Peak Passive Torque Research Articles

Effect of a 10-Week Stretching Program of the Triceps Surae Muscle Architecture and Tendon Mechanical Properties

The present study aimed to test if a long-term passive stretching training causes adaptations of the medial gastrocnemius architecture and the Achilles tendon (AT) tangent modulus. A total of 20 males took part in the study. The stretching group (n = 12), performed stretching exercises for the plantar flexors for 10 weeks, 4–5 times a week, which comprised two static positions sustained twice each during 30 s. For the stretching group, maximum dorsiflexion angle, peak passive torque, and muscle–tendon unit maximum length significantly increased after training. No other differences were found related to muscle architecture and AT tangent modulus. Joint amplitude gain after a long-term stretching of the triceps surae was not accompanied by structural or mechanical changes of the medial gastrocnemius and AT tendon, and seems to reflect an increasing stretch tolerance level.

Acute and chronic effects of static stretching at 100% versus 120% intensity on flexibility.

The acute effects of static stretching have been frequently studied, but the chronic effects have not been studied concurrently. Thus, this study aimed to investigate both the acute and chronic effects of static stretching at different intensities on flexibility. Twenty-three healthy men were randomly assigned to perform 1min of static stretching 3days/week for 4weeks at 100% intensity (n = 12) or 120% intensity (n = 11). The acute effects of stretching were assessed by measuring the range of motion (ROM), peak passive torque, and passive stiffness before and after every stretching session; the chronic effects of stretching were assessed by measuring these outcomes at baseline and after 2 and 4weeks of stretching. Compared with the 100% intensity group, the 120% intensity group had significantly greater acute increases in ROM after all 12 sessions, a significantly greater decrease in passive stiffness after 11 of 12 sessions, and a significantly greater increase in peak passive torque after six of 12 sessions. Regarding the chronic effects, ROM was significantly increased in both groups after 2 and 4weeks of stretching. Peak passive torque significantly increased in the 100% intensity group after 2 and 4weeks of stretching, and after 4weeks in the 120% intensity group. Stretching at 120% intensity resulted in significantly greater acute improvements in ROM, peak passive torque, and stiffness than stretching at 100% intensity. Four weeks of stretching increased ROM and peak passive torque but did not decrease passive stiffness, regardless of the stretching intensity.

The optimal duration of high-intensity static stretching in hamstrings

The purpose of this study was to compare the duration of high-intensity static stretching on flexibility and strength in the hamstrings. Fourteen healthy males (20.8 ± 0.6 years, 170.7 ± 6.5 cm, 66.4 ± 9.9 kg) underwent high-intensity static stretching for three different durations (10, 15, and 20 seconds). The intensity of static stretching was set at the maximum point of discomfort. To examine the change in flexibility and strength, range of motion, peak passive torque, relative passive torque, muscle-tendon unit stiffness, peak torque of isokinetic knee flexion, and knee angle at peak torque of isokinetic knee flexion were measured. To evaluate a time course of pain, a numerical rating scale was described. Range of motion (P < 0.01), peak passive torque (P < 0.01), and knee angle at peak torque were increased at all interventions. Relative passive torque (P < 0.01) and muscle-tendon unit stiffness (P < 0.01) were decreased at all interventions. Peak torque decreased after 10 seconds of stretching (P < 0.05). Numerical rating scale during stretching was 8-9 levels in all interventions, the pain disappeared immediately after the post-measurements (median = 0). The results suggested that muscle-tendon unit stiffness decreased regardless of duration of high-intensity static stretching. However, peak torque of isokinetic knee flexion decreased after 10 seconds of high-intensity static stretching, though it was no change after for more than 15 seconds of stretching.

Age-related Changes In The Passive Properties Of The Plantarflexor Muscles

Limited data exists examining age-related changes in the passive mechanical properties of the musculotendon unit. PURPOSE: To examine the influence of age on maximum range of motion (MROM), peak passive torque (PTpass), and the dissipative coefficient (DC). METHODS: Twenty-one young (20.3 ± 2.4 yrs) and 14 older (69 ± 3.1 yrs) men completed MROM and isometric strength (for EMG normalization) assessments of the plantarflexors, following ultrasonography of the gastrocnemii. Muscle cross-sectional area (CSA) and subcutaneous fat corrected echo intensity (EI) of the gastrocnemii were determined as the sum and average of both muscles, respectively. Participants were seated in a calibrated dynamometer, with their leg fully extended and ankle and foot held in a custom steel foot plate. MROM assessments were performed by dorsiflexing the ankle at 5°s-1 from 10° of plantarflexion to the participants maximally tolerated ROM. PTpass, loading, unloading, and the DC were calculated during the initial 80% of MROM. Independent samples t-tests were used to examine group differences. A Pearson’s correlation coefficient was used to determine the relationship between PTpass and MROM. Analyses of covariance (ANCOVAs) were used to determine age-related differences in loading and unloading, while controlling for MROM. Additional ANCOVAs were used to determine the age-related difference in DC, while controlling for CSA and EI, respectively. An alpha level of 0.05 was used to determine statistical significance. RESULTS: The PTpass, MROM, loading, and unloading (P ≤ 0.046) were greater in the younger men, whereas the DC and EI (P ≤ 0.024) were greater in the older men. When accounting for MROM, unloading (P = 0.044) remained significantly different between groups, while there was no difference between groups for loading (P = 0.223). When accounting for CSA, differences between groups for the DC remained (P = 0.028), while there were no longer differences between groups when accounting for EI (P = 0.120). PTpass was also strongly related to MROM (r = 0.755, P < 0.001). Mean EMG amplitude values across muscles was 1.61% MVC. CONCLUSIONS: Older men exhibited lower MROM and greater DC, which may be explained by an altered stretch tolerance and qualitative changes (i.e. non-contractile tissue accumulation) in aged skeletal muscle, respectively.

The effects of 6 weeks of constant-angle muscle stretching training on flexibility and muscle function in men with limited hamstrings’ flexibility

The aim of the present study was to evaluate the effects of 6weeks of a constant-angle hamstring muscle flexibility training on muscle-tendon stiffness and the range of motion (ROM) in young men with limited hamstring ROM. 13 participants performed unilateral stretching training (EL), while the contralateral limb acted as control (CL). ROM, relative and peak passive torque, passive stiffness, dynamic knee flexion strength, and active optimum joint angle were assessed before and after the last training session. In addition, participants were tested during the first and last training sessions for first stretch sensation during the stretching procedure only in the EL. Straight-leg raise and isokinetic knee ROM tests (both p < 0.0001; from 59.4 ± 8.1 to 70.3 ± 9.8, from 28.3 ± 7.6 to 18.5 ± 5.2, respectively) and peak passive torque (p = 0.001; from 53.1 ± 11.7 to 64.9 ± 12.3) increased only in EL and no changes in relative passive torque, passive stiffness, dynamic knee flexion strength, and active optimum joint angle (p > 0.05) were observed. At the point of first stretch sensation, significant increases in passive torque (p = 0.004) and angle (p < 0.001) were found from pre- to post-training. The flexibility training induced significant increases in ROM alongside increases in peak passive torque (stretch tolerance) and the ROM at which stretch was first perceived. However, this occurred without changes in muscle-tendon mechanical properties or transfer to the untrained limb (CL). These results suggest that limb-specific ROM increases were underpinned by neural adaptations.

Effects of Instrument-assisted Soft Tissue Mobilization on Musculoskeletal Properties.

ABSTRACTPurposeInstrument-assisted soft tissue mobilization (IASTM) has been reported to improve joint range of motion (flexibility). However, it is not clear whether this change in the joint range of motion is accompanied by any alterations in the mechanical and/or neural properties. This study aimed to investigate the effects of IASTM in plantarflexors and Achilles tendon on the mechanical and neural properties of them.MethodsThis randomized, controlled, crossover study included 14 healthy volunteers (11 men and 3 women, 21–32 yr). IASTM was performed on the skin over the posterior part of the lower leg for 5 min and targeted the soft tissues (gastrocnemii, soleus, and tibialis posterior muscles; overlying deep fascia; and Achilles tendon). As a control condition, the same participants rested for 5 min between pre- and postmeasurements without IASTM on a separate day. The maximal ankle joint dorsiflexion angle (dorsiflexion range of motion), the peak passive torque (stretch tolerance), and the ankle joint stiffness (slope of the relationship between passive torque and ankle joint angle) during the measurement of the dorsiflexion range of motion and muscle stiffness of the triceps surae (using shear wave elastography) were measured before and immediately after the interventions.ResultsAfter IASTM, the dorsiflexion range of motion significantly increased by 10.7% ± 10.8% and ankle joint stiffness significantly decreased by −6.2% ± 10.1%. However, peak passive torque and muscle stiffness did not change. All variables remained unchanged in the repeated measurements of controls.ConclusionIASTM can improve joint range of motion, without affecting the mechanical and neural properties of the treated muscles.

Effects of Functional Training and Calf Stretching on Risk of Falls in Older People: A Pilot Study.

This study aimed to determine the effects of a functional training and ankle stretching program in triceps surae torque, passive stiffness index, and in the risk for fall indicators in older adults. Twenty women (73.4 ± 7.3 years) were allocated into an intervention or control group. The 12-week intervention consisted of functional training and calf stretching exercises performed twice a week. Measurements of peak passive and active torque, passive stiffness, maximum dorsiflexion angle, and indexes of risk for falls (Timed Up and Go, functional reach test, QuickScreen-test) were collected. There were no significant differences for all variables, except the maximum dorsiflexion angle, which increased in the intervention group from 33.78 ± 8.57° to 38.89 ± 7.52°. The exercise program was not sufficient to enhance performance on functional tests and decrease the risk for falls in older adults. The significant increase in the maximum dorsiflexion indicates a positive impact of stretching exercises.

Classification of individual flexibility: before and after a long-term stretching program

The evaluation of the stretching effects through mean values of the entire sample can hide different adaptations between groups with distinct characteristics of joint flexibility. This study aimed to employ artificial neural networks to classify subjects according to their flexibility level and to investigate the effects of a 10-week stretching training. The stretching group (SG, n = 9) performed stretching exercises for triceps surae muscles 4–5 times a week over 10 weeks. Maximum dorsiflexion angle (MDA) and peak passive torque (PPT) data at pre-intervention were used in a k-means (k = 3) algorithm to group participants as flexible, intermediate or stiff. A feed-forward artificial neural network (multilayer perceptron) was trained using the pre-intervention dataset with the k-means labeled groups and classified the post-intervention data generated after the stretching protocol. MDA of SG increased significantly (p = 0.015) from 24.72 ± 7.70 to 29.81 ± 6.95° whereas PPT showed no significant differences. Following intervention, two subjects from the SG shifted from the intermediate to the flexible group, whereas one stiff subject changed to the intermediate group. The control group presented a random pattern of group change. This approach can aid future analysis of different adaptations to stretching programs.

Stretching Effects: High-intensity & Moderate-duration vs. Low-intensity & Long-duration.

This study examined whether a high-intensity, moderate-duration bout of stretching would produce the same acute effects as a low-intensity, long-duration bout of stretching. 17 volunteers performed 2 knee-flexor stretching protocols: a high-intensity stretch (i. e., 100% of maximum tolerable passive torque) with a moderate duration (243.5 ± 69.5-s); and a low-intensity stretch (50% of tolerable passive torque) with a long duration (900-s). Passive torque at a given sub-maximal angle, peak passive torque, maximal range of motion (ROM), and muscle activity were assessed before and after each stretching protocol (at intervals of 1, 30 and 60 min). The maximal ROM and tolerable passive torque increased for all time points following the high-intensity stretching (p<0.05), but not after the low-intensity protocol (p>0.05). 1 min post-stretching, the passive torque decreased in both protocols, but to a greater extent in the low-intensity protocol. 30 min post-test, torque returned to baseline for the low-intensity protocol and had increased above the baseline for the high-intensity stretches. The following can be concluded: 1) High-intensity stretching increases the maximal ROM and peak passive torque compared to low-intensity stretching; 2) low-intensity, long-duration stretching is the best way to acutely decrease passive torque; and 3) high-intensity, moderate-duration stretching increases passive torque above the baseline 30 min after stretching.

Nonoperative, Dynamic Treatment of Acute Achilles Tendon Rupture: Influence of Early Weightbearing on Biomechanical Properties of the Plantar Flexor Muscle–Tendon Complex—A Blinded, Randomized, Controlled Trial

Acute Achilles tendon rupture alters the biomechanical properties of the plantar flexor muscle–tendon complex that can affect functional performance and the risk of repeat injury. The purpose of the present study was to compare the biomechanical properties of the plantar flexor muscle–tendon complex in patients randomized to early weightbearing or non-weightbearing in the nonoperative treatment of Achilles tendon rupture. A total of 60 patients were randomized to full weightbearing from day 1 of treatment or non-weightbearing for 6 weeks. After 6 and 12 months, the peak passive torque at 20° dorsiflexion, the stiffness during slow stretching, and the maximal strength were measured in both limbs. The stiffness of the plantar flexor muscle–tendon complex in the terminal part of dorsiflexion was significantly increased (p = .024) in the non-weightbearing group at 12 months. The peak passive torque was significantly lower for the affected limb at 6 months (91%; p = .01), and the stiffness was significantly lower for the affected limb during the early part of dorsiflexion at 6 (67%; p < .001) and 12 (77%; p < .001) months. In conclusion, an increased stiffness of the plantar flexor muscle–tendon complex in the terminal part of dorsiflexion was found in the non-weightbearing group. The altered stiffness and strength in the affected limb could affect the coordination of gait and running.

Are rest intervals between stretching repetitions effective to acutely increase range of motion?

Static stretching with rest between repetitions is often performed to acutely increase joint flexibility. To test the effects of the lack of resting between stretching repetitions and the minimal number of stretching repetitions required to change the maximal range of motion (ROM), maximal tolerated joint passive torque (MPT), and submaximal passive torque at a given angle (PT). Five static stretching repetitions with a 30-s rest-interval (RI) and a no-rest-interval (NRI) stretching protocol were compared. Participants (N=47) were encouraged to perform the maximal ROM without pain in all the repetitions. Each repetition lasted 90 s. Maximal ROM, MPT, PT, and muscle activity were compared between protocols for the same number of stretching repetitions. The NRI produced a higher increase in maximal ROM and MPT during and after stretching (P<.05). PT decreased in both protocols, although the NRI tended to have a lower decrement across different submaximal angles (.05<P<.08) in the initial range of the torque-angle curve. Significant changes in maximal ROM (P<.01) and PT (P<.01) were obtained at the 3rd and 2nd repetitions of RI, respectively. The RI did not significantly increase the MPT (P=.12) after stretching; only the NRI did (P<.01). Lack of rest between repetitions more efficiently increased the maximal ROM and capacity to tolerate PT during and after stretching. The use of 30 s rest between repetitions potentiates the decrease in PT. Rest intervals should not be used if the aim is to acutely increase maximal ROM and peak passive torque.

Acute effects of passive stretching of the plantarflexor muscles on neuromuscular function: the influence of age.

The acute effects of stretching on peak force (Fpeak), 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. Fpeak (-11 %), %VA (-6 %), and MG EMG amplitude (-9 %) decreased after stretching in the young, but not the old (P > 0.05). Changes in Fpeak 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.

Biomechanical properties of the plantar flexor muscle–tendon complex 6 months post‐rupture of the achilles tendon

We compared the effects of a non-weight bearing protocol (NWB) and a weight bearing (WB) protocol on energy stored, stiffness, and shock absorption in the plantar flexor muscle-tendon unit of patients managed non-operatively following an Achilles tendon rupture. Thirty-eight subjects were randomized to a WB cast fitted with a Bohler iron or a traditional non-weight-bearing cast. At a 6-month follow-up, a biomechanical assessment utilizing an isokinetic dynamometer allowed measurement of peak passive torque, energy stored, shock absorption, and stiffness. The WB group had greater peak passive torque (≈ 20%). Irrespective of group, peak passive torque in unaffected legs was greater (≈ 26%) than affected legs. Across the groups, energy stored in the NWB group was 74% of the WB group. The energy stored in affected legs was 80% of that in unaffected legs. Shock absorption was not significantly different across legs or groups. Irrespective of group, affected legs had significantly less stiffness (20-40%). While the augmentation of plaster with a Bohler iron to allow increased weight bearing had positive effects, deficits in affected compared to unaffected legs irrespective of group were notable, and should be addressed prior to participation in vigorous physical activities.

Relationship Between Age and Spasticity in Children With Diplegic Cerebral Palsy

Pierce SR, Prosser LA, Lauer RT. Relationship between age and spasticity in children with diplegic cerebral palsy. Objective To examine the relationship between passive torque, reflex activity, co-contraction, and age during the assessment of spasticity of knee flexors and extensors in children with spastic diplegic cerebral palsy (CP). Design Retrospective. Setting Pediatric orthopedic hospital. Participants Children (N=36) with spastic diplegic CP. Interventions Not applicable. Main Outcome Measures Spasticity of the knee flexors and knee extensors (as measured by peak passive torque, mean passive torque, reflex activity of the medial hamstrings, reflex activity of vastus lateralis, and co-contraction) was assessed during passive movements completed using an isokinetic dynamometer with concurrent electromyography. Results A significant positive relationship was found between age and mean knee flexor passive torque ( P<.05), while a significant negative relationship was found between age and mean percentage of the range of motion with co-contraction ( P<.05). Conclusions Our results suggest that passive stiffness may play a larger role in spasticity than reflex activity as children with spastic diplegic CP age. Additional research is needed to determine whether subject age could influence the effectiveness of interventions, such as serial casting or botulinum toxin, for spasticity in children with spastic diplegic CP.

Effects of an acute hamstring stretch in people with and without osteoarthritis of the knee

Objective To compare the effects of an acute stretching intervention on knee extension range of motion, passive resistive torque and stiffness in subjects with osteoarthritis of the knee, and to compare these variables with subjects without osteoarthritis. Design Cross-sectional experimental study. Setting Human performance laboratory. Participants A total of 55 participants were recruited: 28 subjects (males and females) with osteoarthritis of the knee joint and 27 subjects of a similar age without osteoarthritis of the knee joint. Intervention Using the Kincom dynamometer, three 60-second stretches with 60 seconds of rest between stretches were applied to the hamstring muscle group. Main outcome measures Peak knee extension range of motion, peak passive torque and stiffness in the final 10% of knee extension range of motion. Results A significant ( P < 0.05) increase in knee extension range of motion, peak passive torque and stiffness was observed in both groups. For knee extension range of motion, the mean difference for the osteoarthritis group and non-osteoarthritis group was 4.9 degrees [95% confidence interval (CI) 0.9 to 8.5] and 4.4 degrees (95% CI 1.8 to 6.8), respectively. For peak passive torque, the mean difference in the osteoarthritis group and the non-osteoarthritis group was 4.4 N m (95% CI 0.8 to 6.9) and 1.0 N m (95% CI −1.4 to 3.5), respectively. For stiffness in the final 10% of knee extension range of motion, the mean difference for the osteoarthritis group and the non-osteoarthritis group was 0.19 N m/degree (95% CI 0.08 to 0.3) and 0.04 N m/degree (95% CI −0.05 to 0.1), respectively. Stiffness in the final 10% of knee extension range of motion was significantly higher in the osteoarthritis group compared with the non-osteoarthritis group after stretching. Conclusions Elderly individuals with and without osteoarthritis of the knee are able to demonstrate immediate beneficial adaptations to a stretching intervention. This is important as stretching is often used in preparation for exercise programmes.

Examination of Spasticity of the Knee Flexors and Knee Extensors Using Isokinetic Dynamometry With Electromyography and Clinical Scales in Children With Spinal Cord Injury

Background/Objective: To examine the role of reflex activity in spasticity and the relationship between peak passive torque, Ashworth Scale (AS), and Spasm Frequency Scale (SFS) of the knee flexors and extensors during the measurement of spasticity using an isokinetic dynamometer in children with spinal cord injury (SCI).Methods: Eighteen children with chronic SCI and 10 children of typical development (TD) participated. One set of 10 passive movements was completed using an isokinetic dynamometer at 15, 90, and 180 degrees per second (deg/s) while surface electromyographic data were collected from the vastus lateralis (VL) and medial hamstrings (MH). Spasticity was clinically assessed using the AS and SFS.Results: There were no significant differences in peak passive torque of the knee flexors and extensors at any velocity for children with SCI compared to children with TD. Children with TD demonstrated significantly more reflex activity of the MH during the assessment of knee flexor spasticity at all movement velocities than did children with SCI. Children with TD demonstrated significantly more reflex activity of the VL during the assessment of knee-extensor spasticity with movements at 180 deg/s. The relationship between peak passive torque, AS, and SFS was significant during movements at a velocity of 90 deg/s only. Conclusions: The role of increased reflexes in spasticity needs further examination. Isokinetic dynamometry may be measuring a different aspect of spasticity than the AS and SFS do in children with SCI.

Acute passive stretching alters the mechanical properties of human plantar flexors and the optimal angle for maximal voluntary contraction

The purpose of this study was to investigate whether acute passive stretching (APS) reduced maximal isometric voluntary contraction (MVC) of the plantar flexors (PF) and if so, by what mechanisms. The PF in 15 female volunteers were stretched for 10 min (5 x 120 s) by a torque motor to within 2 degrees of maximum dorsiflexion (D) range of motion (ROM). MVC with twitch interpolation, maximal Hoffmann reflex (H(max)) and compound action potentials (M(max)) were recorded at 20 degrees D. Stretch reflexes (SR) were mechanically induced at 200 degrees s(-1) between 0 degrees and 10 degrees ( )D and SR torque and EMG amplitude were determined. All tests were assessed pre- (pre) and post-APS (post-test(1)). MVC, SR, and M(max) were again assessed after additional stretch was applied [mean 26 (1) degrees D; post-test(2)] to test if the optimal angle had been altered. EMG was recorded from soleus (SOL), medial gastrocnemius (MG) and tibialis anterior (TA) using bipolar surface electrodes. APS resulted in a 27% decrease in mean peak passive torque (P<0.05). MVC and SR torque were 7% (P<0.05) and 13% lower at post-test(1) (P<0.05), respectively. SR EMG amplitude of SOL and MG was reduced by 27% (P<0.05) and 22% (P<0.05), respectively. The H(max)/M(max) EMG and H(max)/M(max) torque ratios were unchanged at post-test(1). At post-test(2), MVC and SR EMG recovered to pre-APS values, while the SR and M(max) torque increased by 19% and 13%, respectively (P<0.05). The decrease in MVC during post-test(1) was attributed to changes in the mechanical properties of PF and not to reduced muscle activation.

The Effect of Prolonged Static and Cyclic Stretching on Ankle Joint Stiffness, Torque Relaxation, and Gait in People With Stroke

Continuous passive motion (cyclic stretching applied to the subject's limb) has been used for the rehabilitation of some orthopedic impairments; however, few researchers have considered its application in the management of neurological disorders such as stroke. The purpose of this study was to examine the short-term effects of prolonged static and cyclic calf stretching on passive ankle joint stiffness, torque relaxation, and gait in people with ischemic stroke. Ten community-dwelling people (mean age=64.6 years, SD=8.76, range=53-76) who were diagnosed with a cerebrovascular accident volunteered to be subjects. Participants engaged in one 30-minute static stretch and one 30-minute cyclic stretch of the calf muscle, using an isokinetic dynamometer that also collected torque and angle measurements. Before and after treatments, 10-m walking times were collected. Ankle joint stiffness was calculated from the slope of the torque and angle curves before and immediately after treatments, and torque relaxation was calculated as the percentage of decrease in peak passive torque over the 30-minute stretch durations. Ankle joint stiffness decreased by 35% and 30% after the static and cyclic stretches, respectively. Stiffness values and 10-m walk times were not different between conditions. The amount of torque relaxation was 53% greater for static stretching than for cyclic stretching. These preliminary data from a very small sample of people with stroke indicate that ankle joint stiffness decreases after both prolonged static and cyclic stretches; however, neither technique appears to be better at reducing stiffness in people with stroke. Torque relaxation is greater after static stretching than after cyclic stretching, and walking speed does not appear to be influenced by the stretching treatments used in our study.

TIME COURSE OF STRESS RELAXATION WITH REPETITIVE STRETCHING OF HUMAN PLANTARFLEXORS

1445 The purpose of this study was to monitor the stress relaxation response to repeated maximum passive stretching (PSmax) of the ankle plantarflexors. Ten university students (6 men, 4 women) underwent 25 min of cyclical, PSmax (10 stretches [S1-S10] over 25 min, 15 s rest between stretches) to a maximum dorsiflexion position (Dmax) each stretch. Soleus EMG confirmed that each stretch was passive. Dmax joint angle, peak passive torque (PTpeak), and passive torque in Dmax was observed during each 2 min stretch, and passive torque decay (PTd) for the intervals from 0 to 15 s (I1), 15 to 30 s (I2), 30 to 45 s (I3), and 105 to 120 s (IE) was calculated. Dmax increased significantly by S2 (P<0.005) and from S2 to S3 (P<0.05) so that 59%(3.4 °) of a total 5.8 ° increase in Dmax over ten stretches(P<0.005), had occured by S3 (P<0.005). PTpeak increased 12% from S1 to S8 (P=0.06). Total PTd was greater in S1 (P<0.005) than S2-S10. Greater PTd was observed in I1 (P<0.005) than I2, I3, and IE of any single stretch so that 45% of PTd in a 2 min stretch, occurs in the first 15s. Greater PTd was observed in I1 of S1 compared to I1 of all other stretches (P<0.005). These data indicate that a significant viscoelastic stress relaxation response occurs within the first 15s of a single stretch and within the first two stretches of a ten stretch protocol. Tissue creep, and increased stretch tolerance, likely allow for further responses beyond the early viscoelastic stress relaxation.

Peak Passive Resistive Torque at Maximum Inversion Range of Motion in Subjects With Recurrent Ankle Inversion Sprains

Although a number of mechanical and neuromuscular processes have been identified, the primary mechanisms underlying residual functional instability of the ankle remain unclear. Understanding such mechanisms will help physical therapists identify where to focus treatment efforts, ultimately leading to more effective rehabilitation. In the present investigation, resistive torque at maximum ankle inversion was evaluated to determine if lateral ankle structures demonstrated mechanical laxity. Thirty subjects with a history of unilateral recurrent inversion sprains were tested bilaterally. A custom-made apparatus provided a stress to the lateral ankle in a method that was similar to the inversion stress test. Two measures of laxity were used: maximum passive inversion range of motion and peak passive resistive torque. Differences between the involved and uninvolved ankles were determined using analysis of covariance procedures. There were no significant differences between involved and uninvolved ankles for maximum inversion range of motion and for peak passive resistive torque. Post hoc testing confirmed adequate statistical power. The results support previous investigations, which suggest that functional instability can exist in the absence of mechanical lateral ankle laxity.