stiffness) following long-term stretch training with various types of stretching (static, dynamic, and proprioceptive neuromuscular stretching). However, in recent years, an increasing number of papers have reported the effects of long-term static stretching on muscle stiffness. The purpose of the present study was to examine the long-term (≥2 weeks) effect of static stretching training on muscle stiffness. PubMed, Web of Science, and EBSCO published before December 28, 2022, were searched and 10 papers met the inclusion criteria for meta-analysis. By applying a mixed-effect model, subgroup analyses, which included comparisons of sex (male vs. mixed sex) and type of muscle stiffness assessment (calculated from the muscle-tendon junction vs. shear modulus), were performed. Furthermore, a meta-regression was conducted to examine the effect of total stretching duration on muscle stiffness. The result of the meta-analysis showed a moderate decrease in muscle stiffness after 3-12 weeks of static stretch training compared to a control condition (effect size = -0.749, p < 0.001, I2  = 56.245). Subgroup analyses revealed no significant differences between sex (p = 0.131) and type of muscle stiffness assessment (p = 0.813). Moreover, there was no significant relationship between total stretching duration and muscle stiffness (p = 0.881).