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Journal ArticleDOI

Acute effects of contract–relax (CR) stretch versus a modified CR technique

01 Mar 2016-European Journal of Applied Physiology (Springer Berlin Heidelberg)-Vol. 116, Iss: 3, pp 611-621

TL;DR: Similar mechanical and neurological changes were observed between conditions, indicating that identical mechanisms underpin the ROM improvements in CR and SRC, and have important practical implications for the use of this stretching mode in athletic environments.

AbstractContract–relax (CR) stretching increases range of motion (ROM) substantively, however its use in athletic environments is limited as the contractions performed in a highly stretched position require partner assistance, are often painful, and may induce muscle damage. Therefore, the acute effects of performing the contractions ‘off stretch’ in the anatomical position [stretch–return–contract (SRC)] were compared with traditional CR stretching in 14 healthy human volunteers. Passive ankle joint moment and dorsiflexion ROM were recorded on an isokinetic dynamometer with electromyographic monitoring of the triceps surae, whilst simultaneous real-time motion analysis and ultrasound imaging recorded gastrocnemius medialis muscle and Achilles tendon elongation. The subjects then performed CR or SRC stretches (4 × 10-s stretches and 5-s contractions) randomly on separate days before reassessment. Significant increases in dorsiflexion ROM (4.1°–4.0°; P   0.05). Similar mechanical and neurological changes were observed between conditions, indicating that identical mechanisms underpin the ROM improvements. These data have important practical implications for the use of this stretching mode in athletic environments as performing the contractions ‘off stretch’ eliminates the pain response, reduces the risk of inducing muscle damage, and removes the need for partner assistance. Thus, it represents an equally effective, simpler, and yet potentially safer, stretching paradigm.

Summary (4 min read)

Introduction

  • Contract-relax (CR) stretching increases range of motion (ROM) substantively, however its use in athletic environments is limited as the contractions performed in a highly stretched position require partner assistance, are often painful, and may induce muscle damage, also known as Purpose.
  • Regarding autogenic inhibition, a neuromuscular inhibition was thought to occur as the loading of the tendon during the contraction phase of CR activated/stimulated type Ib muscle afferent output from the golgi tendon organs, stimulating inhibitory spinal synapses and hyperpolarizing the dendritic ends of spinal α-motoneurons of the stretched muscle.
  • Furthermore, a recent study reported concomitant increases in ROM and reductions in tendon stiffness following isometric contractions performed in the anatomical position (Kay et al. 2015), with the acute increase in ROM being similar to that observed following static stretching.
  • Modification of the CR stretching technique to perform the muscle contraction phase with the muscle ‘off stretch’ may provide a similar stimulus whilst reducing injury risk.

Subjects

  • Fourteen recreationally active participants (8 women, 6 men; age = 26.1 ± (SD) 9.6 yr, height = 1.7 ± 0.1 m, and mass = 75.6 ± 13.3 kg) with no recent history of lower limb musculoskeletal injury or neurological deficit volunteered for the study after completing a pre-test medical questionnaire and giving written and informed consent.
  • The subjects were asked to avoid any flexibility training, intense exercise and stimulant use for 48 h prior to testing.
  • All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional research committee, and the study was completed in accordance with the Declaration of Helsinki.

Overview

  • The subjects were familiarized with the testing protocol one week prior to data collection and then visited the laboratory on two further occasions under experimental conditions, with trials counterbalanced and separated by one week.
  • During the experimental trials, the subjects performed a 5-min warm-up on a Monark cycle at 60 rpm with a 1-kg resistance load.
  • The ankle was then placed in the dynamometer footplate in the anatomical position (0°) with the lateral malleolus aligned to the centre of rotation of the dynamometer.
  • EMG amplitude was constantly monitored during the passive and active trials to quantify muscle activity (described later).
  • The probe was positioned with the proximal end towards the origin of the medial head and the distal end towards the insertion of the Achilles tendon.

Active and passive trials

  • During the active trial the subjects were instructed to perform a 5-s ramped maximal isometric plantar flexor contraction to determine maximal isometric strength, EMG activity, and tendon stiffness (described later).
  • Two minutes after completing the passive ROM trials the subjects performed either the CR or SRC stretching intervention.
  • Furthermore, this ensured that moment data were reflective of the passive properties of the MTC.
  • Upon contraction cessation, the ankle was then immediately rotated again at 0.087 rad·s-1 until reaching the point of discomfort with the protocol repeated three further times giving a total duration of 60 s (i.e. 4 ˟ 10-s stretches and 4 ˟ 5-s contractions).
  • Two minutes later the subjects repeated the passive and active trials (see Fig. 1).

Plantar flexor moment and ROM

  • Maximal isometric plantar flexor moment was recorded pre- and post-intervention during the active trial to determine the influence of CR and SRC stretching on isometric strength.
  • Peak isometric plantar flexor moment was also recorded during the four contractions performed during the CR and SRC interventions to determine the average peak loading during each intervention.
  • The passive rotation enabled ROM, peak passive moment (stretch tolerance), and the slope of the passive moment curve (indicative of MTC stiffness) to be recorded.
  • Joint moment and dorsiflexion angle data were directed from the dynamometer to a high level transducer (model HLT100C, Biopac, Goleta, CA) before analogue-to-digital conversion at a 2000-Hz sampling rate (model MP150 Data Acquisition, Biopac).
  • The data were then directed to a personal computer running AcqKnowledge software (v4.1, Biopac) and filtered with a zero lag, 6-Hz Butterworth low-pass filter.

Electromyographic (EMG) activity

  • EMG signals collected during maximal volitional contractions as well as during muscle stretches were then processed using a 20- to 500-Hz band-pass filter and converted to root-meansquared EMG with a moving symmetrical 250-ms averaging window.
  • The TTL pulse simultaneously placed a marker on the AcqKnowledge (v4.1, Biopac) software while ending the capture of motion analysis and ultrasound data.
  • Tendon length was calculated as the distance between reflective markers A and B (using motion analysis), plus the distance from the actual MTJ position to the distal edge of the image (using ultrasound) in a method identical to that previously reported (Kay et al. 2015).
  • Tendon stiffness was calculated as the change in plantar flexor moment from 50-90%MVC divided by the change in tendon length (Nm·mm-1).

Statistical analysis

  • All data were analyzed using SPSS statistical software (v.20; LEAD Technologies Inc., USA) and are reported as means and 95% confidence intervals (CI).
  • Normal distribution was assessed for pre- and post-group data using Kolmogorov-Smirnov and Shapiro-Wilk tests; no significant difference (P > 0.05) was detected in any variable indicating that all data sets were normally distributed.
  • Normal distribution was also examined for change score data in all variables using KolmogorovSmirnov and Shapiro-Wilk tests; a significant difference (P < 0.05) was detected for changes in peak passive moment in CR and SRC conditions and for ROM in the CR condition; no significant difference (P > 0.05) was detected in any other variable.
  • Spearman’s rank correlation coefficients (rs) were computed to quantify the linear relationship between the change in ROM and changes in peak passive moment (stretch tolerance) and the slope of the passive joint moment curve (MTC stiffness), muscle stiffness and tendon stiffness in each condition.
  • Statistical significance for all tests was accepted at P < 0.05.

Reliability

  • Test-retest reliability was determined for peak isometric moment, peak passive moment, ROM, the slope of the passive moment curve (MTC stiffness) and muscle and tendon stiffness in the pre-test data in both conditions.
  • Sample size Effect sizes (Cohen’s D) were calculated from mean changes in variables (ROM, muscle and tendon stiffness, and peak passive moment) from previous studies employing similar methods (Kay & Blazevich 2009b; Kay et al.
  • To ensure an adequate sample size was recruited for the study, power analyses were conducted using the following parameters (power = 0.80, alpha = 0.05, effect size = 1.0, attrition = 20%).

RESULTS

  • Significant correlations were observed between the changes in ROM and peak passive moment (stretch tolerance) in CR (rs = 0.63; P < 0.05) and SRC conditions (rs = 0.71; P < 0.05) indicating that changes in ROM were associated with changes in stretch tolerance after both interventions.
  • No difference in the reduction in MTC stiffness was found between conditions (P > 0.05), indicating a similar response after each condition.
  • These data are indicative that neuromuscular force generating capacity and reflexive muscle activity were neither inhibited nor potentiated after either condition.

DISCUSSION

  • Contract-relax (CR) stretching has been commonly cited as the optimal stretching mode for achieving acute increases in ROM (Funk et al. 2003; Hindle et al. 2012), although the underlying mechanisms responsible for the efficacy of CR stretching to increase ROM remain to be established.
  • Given that the muscle length adopted during the muscle contraction phase of CR stretching does not appear to influence the subsequent acute gain in ROM, nor the changes in mechanical or neuromuscular responses, the SRC technique may be useful for safely improving ROM when compared to the standard CR technique.
  • Reductions in tendon stiffness have been reported following maximal isometric contractions performed without stretch (Kay & Blazevich 2009b; Kubo et al. 2001), with concomitant increases in ROM being reported that are equivalent to the gains observed after static stretching (Kay et al. 2015).
  • These data are similar to those reported in previous acute CR studies where EMG magnitude was unchanged at full ROM (Kay et al.

CONCLUSIONS

  • In summary, a significant increase in ROM with reductions in both muscle and tendon stiffness and a concomitant increase in stretch tolerance were demonstrated after both CR and SRC stretching.
  • Furthermore, the changes in ROM were significantly correlated with changes in stretch tolerance but not changes in muscle, tendon, or whole MTC stiffness.
  • The present study is the first to examine the effect of performing the contraction phase of CR stretching with the muscle ‘off stretch’.
  • As no differences in the changes in any measure were evident between conditions, it is likely that similar mechanisms were responsible for the increases in ROM in CR and SRC conditions, regardless of the muscle length at which the contractions were performed.
  • These practical improvements may improve the capacity of individuals, coaches and clinicians to facilitate the use of this stretching mode as part of a complete injury prevention strategy in healthy and in at-risk populations in both athletic and clinical settings.

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1
TITLE
Acute effects of contract-relax (CR) stretch versus a modified CR technique
AUTHORS
Anthony D. Kay
1
, Steven Dods
1
& Anthony J. Blazevich
2
AFFILIATION
1
Sport, Exercise and Life Sciences, The University of Northampton, Northampton, United Kingdom
2
Centre for Exercise & Sport Science Research (CESSR), School of Exercise and Health Sciences, Edith Cowan
University, Joondalup, Australia
ADDRESS FOR CORRESPONDENCE
Anthony D. Kay
1
Sport, Exercise and Life Sciences
The University of Northampton
Boughton Green Road
Northampton
NN2 7AL
United Kingdom
Tel: 01604 892577
Fax: 01604 720636
tony.kay@northampton.ac.uk

2
ABSTRACT
Purpose: Contract-relax (CR) stretching increases range of motion (ROM) substantively, however its use in
athletic environments is limited as the contractions performed in a highly stretched position require partner
assistance, are often painful, and may induce muscle damage. Therefore, the acute effects of performing the
contractions ‘off stretch’ in the anatomical position (stretch-return-contract [SRC]) were compared with
traditional CR stretching in 14 healthy human volunteers. Methods: Passive ankle joint moment and dorsiflexion
ROM were recorded on an isokinetic dynamometer with electromyographic monitoring of the triceps surae, whilst
simultaneous real-time motion analysis and ultrasound imaging recorded gastrocnemius medialis muscle and
Achilles tendon elongation. The subjects then performed CR or SRC stretches (4 ˟ 10-s stretches and 5-s
contractions) randomly on separate days before reassessment. Results: Significant increases in dorsiflexion ROM
(4.1-4.0°; P<0.01) and peak passive moment (10.9-15.1%; P<0.05) and decreases in the slope of the passive
moment curve (19.1-13.3%; P<0.05), muscle stiffness (21.7-21.3%; P<0.01) and tendon stiffness (20.4-15.7%;
P<0.01) were observed in CR and SRC, respectively. No between-condition differences were found in any
measure (P>0.05). Conclusions: Similar mechanical and neurological changes were observed between
conditions, indicating that identical mechanisms underpin the ROM improvements. These data have important
practical implications for the use of this stretching mode in athletic environments as performing the contractions
‘off stretch’ eliminates the pain response, reduces the risk of inducing muscle damage, and removes the need for
partner assistance. Thus, it represents an equally effective, simpler, and yet potentially safer, stretching paradigm.
Keywords: Proprioceptive neuromuscular facilitation, range of motion, tendon stiffness, ultrasound.
INTRODUCTION

3
Both the maximal joint range of motion (ROM) and resistance to stretch during rotation (indicative of tissue
stiffness) are important functional parameters that may affect muscle strain injury risk (Witvrouw et al. 2003),
influence the capacity to perform activities of daily living (Mulholland et al. 2001), and are compromised with
aging (Bassey et al. 1989) and disease (Duffin et al. 1999). Static muscle stretching is a commonly used technique
to acutely improve ROM with these improvements thought to be attributable to several mechanisms, including
reductions in tissue stiffness (Kay et al. 2015; Morse et al. 2008), altered peripheral (afferent) output (Avela et al.
1999, 2004), and dampened pain, pressure or stretch perception increasing stretch tolerance (i.e. the capacity to
tolerate increased loading prior to terminating the stretch; Magnusson et al. 1996; Mitchell et al. 2007; Weppler
and Magnusson 2010). Despite the popularity of static stretching, proprioceptive neuromuscular facilitation
stretching (PNF) is regularly reported as being the most effective stretching technique for acute and chronic
improvements in ROM (Funk et al. 2003; Hindle et al. 2012). A common method of PNF stretching is the
contract-relax (CR) technique (Sharman et al. 2006), which includes a static stretching phase for a prescribed
duration, followed immediately by an intense, often maximal, isometric contraction performed in a fully stretched
position. Upon completion of the contraction the joint is rotated further to again stretch the target muscle, with
stretch intensity normally to the point of discomfort. While CR stretching is highly effective and often used in
clinical environments to achieve rapid increases in ROM, it is not commonly used in athletic warm-up routines
possibly because it normally requires an assisting partner, may be painful, and is thought to pose a greater muscle
strain injury risk compared with static stretching (Beaulieu 1981).
Few studies have examined the underlying mechanisms associated with increases in ROM following CR
stretching (Hindle et al. 2012; Kay et al. 2015), consequently these mechanisms remain essentially theoretical and
poorly understood. Two neuromuscular mechanisms (autogenic inhibition, gate control theory) have been
theorized (for review see Hindle et al. 2012). Regarding autogenic inhibition, a neuromuscular inhibition was
thought to occur as the loading of the tendon during the contraction phase of CR activated/stimulated type Ib
muscle afferent output from the golgi tendon organs, stimulating inhibitory spinal synapses and hyperpolarizing
the dendritic ends of spinal α-motoneurons of the stretched muscle. The Ib activity would likely diminish the
influence of homonymous Ia muscle afferents on the α-motoneuron pool of the stretched muscle, with the
diminished reflex activity thought to allow further increases in ROM (Prentice 1983). However, several original
studies have previously reported no change in electromyographic (EMG) magnitude at full ROM (Kay et al. 2015;
Mitchell et al. 2009; Osternig et al. 1990), with reviews concluding autogenic inhibition was unlikely to be an

4
important mechanism underpinning the increase in ROM following CR stretching (Hindle et al. 2012; Sharman
et al. 2006). Gate control theory posits that pressure receptors (type III afferents) activated during the contraction
phase could inhibit pain perception (Mazzullo 1978), as pressure receptors are associated with larger myelinated
neurons that connect to the same spinal interneurons as un-myelinated nociceptive fibers (type IV afferents) within
the spinal horn (Melzack 1993). The increased activity of pressure receptors would theoretically diminish the
influence of homonymous IV afferent output and pain perception, thus enabling further increases in ROM. While
these neuromuscular pathways are theoretical, increased stretch tolerance (dampened pain perception) is
commonly reported following CR stretching (Kay et al. 2015; Mitchell et al. 2009). Thus although autogenic
inhibition has largely been discounted, a neurological contribution to the increased ROM following CR stretching
is at least partly supported.
The distinct muscle-tendon (and joint) loading characteristics of various stretching methods likely result in
different mechanical responses, with a key distinction between CR and other stretching techniques being the
inclusion of an intense, often maximal, isometric contraction performed following the stretching phase and
performed with the muscle remaining in a highly-stretched position. During passive ankle dorsiflexion stretches,
more flexible subjects demonstrate greater tendon elongation with no detectable differences in the onset or
magnitude of muscle activity toward the end of rotation or near full ROM (Blazevich et al. 2014), therefore tendon
properties may, at least partly, influence maximum ROM. While muscular and tendinous tissues experience
deformation during stretching (Blazevich et al. 2014; Morse et al. 2008), studies employing ultrasonography
techniques have found muscle stiffness to be reduced after an acute bout of static stretching, whereas tendon
stiffness remained unaltered (Kay & Blazevich 2009a; Morse et al. 2008). However, a recent study revealed that
CR stretching acutely reduced both muscle and tendon stiffness and elicited significantly greater increases in
ROM compared with a similar volume of static stretching after which only a reduction in muscle stiffness was
induced (Kay et al. 2015). This broader acute adaptive response, where both muscle and tendon stiffness are
influenced concurrently, offers a potentially important mechanism underpinning the superior efficacy of CR
stretching for acutely increasing ROM when compared to other stretching techniques.
CR stretching is implemented to the aim of increasing ROM, often in an attempt to reduce muscle strain injury
risk. However, paradoxically, performing intense muscular contractions in a highly-stretched position, where the
muscle is vulnerable to injury, increases the risk of inducing tissue damage (Beaulieu 1981; Butterfield and Herzog

5
2006; Whitehead et al. 2003). Thus, the question should be asked whether the performance of isometric
contractions in a non-stretched position between each passive static stretching cycle is as effective as performing
the contractions during each passive static stretching cycle (i.e. contractions performed with the muscle in a
highly-stretched position). Interestingly, several studies have reported acute reductions in tendon stiffness
following maximal isometric contractions performed in the anatomical position (i.e. with the muscle off stretch;
Kay & Blazevich 2009b; Kay et al. 2015; Kubo et al. 2002). Furthermore, a recent study reported concomitant
increases in ROM and reductions in tendon stiffness following isometric contractions performed in the anatomical
position (Kay et al. 2015), with the acute increase in ROM being similar to that observed following static
stretching. Collectively, these findings suggest that substantial tendon loading, regardless of muscle length,
should influence tendon stiffness and ROM. Consequently, modification of the CR stretching technique to
perform the muscle contraction phase with the muscle ‘off stretch’ may provide a similar stimulus whilst reducing
injury risk. Therefore, the aims of the present study were to examine the influence of an acute bout of CR
stretching versus a modified CR technique (stretch-return-contract [SRC]; where the contractions are performed
off stretch’) on dorsiflexion ROM, maximal passive joint moment at full volitional ROM (stretch tolerance), the
slope of the passive moment curve (indicative of whole muscle-tendon complex [MTC] stiffness), gastrocnemius
medialis (GM) muscle stiffness and triceps surae EMG activity (measured during a passive joint stretch). The
acute effects of these interventions on Achilles tendon stiffness, maximal isometric plantar flexor joint moment
and peak triceps surae EMG activity during a maximal isometric contraction were then measured. We tested the
hypothesis that CR and SRC stretching techniques would produce similar increases in ROM and stretch tolerance
whilst reducing muscle and tendon stiffness.
METHODS
Subjects
Fourteen recreationally active participants (8 women, 6 men; age = 26.1 ± (SD) 9.6 yr, height = 1.7 ± 0.1 m, and
mass = 75.6 ± 13.3 kg) with no recent history of lower limb musculoskeletal injury or neurological deficit
volunteered for the study after completing a pre-test medical questionnaire and giving written and informed
consent. The subjects were asked to avoid any flexibility training, intense exercise and stimulant use for 48 h
prior to testing. All procedures performed in studies involving human participants were in accordance with the
ethical standards of the institutional research committee, and the study was completed in accordance with the
Declaration of Helsinki.

Figures (4)
Citations
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Journal ArticleDOI
TL;DR: While 120 s SS per muscle increased ROM, even within a comprehensive warm-up routine, it also elicited notable performance decrements and moderate durations of SS were observed to improve ROM whilst either having negligible or beneficial (but not detrimental) effects on specific aspects of athletic performance.
Abstract: Evidence for performance decrements following prolonged static stretching (SS) has led to a paradigm shift in stretching routines within a warm-up. Rather than SS, dynamic stretching (DS) and dynamic activity (DA) have replaced SS within warm-up routines. The objective of the present study was to compare the effect of differing lower limb SS durations (30 [SS30s], 60 [SS60s] or 120 s [SS120s] of SS per muscle group or no-stretch control) within a comprehensive warm-up protocol consisting of aerobic activity, DS and DA. Sixteen male participants completed the four stretching conditions in a randomized order, after a 5-min low-intensity (cycle) warm-up and before a DS/DA component on separate days. Tests included passive hip and knee ranges of motion (ROM), maximum voluntary knee extensor/flexor force, force produced at 100 ms (F100), vertical jump height and evoked knee extensor contractile properties. For hip flexion (hamstrings) ROM, SS120s provided the largest increase (5.6–11.7%) followed by SS60s (4.3–11.4%), control (4.4–10.6%) and SS30s (3.6–11.1%). For knee flexion (quadriceps) ROM, SS30s provided the largest increase (9.3–18.2%) followed by SS120s (6.5–16.3%), SS60s (7.2–15.2%) and control (6.3–15.2%). There were decreases in quadriceps F100 following SS in SS120s (29.6%) only. There were increases in vertical jump performance in the control (6.2%), SS60s (4.6%) and SS30s (3.3%). While 120 s SS per muscle increased ROM, even within a comprehensive warm-up routine, it also elicited notable performance decrements. However, moderate durations of SS were observed to improve ROM whilst either having negligible or beneficial (but not detrimental) effects on specific aspects of athletic performance.

38 citations


Journal ArticleDOI
TL;DR: Moderate-quality evidence shows that results differ between self HR and control in terms of ROM gain, and does not allow to state if PNF is more or less effective than other stretches for improving ROM in healthy young adults.
Abstract: The objective of this study was to evaluate the efficacy of proprioceptive neuromuscular facilitation (PNF) on range of motion (ROM) gain in young healthy adults. We performed a systematic review of randomized controlled trials and quasi-randomized trials, including young healthy adults. The interventions were: PNF compared with different PNF techniques, control, other muscle stretching exercises and musculoskeletal manipulations. The outcome measures were: articular ROM and adverse effects. The final number of included studies was 46, involving 1,864 adults. There was difference on ROM comparing assisted hold-relax (HR) on diagonal plane to control, based on very low-quality evidence. There was also difference on ROM comparing assisted HR to self-HR; self-contract-relax (CR) to control; assisted CR contract to control; and assisted HR contract to control, based on low-quality evidence. Moderate-quality evidence shows that results differ between self HR and control (SMD: 0.95; 95%CI 0.03, 1.86; I2...

9 citations


Cites background or methods from "Acute effects of contract–relax (CR..."

  • ...Furthermore, in 17 trials (Chen et al, 2009; Decicco and Fisher, 2005; Kay, Dods, and Blazevich, 2016; Kay, Husbands-Beasley, and Blazevich, 2015; Mallmann et al, 2011; Minshull et al, 2014; Mitchell et al, 2007; Moesch et al, 2014; Place et al, 2013; Puentedura et al, 2011; Rees et al, 2007;…...

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  • ...Kay, Dods, and Blazevich (2016) G1: 6 men; 8 women; G2: 6 men; 8 women....

    [...]

  • ...Hamstring (both sides) Supine 5/wk, 8 wk Not stated Kay, Dods, and Blazevich (2016) G1: 4x assisted CR PNF(10 s SS; 5 s isometric contraction; total 60 s); G2: 4x assisted CRC PNF (10 s SS; 5 s isometric contraction; 10 s interval; 5 s isometric contraction; total 60 s)....

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  • ...Kay, Dods, and Blazevich (2016) Pre–post-test Passive ankle dorsiflexion (isokinetic dynamometer) G1: MD 4.1°(CI 2.6–5.6); G2: 4°(2–6)....

    [...]

  • ...In this context, only six studies (Alcântara, Firmino, and Lage, 2010; Beltrão, Ritti-Dias, Pitangui, and De Araújo, 2014; Demoulin et al, 2016; Kay, Dods, and Blazevich, 2016; Kay, Husbands-Beasley, and Blazevich, 2015; Konrad, Gad, and Tilp, 2015) performed a sample calculation, evidencing that…...

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Journal ArticleDOI
TL;DR: The results suggest that a higher intensity of the static stretching should be conducted to increase ROM and decrease muscle stiffness, even for a short time.
Abstract: This study investigated the effects of static stretching (SS) delivered with the same load but using two protocols - high-intensity and short-duration and low-intensity and long-duration - on range of motion (ROM) and muscle stiffness. A total of 18 healthy students participated in the study. They randomly performed high-intensity and short-duration (120% and 100 s) or low-intensity and long-duration (50% and 240 s) SS. Outcomes were assessed on ROM, passive torque at dorsiflexion ROM, and shear elastic modulus of the medial gastrocnemius before and after static stretching. The results showed that ROM increased significantly at post-stretching compared to that at pre-stretching in both high-intensity and short-duration [+6.1° ± 4.6° (Δ25.7 ± 19.9%)] and low-intensity and long-duration [+3.6° ± 2.3° (Δ16.0 ± 11.8%)]. Also, the ROM was significantly higher at post-stretching in high-intensity and short-duration conditions than that in low-intensity and long-duration. The passive torque at dorsiflexion ROM was significantly increased in both high-intensity and short-duration [+5.8 ± 12.8 Nm (Δ22.9 ± 40.5%)] and low-intensity and long-duration [+2.1 ± 3.4 Nm (Δ6.9 ± 10.8%)] conditions, but no significant differences were observed between both conditions. The shear elastic modulus was significantly decreased in both high-intensity and short-duration [-8.8 ± 6.1 kPa (Δ - 38.8 ± 14.5%)] and low-intensity and long-duration [-8.0 ± 12.8 kPa (Δ - 22.2 ± 33.8%)] conditions. Moreover, the relative change in shear elastic modulus in the high-intensity and short-duration SS was significantly greater than that in low-intensity and long-duration SS. Our results suggest that a higher intensity of the static stretching should be conducted to increase ROM and decrease muscle stiffness, even for a short time.

7 citations



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Abstract: Introduction Congenital dysplasia of the pelvis often occurs in isolation, however, it can also involve other pelvic components, and anomalies of the digestive system. Pelvic malformations have effects on the pelvic girdle and pelvic stability influencing the quality of gait. The condition can be treated with a total hip arthroplasty (THA). The concept of Proprioceptive Neuromuscular Facilitation (PNF) has been described as a comprehensive rehabilitation approach with a focus on motor learning. This case report seeks to illustrate the clinical reasoning and feasibility of applying the PNF-concept in a patient after a THA with multiple congenital pelvis malformations. Case description A male, 44 years of age, physically active laborer was treated with THA after hip dysplasia, with comorbid missing pubic symphysis. The patient presented with complaints in gait speed, gait distance, hip joint mobility and stability. Patient management PNF-based motor-control training, including specified PNF-pattern exercises with specific PNF-facilitation principles and techniques was provided over a period of eighteen weeks. Results showed improvements beyond the minimal detectable change and/or the minimal clinically important difference for physical functioning in gait, strength, range of motion, and personal required activities. Discussion and conclusion Gait rehabilitation training, restoring altered movement patterns in the patient's activities of daily living was provided with PNF. Besides targeting structural impairments, this approach elicited motor learning effects. PNF-patterns have been described as: "mimicking functional activities" from daily life and sports. A specified PNF-based therapy including motor learning components, was a feasible approach in this case of complex pelvic skeletal malformations.

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TL;DR: Results indicate that soccer players with an increased tightness of the hamstring or quadriceps muscles have a statistically higher risk for a subsequent musculoskeletal lesion.
Abstract: Background: Muscular tightness is frequently postulated as an intrinsic risk factor for the development of a muscle injury. However, very little prospective data exist to prove this.Hypothesis: Increased muscle tightness identifies a soccer player at risk for a subsequent musculoskeletal lesion.Study Design: Prospective cohort study.Methods: We examined 146 male professional soccer players before the 1999—2000 Belgian soccer competition. None of the players had a history of muscle injury in the lower extremities in the previous 2 years. The flexibility of the hamstring, quadriceps, adductor, and calf muscles of these players was measured goniometrically before the start of the season. All of the examined players were monitored throughout the season to register subsequent injuries.Results: Players with a hamstring (N = 31) or quadriceps (N = 13) muscle injury were found to have significantly lower flexibility in these muscles before their injury compared with the uninjured group. No significant differences...

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"Acute effects of contract–relax (CR..." refers background in this paper

  • ...…to stretch during rotation (indicative of tissue stiffness) are important functional parameters that may affect muscle strain injury risk (Witvrouw et al. 2003), influence the capacity to perform activities of daily living (Mulholland and Wyss 2001), and are compromised with aging…...

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  • ...Both the maximal joint range of motion (ROM) and resistance to stretch during rotation (indicative of tissue stiffness) are important functional parameters that may affect muscle strain injury risk (Witvrouw et al. 2003), influence the capacity to perform activities of daily living (Mulholland and Wyss 2001), and are compromised with aging (Bassey et al....

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481 citations


"Acute effects of contract–relax (CR..." refers background or methods in this paper

  • ...The subjects were then seated in the chair of an isokinetic dynamometer (Biodex System 3 Pro, IPRS, Suffolk, UK) with the hip flexed to 55° and knee fully extended (0°) to ensure all plantar flexor muscles could be strongly activated and were at an appropriate length to contribute strongly to the total passive and active joint moments (Cresswell et al. 1995; Kawakami et al. 1998)....

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  • ...…3 Pro, IPRS, Suffolk, UK) with the hip flexed to 55° and knee fully extended (0°) to ensure all plantar flexor muscles could be strongly activated and were at an appropriate length to contribute strongly to the total passive and active joint moments (Cresswell et al. 1995; Kawakami et al. 1998)....

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Journal ArticleDOI
TL;DR: It is concluded that reflex EMG activity does not limit the range of movement during slow stretches and that the increased range of motion achieved from training is a consequence of increased stretch tolerance on the part of the subject rather than a change in the mechanical or viscoelastic properties of the muscle.
Abstract: 1. We investigated the effect of a long-term stretching regimen on the tissue properties and stretch tolerance of human skeletal muscle. 2. Resistance to stretch was measured as torque (in N m) offered by the hamstring muscle group during passive knee extension while electromyographic (EMG) activity, knee joint angle and velocity were continuously monitored during a standardized stretch manoeuvre. Seven healthy subjects were tested before and after a 3 week training period using two separate protocols. Protocol 1 consisted of a slow stretch at 0.087 rad s-1 to a predetermined angle followed by a 90 s holding phase. Subjects were brought to the same angle before and after the training period. Protocol 2 was a similar stretch, but continued to the point of pain. 3. During protocol 1 the torque rose during the stretch and then declined during the holding phase. EMG activity was small and did not change significantly during the protocol. No significant differences in stiffness, energy and peak torque about the knee joint were seen as a result of the training. During protocol 2 the angle to which the knee could be extended was significantly increased as a result of the training. This was accompanied by a comparable increase in peak torque and energy. EMG activity was small and not affected by training. 4. It is concluded that reflex EMG activity does not limit the range of movement during slow stretches and that the increased range of motion achieved from training is a consequence of increased stretch tolerance on the part of the subject rather than a change in the mechanical or viscoelastic properties of the muscle.

375 citations


"Acute effects of contract–relax (CR..." refers background or methods in this paper

  • ...…peripheral (afferent) output (Avela et al. 1999, 2004), and dampened pain, pressure or stretch perception increasing stretch tolerance (i.e., the capacity to tolerate increased loading prior to terminating the stretch; Magnusson et al. 1996; Mitchell et al. 2007; Weppler and Magnusson 2010)....

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  • ...Effect sizes (Cohen’s D) were calculated from mean changes in variables (ROM, muscle and tendon stiffness, and peak passive moment) from previous studies employing similar methods (Kay and Blazevich 2009b; Kay et al. 2015; Kubo et al. 2002; Magnusson et al. 1996)....

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  • ...1999, 2004), and dampened pain, pressure or stretch perception increasing stretch tolerance (i.e., the capacity to tolerate increased loading prior to terminating the stretch; Magnusson et al. 1996; Mitchell et al. 2007; Weppler and Magnusson 2010)....

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Journal ArticleDOI
TL;DR: Passive stretching was commonly used to increase limb range of movement prior to athletic performance but it is unclear which component of the muscle–tendon unit (MTU) is affected by this procedure but post‐conditioning this was not the case suggesting that at least part of the change in muscle with conditioning stretches was due to altered properties of connective tissue.
Abstract: Passive stretching is commonly used to increase limb range of movement prior to athletic performance but it is unclear which component of the muscle-tendon unit (MTU) is affected by this procedure. Movement of the myotendinous junction (MTJ) of the gastrocnemius medialis muscle was measured by ultrasonography in eight male participants (20.5 +/- 0.9 years) during a standard stretch in which the ankle was passively dorsiflexed at 1 deg s(-1) from 0 deg (the foot at right angles to the tibia) to the participants' volitional end range of motion (ROM). Passive torque, muscle fascicle length and pennation angle were also measured. Standard stretch measurements were made before (pre-) and after (post-) five passive conditioning stretches. During each conditioning stretch the MTU was taken to the end ROM and held for 1 min. Pre-conditioning the extension of the MTU during stretch was taken up almost equally by muscle and tendon. Following conditioning, ROM increased by 4.6 +/- 1.5 deg (17%) and the passive stiffness of the MTU was reduced (between 20 and 25 deg) by 47% from 16.0 +/- 3.6 to 10.2 +/- 2.0 Nm deg(-1). Distal MTJ displacement (between 0 and 25 deg) increased from 0.92 +/- 0.06 to 1.16 +/- 0.05 cm, accounting for all the additional MTU elongation and indicating that there was no change in tendon properties. Muscle extension pre-conditioning was explicable by change in length and pennation angle of the fascicles but post-conditioning this was not the case suggesting that at least part of the change in muscle with conditioning stretches was due to altered properties of connective tissue.

349 citations


"Acute effects of contract–relax (CR..." refers background or methods or result in this paper

  • ...Importantly, both CR and SRC stretching techniques cause an acute reduction in muscle and tendon stiffness, and this broader adaptive response may be an important adaptation that underpins the superior efficacy of CR stretching to acutely increase ROM compared with static stretching, which only influences muscle properties (Kay and Blazevich 2009a; Morse et al. 2008)....

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  • ...…improve ROM with these improvements thought to be attributable to several mechanisms, including reductions in tissue stiffness (Kay et al. 2015; Morse et al. 2008), altered peripheral (afferent) output (Avela et al. 1999, 2004), and dampened pain, pressure or stretch perception increasing…...

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  • ...Consistent with previous findings (Kay and Blazevich 2009a; Morse et al. 2008), the ultrasonography data in the present study revealed a reduced GM muscle stiffness Fig....

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  • ...2008), studies employing ultrasonography techniques have found muscle stiffness to be reduced after an acute bout of static stretching, whereas tendon stiffness remained unaltered (Kay and Blazevich 2009a; Morse et al. 2008)....

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  • ...The relative stiffness, and consequently the deformation, of muscle and tendon are distinct during low-velocity passive joint rotations towards maximal ROM (Blazevich et al. 2014; Morse et al. 2008), however the energy transfer through the tendon and muscle are identical as these tissues are arranged in series....

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