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Renato Semadeni and Kai-Uwe Schmitt

Objective:

In this study a numerical model of a skier was developed to investigate the effect of different rehabilitation strategies after anterior cruciate ligament (ACL) rupture.

Methods:

A computer model using a combined finite-element and multibody approach was established. The model includes a detailed representation of the knee structures, as well as all major leg muscles. Using this model, different strategies after ACL rupture were analyzed.

Results:

The benefit of muscle training to compensate for a loss of the ACL was shown. The results indicate that an increase of 10% of the physiological cross-sectional area has a positive effect without subjecting other knee structures to critical loads. Simulating the use of a hamstring graft indicated increasing knee loads. A patellar-tendon graft resulted in an increase of the stress on the lateral collateral ligament.

Conclusion:

Muscle training of both extensors and flexors is beneficial in medical rehabilitation of ACL-deficient and ACL-reconstructed knees.

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Geraldine L. Pellecchia, Holly Hamel and Peter Behnke

The purpose of this study was to compare an established protocol of modalities and transverse friction massage (MOD & TFM) with iontophoresis of dexamethasone and lidocaine (IONTO) in the treatment of patients with infrapatellar tendinitis. Thirty cases with infrapatellar tendinitis were randomly assigned to either the MOD & TFM or the IONTO intervention. Subjects still symptomatic after six sessions of intervention received the alternate treatment protocol. Four measures were used to assess patient status: a functional index questionnaire, a visual analog pain scale, a rating of tenderness with palpation of the involved tendon, and the number of step-ups needed to elicit pain. In response to the MOD & TFM intervention, only the number of step-ups performed to elicit pain showed significant improvement. All status measures improved significantly with the IONTO intervention. The results suggest that iontophoresis may be more effective and efficient in decreasing pain, reducing inflammation, and promoting healing in patients with infrapatellar tendinitis.

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Benno M. Nigg, Gerald K. Cole and Gert-Peter Brüggemann

Impact forces have been speculated to be associated with the development of musculoskeletal injuries. However, several findings indicate that the concepts of “impact forces” and the paradigms of their “cushioning” may not be well understood in relation to the etiology of running injuries and that complex mechanisms may be responsible for injury development during running. The purposes of this paper are (a) to review impact mechanics during locomotion, (b) to review injuries and changes of biological tissue due to impact loading, and (c) to synthesize the mechanical and biological findings. In addition, directions for future research are discussed. Future research should address the development of noninvasive techniques to assess changes in the morphology and biochemistry of bone, cartilage, tendon, and ligaments; researchers should also try to simulate impact loading during activities such as running, focusing on the interaction of the various loading parameters that determine the acceptable windows of loading for biological tissues.

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Danielle M. DeBruyne, Marina M. Dewhurst, Katelyn M. Fischer, Michael S. Wojtanowski and Chris Durall

Clinical Scenario:

Increasing the length of the muscle–tendon unit may prevent musculotendinous injury. Various methods have been proposed to increase muscle–tendon flexibility, including self-mobilization using foam rollers or roller massagers, although the effectiveness of these devices is uncertain. This review was conducted to determine if the use of foam rollers or roller massagers to improve hamstrings flexibility is supported by moderate- to high-quality evidence.

Clinical Question:

Are foam rollers or roller massagers effective for increasing hamstrings flexibility in asymptomatic physically active adults?

Summary of Key Findings:

The literature was searched for studies on the effects of using foam rollers or roller massagers to increase hamstrings flexibility in asymptomatic physically active adults. Four randomized controlled trials were included; 2 studies provided level 2 or 3 evidence regarding foam rollers and 2 studies provided level 2 or 3 evidence regarding roller massagers. Both roller-massager studies reported increases in hamstrings flexibility after treatment. Data from the foam-roller studies did not demonstrate a statistically significant increase in hamstrings flexibility, but 1 study did demonstrate a strong effect size.

Clinical Bottom Line:

The reviewed moderate-quality studies support the use of roller massagers but provide limited evidence on the effectiveness of foam rolling to increase hamstrings flexibility in asymptomatic physically active adults. Flexibility gains may be improved by a longer duration of treatment and administration by a trained therapist. Gains appear to decline rapidly postrolling. Neither device has been shown to confer a therapeutic benefit superior to static stretching, and the effectiveness of these devices for preventing injury is unknown.

Strength of Recommendation:

Grade B evidence supports the use of roller massagers to increase hamstrings flexibility in asymptomatic physically active adults.

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Vera L. Talis and Irina A Solopova

We investigated the development of postural reactions induced in standing subjects by Achilles tendon vibration. We compared vibratory reactions in 3 different conditions: normal standing, standing near support, and when the solid support being protracted forward changed the initial posture. Additional support for the back was placed at subject's sacral or shoulder level. In the easy standing condition, the postural vibration reaction consists of progressive backward upper body movement. When the body contacted the additional support on the sacral level during the vibratory reaction, the movement of the upper body continued in most of the subjects. This was accompanied by an increase of pressure on the toes. When the support was applied at the shoulder level, the body motion reversed its direction in half of the subjects. In this case, backward-forward oscillations occurred near the support. The initial change of body-support interaction did not influence the ensuing vibration reaction; namely the reaction was similar to that with the support near to the body at the sacral level. Our data demonstrate that the vibration-induced reaction is not a local reaction limited to one joint, but a complex postural synergy that involves both leg and trunk muscles and integrates the information from touch and pressure afferents of the upper body.

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George Vagenas and Blaine Hoshizaki

The purpose of this study was to identify the kinematic characteristics of bilateral rearfoot asymmetry during heel–toe running under two experimental conditions: worn (broken-in) running shoes and new (standardized) running shoes. High-speed cinematography (150 fps) was used to film the lower limbs of four male runners in the frontal plane while running on a treadmill at their training pace. Six successive footfalls were analyzed for each subject and selected kinematical variables of the rearfoot function were calculated. Significant asymmetries were found in lower leg angle and Achilles tendon angle at touchdown and at maximum pronation. Total pronation and rearfoot angle were almost symmetric. The angular displacement graphs for the shank and foot revealed a distinct overall asymmetry between the lower limbs in both conditions. The mean values of the kinematical asymmetries were appreciably higher in the new shoe condition. It is proposed that the degree of these asymmetries is subject to changes due to injury, personal running style, and stability of the running shoe. Trends of bilateral dominance specific to rearfoot control in running were identified.

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Annette J. Raynor

The patellar tendon reflex (PTR) and simple visual reaction time (VRT) were fractionated and compared in 40 subjects with developmental coordination disorder (DCD) and normal coordination (NC) in two age groups. Four equal groups of subjects, 6 years DCD (6DCD), 6 years NC (6NC), 9 years DCD (9DCD), and 9 years NC (9NC) were compared using ANOVA for the main effects of coordination and age. PTR and its components of reflex latency and motor time were not significantly affected by the level of coordination; however, a significant coordination by age interaction (p < .05) revealed an increased motor time in the 6DCD group. VRT, premotor time, and motor time were all significantly (p < .05) increased in children with DCD; the increased VRT and premotor time support earlier findings, whereas the increased motor time has not previously been found. These findings suggest that the processing of reflexive and volitional responses by children with DCD differs from that of their NC peers.

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David Diggin, Ross Anderson and Andrew J. Harrison

Evidence suggests reports describing the reliability of leg-spring (kleg) and joint stiffness (kjoint) measures are contaminated by artifacts originating from digital filtering procedures. In addition, the intraday reliability of kleg and kjoint requires investigation. This study examined the effects of experimental procedures on the inter- and intraday reliability of kleg and kjoint. Thirty-two participants completed 2 trials of single-legged hopping at 1.5, 2.2, and 3.0 Hz at the same time of day across 3 days. On the final test day a fourth experimental bout took place 6 hours before or after participants’ typical testing time. Kinematic and kinetic data were collected throughout. Stiffness was calculated using models of kleg and kjoint. Classifications of measurement agreement were established using thresholds for absolute and relative reliability statistics. Results illustrated that kleg and kankle exhibited strong agreement. In contrast, kknee and khip demonstrated weak-to-moderate consistency. Results suggest limits in kjoint reliability persist despite employment of appropriate filtering procedures. Furthermore, diurnal fluctuations in lower-limb muscle-tendon stiffness exhibit little effect on intraday reliability. The present findings support the existence of kleg as an attractor state during hopping, achieved through fluctuations in kjoint variables. Limits to kjoint reliability appear to represent biological function rather than measurement artifact.

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Pablo B. Costa, Eric D. Ryan, Trent J. Herda, Ashley A. Walter, Katherine M. Hoge and Joel T. Cramer

This study examined the acute effects of passive stretching on electromechanical delay (EMD), peak twitch force (PTF), rate of force development (RFD), and peak-to-peak M-wave (PPM) for the soleus muscle during evoked isometric plantar flexion muscle actions. Fourteen men (mean age ± SD = 21.2 ± 2.4 years; body mass = 80.0 ± 14.9 kg; height = 176.9 ± 7.2 cm) and 20 women (20.9 ± 2.5 years; 61.3 ± 8.9 kg; 165.3 ± 7.5 cm) volunteered for the study. Five single-square, supramaximal transcutaneous electrical stimuli (each separated by 5 s) were delivered to the tibial nerve before and after passive stretching. A time × gender interaction was observed for EMD, and the post hoc dependent-samples t tests indicated that EMD increased 4% for the women (p = .023), but not for the men (p = .191). There were no other stretching-related changes for PTF, RFD, or p-p M-wave for either the men or women (p > .05). These findings tentatively suggested that mechanical factors related to the stiffness of the muscle-tendon unit may contribute to the explanation for why stretching caused an acute increase in the EMD during evoked twitches in the women, but not in the men.

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Samantha L. Winter and John H. Challis

For a physiologically realistic joint range of motion and therefore range of muscle fiber lengths, only part of the whole muscle force-length curve can be used in vivo; that is, only a section of the force-length curve is expressed. Previous work has determined that the expressed section of the force-length curve for individual muscles can vary between subjects; however, the degree of intersubject variability is different for different muscles. This study determined the expressed section of both the rectus femoris and gastrocnemius—muscles with very different ratios of tendon slack length to muscle fiber optimum length—for 28 nonspecifically trained subjects to test the hypothesis that the value of this ratio affects the amount of variability in the expressed section. The force-length curves of the two muscles were reconstructed from moment-angle data using the method of Herzog & ter Keurs (1988). There was no relationship between the expressed sections of the force-length curve for the two muscles. Less variability was found in the expressed section of the gastrocnemius compared with the rectus femoris, supporting the hypothesis. The lack of relationship between the expressed sections of the two muscles has implications for motor control and for training muscle for rehabilitation.