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Michael Lyght, Matthew Nockerts, Thomas W. Kernozek and Robert Ragan

Achilles tendon (AT) injuries are common in runners. The AT withstands high magnitudes of stress during running which may contribute to injury. Our purpose was to examine the effects of foot strike pattern and step frequency on AT stress and strain during running utilizing muscle forces based on a musculoskeletal model and subject-specific ultrasound-derived AT crosssectional area. Nineteen female runners performed running trials under 6 conditions, including rearfoot strike and forefoot strike patterns at their preferred cadence, +5%, and –5% preferred cadence. Rearfoot strike patterns had less peak AT stress (P < .001), strain (P < .001), and strain rate (P < .001) compared with the forefoot strike pattern. A reduction in peak AT stress and strain were exhibited with a +5% preferred step frequency relative to the preferred condition using a rearfoot (P < .001) and forefoot (P=.005) strike pattern. Strain rate was not different (P > .05) between step frequencies within each foot strike condition. Our results suggest that a rearfoot pattern may reduce AT stress, strain, and strain rate. Increases in step frequency of 5% above preferred frequency, regardless of foot strike pattern, may also lower peak AT stress and strain.

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Dominic James Farris, Erica Buckeridge, Grant Trewartha and Miranda Polly McGuigan

This study assessed the effects of orthotic heel lifts on Achilles tendon (AT) force and strain during running. Ten females ran barefoot over a force plate in three conditions: no heel lifts (NHL), with 12 mm heel lifts (12HL) and with 18 mm heel lifts (18HL). Kinematics for the right lower limb were collected (200 Hz). AT force was calculated from inverse dynamics. AT strain was determined from kinematics and ultrasound images of medial gastrocnemius (50 Hz). Peak AT strain was less for 18HL (5.5 ± 4.4%) than for NHL (7.4 ± 4.2%) (p = .029, effect size [ES] = 0.44) but not for 12HL (5.8 ± 4.8%) versus NHL (ES = 0.35). Peak AT force was significantly (p = .024, ES = 0.42) less for 18HL (2382 ± 717 N) than for NHL (2710 ± 830 N) but not for 12HL (2538 ± 823 N, ES = 0.21). The 18HL reduced ankle dorsiflexion but not flexion-extension ankle moments and increased the AT moment arm compared with NHL. Thus, 18HL reduced force and strain on the AT during running via a reduction in dorsiflexion, which lengthened the AT moment arm. Therefore, heel lifts could be used to reduce AT loading and strain during the rehabilitation of AT injuries.

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Carlan K. Yates, Michael R. McCarthy, Howard S. Hirsch and Mark S. Pascale

This study examined the benefits and possible risks of immediate continuous passive motion after autogenous patellar tendon reconstruction of the anterior cruciate ligament. Thirty patients scheduled to undergo ACL reconstruction were prospectively randomized into two groups, CPM and non-CPM. Postoperatively, those in the non-CPM group wore a hinged knee brace. Those in the CPM group were kept on a CPM machine 16 hrs a day while in the hospital and they used it 6 hrs a day for the first 2 weeks postoperatively. After surgery the patients were assessed for hemovac drainage, range of motion, swelling, effusion, subjective pain, and use of pain medication. The CPM group had significantly less swelling and effusion, required less pain medication, and had greater knee flexion. No differences were found in hemovac drainage, passive knee extension, or subjective pain reports despite a significantly greater use of pain medication in the non-CPM group. The results suggest that immediate CPM after ACL reconstruction is safe and facilitates early range of motion by decreasing the amount of pain medication, effusion, and soft tissue swelling.

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Keitaro Kubo, Teruaki Komuro, Noriko Ishiguro, Naoya Tsunoda, Yoshiaki Sato, Naokata Ishii, Hiroaki Kanehisa and and Tetsuo Fukunaga

The present study aimed to investigate the effects of low-load resistance training with vascular occlusion on the specific tension and tendon properties by comparing with those of high-load training. Nine participants completed 12 weeks (3 days/week) of a unilateral isotonic training program on knee extensors. One leg was trained using low load (20% of 1 RM) with vascular occlusion (LLO) and other leg using high load (80% of 1 RM) without vascular occlusion (HL). Before and after training, maximal isometric knee extension torque (MVC) and muscle volume were measured. Specific tension of vastus lateralis muscle (VL) was calculated from MVC, muscle volume, and muscle architecture measurements. Stiffness of tendon-aponeurosis complex in VL was measured using ultrasonography during isometric knee extension. Both protocols significantly increased MVC and muscle volume of quadriceps femoris muscle. Specific tension of VL increased significantly 5.5% for HL, but not for LLO. The LLO protocol did not alter the stiffness of tendon-aponeurosis complex in knee extensors, while the HL protocol increased it significantly. The present study demonstrated that the specific tension and tendon properties were found to remain following low-load resistance training with vascular occlusion, whereas they increased significantly after high-load training.

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Seong-won Han, Dae-yeon Lee, Dong-Sung Choi, Boram Han, Jin-Sun Kim and Hae-Dong Lee

This study aimed to examine whether muscle force and tendon stiffness in a muscle-tendon complex alter synchronously following 8-week whole-body vibration (WBV) training in older people. Forty older women aged 65 years and older were randomly assigned into control (CON, n = 15) and whole-body vibration (WBV) training groups (exposure time, n = 13; vibration intensity, n = 12). For the training groups, a 4-week detraining period was completed following the training period. Throughout the training/detraining period, force of the medial gastrocnemius (MG) muscle and stiffness of the Achilles tendon were assessed four times (0, 4, 8, and 12 weeks) using a combined system of dynamometer and ultrasonography. While muscle force gradually increased throughout the training period (p < .05), a significant increase in tendon stiffness was observed after 8 weeks (p < .05). These findings indicated that, during the early phase of WBV training, muscle force and tendon stiffness changed asynchronously, which might be a factor in possible musculotendinous injuries.

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Akinori Nagano, Taku Komura and Senshi Fukashiro

The two goals of this study were (a) to evaluate the effects of the series elasticity of the muscle tendon complex on an explosive performance that allows a counter movement, and (b) to determine whether or not a counter movement is automatically generated in the optimal explosive activity, using computer simulation. A computer simulation model of the Hill-type muscle tendon complex, which is composed of a contractile element (CE) and a series elastic element (SEE), was constructed. The proximal end of the CE was affixed to a point in the gravitational field, and a massless supporting object was affixed to the distal end of the SEE. An inertia was held on the supporting object. The goal of the explosive activity was to maximize the height reached by the inertia. A variation of the SEE elasticity was examined within the natural range. The optimal pattern of neural activation input was sought through numerical optimization for each value of the SEE elasticity. Two major findings were obtained: (a) As the SEE elasticity increased, the maximal height reached by the inertia increased. This was primarily due to the enhanced force development of the CE. (b) A counter movement was automatically generated for all values of the SEE elasticity through the numerical optimization. It is suggested that it is beneficial to make a counter movement in order to reach a greater jump height, and the effect of making a counter movement increases as the elasticity of the muscle tendon complex increases.

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Robert A. Weinert-Aplin, Anthony M.J. Bull and Alison H. McGregor

Conservative treatments such as in-shoe orthotic heel wedges to treat musculoskeletal injuries are not new. However, weak evidence supporting their use in the management of Achilles tendonitis suggests the mechanism by which these heel wedges works remains poorly understood. It was the aim of this study to test the underlying hypothesis that heel wedges can reduce Achilles tendon load. A musculoskeletal modeling approach was used to quantify changes in lower limb mechanics when walking due to the introduction of 12-mm orthotic heel wedges. Nineteen healthy volunteers walked on an inclinable walkway while optical motion, force plate, and plantar pressure data were recorded. Walking with heel wedges increased ankle dorsiflexion moments and reduced plantar flexion moments; this resulted in increased peak ankle dorsiflexor muscle forces during early stance and reduced tibialis posterior and toe flexor muscle forces during late stance. Heel wedges did not reduce overall Achilles tendon force during any walking condition, but did redistribute load from the medial to lateral triceps surae during inclined walking. These results add to the body of clinical evidence confirming that heel wedges do not reduce Achilles tendon load and our findings provide an explanation as to why this may be the case.

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Marge Taylor

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Steven Malvasi, Brian Gloyeske, Matthew Johnson and Timothy Miller

Background:

Injury to the anterior cruciate ligament (ACL) is one of the most common orthopedic injuries in the United States, while injury to the patellar tendon (PT) is less common. A combined rupture to the ACL and PT is consequentially uncommon and increases the difficulty of a correct initial diagnosis. The purpose of this paper is to critically appraise the current peer-reviewed literature regarding multi-ligamentous knee injuries (MLKI) in sport.

Methods:

A systematic review was undertaken to identify all relevant peer-reviewed articles regarding MLKI from March 1980 to January 2015. All articles pertaining to simultaneous rupture of the ACL and PT were included for review.

Results:

A total of 27 cases presented in 15 articles were used. Findings suggest that the combination of a palpable gap over the PT, a positive Lachman test, inability to complete terminal knee extension, and a superior position of the patella are clinical examination markers for a possible MLKI involving the ACL and PT.

Conclusion:

Simultaneous rupture to the ACL and PT is incredibly rare within the sport population, making diagnosis and treatment of such injury challenging. A thorough examination of the extensor mechanism of the knee is important in making the proper diagnosis.

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Ryota Akagi, Soichiro Iwanuma, Satoru Hashizume, Hiroaki Kanehisa, Toshimasa Yanai and Yasuo Kawakami

The purpose of this study was to investigate how the contraction-induced increase in distal biceps brachii tendon moment arm is related to that in elbow flexor muscle thickness, with a specific emphasis on the influence of the site-related differences in muscle thickness. The moment arm and muscle thickness were determined from sagittal and cross-sectional images, respectively, of the right arm obtained by magnetic resonance imaging of nine young men. The muscle thickness was measured at levels from the reference site (60% of the upper arm length from the acromial process of the scapula to the lateral epicondyle of the humerus) to 60 mm distal to it (every 10 mm; 7 measurement sites). At 80° of elbow flexion, the moment arm and muscle thickness were determined at rest and during 60% of maximal voluntary contraction (60%MVC) of isometric elbow flexion. Only the relative change from rest to 60%MVC in muscle thickness at the level 60 mm distal to the reference site correlated significantly with that of the moment arm. This result indicates that the contraction-induced increase in distal biceps brachii tendon moment arm is related to that in elbow flexor muscle thickness near the corresponding muscle-tendon junction.