Time course of stress relaxation and recovery in human ankles

doi:10.1016/S0268-0033(01)00043-2

Clinical Biomechanics

Volume 16, Issue 7, August 2001, Pages 601-607

https://doi.org/10.1016/S0268-0033(01)00043-2 Get rights and content

Abstract

Objective. To characterise the time course of stress relaxation and recovery from stress relaxation in human ankles.

Design. Two experiments were conducted. The first used a randomised within-subjects design, and the second used a randomised between-subjects regression design.

Background. Several studies have described the time course of stress relaxation in human joints, but most have looked only at the effects of short durations of stretch. The time course of recovery from stretch in human ankles has not been documented.

Methods. In the first experiment, one ankle of each of eight subjects was stretched to a fixed dorsiflexion angle for 20 min. The ankle was then released for 2 min (during which time subjects either remained relaxed or performed isometric contractions), then stretched again. In a second experiment, on 24 subjects, the ankle was stretched for 20 min, then released between 0 and 20 min, then stretched again. In both experiments, subjects remain relaxed and ankle torque was measured continuously.

Results. When a constant-angle stretch was applied to the ankle, torque declined bi-exponentially towards an asymptote that was 58% of the initial torque. Nearly 5 min of stretch were required to obtain half of the maximal possible stress relaxation. Torque had recovered by 43% within 2 min of the release of stretch, but the degree of recovery did not appear to depend on whether subjects remained relaxed or performed isometric contractions. The time course of recovery was similar to the time course of stress relaxation.

Conclusions. Long duration stretches are required to produce a large proportion of the maximal possible stress relaxation. Recovery is initially rapid when the stretch is released.
Relevance

These data provide a description of the time course of the effects of stretch, and of the subsequent relief of stretch, on mechanical properties of human ankles.

Introduction

When soft tissues are stretched for a period of seconds or minutes they undergo progressive deformation, so that they can then be extended further with a constant force (“creep”) or exert less force when stretched to a constant length (“stress relaxation”) [1]. In everyday parlance, stretching is said to make the tissues more flexible. This property is exploited by clinicians and athletes when they stretch muscles and joints.

A number of studies have examined the time course of the effects of stretching [2], [3], [4], [5], because it has been thought that this might enable recommendations to be made concerning optimal stretch duration. In a frequently cited study, Madding and colleagues [5] found no significant difference between the effects of hip adductor stretches of 15, 45 s or 2 min duration. They suggested that it is reasonable to stretch muscles for only 15 s when immediate increases in the range of motion are desired. However, in most tissues the effects of stretching continue indefinitely, albeit at a diminishing rate [6], [7]. Madding et al.'s study may have detected further effects of stretching at 2 min if it utilised a larger sample or a design that provided greater statistical precision.

The Madding study investigated the time course of stretching by allocating subjects to groups that were stretched for different durations. A better way to examine the time course of the effects of stretching is to monitor the time course of stretch on each individual, either by stretching tissues to a constant torque and continuously measuring joint angle (i.e., monitor creep), or by stretching tissues to a constant-angle and continuously measuring torque (i.e., monitor stress relaxation). Toft and colleagues [8] showed that when the ankle was stretched to a constant dorsiflexion angle, torque initially declined rapidly and thereafter declined linearly with the logarithm of time. These authors monitored the stress relaxation for 5 min, at which time passive torque was still declining significantly.

The purpose of the present study is to extend these observations to the time course of stress relaxation in the human ankle. We sought to apply a dorsiflexion stretch to the ankle long enough to be able to confidently predict the effects of a hypothetical stretch of infinite duration. This would make it possible to describe the effects of short duration stretches in terms of a proportion of the greatest possible effect of stretching.

In vivo studies on isolated tissues and studies on human joints show that stress relaxation is a reversible phenomenon [9], [10], [11], [12]. That is, when the stretch is released, the degree of stress sustained at any length slowly returns to pre-stretch values. Few studies have examined the time course of recovery from sustained stretch in humans [13] and none, to our knowledge, have examined the time course of recovery of stress relaxation. Therefore, a second purpose of the present study was to make a preliminary investigation of the time course of recovery from stretch. To do this, we examined the degree of recovery that occurred when a 20-min stretch was released for 2 min. As the mechanical properties of resting skeletal muscle depend on the muscle's contraction history (“thixotropy”), [14], [15], we also investigated whether the degree of recovery from a stretch to the ankle is influenced by muscle contraction during the recovery period.

A second experiment examined the time course of recovery in more detail. The purpose was to determine how much recovery occurred at any time following removal of the stretch. In this experiment we manipulated the duration of the recovery period following a 20-min stretch.

Section snippets

Experiment 1

Subjects. Eight healthy university students volunteered to participate in the first experiment. There were seven females and one male with a mean age of 21.0 years (SD 0.82). None had a history of major musculoskeletal trauma to the ankle.

Procedures. All procedures were approved by the institutional ethics committee. Subjects were required to attend the laboratory on four separate days. On each day the ankle was stretched to a fixed dorsiflexion angle for 20 min. There was then a 2-min recovery

Experiment 1

The initial ankle angles attained when a “strong but not painful” stretch was applied varied considerably between-subjects (range 101–125°, mean 114°, SD 8°).

Time course of stress relaxation. A representative stress relaxation profile is shown in Fig. 2. The time course of stress relaxation was closely fitted by a double exponential function of the form $T=A+B e^{−t/τ^{1}} +C e^{−t/τ^{2}},$ where T is the torque (N m) and t is the stretch time (s). $A, B, C, τ_{1}$ and τ₂ are the constants obtained from the non-linear

Discussion

In experiment 1, subjects in the relax-long condition received an uninterrupted 42-min stretch to the ankle. Over this period, passive ankle torque declined to within 8% of the final value anticipated had the double exponential decline continued indefinitely. This made it possible to accurately characterise most of the time course of stress relaxation. The main findings were that torque declines as a double exponential function, and the time course of this decline is slow. For example, it takes

References (23)

E. Toft et al.
Biomechanical properties of the human ankle in relation to passive stretch
J Biomech
(1989)
R.F. Kirsch et al.
Effect of maintained stretch on the range of motion of the human ankle joint
Clin Biomech
(1995)
M. Solomonow et al.
Biexponential recovery model of lumbar viscoelastic laxity and reflexive muscular activity after prolonged cyclic loading
Clin Biomech
(2000)
S.M. McGill et al.
Creep response of the lumber spine to prolonged full flexion
Clin Biomech
(1992)
M.T. Jahnke et al.
Measurements of muscle stiffness, the electromyogram and activity in single muscle spindles of human flexor muscles following conditioning by passive stretch or contraction
Brain Res
(1989)
D. Taylor et al.
Viscoelastic properties of muscle-tendon units. The biomechanical effects of stretching
Am J Sports Med
(1989)
W.Y. Loebl
The assessment of mobility of metacarpaophalangeal joints
Rheum Phys Med
(1972)
M.P. McHugh et al.
Viscoelastic stress relaxation in human skeletal muscle
Med Sci Sports Exerc
(1992)
S.W. Madding et al.
Effect of duration of passive stretch on hip abduction range of motion
J Orthop Sports Phys Ther
(1987)
Y.C.B. Fung
Elasticity of soft tissues in simple elongation
Am J Physiol
(1967)

A. Viidik

Mechanical properties of parallel-fibred collagenous tissues

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Effect of chronic stretching interventions on the mechanical properties of muscles in patients with stroke: A systematic review
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Second, measurement of the force applied may help increase the effectiveness of interventions by ensuring that sufficient force is applied and to progress the stretch. This will ensure a “true” stretching effect, beyond the muscle relaxation that occurs during positioning, after only a few minutes [14]. Therefore, measuring the mechanical load that is applied during stretching helps in standardizing both the assessment and the dosage of the intervention, according to the stress–strain principle.
Muscle contractures are common after stroke and their treatment usually involves stretching. However, recent meta-analyses concluded that stretching does not increase passive joint amplitudes in patients with stroke. The effectiveness of treatment is usually evaluated by measuring range of motion alone; however, assessing the effects of stretching on the structural and mechanical properties of muscle by evaluating the torque-angle relationship can help in understanding the effects of stretching. Although several studies have evaluated this, the effects remain unclear.
A systematic review of the literature on the effectiveness of stretching procedures for which the outcomes included a measurement of torque associated with range of motion or muscle structure (e.g., fascicle length) in stroke survivors.
PubMed, ScienceDirect and PEDro databases were searched by 2 independent reviewers for relevant studies on the effects of chronic stretching interventions (> 4 weeks) that evaluated joint angle and passive torque or muscle structure or stiffness. The quality of the studies was assessed with the PEDro scale.
Eight randomized clinical trials (total of 290 participants) met the inclusion criteria, with highly variable sample characteristics (at risk/existing contractures), program objectives (prevent/treat contractures) and duration (from 4 to 52 weeks) and volume of stretching (1 to 586 hr). All studies were classified as high quality (> 6/10 PEDro score). Six studies focused on the upper limb. Many programs were less than 12 weeks (n = 7 studies) and did not change mechanical/structural properties. The longest intervention (52 weeks) increased muscle fascicle length and thickness (plantar flexors).
Long interventions involving high stretching volumes and/or loads may have effects on muscle/joint mechanical properties, for preventing/treating contractures after stroke injury, but need to be further explored before firm conclusions are drawn.
Effect of static stretching with different rest intervals on muscle stiffness
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Stress relaxation is reported as a phenomena caused by SS, which corresponds to a gradual decline in the passive force on the muscle during stretching at a constant angle (Taylor et al., 1990). In a manner similar to the gradual declines in passive force during SS, it is known that the muscle force also gradually recovers after the muscle is released from stretching (Duong et al., 2001). Duong et al., (2001) reported that the decrease in force due to 20-min SS recovered 2 min after SS by approximately 43%.
The aim of the study was to investigate the effect of static stretching (SS) with different rest intervals on muscle stiffness. Fifteen healthy males participated in the study. Four bouts of thirty-second SS for the gastrocnemii were performed at the maximal dorsiflexion using dynamometer with two different rest intervals between stretches, namely 0 s (R0) and 30 s (R30). Each participant underwent both stretching protocols at least 48 h apart in a random order. Between each bout of SS, the ankle was moved to 20°-plantar-flexion in 3 s, held for each rest interval time, and then returned to the stretching position in 3 s. The shear elastic modulus of the medial gastrocnemius was measured before (PRE) and immediately after (POST) four bouts of SS to assess muscle stiffness of the medial gastrocnemius. Two-way repeated measures analysis of variance (protocol × time) indicated a significant interaction effect on the shear elastic modulus. The shear elastic modulus significantly decreased after SS in both protocols [R0, PRE: 11.5 ± 3.3 kPa, POST: 10.0 ± 2.6 kPa, amount of change: 1.6 ± 0.9 kPa (13.0 ± 5.2%); R30, PRE: 11.0 ± 2.8 kPa, POST: 10.2 ± 2.1 kPa, amount of change: 0.8 ± 1.3 kPa (6.0 ± 10.4%)]. Furthermore, the SS with 0-s rest interval induced greater decrease in shear elastic modulus when compared to SS with 30-s rest interval (p = 0.023). Thus, when performing SS to decrease muscle stiffness, rest intervals between stretches should be minimized.
Stretch-induced changes in tension generation process and stiffness are not accompanied by alterations in muscle architecture of the middle and distal portions of the two gastrocnemii
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Recent studies showed that pre-exercise SS may negatively affect maximum force and power output (Behm et al., 2004; La Torre et al., 2010; Limonta et al., 2012, 2013; Rubini et al., 2007; Simic et al., 2013), which are highly dependent on neuromuscular activation and muscle mass, composition and architecture. This acute response to SS has been related to both neural and mechanical factors, among which a reduction in the neural drive (Avela et al., 2004; Cè et al., 2008a,b; Guissard et al., 1988, 1989) and a decrease in the muscle–tendon unit (MTU) stiffness (Duong et al., 2001; Fowles et al., 2000; Herda et al., 2011; Magnusson et al., 1995; Nordez et al., 2008; Ryan et al., 2011), which leads to an alteration in the passive tension-length relationship (Taylor et al., 1990). While the stretch-induced reduction in neural drive has been ascribed to changes in pre- and post-synaptic circuits at spinal level (Avela et al., 2004; Chalmers, 2004; Guissard et al., 1988, 1989, 2001), the alteration in MTU stiffness has been attributed to changes in the viscoelastic properties of the tissues, such as an increased extensibility of the tendon (Kato et al., 1985; Kubo et al., 2001a,b) and muscular components (aponeuroses, contractile and connective tissues) (Morse et al., 2008).
The study aimed to evaluate the stretch-induced changes in muscle architecture in different portions of the gastrocnemius medialis (GM) and lateralis (GL) muscles. The reliability and sensitivity of the measurements were also assessed. Fascicle length (FL) and pennation angle (PA) were calculated in the middle and distal portions of GM and GL at 0°, 10° and 20° of ankle dorsiflexion. At the same angles, passive torque (T_pass), peak torque (pT) and myotendinous junction displacement of GM were determined. Stiffness was calculated at muscle–tendon unit (MTU), muscle and tendon level. After static stretching administration, T_pass, pT and MTU stiffness decreased by 22%, 12% and 16%, respectively (p < 0.05). Muscle and tendon stiffness decreased by 15% and 16% (p < 0.05). Nevertheless, no changes in FL and PA occurred. The reliability of the approach was always very high (intraclass correlation coefficient > 0.90), with an adequate level of sensitivity. pT after static stretching was related to decreases in MTU, muscle and tendon stiffness, but not to alterations in muscle architecture.
Relationship between viscosity of the ankle joint complex and functional ankle instability for inversion ankle sprain patients
2015, Journal of Science and Medicine in Sport
Measurement of viscosity of the ankle joint complex is a novel method to assess mechanical ankle instability. In order to further investigate the clinical significance of the method, this study intended to investigate the relationship between ankle viscosity and severity of functional ankle instability.
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15 participants with unilateral inversion ankle sprain and 15 controls were recruited. Their ankles were further classified into stable and unstable ankles. Ankle viscosity was measured by an instrumental anterior drawer test. Severity of functional ankle instability was measured by the Cumberland Ankle Instability Tool. Unstable ankles were compared with stable ankles. Injured ankles were compared with uninjured ankles of both groups. The spearman's rank correlation coefficient was applied to determine the relationship between ankle viscosity and severity of functional ankle instability in unstable ankles.
There was a moderate relationship between ankle viscosity and severity of functional ankle instability (r = −0.64, p < 0.0001). Unstable ankles exhibited significantly lower viscosity (p < 0.005) and more severe functional ankle instability (p < 0.0001) than stable ankles. Injured ankles exhibited significantly lower viscosity and more severe functional ankle instability than uninjured ankles (p < 0.0001).
There was a moderate relationship between ankle viscosity and severity of functional ankle instability. This finding suggested that, severity of functional ankle instability may be partially attributed to mechanical insufficiencies such as the degenerative changes in ankle viscosity following the inversion ankle sprain. In clinical application, measurement of ankle viscosity could be a useful tool to evaluate severity of chronic ankle instability.
Time course of changes in passive properties of the gastrocnemius muscle-tendon unit during 5 min of static stretching
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Recently, noninvasive methods of measuring the passive properties of muscles and tendons, such as myotendinous junction (MTJ) displacement, have been developed using ultrasonography during passive movement (Morse et al., 2008; Kay and Blazevich, 2009a, 2009b, 2010; Mizuno et al., in press; Morse, 2011; Morse et al., 2008; Nakamura et al., 2011, 2012). Many studies have examined the acute effects of SS on passive torque and MTU stiffness, which is an indicator of MTU resistance, using a dynamometer and have reported that SS of various durations (1–42 min) (Magnusson et al., 1996b; Fowles et al., 2000; Duong et al., 2001; Nordez et al., 2006, 2008; Morse et al., 2008; Ryan et al., 2008a; Ryan et al., 2009; Herda et al., 2009, 2011; Ryan et al., 2009) resulted in decreased passive torque or decreased MTU stiffness. On the other hand, Halbertsma et al. (1996) reported that maximum ROM increased immediately after 5 min of SS, but no changes were observed in MTU stiffness.
The minimum time required for Static stretching (SS) to change the passive properties of the muscle–tendon unit (MTU), as well as the association between these passive properties, remains unclear. This study investigated the time course of changes in the passive properties of gastrocnemius MTU during 5 min of SS.
The subjects comprised 20 healthy males (22.0 ± 1.8 years). Passive torque as an index of MTU resistance and myotendinous junction (MTJ) displacement as an index of muscle extensibility were assessed using ultrasonography and dynamometer during 5 min of SS. Significant differences before and every 1 min during SS were determined using Scheffé’s post hoc test. Relationships between passive torque and MTJ displacement for each subject were determined using Pearson's product–moment correlation coefficient.
Although gradual changes in both passive torque and MTJ displacement were demonstrated over every minute, these changes became statistically significant after 2, 3, 4, and 5 min of SS compared with the values before SS. In addition, passive torque after 5 min SS was significantly lower than that after 2 min SS. Similarly, MTJ displacement after 5 min SS was significantly higher than that after 2 min SS. A strong correlation was observed between passive torque and MTJ displacement for each subject (r = −0.886 to −0.991).
These results suggest that SS for more than 2 min effectively increases muscle extensibility, which in turn decreases MTU resistance.
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Counterbalancing [using a random numbers table] was used to minimise the possibility of order effects, as subjects participated in two conditions. In order to provide sufficient time for the restoration of the baseline physical properties of the hamstring muscle between interventions, testing days were separated by 48 h (DePino et al., 2000; Duong et al., 2001). All subjects received verbal and written information about the study and gave written informed consent prior to testing.
The growing evidence suggests that physiological mobilisation techniques influence the passive properties of the muscle-tendon unit (MTU). Techniques that combine a transverse directed force to the physiological technique attempt greater influence on biomechanical properties. No research has investigated the biomechanical effects of a technique with addition of a transverse directed force. This pilot study aimed to explore preliminary data of effectiveness of two techniques on longitudinal load (extensibility and passive resistance) in the hamstring MTU. A counterbalanced quasi-experimental same subject design using fifteen healthy subjects compared two conditions: physiological technique and a technique with addition of a transverse directed force. Passive resistance (torque, Nm) and extensibility (knee extension range of movement) of the hamstring MTU were recorded during and following both conditions. Paired t tests explored within and across condition comparisons, with Bonferroni adjustment to account for multiple analyses. Passive resistance demonstrated a significant reduction for the technique with addition of a transverse directed force (t = 4.26, p < 0.05) that may have contributed to the significant increase in extensibility (t = 8.48, p < 0.05). The data suggest that longitudinal load through the hamstring MTU during a physiological mobilisation can be increased by the application of a transverse directed force. This merits further research.

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Time course of stress relaxation and recovery in human ankles

Abstract

Introduction

Section snippets

Experiment 1

Experiment 1

Discussion

J Biomech

Clin Biomech

Clin Biomech

Clin Biomech

Brain Res

Viscoelastic properties of muscle-tendon units. The biomechanical effects of stretching

Am J Sports Med

The assessment of mobility of metacarpaophalangeal joints

Rheum Phys Med

Viscoelastic stress relaxation in human skeletal muscle

Med Sci Sports Exerc

Effect of duration of passive stretch on hip abduction range of motion

J Orthop Sports Phys Ther

Elasticity of soft tissues in simple elongation

Am J Physiol

Mechanical properties of parallel-fibred collagenous tissues