Daily muscle stretching enhances blood flow, endothelial function, capillarity, vascular volume and connectivity in aged skeletal muscle

The biological macromolecules constructed Matrigel for cultured organoids in biomedical and tissue engineering

Matrigel is the most commonly used matrix for 3D organoid cultures. Research on the biomaterial basis of Matrigel for organoid cultures is a highly challenging field. Currently, many studies focus on Matrigel-based biological macromolecules or combinations to construct natural Matrigel and synthetic hydrogel scaffolds based on collagen, peptides, polysaccharides, microbial transglutaminase, DNA supramolecules, and polymers for organoid culture. In this review, we discuss the limitations of both natural and synthetic Matrigel, and describe alternative scaffolds that have been employed for organoid cultures. The patient-derived organoids were constructed in different cancer types and limitations of animal-derived organoids based on the hydrogel or Matrigel. The constructed techniques utilizing 3D bioprinting platforms, air-liquid interface (ALI) culture, microfluidic culture, and organ-on-a-chip platform are summarized. Given the potential of organoids for a wide range of therapeutic, tissue engineering and pharmaceutical applications, it is indeed imperative to develop defined and customized hydrogels in addition to Matrigel.

Potential preservative mechanisms of cardiac rehabilitation pathways on endothelial function in coronary heart disease

Cardiac rehabilitation, a comprehensive exercise-based lifestyle and medical management, is effective in decreasing morbidity and improving life quality in patients with coronary heart disease. Endothelial function, an irreplaceable indicator in coronary heart disease progression, is measured by various methods in traditional cardiac rehabilitation pathways, including medicinal treatment, aerobic training, and smoking cessation. Nevertheless, studies on the effect of some emerging cardiac rehabilitation programs on endothelial function are limited. This article briefly reviewed the endothelium-beneficial effects of different cardiac rehabilitation pathways, including exercise training, lifestyle modification and psychological intervention in patients with coronary heart disease, and related experimental models, and summarized both uncovered and potential cellular and molecular mechanisms of the beneficial roles of various cardiac rehabilitation pathways on endothelial function. In exercise training and some lifestyle interventions, the enhanced bioavailability of nitric oxide, increased circulating endothelial progenitor cells (EPCs), and decreased oxidative stress are major contributors to preventing endothelial dysfunction in coronary heart disease. Moreover, the preservation of endothelial-dependent hyperpolarizing factors and inflammatory suppression play roles. On the one hand, to develop more endothelium-protective rehabilitation methods in coronary heart disease, adequately designed and sized randomized multicenter clinical trials should be advanced using standardized cardiac rehabilitation programs and existing assessment methods. On the other hand, additional studies using suitable experimental models are warranted to elucidate the relationship between some new interventions and endothelial protection in both macro- and microvasculature.

Effects of aging and exercise training on bone and marrow blood flow and vascular function

Aging leads to progressive bone loss, which is associated with impaired bone and marrow perfusion. The purpose of this study was to determine whether chronic exercise training enhances blood flow to the femur at rest and during exercise, and elucidate whether putative changes in training-induced bone perfusion are associated with alterations in the intrinsic vasomotor properties of the femoral principal nutrient artery (PNA) in old age. Young (4-6 mo old) and old (20-22 mo old) male Fischer-344 rats were either treadmill exercise trained (ET) or remained sedentary (SED). Regional blood flow to the femur was assessed at rest and during treadmill exercise. Endothelium-dependent (acetylcholine, ACh) and -independent (Dea-NONOate) vasodilator, and vasoconstrictor (phenylephrine (PE), KCl and myogenic) responses of femoral PNAs were determined. Exercise training led to higher blood flow to distal metaphysis and epiphysis in old rats at rest, and old ET rats showed greater regional blood flow during exercise compared to old SED rats. The increased blood flow to the proximal and distal metaphysis and epiphysis were also higher in old ET rats than that in young ET rats. Exercise training enhanced the vasodilator response to ACh, corresponding to increased eNOS expression in femoral PNAs from both young and old rats. Aging did not alter PE- or KCl-induced vasoconstriction, whereas myogenic responses were impaired. Exercise training enhanced vasoconstrictor responses to PE in old rats but had no effect on KCl or myogenic responses in either group. These data demonstrate that exercise training enhances both regional bone and marrow blood flow and vasodilator responses, which are impaired in the femora of old SED rats.

Efficacy and Safety of Static Stretching and Daily Walking on the Cardio-Ankle Vascular Index in a Patient With Type 2 Diabetes Mellitus, Proliferative Retinopathy, and Lower-Extremity Peripheral Arterial Disease: A Case Report

Proliferative diabetic retinopathy (PDR) and peripheral arterial disease (PAD) of the lower extremities are serious complications of type 2 diabetes mellitus (T2DM). Aerobic exercise has been shown to be primarily effective for glycemic control and gait disturbance owing to PAD. However, the safety and efficacy of exercise therapy in patients with PDR remain unclear. The purpose of this case report was to demonstrate the short-term effects of static stretching (SS) and daily walking over 10,000 steps on patients with T2DM presenting with PDR and PAD. The intervention consisted of 40 minutes of other-movement SS and in-hospital walking during a two-week hospitalization phase and 20-30 minutes of automatic SS and outdoor walking during a two-week home phase post-discharge. The walking conditions consisted of 10,000 steps/day, and the rate of perceived exertion was 11-12 on the Borg scale. Outcomes included the presence of a new intraocular hemorrhage and changes in intraocular pressure (IOP), blood pressure, fasting blood glucose level, biochemical parameters, cardio-ankle vascular index (CAVI), and ankle-brachial index. No new intraocular hemorrhage or increased IOP was observed during the intervention period, and blood pressure, glycemic control, and CAVI parameters improved. The results of the intervention in this case suggest that the combination of SS and walking exercises may be safe and effective.

Revisiting the stretch-induced force deficit: A systematic review with multilevel meta-analysis of acute effects

BACKGROUND

When recommending avoidance of static stretching prior to athletic performance, authors and practitioners commonly refer to available systematic reviews. However, effect sizes (ES) in previous reviews were extracted in major part from studies lacking control conditions and/or pre-post testing designs. Also, currently available reviews conducted calculations without accounting for multiple study outcomes, with ES: -0.03 to 0.10, which would commonly be classified as trivial.

METHODS

Since new meta-analytical software and controlled research articles have appeared since 2013, we revisited the available literatures and performed a multilevel meta-analysis using robust variance estimation of controlled pre-post trials to provide updated evidence. Furthermore, previous research described reduced electromyography activity-also attributable to fatiguing training routines-as being responsible for decreased subsequent performance. The second part of this study opposed stretching and alternative interventions sufficient to induce general fatigue to examine whether static stretching induces higher performance losses compared to other exercise routines.

RESULTS

Including 83 studies with more than 400 ES from 2012 participants, our results indicate a significant, small ES for a static stretch-induced maximal strength loss (ES = -0.21, p = 0.003), with high magnitude ES (ES = -0.84, p = 0.004) for stretching durations ≥60 s per bout when compared to passive controls. When opposed to active controls, the maximal strength loss ranges between ES: -0.17 to -0.28, p < 0.001 and 0.040 with mostly no to small heterogeneity. However, stretching did not negatively influence athletic performance in general (when compared to both passive and active controls); in fact, a positive effect on subsequent jumping performance (ES = 0.15, p = 0.006) was found in adults.

CONCLUSION

Regarding strength testing of isolated muscles (e.g., leg extensions or calf raises), our results confirm previous findings. Nevertheless, since no (or even positive) effects could be found for athletic performance, our results do not support previous recommendations to exclude static stretching from warm-up routines prior to, for example, jumping or sprinting.

The effects of static and dynamic stretching on deep fascia stiffness: a randomized, controlled cross-over study

AIM

Previous stretching studies mostly investigated effects on the skeletal muscle but comprehensive explorations regarding the role of the connective tissue are scarce. Since the deep fascia has been demonstrated to be sensitive to mechanical tension, it was hypothesized that the fascia would also respond to stretching, contributing to enhanced range of motion (ROM).

METHODS

Forty (40) recreationally active participants (male: n = 25, female: n = 15) were included in the randomized controlled cross-over trial and allocated to different groups performing 5 min static (STAT) or dynamic (DYN) plantar flexor stretching or control condition (CC) in a random order. Pre- and immediately post-intervention, muscle and fascia stiffness, as well as muscle and fascia thickness were measured using high-resolution ultrasound and strain elastography. ROM was assessed in the ankle joint via the knee to wall test (KtW) and goniometer.

RESULTS

STAT reduced both, muscle and fascia stiffness (d = 0.78 and 0.42, p < 0.001, respectively), while DYN did not reduce stiffness compared to the control condition (p = 0.11-0.41). While both conditions showed significant increases in the KtW (d = 0.43-0.46, p = 0.02-0.04), no significant differences to the CC were observed for the isolated ROM testing (p = 0.09 and 0.77). There was a small correlation between fascia stiffness decreases and ROM increases (r = - 0.25, p = 0.006) but no association was found between muscle stiffness decreases and ROM increases (p = 0.13-0.40).

CONCLUSION

Our study is the first to reveal stretch-induced changes in fascia stiffness. Changes of fascia`s but not muscle`s mechanical properties may contribute to increased ROM following stretching.

The role of hypertension in the relationship between leisure screen time, physical activity and migraine: a 2-sample Mendelian randomization study

BACKGROUND

The relationship between lifestyle and migraine is complex, as it remains uncertain which specific lifestyle factors play the most prominent role in the development of migraine, or which modifiable metabolic traits serve as mediators in establishing causality.

METHODS

Independent genetic variants strongly associated with 20 lifestyle factors were selected as instrumental variables from corresponding genome-wide association studies (GWASs). Summary-level data for migraine were obtained from the FinnGen consortium (18,477 cases and 287,837 controls) as a discovery set and the GWAS meta-analysis data (26,052 cases and 487,214 controls) as a replication set. Estimates derived from the two datasets were combined using fixed-effects meta-analysis. Two-step univariable MR (UVMR) and multivariable Mendelian randomization (MVMR) analyses were conducted to evaluate 19 potential mediators of association and determine the proportions of these mediators.

RESULTS

The combined effect of inverse variance weighted revealed that a one standard deviation (SD) increase in genetically predicted Leisure screen time (LST) was associated with a 27.7% increase (95% CI: 1.14-1.44) in migraine risk, while Moderate or/and vigorous physical activity (MVPA) was associated with a 26.9% decrease (95% CI: 0.61-0.87) in migraine risk. The results of the mediation analysis indicated that out of the 19 modifiable metabolic risk factors examined, hypertension explains 24.81% of the relationship between LST and the risk of experiencing migraine. Furthermore, hypertension and diastolic blood pressure (DBP) partially weaken the association between MVPA and migraines, mediating 4.86% and 4.66% respectively.

CONCLUSION

Our research findings indicated that both LST and MVPA in lifestyle have independent causal effects on migraine. Additionally, we have identified that hypertension and DBP play a mediating role in the causal pathway between these two factors and migraine.

Discussing Conflicting Explanatory Approaches in Flexibility Training Under Consideration of Physiology: A Narrative Review

The mechanisms underlying range of motion enhancements via flexibility training discussed in the literature show high heterogeneity in research methodology and study findings. In addition, scientific conclusions are mostly based on functional observations while studies considering the underlying physiology are less common. However, understanding the underlying mechanisms that contribute to an improved range of motion through stretching is crucial for conducting comparable studies with sound designs, optimising training routines and accurately interpreting resulting outcomes. While there seems to be no evidence to attribute acute range of motion increases as well as changes in muscle and tendon stiffness and pain perception specifically to stretching or foam rolling, the role of general warm-up effects is discussed in this paper. Additionally, the role of mechanical tension applied to greater muscle lengths for range of motion improvement will be discussed. Thus, it is suggested that physical training stressors can be seen as external stimuli that control gene expression via the targeted stimulation of transcription factors, leading to structural adaptations due to enhanced protein synthesis. Hence, the possible role of serial sarcomerogenesis in altering pain perception, reducing muscle stiffness and passive torque, or changes in the optimal joint angle for force development is considered as well as alternative interventions with a potential impact on anabolic pathways. As there are limited possibilities to directly measure serial sarcomere number, longitudinal muscle hypertrophy remains without direct evidence. The available literature does not demonstrate the necessity of only using specific flexibility training routines such as stretching to enhance acute or chronic range of motion.

4-week stretching program after submaximal strength exercise affects performance but not heart rate variability and lactate clearance. An exploratory study

Previous research has demonstrated that stretching can enhance athletic performance and induce cardiovascular adaptations. This study aims to assess whether a 4-week preventative stretching routine can enhance heart rate variability and heart rate recovery, faster blood lactate clearance, and improve performance following submaximal strength exercises. Twenty-four healthy adults were recruited and randomly allocated to either the experimental group or the control group. Both groups engaged in submaximal strength exercises (5 sets to voluntary failure at 60% of 1RM) comprising bench press and back squat exercises under baseline conditions and after stretching protocol. The experimental group followed the Stretching Protocol, while the control group adhered to their regular training routine. ANOVA analysis revealed a significant pre-post interaction effect between groups in the variable of squat repetitions, although no notable pre- or post-differences were observed in heart rate variability, heart rate recovery, blood lactate concentration, or bench repetitions in either group. A 4-week preventative stretching program does not appear adequate to enhance lactate clearance and cardiovascular adaptation after submaximal strength exercises in resistance-trained individuals compared to the control group. However, it is plausible that such a stretching routine may mitigate muscle fatigue, though further investigation is warranted to substantiate this hypothesis.

Longitudinal trends in physical activity levels and lifetime cardiovascular disease risk: insights from the ATTICA cohort study (2002-2022)

Objective

To evaluate trends in physical activity levels and their associations with demographic characteristics, health status, and lifetime cardiovascular disease (CVD) risk.

Methods

A longitudinal analysis was conducted using data from 987 males and 1,001 females (45 ± 12 years old) participating in the ATTICA cohort study. Physical activity levels were assessed at baseline (2001-2002) and subsequent follow-ups (2006, 2012, and 2022). Four physical activity trajectories according to participants' physical activity tracking were defined, i.e., consistently active/inactive and changed from active/inactive. Twenty-year incidence of hypertension, hypercholesterolemia, and diabetes were evaluated in relation to physical activity trajectories; the life-table method was utilized to forecast the lifetime CVD risk (death without CVD was regarded as a competing event).

Results

in total, 47% of the participants were categorized as being consistently inactive, whereas only 9% of males and 15% of females sustained physical activity levels throughout the 20-year follow-up period (p < 0.001). Participants being consistently inactive were from lower socioeconomic backgrounds (p = 0.002). Transitioning to being physically active was associated with higher education level and being married (p < 0.001). Consistently active individuals had up to 35% reduced lifetime CVD risk, and lower 20-year incidence of hypertension, and hypercholesterolemia (p < 0.01); no association was observed regarding diabetes incidence.

Conclusions

Promoting and maintaining regular physical activity throughout lifespan is crucial for reducing lifetime CVD risk and related risk factors. Tailored interventions addressing demographic and socioeconomic factors may help enhance cardiovascular health outcomes.

Resistance Training Causes the Stretch-Induced Force Deficit-A Randomized Cross-Over Study

PURPOSE

Stretch-induced force deficit suggests an acute stretch-specific strength capacity loss, which is commonly attributed to EMG reductions. Since those deficits could also be attributed to general fatigue induced by overloading the muscle, this study aimed to compare stretching with an exhausting calf raise programme to compare strength and stretching responses.

METHOD

This study included 16 participants with different, high-duration calf muscle stretching effects (10, 20, 30 min of stretching) with resistance training (RT) (3 × 12 repetitions) performed until muscle failure, by using a cross-over study design with pre-post comparisons. Strength was tested via isometric plantar flexor diagnostics, while flexibility was assessed using the knee-to-wall test (KtW) and an isolated goniometer test.

RESULTS

Using a three-way ANOVA, RT strength decreases were greater compared to 10 and 20 min of stretching (p = 0.01-0.02), but similar to those of 30 min of stretching. ROM in the KtW showed no specific stretch-induced increases, while only the stretching conditions enhanced isolated tested ROM (p < 0.001-0.008). No RT-related isolated ROM increases were observed.

CONCLUSIONS

The results showed both interventions had similar effects on strength and ROM in the calf muscles. More holistic explanatory approaches such as fatigue and warm-up are discussed in the manuscript and call for further research.

Effects of Chronic Static Stretching on Maximal Strength and Muscle Hypertrophy: A Systematic Review and Meta-Analysis with Meta-Regression

BACKGROUND

Increases in maximal strength and muscle volume represent central aims of training interventions. Recent research suggested that the chronic application of stretch may be effective in inducing hypertrophy. The present systematic review therefore aimed to syntheisize the evidence on changes of strength and muscle volume following chronic static stretching.

METHODS

Three data bases were sceened to conduct a systematic review with meta-analysis. Studies using randomized, controlled trials with longitudinal (≥ 2 weeks) design, investigating strength and muscle volume following static stretching in humans, were included. Study quality was rated by two examiners using the PEDro scale.

RESULTS

A total of 42 studies with 1318 cumulative participants were identified. Meta-analyses using robust variance estimation showed small stretch-mediated maximal strength increases (d = 0.30 p < 0.001) with stretching duration and intervention time as significant moderators. Including all studies, stretching induced small magnitude, but significant hypertrophy effects (d = 0.20). Longer stretching durations and intervention periods as well as higher training frequencies revealed small (d = 0.26-0.28), but significant effects (p < 0.001-0.005), while lower dosage did not reach the level of significance (p = 0.13-0.39).

CONCLUSIONS

While of minor effectiveness, chronic static stretching represents a possible alternative to resistance training when aiming to improve strength and increase muscle size. As a dose-response relationship may exist, higher stretch durations and frequencies as well as long program durations should be further elaborated.

Comparison of Supervised versus Self-Administered Stretching on Bench Press Maximal Strength and Force Development

PURPOSE

While there is reported superior effectiveness with supervised training, it usually requires specialized exercise facilities and instructors. It is reported in the literature that high-volume stretching improves pectoralis muscles strength under supervised conditions while practical relevance is discussed. Therefore, the study objective was to compare the effects of volume equated, supervised- and self-administered home-based stretching on strength performance.

METHODS

Sixty-three recreational participants were equally assigned to either a supervised static stretching, home-based stretching, or control group. The effects of 15 min pectoralis stretching, 4 days per week for 8 weeks, were assessed on dynamic and isometric bench press strength and force development.

RESULTS

While there was a large magnitude maximal strength increase (p < 0.001-0.023, ƞ2 = 0.118-0.351), force development remained unaffected. Dynamic maximal strength in both groups demonstrated large magnitude increases compared to the control group (p < 0.001-0.001, d = 1.227-0.905). No differences between the intervention group for maximal strength (p = 0.518-0.821, d = 0.101-0.322) could be detected.

CONCLUSIONS

The results could potentially be attributed to stretch-induced tension (mechanical overload) with subsequent anabolic adaptations, and alternative explanatory approaches are discussed. Nevertheless, home-based stretching seems a practical alternative to supervised training with potential meaningful applications in different settings.

Self-stretching exercises with kinesio taping for management of chronic nonspecific neck pain in taxi drivers: A single-blind, randomized controlled trial

OBJECTIVES

Taxi drivers experience chronic neck pain owing to their posture while driving. The aim of this study was to investigate the effect of self-stretching exercises with kinesio taping on pain, stress, pressure pain threshold (PPT), disability, cervical range of motion (CROM) in this population.

DESIGN

A single-blind, randomized controlled trial SETTING: Forty-three taxi drivers with nonspecific chronic nonspecific neck pain were randomly assigned to experimental (n = 22) and control (n = 21) groups.

METHODS

In the experimental group, self-stretching exercises were performed 3 times a day, 5 days per week, for 4 weeks, with kinesio taping applied while driving. In the control group, only kinesio taping was applied while driving for 4 weeks. Pain intensity, stress intensity, PPT, neck disability, and CROM were assessed pre-intervention, post-intervention, and at 4 weeks post-intervention.

RESULTS

Significant time and group interactions were observed in pain intensity at rest (p = 0.048) and while driving (p = 0.001). In the experimental group, the Pre - Post - Follow-up mean (95% CI) was 4.41 (4.14 to 4.68) - 3.82 (3.57 to 4.07) - 3.78 (3.55 to 3.99). In the control group, the Pre - Post - Follow-up mean (95% CI) was 4.29 (4.01 to 4.56) - 3.86 (3.60 to 4.11) - 4.05 (3.82 to 4.27) for pain at rest. In the experimental group, the Pre - Post - Follow-up mean (95% CI) was 4.91 (4.63 to 5.19) - 4.00 (3.76 to 4.24) - 3.69 (3.69 to 4.22), while in the control group, the Pre - Post - Follow-up mean (95% CI) was 4.81 (4.53 to 5.09) - 4.38 (4.13 to 4.63) - 4.57 (4.30 to 4.85) for pain while driving. PPT on the right (p = 0.029) and left (p < 0.001) sides, and neck disability (p = 0.001) also showed significant time and group interactions. NDI was not clinically significant based on the minimum clinically important difference. All CROM showed significant time and group interactions (flexion, p = 0.008; right lateral flexion, p = 0.009; left lateral flexion, p = 0.004; right rotation, p = 0.001; left rotation, p = 0.001), except for extension.

CONCLUSION

This study showed that self-stretching exercises with kinesio taping provided benefits over kinesio taping alone on pain intensity, PPT, disability, and CROM in taxi drivers with nonspecific chronic neck pain.

CLINICAL TRIAL REGISTRATION

This study registered with the Clinical Research Information Service (WHO International Clinical Trials Registry Platform) on September 22, 2020 (KCT0005406).

Adaptations of bone and bone vasculature to muscular stretch training

The magnitude of bone formation and remodeling is linked to both the magnitude of strain placed on the bone and the perfusion of bone. It was previously reported that an increase in bone perfusion and bone density occurs in the femur of old rats with moderate aerobic exercise training. This study determined the acute and chronic effects of static muscle stretching on bone blood flow and remodeling. Old male Fischer 344 rats were randomized to either a naive or stretch-trained group. Static stretching of ankle flexor muscles was achieved by placement of a dorsiflexion splint on the left ankle for 30 min/d, 5d/wk for 4wk. The opposite hindlimb served as a contralateral control (nonstretched) limb. Bone blood flow was assessed during and after acute stretching in naive rats, and at rest and during exercise in stretch-trained rats. Vascular reactivity of the nutrient artery of the proximal tibia was also assessed in stretch-trained rats. MicroCT analysis was used to assess bone volume and micro-architecture of the trabecular bone of both tibias near that growth plate. In naive rats, static stretching increased blood flow to the proximal tibial metaphasis. Blood flow to the proximal tibial metaphysis during treadmill exercise was higher in the stretched limb after 4 wk of daily stretching. Daily stretching also increased tibial bone weight and increased total volume in both the proximal and distal tibial metaphyses. In the trabecular bone immediately below the proximal tibial growth plate, total volume and bone volume increased, but bone volume/total volume was unchanged and trabecular connectivity decreased. In contrast, intravascular volume increased in this region of the bone. These data suggest that blood flow to the tibia increases during bouts of static stretching of the hindlimb muscles, and that 4 wk of daily muscle stretching leads to bone remodeling and an increase in intravascular volume of the tibial bone.

Using multi-channel near-infrared spectroscopy to assess the effect of cupping therapy on the spatial hemodynamic response of the biceps muscle: A preliminary study

BACKGROUND

The local hemodynamic response after cupping therapy has been considered as a contributing factor for improving muscle tissue health; however, the effects of cupping pressure and duration on the spatial hemodynamic response have not been investigated.

OBJECTIVE

The objective of this study was to investigate the hemodynamic response inside and outside the cupping cup under various pressures and durations of cupping therapy.

METHODS

A 3-way factorial design with repeated measures was used to investigate the main and interaction effects of the location (areas inside and outside the cup), pressure (-225 and -300 mmHg) and duration (5 and 10 min) on the hemodynamic response of the biceps muscle. A functional near-infrared spectroscopy was used to assess hemodynamic changes in 18 participants.

RESULTS

A significant three-way interaction of the location, pressure, and duration factors was observed in oxyhemoglobin (p= 0.023), deoxy-hemoglobin (p= 0.013), and blood volume (p= 0.013). A significant increase was observed in oxyhemoglobin, blood volume, and oxygenation compared to pre-cupping (p< 0.05) in the area outside the cup.

CONCLUSION

Our findings indicate that an appropriate combination of cupping pressure and duration can effectively affect the spatial hemodynamic response of the biceps.

Pathogenesis of Musculotendinous and Fascial Injuries After Physical Exercise - Short Review

Purpose

The identification of sports and physical exercises with injury risk is necessary to preserve the capacity of athletes and people who perform physical education and also to prevent the installation of functional deficiencies.

Methods

We have selected the articles related to the pathogenic mechanisms involved in musculotendinous and fascial injuries produced as a result of physical exercise.

Results and Discussions

The lesional pathogenesis is complex and incompletely clarified. Recent theories put in a new light the mechanisms of muscle pain and tendinopathy production. The accumulation of lactate anion, known to be a residue that induces fatigue and muscle pain, has been reconsidered by some authors. It appears that lactate anion is an excellent fuel for the myocardial fiber. Moreover, the accumulation of lactic acid after intense physical exercise could prevent the inexcitability of the sarcolemma induced by the increased concentration of interstitial K+. Most of the time, overuse injuries are not limited to muscles. They can cause myofascial, myotendinous or purely muscular injuries. The muscular fascia is more susceptible to injuries produced under the action of large external forces. Also, fascia is more sensitive to pain compared to muscle when external forces act eccentrically. Overloading the tendon and putting it under tension repeatedly is followed by ruptures of the tendon fibers. The regeneration of the degenerated tendon is defective in the context of the inflammation produced by the injury. Tendon fibers undergo a process of fibrosis, scarring, adhesion and heterogeneous calcification. Oxidative stress is responsible for inflammation, degeneration and apoptosis of tenocytes.

Conclusion

The benefits brought by physical education and sports are indisputable, but their practice requires a coordinated program to prevent possible traumatic and overuse injuries.

Fourteen weeks of multicomponent training associated with flexibility training modifies postural alignment, joint range of motion and modulates blood pressure in physically inactive older women: a randomized clinical trial

Background: Body relaxation and pain reduction are some of the reported benefits of flexibility training (through active stretching exercises), however their effects on posture and blood circulation are uncertain. We aimed to investigate the effects of flexibility training (through active stretching exercises) in combination with multicomponent training (MT) on blood pressure (BP), and the correlation with changes in body alignment and flexibility in physically inactive women. Methods: Women aged 60-70 years were into three groups: multicomponent training group (MT), multicomponent training plus flexibility training group (FT), and control group (CG). After randomization, the resting blood pressure was measured and the participants were reallocated into subgroups according to pressure values >130/80 mmHg (This classification is according to the American Heart Association (AHA), resulting in the subgroups: flexibility training (FT); flexibility training for hypertensive patients (FTSAH); multicomponent training (MT); multicomponent training for hypertensive patients (MTSAH); control group (CG); control group of hypertensive patients (CGSAH). The interventions lasted 14 weeks. Systolic (sBP) and diastolic (dBP) BP, range of motion (flexion and extension), and postural analysis by asymmetry in the frontal plane and asymmetry in the sagittal plane, displacement and the flexibility test were collected before (Pre) and after training (Post). In total, 141 women participated in the study (without SAH: FT = 23, MT = 20, and CG = 21; with SAH: FTSAH = 28, MTSAH = 23, and CGSAH = 26). Results: Systolic blood pressure, in the pre and post moments were: FT (116 ± 6.7 vs. 114 ± 4.7); FTSAH (144 ± 16.5 vs. 121 ± 10.1); MT: (120 ± 6.8 vs. 121 ± 7.3); MTSAH: (137 ± 10.6 vs. 126 ± 13.0); CG: (122 ± 5.3 vs. 133 ± 19.2); and CGSAH: (140 ± 9.7 vs. 143 ± 26.2), presenting an F value (p-value - group x time) of 12.00 (<0.001), with improvement in the groups who trained. The diastolic blood pressure in the pre and post moments were: FT (71 ± 4.7 vs. 74 ± 6.8); FTSAH (88 ± 9.6 vs. 70 ± 12.0); MT: (74 ± 4.5 vs. 77 ± 11.7); MTSAH: (76 ± 10.4 vs. 76 ± 10.2); CG: (69 ± 7.11 vs. 82 ± 11.4); and CGSAH: (76 ± 13.4 vs. 86.6 ± 7.7), presenting an F value (p-value - group x time) of 8.00 (p < 0.001), with improvement in the groups who trained. In the Elastic Net Regression, sBP was influenced by height (β: -0.044); hip flexion (β: 0.071); Shoulder extension (β: 0.104); low back flexion (β: 0.119) and dBP (β: 0.115). In the Elastic Net Regression, dBP was influenced by asymmetry in the sagittal plane variables (0.040); asymmetry in the frontal plane (β: 0.007); knee flexion (β: -0.398); BM (β: 0.007); Shoulder flexion (β: -0.142); Hip flexion (β: -0.004); sBP (β: 0.155) and Ankle Flexion (β: -0.001). Conclusion: The displacement of the asymmetry in the frontal plane and asymmetry in the sagittal plane, and the increase in the flexion position in the hip, lumbar, head, and knee regions, influenced the highest-pressure levels. Multicomponent training associated with flexibility training promoted improvement in body alignment, COM, and joint angles, and decreased blood pressure.

Physiology of Stretch-Mediated Hypertrophy and Strength Increases: A Narrative Review

Increasing muscle strength and cross-sectional area is of crucial importance to improve or maintain physical function in musculoskeletal rehabilitation and sports performance. Decreases in muscular performance are experienced in phases of reduced physical activity or immobilization. These decrements highlight the need for alternative, easily accessible training regimens for a sedentary population to improve rehabilitation and injury prevention routines. Commonly, muscle hypertrophy and strength increases are associated with resistance training, typically performed in a training facility. Mechanical tension, which is usually induced with resistance machines and devices, is known to be an important factor that stimulates the underlying signaling pathways to enhance protein synthesis. Findings from animal studies suggest an alternative means to induce mechanical tension to enhance protein synthesis, and therefore muscle hypertrophy by inducing high-volume stretching. Thus, this narrative review discusses mechanical tension-induced physiological adaptations and their impact on muscle hypertrophy and strength gains. Furthermore, research addressing stretch-induced hypertrophy is critically analyzed. Derived from animal research, the stretching literature exploring the impact of static stretching on morphological and functional adaptations was reviewed and critically discussed. No studies have investigated the underlying physiological mechanisms in humans yet, and thus the underlying mechanisms remain speculative and must be discussed in the light of animal research. However, studies that reported functional and morphological increases in humans commonly used stretching durations of > 30 min per session of the plantar flexors, indicating the importance of high stretching volume, if the aim is to increase muscle mass and maximum strength. Therefore, the practical applicability seems limited to settings without access to resistance training (e.g., in an immobilized state at the start of rehabilitation), as resistance training seems to be more time efficient. Nevertheless, further research is needed to generate evidence in different human populations (athletes, sedentary individuals, and rehabilitation patients) and to quantify stretching intensity.

Preexercise intermittent passive stretching and vascular function after treadmill exercise

Acute aerobic exercise stress is associated with decreased endothelial function that may increase the likelihood of an acute cardiovascular event. Passive stretch (PS) elicits improvements in vascular function, but whether PS can be performed before exercise to prevent declines in vascular function remains unknown. This strategy could be directly applicable in populations that may not be able to perform dynamic exercise. We hypothesized that preexercise PS would provide better vascular resilience after treadmill exercise. Sixteen healthy college-aged males and females participated in a single laboratory visit and underwent testing to assess micro- and macrovascular function. Participants were randomized into either PS group or sham control group. Intermittent calf PS was performed by having the foot in a splinting device for a 5-min stretch and 5-min relaxation, repeated four times. Then, a staged V̇o2 peak test was performed and 65% V̇o2 peak calculated for subjects to run at for 30 min. Near-infrared spectroscopy-derived microvascular responsiveness was preserved with the PS group [(pre: 0.53 ± 0.009%/s) (post: 0.56 ± 0.012%/s; P = 0.55)]. However, there was a significant reduction in the sham control group [(pre: 0.67 ± 0.010%/s) (post: 0.51 ± 0.007%/s; P = 0.05)] after treadmill exercise. Flow-mediated vasodilation (FMD) of the popliteal artery showed similar responses. In the PS group, FMD [(pre: 7.23 ± 0.74%) (post: 5.86 ± 1.01%; P = 0.27)] did not significantly decline after exercise. In the sham control group, FMD [(pre: 8.69 ± 0.72%) (post: 5.24 ± 1.24%; P < 0.001)] was significantly reduced after treadmill exercise. Vascular function may be more resilient if intermittent PS is performed before moderate-intensity exercise and, importantly, can be performed by most individuals.NEW & NOTEWORTHY We demonstrate for the first time that popliteal artery and gastrocnemius microvascular responsiveness after acute aerobic exercise are reduced. The decline in vascular function was mitigated in those who performed intermittent passive stretching before the exercise bouts. Collectively, these findings suggest that intermittent passive stretching is a novel method to increase vascular resiliency before aerobic activity.

Effects of the Foam Massage Roller on VEGF-A and FGF-2 Blood Levels in Young Men

BACKGROUND/AIM

Angiogenesis induced in muscles or massaged tissue is thought to support their regeneration and performance. Therefore, different methods that could promote angiogenesis are investigated. The aim of this study was to examine whether the use of the foam roller massager for lower limb muscles affects VEGF-A and FGF-2 levels in young men.

MATERIALS AND METHODS

The study group included 60 healthy young men attending Military University of Land Forces, Wroclaw, Poland. The participants were randomly divided into two groups. The experimental group included 40 individuals who performed self-massage of the lower limbs using a foam roller. The control group comprised 20 individuals who did not perform massage. Massage was applied to lower limb muscles four times a week for seven weeks. Blood was collected before the experiment and after weeks 1, 3, 5, and 7. ELISA was used to determine changes in VEGF-A and FGF-2 levels in blood serum.

RESULTS

The results of the study demonstrated a significant increase in VEGF-A serum levels in the group of individuals who underwent massage each week compared to VEGF-A concentrations before the experiment. The increase in VEGF-A levels in the experimental group was observed throughout the experiment compared to the control group. No significant changes in serum FGF-2 levels were found.

CONCLUSION

The use of a foam massage roller increased VEGF-A serum levels, which may indicate stimulation of angiogenesis.

Dynamic and static stretching on hamstring flexibility and stiffness: A systematic review and meta-analysis

INTRODUCTION

Hamstring injuries are one of the most common types of damage in sports. Insufficient flexibility and high stiffness are important reasons for it. Stretching is often used in warm-up activities before exercises to increase flexibility, among which dynamic stretching (DS) and static stretching (SS) are the most widely used. The effects of these two stretching techniques on the flexibility or stiffness of the hamstring still need to be clarified.

OBJECTIVE

This study aimed to compare the short-term, medium-term, and long-term effects of DS and SS on improving hamstring flexibility and stiffness via a meta-analysis of RCTs.

METHODS

RCTs were identified from PubMed, Cochrane Library, Web of Science, and PEDro from inception to July 28, 2022. The methodological quality was evaluated using the PEDro scale. The mean difference and 95% confidence interval of the outcome variables before and after stretching were calculated and the extracted data were quantitatively processed using a random or fixed effects model.

RESULTS

A total of 27 RCTs and 606 participants were included. In terms of improving the ROM of the hamstring, there was no significant difference in the acute (MD, -0.70, 95% CI, -1.54 to 0.14; Z = 1.63, P > 0.05) and sub-acute effects (MD, 1.71, 95% CI, -2.80 to 6.22; Z = 0.74, P > 0.05) between a single bout of SS and DS, while the acute (MD, -5.13, 95% CI, -7.65 to -2.61; Z = 3.99, P < 0.05) and sub-acute effects (MD, -5.30, 95% CI, -6.33 to -4.27; Z = 10.04, P < 0.05) of multiple bouts of SS was superior to DS; There was no significant difference in the medium-term effect between the two stretching techniques (MD, 3.48, 95% CI, -2.57 to 9.53; Z = 1.13, P > 0.05), but the long-term effect of SS was better than DS (MD, - 10.40, 95% CI, -10.97 to -9.83; Z = 35.57, P < 0.05). Regarding the length of the hamstring, the acute (MD, -0.41, 95% CI, -1.09 to 0.26; Z = 1.20, P > 0.05) and sub-acute effects (MD, -0.73, 95% CI, -1.69 to 0.22; Z = 1.51, P > 0.05) of a single bout of DS and SS were similar. Two studies have compared the effects on hamstring stiffness, with one showing similar effects, and the other showed that DS was superior to SS. One study showed no difference in the magnitude of change in improving passive torque. No studies explored the effect of DS and SS on hamstring myofascial length. Only one study demonstrated no significant difference in hamstring thickness.

CONCLUSIONS

A single bout of DS and SS have similar short-term effects in improving hamstring ROM and length, while multiple bouts of SS can significantly improve hamstring ROM compared to DS. DS and SS showed similar effects on hamstring myofascial length.

Hamstrings fascicle length and physical performance changes after a single bout of dynamic stretching or neurodynamic gliding in healthy young and older adults

INTRODUCTION

The physiological and structural alterations have been less reported in response to dynamic stretching (DS) or neurodynamic nerve gliding (NG). Accordingly, this study investigated the changes in fascicle lengths (FL), popliteal artery velocity, and physical fitness in response to a single bout of DS or NG.

METHODS

The study included 15 healthy young adults (20.9 ± 0.7 yrs) and 15 older adults (66.6 ± 4.2 yrs) who randomly performed three different interventions (DS, NG, and rest control) for 10 min and 3 days apart. The biceps femoris and semitendinosus FL, popliteal artery velocity, sit and reach (S&R), straight leg raise (SLR), and fast walking speed were measured before and immediately after the intervention.

RESULTS

After NG intervention, S&R was largely greater by 2 cm (1.2, 2.8 cm) and 3.4 cm (2.1, 4.7 cm) with largely increased SLR angles of 4.9° (3.7°, 6.1°) and 4.6° (3.0°, 6.2°) with all p < 0.001 for the older adults and young groups, respectively. A similar magnitude improvement in the S&R and SLR testing was also seen for both groups after DS (p < 0.05). Moreover, no changes were seen in FL, popliteal artery velocity, fast gait speed, and age effect following all three intervention occasions.

CONCLUSION

Stretching with DS or NG immediately increased flexibility, which appeared to be largely due to changes in stretch tolerance rather than an increase in fascicle length. Furthermore, age dependency in response to stretching exercise was not seen in the present study.

Effects of acute cervical stretching on arterial wall elastic properties

Purpose: Acute (immediate) or regular (mid- or long-term) stretching increases arterial compliance and reduces arterial stiffness. Stretching is widely known to induce arterial functional factor changes, but it is unclear whether stretching alters arterial structural factors. Ultrasound shear wave elastography can quantify the distribution of tissue elastic properties as an index of arterial structural factors. This study thus aimed to examine the effects of acute cervical stretching on arterial wall tissue elastic properties. Methods: Seventeen healthy young adults participated in two different trials for 15 min in random order on separate days: a resting and sitting trial (CON) and a supervised cervical stretching trial (CS). In CS, subjects performed 10 different stretches. At each site, the stretch was held for 30 s followed by a 10-s relaxation period. In CON, subjects rested on a chair for 15 min. Results: After the experiment, carotid arterial compliance, assessed by combined ultrasound imaging and applanation tonometry, was significantly increased in CS, but not in CON. However, there was no significant change in tissue elasticity properties of the arterial wall in either trial, as assessed by ultrasound shear wave elastography. Conclusion: Acute cervical stretching significantly increased carotid artery compliance in young participants, but did not reduce elastic tissue properties (i.e., arterial structural factors) of the carotid artery wall. These results strongly suggest that changes in structural factors have little relation to stretching-induced acute increases in arterial compliance.

Association between Yoga Participation and Arterial Stiffness: A Cross-Sectional Study

BACKGROUND

Yoga may help adults of all fitness levels increase their physical activity and decrease their cardiovascular disease risk.

AIM

To determine if arterial stiffness is lower (beneficial) in yoga versus non-yoga participants.

METHOD

This cross-sectional study included 202 yoga (48.4 + 14.1 years, 81% female) and 181 (42.8 + 14.1 years, 44% female) non-yoga participants. The primary outcome was carotid-femoral pulse wave velocity (cfPWV). The two groups were compared using analysis of covariance with adjustments for demographic (age and sex), hemodynamic (mean arterial pressure and heart rate), lifestyle (physical activity levels, sedentary behaviour, smoking status and perceived stress score) and cardiometabolic (waist-to-hip ratio, total cholesterol and fasting glucose) factors.

RESULTS

Following adjustments, cfPWV was significantly lower in yoga compared to non-yoga participants with a mean difference: -0.28 m.s^-1, (95% CI = -0.55 to 0.08).

CONCLUSION

At a population level, yoga participation may assist with decreasing the risk of cardiovascular disease in adults.

Immediate Effects of Myofascial Release Treatment on Lumbar Microcirculation: A Randomized, Placebo-Controlled Trial

(1) Background: Inflammatory processes in the thoracolumbar fascia (TLF) lead to thickening, compaction, and fibrosis and are thought to contribute to the development of nonspecific low back pain (nLBP). The blood flow (BF) of fascial tissue may play a critical role in this process, as it may promote hypoxia-induced inflammation. The primary objective of the study was to examine the immediate effects of a set of myofascial release (MFR) techniques on the BF of lumbar myofascial tissue. The secondary objectives were to evaluate the influence of TLF morphology (TLFM), physical activity (PA), and body mass index (BMI) on these parameters and their correlations with each other. (2) Methods: This study was a single-blind, randomized, placebo-controlled trial. Thirty pain-free subjects (40.5 ± 14.1 years) were randomly assigned to two groups treated with MFR or a placebo intervention. Correlations between PA, BMI, and TLFM were calculated at baseline. The effects of MFR and TLFM on BF (measured with white light and laser Doppler spectroscopy) were determined. (3) Results: The MFR group had a significant increase in BF after treatment (31.6%) and at follow-up (48.7%) compared with the placebo group. BF was significantly different between disorganized and organized TLFM (p < 0.0001). There were strong correlations between PA (r = -0.648), PA (d = 0.681), BMI (r = -0.798), and TLFM. (4) Conclusions: Impaired blood flow could lead to hypoxia-induced inflammation, possibly resulting in pain and impaired proprioceptive function, thereby likely contributing to the development of nLBP. Fascial restrictions of blood vessels and free nerve endings, which are likely associated with TLFM, could be positively affected by the intervention in this study.

Cross-sectional and longitudinal associations between body flexibility and sarcopenia

BACKGROUND

The associations between body flexibility and sarcopenia were not well understood. This study aimed to explore the cross-sectional and longitudinal associations of flexibility with sarcopenia.

METHODS

Our study selected participants aged 50-80 from the WELL-China cohort and the Lanxi cohort. Participants from the urban area of the Lanxi cohort were followed up 4 years later. Body flexibility was measured by the sit-and-reach test. Muscle mass was evaluated by dual-energy X-ray absorptiometry. Muscle strength was evaluated using handgrip strength. Sarcopenia was defined as having both low muscle mass and low muscle strength. We used multivariable logistic regressions to assess the cross-sectional associations of body flexibility with low muscle mass, low muscle strength and sarcopenia. We also used multivariable logistic regressions to explore the associations of baseline flexibility and 4-year changes in flexibility with incident low muscle mass, low muscle strength and sarcopenia.

RESULTS

A total of 9453 participants were enrolled in the cross-sectional study, and 1233 participants were included in the longitudinal analyses. In the cross-sectional analyses, compared with low body flexibility, high body flexibility was inversely associated with low muscle mass (odds ratio [OR], 0.58; 95% confidence interval [CI], 0.50-0.68; P < 0.001), low muscle strength (OR, 0.62; 95% CI, 0.55-0.69; P < 0.001) and sarcopenia (OR, 0.52; 95% CI, 0.41-0.65; P < 0.001), and these associations did not differ in different age groups, sex or physical activity levels. In the longitudinal analyses, compared with participants with low body flexibility, participants with high body flexibility had lower risk of the incident low muscle strength (OR, 0.53; 95% CI, 0.38-0.74; P < 0.001) and sarcopenia (OR, 0.36; 95% CI, 0.21-0.61; P < 0.001), but not incident low muscle mass (OR, 0.59; 95% CI, 0.33-1.06; P = 0.076). Every 1-cm increase in flexibility during 4 years was associated with reduced risk of incident low muscle mass (OR, 0.96; 95% CI, 0.93-1.00; P = 0.025), low muscle strength (OR, 0.96; 95% CI, 0.94-0.98; P = 0.002) and sarcopenia (OR, 0.96; 95% CI, 0.93-0.99; P = 0.007).

CONCLUSIONS

High flexibility was associated with reduced risk of incident low muscle strength and sarcopenia. Increases in flexibility were associated with reduced risk of incident low muscle mass, low muscle strength and sarcopenia. Flexibility exercises and monitoring the dynamic change of flexibility might be helpful in preventing sarcopenia among adults aged 50 years or over.

Using Daily Stretching to Counteract Performance Decreases as a Result of Reduced Physical Activity-A Controlled Trial

There are many reasons for reduced physical activity leading to reduced maximal strength and sport-specific performance, such as jumping performance. These include pandemic lockdowns, serious injury, or prolonged sitting in daily work life. Consequently, such circumstances can contribute to increased morbidity and reduced physical performance. Therefore, a demand for space-saving and home-based training routines to counteract decreases in physical performance is suggested in the literature. This study aimed to investigate the possibility of using daily static stretching using a stretching board to counteract inactivity-related decreases in performance. Thirty-five (35) participants were either allocated to an intervention group (IG), performing a daily ten-minute stretch training combined with reduced physical activity or a reduced physical activity-only group (rPA). The effects on maximal voluntary contraction, range of motion using the knee-to-wall test, countermovement jump height (CMJ_height), squat jump height (SJ_height), drop jump height (DJ_height), contact time (DJ_ct) and the reactive strength index (DJ_RSI) were evaluated using a pre-test-post-test design. The rPA group reported reduced physical activity because of lockdown. Results showed significant decreases in flexibility and jump performance (d = -0.11--0.36, p = 0.004-0.046) within the six weeks intervention period with the rPA group. In contrast, the IG showed significant increases in MVC90 (d = 0.3, p < 0.001) and ROM (d = 0.44, p < 0.001) with significant improvements in SJ_height (d = 0.14, p = 0.002), while no change was measured for CMJ_height and DJ performance. Hence, 10 min of daily stretching seems to be sufficient to counteract inactivity-related performance decreases in young and healthy participants.

Influence of One Hour versus Two Hours of Daily Static Stretching for Six Weeks Using a Calf-Muscle-Stretching Orthosis on Maximal Strength

Rebuilding strength capacity is of crucial importance in rehabilitation since significant atrophy due to immobilization after injury and/or surgery can be assumed. To increase maximal strength (MSt), strength training is commonly used. The literature regarding animal studies show that long-lasting static stretching (LStr) interventions can also produce significant improvements in MSt with a dose-response relationship, with stretching times ranging from 30 min to 24 h per day; however, there is limited evidence in human studies. Consequently, the aim of this study is to investigate the dose-response relationship of long-lasting static stretching on MSt. A total of 70 active participants (f = 30, m = 39; age: 27.4 ± 4.4 years; height: 175.8 ± 2.1 cm; and weight: 79.5 ± 5.9 kg) were divided into three groups: IG1 and IG2 both performed unilateral stretching continuously for one (IG1) or two hours (IG2), respectively, per day for six weeks, while the CG served as the non-intervened control. MSt was determined in the plantar flexors in the intervened as well as in the non-intervened control leg to investigate the contralateral force transfer. Two-way ANOVA showed significant interaction effects for MSt in the intervened leg (ƞ² = 0.325, p < 0.001) and in the contralateral control leg (ƞ² = 0.123, p = 0.009), dependent upon stretching time. From this, it can be hypothesized that stretching duration had an influence on MSt increases, but both durations were sufficient to induce significant enhancements in MSt. Thus, possible applications in rehabilitation can be assumed, e.g., if no strength training can be performed, atrophy could instead be reduced by performing long-lasting static stretch training.

Acute effect of resistance exercise at different velocities on stiffness and vascularity of the biceps brachii muscle: a preliminary study

Background

Resistance exercise can be defined as the percentage of maximal strength (%1 repetition maximum) used for a particular exercise. Shear wave elastography (SWE) is a robust and novelty imaging technique that provides information regarding tissue stiffness. Superb microvascular imaging (SMI) is a non-irradiating technique that can provide quantitative measurement of muscle blood flow non-invasively.

Purpose

To compare the acute effects of low- and high-velocity resistance exercise on stiffness and blood flow in the biceps brachii muscle (BBM) using SWE and SMI.

Material and Methods

This prospective study included 60 healthy men (mean age=28.9 years; age range=26–34 years). BBM stiffness was measured by using SWE at rest, after low- and high-velocity resistance exercise, and muscle blood flow was also evaluated by SMI. Resistance exercise was performed using a dumbbell with a mass adjusted to 70%–80% of one-repetition maximum.

Results

The stiffness values increased significantly from resting to high- and low-velocity resistance exercises. There was no significant difference between the elastography values of the BBM after the high- and low-velocity resistance exercise. The blood flow increased significantly from resting to high- and low-velocity resistance exercises. Blood flow increase after low-velocity exercise was significantly higher compared to high-velocity exercise.

Conclusion

While muscle stiffness parameters and blood flow significantly increased from resting after both high- and low-velocity resistance exercises, blood flow significantly increased after low-velocity exercise compared to high-velocity exercise. This can mean that metabolic stress, an important trigger for muscle development, is more likely to occur in low-velocity exercise.

Mechanisms Underlying Anti-Inflammatory and Anti-Cancer Properties of Stretching-A Review

Stretching is one of the popular elements in physiotherapy and rehabilitation. When correctly guided, it can help minimize or slow down the disabling effects of chronic health conditions. Most likely, the benefits are associated with reducing inflammation; recent studies demonstrate that this effect from stretching is not just systemic but also local. In this review, we present the current body of knowledge on the anti-inflammatory properties of stretching at a molecular level. A total of 22 papers, focusing on anti-inflammatory and anti-cancer properties of stretching, have been selected and reviewed. We show the regulation of oxidative stress, the expression of pro- and anti-inflammatory genes and mediators, and remodeling of the extracellular matrix, expressed by changes in collagen and matrix metalloproteinases levels, in tissues subjected to stretching. We point out that a better understanding of the anti-inflammatory properties of stretching may result in increasing its importance in treatment and recovery from diseases such as osteoarthritis, systemic sclerosis, and cancer.

Microvascular Adaptations to Muscle Stretch: Findings From Animals and the Elderly

Microcirculation in skeletal muscle is disturbed with advancing aging, causing limited capillary blood flow and exercise incapacity. Muscle stretch has been widely performed in physical therapy, sports medicine, and health promotion. However, the effect of stretch on microvascular reactivity and muscle blood flow remains unknown. This review focuses on stretch-induced microvascular adaptations based on evidence from cultured cells, small animals, and human studies. Vascular endothelium senses and responds to mechanical stimuli including stretch. This endothelial mechanotransduction potentially plays a vital role in the stretch-induced microvascular adaptation alongside hypoxia. Aging impairs microvascular endothelial function, but muscle stretch has the potential to restore it. Muscle stretch may be an alternative to improve vascular function and enhance exercising blood flow, especially for those who have difficulties in participating in exercise due to medical, functional, or psychological reasons.

Four weeks of lower-limb static stretching reduces regional arterial stiffness in middle-aged and older women

[Purpose]

This study aimed to clarify whether habitual lower-limb stretching intervention reduces regional arterial stiffness at the stretched site in middle-aged and older women.

[Methods]

In this study, the effects of 4 weeks of lower-limb static stretching (of the hip extensor and flexor, knee extensor and flexor, and plantar flexor muscles) were investigated on systemic, central, and peripheral arterial stiffness using pulse wave velocity in 14 healthy middle-aged and older women randomly assigned to either a sedentary control group (67.3 ± 5.6 years; n = 7) or a stretching intervention group (63.4 ± 6.4 years; n = 7).

[Results]

The femoral-ankle pulse wave velocity (an index of peripheral arterial stiffness) significantly decreased in the intervention group (pre, 1222.4 ± 167.5 cm/s; post, 1122.0 ± 141.1 cm/s) but did not change in the control group (pre, 1122.7 ± 107.7 cm/s; post, 1139.9 ± 77.5 cm/s). However, the brachial-ankle pulse wave velocity as an index of systemic arterial stiffness (control: pre, 1655.7 ± 296.8 cm/s, post, 1646.4 ± 232.1 cm/s; intervention: pre, 1637.6 ± 259.9 cm/s, post, 1560.8 ± 254.7 cm/s) and the carotid-femoral pulse wave velocity as an index of central arterial stiffness (control: pre, 1253.6 ± 346.4 cm/s, post, 1223.6 ± 263.4 cm/s; intervention: pre, 1125.4 ± 204.7 cm/s, post, 1024.9 ± 164.5 cm/s) did not change in either group.

[Conclusion]

These findings suggest that lower-limb stretching interventions may reduce regional arterial stiffness at the stretched site

Compliance of Static Stretching and the Effect on Blood Pressure and Arteriosclerosis Index in Hypertensive Patients

Background: Treatment of high blood pressure is a combination of lifestyle changes and medications, and appropriateexercise therapy is recommended as one of the lifestyle-related changes. Recently, stretching, a low-intensity exercise, was reported to be antihypertensive and effective for improving arteriosclerosis, in addition to aerobic exercise. The present study investigated the short-term effects of continuous stretching and rest-induced rebound on vascular endothelial function in hypertensive patients. Methods: This study was conducted as a single-arm prospective interventional study including patients between 30 and 70 years of age undergoing treatment for hypertension from October 2019 until May 2021. The intervention consisted of six months of daily stretching, one month of rest, and another three months of stretching. We measured arteriosclerosis indices such as cardio ankle vascular index (CAVI), ankle brachial pressure index (ABI) and reactive hyperemia index (RHI), and flexibility at the baseline and one, three, six, seven, and ten months from the baseline. Results: We included a total of ten patients (three males and seven females) with an average age of 60.10 ± 6.05 years. The exercise rate for the entire period was 90% or more, and the anteflexion measurement value improved significantly before and after the intervention (p < 0.001). Blood pressure and CAVI/ABI were well controlled throughout the study period. RHI did not show any significant improvement during the initial six months, and only slightly improved by the third month (p = 0.063). Even after the rest phase and resumption of stretching, RHI remained stable. Conclusions: The compliance of the stretching program we used, evaluated by the exercise implementation rate for the entire period, was 90% or more; therefore, easy to perform and continue by hypertensive patients. However, we did not observe a significant positive effect on arteriosclerosis index or blood pressure in this study.

Regular exercise ball training reduces arterial stiffness in sedentary middle-aged males

[Purpose] Reports suggest that static stretching, which improves body flexibility, could reduce arterial stiffness. Regular training using an exercise ball would increase flexibility in a different manner, compared to that from static stretching; however, it remains unclear whether such exercise can reduce arterial stiffness. This study aimed to clarify the effect of exercise ball training on arterial stiffness in sedentary middle-aged participants. [Participants and Methods] Fifteen healthy middle-aged males (age, 52 ± 12 years) were divided into a control group (n=7, CON) and an intervention group (n=8, INT). The CON group did not alter physical activity levels throughout the study period, while the INT group participated in supervised training sessions using an exercise ball for 20-30 min, 5 days/week, for a duration of 4 weeks. [Results] Exercise ball training significantly increased the sit-and-reach test score (CON, -3.8 ± 11.1% vs. INT, 33.8 ± 47.5%) and reduced cardio-ankle vascular index (CON, -0.8 ± 4.1% vs. INT, -5.7 ± 4.1%) and heart-ankle pulse wave velocity (CON, 1.6 ± 4.5% vs. INT, -4.2 ± 4.6%), as an index of arterial stiffness. [Conclusion] Four weeks of supervised training using an exercise ball as well as regular static stretching would increase body flexibility and reduce systemic arterial stiffness among sedentary middle-aged males.

Redox balance in human skeletal muscle-derived endothelial cells - Effect of exercise training

Aerobic training can improve vascular endothelial function in-vivo. The aim of this study was to elucidate the mechanisms underlying this improvement in isolated human microvascular endothelial cells. Sedentary males, aged 57 ± 6 years completed 8 weeks of intense aerobic training. Resting muscle biopsies were obtained from the thigh muscle and used for isolation of endothelial cells (pre n = 23, post n = 16). The cells were analyzed for mitochondrial respiration, H₂O₂ emission, glycolysis, protein levels of antioxidants, NADPH oxidase, endothelial nitric oxide (NO) synthase and prostacyclin synthase (PGI₂S). In-vivo microvascular function, assessed by acetylcholine infusion and arterial blood pressure were also determined. Endothelial mitochondrial respiration and H₂O₂ formation were similar before and after training whereas the expression of superoxide dismutase and the expression of glutathione peroxidase were 2.4-fold (p = 0.012) and 2.3-fold (p = 0.006) higher, respectively, after training. In-vivo microvascular function was increased by 1.4-fold (p = 0.036) in parallel with a 2.1-fold increase in endothelial PGI₂S expression (p = 0.041). Endothelial cell glycolysis was reduced after training, as indicated by a 65% lower basal production of lactate (p = 0.003) and a 30% lower expression of phosphofructokinase (p = 0.011). Subdivision of the participants according to blood pressure at base-line (n = 23), revealed a 2-fold higher (p = 0.049) rate of H₂O₂ production in endothelial cells from hypertensive participants. Our data show that exercise training increases skeletal muscle microvascular endothelial cell metabolism, antioxidant capacity and the capacity to form prostacyclin. Moreover, elevated blood pressure is associated with increased endothelial mitochondrial ROS formation.

Evaluation of Local Skeletal Muscle Blood Flow in Manipulative Therapy by Diffuse Correlation Spectroscopy

Manipulative therapy (MT) is applied to motor organs through a therapist’s hands. Although MT has been utilized in various medical treatments based on its potential role for increasing the blood flow to the local muscle, a quantitative validation of local muscle blood flow in MT remains challenging due to the lack of appropriate bedside evaluation techniques. Therefore, we investigated changes in the local blood flow to the muscle undergoing MT by employing diffuse correlation spectroscopy, a portable and emerging optical measurement technology that non-invasively measures blood flow in deep tissues. This study investigated the changes in blood flow, heart rate, blood pressure, and autonomic nervous activity in the trapezius muscle through MT application in 30 volunteers without neck and shoulder injury. Five minutes of MT significantly increased the median local blood flow relative to that of the pre-MT period (p &lt; 0.05). The post-MT local blood flow increase was significantly higher in the MT condition than in the control condition, where participants remained still without receiving MT for the same time (p &lt; 0.05). However, MT did not affect the heart rate, blood pressure, or cardiac autonomic nervous activity. The post-MT increase in muscle blood flow was significantly higher in the participants with muscle stiffness in the neck and shoulder regions than in those without (p &lt; 0.05). These results suggest that MT could increase the local blood flow to the target skeletal muscle, with minimal effects on systemic circulatory function.

Acute Hemodynamic Responses to Three Types of Hamstrings Stretching in Senior Athletes

Although stretching is recommended for fitness and health, there is little research on the effects of different stretching routines on hemodynamic responses of senior adults. It is not clear whether stretching can be considered an aerobic exercise stimulus or may be contraindicated for the elderly. The purpose of this study was to compare the effect of three stretching techniques; contract/relax proprioceptive neuromuscular facilitation (PNF), passive straight-leg raise (SLR), and static sit-and-reach (SR) on heart rate (HR) and blood pressure (BP) in senior athletes (119 participants: 65.6 ± 7.6 yrs.). Systolic blood pressure (SBP), diastolic blood pressure (DBP), mean arterial pressure (MAP) and HR measurements were taken at baseline (after 5-minutes in a supine position), 45 and 90-seconds, during the stretch, and 2-minutes after stretching. Within each stretching group, (SLR, PNF, and SR) DBP, MAP and HR at pre-test and 2-min post-stretch were lower than at 45-s and 90-s during the stretch. SLR induced smaller increases in DBP and MAP than PNF and SR, whereas PNF elicited lower HR responses than SR. In conclusion, trained senior adult athletes experienced small to moderate magnitude increases of hemodynamic responses with SLR, SR and PNF stretching, which recovered to baseline values within 2-min after stretching. Furthermore, the passive SLR induced smaller increases in BP than PNF and SR, while PNF elicited lower HR responses than SR. These increases in hemodynamic responses (HR and BP) were not of a magnitude to be clinically significant, provide an aerobic exercise stimulus or warrant concerns for most senior athletes.

Endothelial dysfunction: a therapeutic target in bacterial sepsis?

INTRODUCTION

Endothelial cells maintain vascular integrity, tone, and patency and have important roles in hemostasis and inflammatory responses. Although some degree of endothelial dysfunction with increased vascular permeability may be necessary to control local infection, excessive dysfunction plays a central role in the pathogenesis of sepsis-related organ dysfunction and failure as it results in dysregulated inflammation, vascular leakage, and abnormal coagulation. The vascular endothelium has thus been proposed as a potential target for therapeutic intervention in patients with sepsis.

AREAS COVERED

Different mechanisms underlying sepsis-related dysfunction of the vascular endothelium are discussed, including glycocalyx shedding, nitrosative stress, and coagulation factors. Potential therapeutic implications of each mechanism are mentioned.

EXPERT OPINION

Multiple targets to protect or restore endothelial function have been suggested, but endothelium-driven treatments remain a future potential at present. As some endothelial dysfunction and permeability may be necessary to remove infection and repair damaged tissue, targeting the endothelium may be a particular challenge. Ideally, therapies should be guided by biomarkers related to that specific pathway to ensure they are given only to patients most likely to respond. This enrichment based on biological plausibility and theragnostics will increase the likelihood of a beneficial response in individual patients and enable more personalized treatment.

The Usefulness of Magnetic Resonance Angiography to Analyze the Variable Arterial Facial Anatomy in an Effort to Reduce Filler-Associated Blindness: Anatomical Study and Visualization Through an Augmented Reality Application

BACKGROUND

The use of soft tissue fillers for facial rejuvenation is increasing rapidly and the complications, unfortunately, follow the same path. Blindness caused by intravascular filler injections is a rare but devastating complication. Knowledge of the individual arterial anatomy may aid the injector in avoiding injecting into an artery and thus to prevent blindness.

OBJECTIVES

To evaluate if the use of magnetic resonance angiography (MRA) may visualize the arterial facial anatomy in a contrast- and radiation-free way and study the individual arterial variations using an augmented reality (AR) image.

METHODS

The individual arterial anatomy of the 3 terminal branches of the ophthalmic artery (supraorbital [SO]; supratrochlear [STr]; and dorsal nasal [DN] arteries) of 20 volunteers was studied by a 3-Tesla MRI, combining infrared (IR) facial warming and 3-dimensional time-of-flight multiple overlapping thin slab acquisition MRA. The resulting visualization of the facial arteries was shown on the patient's face through AR technology.

RESULTS

The MRA was able to visualize the SO in 90.0%, STr in 92.5%, and DN arteries in 75% of the examined patients, as well as numerous variations in both vessel localization and path. Furthermore, a proof-of-concept of the AR visualization of the individual arterial anatomy was successfully implemented.

CONCLUSIONS

Dermal filler injectors should be aware of the risk of filler-induced blindness and familiarize themselves with the visualization of the variable facial vascular anatomy. The implementation of a one-time MRA and subsequent AR visualization may be useful in the accurate planning of minimally invasive facial rejuvenation procedures.

Exercise as a multi-modal disease-modifying medicine in systemic sclerosis: An introduction by The Global Fellowship on Rehabilitation and Exercise in Systemic Sclerosis (G-FoRSS)

Systemic sclerosis (SSc) is a heterogeneous multisystem autoimmune disease whereby its main pathological drivers of disability and damage are vascular injury, inflammatory cell infiltration, and fibrosis. These mechanisms result in diffuse and diverse impairments arising from ischemic circulatory dysfunction leading to painful skin ulceration and calcinosis, neurovascular aberrations hindering gastrointestinal (GI) motility, progressive painful, incapacitating or immobilizing effects of inflammatory and fibrotic effects on the lungs, skin, articular and periarticular structures, and muscle. SSc-related impairments impede routine activities of daily living (ADLs) and disrupt three critical life areas: work, family, social/leisure, and also impact on psychological well-being. Physical activity and exercise are globally recommended; however, for connective tissue diseases, this guidance carries greater impact on inflammatory disease manifestations, recovery, and cardiovascular health. Exercise, through myogenic and vascular phenomena, naturally targets key pathogenic drivers by downregulating multiple inflammatory and fibrotic pathways in serum and tissue, while increasing circulation and vascular repair. G-FoRSS, The Global Fellowship on Rehabilitation and Exercise in Systemic Sclerosis recognizes the scientific basis of and advocates for education and research of exercise as a systemic and targeted SSc disease-modifying treatment. An overview of biophysiological mechanisms of physical activity and exercise are herein imparted for patients, clinicians, and researchers, and applied to SSc disease mechanisms, manifestations, and impairment. A preliminary guidance on exercise in SSc, a research agenda, and the current state of research and outcome measures are set forth.

Human microvascular reactivity: a review of vasomodulating stimuli and non-invasive imaging assessment

The microvasculature serves an imperative function in regulating perfusion and nutrient exchange throughout the body, adaptively altering blood flow to preserve hemodynamic and metabolic homeostasis. Its normal functioning is vital to tissue health, whereas its dysfunction is present in many chronic conditions, including diabetes, heart disease, and cognitive decline. As microvascular dysfunction often appears early in disease progression, its detection can offer early diagnostic information. To detect microvascular dysfunction, one uses imaging to probe the microvasculature's ability to react to a stimulus, also known as microvascular reactivity (MVR). An assessment of MVR requires an integrated understanding of vascular physiology, techniques for stimulating reactivity, and available imaging methods to capture the dynamic response. Practical considerations, including compatibility between the selected stimulus and imaging approach, likewise require attention. In this review, we provide a comprehensive foundation necessary for informed imaging of MVR, with a particular focus on the challenging endeavor of assessing microvascular function in deep tissues.

Passive repetitive stretching is associated with greater muscle mass and cross-sectional area in the sarcopenic muscle

Mechanical stimulation has benefits for muscle mass and function. Passive stretching is widely performed in clinical rehabilitation medicine. However, the hypertrophic effects of passive repetitive stretching on senescent skeletal muscles against muscle atrophy remain unknown. We used senescence-accelerated model SAM-P8 mice. The gastrocnemius muscle was passively repetitive stretched by manual ankle dorsiflexion for 15 min, 5 days a week for 2 weeks under deep anesthesia. We examined the effects of passive stretching on muscle mass, myofiber cross-sectional area, muscle fiber type composition, satellite cell and myonuclei content, signaling pathways involved in muscle protein synthesis, and myogenic regulatory factors. The gastrocnemius muscle weight and fiber cross-sectional area of the stretched side was found greater compared with that of the unstretched side. Passive repetitive stretching increased the mRNA expression level of Akt, p70S6K, 4E-BP1, Myf5, myogenin, MuRF1.The phosphorylation level of p70S6K significantly increased in the stretched muscles, whereas of Akt and 4E-BP1 remained unchanged, compared to the unstretched side. The Pax7+ cells and myonuclei content did not differ between the stretched and unstretched muscles. These findings suggest that the hypertrophic or suppressed atrophic observation in the stretched muscles are mainly attributable to the protein turnover provoked by stretching. These findings are applicable to clinical muscle strengthening and sarcopenia prevention.

Cardiovascular Responses to Muscle Stretching: A Systematic Review and Meta-analysis

The aim of this study will be to review the current body of literature to understand the effects of stretching on the responses of the cardiovascular system. A literature search was performed using the following databases: Scopus, NLM Pubmed and ScienceDirect. Studies regarding the effects of stretching on responses of the cardiovascular system were investigated. Outcomes regarded heart rate(HR), blood pressure, pulse wave velocity (PWV of which baPWV for brachial-ankle and cfPWV for carotid-femoral waveforms), heart rate variability and endothelial vascular function. Subsequently, the effects of each outcome were quantitatively synthetized using meta-analytic synthesis with random-effect models. A total of 16 studies were considered eligible and included in the quantitative synthesis. Groups were also stratified according to cross-sectional or longitudinal stretching interventions. Quality assessment through the NHLBI tools observed a "fair-to-good" quality of the studies. The meta-analytic synthesis showed a significant effect of d=0.38 concerning HR, d=2.04 regarding baPWV and d=0.46 for cfPWV. Stretching significantly reduces arterial stiffness and HR. The qualitative description of the studies was also supported by the meta-analytic synthesis. No adverse effects were reported, after stretching, in patients affected by cardiovascular disease on blood pressure. There is a lack of studies regarding vascular adaptations to stretching.

Stretching is Superior to Brisk Walking for Reducing Blood Pressure in People With High-Normal Blood Pressure or Stage I Hypertension

BACKGROUND

Aerobic exercise is recommended for reducing blood pressure; however, recent studies indicate that stretching may also be effective. The authors compared 8 weeks of stretching versus walking exercise in men and women with high-normal blood pressure or stage 1 hypertension (ie, 130/85-159/99 mm Hg).

METHODS

Forty men and women (61.6 y) were randomized to a stretching or brisk walking exercise program (30 min/d, 5 d/wk for 8 wk). Blood pressure was assessed during sitting and supine positions and for 24 hours using a portable monitor before and after the training programs.

RESULTS

The stretching program elicited greater reductions than the walking program (P < .05) for sitting systolic (146 [9] to 140 [12] vs 139 [9] to 142 [12] mm Hg), supine diastolic (85 [7] to 78 [8] vs 81 [7] to 82 [7] mm Hg), and nighttime diastolic (67 [8] to 65 [10] vs 68 [8] to 73 [12] mm Hg) blood pressures. The stretching program elicited greater reductions than the walking program (P < .05) for mean arterial pressure assessed in sitting (108 [7] to 103 [6] vs 105 [6] vs 105 [8] mm Hg), supine (102 [9] to 96 [9] vs 99 [6] to 99 [7] mm Hg), and at night (86 [9] to 83 [10] vs 88 [9] to 93 [12] mm Hg).

CONCLUSIONS

An 8-week stretching program was superior to brisk walking for reducing blood pressure in individuals with high-normal blood pressure or stage 1 hypertension.

Fast repetitive stretch suppresses denervation-induced muscle fibrosis

BACKGROUND

We aimed to examine the influence of different speeds of stretching on denervation-induced skeletal muscle fibrosis.

METHODS

Stretching was passively applied to rat plantaris muscle denervated by sciatic nerve excision in three different cycles of 0.5, 3, or 12 cycles/min, for 20 min/d for 2 weeks.

RESULTS

Gene analysis results showed greater expression of fibrosis-related factors with fast stretching compared with non-stretched muscle. Laser Doppler blood flow analysis indicated reduced intramuscular blood flow during stretching. Histological analysis demonstrated fibrotic area decreases in 12 cycles/min stretched muscle compared with non-stretched muscle.

CONCLUSIONS

Slower stretching induced greater mRNA expression of collagen and fibroblasts and greater decrement of blood flow. Histologically, faster stretching suppressed fibrosis. These results suggest that fast repetitive stretching of denervated muscle might suppress processes of muscle fibrosis.

The Efficacy of Stretching Exercises on Arterial Stiffness in Middle-Aged and Older Adults: A Meta-Analysis of Randomized and Non-Randomized Controlled Trials

Background: Aerobic exercise is known to reduce arterial stiffness; however, high-intensity resistance exercise is associated with increased arterial stiffness. Stretching exercises are another exercise modality, and their effect on arterial stiffness remains unclear. The purpose of this study was to determine whether stretching exercises reduce arterial stiffness in middle-aged and older adults, performing the first meta-analysis of currently available studies. Methods: We searched the literature for randomized controlled trials (RCTs) and non-RCTs published up to January 2020 describing middle-aged and older adults who participated in a stretching intervention vs. controls without exercise training. The primary and secondary outcomes were changes in arterial stiffness and vascular endothelial function and hemodynamic status. Pooled mean differences (MDs) and standard MDs (SMDs) with 95% confidence intervals (CIs) between the intervention and control groups were calculated using a random effects model. Results: We identified 69 trials and, after an assessment of relevance, eight trials, including a combined total of 213 subjects, were analyzed. Muscle stretching exercises were shown to significantly reduce arterial stiffness and improve vascular endothelial function (SMD: −1.00, 95% CI: −1.57 to −0.44, p = 0.0004; SMD: 1.15, 95% CI: 0.26 to 2.03, p = 0.01, respectively). Resting heart rate (HR) and diastolic blood pressure (DBP) decreased significantly after stretching exercise intervention (MD: −0.95 beats/min, 95% CI: −1.67 to −0.23 beats/min, p = 0.009; MD: −2.72 mm Hg, 95% CI: −4.01 to −1.43 mm Hg, p < 0.0001, respectively) Conclusions: Our analyses suggest that stretching exercises reduce arterial stiffness, HR, and DBP, and improve vascular endothelial function in middle-aged and older adults.

Evidence for improved systemic and local vascular function after long-term passive static stretching training of the musculoskeletal system

KEY POINTS

Vascular function and arterial stiffness are important markers of cardiovascular health and cardiovascular co-morbidity. Transitional phases of hypoemia and hypermia, with consequent fluctuations in shear rate, occuring during repetitive passive stretching adminstration (passive stretching training) may constitute an effective stimulus to induce an amelioration in vascular function, arterial stiffness and vascular remodelling by improving central and local blood flow control mechanisms. Vascular function, arterial stiffness and vascular remodelling were evaluated before and after 12 weeks of passive stretching training and after 6 weeks from training cessation, in the femoral, popliteal (treated with stretching), and brachial arteries (untreated) of both sides. After passive stretching training, vascular function and arterial remodelling improved, and arterial stiffness decreased in all the arteries, suggesting modifications of both central and local blood flow control mechanisms. Passive stretching-induced improvements related to central mechanisms seemed to have a short duration, as they returned to pre-training baseline within 6 weeks from training cessation, whereas those more related to a local mechanism persisted in the follow-up.

ABSTRACT

Acute passive stretching (PS) effects on blood flow ( Q ̇ ), shear rate ( Y ̇ ), and vascular function in the feeding arteries of the stretched muscle have been extensively investigated; however, few data are available on vascular adjustments induced by long-term PS training. We investigated the effects of PS training on vascular function and stiffness of the involved (femoral and popliteal) and uninvolved (brachial) arteries. Our hypothesis was that PS-induced changes in Q ̇ and Y ̇ would improve central and local mechanisms of Q ̇ control. Thirty-nine participants were randomly assigned to bilateral PS (n = 14), monolateral PS (n = 13) or no PS training (n = 12). Vascular function was measured before and after 12 weeks of knee extensor and plantar flexor muscles' PS training by single passive limb movement and flow-mediated dilatation (FMD). Central (carotid-femoral artery PWV, PWV_CF ) and peripheral (carotid-radial artery PWV, PWV_CR ) arterial stiffness was measured by pulse-wave velocity (PWV), together with systolic (SBP) and diastolic (DBP) blood pressure. After PS training, increases of 30%, 25% and 8% (P < 0.05) in femoral Δ Q ̇ , popliteal and brachial artery FMD%, respectively, occurred in both PS training groups. A decrease in PWV_CF , PWV_CR , SBP and DBP (-25%, -17%, -4% and -8%, respectively; P < 0.05) was noted. No changes occurred in controls. Vascular function improved and arterial stiffness reduced in the arteries involved and uninvolved with PS training, suggesting modifications in both central and local Q ̇ control mechanisms. PS-induced improvements had a short duration in some of vascular function parameters, as they returned to baseline within 6 weeks of PS training cessation.