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Muscle stretching - The potential role of endogenous pain inhibitory modulation on stretch tolerance
Scandinavian Journal of Pain
Abstract
Background and aims. The effect of stretching on joint range of motion is well documented and is primarily related to changes in the tolerance to stretch, but the mechanisms underlying this change are still largely unknown. The aim of this study was to investigate the influence of a remote, painful stimulus on stretch tolerance.
Methods. Thirty-four healthy male subjects were recruited and randomly assigned to an experimental pain group (N = 17) or a control group (N = 17). Passive knee extension range of motion, the activity of hamstring muscles and passive resistive torque were measured with subjects in a seated position. Three consecutive measures were performed with a five-minute interval between. A static stretch protocol was utilized in both groups to examine the effect of stretching and differences in stretch tolerance between groups. Following this, the pain-group performed a cold pressor test which is known to engage the endogenous pain inhibitory system after which measurements were repeated.
Results. A significant increase in knee extension range of motion was found in the pain group compared with controls (ANCOVA: P < 0.05). No difference was found in muscle activity or passive resistive torque between groups (ANCOVA P > 0.091).
Conclusions. Passive knee extension range of motion following stretching increased when following a distant, painful stimulus, potentially engaging the endogenous pain inhibitory systems. Current findings indicate a link between increased tolerance to stretch and endogenous pain inhibition.
Implications. The current findings may have implications for clinical practice as they indicate that a distant painful stimulus can influence range of motion in healthy individuals. This implies that the modulation of pain has significance for the efficacy of stretching which is important knowledge when prescribing stretching as part of rehabilitation.
... Stretch tolerance is defined as the capability to tolerate stretchrelated discomfort [13]. Previous research indicates that changes in the range of motion following stretching may be a manifestation of altered pain sensitivity [14,15], suggesting that the tolerance to stretching may be a marker of overall pain sensitivity [16]. The increase in stretch tolerance may be contingent on an analgesic effect, allowing for a higher tolerance to passive tension [14,17]. ...
... Previous research indicates that changes in the range of motion following stretching may be a manifestation of altered pain sensitivity [14,15], suggesting that the tolerance to stretching may be a marker of overall pain sensitivity [16]. The increase in stretch tolerance may be contingent on an analgesic effect, allowing for a higher tolerance to passive tension [14,17]. There may also be a decrease in both regional (e.g., local) and distant (e.g., a remote site of the body) pain sensitivity following acute bouts of stretching in healthy adults [18]. ...
... Mechanisms such as the modulation of inputs in the spinal dorsal horns (i.e., the Gate Control Theory) [7] and endogenous pain inhibitory mechanisms [16] have been proposed to be related to the effect of stretching on pain. Previous studies have also found correlations between the relative changes in the range of motion and the relative changes in pressure pain thresholds following stretching [12,14,18]. However, the magnitude of altered pain sensitivity responses following regular stretching is unknown. ...
Background
Stretching exercises are widely used for pain relief and show positive effects on musculoskeletal, nociplastic and neuropathic pain; the magnitude of altered pain sensitivity responses following regular stretching is currently unknown. This study aimed to investigate the effect of six weeks of regular stretching exercise on regional and widespread pain sensitivity and range of motion and the effect of stretching cessation on regional and widespread pain sensitivity and range of motion.
Methods
An experimental single-blind longitudinal repeated measures study. Twenty-six healthy adults were recruited. Regional and distant pressure pain thresholds and passive knee extension range of motion were measured at three points: before (baseline) and after six weeks (post-stretch) of daily bilateral hamstring stretching exercises and following four weeks of cessation (post-cessation) from stretching exercises.
Results
Participants had a mean ± standard deviation (range) age of 23.8 ± 2.1 (21–30) years. There was a 36.7% increase in regional (p = 0.003), an 18.7% increase in distant pressure pain thresholds (p = 0.042) and a 3.6% increase in range of motion (p = 0.002) between baseline and post-stretch measures. No statistically significant differences were found for regional (p = 1.000) or distant pressure pain thresholds (p = 1.000), or range of motion (p = 1.000) between post-stretch and post-cessation. A 41.2% increase in distant pressure pain thresholds (p = 0.001), a 15.4% increase in regional pressure pain thresholds from baseline to post-cessation (p = 0.127) and a 3.6% increase in passive knee extension range of motion (p = 0.005) were found from baseline to post-cessation.
Conclusions
Six weeks of regular stretching exercises significantly decreased regional and widespread pain sensitivity. Moreover, the results showed that the hypoalgesic effect of stretching on regional and widespread pain sensitivity persisted following four weeks of cessation. The results further support the rationale of adding stretching exercises to rehabilitation efforts for patients experiencing nociceptive, nociplastic, and neuropathic pain. However, further research is needed to investigate how the long-term effects of stretching exercises compare with no treatment in clinical populations.
Trial registration
The trial was registered June 1st, 2021 at ClinicalTrials.gov (Trial registration number NCT04919681).
... Para um bom desempenho das atividades ocupacionais, desportivas e até mesmo das atividades de vida diária é fundamental que a mobilidade dos tecidos moles, assim como das articulações, esteja íntegra. [1][2][3][4][5] Definida como a capacidade do músculo de alongar-se 4,6 e permitir que a articulação se movimente ao longo de sua amplitude de movimento (ADM) de forma irrestrita e não álgica, 7 a flexibilidade muscular exerce influência sobre a mobilidade e funcionalidade articular, 1 além de ser importante para a aptidão física e para o desempenho muscular. 4,6 Empregado como exercício para ganho e manutenção de flexibilidade 4,6,8 o alongamento é adotado por muitos profissionais em programas de recuperação e prevenção de lesões, bem como para promoção de saúde, uma vez que, entre seus benefícios encontra-se o aumento da extensibilidade dos tecidos moles, a diminuição do tônus e do encurtamento muscular e a promoção da amplitude de movimento articular. ...
... 1,2,9 Esses resultados favoráveis obtidos pelo alongamento estão, frequentemente, relacionados às alterações na unidade músculo-tendínea (UMT) e em componentes neuromusculares. 5 Outras técnicas do acervo fisioterapêutico podem ser aplicadas em associação ao alongamento no intuito de fomentar seus efeitos sobre o ganho de flexibilidade, entre tais recursos destacam-se os agentes térmicos, calor e frio. Tanto a aplicação -aquecimento -como a retirada -resfriamento -do calor superficial dos tecidos, agregam resultados e podem ser utilizados para fins terapêuticos. ...
... 1,2,7,10 Em razão da propriedade do frio que diminui a velocidade de condução nervosa, o seu uso prévio ao alongamento não é seguro, pois o paciente perde o feedback sensitivo do procedimento (alongamento), ficando sujeito a lesões musculares por excesso de alongamento (estiramento/distensão muscular). [2][3][4][5]10 Portanto, posto que o calor aumenta a flexibilidade, porém seus ganhos não são mantidos e, o frio possui capacidade de aumentar a rigidez tecidual e proporcionar mudança na conformação estrutural e manutenção das alterações, 1-10 hipotetiza-se que o uso do calor prévio ao alongamento e do frio posterior ao mesmo, possibilitaria uma maior eficácia das manobras para ganho de flexibilidade, hipótese ainda não testada na literatura. Sugere-se que a associação entre agentes térmicos e alongamento pode acrescer o ganho de flexibilidade. ...
Objetivo: Investigar os efeitos da associação entre alongamento e recursos termoterapêuticos sobre o ganho de flexibilidade e amplitude de movimento. Métodos: Este ensaio clínico, controlado, não randomizado e cego teve duração de três semanas, com duas sessões semanais e incluiu 27 indivíduos do sexo feminino, as quais compuseram tanto o grupo experimental quanto o controle, de forma que um de seus membros inferiores recebeu a intervenção terapêutica dos recursos termoterapêuticos e o membro oposto foi submetido apenas ao alongamento. A análise angular foi realizada através do software de avaliação postural Kinovera. Resultados: Os efeitos do alongamento associado ao calor prévio e resfriamento pós intervenção se mostraram mais eficazes comparado ao grupo controle pré-intervenção (p<0,000), grupo controle pós intervenção (p= 0,003) e grupo experimental pré-intervenção (p<0,000). Conclusão: A aplicação de calor prévio ao alongamento, seguido pelo emprego imediato de resfriamento propicia ganhos de flexibilidade muscular e amplitude de movimento maiores que o alongamento simples.
... Stretch tolerance is commonly characterized by the changes in range of motion and peak passive moment recorded at end range [8] and is defined as the ability to tolerate stretch-related discomfort [9] suggesting that an increase in stretch tolerance may explain improved joint range of motion following stretching [10]. An increase in stretch tolerance following stretching may depend on an analgesic effect, allowing for higher tolerance to passive tension [11,12], possibly due to changes in the sensitivity of peripheral nociceptors in the joint or muscle-tendon unit (e.g. type Ia and Ib afferents) via gate control [9,10] or neurotransmitter modulation [13]. ...
... Recent findings from our group suggest that there may be a link between the tolerance to stretch and endogenous inhibitory pain mechanisms indicating that central pain mechanisms can to some extent modulate joint range of motion following stretching [12]. However, it is still unknown to what extent pain affects the tolerance to stretch. ...
... The participants had a mean ± standard deviation (range) age, 25.5 ± 3.5 [22][23][24][25][26][27][28][29][30][31][32][33][34] [21]. In accordance with IKDC criteria, the sample size was determined to detect a difference in knee extension range of motion of at least 2°, as this must be distinguished to properly categorize knee function [13], (α=0:05, power=80%) between measures [12]. Based on these data, an n value of 16 participants was estimated to be necessary. ...
Objectives
The effect of stretching on joint range of motion is well documented, and although sensory perception has significance for changes in the tolerance to stretch following stretching the underlining mechanisms responsible for these changes is insufficiently understood. The aim of this study was to examine the influence of endogenous pain inhibitory mechanisms on stretch tolerance and to investigate the relationship between range of motion and changes in pain sensitivity.
Methods
Nineteen healthy males participated in this randomized, repeated-measures crossover study, conducted on 2 separate days. Knee extension range of motion, passive resistive torque, and pressure pain thresholds were recorded before, after, and 10 min after each of four experimental conditions; (i) Exercise-induced hypoalgesia, (ii) two bouts of static stretching, (iii) resting, and (iv) a remote, painful stimulus induced by the cold pressor test.
Results
Exercise-induced hypoalgesia and cold pressor test caused an increase in range of motion (p<0.034) and pressure pain thresholds (p<0.027). Moderate correlations in pressure pain thresholds were found between exercise-induced hypoalgesia and static stretch (Rho>0.507, p=0.01) and exercise-induced hypoalgesia and the cold pressor test (Rho=0.562, p=0.01). A weak correlation in pressure pain thresholds and changes in range of motion were found following the cold pressor test (Rho=0.460, p=0.047). However, a potential carryover hypoalgesic effect may have affected the results of the static stretch.
Conclusions
These results suggest that stretch tolerance may be linked with endogenous modulation of pain. Present results suggest, that stretch tolerance may merely be a marker for pain sensitivity which may have clinical significance given that stretching is often prescribed in the rehabilitation of different musculoskeletal pain conditions where reduced endogenous pain inhibition is frequently seen.
... As the non-local or contralateral limb is not physically stretched in these scenarios, it is postulated that the increase in ROM cannot be attributed to morphological mechanisms such as increased musculotendinous unit compliance [16,18,19,23]. Increased stretch tolerance is a commonly suggested mechanism underlying an increase in ROM of the stretched limb [5,6,[24][25][26] as well as with non-stretched contralateral and non-local muscles and joints [16,18,19,[21][22][23]27]. ...
... Increased stretch (pain) tolerance has been widely attributed as a primary mechanism underlying stretched and non-stretched joint ROM increases [16,18,19,24,26,[37][38][39][40]. Increased stretch tolerance effects to increase contralateral ROM have been attributed to diffuse noxious inhibitory control and gate control theory of pain due to stimulation of nociceptors from the SS which may suppress the sensation of pain [16,18,41,42]. ...
Introduction: Increases in contralateral range of motion (ROM) have been shown following acute high-intensity and high-duration static stretching (SS) with no significant change in contralateral force, power, and muscle activation. There are currently no studies comparing the effects of a high-intensity, short-duration (HISD) or low-intensity, long-duration (LILD) SS on contralateral performance. Purpose: The aim of this study was to examine how HISD and LILD SS of the dominant leg hamstrings influence contralateral limb performance. Methods: Sixteen trained participants (eight females, eight males) completed three SS interventions of the dominant leg hamstrings; (1) HISD (6 × 10 s at maximal point of discomfort), (2) LILD (6 × 30 s at initial point of discomfort), and (3) control. Dominant and non-dominant ROM, maximal voluntary isometric contraction (MVIC) forces, muscle activation (electromyography (EMG)), and unilateral CMJ and DJ heights were recorded pre-test and 1 min post-test. Results: There were no significant contralateral ROM or performance changes. Following the HISD condition, the post-test ROM for the stretched leg (110.6 ± 12.6°) exceeded the pre-test (106.0 ± 9.0°) by a small magnitude effect of 4.2% (p = 0.008, d = 0.42). With LILD, the stretched leg post-test (112.2 ± 16.5°) exceeded (2.6%, p = 0.06, d = 0.18) the pre-test ROM (109.3 ± 16.2°) by a non-significant, trivial magnitude. There were large magnitude impairments, evidenced by main effects for testing time for force, instantaneous strength, and associated EMG. A significant ROM interaction (p = 0.02) showed that with LILD, the stretched leg significantly (p = 0.05) exceeded the contralateral leg by 13.4% post-test. Conclusions: The results showing no significant increase in contralateral ROM with either HISD or LILD SS, suggesting the interventions may not have been effective in promoting crossover effects.
... Tolerance to the stretch sensation may be associated with an endogenous descending inhibitory response that improves muscle extensibility [19,20]. Greater tolerance to the stretch sensation is related to improvements in muscle extensibility rather than passive stiffness [21]. ...
... The prior literature demonstrates that range of motion increases after introducing a painful stimuli, such as a cold pressor test or stretching to the point of pain [19,20]. In a cross-over study of nineteen healthy male participants, participants underwent pre/post assessment of the PPT (quadriceps, biceps, deltoid) in response to two repetitions of a thirty second static stretching intervention of the knee flexors or two minutes of cold water immersion (conditioned pain modulation) [19]. ...
Myofascial stretching is often prescribed in the management of musculoskeletal pain. However, the neural mechanisms contributing to a decrease in pain are unknown. Stretching produces a sensation that may act as a conditioning stimulus in a conditioned pain modulation response. The purpose of this study was to compare immediate changes in pressure pain thresholds (PPTs) during a low-intensity stretch, moderate-intensity stretch, and cold water immersion task. A secondary purpose was to examine if personal pain sensitivity and psychological characteristics were associated with the responses to these interventions. Twenty-seven (27) healthy participants underwent a cross-over study design in which they completed a cold water immersion task, upper trapezius stretch to the onset of the stretch sensation, and a moderate-intensity stretch. A significant condition x time effect was observed (F (8,160) = 2.85, p < 0.01, partial eta2 = 0.13), indicating reductions in pain sensitivity were significantly greater during a cold water immersion task compared to moderate-intensity stretching at minutes two and four. Widespread increases in heat pain threshold and lower pain-related anxiety were moderately correlated with the response to the cold water immersion task but not stretching. Moderate-intensity stretching may not elicit a conditioned pain modulation response possibly because the stretch was not intense enough to be perceived as painful.
... These results suggest that the routine SS intervention program using high-intensity stretching could change stretch tolerance rather than muscle architecture and muscle stiffness in the contralateral side, which would increase DF ROM in the contralateral side. A previous study suggested that endogenous pain inhibition is associated with changes in stretch tolerance during stretching intervention (Støve et al., 2019). Furthermore, the painful stimulus could increase ROM in non-local joints (Støve et al., 2019). ...
... A previous study suggested that endogenous pain inhibition is associated with changes in stretch tolerance during stretching intervention (Støve et al., 2019). Furthermore, the painful stimulus could increase ROM in non-local joints (Støve et al., 2019). It is thought that painful stimulus is essential for the non-local effect, including the cross-education effect. ...
Purpose: This study aimed to compare the cross-education effect of unilateral stretching intervention programs with two different intensities (high- vs. normal-intensity) on dorsiflexion range of motion (DF ROM), muscle stiffness, and muscle architecture following a 4-week stretching intervention.
Methods: Twenty-eight healthy males were randomly allocated into two groups: a high-intensity static stretching (HI-SS) intervention group (n=14; stretch intensity 6-7 out of 10) and a normal-intensity static stretching (NI-SS) intervention group (n=14; stretch intensity 0-1 out of 10). The participants were asked to stretch their dominant leg (prefer to kick a ball) for 4 weeks (3 x week for 3 x 60s). Before and after the intervention, the non-trained leg passive properties (DF ROM, passive torque, and muscle stiffness) of the plantar flexors and the muscle architecture of the gastrocnemius medialis (muscle thickness, pennation angle, and fascicle length) were measured.
Results: DF ROM and passive torque at DF ROM were significantly increased in the HI-SS group (50.6% and 18.2%, respectively), but not in the NI-SS group. Moreover, there were no further significant changes in both groups.
Conclusion: For rehabilitation settings, a high-intensity SS intervention is required to increase the DF ROM of the non-trained limb. However, the increases in DF ROM seem to be related to changes in stretch tolerance and not to changes in muscle architecture or muscle stiffness.
... However, few have addressed the stretching effect from a pain perspective. Emerging evidence suggests that biomechanical changes may be explained by an increase in stretch tolerance, potentially mediated by reduced pain sensitivity [14,15]. Peripheral and central mechanisms involved in pain modulation may play an important role in increase stretch tolerance. ...
... Bishop & George (2017) observed that the increase in range of motion following stretching were largely due to an increase in stretch tolerance (i.e. the ability to tolerate the discomfort) [14]. This would imply that the ability to increase range may be more related to a reduction in pain sensitivity as opposed to architectural muscle-tendon changes [15]. ...
Objectives
Stretching is an intervention often used in various kinds of rehabilitation protocols and the effects on pain sensitivity has sparsely been investigated, especially when addressing potential effects on pain. The objective is to investigate the immediate effects of an axial and peripheral prolonged stretch on pressure pain sensitivity (PPT) and temporal summation (TS) on local and distal sites in healthy subjects.
Methods
Twenty-two healthy volunteers were recruited to participate in this pilot study. Two prolonged stretching protocols were performed: low back and wrist extensors stretches. PPT and pinprick TS were measured pre- and post-intervention at local and remote sites. Repeated measures analysis of variance (ANOVA) was used to examine the effects and significance of the interventions.
Results
The low back stretch induced an increase in PPT for both local and remote sites, and the wrist stretch produced a PPT increase only at the local site. TS did not change.
Conclusions
Low back stretching induced an increase in PPT at both local and remote sites whereas the wrist stretch only increased PPT locally, suggesting hypoalgesia at these sites. Further studies are needed to confirm the effect and mechanisms using randomised, controlled and parallel study design. Considering that pain sensitivity is different than clinical pain, results are difficult to extrapolate to clinical practice. Future studies testing clinical pain are needed to better understand the clinical implication of these results.
... The present findings support this rationale, which has been discussed in previous literature (4,40,43). It should be noted that a modification in stretch tolerance has also been suggested as a potential mechanism for increasing maximal ROM following chronic stretching and cannot be totally excluded from our findings (6,21,54,59). Because several studies have reported improvements in variables such as range of motion in the absence of mechanical adaptations at the joint level, chronic changes associated with long-term stretching have most often been explained by an alteration of sensation, which is referred to as the "sensory" theory in the literature (21,59). ...
... There were no statistical significant group effects on maximal dorsiflexion ROM at the same ankle torque for the HIP-flexion condition [F(2,54) ϭ 18.9, P ϭ 0.649, p 2 ϭ 0.016].Muscle shear wave velocity. There was a significant main effect of group in triceps surae shear wave velocity for all assessed muscle locations with moderate to large effects sizes: GM proximal [F(2,54) ϭ 5.9, P ϭ 0.005, p 2 ϭ 0.18], GM intermediate [F(2,54) ϭ 12.4, P Ͻ 0.001, p 2 ϭ 0.32], GM distal [F(2,54) ϭ 7, P ϭ 0.002, p 2 ϭ 0.21], GL proximal [F(2,54) ϭ 9.3, P Ͻ 0.001, p 2 ϭ 0.26], GL intermediate [F(2,54) ϭ 3.9, P ϭ 0.026, p 2 ϭ 0.13], GL distal [F(2,54) ϭ 6.3, P ϭ 0.003, p 2 ϭ 0.19], soleus proximal [F(2,54) ϭ 5.9, P ϭ 0.005, p 2 ϭ 0.18], and soleus distal [F(2,54) ϭ 3.5, P ϭ 0.036, p 2 ϭ 0.12]. ...
Tissue-directed stretching interventions can preferentially load muscular or non-muscular structures such as peripheral nerves. How these tissues adapt mechanically to long-term stretching is poorly understood. This randomized, single-blind, controlled study used ultrasonography and dynamometry to compare the effects of 12-week nerve-directed and muscle-directed stretching programs versus control on: maximal ankle dorsiflexion range of motion (ROM) and passive torque, shear wave velocity (SWV; an index of stiffness) and architecture of triceps surae and sciatic nerve. Sixty healthy adults were randomized to receive nerve-directed, muscle-directed stretching, or no intervention (control). The muscle-directed protocol was designed to primarily stretch the plantar flexor muscle group, while the nerve-directed intervention targeted the sciatic nerve tract. Compared with the control group (mean; 95% Confidence Interval), muscle-directed intervention showed increased ROM (+7.3°; 95% CI: 4.1-10.5), decreased SWV of triceps surae (varied from -0.8 to -2.3m/s across muscles), decreased passive torque (-6.8N.m; 95% CI: -11.9 to -1.7), and greater gastrocnemius medialis fascicle length (+0.4cm; 95% CI: 0.1 to 0.8). Muscle-directed intervention did not affect the SWV and size of sciatic nerve. Participants in nerve-directed group showed a significant increase in ROM (+9.9°; 95% CI: 6.2 to 13.6) and a significant decrease in sciatic nerve SWV (> -1.8m/s across nerve regions) compared with the control group. Nerve-directed intervention had no effect on the main outcomes at muscle and joint levels. These findings provide new insights into the long-term mechanical effects of stretching interventions, and have relevance to clinical conditions where change in mechanical properties has occurred.
... It was previously assumed that the increase in muscle extensibility achieved through stretching was attributed to an increase in muscle length. However, numerous studies suggest that this increase may primarily result from changes in the individual's perception 2 of 12 during stretching [8][9][10][11]. These changes may depend on the neural tension parameters applied during stretching. ...
(1) Background: Stretching has been shown to improve flexibility, muscle activation, and coordination, but its effects may depend on neural tension during the stretch. This study evaluated the short- and medium-term effects of hamstring stretching with and without neural load on flexibility, tibial nerve pressure pain threshold, and maximum isometric strength. (2) Methods: Seventy-eight healthy participants (mean age: 24.96 ± 6.11 years) were randomly assigned to stretching programs with (n = 39) or without neural load (n = 39). Flexibility, pressure pain threshold, and maximum isometric strength were assessed at baseline, after the first session, at the end of the intervention, and one month later. (3) Results: The group using neural load showed significant flexibility improvements after the first session (MD = −5.2; p < 0.001), which were maintained at two months (MD = −8.6; p < 0.001) and follow-up (MD = −6.4; p < 0.001). In the control group, flexibility gains diminished at follow-up (MD = −3.9; p = 0.052). Other variables showed no significant changes across time points. (4) Conclusions: Since neither treatment showed superior efficacy, no specific stretching type could be recommended.
... Music-induced relaxation has been shown to be an important tool for alleviation of musculoskeletal pain, increased exercise motivation, and decreased muscle tension in medical rehabilitation settings [14][15][16]. It may thus be expected to decrease muscle stiffness by also decreasing pain [4] or increasing pain tolerance, allowing a person to tolerate a greater muscle stretch [17][18][19][20]. Van Criekinge et al. [16] recently summarized the effects of music on arousal state, cognitive function, and attention, and such information might be used to develop acute music interventions. ...
Studies investigating the mechanisms influencing maximum passive joint range of motion (ROMmax) and stiffness have not objectively assessed the possible influence of stretch speed and/or arousal state. The purpose of this study was to assess the effects of arousal state and stretch speed on healthy individuals ROMmax, stiffness, gastrocnemius medialis, and soleus electromyographic activity (EMG). Fourteen participants performed one familiarization and then one testing session on separate days in the laboratory. In the familiarization (Session 1), participants practiced fast (30°/s ankle dorsiflexion) and slow (5°/s) plantar flexor stretches on an isokinetic dynamometer with the knee extended. In the experimental session (Session 2), they performed two slow, then two fast, stretches under three randomized arousal conditions: control (no music), arousing, and relaxing music. Dorsiflexion ROMmax, ankle joint stiffness, muscle activity during stretch, mean heart rate, and perception of arousal were measured. Perception of arousal was greater in the arousing than relaxing condition (p = 0.001). ROMmax was greater during fast (69.1° ± 7.8°) than slow stretches (64.9° ± 10.8°; p = 0.002) with no effect of arousal. Stiffness and EMG were higher at faster speeds, with a significantly greater percentage of stiffness observed in the arousing than the other conditions during faster stretches (p = 0.04). ROMmax was greater at the faster stretch speed despite greater stiffness and muscle activities being produced during the stretch. Thus, despite reflexive muscle activity and viscosity being higher during faster stretches, a greater, not lesser, ROMmax was observed. Arousal state, at least when altered by music, did not seem to affect ROMmax but somewhat influenced stiffness in the faster stretches.
... Because passive torque at DF ROM is defined as an indicator of stretch tolerance [1,5], the results of this study support these findings. In a previous study examining the mechanism of stretch tolerance [34,35], knee extension ROM increased in a condition in which the dominant hand performed submaximal isometric handgrip exercises at 25% of maximum voluntary contraction for 3 min and in a condition in which the nondominant hand was immersed up to the wrist in a circulating water bath at 1 °C-4 °C for 2 min, which suggests that exercise-induced hypoalgesia and the endogenous pain suppression system by conditioned pain modulation with cold stimulation were associated with increased stretch tolerance. In addition, Mizuno et al. reported that cathodal transcranial direct current stimulation, which decreases cortical excitability, stimulated the Cz corresponding to the sensorimotor foot area and increased ankle DF ROM without changing mechanical properties [36]. ...
Context
Joint position sense may be related to increased range of motion (ROM) with static stretching (SS).
Purpose
The purpose of this study was to examine the relationship between the increased ROM and stretch tolerance, passive stiffness, and joint position sense in the acute effects of SS, including cross-education and non-local effects.
Methods
Eighteen healthy, young males were randomized to three SS intervention conditions [(1) ipsilateral, (2) contralateral, (3) hamstring stretching], and one (4) control condition. The SS intervention was performed on the dominant side in the ipsilateral condition, the non-dominant side in the contralateral condition, and on the hamstrings of the dominant side in the hamstring condition. SS was performed at three 60-s stretching interventions with a 30-s interval. In the control condition, participants sat on the chair for 240 s. The ankle dorsiflexion (DF) ROM, passive torque at DF ROM, passive stiffness, and joint position sense of the dominant side were measured pre and post-intervention the SS intervention. We performed pre and post-intervention comparisons and a correlation analysis using changes.
Results
Significant positive correlations were noted between the change DF ROM and change passive torque at DF ROM in the ipsilateral (p < 0.001, r = 0.805), contralateral (p < 0.001, r = 0.814), and hamstring (p < 0.01, rs = 0.874) conditions. No significant correlation was found between changes DF ROM and changes passive stiffness and joint position sense in all conditions.
Conclusion
Increases in ROM due to acute effects of SS are not related to changes in joint position sense.
... Another possible explanation may arise from the investigations of Warneke et al. [15,16] indicating improvements in ROM following several warm-up strategies including sham-rolling but also interventions different than FR, which would indicate that a possible warm-up effect rather than a modification of pain sensitivity could be an additional factor contributing to improving ROM following FR. Variations in PPT were not observed in the muscles of the thigh, suggesting, especially for SS, in which a variation in the PF was present, that pain perception was modulated locally rather than as a modulation of the endogenous pain inhibitory system [46]. ...
Background
This study aimed to compare and examine the local and non-local effects of a foam rolling (FR) and static stretching (SS) intervention applied to the plantar flexor (PF).
Methods
Fourteen female participants were investigated. Each participant underwent three conditions in a random order at least 48h apart and at the same time of the day: Control (CC), SS, and FR. Each condition was performed unilaterally in the dominant PF for 4 sets (apart from CC). SS was performed for 30 s. The FR included 30 rolls (15 in each direction) over a period of 30 s. A rest of 30 s was provided between each set for all conditions. Outcome variables were ankle dorsiflexion range of movement (ROM), tissue hardness, localized bioimpedance analysis at 50 kHz (L-BIA), and pain pressure thresholds (PPT). Tissue hardness, L-BIA, and PPT were measured in the lower leg and thigh. Measures were assessed pre (T0), immediately post (T1), and 10-min after (T2) the intervention.
Results
No differences were found for time for the CC or between the T0 of each condition. Concerning the lower leg, ROM improved for SS and FR from T0 to T1 while returning to baseline in T2. A significant increase in PPT was observed only for SS in T1. L-BIA showed a significant increase for both phase angle and impedance only for FR in T1. Tissue hardness did not change for any group at any time-point. Concerning the thigh, no measure at any time point showed significant differences.
Conclusion
Both, FR and SS were able to acutely improve ankle ROM. The observed changes were probably caused by a change in viscoelastic properties and local pain perception, without any variation in tissue morphology. FR was the only intervention to improve the intracellular-to-extracellular ratio and decrease fluids. Non-local effects were not observed.
... Also recruiting endogenous mechanisms of pain inhibition or facilitation modulate a®erent stimuli of the nervous system resulting in increased pain tolerance. 29 Study had not found any signi¯cant reduction of pain with addition of oculomotor exercises. It has been seen that increased pronociceptive and impaired antinociceptive mechanism occur in non-speci¯c chronic neck pain. ...
Background: Neck pain is a common musculoskeletal disorder, the most common type being non-specific chronic neck pain. It usually involves postural or mechanical causes. In Individuals with neck pain, a notable prevalence of visual complaints has been predominantly reported. It can be linked to the mismatch in the cervical afferent output.
Objective: This study aimed to assess the effect of oculomotor exercises on neck pain, neck disability, gaze stability and visual complaints among individuals with non-specific chronic neck pain and associated visual complaints.
Methods: A total of 32 individuals with non-specific chronic neck pain and associated visual complaints were equally randomised into two groups. To receive either: stretching to the sternocleidomastoid and anterior scalene along with neck Isometric exercises (Group A, conventional) or the conventional protocol along with oculomotor exercises (Group B, experimental). The protocol was given for three alternate days a week for three weeks, a total of nine sessions. The outcome measures were the Visual Analogue Scale (VAS) for pain, Neck Disability Index (NDI) for disability, Dynamic Visual Acuity (DVA) test for gaze stability and Visual Complaints Index (VCI) for visual complaints.
Results: Significant results were seen for the DVA ([Formula: see text]) and VCI ([Formula: see text]), suggesting improvements in gaze stability and visual complaints using oculomotor exercises.
Conclusion: From this study, we highlighted that oculomotor exercises along with conventional treatment led to improvement in visual complaints and gaze stability in patients with non-specific chronic neck pain and associated visual complaints.
... 6,7 Literature shows that stretching is not effective in reducing the occurrence of injury and increasing hamstring muscle length. 8 Cold and hot packs have been shown to affect the contractile properties of muscles. In a study, it has been reported that during isometric contraction of the gastrocnemius muscle, the connection between estimated muscle force and elongation of each structure (tendon-aponeurosis complex, tendon) remained unchanged in both hot and cold immersions. ...
BACKGROUND: Prolonged sitting and a sedentary lifestyle may result in hamstring shortness. A decline in regular physical activity could lead to a decrease in the flexibility of the muscle in a younger adult. Increasing hamstring muscle flexibility could decrease the possibility of injuries and prevent low back pain. The application of high-intensity laser therapy (HILT) has proved to be innumerable benefits for many conditions. However, to date, no published research is available on the effectiveness of this therapy in improving hamstring muscle length in healthy young adults. This article describes the study protocol for investigating the benefits of HILT in treating hamstring muscle tightness among young adults. METHODS: 136 healthy young individuals will be recruited, by purposive sampling method, to participate in a randomized, single-blinded, sham-controlled study. Recruited participants will be randomly divided into two groups, the active HILT group, and the sham HILT group. The treatment duration will be 8-10 minutes per session, on both lower limbs, for alternate days a week, for two weeks. The active knee extension test and sit-toe and touch test are the outcome measures that will be recorded at baseline, end of the 2-week post-intervention period. The p-value ≤0.05 will be considered statistically significant. DISCUSSION: The study findings will provide the data to determine whether HILT would be a future non-pharmacological non-invasive intervention to reduce hamstring muscle tightness among young adults. Trial Registry: Clinical Trials Registry (NCT05077761).
... However, these alterations could be counteracted by performing stretching exercises [14,15]. Battaglia et al. [16] showed that elderly women who performed 8 weeks of training flexibility increased their spinal ROM; specifically, the sacral/hip joint ROM improved by 34 percent. ...
Flexibility training is a fundamental biological process that improves the quality of life of the elderly by improving the ranges of motion of joints, postural balance and locomotion, and thus reducing the risk of falling. Two different training programs were assessed acutely and after 12 weeks by means of the sit-and-reach test. Thirty-one healthy older adults were randomly divided into three groups: the Experiment I group (Exp) performed strength and static stretching exercises; the Experiment II group performed dynamic and static stretching exercises; and participants assigned to the control group maintained a sedentary lifestyle for the entire period of the study. Flexibility acutely increased in Exp I by the first (ΔT0 = 7.63 ± 1.26%; ES = 0.36; p = 0.002) and second testing sessions (ΔT1 = 3.74 ± 0.91%; ES = 0.20; p = 0.002). Similarly, it increased in Exp II significantly by the first (ΔT0 = 14.21 ± 3.42%; ES = 0.20; p = 0.011) and second testing sessions (ΔT1 = 9.63 ± 4.29%; ES = 0.13; p = 0.005). Flexibility significantly increased over the 12 weeks of training in Exp I (ΔT0 − T1 = 9.03 ± 3.14%; ES = 0.41; p = 0.020) and Exp II (ΔT0 − T1 = 22.96 ± 9.87%; ES = 0.35; p = 0.005). The acute and chronic differences between the two groups were not significant (p > 0.05). These results suggest the effectiveness of different exercise typologies in improving the flexibility of the posterior muscular chains in older adults. Therefore, the selection of a program to optimize training interventions could be based on the physical characteristics of the participants.
... The improvements in the described parameters could be because the PROMUFRA program would act by preventing pain from appearing after high intensity exercise. At this point it is necessary to remember that SMMR, a novel element of the MEP, exerts effects similar to those of massage [13], and is therefore capable of stimulating proprioceptors that activate pain inhibition mechanismscausing greater tolerance to stretching and a consequent increase in ROM [18]. In addition, it was hypothesized that, since it is effective in the elimination of fibrosis, SMMR would allow greater lateral transmission of force, which in turn would influence the improvement of muscle function, as can be seen in the effects analyzed in the following paragraph [13]. ...
A study was made of the effect of the PROMUFRA multicomponent frailty program upon physical frailty, kinanthropometry, pain and muscle function parameters in frail and pre-frail community-dwelling older people. Eighty-one participants were randomly allocated to the intervention group (IG) or control group (CG). The IG performed PROMUFRA for 20 weeks, using six strength exercises with three series of 8-12 repetitions until muscular failure, and seven myofascial exercises, with one set of 10 repetitions. The CG continued their routine. The frailty criteria number (FCN), kinanthropometric parameters and muscle function were measured at baseline and after the program. Between-group differences were found in the interaction for FCN, muscle mass, fat mass, skeletal muscle mass index, knee flexion range of motion (ROM), hip flexion with knee straight ROM, maximum isometric knee extension, maximum isotonic knee extension, maximum leg press and hand grip strength., and also on post-intervention frailty status. The IG showed a statistical trend towards decreased pain. In conclusion, the PROMUFRA program is a potential training approach that can bring benefits in physical frailty status, body composition, ROM and muscle function among frail or pre-frail community-dwelling older people.
... The mechanism of the increase in stretch tolerance, which is the capacity to tolerate loading before stretch termination, is unknown. However, Stove et al. performed cold pressor tests, which are related to the endogenous pain inhibitory system, and reported that ROM associated with knee extension was significantly increased in the cold pressor test group (an experimental pain group) compared with controls because cold pressor test was known to decrease pain sensitivity and thereby increasing the tolerance to pain; they also suggested that stretch tolerance was reflected by the endogenous pain inhibition (Stove et al., 2019). Furthermore, the authors reported that ROM increased owing to exercise-induced hypoalgesia, and pressure pain thresholds exhibited a significant correlation between SS and exerciseinduced hypoalgesia (Støve et al., 2021). ...
Background
No review has yet investigated acute and chronic effects of different stretching intensities, including constant-angle (CA) and constant-torque (CT) stretching.
Objective
This review aimed to investigate the acute and chronic effects of different stretching intensities on the range of motion (ROM) and passive properties.
Methods
PubMed, Scopus, and Google Scholar were used for literature search. Advanced search functions were used to identify original studies using the terms stretching intensity, constant-torque stretching, constant-angle stretching, ROM, passive stiffness, shear elastic modulus in the title or abstract. The keywords were combined using the Boolean operators “AND” and “OR”. The search for articles published from inception until 2021 was done in electronic databases.
Results and conclusion
s: Five studies compared CA and CT stretching. Three studies reported a greater decrease in passive stiffness, and two studies reported a greater ROM increase after CT than CA stretching. Twelve studies investigated the acute effects of different stretching intensities, and six reported a greater ROM increase at higher stretching intensities. Five studies reported a greater decrease in passive stiffness at higher stretching intensities, but three reported no significant differences in passive stiffness among stretching intensities. Five studies investigated the chronic effect, and four reported no significant difference in ROM change among different intensities. Three studies reported no significant changes in passive stiffness after the stretching program. We suggest that the acute effect of higher stretching intensity, including CT stretching, was more effective for changes in ROM and passive stiffness, but the chronic effect was weak.
... Individuals also responded feeling the necessity to stretch to reduce muscle pain. This result was congruent with the literature since recent evidences demonstrated the positive effects of stretching on pain sensitivity [49] with potential roles in endogenous pain inhibitory systems [50]. For that reason, 74.9% of the respondents indicated using stretching for recovery (i.e., performance or muscle soreness) and therefore after single or multiple training sessions. ...
Recommendations for prescribing stretching exercises are regularly updated. It appears that coaches progressively follow the published guidelines, but the real stretching practices of athletes are unknown. The present study aimed to investigate stretching practices in individuals from various sports or physical activity programs. A survey was completed online to determine some general aspects of stretching practices. The survey consisted of 32 multiple-choice or open-ended questions to illustrate the general practices of stretching, experiences and reasons for stretching. In total, 3546 questionnaires were analyzed (47.3% women and 52.7% men). Respondents practiced at the national/international level (25.2%), regional level (29.8%), or recreationally (44.9%). Most respondents (89.3%) used stretching for recovery (74.9%) or gains of flexibility (57.2%). Stretching was generally performed after training (72.4%). The respondents also indicated they performed stretching as a pre-exercise routine (for warm-up: 49.9%). Static stretching was primarily used (88.2%) but when applied for warm-up reasons, respondents mostly indicated performing dynamic stretching (86.2%). Only 37.1% of the respondents indicated being supervised. Finally, some gender and practice level differences were noticed. The present survey revealed that the stretching practices were only partly in agreement with recent evidence-based recommendations. The present survey also pointed out the need to improve the supervision of stretching exercises.
... DNIC suppresses pain sensitivity with the widespread distribution of monoamines such as endorphins, enkephalins and other compounds to contribute to global analgesia [80,81], thus contributing to greater non-local stretch or pain tolerance. Stove et al. [82] demonstrated this global analgesia/increased non-local stretch (pain) tolerance effect by applying a painful cold pressor test to the hand and wrist and found an increase in passive knee extension ROM. ...
Background
Stretching a muscle not only increases the extensibility or range of motion (ROM) of the stretched muscle or joint but there is growing evidence of increased ROM of contralateral and other non-local muscles and joints.
Objective
The objective of this meta-analysis was to quantify crossover or non-local changes in passive ROM following an acute bout of unilateral stretching and to examine potential dose–response relations.
Methods
Eleven studies involving 14 independent measures met the inclusion criteria. The meta-analysis included moderating variables such as sex, trained state, stretching intensity and duration.
Results
The analysis revealed that unilateral passive static stretching induced moderate magnitude (standard mean difference within studies: SMD: 0.86) increases in passive ROM with non-local, non-stretched joints. Moderating variables such as sex, trained state, stretching intensity, and duration did not moderate the results. Although stretching duration did not present statistically significant differences, greater than 240-s of stretching (SMD: 1.24) exhibited large magnitude increases in non-local ROM compared to moderate magnitude improvements with shorter (< 120-s: SMD: 0.72) durations of stretching.
Conclusion
Passive static stretching of one muscle group can induce moderate magnitude, global increases in ROM. Stretching durations greater than 240 s may have larger effects compared with shorter stretching durations.
... 5,37 It appears that massage, such as FR, modulates pain perception by lowering sympathetic activation, stimulating Ruffini bodies within connective tissue, or increasing pain thresholds by stimulating nociceptors and mechanoreceptors under the skin. 38,39 Because end feel, defined as ROM in the present study, was determined generally depending on, among other factors, subjective pain thresholds 20 and this pain inhibitory system is related with stretch tolerance in passive joint ROM positivity, 40 as another possibility, the neurological mechanism of the pain modulatory system might help increase DF ROM. ...
Context:
Several studies have reported that self-massage using a foam roller (FR) increased joint range of motion (ROM) immediately. However, the mechanism of increasing ROM by the FR intervention has not been elucidated.
Objective:
To clarify the mechanism by investigating properties and morphological changes of muscles targeted by the FR intervention.
Design:
An interventional study.
Setting:
An athletic training laboratory.
Participants:
Ten male college volunteers with no injuries in their lower limbs (mean [SD]: age 23.8 [3.2] y, height 173.2 [4.9] cm, weight 69.5 [8.6] kg).
Intervention:
The FR intervention on the right plantar flexors for 3 minutes.
Main outcome measures:
Maximum ankle ROM, muscle hardness, and fascicle length of the gastrocnemius muscle at the neutral (0°), maximum dorsiflexion, and maximum plantar flexion positions. All measurements were conducted before (PRE) and after (POST) the FR intervention.
Results:
Dorsiflexion ROM increased significantly at POST (PRE: 13.6° [8.0°], POST: 16.6° [8.4°]; P < .001), although plantar flexion ROM did not change significantly between PRE and POST (PRE: 40.0° [6.1°], POST: 41.1° [4.9°]). There was no significant difference in muscle hardness and fascicle length between PRE and POST in any of the angles.
Conclusions:
Dorsiflexion ROM increased significantly by the FR intervention in the present study; however, muscle hardness and fascicle length did not change. FR may affect not only the muscle but also the fascia, tendon, and muscle-tendon unit. The FR protocol of the present study can be applied in clinical situations, because it was found to be effective to increase ROM.
Background:
The aim of this manuscript is to investigate if stretching exercise administration order may influence outcomes pertinent to range of movement (ROM).
Methods:
A total sample of 108 participants was randomized into five groups. Eight sets of unilateral static stretching (SS) of 30s duration each with a 30s rest were administered to the right leg. One group underwent SS of the knee extensors (KE), another to the knee flexors (KF), another first to the KE and then to the KF, another first to the KF and then to the KE while the last group was used as control (CG). Each group was assessed for ROM of both lower limbs for either the KE and KF motion (passive hip extention [PHE] and passive straight leg raise [PSLR], respectively). Measures were assessed before (T0), immediately after (T1), and 15 minutes after the intervention (T2).
Results:
No differences were observed for time (T0 vs. T1 vs. T2) for all measures in the CG for both limbs. Time-x-group interactions were observed only in the intervention limb (P<0.0007 and 0.004, ES 0.73 and 0.55, for KE and KF, respectively). Within the intervention limb, a significant increase in the PHE was observed from T0 to T1 only in the KE and KF/KE groups. For measures of the PSLR, a significant increase was observed from T0 to T1 only in the KF and KE/KF groups. No differences neither for time or group were observed in the control limb.
Conclusions:
Our results highlight that exercise administration order has an effect on ROM outcomes. Measures of ROM significantly increase only for the last stretched muscle in each intervention group. No crossover effect was observed in the contralateral limb.
Objective
To determine the extent to which changes in knee range of motion (ROM) after a stretching program are related to sensory factors at the time of testing and the amount of force used during the measurement of ROM, rather than changes in soft-tissue properties.
Design
Randomized, single-blind design. Participants were randomly assigned to a control or stretching group.
Setting
Research laboratory.
Participants
Forty-four healthy volunteers (22.8±2.8 years of age; 23 men).
Interventions
The stretching group undertook static stretching twice a day for 8 weeks. The control group continued with routine activity, but was discouraged from starting a flexibility program.
Main outcome measures
ROM and tissue extensibility was assessed using a Biodex3 dynamometer, and ratings of thermal pain were collected at baseline and at 4 and 8 weeks by an examiner blinded to group assignment. Multilevel modeling was used to examine predictors of ROM across time.
Results
The stretching group showed a 6% increase, and the control group had a 2% increase, in ROM over the 8-week program. However, when fixed and random effects were tested in a complete model, the group assignment was not significant. End-point torque during ROM testing (p=0.021) and the ratings in response to thermal testing (p<0.001) were significant, however.
Conclusion
ROM measured in a testing session was not predicted by assignment to a stretching program. Rather, ROM was predicted by the ratings of thermal stimuli and the peak torque used to apply the stretch.
Purpose:
It is recognized that stretching is an effective method to chronically increase the joint range of motion. However, the effects of stretching training on the muscle-tendon structural properties remain unclear. This systematic review with meta-analysis aimed to determine whether chronic stretching alter the muscle-tendon structural properties.
Methods:
Published papers regarding longitudinal stretching (static, dynamic and/or PNF) intervention (either randomized or not) in humans of any age and health status, with more than 2 weeks in duration and at least 2 sessions per week, were searched in PubMed, PEDro, ScienceDirect and ResearchGate databases. Structural or mechanical variables from joint (maximal tolerated passive torque or resistance to stretch) or muscle-tendon unit (muscle architecture, stiffness, extensibility, shear modulus, volume, thickness, cross sectional area, and slack length) were extracted from those papers.
Results:
A total of 26 studies were selected, with a duration ranging from 3 to 8 weeks, and an average total time under stretching of 1165s per week. Small effects were seen for maximal tolerated passive torque, but trivial effects were seen for joint resistance to stretch, muscle architecture, muscle stiffness, and tendon stiffness. A large heterogeneity was seen for most of the variables.
Conclusion:
Stretching interventions with 3-8 weeks duration do not seem to change either the muscle or the tendon properties, although it increases the extensibility and tolerance to a greater tensile force. Adaptations to chronic stretching protocols shorter than 8 weeks seem to mostly occur at a sensory level. This article is protected by copyright. All rights reserved.
Recently, there has been a shift from static stretching (SS) or proprioceptive neuromuscular facilitation (PNF) stretching within a warm-up to a greater emphasis on dynamic stretching (DS). The objective of this review was to compare the effects of SS, DS, and PNF on performance, range of motion (ROM), and injury prevention. The data indicated that SS- (–3.7%), DS- (+1.3%), and PNF- (–4.4%) induced performance changes were small to moderate with testing performed immediately after stretching, possibly because of reduced muscle activation after SS and PNF. A dose–response relationship illustrated greater performance deficits with ≥60 s (–4.6%) than with <60 s (–1.1%) SS per muscle group. Conversely, SS demonstrated a moderate (2.2%) performance benefit at longer muscle lengths. Testing was performed on average 3–5 min after stretching, and most studies did not include poststretching dynamic activities; when these activities were included, no clear performance effect was observed. DS produced small-to-moderate performance improvements when completed within minutes of physical activity. SS and PNF stretching had no clear effect on all-cause or overuse injuries; no data are available for DS. All forms of training induced ROM improvements, typically lasting <30 min. Changes may result from acute reductions in muscle and tendon stiffness or from neural adaptations causing an improved stretch tolerance. Considering the small-to-moderate changes immediately after stretching and the study limitations, stretching within a warm-up that includes additional poststretching dynamic activity is recommended for reducing muscle injuries and increasing joint ROM with inconsequential effects on subsequent athletic performance.
This narrative review examined the biomechanical effect of stretching exercises on skeletal
muscles. While there is a long history of clinical research on the effect of stretching on flexibility,
there have only been a few years of research on the acute and chronic effects of stretching on the
biomechanical parameters of muscle function. The acute effect of stretching appears to be a
significant increase in range of motion primarily due to increased stretch tolerance and significant
reductions in most all forms of muscular performance. Stretching also creates significant acute
reductions in passive tension (stress-relaxation) in the muscle, but does not appear to affect its
stiffness/elasticity. Stretch training significantly increases range of motion, but it also tends to
increase the passive tension and stiffness of the musculature. Future research of human muscle in
vivo during stretching and normal movement using ultrasound promises to help clarify the effects
of stretching on the active and passive components of muscle and the many biomechanical
variables of muscular performance.
The purpose of this study was to examine opioid and endocannabinoid mechanisms of exercise-induced hypoalgesia (EIH). Fifty-eight men and women (mean age = 21 yrs) completed three sessions. During the first session, participants were familiarized with the temporal summation of heat pain and pressure pain protocols. In the exercise sessions, following double-blind administration of either an opioid antagonist (50 mg naltrexone) or placebo, participants rated the intensity of heat pulses and indicated their pressure pain thresholds (PPT) and ratings (PPR) before and after 3 minutes of submaximal isometric exercise. Blood was drawn before and after exercise. Results indicated circulating concentrations of two endocannabinoids, N-arachidonylethanolamine (AEA) and 2-arachidonoylglycerol (2-AG) as well as related lipids oleoylethanolamide (OEA), palmitoylethanolamide (PEA), N-docsahexaenoylethanolamine (DHEA), and 2-oleoylglycerol (2-OG) increased significantly (p < 0.05) following exercise. PPT increased significantly (p < 0.05) while PPR decreased significantly (p < 0.05) following exercise. Also, temporal summation ratings were significantly lower (p < 0.05) following exercise. These changes in pain responses did not differ between placebo or naltrexone conditions (p > 0.05). A significant association was found between EIH and DHEA. These results suggest involvement of a non-opioid mechanism in EIH following isometric exercise.
Perspective
Currently, the mechanisms responsible for exercise-induced hypoalgesia (EIH) are unknown. This study provides support for a potential endocannabinoid mechanism of EIH following isometric exercise.
The acute effects of stretching on peak force (F
peak), percent voluntary activation (%VA), electromyographic (EMG) amplitude, maximum range of motion (MROM), peak passive torque, the passive resistance to stretch, and the percentage of ROM at EMG onset (%EMGonset) were examined in 18 young and 19 old men. Participants performed a MROM assessment and a maximal voluntary contraction of the plantarflexors before and immediately after 20 min of passive stretching. F
peak (−11 %), %VA (−6 %), and MG EMG amplitude (−9 %) decreased after stretching in the young, but not the old (P > 0.05). Changes in F
peak were related to reductions in all muscle activation variables (r = 0.56–0.75), but unrelated to changes in the passive resistance to stretch (P ≥ 0.24). Both groups experienced increases in MROM and peak passive torque and decreases in the passive resistance to stretch. However, the old men experienced greater changes in MROM (P < 0.001) and passive resistance (P = 0.02–0.06). Changes in MROM were correlated to increases in peak passive torque (r = 0.717), and the old men also experienced a nonsignificant greater (P = 0.08) increase in peak passive torque. %EMGonset did not change from pre- to post-stretching for both groups (P = 0.213), but occurred earlier in the old (P = 0.06). The stretching-induced impairments in strength and activation in the young but not the old men may suggest that the neural impairments following stretching are gamma-loop-mediated. In addition, the augmented changes in MROM and passive torque and the lack of change in %EMGonset for the old men may be a result of age-related changes in muscle-tendon behavior.
The neuromuscular adaptations in response to muscle stretch training have not been clearly described. In the present study, changes in muscle (at fascicular and whole muscle levels) and tendon mechanics, muscle activity and spinal motoneuron excitability were examined during standardized plantar flexor stretches after 3 wk of twice-daily stretch training (4×30-s). No changes were observed in a non-exercising control group (N=9), however stretch training elicited a 19.9% increase in dorsiflexion range of motion (ROM) and 28% increase in passive joint moment at end ROM (N=12). Only a trend toward a decrease in passive plantar flexor moment during stretch (-9.9%, p=0.15) was observed and no changes in EMG amplitudes during or at end ROM were detected. Decreases in Hmax:Mmax (tibial nerve stimulation) were observed at plantar flexed (gastrocnemius medialis and soleus) and neutral (soleus only) joint angles, but not with the ankle dorsiflexed. Muscle and fascicle strain increased (12 vs. 23%) along with a decrease in muscle stiffness (-18%) during stretch to a constant target joint angle. Muscle length at end ROM increased (13%) without a change in fascicle length, fascicle rotation, tendon elongation or tendon stiffness following training. A lack of change in MVC moment and RFD at any joint angle was taken to indicate a lack of change in series compliance of the muscle-tendon unit. Thus, increases in end ROM were underpinned by increases in maximum tolerable passive joint moment ('stretch tolerance') and both muscle and fascicle elongation rather than changes in volitional muscle activation or motoneuron pool excitability.
Background:
It is known that static stretching is an appropriate means of increasing the range of motion, but information in the literature about the mechanical adaptation of the muscle-tendon unit is scarce. Therefore, the purpose of this study was to investigate the influence of a six-week static stretching training program on the structural and functional parameters of the human gastrocnemius medialis muscle and the Achilles tendon.
Methods:
A total of 49 volunteers were randomly assigned into static stretching and control groups. Before and following the stretching intervention, we determined the maximum dorsiflexion range of motion with the corresponding fascicle length and pennation angle. Passive resistive torque and maximum voluntary contraction were measured with a dynamometer. Muscle-tendon junction displacement allowed us to determine the length changes in tendon and muscle, and hence to calculate stiffness. Fascicle length, pennation angle, and muscle tendon junction displacement were measured with ultrasound.
Findings:
Mean range of motion increased significantly from 30.9 (5.3) to 36.3 (6.1) in the intervention group, but other functional (passive resistive torque, maximum voluntary contraction) and structural (fascicle length, pennation angle, muscle stiffness, tendon stiffness) parameters were unaltered.
Interpretation:
The increased range of motion could not be explained by the structural changes in the muscle-tendon unit, and was likely due to increased stretch tolerance possibly due to adaptations of nociceptive nerve endings.
The purpose of this study was to investigate the influence of a six-week ballistic stretching training program on various parameters of the human gastrocnemius medialis muscle and the Achilles tendon. It is known that ballistic stretching is an appropriate means of increasing the range of motion (RoM), but information in the literature about the mechanical adaptation of the muscle-tendon unit (MTU) is scarce. Therefore, in this study, a total of 49 volunteers were randomly assigned into ballistic stretching and control groups. Before and following the stretching intervention, we determined the maximum dorsiflexion RoM with the corresponding fascicle length and pennation angle. Passive resistive torque (PRT) and maximum voluntary contraction (MVC) were measured with a dynamometer. Muscle-tendon junction (MTJ) displacement allowed us to determine the length changes in tendon and muscle, and hence to calculate stiffness. Mean RoM increased significantly from 33.8 ± 6.3° to 37.8 ± 7.2° only in the intervention group, but other functional (PRT, MVC) and structural (fascicle length, pennation angle, muscle stiffness, tendon stiffness) parameters were unaltered. Thus, the increased RoM could not be explained by structural changes in the MTU and was likely due to increased stretch tolerance.
Proprioceptive neuromuscular facilitation (PNF) stretching techniques are commonly used in the athletic and clinical environments to enhance both active and passive range of motion (ROM) with a view to optimising motor performance and rehabilitation. PNF stretching is positioned in the literature as the most effective stretching technique when the aim is to increase ROM, particularly in respect to short-term changes in ROM. With due consideration of the heterogeneity across the applied PNF stretching research, a summary of the findings suggests that an ‘active’ PNF stretching technique achieves the greatest gains in ROM, e.g. utilising a shortening contraction of the opposing muscle to place the target muscle on stretch, followed by a static contraction of the target muscle. The inclusion of a shortening contraction of the opposing muscle appears to have the greatest impact on enhancing ROM. When including a static contraction of the target muscle, this needs to be held for approximately 3 seconds at no more than 20% of a maximum voluntary contraction. The greatest changes in ROM generally occur after the first repetition and in order to achieve more lasting changes in ROM, PNF stretching needs to be performed once or twice per week. The superior changes in ROM that PNF stretching often produces compared with other stretching techniques has traditionally been attributed to autogenic and/or reciprocal inhibition, although the literature does not support this hypothesis. Instead, and in the absence of a biomechanical explanation, the contemporary view proposes that PNF stretching influences the point at which stretch is perceived or tolerated. The mechanism(s) underpinning the change in stretch perception or tolerance are not known, although pain modulation has been suggested.
The aim of the present study was to compare the acute effects of constant torque (CT) and constant angle (CA) stretching exercises on the maximum range of motion (ROMmax), passive stiffness (PS), and ROM corresponding to the first sensation of tightness in the posterior thigh (FSTROM). Twenty three sedentary men (aged 19 to 33 years) went through 1 familiarization session and afterwards proceeded randomly to both CA and CT treatment stretching conditions, on separate days. An isokinetic dynamometer was used to analyze hamstring muscles during passive knee extension. The subjects performed 4 stretches of 30 seconds each, with a 15-second interval between them. In the CA stretching, the subject reached a certain ROM (95% of ROMmax) and the angle was kept constant. On the other hand in the CT stretching exercise, the volunteer reached a certain resistance torque (RT) (corresponding to 95% of ROMmax) and it was kept constant. The results showed an increase in ROMmax for both CA and CT (p < 0.001), but the increase was greater for CT than for CA (CA vs. CT in post-stretching, p = 0.002). Although the PS decreased for both CA and CT (p < 0.001), the decrease was greater for CT than for CA (CA vs. CT in post-stretching, p = 0.002). The FSTROM increased for both CA and CT, but the increase for CT was greater than that for CA (CA vs. CT in post-stretching, p = 0.003). The greater increase in ROMmax for the CT stretch may be explained by greater changes in the biomechanical properties of the muscle-tendon unit and stretch tolerance, as indicated by the passive stiffness and FSTROM results.
'Diffuse noxious inhibitory controls' (DNIC), a form of supraspinal descending endogenous analgesia, requires a noxious conditioning stimulus for pain attenuation. This may be partly dependent on a distraction effect. The term "conditioned pain modulation" (CPM) has recently been introduced to describe the psychophysical paradigm to test DNIC. The present study aimed to determine whether distraction and tonic heat stimulation inhibit pain through the same or different mechanisms by looking at whether there is a similar or even an additive effect on pain attenuation. Test pain was brief heat stimulation applied to the left volar of 34 healthy volunteers. For conditioning, the right hand was immersed in 46.5 degrees C water. Distraction was provided by three different difficulty levels of continuous cognitive visual tasks. Experimental blocks consisted of test pain: (1) alone; 'baseline', (2) with conditioning pain; 'CPM', (3) with distraction; 'distraction' and (4) with conditioning pain and distraction; 'combined'. They were randomized and repeated three times and pain intensity and unpleasantness rated. Results showed an overall effect of experimental block on test pain intensity (P=0.0125). Post-hoc tests revealed a significant reduction in pain intensity ratings under Combined (21.2+/-2.3; mean+/-SEM) compared to CPM alone (16.0+/-2.3) (P<0.05). Furthermore, at all levels of distraction there were always a few subjects who were not distracted despite expressing CPM. Based on the additive effect of CPM and distraction on pain inhibition, and the cases of no distraction despite CPM, we suggest that CPM acts independently from distraction.
Stretch is commonly prescribed as part of physical rehabilitation in pain management programs, yet little is known about its effectiveness.
A randomized controlled trial was conducted to investigate the effects of a 3-week stretch program on muscle extensibility and stretch tolerance in patients with chronic musculoskeletal pain.
A within-subject design was used, with one leg of each participant randomly allocated to an experimental (stretch) condition and the other leg randomly allocated to a control (no-stretch) condition.
Thirty adults with pain of musculoskeletal origin persisting for at least 3 months were recruited from patients enrolled in a multidisciplinary pain management program at a hospital in Sydney, Australia.
The hamstring muscles of the experimental leg were stretched daily for 1 minute over 3 weeks; the control leg was not stretched. This intervention was embedded within a pain management program and supervised by physical therapists.
Primary outcomes were muscle extensibility and stretch tolerance, which were reflected by passive hip flexion angles measured with standardized and nonstandardized torques, respectively. Initial measurements were taken before the first stretch on day 1, and final measurements were taken 1 to 2 days after the last stretch. A blinded assessor was used for testing.
Stretch did not increase muscle extensibility (mean between-group difference in hip flexion was 1 degrees , 95% confidence interval=-2 degrees to 4 degrees ), but it did improve stretch tolerance (mean between-group difference in hip flexion was 8 degrees , 95% confidence interval=5 degrees to 10 degrees ).
Three weeks of stretch increases tolerance to the discomfort associated with stretch but does not change muscle extensibility in patients with chronic musculoskeletal pain.
In chronic musculoskeletal pain conditions, the balance between supraspinal facilitation and inhibition of pain shifts towards an overall decrease in inhibition. Application of a tonic painful stimulus results in activation of diffuse noxious inhibitory controls (DNIC). The aims of the present experimental human study were (1) to compare DNIC, evoked separately, by hypertonic saline (6%)-induced muscle pain (tibialis anterior) or cold pressor pain; (2) to investigate DNIC evoked by concomitant experimental muscle pain and cold pressor pain, and (3) to analyze for gender differences. Ten males and 10 age matched females participated in two sessions. In the first session unilateral muscle pain or unilateral cold pressor pain were induced separately; in the second session unilateral muscle pain and unilateral cold pressor pain were induced concomitantly. Pressure pain thresholds (PPT) were measured around the knee joint before, during, and after DNIC induction. Cold pressor pain increased PPT in both males and females with greater increases in males. Hypertonic saline-evoked muscle pain significantly increased PPT in males but not in females. When cold pressor and muscle pain were applied concomitantly the PPT increases were smaller when compared to the individual sessions. This study showed for the first time that two concurrent conditioning tonic pain stimuli (muscle pain and cold pressor pain) cause less DNIC compared with either of the conditioning stimuli given alone; and males showed greater DNIC than females. This may explain why patients with chronic musculoskeletal pain have impaired DNIC.
To examine electromyography (EMG) activity, passive torque, and stretch perception during static stretch and contract-relax stretch.
Two separate randomized crossover protocols: (1) a constant angle protocol on the right side, and (2) a variable angle protocol on the left side.
10 male volunteers.
Stretch-induced mechanical response in the hamstring muscles during passive knee extension was measured as knee flexion torque (Nm) while hamstring surface EMG was measured. Final position was determined by extending the knee to an angle that provoked a sensation similar to a stretch maneuver. Constant angle stretch: The knee was extended to 10 degree below final position, held 10sec, then extended to the final position and held for 80 sec. Variable angle stretch: The knee was extended from the starting position to 10 degrees below the final position, held 10sec, then extended to the onset of pain. Subjects produced a 6-sec isometric contraction with the hamstring muscles 10 degrees below the final position in the contract-relax stretch, but not in the static stretch.
Passive torque, joint range of motion, velocity, and hamstring EMG were continuously recorded.
Constant angle contract-relax and static stretch did not differ in passive torque or EMG response. In the final position, passive torque declined 18% to 21% in both contract-relax and static stretch (p<.001), while EMG activity was unchanged. In the variable angle protocol, maximal joint angle and corresponding passive torque were significantly greater in contract-relax compared with static stretch(p<.01), while EMG did not differ.
At a constant angle the viscoelastic and EMG response was unaffected by the isometric contraction. The variable angle protocol demonstrated that PNF stretching altered stretch perception.
Over the past 20 years a number of studies have examined whether analgesia occurs following exercise. Exercise involving running and cycling have been examined most often in human research, with swimming examined most often in animal research. Pain thresholds and pain tolerances have been found to increase following exercise. In addition, the intensity of a given pain stimulus has been rated lower following exercise. There have been a number of different noxious stimuli used in the laboratory to produce pain, and it appears that analgesia following exercise is found more consistently for studies that used electrical or pressure stimuli to produce pain, and less consistently in studies that used temperature to produce pain. There is also limited research indicating that analgesia can occur following resistance exercise and isometric exercise. Currently, the mechanism(s) responsible for exercise-induced analgesia are poorly understood. Although involvement of the endogenous opioid system has received mixed support in human research, results from animal research seem to indicate that there are multiple analgesia systems, including opioid and non-opioid systems. It appears from animal research that properties of the exercise stressor are important in determining which analgesic system is activated during exercise.
The purpose of this study was to analyze the accuracy of commonly used techniques for the measurement of knee extension and to compare them with a new measurement device. The bars of an external fixator were used to determine reference knee extension angles of 15 human cadavers. These angles were compared with measurements of knee extension on radiographs limited to the knee joint. Extension was determined in various knee positions using a generic goniometer and a novel long arm goniometer. In a clinical study, two independent examiners categorized knee extension performance according to the IKDC. Sixteen knees with deficits in the range of motion were rated using a generic goniometer, a long arm goniometer and the novel extension measurement device. The radiological measurement of knee extension angles that were restricted to the shaft of femur and tibia had a systematic error of -5.2 +/- 1.9 degrees compared with the lines created by the centers of rotation. In the experimental setup, the mean absolute deviations were 3.92 +/- 1.41 degrees with a generic goniometer and 1.22 +/- 0.20 degrees with the extension measurement device. The variance of the measurements was significantly lower (2.64 +/- 0.28) than with the generic goniometer (23.72 +/- 4.39; P < 0.05). Correspondence in the IKDC rating was 63% using a standard goniometer, 50% with the long arm goniometer, and 96% using the novel device. Radiological measurements of knee extension limited to the area of the knee joint deviates systematically from measurements of the total axis of the bones. A precision goniometer that utilizes bony landmarks of the tibia and femur is superior in accuracy compared with standard and long arm goniometer techniques.
This study quantitatively assessed the mechanical reliability and validity of position, torque and velocity measurements of the Biodex System 3 isokinetic dynamometer. Trial-to-trial and day-to-day reliability were assessed during three trials on two separate days. To assess instrument validity, measurement of each variable using the Biodex System 3 dynamometer was compared to a criterion measure of position, torque and velocity. Position was assessed at 5 degrees increments across the available range of motion of the dynamometer. Torque measures were assessed isometrically by hanging six different calibrated weights from the lever arm. Velocity was assessed (30 degrees/s to 500 degrees/s) across a 70 degrees arc of motion by manually accelerating the weighted lever arm. With the exception of a systematic decrease in velocity at speeds of 300 degrees/s and higher, the Biodex System 3 performed with acceptable mechanical reliability and validity on all variables tested.
Proprioceptive neuromuscular facilitation (PNF) stretching techniques are commonly used in the athletic and clinical environments to enhance both active and passive range of motion (ROM) with a view to optimising motor performance and rehabilitation. PNF stretching is positioned in the literature as the most effective stretching technique when the aim is to increase ROM, particularly in respect to short-term changes in ROM. With due consideration of the heterogeneity across the applied PNF stretching research, a summary of the findings suggests that an 'active' PNF stretching technique achieves the greatest gains in ROM, e.g. utilising a shortening contraction of the opposing muscle to place the target muscle on stretch, followed by a static contraction of the target muscle. The inclusion of a shortening contraction of the opposing muscle appears to have the greatest impact on enhancing ROM. When including a static contraction of the target muscle, this needs to be held for approximately 3 seconds at no more than 20% of a maximum voluntary contraction. The greatest changes in ROM generally occur after the first repetition and in order to achieve more lasting changes in ROM, PNF stretching needs to be performed once or twice per week. The superior changes in ROM that PNF stretching often produces compared with other stretching techniques has traditionally been attributed to autogenic and/or reciprocal inhibition, although the literature does not support this hypothesis. Instead, and in the absence of a biomechanical explanation, the contemporary view proposes that PNF stretching influences the point at which stretch is perceived or tolerated. The mechanism(s) underpinning the change in stretch perception or tolerance are not known, although pain modulation has been suggested.
Background Tendinopathy is often a chronic condition. The mechanisms behind persistent tendon pain are not yet fully understood. It is unknown whether, similar to other persistent pain states, central pain mechanisms contribute to ongoing tendon pain.
Aim We investigated the presence of altered central pain processing in Achilles tendinopathy by assessing the conditioned pain modulation (CPM) effect in people with and without Achilles tendinopathy.
Methods 20 people with Achilles tendinopathy and 23 healthy volunteers participated in this cross-sectional study. CPM was assessed by the cold pressor test. The pressure pain threshold (PPT) was recorded over the Achilles tendon before and during immersion of the participant's hand into cold water. The CPM effect was quantified as the absolute difference in PPT before and during the cold pressor test.
Results An increase in PPT was observed in the Achilles tendinopathy and control group during the cold pressor test (p<0.001). However, the CPM effect was stronger in the control group (mean difference=160.5 kPa, SD=84.9 kPa) compared to the Achilles tendinopathy group (mean difference=36.4 kPa, SD=68.1 kPa; p<0.001).
Summary We report a reduced conditioned pain modulation effect in people with Achilles tendinopathy compared to people without Achilles tendinopathy. A reduced conditioned pain modulation effect reflects altered central pain processing which is believed to contribute to the persistence of pain in other conditions. Altered central pain processing may also be an important factor in persistent tendon pain that has traditionally been regarded to be dominated by peripheral mechanisms.
Objectives: In chronic pain patients impaired conditioned pain modulation (CPM) and exercise-induced hypoalgesia (EIH) have been reported. No studies have compared CPM and EIH in chronic musculoskeletal pain patients with high pain sensitivity compared with low pain sensitivity.
Methods: On two days, manual pressure pain thresholds (PPTs) were recorded at the legs, arm, and shoulder in 61 chronic pain patients and they performed cold pressor test, two exercise conditions (bicycling and isometric contraction), and a control condition in a randomized and counterbalanced order. Pressure pain thresholds, pain tolerance, pain tolerance limit, and temporal summation of pain were assessed with cuff algometry before and after test conditions. Based on a median split of the average PPTs for women and men, respectively, low (LPS; N=30) and high (HPS; N=31) pain-sensitivity groups were formed.
Results: At baseline, cuff pressure pain threshold and pain tolerance were decreased and temporal summation of pain was increased in the HPS group (P<0.02). Cuff pressure pain threshold increased and pain tolerance limit decreased after cold pressor test and exercises in LPS (P<0.001). Temporal summation of pain was increased after bicycling in HPS (P<0.005). Pain tolerance increased after cold pressor test and exercise in both groups (P<0.001).
Discussion: CPM and EIH were partly impaired in chronic pain patients with high versus less pain sensitivity suggesting that the CPM and EIH responses depends on the degree of pain sensitivity. This has clinical implications as clinicians should evaluate pain sensitivity when considering treatment options utilizing the descending modulatory pain control.
The cold pressor task (CPT) was originally developed as a clinically indicative cardiovascular test, and quantifies vascular response and pulse excitability when a subject's hand is immersed into ice water. Since the test procedure results in a gradually increasing cold pain, the CPT has been widely used as a nociceptive stimulus in experimental studies on adults and children.
To evaluate the test-retest stability of response patterns using the CPT as a measure of pain threshold and pain tolerance.
In the present study, sixty-one undergraduate students received painful stimulation using the CPT either at 4°C or 6°C. Measurements of pain threshold, pain tolerance and pain intensity ratings using the short form of the McGill pain questionnaire (SF-MPQ), were derived. The assessment was repeated twice over an interval of 2 weeks. Test-Retest stability was assessed within a three-layered approach, using ANOVAs, interclass correlation coefficients and standard error of the mean. A Bland-Altman analysis was also performed. Possible predictors of pain threshold and pain tolerance were assessed using random effect panel regression models.
No significant differences emerged as a function of temperature (4°C or 6°C) on pain threshold, pain tolerance, and pain ratings. Environmental variables (room temperature and humidity) show no impact on measures of pain threshold and pain tolerance.
Consistent with previous findings, regression analysis reveals that age is significantly associated with pain tolerance. The CPT procedure shows excellent 2 week test-retest stability to assess pain threshold and pain tolerance within a student population.
Pain inhibitory mechanisms are often assessed by paradigms of exercise-induced hypoalgesia (EIH) and conditioned pain modulation (CPM). In this study it was hypothesised that the spatial and temporal manifestations of EIH and CPM were comparable. Eighty healthy subjects (40 females), between 18-65 years participated in this randomized repeated-measures crossover trial with data collection on two different days. CPM was assessed by two different cold pressor tests (hand,foot). EIH was assessed through two intensities of aerobic bicycling exercises and two intensities of isometric muscle contraction exercises (arm,leg). Pressure pain thresholds (PPTs) were recorded before, during, after, and 15 min after conditioning/exercise, at sites local and remote to the extremity used for cold pressor stimulation and exercise. PPTs increased at local as well as remote sites during both cold pressor tests and after all of the exercise conditions, except low intensity bicycling. EIH after bicycling was increased in women compared to men. CPM and the EIH response after isometric exercises were comparable in men and women and not affected by age. The EIH response was larger in the exercising body part compared with non-exercising body parts for all exercise conditions. High intensity exercise produced larger EIH response compared with low intensity exercise. The change in PPTs during cold pressor test and the change in PPTs after exercises were not correlated. The CPM response was not dominated by local manifestations and the effect was only seen during the stimulation, whereas exercise had larger local manifestations and the effects were also found after exercise.
Unlabelled:
This study investigated if conditioned pain modulation (CPM) varies across the menstrual cycle in healthy, normally menstruating women and investigated correlations between sex hormone levels and CPM across the menstrual cycle. Thirty-six normally menstruating women were tested during 3 phases of the menstrual cycle: early follicular, ovulatory, and midluteal, confirmed by hormone determinations. Mechanical pressure (test stimulus) was applied to the masseter muscle and the induced pain assessed before, during, and after immersion of the hand into ice water (conditioning stimulus) to activate CPM or tepid water (control). Conditioning pain, ie, pain in the hand during CPM/control experiment, and tolerance time were also measured. Test pain intensity was suppressed during CPM in all phases (P < .001), but with more effective suppression during the ovulatry than during the early follicular phase (P < .05). There were no changes in test pain intensity during the control experiment and no significant differences in conditioning pain, or tolerance time between phases. In conclusion, our results showed more effective pain modulation in the ovulatory phase of the menstrual cycle, when estradiol levels are high and progesterone levels are low, than in the early follicular phase when both these hormones are low.
Perspective:
Deficient pain modulation is believed to be an important pathogenic factor in many chronic pain conditions that affect women. This article shows that sex hormones modulate conditioned pain modulation, because pain inhibition was more effective in the ovulatory phase of the menstrual cycle than in the early follicular phase.
Meniscectomy and articular cartilage damage have been found to increase the prevalence of osteoarthritis after anterior cruciate ligament reconstruction, but the effect of knee range of motion has not been extensively studied.
The prevalence of osteoarthritis as observed on radiographs would be higher in patients who had abnormal knee range of motion compared with patients with normal knee motion, even when grouped for like meniscal or articular cartilage lesions.
Cohort study; Level of evidence, 3.
We prospectively followed patients at a minimum of 5 years after surgery. The constant goal of rehabilitation was to obtain full knee range of motion as quickly as possible after surgery and maintain it in the long term. Range of motion and radiographs were evaluated at the time of initial return to full activities (early follow-up) and final follow-up according to International Knee Documentation Committee (IKDC) objective criteria. A patient was considered to have normal range of motion if extension was within 2° of the opposite knee including hyperextension and knee flexion was within 5°. Radiograph findings were rated as abnormal if any signs of joint space narrowing, sclerosis, or osteophytes were present.
Follow-up was obtained for 780 patients at a mean of 10.5 ± 4.2 years after surgery. Of these, 539 had either normal or abnormal motion at both early and final follow-up. In 479 patients who had normal extension and flexion at both early and final follow-up, 188 (39%) had radiographic evidence of osteoarthritis versus 32 of 60 (53%) patients who had less than normal extension or flexion at early and final follow-up (P = .036). In subgroups of patients with like meniscal status, the prevalence of normal radiograph findings was significantly higher in patients with normal motion at final follow-up versus patients with motion deficits. Multivariate logistic regression analysis of categorical variables showed that abnormal knee flexion at early follow-up, abnormal knee extension at final follow-up, abnormal knee flexion at final follow-up, partial medial meniscectomy, and articular cartilage damage were significant factors related to the presence of osteoarthritis on radiographs. Abnormal knee extension at early follow-up showed a trend toward statistical significance (P = .0544). Logistic regression showed the odds of having osteoarthritis were 2 times more for patients with abnormal range of motion at final follow-up; these odds were similar for those with partial medial meniscectomy and articular cartilage damage.
The prevalence of osteoarthritis on radiographs in the long term after anterior cruciate ligament reconstruction is lower in patients who achieve and maintain normal knee motion, regardless of the status of the meniscus.
Background:
Many people stretch before or after engaging in athletic activity. Usually the purpose is to reduce risk of injury, reduce soreness after exercise, or enhance athletic performance. This is an update of a Cochrane review first published in 2007.
Objectives:
The aim of this review was to determine effects of stretching before or after exercise on the development of delayed-onset muscle soreness.
Search strategy:
We searched the Cochrane Bone, Joint and Muscle Trauma Group Specialised Register (to 10 August 2009), the Cochrane Central Register of Controlled Trials (2010, Issue 1), MEDLINE (1966 to 8th February 2010), EMBASE (1988 to 8th February 2010), CINAHL (1982 to 23rd February 2010), SPORTDiscus (1949 to 8th February 2010), PEDro (to 15th February 2010) and reference lists of articles.
Selection criteria:
Eligible studies were randomised or quasi-randomised studies of any pre-exercise or post-exercise stretching technique designed to prevent or treat delayed-onset muscle soreness (DOMS). For the studies to be included, the stretching had to be conducted soon before or soon after exercise and muscle soreness had to be assessed.
Data collection and analysis:
Risk of bias was assessed using The Cochrane Collaboration's 'Risk of bias' tool and quality of evidence was assessed using GRADE. Estimates of effects of stretching were converted to a common 100-point scale. Outcomes were pooled in fixed-effect meta-analyses.
Main results:
Twelve studies were included in the review. This update incorporated two new studies. One of the new trials was a large field-based trial that included 2377 participants, 1220 of whom were allocated stretching. All other 11 studies were small, with between 10 and 30 participants receiving the stretch condition. Ten studies were laboratory-based and other two were field-based. All studies were exposed to either a moderate or high risk of bias. The quality of evidence was low to moderate.There was a high degree of consistency of results across studies. The pooled estimate showed that pre-exercise stretching reduced soreness at one day after exercise by, on average, half a point on a 100-point scale (mean difference -0.52, 95% CI -11.30 to 10.26; 3 studies). Post-exercise stretching reduced soreness at one day after exercise by, on average, one point on a 100-point scale (mean difference -1.04, 95% CI -6.88 to 4.79; 4 studies). Similar effects were evident between half a day and three days after exercise. One large study showed that stretching before and after exercise reduced peak soreness over a one week period by, on average, four points on a 100-point scale (mean difference -3.80, 95% CI -5.17 to -2.43). This effect, though statistically significant, is very small.
Authors' conclusions:
The evidence from randomised studies suggests that muscle stretching, whether conducted before, after, or before and after exercise, does not produce clinically important reductions in delayed-onset muscle soreness in healthy adults.
A number of studies have investigated the efficacy of several repetitions of proprioceptive neuromuscular facilitation stretching (PNF) and static stretching (SS). However, there is limited research comparing the effects of a single bout of these stretching maneuvers. The aim of this study was to compare the effectiveness of a single bout of a therapist-applied 30-second SS vs. a single bout of therapist-applied 6-second hamstring (agonist) contract PNF. Forty-five healthy subjects between the ages of 21 and 35 were randomly allocated to 1 of the 2 stretching groups or a control group, in which no stretching was received. The flexibility of the hamstring was determined by a range of passive knee extension, measured using a universal goniometer, with the subject in the supine position and the hip at 90° flexion, before and after intervention. A significant increase in knee extension was found for both intervention groups after a single stretch (SS group = 7.53°, p < 0.01 and PNF group = 11.80°, p < 0.01). Both interventions resulted in a significantly greater increase in knee extension when compared to the control group (p < 0.01). The PNF group demonstrated significantly greater gains in knee extension compared to the SS group (mean difference 4.27°, p < 0.01). It can be concluded that a therapist applied SS or PNF results in a significant increase in hamstring flexibility. A hamstring (agonist) contract PNF is more effective than an SS in a single stretching session. These findings are important to physiotherapists or trainers working in clinical and sporting environments. Where in the past therapists may have spent time conducting multiple repetitions of a PNF and an SS, a single bout of either technique may be considered just as effective. A key component of the study methodology was the exclusion of a warm-up period before stretching. Therefore, the findings of efficacy of a single PNF are of particular relevance in sporting environments and busy clinical settings where time may be limited.
The purpose of the present study was to examine the effects of constant-angle (CA) and constant-torque (CT) stretching of the leg flexors on peak torque (PT), EMGRMS at PT, passive range of motion (PROM), passive torque (PAS(TQ)), and musculotendinous stiffness (MTS).
Seventeen healthy men (mean ± SD: age = 21.4 ± 2.4 yr) performed a PROM assessment and an isometric maximal voluntary contraction of the leg flexors at a knee joint angle of 80° below full leg extension before and after 8 min of CA and CT stretching. PASTQ and MTS were measured at three common joint angles for before and after assessments.
PT decreased (mean ± SE = 5.63 ± 1.65 N·m) (P = 0.004), and EMG(RMS) was unchanged (P > 0.05) from before to after stretching for both treatments. PROM increased (5.00° ± 1.03°) and PASTQ decreased at all three angles before to after stretching (angle 1 = 5.03 ± 4.52 N·m, angle 2 = 6.30 ± 5.88 N·m, angle 3 = 6.68 ± 6.33 N·m) for both treatments (P ≤ 0.001). In addition, MTS decreased at all three angles (angle 1 = 0.23 ± 0.29 N·m·°(-1), angle 2 = 0.26 ± 0.35 N·m·°(-1), angle 3 = 0.28 ± 0.44 N·m·°(-1)) after the CT stretching treatment (P < 0.005); however, MTS was unchanged after CA stretching (P > 0.05).
PT, EMG(RMS), PROM, and PASTQ changed in a similar manner after stretching treatments; however, only CT stretching resulted in a decrease in MTS. Therefore, if the primary goal of the stretching routine is to decrease MTS, these results suggest that CT stretching (constant pressure) may be more appropriate than a stretch held at a constant muscle length (CA stretching).
The ability of a painful stimulus to suppress pain in another, remote area (DNIC) has been intensely studied. However, the effect of the distance between the two painful stimuli and the attentional factors during the measurement of pain perception received minimal treatment. We evaluated the effect of these factors on DNIC and on the interaction between DNIC and spatial summation (SS) of pain. Subjects rated the intensity of a test stimulus (applied to one hand) alone and simultaneously with conditioning stimuli applied to four different locations; 5 and 30cm from the test stimulus on the same hand, the contralateral hand and contralateral leg. In each location, ratings were performed under three different instructions: summation, attention to test stimulus, attention to conditioning stimulus. The distance between the conditioning and test stimulus significantly affected pain perception (p<0.01) regardless of the instructions; SS occurred only at a distance of 5cm and DNIC occurred only in the remaining distances. DNIC's magnitude increased as the distance between the two stimuli increased (p<0.01). However, the instruction to summate attenuated DNIC and the DNIC instruction attenuated SS of pain. Attention to the conditioning stimulus induced a stronger DNIC than attention to the test stimulus (p<0.001). We conclude that (1) DNIC and SS of pain appear to be antagonistic processes. (2) DNIC is affected by the distance between two noxious stimuli and to a lesser extent, by attention. (3) The interaction between DNIC, SS and attention is complex and reflects the role of sensory-cognitive integration in pain perception.
There is a growing body of knowledge on pain modulation in various disease states. This article reviews the state of the art regarding the clinical relevance of pain inhibition as revealed by 'pain inhibits pain' test paradigms, trying to organize the clinically relevant data, and emphasizing the pathophysiology of pain. In line with recent experts' recommendations, the term conditioned pain modulation (CPM) will be used, replacing the previous terms 'diffuse noxious inhibitory control (DNIC)' or 'DNIC-like' effects.
Most of the work in this context was done on the idiopathic pain syndromes, such as irritable bowel syndrome, temporomandibular disorders, fibromyalgia, and tension type headache. The pattern of reduced CPM efficiency seems common to these syndromes and an assertion is made that low CPM efficiency, reflecting low pain inhibitory capacity, is a pathogenetic factor in the development of the idiopathic pain syndromes. Low CPM efficiency was shown to be predictive of acute and chronic postoperative pain, and, in some reports, to be associated with neuropathic pain levels.
Low CPM efficiency is associated with higher pain morbidity and vice versa. Further work is awaited on clarifying plasticity of CPM and its relevance to selection and efficacy of pain therapy.
The surface electromyographic (sEMG) signal that originates in the muscle is inevitably contaminated by various noise signals or artifacts that originate at the skin-electrode interface, in the electronics that amplifies the signals, and in external sources. Modern technology is substantially immune to some of these noises, but not to the baseline noise and the movement artifact noise. These noise sources have frequency spectra that contaminate the low-frequency part of the sEMG frequency spectrum. There are many factors which must be taken into consideration when determining the appropriate filter specifications to remove these artifacts; they include the muscle tested and type of contraction, the sensor configuration, and specific noise source. The band-pass determination is always a compromise between (a) reducing noise and artifact contamination, and (b) preserving the desired information from the sEMG signal. This study was designed to investigate the effects of mechanical perturbations and noise that are typically encountered during sEMG recordings in clinical and related applications. The analysis established the relationship between the attenuation rates of the movement artifact and the sEMG signal as a function of the filter band pass. When this relationship is combined with other considerations related to the informational content of the signal, the signal distortion of filters, and the kinds of artifacts evaluated in this study, a Butterworth filter with a corner frequency of 20 Hz and a slope of 12 dB/oct is recommended for general use. The results of this study are relevant to biomechanical and clinical applications where the measurements of body dynamics and kinematics may include artifact sources.
Various theories have been proposed to explain increases in muscle extensibility observed after intermittent stretching. Most of these theories advocate a mechanical increase in length of the stretched muscle. More recently, a sensory theory has been proposed suggesting instead that increases in muscle extensibility are due to a modification of sensation only. Studies that evaluated the biomechanical effect of stretching showed that muscle length does increase during stretch application due to the viscoelastic properties of muscle. However, this length increase is transient, its magnitude and duration being dependent upon the duration and type of stretching applied. Most of these studies suggest that increases in muscle extensibility observed after a single stretching session and after short-term (3- to 8-week) stretching programs are due to modified sensation. The biomechanical effects of long-term (>8 weeks) and chronic stretching programs have not yet been evaluated. The purposes of this article are to review each of these proposed theories and to discuss the implications for research and clinical practice.
To compare a passive and an active stretching technique to determine which one would produce and maintain the greatest gain in hamstring flexibility. To determine whether a passive or an active stretching technique results in a greater increase in hamstring flexibility and to compare whether the gains are maintained.
Randomized controlled trial.
Institutional.
Sixty-five volunteer healthy subjects completed the enrollment questionnaire, 33 completed the required 75% of the treatment after 6 weeks, and 22 were assessed 4 weeks after the training interruption.
A 6-week stretching program with subjects divided into 2 groups with group 1 performing active stretching exercises and group 2 performing passive stretching exercises.
Range of motion (ROM) was measured after 3 and 6 weeks of training and again 4 weeks after the cessation of training and compared with the initial measurement.
After 3 weeks of training, the mean gain in group 1 (active stretching) on performing the active knee extension range of motion (AKER) test was 5.7 degrees, whereas the mean gain in group 2 (passive stretching) was 3 degrees (P = .015). After 6 weeks of training, the mean gain in group 1 was 8.7 degrees , whereas the mean gain in group 2 was 5.3 degrees (P = .006). Twenty-two subjects were reassessed 4 weeks after the cessation of the training with the maintained gain of ROM in group 1 being 6.3 degrees , whereas the maintained gain in group 2 was 0.1 degrees (P = .003).
Active stretching produced the greater gain in the AKER test, and the gain was almost completely maintained 4 weeks after the end of the training, which was not seen with the passive stretching group. Active stretching was more time efficient compared with the static stretching and needed a lower compliance to produce effects on flexibility.
Hamstring muscle injury is a complex problem for athletes, physicians, physical therapists, and athletic trainers. This injury tends to recur and to limit participation in athletic competition. The etiology of hamstring muscle injury continues to be confusing and incomplete for clinicians and researchers. The purposes of this paper are: 1) to review briefly hamstring muscle group anatomy and function, 2) to review the clinical and animal research literature concerning the role of strength, flexibility, warm-up, and fatigue in hamstring muscle injury, 3) to present an evaluation and rehabilitation scheme for hamstring muscle injury, 4) to describe a theoretical multiple factor hamstring injury model, and 5) to offer recommendations concerning prevention of hamstring muscle injury. During preseason screening and rehabilitation following hamstring muscle injury, clinicians should consider the influence of hamstring strength, flexibility, warm-up, and fatigue on muscle performance. Additional research concerning these factors is recommended. J Orthop Sports Phys Ther 1992;16(1):12-18.
Cross-sectional area, stiffness, viscoelastic stress relaxation, stretch tolerance and EMG activity of the human hamstring muscle group were examined in endurance-trained athletes with varying flexibility. Subjects were defined as tight (n = 10) or normal (n = 8) based on a clinical toe-touch test. Cross-sectional area was computed from magnetic resonance imagining (MRI) images. Torque (Nm) offered by the hamstring muscle group, electromyographic (EMG) activity, knee joint angle and velocity were continuously monitored during two standardized stretch protocols. Protocol 1 consisted of a slow stretch at 0.087 rad/s (dynamic phase) to a pre-determined final angle followed by a 90-s static phase. In the dynamic phase final angle and stiffness was lower in tight (28.0+/-2.9 Nm/rad) than normal subjects (54.9+/-6.5 Nm/rad), P<0.01. In the static phase tight subjects had lower peak (15.4+/-1.8 Nm) and final torque (10.8+/-1.6 Nm) than normal subjects (31.6+/-4.1 Nm, 24.1+/-3.7 Nm, respectively)(P<0.01), but torque decline was similar. Protocol 2 consisted of a slow stretch to the point of pain and here tight subjects reached a lower maximal angle, torque, stiffness and energy than normal subjects (P<0.01). On the other hand, stiffness was greater in tight subjects in the common range (P<0.01). Cross-sectional area of the hamstring muscles and EMG activity during the stretch did not differ between the groups. However, lateral hamstring cross-sectional area was positively related to mid-range stiffness (P<0.05), but inversely related to final stiffness, peak torque and the toe-touch test (P<0.01). Final angle and peak torque in protocol 1 combined to improve the predictability of the toe-touch test (R2=0.77, P<0.001). These data show that the toe-touch test is largely a measure of hamstring flexibility. Further, subjects with a restricted joint range of movement on a clinical toe-touch test have stiffer hamstring muscles and a lower stretch tolerance.
Despite limited scientific knowledge, stretching of human skeletal muscle to improve flexibility is a widespread practice among athletes. This article reviews recent findings regarding passive properties of the hamstring muscle group during stretch based on a model that was developed which could synchronously and continuously measure passive hamstring resistance and electromyographic activity, while the velocity and angle of stretch was controlled. Resistance to stretch was defined as passive torque (Nm) offered by the hamstring muscle group during passive knee extension using an isokinetic dynamometer with a modified thigh pad. To simulate a clinical static stretch, the knee was passively extended to a pre-determined final position (0.0875 rad/s, dynamic phase) where it remained stationary for 90 s (static phase). Alternatively, the knee was extended to the point of discomfort (stretch tolerance). From the torque-angle curve of the dynamic phase of the static stretch, and in the stretch tolerance protocol, passive energy and stiffness were calculated. Torque decline in the static phase was considered to represent viscoelastic stress relaxation. Using the model, studies were conducted which demonstrated that a single static stretch resulted in a 30% viscoelastic stress relaxation. With repeated stretches muscle stiffness declined, but returned to baseline values within 1 h. Long-term stretching (3 weeks) increased joint range of motion as a result of a change in stretch tolerance rather than in the passive properties. Strength training resulted in increased muscle stiffness, which was unaffected by daily stretching. The effectiveness of different stretching techniques was attributed to a change in stretch tolerance rather than passive properties. Inflexible and older subjects have increased muscle stiffness, but a lower stretch tolerance compared to subjects with normal flexibility and younger subjects, respectively. Although far from all questions regarding the passive properties of humans skeletal muscle have been answered in these studies, the measurement technique permitted some initial important examinations of vicoelastic behavior of human skeletal muscle.
A stooping (slump) position is believed to add tension to the nerve tissue complex. This study was designed to determine whether this position would have an effect on the stretch tolerance in a passive knee extension. Thirteen healthy individuals were tested. The knee extension was stopped by the subjects at “onset of pain”. Joint range of motion and passive resistance to the extension were recorded in four test situations: upright sitting and stooping position, with the ankle joint in either the neutral or maximal dorsi-flexed position.
A significant decrease in range of motion was seen when shifting from upright to stooping position: Δangle −2.4° (P<0.01). According to this, the passive tissue tension was accepted at significantly lower values in stooping position: Δtorque −1.2 N m (P<0.01). Testing with maximal dorsi-flexion of the ankle showed more pronounced changes: Δangle −3.4° (P<0.001); Δtorque −2.3 N m (P<0.001), but the effect of foot position was not significant.
Knee joint range of motion was acutely diminished in a stooping position. Thus, stretch tolerance was affected by manipulation of structures, which were not directly mechanically related to this joint. An influence from the nerve tissue complex must be considered to be a factor when describing the mechanisms behind altered stretch tolerance.
We will focus on spinal cord dorsal horn lamina I projection neurones, their supraspinal targets and involvement in pain processing. These spinal cord neurons respond to tonic peripheral inputs by wind-up and other intrinsic mechanisms that cause central hyper-excitability, which in turn can further enhance afferent inputs. We describe here another hierarchy of excitation - as inputs arrive in lamina I, neurones rapidly inform the parabrachial area (PBA) and periaqueductal grey (PAG), areas associated with the affective and autonomic responses to pain. In addition, PBA can connect to areas of the brainstem that send descending projections down to the spinal cord - establishing a loop. The serotonin receptor, 5HT3, in the spinal cord mediates excitatory descending inputs from the brainstem. These descending excitatory inputs are needed for the full coding of polymodal peripheral inputs from spinal neurons and are enhanced after nerve injury. Furthermore, activity in this serotonergic system can determine the actions of gabapentin (GBP) that is widely used in the treatment of neuropathic pain. Thus, a hierarchy of separate, but interacting excitatory systems exist at peripheral, spinal and supraspinal sites that all converge on spinal neurones. The reciprocal relations between pain, fear, anxiety and autonomic responses are likely to be subserved by these spinal-brainstem-spinal pathways we describe here. Understanding these pain pathways is a first step toward elucidating the complex links between pain and emotions.
Neural mechanisms contribute significantly to the gains that occur in the range of motion about a joint with stretching exercises. In the acute condition, lengthening of a muscle-tendon unit decreases spinal reflex excitability, which reduces passive tension and increases joint range of motion. Similarly, participation in a stretch-training program decreases tonic reflex activity and increases flexibility.
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