Muscle Fascicle Length Research Articles

Identification of muscle morphology with noncontact capacitive sensing: Preliminary study.

Human-machine interface with muscle signals serves as an important role in the field of wearable robotics. To compensate for the limitations of the existing surface Electromyography (sEMG) based technologies, we previously proposed a noncontact capacitive sensing approach that could record the limb shape changes. The sensing approach frees the human skin from contacting to the metal electrodes, thus enabling the measurement of muscle signals by dressing the sensing front-ends outside of the clothes. We validated the capacitive sensing in human motion intent recognition tasks with the wearable robots and produced comparable results to existing studies. However, the biological significance of the capacitance signals is still unrevealed, which is an indispensable issue for robot intuitive control. In this study, we address the problems of identifying the relationships between the muscle morphological parameters and the capacitance signals. We constructed a measurement system that recorded the noncon-tact capacitive sensing signals and the muscle ultrasound (US) images simultaneously. With the designed device, five subjects were employed and the US images from the gastrocnemius muscle (GM) and the tibialis anterior (TA) muscle during level walking were sampled. We fitted the calculated muscle morphological parameters (the pinnation angles and the muscle fascicle length) and the capacitance signals of the same gait phases. The results demonstrated that at least one-channel capacitance signal strongly correlated to the muscle morphological parameters (R2 > 0.5, quadratic regression). The average R2s of the most correlated channels were up to 0.86 for pinnation angles and 0.83 for the muscle fascicle length changes. The interesting findings in this preliminary study suggest the biological physical significance of the capacitance signals during human locomotion. Future efforts are worth being paid in this new research direction for more promising results.

Effect of Weekly Training Frequency With the Nordic Hamstring Exercise on Muscle-Strain Risk Factors in Football Players: A Randomized Trial.

To examine the differences between performing Nordic hamstring exercises once or twice a week on hamstring eccentric strength and other muscle-strain risk factors in high-level football players. In this randomized trial, 32 football players (18-23 y old) completed an 8-week Nordic hamstring exercise training program in 1 of 2 experimental groups: group 1 (once a week; n = 15) and group 2 (twice a week; n = 17). Knee-flexor/extensor peak torques and biceps femoris long-head muscle architecture were assessed through isokinetic dynamometry and ultrasonography, respectively, before and after the training programs. Analysis of covariance, effect sizes (ESs), and t tests for percentage change were used to assess the effect of the 2 interventions on the outcome measures. Group 2 demonstrated higher hamstring concentric peak torque than group 1 posttraining (155-164 vs 149-158N·m; P = .043; ES = 0.27), although there was also a statistical trend for higher hamstring eccentric peak torque (212-234 vs 198-221N·m; P = .098; ES = 0.37), hamstring-to-quadriceps conventional ratio (0.56-0.59 vs 0.54-0.57; P = .089; ES = 0.31), and hamstring-to-quadriceps functional ratio (0.76-0.84 vs 0.71-0.79; P = .076; ES = 0.50). No between-groups differences were found for muscle thickness (P = .864; ES = 0.12), pennation angle (P = .289; ES = 0.18), fascicle length (P = .406; ES = 0.03), and quadriceps concentric peak torque (P = .340; ES = 0.02). Only the Nordic hamstring exercise training program performed twice a week strengthened the hamstrings of high-level football players, while similar changes in muscle architecture occurred with both once- and twice-weekly sessions.

Ultrasound analyses of hamstrings muscle morphology changes whit sport

Abstract Introduction Physical activities and sports can change muscle morphology. Changes caused by regular physical exercise can be assessed by ultrasound parameters such as the pennation angle, cross-sectional area, echo-intensity and muscle thickness. Objectives This study aims to characterise and evaluate the morphological changes of the hamstring muscles through ultrasound parameters such as the pennation angle, fascicle length, cross-sectional area, echo-intensity and muscle thickness, and verify the existence of morphological changes between the dominant and non-dominant limb. Methodology Twenty-two young female divided in two groups (control group=11; athletes group=11) were submitted to an ultrasound examination at 50% of the posterior region of the thigh, for the semimembranosus and long portion of the femoral biceps muscles in the longitudinal and in a panoramic view. Results 22 athletes with a mean age of 22.25 years were evaluated. There were significant differences between the two groups in muscle morphology. The athletes group showed a higher value for muscle thickness, cross-sectional area, pennation angle and fascicle length and a lower value for muscle echo-intensity. This group also showed higher values for these parameters when dominant limb is compared with non-dominant. Conclusion Physical exercise causes changes in muscle morphology and ultrasound is a good method for the musculoskeletal assessment of athlete’s performance, since it is an imaging modality that allows to carry out comparative bilateral studies for athletes performance follow up and for preventive strategies against the sedentarism.

Does resistance training increase aponeurosis width? The current results and future tasks.

The aponeurosis, a sheet of fibrous tissue, is the deep and superficial fascia where muscle fibers attach in pennate muscles. It is quite possible that the aponeurosis size increases in response to resistance training-induced fiber hypertrophy due to an increase in connection area. As a result, it leads to an increase in anatomical muscle cross-sectional area. However, attention has not been paid to aponeurosis area changes. This review sought to determine whether muscle hypertrophy changes aponeurosis width following short-term resistance training using an equation we modified [post/pre changes in aponeurosis width (AWpost/pre) = post/pre changes in anatomical cross-sectional area (CSApost/pre) ÷ post/pre changes in pennation angle (PApost/pre) ÷ post/pre changes in fascicle length (FLpost/pre)]. A search using two electronic databases (PubMed and Google Scholar) was conducted. Nine studies measured CSApost/pre, PApost/pre, and FLpost/pre of the vastus lateralis muscle by ultrasound and magnetic resonance imaging. There was a statistically significant 2.73 [95% CI 1.11, 4.36; p = 0.009] cm2 increase in CSApost/pre along with a statistically significant 1.21° [95% CI 0.44, 1.97; p = 0.002] increase in PApost/pre and a statistically significant 0.36cm [95% CI 0.19, 0.54; p = 0.0002] increase in FLpost/pre. These results yield an estimated 1% reduction in aponeurosis width. Our results suggest that while muscle CSA, pennation angle, and fascicle length all increase following short-term resistance training, the aponeurosis width is not altered.

Quadriceps muscle properties in rheumatoid arthritis: insights about muscle morphology, activation and functional capacity

BackgroundRheumatoid arthritis (RA) is an inflammatory and chronic autoimmune disease that leads to muscle mass loss and functional capacity impairment, potentiated by physical inactivity. Despite evidences demonstrate neuromuscular impairments in RA patients, aging effects may have masked the results of similar previous studies. The aim of study was to verify (i) the effects of RA on functional capacity and muscle properties in middle-aged patients and (ii) the association between age, clinical characteristics, quadriceps muscle properties and functional capacity.MethodsThirty-five RA women and 35 healthy age-matched women were compared with the following outcomes: (i) physical activity level through the International Physical Activity Questionnaire (IPAQ); (ii) timed-up and go (TUG) test; (iii) isometric knee extensor muscular strength; and (iv) vastus lateralis muscle activation and muscle architecture (muscle thickness, pennation angle and fascicle length) during an isometric test. An independent Student t-test and partial correlation (controlled by physical activity levels) were performed, with p < 0.05.ResultsCompared with healthy women, RA presented (i) lower physical activity level (− 29.4%; p < 0.001); (ii) lower isometric knee extensor strength (− 20.5%; p < 0.001); (iii) lower TUG performance (− 21.7%; p < 0.001); (iv) smaller muscle thickness (− 23.3%; p < 0.001) and pennation angle (− 14.1%; p = 0.011). No differences were observed in muscle activation and fascicle length. Finally, the correlation demonstrated that, with exception of TUG, muscle strength and muscle morphology were not associated with age in RA, differently from healthy participants.ConclusionMiddle-aged RA patients’ impairments occurred due to the disease independently of the aging process, except for functional capacity. Physical inactivity may have potentiated these losses.

Review of the methods used for calculating physiological cross-sectional area (PCSA) for ecological questions.

This review examines literature that used physiological cross-sectional area (PCSA) as a representative measure of an individual muscle's maximal isometric force production. PCSA is used to understand the muscle architecture and how a trade-off between muscle force and muscle contractile velocity reflect adaptations of the musculoskeletal system as a reflection of functional demands. Over the decades, methods have been developed to measure muscle volume, fascicle lengths, and pennation angle to calculate PCSA. The advantages and limitations of these methods (especially the inclusion/elimination of pennation angle) are discussed frequently; however, these method descriptions are scattered throughout the literature. Here, we reviewed and summarised the different approaches to collecting and recording muscle architectural properties to subsequently calculate PCSA. By critically discussing the advantages and limitations of each methodology, we aim to provide readers with an overview of repeatable methods to assess muscle architecture. This review may serve as a guide to facilitate readers searching for the appropriate techniques to calculate PCSA and measure muscle architecture to be applied in ecomorphology research. RESEARCH HIGHLIGHTS: Discuss the theories behind PCSA in a synthesised review to inform researchers about PCSA methodology.

Vastus intermedius muscle architecture predicts the late phase of the knee extension rate of force development in recreationally resistance-trained men

ObjectivesThe current study investigated the correlation between quadriceps muscle architecture and the knee extension rate of force development (RFD). Designcross-sectional study. MethodsMuscle thickness, pennation angle and fascicle length normalized per the thigh-length were measured via ultrasound in vastus lateralis, rectus femoris, vastus intermedius and vastus medialis. The knee extension rate of force was assessed isometrically at 90° knee angle and calculated in different 50-ms epochs (0−50, 50−100, 100−150, 150−200 and 200−250ms). The maximum voluntary contraction was also recorded. ResultsLarge correlations were observed between vastus intermedius muscle thickness and the 100−150ms (r=0.694, p=0.004), 150−200ms (r=0.597, p=0.019) and 200−250ms (r=0.546, p=0.045) epochs. Large correlation was observed between vastus intermedius normalized fascicle length and 100−150ms (r=0.570, p=0.043) and large correlations with 150−200ms (r=0.643, p=0.010) and 200−250ms (r=0.629, p=0.012) epochs. Additionally, large correlations were observed between vastus lateralis normalized fascicle length and the 100−150ms (r=0.535, p=0.049), 150−200ms (r=0.629, p=0.016) and 200−250ms (r=0.563, p=0.046) epochs. Vastus intermedius muscle thickness predicted 59% (R2=0.581, p=0.002) of the RFD of the 100−150ms epoch; vastus intermedius muscle thickness and fascicle length predicted 51% (R2=0.506, p=0.029) of the 150−200ms epoch; vastus intermedius and vastus lateralis fascicle length predicted 48% (R2=0.483, p=0.037) of the 200−250ms epoch. No further correlation was observed. ConclusionsFascicle length and muscle thickness were observed as predictive of the late phase of the rate of force development. Vastus intermedius muscle architecture has a primary role in the knee extension RFD.

Effects of Blood Flow Restriction Training on Muscle Strength and Architecture.

Korkmaz, E, Dönmez, G, Uzuner, K, BabayevaŞerife Şeyma Torgutalp, N, and Özçakar, L. Effects of blood flow restriction training on muscle strength and architecture. J Strength Cond Res XX(X): 000-000, 2020-The aim of this study was to compare the effect of the traditional resistance (RES) training and low-intensity resistance training with blood flow restriction (BFR) protocols on quadriceps and hamstring muscle strength, and rectus femoris (RF) and vastus lateralis architecture, in youth team soccer players. Twenty-three young trained soccer team players were divided into 2 groups: the RES group that practiced traditional high-intensity resistance training (80% 1 repetition maximum [1RM], 4 sets, 12 rep.) (n = 12) and the BFR group that performed low-intensity resistance exercise with BFR (30% 1RM, 4 sets, 30-15-15-15 rep) (n = 11)-unilateral knee extension exercise-twice a week for 6 weeks. Muscle strength (isokinetic concentric peak torque of the quadriceps and hamstring muscles) and ultrasonographic parameters (muscle thickness, pennation angle, and fascicle length) were assessed. Bilateral knee flexor and extensor strength was increased in both groups compared with pre-exercise. The increase in dominant side extensor muscle strength (60°·s p = 0.02, ηp = 0.256, 180°·s p = 0.019, ηp = 0.271) and RF thickness (p = 0.002, ηp = 0.361) was statistically higher in the BFR group than in the RES group. These findings support that occlusion training can provide better benefits than traditional strength training to improve muscle hypertrophy. In addition, the novelty of our study is that BFR training may affect the muscle structure measured by ultrasonography.

Structural and molecular analysis of elbow flexor muscles in modern humans and common chimpanzees

In the present study we calculated the muscle fascicle length (MFL) and the physiological cross-sectional area (PCSA) in the elbow flexor muscles of five Homo sapiens and five Pan troglodytes. We also assessed the expression of the myosin heavy chain (MyHC) isoforms with real-time quantitative polymerase chain reaction in the same muscles and, finally, we analyzed the muscle insertion sites in the proximal epiphyses of the ulna and the radius with 3D geometric morphometrics. Our main objective is to identify quantitative differences in the elbow flexor muscles of Homo sapiens and Pan troglodytes in terms of muscle architecture, expression of MyHC isoforms, and bone insertion sites and to explore the association of these differences with the types of locomotion developed by these two species of hominoid primates. We observed that the elbow flexor muscles had a greater PCSA and a higher expression of the fast MyHC-II isoforms in Pan troglodytes, while they had a greater MFL and a higher expression of the slow MyHC-I isoform in Homo sapiens. The insertion site of the brachialis was larger in Pan troglodytes, while that of the biceps brachii was larger in Homo sapiens. Our findings may be related to the greater capacity of force generation in the elbow flexor muscles of Pan troglodytes, as an adaptation to vertical climbing, and to the greater contraction speed and resistance to fatigue of the muscles in Homo sapiens, as an adaptation to the manipulative function of the upper extremities.

Effects of Self-Massage Using a Foam Roller on Ankle Range of Motion and Gastrocnemius Fascicle Length and Muscle Hardness: A Pilot Study.

Several studies have reported that self-massage using a foam roller (FR) increased joint range of motion (ROM) immediately. However, the mechanism of increasing ROM by the FR intervention has not been elucidated. To clarify the mechanism by investigating properties and morphological changes of muscles targeted by the FR intervention. An interventional study. An athletic training laboratory. Ten male college volunteers with no injuries in their lower limbs (mean [SD]: age 23.8 [3.2]y, height 173.2 [4.9]cm, weight 69.5 [8.6]kg). The FR intervention on the right plantar flexors for 3 minutes. Maximum ankle ROM, muscle hardness, and fascicle length of the gastrocnemius muscle at the neutral (0°), maximum dorsiflexion, and maximum plantar flexion positions. All measurements were conducted before (PRE) and after (POST) the FR intervention. Dorsiflexion ROM increased significantly at POST (PRE: 13.6° [8.0°], POST: 16.6° [8.4°]; P < .001), although plantar flexion ROM did not change significantly between PRE and POST (PRE: 40.0° [6.1°], POST: 41.1° [4.9°]). There was no significant difference in muscle hardness and fascicle length between PRE and POST in any of the angles. Dorsiflexion ROM increased significantly by the FR intervention in the present study; however, muscle hardness and fascicle length did not change. FR may affect not only the muscle but also the fascia, tendon, and muscle-tendon unit. The FR protocol of the present study can be applied in clinical situations, because it was found to be effective to increase ROM.

Low frequency fatigue and changes in muscle fascicle length following eccentric exercise of the knee extensors.

What is the central question of this study? Does low frequency muscle fatigue indicate a failure of excitation-contraction coupling after eccentric exercise, or is it simply due to a change in muscle length? What is the main finding and its importance? The low to high frequency muscle fatigue ratio was relatively insensitive to changes in muscle length, and any changes in length following eccentric exercise were far too small to account for the high degree of low frequency fatigue. The results strengthen the suggestion that the early loss of force following eccentric exercise is due to a deficit of excitation-contraction coupling. Development of long lasting fatigue (low frequency fatigue; LFF), assessed as the ratio of forces at 20 and 100Hz stimulation, suggests the early phase of muscle damage caused by eccentric exercise is due to a deficit of excitation-contraction coupling. However, this could be caused by a change of muscle length. Eleven men (21.3±2.0years) performed 200 maximum eccentric knee extensions (30-110deg flexion). Force generated by 20 and 100Hz stimulation and maximum isometric force (MIF) were determined at knee angles 50, 70 and 90deg before and immediately after the exercise. Vastus lateralis fascicle length (FL) was measured by ultrasound of resting and contracting muscle. Peak MIF (829±119N) was at 70deg knee flexion, falling to 486±180N (P<0.001) after exercise, but with no change in optimum angle. FLs at rest were unaffected by eccentric exercise, but during contraction they were on average 8.8% (95% CI: 4.1, 13.5%, P=0.002) longer after exercise. Before exercise, the 20/100 ratio increased with muscle length, from 0.69±0.09 at 50deg, 0.72±0.05 at 70deg and 0.80±0.08 at knee angle 90deg (P<0.001). After eccentric exercise the 20/100 ratio was reduced to 0.29±0.08 at 50deg, 0.27±0.04 at 70deg and 0.34±0.04 at 90deg (P<0.001). The 20/100 ratio was relatively insensitive to changes in muscle length and the decrease following eccentric exercise was far greater than might be caused by any changes in muscle length after eccentric exercise. The results show that LFF following eccentric exercise is not due to change in muscle length and strengthen the suggestion that it represents a deficit in excitation-contraction coupling.

Effects of eccentric exercise on the quadriceps architecture

To determine the muscle architecture adaptations in the vastus lateralis (VL) and vastus medialis (VM) after an eccentric training programme based on the Reverse Nordic Hamstring Exercise (RNHE) and after a subsequent detraining period. The participants ( N = 28) underwent a 12-week intervention, consisting of one week of assessment and familiarisation, followed by seven weeks of eccentric training and four weeks of detraining. The VL and VM muscle architecture features were assessed in resting conditions by means of 2D ultrasonography before (week 1) and after (week 8) the training period, as well as after the detraining period (week 12). Significant increases in the VL and VM muscle fascicle length (FL) ( t = − 5.06, d = 1.43, P < 0.05 and t = − 11.14, d = 3.09, P < 0.001, respectively), muscle thickness (MT) ( t = − 5.0, d = 1.39, P < 0.05 and t = − 6.17, d = 1.71, P < 0.05) and pennation angle (PA) ( t = − 6.77, d = 1.88, P < 0.05 and t = − 4.48, d = 1.25, P < 0.05) were observed after the training period. The FL, MT and PA showed a significant decrease after the detraining period. The results provide evidence that an eccentric training programme based on the RNHE may lead to changes in the VL and VM muscle architecture features, which are reversible after a four-week detraining period. Déterminer les adaptations de l’architecture musculaire de la vastus lateralis (VL) et vastus medialis (VM) après un programme d’entraînement excentrique basé sur le jarret nordique inversé (JNI) et après une période de formation ultérieure. Les participants ( n = 28) ont subi une intervention de 12 semaines comprenant une semaine d’évaluation et de familiarisation, suivie de sept semaines de formation excentrique et de quatre semaines de formation. Les caractéristiques de l’architecture musculaire de la LV et de la VM ont été évaluées au repos au moyen d’une échographie 2D avant (semaine 1) et après (semaine 8) la période d’entraînement, ainsi qu’après la période d’entraînement (semaine 12). Augmentations significatives de la longueur du fascicule musculaire VL et VM (FL) ( t = − 5,06, d = 1,43, p < 0,05 et t = − 11,14, d = 3,09, p < 0,001, respectivement), de l’épaisseur musculaire (MT) = − 5,0, d = 1,39, p < 0,05 et t = − 6,17, d = 1,71, p < 0,05) et l’angle de pennation (PA) ( t = − 6,77, d = 1,88, p < 0,05 et t = − 4,48, d = 1,25, p < 0,05) ont été observés après la période d’entraînement. Le FL, le MT et le PA ont montré une diminution significative après la période de détrainage. Les résultats démontrent qu’un programme d’entraînement excentrique basé sur le RNHE peut entraîner des modifications des caractéristiques de l’architecture musculaire de la LV et de la VM, qui sont réversibles après une période de formation de quatre semaines.

Effect of chronic stretching interventions on the mechanical properties of muscles in patients with stroke: A systematic review.

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.

Shorter gastrocnemius fascicle lengths in older adults associate with worse capacity to enhance push-off intensity in walking

BackgroundReduced push-off intensity during walking is thought to play an important role in age-related mobility impairment. We posit that an age-related shift toward shorter plantarflexor operating lengths during walking functionally limits force generation, and thereby the ability of those muscles to respond to increased propulsive demands during walking. Research QuestionTo determine whether gastrocnemius muscle fascicle lengths during normal walking: (1) are shorter in older than young adults, and (2) correlate with one’s capacity to increase the propulsive demands of walking to their maximum. MethodsWe used in vivo cine B-mode ultrasound to measure gastrocnemius fascicle lengths in 9 older and 9 young adults walking at their preferred speed, their maximum speed, and with horizontal impeding forces that increased in a ramped design at 1%BW/s to their maximum. A repeated measures ANOVA tested for effects of age and walking condition, and Pearson correlations assessed the relation between fascicle outcomes and condition performance. ResultsA tendency toward shorter medial gastrocnemius muscle fascicle lengths in older versus young adults was not statistically significant. However, older adults walked with reduced peak fascicle shortening during all conditions compared to young adults – an outcome not explained by reduced muscle-tendon unit shortening and exacerbated during tasks with greater than normal propulsive demand. As hypothesized, we found a strong and significant positive correlation in older subjects between gastrocnemius fascicle lengths during normal walking and performance on the ramped impeding force condition (p = 0.005, r² = 0.704), even after controlling for isometric strength (p = 0.011, r² = 0.792) and subject stature (p = 0.010, r² = 0.700). SignificanceOur findings provide muscle-level insight to develop more effective rehabilitation techniques to improve push-off intensity in older adults and assistive technologies designed to steer plantarflexor muscle fascicle operating behavior during functional tasks.

Effect of resistance training to muscle failure vs non-failure on strength, hypertrophy and muscle architecture in trained individuals.

The aim of this study was to compare the effects of resistance training to muscle failure (RT-F) and non-failure (RT-NF) on muscle mass, strength and activation of trained individuals. We also compared the effects of these protocols on muscle architecture parameters. A within-subjects design was used in which 14 participants had one leg randomly assigned to RT-F and the other to RT-NF. Each leg was trained 2 days per week for 10 weeks. Vastus lateralis (VL) muscle cross-sectional area (CSA), pennation angle (PA), fascicle length (FL) and 1-repetition maximum (1-RM) were assessed at baseline (Pre) and after 20 sessions (Post). The electromyographic signal (EMG) was assessed after the training period. RT-F and RT-NF protocols showed significant and similar increases in CSA (RT-F: 13.5% and RT-NF: 18.1%; P < 0.0001), PA (RT-F: 13.7% and RT-NF: 14.4%; P < 0.0001) and FL (RT-F: 11.8% and RT-NF: 8.6%; P < 0.0001). All protocols showed significant and similar increases in leg press (RT-F: 22.3% and RT-NF: 26.7%; P < 0.0001) and leg extension (RT-F: 33.3%, P < 0.0001 and RT-NF: 33.7%; P < 0.0001) 1-RM loads. No significant differences in EMG amplitude were detected between protocols (P > 0.05). In conclusion, RT-F and RT-NF are similarly effective in promoting increases in muscle mass, PA, FL, strength and activation.

Relationships Between Muscle Architecture, Deadlift Performance, and Maximal Isometric Force Produced at the Midthigh and Midshin Pull in Resistance-Trained Individuals.

Bartolomei, S, Rovai, C, Lanzoni, IM, and di Michele, R. Relationships between muscle architecture, deadlift performance, and maximal isometric force produced at the midthigh and midshin pull in resistance-trained individuals. J Strength Cond Res 36(2): 299-303, 2022-The aim of this study was to investigate the relationships between muscle architecture, lower-body power, and maximal isometric force produced at midthigh pull (MTP), and at midshin pull (MSP). Twenty experienced resistance-trained men (age = 25.5 ± 3.2 years; body mass = 86.9 ± 12.4 kg; body height = 178.0 ± 5.3 cm) were tested for deadlift 1 repetition maximum (1RM), countermovement jump (CMJ), peak force (PF), and rate of force development (pRFD20) produced at isometric MTP and isometric MSP. Subjects were also assessed for architecture of vastus lateralis (VL). Physiological muscle thickness, pennation angle, and fascicle length (FL) were measured. Pearson's correlation coefficients were calculated to assess the relationships between variables. In addition, differences between MTP and MSP were assessed using paired-sample t-tests. A significant (p < 0.05) difference was detected on the correlation between deadlift 1RM and MSP (r = 0.78; p < 0.001) compared with MTP (r = 0.55; p = 0.012). Moderate correlations were observed between MSP PF and VLFL (r = 0.55; p = 0.011). Midshin pull pRFD20 was the only parameter significantly correlated with CMJ (r = 0.50; p = 0.048). Significantly higher PF and pRFD20 were recorded in MTP compared with MSP (p = 0.007 and p = 0.003, respectively). The present results show that force produced from the floor position may be more important than force produced from a position that mimics the second pull of the clean for deadlift and vertical jump performances. Coaches and scientific investigators should consider using MSP to assess isometric PF using a test correlated with both muscle architecture and dynamic performances.

Do Stretch-Shortening Cycles Really Occur in the Medial Gastrocnemius? A Detailed Bilateral Analysis of the Muscle-Tendon Interaction During Jumping.

The effect of stretch-shortening cycles (SSCs) is often studied in laboratory settings, yet it remains unclear whether highly active muscle SSCs actually occur during in vivo movement. Nine highly trained jumping athletes performed single-leg pre-hop forward jumps at maximal effort. We hypothesized that these jumps would induce a SSC at the level of the muscle in the medial gastrocnemius. Kinematic and kinetic data were collected together with electromyography signals (EMG) and muscle fascicle length and pennation angle changes of the medial gastrocnemius of both legs and combined with a musculoskeletal model to calculate the stretch-shortening behavior of the muscle (fascicles) and tendon (series-elastic element). The length changes of the fascicles, longitudinal muscle displacement, series-elastic element, and whole muscle-tendon unit further allowed for a detailed analysis of the architectural gearing ratio between different phases of the SSC within a single movement. We found a SSC at the level of the joint, muscle-tendon unit and tendon but not at the muscle. We further found that the average architectural gearing ratio was higher during the stretching of the series-elastic element as compared to when the series-elastic element was shortening, yet this was not statistically tested because of low sample size for this parameter. However, we found no correlation when plotting the architectural gearing ratio as a function of the fascicle velocities at each instance in time. Despite the athletes having a clear preferred leg for jumping, we found no differences in any kinematic or kinetic parameter between the preferred and non-preferred leg or any parameter from the muscle-tendon interaction analysis other than a reduced longitudinal muscle shortening in the non-preferred leg (p = 0.008). We conclude that, although common at the level of the joints, MTUs, and tendon (series-elastic element), highly active SSCs very rarely occur in the medial gastrocnemius, even in movements that induce high loading. This has important implications for the translation of ex vivo findings on SSC effects, such as residual force enhancement, in this muscle. We further conclude that there is no precise tuning of the architectural gearing ratio in the medial gastrocnemius throughout the whole movement.

Force-sharing within the Triceps Surae: An Achilles Heel in Achilles Tendinopathy.

The primary aim of this study was to determine whether the distribution of force between the three heads of the triceps surae differs between people with Achilles tendinopathy and controls. We also aimed to determine the effect of this force distribution on subtendon strain. Data were collected for 21 participants with Achilles tendinopathy and 21, case-wise paired, asymptomatic controls. Ultrasonography was used to measure muscle volume, fascicle length, pennation angle and subtendon length at rest. Muscle activation was estimated using surface electromyography during maximal and submaximal isometric plantarflexion tasks. The product of normalized activation, physiological cross-sectional area, and the cosine of the pennation angle was considered as an index of individual muscle force. Displacement of the distal myotendinous junction of each muscle was measured during the submaximal contractions. The contribution of the gastrocnemius lateralis to the overall triceps surae physiological cross-sectional area and activation was 8.5% (P = 0.047, d = 0.75) and 24.7% lower (main effect group P = 0.009, d = 0.67) in people with Achilles tendinopathy than in the controls, respectively. Consequently, gastrocnemius lateralis contributed approximately 28% less (main effect group P = 0.025, d = 0.62) of the triceps surae force in people with Achilles tendinopathy. The contribution of gastrocnemius medialis and soleus was not different between groups. Subtendon strain was not different between groups (P = 0.835). These results provide evidence for a difference in force-sharing strategy within the triceps surae in people with Achilles tendinopathy compared with the controls. Whether this altered strategy is a cause or a consequence of Achilles tendinopathy should be explored further.

Effects of Vastus Lateralis Muscle Fascicle Length on Isokinetic Muscle Strength and Dynamic Balance in Youth Soccer Players

PURPOSE The purpose of this study was to determine the effect of vastus lateralis muscle fascicle length on isokinetic muscle strength and dynamic balance in youth soccer players. METHODS Fourteen youth soccer players were divided into long fascicle length group (LFG, n=7) and short fascicle length group (SFG, n=7) by fascicle length of vastus lateralis muscle using ultrasound imaging. And measurements of muscle thickness, fascicle pennation angle, and physiological cross-sectional area were taken at the same location. Additionally, maximal isokinetic strength of knee extensors was assessed at 60°/sec and 120°/sec and a Y-balance test was completed. RESULTS Fascicle length and ratio of fascicle length/lower limb length were significantly greater in LFG than that in SFG (p<.001). Fascicle pennation angle (p<.01) and physiological cross-sectional area (p<.05) were significantly greater in SFG than that in LFG. The isokinetic maximal strength of knee extensors at 120°/sec was significantly greater in SFG than that in LFG (p<.05). The composite score of Y-balance was significantly greater in SFG than that in LFG (p<.05). CONCLUSIONS Our results show differences in architectural characteristics of the vastus lateralis. Further, the maximal isokinetic strength of knee extensors at 120°/sec and the ability of dynamic balance were greater in short vastus lateralis fascicle length of youth soccer players. 색인어: 외측광근, 근속길이, 등속성 ê·¼ë ¥, ë™ì ê· í˜•, ìœ ì†Œë „ ì¶•êµ¬ì„ ìˆ˜ Keywords: Vastus lateralis, Fascicle length, Isokinetic strength, Dynamic balance, Youth soccer players

DiceCT Analysis of the Extreme Gouging Adaptations Within the Masticatory Apparatus of the Aye-Aye (Daubentonia madagascariensis).

Relative to all other primates, the aye-aye (Daubentonia madagascariensis) exists at the extremes of both morphology and behavior. Its specialized anatomy-which includes hypselodont incisors and highly derived manual digits-reflects a dietary niche, unique among primates, which combines tap-foraging with gouging to locate and extract wood-boring larvae. Here, we explore the impact of this extreme dietary ecology upon the masticatory musculature of this taxon with reference to a second, similarly sized but highly generalist lemuriform-the mongoose lemur (Eulemur mongoz). Using non-destructive, high-resolution diffusible iodine-based contrast-enhanced computed tomography techniques, we reconstruct the three-dimensional volumes of eight masticatory muscles, and, for the first time in strepsirrhines, isolate and visualize their constituent muscle fascicles in situ and in three dimensions. Using these data, we report muscle volumes, forces, and fascicle lengths from each muscle portion, as well as their orientation relative to two standardized anatomical planes. Our findings demonstrate the overbuilt nature of the aye-aye's masticatory apparatus, in which each muscle possesses an absolutely and relatively larger muscle volume and PCSA than its counterpart in the mongoose lemur. Likewise, for several adductor muscles, aye-ayes also possess relatively greater fascicle lengths. Finally, we note several unusual features within the lateral pterygoid of the aye-aye-the muscle most responsible for jaw protrusion-that relate to force maximization and reorientation. As this jaw motion is critical to gouging, we interpret these differences to reflect highly specific specializations that facilitate the aye-aye's extreme subsistence strategy. Anat Rec, 2019. © 2019 American Association for Anatomy Anat Rec, 303:282-294, 2020. © 2019 American Association for Anatomy.