Intermittent Stretch Research Articles

Immediate Effects of Intermittent Bilateral Ankle Plantar Flexors Static Stretching on Balance and Plantar Pressures

ObjectiveThe purpose of this study was to analyze the immediate effects of an intermittent plantar flexion static-stretching protocol on balance and plantar pressures. MethodsThe study included a sample size of 24 healthy participants (21 female and 3 male). Participants were 32.20 ± 8.08 years, 166.20 ± 8.43 cm, and 62.77 ± 9.52 kg. All participants performed an intermittent plantar flexion static-stretching protocol. Five sets (60 seconds intermittent stretch; 15 seconds for the rest time) of a passive plantar flexor stretching (70% to 90% of the point of discomfort) were performed. Static footprint analysis and a stabilometry analysis were performed before and after stretching. A P value < .05 with a CI of 95% was considered statistically significant for all tests. ResultsIntermittent ankle plantar static stretching resulted in a significantly greater forefoot surface contact area and lower rear foot medium and maximum plantar pressures. In addition, static stretching caused a lower displacement of the center of pressure for both eyes open and eyes closed conditions. ConclusionAn intermittent plantar flexor static-stretching protocol improved balance and reduced rear foot plantar pressures (maximum and medium pressures).

Passive muscle stretching impairs rapid force production and neuromuscular function in human plantar flexors.

We examined the effect of muscle stretching on the ability to produce rapid torque and the mechanisms underpinning the changes. Eighteen men performed three conditions: (1) continuous stretch (1 set of 5min), (2) intermittent stretch (5 sets of 1min with 15-s inter-stretch interval), and (3) control. Isometric plantar flexor rate of torque development was measured during explosive maximal voluntary contractions (MVC) in the intervals 0-100ms (RTDV100) and 0-200ms (RTDV200), and in electrically evoked 0.5-s tetanic contractions (20Hz, 20Hz preceded by a doublet and 80Hz). The rate of EMG rise, electromechanical delay during MVC (EMDV) and during a single twitch contraction (EMDtwitch) were assessed. RTDV200 was decreased (P < 0.05) immediately after continuous (-15%) and intermittent stretch (-30%) with no differences between protocols. The rate of torque development during tetanic stimulations was reduced (P < 0.05) immediately after continuous (-8%) and intermittent stretch (-10%), when averaged across stimulation frequencies. Lateral gastrocnemius rate of EMG rise was reduced after intermittent stretch (-27%), and changes in triceps surae rate of EMG rise were correlated with changes in RTDV200 after both continuous (r = 0.64) and intermittent stretch (r = 0.65). EMDV increased immediately (31%) and 15min (17%) after intermittent stretch and was correlated with changes in RTDV200 (r = -0.56). EMDtwitch increased immediately after continuous (4%), and immediately (5.4%), 15min (6.3%), and 30min after (6.4%) intermittent stretch (P < 0.05). Reductions in the rate of torque development immediately after stretching were associated with both neural and mechanical mechanisms.

Possible role of rivaroxaban in attenuating pressure-overload-induced atrial fibrosis and fibrillation

BackgroundCoagulation factor Xa (FXa) promotes thrombus formation and exacerbates inflammation via activation of protease-activated receptor (PAR)-2. We tested the hypothesis of whether administration of direct oral anticoagulant, rivaroxaban, would attenuate transverse aortic constriction (TAC)-induced atrial inflammatory fibrosis and vulnerability to atrial fibrillation (AF) in mice. MethodsTen-week-old male CL57/B6 mice were divided into a sham-operation (CNT) group and TAC-surgery group. These two groups were then subdivided into vehicle (VEH) and rivaroxaban (RVX) treatment (30μg/g/day) groups. We assessed PAR-2 expression in response to TAC-related stimulation using rat cultured cells. ResultsTAC-induced left atrial thrombus formation was not observed in the TAC-RVX group. Cardiac PAR-2 upregulation was observed in both TAC groups. In the quantitative analysis of mRNA levels, cardiac PAR-2 upregulation was attenuated in the TAC-RVX group compared to TAC-VEH group. In histological evaluation, the TAC-VEH group showed cardiac inhomogeneous interstitial fibrosis and abundant infiltration of macrophages, which were attenuated by RVX administration. Electrophysiological examination revealed that AF duration in the TAC group was shortened by RVX administration. TAC-induced protein overexpression of monocyte chemoattractant protein-1, and mRNA overexpression of tumor necrosis factor-α, interleukin (IL)-1β and IL-6 in the left atrium was suppressed by RVX treatment. In cardiac fibroblasts, persistent intermittent stretch upregulated PAR-2, which was suppressed by RVX pre-incubation. ConclusionsThese observations demonstrate that coagulation FXa inhibitor probably has a cardioprotective effect against pressure-overload-induced atrial remodeling.

ラットヒラメ筋に対する廃用性筋萎縮予防としての間歇的伸張運動の効果

〔目的〕ラットヒラメ筋の廃用性萎縮進行中の間歇的伸張運動の効果を時間別，部位別に検討することとした．〔対象と方法〕8週齡のWistar系雄ラットの両側ヒラメ筋を対象に，これを通常飼育群，16日間の後肢懸垂にて廃用性筋萎縮を惹起するH群，実験期間中に間歇的伸張運動を5分間実施するSST群，10分間実施するLST群に分けた．部位は筋長の25％を近位部，50％を中央部，75％を遠位部とし，検討項目は各群と部位の筋線維横断面積，壊死線維，中心核線維の発生頻度とした．〔結果〕筋横断面積は遠位部においてLST，SST群ではH群と比較し，また中央部，遠位部においてSST群ではLST群と比較し有意に大きかった．〔結語〕短時間の伸張運動では伸張部位や時間によって廃用性筋萎縮の抑制効果が異なることが示唆される．

Fascicle length does increase in response to longitudinal resistance training and in a contraction-mode specific manner.

Fascicle length does increase in response to longitudinal resistance training and in a contraction-mode specific manner.

Intermittent stretch training of rabbit plantarflexor muscles increases soleus mass and serial sarcomere number.

In humans, enhanced joint range of motion is observed after static stretch training and results either from an increased stretch tolerance or from a change in the biomechanical properties of the muscle-tendon unit. We investigated the effects of an intermittent stretch training on muscle biomechanical and structural variables. The left plantarflexors muscles of seven anesthetized New Zealand (NZ) White rabbits were passively and statically stretched three times a week for 4 wk, while the corresponding right muscles were used as nonstretched contralateral controls. Before and after the stretching protocol, passive torque produced by the left plantarflexor muscles as a function of the ankle angle was measured. The left and right plantarflexor muscles were harvested from dead rabbits and used to quantify possible changes in muscle structure. Significant mass and serial sarcomere number increases were observed in the stretched soleus but not in the plantaris or medial gastrocnemius. This difference in adaptation between the plantarflexors is thought to be the result of their different fiber type composition and pennation angles. Neither titin isoform nor collagen amount was modified in the stretched compared with the control soleus muscle. Passive torque developed during ankle dorsiflexion was not modified after the stretch training on average, but was decreased in five of the seven experimental rabbits. Thus, an intermittent stretching program similar to those used in humans can produce a change in the muscle structure of NZ White rabbits, which was associated in some rabbits with a change in the biomechanical properties of the muscle-tendon unit.

Intermittent Stretching and Osteogenic Differentiation of Bone Marrow Derived Mesenchymal Stem Cells via the p38MAPK-Osterix Signaling Pathway

Aims: The relationship between the p38MAPK signaling pathway and osterix in osteogenic differentiation of BMMSCs subjected to intermittent stretching was investigated. Methods: BMMSCs derived from C57BL/6J mice were divided into the following groups: 1) control, 2) stretch, and 3) SB203580+stretch (SB203580 is a p38MAPK signal pathway inhibitor). BMMSCs were exposed to an intermittent mechanical strain of 0.8% (8000μ strain) at 0.5 Hz, twice a day for 30 min each application. BMMSCs were harvested on days 1, 3, and 5 post-treatment. The expression of ALP, COL I, OCN, and osterix mRNA was assessed utilizing RT-PCR while the expression of P-p38MAPK and osterix protein was assessed by Western blot analysis. The osterix gene in mouse BMMSCs was knocked down using RNAi technology and its protein expression was also assessed by Western blot. RT-PCR was used to detect ALP, COL I, and OCN mRNA expression. Results: Intermittent stretching was found to promote expression of ALP, COL I, OCN, and osterix mRNA. Silencing the osterix gene was found to reduce levels of ALP, COL I, and OCN mRNA. Western blot analysis demonstrated that the levels of osterix and P-p38MAPK proteins in the stretch group were significantly higher than in the control group (P<0.05). There was less expression of ALP, COL I, OCN, and osterix mRNA in the SB203580+stretch group than in the control and stretch groups. Conclusions: Data demonstrate that intermittent stretching promotes osteogenic differentiation of BMMSCs, and the p38MAPK-osterix pathway has an important role in the control of osteogenesis-related gene expression.

Intermittent Stretch Reduces Force and Central Drive more than Continuous Stretch

The relative contributions of central versus peripheral factors to the force loss induced by acute continuous and intermittent plantarflexor stretches were studied. Eighteen healthy young men with no apparent tissue stiffness limitations randomly performed 1) one 5-min stretch (continuous stretch [CS]), 2) five 1-min stretches (intermittent stretch [IS]), and 3) a control condition, on three separate days. The stretches were constant-torque ankle stretches performed on an isokinetic dynamometer. Gastrocnemius medialis oxygenation status was quantified during stretch using near-infrared spectroscopy. Measures of isometric plantarflexor peak torque (Tpeak), voluntary activation (%VA; interpolated twitch technique), EMG amplitude normalized by Mmax (EMG:M), V-wave amplitude, and excitation-contraction (E-C) coupling efficiency (torque ratio between 20- and 80-Hz tetanic stimulations [20:80]) were taken before, immediately, and 15 and 30 min after each condition. IS caused substantial cyclic variations in tissue oxygenation, but CS resulted in a greater decrease in oxyhemoglobin concentration. Voluntary Tpeak decreased more after IS (-23.8%) than CS (-14.3%) and remained significantly depressed until 30 min after IS only (-5.6%). EMG:M (-27.7%) and %VA (-15.9%) were reduced only after IS. After CS and IS, the magnitude of decrease in Tpeak was correlated with decreases in EMG:M (r = 0.81 and 0.89, respectively), %VA (r = 0.78 and 0.93), and V-wave (r = 0.51, only after IS). Tetanic torque values (20 and 80 Hz) were decreased after IS (-13.1% and -6.4%, respectively) and CS (-10.9% and -6.7%, respectively), but 20:80 was not different from the control group. These results suggest that IS reduced Tpeak more than CS, and these reductions were strongly associated with a depression in central drive.

THU0567 The Development of a Community Based Education/Self-Management Program for People with Ankylosing Spondylitis

BackgroundWhilst hospital based physiotherapy led education/exercise programs exist for ankylosing spondylitis (AS), there are few community based disease specific self management interventionsObjectivesTo develop a group education and self-management program, for...

Intermittent Traction Stretch Promotes the Osteoblastic Differentiation of Bone Mesenchymal Stem Cells by the ERK1/2-Activated Cbfa1 Pathway

Mechanical stress plays a crucial role in bone formation and absorption. We investigated the osteoblastic differentiation of bone mesenchymal stem cells (BMSCs) affected by intermittent traction stretch at different time points and explored the mechanism of osteoblastic differentiation under this special mechanical stimulation. The BMSCs and C3H10T1/2 cells were subjected to 10% elongation for 1–7 days using a Flexcell Strain Unit, and then the mRNA levels of osteoblastic genes and the expression of core-binding factor a1 (Cbfa1) were examined. Furthermore, we focused specifically on the role of the extracellular signal-regulated kinases 1/2 (ERK1/2) and Cbfa1 in the osteogenesis of BMSCs stimulated by the stretch. The results of these experiments showed that the stretch induces a time-dependent increase in the expression of osteoblastic genes. The synthesis of osteoblastic genes was downregulated after the knockdown of Cbfa1 expression by short-interfering RNA. Furthermore, the stress-induced increase in the expression of Cbfa1 mRNA and osteoblastic genes was inhibited by U0126, an ERK1/2 inhibitor. These results indicate that long periods of intermittent traction stretch promote osteoblastic differentiation of BMSCs through the ERK1/2-activated Cbfa1 signaling pathway.

Phosphatidic Acid and Mechanical Stimuli Activate mTOR Signaling via an ERK‐independent Mechanism

Signaling by mTOR is both necessary and sufficient for the induction of hypertrophy in response to increased mechanical loading. Recently it has been suggested that mechanical stimuli (MS) induce mTOR signaling via a mechanism that is dependent on phosphatidic acid (PA). The mechanism via which PA activates mTOR signaling is not clear, but at least two models have been proposed; 1) direct binding of PA to mTOR, or 2) PA‐induced activation of ERK which then stimulates mTOR. In order to more clearly define the role of ERK in the regulation of mTOR by PA and MS, we first performed experiments in which C2C12 myoblasts were stimulated with exogenous PA. The results indicated that exogenous PA was sufficient to induce signaling through both ERK and mTOR, however, inhibition of ERK with UO126 did not prevent the ability of PA to induce mTOR signaling. Next, we performed experiments in which mouse EDL muscles were subjected to intermittent stretch as a source of MS. The results indicated that MS was sufficient to induce an increase in PA, as well as, signaling through both ERK and mTOR. Similar to the results observed with exogenous PA, inhibiting ERK with UO126 did not prevent the ability of MS to induce mTOR signaling. Taken together, these results indicate that both exogenous PA and MS induce mTOR signaling through an ERK‐independent mechanism that potentially involves a direct interaction of PA with mTOR. Support: NIH grant AR057347 to TAH

Optimizing an Intermittent Stretch Paradigm Using ERK1/2 Phosphorylation Results in Increased Collagen Synthesis in Engineered Ligaments

Dynamic mechanical input is believed to play a critical role in the development of functional musculoskeletal tissues. To study this phenomenon, cyclic uniaxial mechanical stretch was applied to engineered ligaments using a custom-built bioreactor and the effects of different stretch frequency, amplitude, and duration were determined. Stretch acutely increased the phosphorylation of p38 (3.5±0.74-fold), S6K1 (3.9±0.19-fold), and ERK1/2 (2.45±0.32-fold). The phosphorylation of ERK1/2 was dependent on time, rather than on frequency or amplitude, within these constructs. ERK1/2 phosphorylation was similar following stretch at frequencies from 0.1 to 1 Hz and amplitudes from 2.5% to 15%, whereas phosphorylation reached maximal levels at 10 min of stretch and returned toward basal within 60 min of stretch. Following a single 10-min bout of cyclic stretch, the cells remained refractory to a second stretch for up to 6 h. Using the phosphorylation of ERK1/2 as a guide, the optimum stretch paradigm was hypothesized to be 10 min of stretch at 2.5% of resting length repeated every 6 h. Consistent with this hypothesis, 7 days of stretch using this optimized intermittent stretch program increased the collagen content of the grafts more than a continuous stretch program (CTL=3.1%±0.44%; CONT=4.8%±0.30%; and INT=5.9%±0.56%). These results suggest that short infrequent bouts of loading are optimal for improving engineered tendon and ligament physiology.

The Effects of Intermittent Stretching Following a 4-Week Static Stretching Protocol: A Randomized Trial

Stretching is performed in rehabilitation and sports conditioning programs. It is not known how often during a week stretching needs to be performed to maintain flexibility. Therefore, the purpose of this study was to determine the influence of intermittent stretching (i.e., 2-3 days/week) on hip range of motion (ROM) following a 4-week, daily stretching program. This study used a randomized, single-blind, test-retest design. Healthy adult subjects, age 18 to 50 years, were randomly assigned to 1 of 2 static stretching protocols: (a) standard protocol or (b) intermittent protocol. All subjects stretched their hamstrings daily for the first 4 weeks. The standard group discontinued all stretching after 4 weeks. The intermittent group continued to stretch 2 to 3 days per week for an additional 4 weeks. All subjects were measured for hip ROM weekly for the full 8 weeks. Thirty-two subjects completed the study (standard group = 14; intermittent group = 18, mean age 24.6 years). Mean hip ROM increased (p < 0.05) for both groups from before protocol (PRE) to Week 4 (standard group gain from 71.4 +/- 18.5 degrees to 90.6 +/- 20.5 degrees and intermittent group gain from 68.6 +/- 15.7 degrees to 89.1 +/- 16.8 degrees). During the final 4 weeks, mean hip ROM decreased (p < 0.05) for the standard group from 90.6 +/- 20.5 degrees to 83.9 +/- 20.3 degrees. Mean hip ROM for the intermittent group did not decrease during the final 4 weeks of the study (89.1 +/- 16.8 degrees to 93.2 +/- 14.9 degrees, p > 0.05). Intermittent stretching (i.e., 2 or 3 days/week) is sufficient to maintain ROM gains acquired from a prior static stretching program. Clinicians and trainers may educate their clients of the benefits of intermittent stretching to maintain flexibility.

Phosphatidic acid: a novel mechanical mechanism for how resistance exercise activates mTORC1 signalling

Phosphatidic acid: a novel mechanical mechanism for how resistance exercise activates mTORC1 signalling

The Effect of Different Frequencies of Stretch on Human Dermal Keratinocyte Proliferation and Survival

The effects of cyclic stretch on mitogen-activated protein kinase (MAPK) and apoptosis in keratinocytes are not well understood. The aim of this study is to compare the effect of high frequency repetitive (HF) stretch to intermittent (I) stretch on human dermal keratinocytes proliferation and survival. Cultured human dermal keratinocytes were exposed to either repetitive HF or I stretch. Cell number was measured by coulter counter, DNA synthesis was assessed by BrdU staining, and apoptosis was assessed by terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL) staining. The activation of p38 MAPK, ERK 1/2, and AKT was assessed by immunoblotting. p38 MAPK, ERK 1/2, and AKT exhibited no change after HF stretch, while AKT and Homo sapiens BCL-2-antagonist of cell death (BAD) were significantly activated after I stretch. After experiencing I stretch for 2 d, keratinocyte proliferation rates were significantly decreased. This decrease was most likely not due to apoptosis as TUNEL-positive cells only increased for cells treated with an AKT inhibitor.

Effect of different frequencies of tensile strain on human dermal fibroblast proliferation and survival

The aim of this study is to compare the effect of a high-frequency repetitive (HF) stretch or an intermittent (I) stretch on the cell proliferation and survival of human dermal fibroblasts and to determine the activation of any relevant signal pathways. Cultured human dermal fibroblasts were exposed to either HF or I stretch. Cell number was measured by counting, while DNA synthesis was assessed by 5-bromo-2'-deoxyuridine (BrdU) staining and apoptosis by terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling staining. To investigate the potential mechanisms of repetitive strain on the proliferation and survival of fibroblasts, the activation of relevant transduction pathways, such as p38 mitogen-activated protein kinase (MAPK), extracellular signal-regulated kinase (ERK)1/2, AKT, and BAD, was assessed by Western blot. In addition, the effect of inhibition of these pathways on the fibroblast response was also studied. After either HF or I stretch for 7 days, fibroblast number was significantly decreased and there were less BrdU-positive cells. The numbers of apoptotic and/or necrotic fibroblasts were not affected. p38 MAPK and ERK1/2 were significantly activated after HF stretch, but AKT and BAD were significantly activated after I stretch. The inhibitors of p38 MAPK and MAPK/ERK kinase as well as dominant-negative AKT reduced cell number after both HF and I stretch but these pathways were not critical for the stretch-induced decrease in cell number.

The Ecological Effect of Drought on the Macroinvertebrate Fauna of a Small Intermittent Stream – An Example from the Czech Republic

AbstractThe impact of an unstable hydrological regime on macroinvertebrates in an intermittent stream (with periodic summer droughts in particular stretches) was investigated in two successive years with differing climatic conditions. Ten series of macroinvertebrate samples were taken from two sampling sites between April 2002 and October 2003. Total abundance, taxa richness, main faunal groups, and life strategies were assessed in order to describe the changes in the macroinvertebrate assemblages. Periodic dry periods caused a decrease in macroinvertebrate density in the intermittent stretch, whereas they had no negative influence on number of taxa. Before the drought, the density of permanent fauna decreased and the number of r‐strategists rose and stayed at a high level in first samples in the after‐drought period. (© 2007 WILEY‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)

The Effect of Prolonged Versus Intermittent Stretch on Disuse Atrophy of Immobilized Rat Muscles

The Effect of Prolonged Versus Intermittent Stretch on Disuse Atrophy of Immobilized Rat Muscles

Decreased capillarization and a shift to fast myosin heavy chain IIx in the biceps brachii muscle from young adults with spastic paresis

Muscle spasticity and paresis are conditions that occur secondary to upper motor neuron lesions. The co-existence of decreased motor unit recruitment and intermittent over-activity generates confusion concerning the effect on muscle fiber characteristics. In order to increase the knowledge about the effect of upper motor lesion on capillarization and muscle fiber composition, the biceps brachii muscle from seven young adults with long duration of spastic paresis and seven age-matched controls were analyzed using morphological and enzyme- and immuno-histochemical techniques. The spastic muscles had a 38% lower capillary density ( p = 0.002), 30% fewer capillaries around each muscle fiber ( p = 0.02), and 16% fewer capillaries when related to the fiber size ( p = 0.04). The frequency of fibers expressing myosin heavy chain (MyHC) IIx increased (30% vs. 4%, p = 0.006), while the percentage of fibers expressing MyHC I and MyHC IIa, respectively, decreased (22% vs. 46% and 7% vs. 29%, p < 0.01). The high proportion of muscle fibers with low oxidative capacity and low capillary supply indicates that biceps brachii muscle from patients with upper motor lesions fatigue more easily than normal controls. We also observed a significantly higher variability in fiber size for fibers expressing MyHC I ( p < 0.04), and, in three of the subjects, a small amount of small fibers expressing developmental MyHCs was found. These results suggest that, although intermittent stretch reflex contractions might have an impact on the muscle characteristics in spastic paresis, the muscle phenotypic properties are more adapted to decreased voluntary motor unit recruitment.

Cyclic mechanical stretch inhibits cell proliferation and induces apoptosis in fetal rat lung fibroblasts.

Development of the pulmonary air sacs is crucial for extrauterine survival. Late fetal lung development is characterized by a thinning of the mesenchyme, which brings pneumocytes and endothelial cells into apposition. We hypothesized that mechanical stretch, simulating fetal breathing movements, plays an important role in this remodeling process. Using a Flexercell Strain Unit, we analyzed the effects of intermittent stretch on cell proliferation and apoptosis activation in fibroblasts isolated from fetal rat lungs during late development. On day 19, intermittent stretch increased cells in G(0)/G(1) by 22% (P = 0.001) and decreased in S phase by 50% (P = 0.003) compared with unstretched controls. Cell proliferation analyzed by 5-bromo-2'-deoxyuridine incorporation showed a similar magnitude of cell cycle arrest (P = 0.04). At this same gestational age, stretch induced apoptosis by two- to threefold over controls, assayed by DNA flow cytometry, terminal deoxynucleotidyl transferase-mediated dUTP-FITC nick-end labeling, and caspase-3 activation. These results indicate that mechanical stretch of fibroblasts isolated during the canalicular stage inhibits cell cycle progression and activates apoptosis. These findings are cotemporal with the mesenchymal thinning that normally occurs in situ.