Local displacement within the Achilles tendon induced by electrical stimulation of the single gastrocnemius muscles.

BACKGROUND: The Achilles tendon consists of three subtendons, but their functional meaning is still unknown. There are several approaches for the examination in-vivo using sonographic imaging, however, there is no approach for in-vivo examination with respect to the single subtendons of the m. triceps surae. The study's aim was to reveal the single subtendons of the m. triceps surae. METHODS: The Achilles tendon of 17 subjects was analysed. The muscles (m. gastrocnemius lateralis and medialis) were stimulated separately using neuromuscular electrical stimulation. The intensity of muscle contraction was controlled using electromyographic data. Sonographic videos of the Achilles tendon were recorded during muscle contraction. A speckle tracking algorithm was used to analyse the moving areas within the Achilles tendon during the initial phase of contraction. FINDINGS: The muscles were activated at 10-20% of the maximal M-wave. Isolated contraction of m. gastrocnemius lateralis led to local displacement in the lateral part of the Achilles tendon's cross-section whereas isolated contraction of m. gastrocnemius medialis led to displacement in the medial part and to a larger size of the area where initial displacement took place (m. gastrocnemius lateralis to medialis approximately 1:2). INTERPRETATION: The results demonstrate that isolated contractions of m. gastrocnemius lateralis and medialis lead to individual displacements which significantly differ. The differences in position and size of the area of the local displacement indicate an independent individual function. Unlike other studies generally investigating the AT in-vivo using muscle stimulation and ultrasonic imaging, this study investigated the AT's cross-section which had never been investigated before.

Reduced Vastus Medialis/Lateralis EMG Ratio in Volleyballers with Chronic Knee Pain on Sports-Specific Surfaces: A Pilot Study.

BACKGROUND: Even though chronic knee pain is common in volleyball, neuromuscular imbalance as a potential risk factor has not been investigated in volleyball-specific tasks. The aim of the study was to compare neuromuscular control between healthy and injured players in a clinical jump test and a volleyball-specific jump task in real field conditions. METHODS: Six athletes with knee pain and nine controls were included. Surface electromyographic data were recorded from the mm. vastus medialis (VM) and lateralis (VL) of both legs. VM/VL activation ratio was calculated from countermovement jump (CMJ) and volleyball spike indoors and on two beach surfaces. RESULTS: All subjects had pain in the leading leg. Mann-Whitney U Test (M-W-U Test) revealed a significantly lower VM/VL ratio of the leading leg (always affected) of the injured compared with that of the healthy control group for the CMJ and spike jump on all three grounds. Bland-Altman analysis revealed low bias and low difference in standard deviation for the injured leg but high values for the uninvolved leg and healthy controls between tasks and grounds. These results could indicate that neuromuscular control might not adapt too well to different movement tasks and grounds in the injured leg. CONCLUSION: Athletes with chronic knee pain might have lower VM/VL ratios than controls independent from movement task and ground. Neuromuscular control in injured athletes might be less adaptable to new circumstances. The results of neuromuscular control in laboratory settings might be applicable to field conditions in injured legs but not healthy ones.

UC-II Undenatured Type II Collagen for Knee Joint Flexibility: A Multicenter, Randomized, Double-Blind, Placebo-Controlled Clinical Study.

Objective: Joint-related stress models have been used in the past to induce a standardized load on physical structures, allowing researchers to observe changes in perceived stress on joints as accurately as possible in healthy individuals. Previous studies support the efficacy of UC-II® undenatured type II collagen ("undenatured collagen") supplementation in maintaining joint health. The purpose of this study was to assess the effect of undenatured collagen on knee flexibility in healthy subjects who experience activity-related joint discomfort (ArJD). Methods: This randomized, double-blind, placebo (PLA)-controlled study was conducted in healthy subjects with ArJD who had no history of osteoarthritis, or joint diseases. Ninety-six (n = 96, 20-55 years old) subjects who reported joint discomfort while performing a standardized single-leg-step-down test were randomized to receive either PLA (n = 48) or 40 mg of undenatured collagen (n = 48) supplementation daily for 24 weeks. Range of motion (ROM) flexion and extension were measured using a digital goniometer. Results: At the end of the study, a statistically significant increase in knee ROM flexion was observed in the undenatured collagen group versus the PLA group (3.23° vs. 0.21°; p = 0.025). In addition, an increase in knee ROM extension by 2.21° was observed over time in the undenatured collagen group (p = 0.0061), while the PLA group showed a nonsignificant increase by 1.27° (p > 0.05). Subgroup analysis by age showed a significant increase in knee ROM flexion in subjects >35 years old in the undenatured collagen supplemented group compared with PLA (6.79° vs. 0.30°; p = 0.0092). Conclusion: Overall, these results suggest that daily supplementation of 40 mg of undenatured collagen improved knee joint ROM flexibility and extensibility in healthy subjects with ArJD.

Evaluation and Validation of a Joint Stress Test to Induce Activity-Related Knee Joint Discomfort - a Prospective Case-Control Study.

BACKGROUND: The assessment of improvement or maintenance of joint health in healthy subjects is a great challenge. The aim of the study was the evaluation of a joint stress test to assess joint discomfort in subjects with activity-related knee joint discomfort (ArJD). RESULTS: Forty-five subjects were recruited to perform the single-leg-step-down (SLSD) test (15 subjects per group). Subjects with ArJD of the knee (age 22-62 years) were compared to healthy subjects (age 24-59 years) with no knee joint discomfort during daily life sporting activity and to subjects with mild-to-moderate osteoarthritis of the knee joint (OA, Kellgren score 2-3, age 42-64 years). The subjects performed the SLSD test with two different protocols: (I) standardization for knee joint discomfort; (II) standardization for load on the knee joint. In addition, range of motion (ROM), reach test, acute pain at rest and after a single-leg squat and knee injury, and osteoarthritis outcome score (KOOS) were assessed. In OA and ArJD subjects, knee joint discomfort could be reproducibly induced in a short time interval of less than 10 min (200 steps). In healthy subjects, no pain was recorded. A clear differentiation between study groups was observed with the SLSD test (maximal step number) as well as KOOS questionnaire, ROM, and reach test. In addition, a moderate to good intra-class correlation was shown for the investigated outcomes. CONCLUSIONS: These results suggest the SLSD test is a reliable tool for the assessment of knee joint health function in ArJD and OA subjects to study the improvements in their activities. Further, this model can be used as a stress model in intervention studies to study the impact of stress on knee joint health function.

Effects of a 12-week home exercise therapy program on pain and neuromuscular activity in patients with patellofemoral pain syndrome.

INTRODUCTION: The aim of this study is to evaluate the effects of a 12-week home exercise therapy program on pain, function and neuromuscular activity of the vastus medialis and vastus lateralis. MATERIALS AND METHODS: Fifty patients with patellofemoral pain syndrome were treated with a 12-week online home exercise program. The primary outcomes of pain and function were assessed at the 12-week follow-up using the Visual Analog Scale and Kujala Score, respectively. Secondary outcomes were the muscle onset time and the ratio of vastus medialis and vastus lateralis during different daily activities. RESULTS: After 12 weeks, patients showed significant (p < 0.05) improvements of 27 points on the Visual Analog Scale and 10 points on Kujala Score. Differences in pre-post comparison regarding both temporal and amplitude-related neurophysiological differences between the vastus medialis and lateralis were only found when the subjects were divided into groups of different electromyographic patterns. Then changes in the pre-post comparison were particularly evident in the patient group with a delayed vastus medialis onset and a lower activity of the vastus medialis compared to the VL. CONCLUSION: Pain and function improved significantly after a home exercise therapy program in patients with patellofemoral pain syndrome. In addition, patients with a delayed onset or reduced activity of the vastus medialis compared to the vastus lateralis experienced a reduction in this imbalance.

Immediate effects of an elastic patellar brace on pain, neuromuscular activity and knee kinematics in subjects with patellofemoral pain.

INTRODUCTION: The aim of this randomized controlled trial was to investigate immediate effects of a patellar brace on pain, neuromuscular activity, and knee kinematics in subjects with patellofemoral pain syndrome. MATERIALS AND METHODS: Fifty subjects with a diagnosis of patellofemoral pain syndrome completed 6 activities each with and without a patellar brace in a randomized order. The subjects were asked to rate their perceived pain on a Visual Analog Scale after each activity. During the activities, neuromuscular activity of vastus medialis and vastus lateralis, as well as knee angles were measured. RESULTS: Subjects showed a statistically significant pain reduction of 33-56% on the Visual Analog Scale during all activities while wearing the brace. Two groups with different onset patterns for vastus medialis and vastus lateralis were identified: one group who activated vastus medialis prior to vastus lateralis, and one who activated vastus medialis after vastus lateralis. In the subgroup of subjects activating vastus lateralis prior to vastus medialis, bracing resulted in a significantly (p = 0.048) earlier onset of vastus medialis by 56 ms. In all but one activity, the vastus medialis/vastus lateralis ratio without the patellar brace was < 1.0 and inverted with the patellar brace > 1.0. Knee angles in the sagittal plane increased significantly with the patellar brace in two activities. CONCLUSION: Patellofemoral bracing results in an immediate decrease of pain, an earlier onset of vastus medialis and inverted vastus medialis/vastus lateralis ratio and altered knee kinematics.

Weekly Time Course of Neuro-Muscular Adaptation to Intensive Strength Training.

Detailed description of the time course of muscular adaptation is rarely found in literature. Thus, models of muscular adaptation are difficult to validate since no detailed data of adaptation are available. In this article, as an initial step toward a detailed description and analysis of muscular adaptation, we provide a case report of 8 weeks of intense strength training with two active, male participants. Muscular adaptations were analyzed on a morphological level with MRI scans of the right quadriceps muscle and the calculation of muscle volume, on a voluntary strength level by isometric voluntary contractions with doublet stimulation (interpolated twitch technique) and on a non-voluntary level by resting twitch torques. Further, training volume and isokinetic power were closely monitored during the training phase. Data were analyzed weekly for 1 week prior to training, pre-training, 8 weeks of training and 2 weeks of detraining (no strength training). Results show a very individual adaptation to the intense strength training protocol. While training volume and isokinetic power increased linearly during the training phase, resting twitch parameters decreased for both participants after the first week of training and stayed below baseline until de-training. Voluntary activation level showed an increase in the first 4 weeks of training, while maximum voluntary contraction showed only little increase compared to baseline. Muscle volume increased for both subjects. Especially training status seemed to influence the acute reaction to intense strength training. Fatigue had a major influence on performance and could only be overcome by one participant. The results give a first detailed insight into muscular adaptation to intense strength training on various levels, providing a basis of data for a validation of muscle fatigue and adaptation models.

Fatigue detection in strength training using three-dimensional accelerometry and principal component analysis.

Detection of neuro-muscular fatigue in strength training is difficult, due to missing criterion measures and the complexity of fatigue. Thus, a variety of methods are used to determine fatigue. The aim of this study was to use a principal component analysis (PCA) on a multifactorial data-set based on kinematic measurements to determine fatigue. Twenty participants (strength training experienced, 60% male) executed 3 sets of 3 exercises with 50 (12 repetitions), 75 (12 repetitions) and 100%-12 RM (RM). Data were collected with a 3D accelerometer and analysed by a newly developed algorithm to evaluate parameters for each repetition. A PCA with six variables was carried out on the results. A fatigue factor was computed based on the loadings on the first component. One-way ANOVA with Bonferroni post hoc analysis was calculated to test for differences between the intensity levels. All six input variables had high loadings on the first component. The ANOVA showed a significant difference between intensities (p < 0.001). Post-hoc analysis revealed a difference between 100% and the lower intensities (p < 0.05) and no difference between 50 and 75%-12RM. Based on these results, it is possible to distinguish between fatigued and non-fatigued sets of strength training.

Effect of Footwear Modifications on Oscillations at the Achilles Tendon during Running on a Treadmill and Over Ground: A Cross-Sectional Study.

BACKGROUND: Achilles tendon injuries are known to commonly occur in runners. During running repeated impacts are transferred in axial direction along the lower leg, therefore possibly affecting the oscillation behavior of the Achilles tendon. The purpose of the present study was to explore the effects of different footwear modifications and different ground conditions (over ground versus treadmill) on oscillations at the Achilles tendon. METHODS: Oscillations were measured in 20 male runners using two tri-axial accelerometers. Participants ran in three different shoe types on a treadmill and over ground. Data analysis was limited to stance phase and performed in time and frequency space. Statistical comparison was conducted between oscillations in vertical and horizontal direction, between running shoes and between ground conditions (treadmill versus over ground running). RESULTS: Differences in the oscillation behavior could be detected between measurement directions with peak accelerations in the vertical being lower than those in the horizontal direction, p < 0.01. Peak accelerations occurred earlier at the distal accelerometer than at the proximal one, p < 0.01. Average normalized power differed between running shoes (p < 0.01) with harder damping material resulting in higher power values. Little to no power attenuation was found between the two accelerometers. Oscillation behavior of the Achilles tendon is not influenced by ground condition. CONCLUSION: Differences in shoe configurations may lead to variations in running technique and impact forces and therefore result in alterations of the vibration behavior at the Achilles tendon. The absence of power attenuation may have been caused by either a short distance between the two accelerometers or high stiffness of the tendon. High stiffness of the tendon will lead to complete transmission of the signal along the Achilles tendon and therefore no attenuation occurs.

Relationship between muscle volume and contractile properties of the human knee extensors.

The present study was designed to investigate the relationship between volume and electrically evoked twitch properties of the quadriceps muscle. Supramaximal single and doublet stimulation of the femoral nerve was used to assess contractile properties at 45° and 80° knee flexion. Muscle volume was measured using a 1.5-Tesla magnetic resonance imaging scanner. Quadriceps muscle volume was only significantly correlated (r = 0.629) with peak twitch torque induced by doublet stimulation at 80° but not at 45° knee flexion.

Reduced muscular fatigue after a 12-week leucine-rich amino acid supplementation combined with moderate training in elderly: a randomised, placebo-controlled, double-blind trial.

BACKGROUND: Age-related muscle loss is characterised by a progressing decrease in muscle mass, strength and function. Besides resistance training and physical activity, appropriate nutrition that is rich in protein, especially branched-chain amino acids, is very important to support training effects and positively influence the protein synthesis to degradation ratio. AIM: The purpose of this study was to evaluate the effect of a 12-week leucine-rich amino acid supplementation in combination with moderate training. METHODS: Forty-eight healthy subjects exercised for 30 min three times per week and received either a leucine-rich amino acid supplementation or a placebo. Before and after supplementation, volunteers performed an exhaustive eccentric exercise protocol. Maximal concentric strength, muscle soreness, creatine kinase (CK), type II collagen collagenase cleavage neoepitope (C2C), C propeptide of type II procollagen (CP2) and safety assessments were performed before exercise and after 3, 24, 48 and 72 hours. RESULTS: The supplementation with leucine resulted in reduced loss of strength at 0 and 3 hours after downhill walking compared with the placebo (p=0.0439). The reduction of C2C/CP2 ratio deflection was significantly increased (p=0.038) due to leucine compared with the placebo. The same tendency could be observed for the recovery phase. No significant supplement effects for muscle soreness and CK could be observed. CONCLUSION: The principle findings show that leucine-rich amino acid supplementation can counteract the negative effects of eccentric exercise. The treatment resulted in a reduction of exercise-induced strength loss.

Spatial orientation of the subtalar joint axis is different in subjects with and without Achilles tendon disorders.

BACKGROUND: There are many possible predisposing factors for Achilles tendon disorders suggested in the literature but their pathogenetic relevance is not proven in most cases. The asymmetric mechanical load distribution within the Achilles tendon during locomotion is frequently addressed as a major risk factor for Achilles tendon disorders. The spatial orientation of the subtalar joint axis (STA) may influence the Achilles tendon loading possibly leading to overload injuries. Hypothesis There is a significant difference between the orientation of the STA in subjects with and without Achilles tendon pathologies. MATERIALS AND METHODS: 614 subtalar joint axes determined in 307 long-distance runners with and without Achilles tendon disorders were included. Achilles tendon disorders were defined as any Achilles tendon-related pain during or following running, existing for more than 2 weeks in the past. Motion analysis of the foot was performed using an ultrasonic pulse-echo-based measurement system. The orientation of the STA was expressed by two angles. RESULTS: The mean inclination angle was 42 ± 16° and the mean deviation angle was 11 ± 2 3°. There was a significant difference (p=0.002) between the mean deviation angle measured in subjects with Achilles tendon pathologies (18 ± 23°) and those without (10 ± 23°). CONCLUSIONS: The results demonstrate a wide interindividual variability of the spatial orientation of the STA. In addition, the mean deviation angle in people with Achilles tendon pathologies is significantly more oblique than in people without. This finding indicates that the spatial orientation of the STA is related to the incidence of overuse injuries of the Achilles tendon in the investigated sample.

Novel approach for a precise determination of short-time intervals in ankle sprain experiments.

The etiology of ankle sprain injury is still under debate. Therefore, diagnoses of ankle inversion experiments play an important role. Recent studies stress the importance of exact time measurements due to the short inversion period of around 70ms. This paper presents a novel approach using the vertical ground reaction force (vGRF) to determine the short-time intervals in ankle sprain experiments, which are present in the form of short periods from the beginning of the movement to its end and short latencies to following signals, e.g. EMG onset of peroneal muscles. We compare our method to electrogoniometry at the ankle which is considered as the gold standard. During the inversion movement the kinematic action at the ankle can be measured with electrogoniometry, whereas the vGRF quantifies the vertical dynamic reaction of the tested subject entirely. We observe a difference of DeltaT(f,0-->g,0)=10+/-0.5ms between the first observable vGRF response and the first observable electrogoniometer response following platform release. The end of the ankle inversion measured with electrogoniometry is DeltaT(f,1-->g,1)=3+/-0.5ms later than the maximal vGRF peak. The potential supplementary (mechanical) information of this novel approach compared to electrogoniometry and its ease of use, may be not only interesting for researchers when studying ankle sprain simulations but also for clinicians when testing functional ankle stability.