Hamstring Architectural and Functional Adaptations Following Long vs. Short Muscle Length Eccentric Training

Joint angle-torque characteristics of the knee extensors following eccentric exercise-induced muscle damage in young, active women

BackgroundThe single leg bridge test (SLBT) has been introduced in the sports context as a way of estimating hamstring muscle capacity for prevention and rehabilitation of hamstring strain injuries.PurposeThe primary aim was to examine the association between SLBT scores with concentric and eccentric knee flexor peak torques. Secondarily, this study aimed examine the association of between-limb asymmetries provided by SLBT and isokinetic tests.Study designCross-sectional study.MethodsOne hundred male soccer players (20±3 years) performed the SLBT and the knee flexion-extension isokinetic dynamometry evaluation (60°/s) billaterally during a single visit. SLBT score (i.e., number of repetitions until failure) and concentric and eccentric knee flexor peak torques (normalized per body mass) were considered for analysis. For both SLBT and isokinetic dynamometry, between-limb asymmetry was calculated as the percentage difference between the left limb and the right limb. Associations were assessed through Pearson’s correlation coefficient.ResultsThe mean SLBT score was 33.6±9.6 repetitions, concentric peak torque was 2.00±0.22 Nm/kg, and eccentric peak torque was 2.79±0.44 Nm/kg. Between-limb asymmetry was 0.4±9.6%, 1.08±8.5%, and 1.64±14.61% in SLBT, concentric, and eccentric tests, respectively. There was a poor association of SLBT score with concentric (p<0.001, r=0.275) and eccentric (p=0.002, r=0.215) peak torques. The SLBT between-limb asymmetry was poorly associated with asymmetry found in concentric peak torque asymmetry (p=0.033, r=0.213) and was not associated with eccentric peak torque asymmetry (p=0.539, r=0.062).ConclusionThe SLBT should not be used as a clinical tool to assess the maximum strength of hamstring muscles.Level of EvidenceLevel 3

Eccentric exercise training is believed to induce an increase in muscle fascicle length. However, the mechanisms underlying this adaptation are not fully understood. This study aimed to determine if an increase in gastrocnemius medialis fascicle length following an 8-wk eccentric training is linked to changes in muscle tissue and joint mechanical properties. Thirty-three physically active young adults were assigned to one of the two training protocols targeting the plantar flexors: eccentric exercise at 1) long-muscle length or 2) short-muscle length. Fascicle length and muscle shear modulus of the gastrocnemius medialis were assessed using ultrasound imaging during passive ankle rotations, alongside measurements of passive ankle torque. A total of 27 participants successfully completed the training program and data processing stage (long-muscle length, n = 15; short-muscle length, n = 12). Maximal voluntary isometric torque increased significantly following the training programs (9.5%), with no differences between training groups. An increase in fascicle length (mean 8.5%) was observed in the long-muscle length group, from 39.5 ± 0.7° to 36.8 ± 0.8° in plantar flexion, but not in the short-muscle length group. Notably, this macrostructural adaptation was detected only at muscle lengths shorter than the slack length (i.e., absence of any muscle passive tension). The eccentric training did not alter the muscle shear modulus or slack length. Collectively, these findings suggest that fascicle length adaptations in response to eccentric training were unrelated to changes in passive muscle-tendon mechanical properties. Consequently, the increase in fascicle length may be attributed to an increase in sarcomere length and/or an addition of sarcomeres in series.NEW & NOTEWORTHY We demonstrate that an 8-wk eccentric training program significantly increases gastrocnemius medialis fascicle length in humans, independent of any adaptions in passive muscle-tendon mechanical properties. Fascicle length adaptions were specific to the group that trained at long-muscle lengths, highlighting the importance of the muscle-tendon length range during eccentric exercise programs. This factor may be crucial for fine-tuning structural adaptations at the fascicle level, likely through the addition of sarcomeres in series.

A simple geometrical model accounting for 3D muscle architectural changes across muscle lengths

Hamstring muscle architecture may be associated with sprint performance and the risk of sustaining a muscle injury, both of which increase during puberty. In this study, we investigated the m. biceps femoris long head (BFlh) cross-sectional area (ACSA), fascicle length (FL) and pennation angle (PA), and sprint performance as well as their relationship in under 13 to 15 youth soccer players. We measured 85 players in under-13 (n = 29, age = 12.5 [0.1]y, height = 155.3 [6.2]cm, weight = 43.9 [7.6]kg), under-14 (n = 25, age = 13.5 [0.3]y, height = 160.6 [7.7]cm, weight = 47.0 [6.8]kg), and under-15 (n = 31, age = 14.4 [0.3]y, height = 170.0 [7.7]cm, weight = 58.1 [8.8]kg) teams. We used ultrasound to measure BFlh ACSA, FL and PA, and sprint tests to assess 10- and 30-m sprint time, maximal velocity (vmax), and maximal acceleration (αmax). We calculated Pearson r to assess the relationship between sprint ability and architectural parameters. All muscle architectural parameters increased from the under-13 to the under-15 age group (BFlh ACSA = 37%, BFlh FL = 11%, BFlh PA = 8%). All sprint performance parameters improved from the under-13 to under-15 age categories (30-m time = 7%, 10-m time = 4%, vmax = 9%, αmax = 7%). The BFlh ACSA was correlated with 30-m sprint time (r = -.61 (95% compatibility interval [CI] [-.73, -.45]) and vmax (r = .61, 95% CI [.45, .72]). A combination of BFlh ACSA and age best predicted 30-m time (R² = .47 [.33, .62]) and 10-m time (R² = .23 [.08, .38]). Muscle architectural as well as sprint performance parameters increase from the under-13 to under-15 age groups. Even though we found correlations for all assessed architectural parameters, BFlh ACSA was best related to the assessed sprint parameters.

Effect Size Guidelines for Individual and Group Differences in Physiotherapy.

The aging process can lead to changes in muscle architecture, such as reduction of muscle thickness (MT), pennation angle (PA) and fascicle length (FL), which may contribute to dinapenia. Thus, the aim of the study was to correlate the medial gastrocnemius (MG) muscle architecture and plantiflexors peak of torque (PT) of community older women. Cross-sectional study approved by the Research Ethics Committee of Federal University of Parana (36003814.2.0000.0102). The study included 48 older women (70.4 ± 5.1 years-old; BMI: 27.8 ± 4 Kg/m). MG architecture was evaluated at 30% of the distance between medial tibia condyle and medial malleolus, using a B-mode ultrasonography imaging device (Logiq Book-XP, General Eletric®) with a linear-array probe (50mm, 4cm of depth, 11 MHz). The ImageJ software was used to analyze MT (mean distance between deep and superficial aponeuroses), PA (angle of insertion of muscle fiber fascicles into the deep aponeurosis) and FL (fascicle length between the superior and deep aponeuroses). The concentric plantiflexors PT was evaluated by an isokinetic dynamometer (System4, Biodex®) with 30° of range of motion, three repetitions each set performed at 60°/s and 180°/s. To verify the association between variables the Pearson correlation test was used (p<0.05). The mean±SD were: MT=1.6 ± 0.2cm; PA=26.7 ± 3.4°; FL=3.8 ± 0.5cm; PT60°/s=39.8 ± 11.4Nm; PT180°/s 31 ± 9.2Nm. It was observed correlation between MT and PT60°/s (r=0.412, p=0.004); MT and PT180°/s (r=0.387, p=0.007); FL and PT60°/s (r=0.334, p=0.020). It can be concluded that the greater MG thickness and FL, the greater is the plantiflexors power and strength of community older women.

Muscle performance is closely related to the architecture and dimensions of the muscle-tendon unit and the effect of maturation on these architectural characteristics in humans is currently unknown. This study determined whether there are differences in musculo-tendinous architecture between adults and children of both sexes. Fascicle length and pennation angle were measured from ultrasound images at three sites along the length of the vastus intermedius, vastus lateralis, vastis medialis and rectus femoris muscles. Muscle volume and muscle-tendon length were measured from magnetic resonance images. Muscle physiological cross-sectional area (PCSA) was calculated as the ratio of muscle volume to optimum fascicle length. Fascicle length was greater in the adult groups than in children (P < 0.05) but pennation angle did not differ between groups (P > 0.05). The ratios between fascicle and muscle length and between fascicle and tendon length were not different (P > 0.05) between adults and children for any quadriceps muscle. Quadriceps volume and PCSA of each muscle were greater in adults than children (P < 0.01) but the relative proportion of each head to the total quadriceps volume was similar in all groups. However, the difference in PCSA between adults and children (men approximately 104% greater than boys, women approximately 57% greater than girls) was greater (P < 0.05) than the difference in fascicle length (men approximately 37% greater than boys, women approximately 10% greater than girls). It is concluded that the fascicle, muscle and tendon lengthen proportionally during maturation, thus the muscle-tendon stiffness and excursion range are likely to be similar in children and adults but the relatively greater increase in PCSA than fascicle length indicates that adult muscles are better designed for force production than children's muscles.

Poststroke plantar flexor muscle weakness has been attributed to muscle atrophy and impaired activation, which cannot collectively explain the limitations in force-generating capability of the entire muscle group. It is of interest whether changes in poststroke plantar flexor muscle fascicle length and pennation angle influence the individual force-generating capability and whether plantar flexor weakness is due to uniform changes in individual muscle force contributions. Fascicle lengths and pennation angles for the soleus, medial, and lateral gastrocnemius were measured using ultrasound and compared between ten hemiparetic poststroke subjects and ten healthy controls. Physiological cross-sectional areas and force contributions to poststroke plantar flexor torque were estimated for each muscle. No statistical differences were observed for any muscle fascicle lengths or for the lateral gastrocnemius and soleus pennation angles between paretic, nonparetic, and healthy limbs. There was a significant decrease (P < 0.05) in the paretic medial gastrocnemius pennation angle compared to both nonparetic and healthy limbs. Physiological cross-sectional areas and force contributions were smaller on the paretic side. Additionally, bilateral muscle contributions to plantar flexor torque remained the same. While the architecture of each individual plantar flexor muscle is affected differently after stroke, the relative contribution of each muscle remains the same.

BackgroundMidfoot osteoarthritis (OA) is a common condition, however its aetiology is not well understood. Understanding how plantar pressures differ between people with and without midfoot OA may provide insight into the aetiology and how best to manage this condition. Research questionTo compare plantar pressures between people with and without symptomatic radiographic midfoot OA. MethodsThis was a cross-sectional study of adults aged ≥ 50 years registered with four UK general practices who reported foot pain in the past year. Symptomatic radiographic midfoot OA was defined as midfoot pain in the last four weeks, combined with radiographic OA in one or more midfoot joints. Cases were matched 1:1 for sex and age ( ± 5 years) to controls. Peak plantar pressure and maximum force in 10 regions of the foot were determined using a pressure platform (RSscan International, Olen, Belgium) and compared between the groups using independent samples t-tests and effect sizes (Cohen’s d). ResultsWe included 61 midfoot OA cases (mean age 67.0, SD 8.1, 31 males, 30 females) and matched these to 61 controls (mean age 66.0, SD 7.9). Midfoot OA cases displayed greater force (d=0.79, medium effect size, p = <0.001) and pressure at the midfoot (d=0.70, medium effect size, p = <0.001), greater force at the fourth metatarsophalangeal (MTP) joint (d=0.28, small effect size, p = 0.13), and fifth MTP joint (d=0.37, small effect size, p = 0.10) and greater pressure at the fifth MTP joint (d=0.34, small effect size, p = 0.13). They also displayed lower force (d=0.40, small effect size, p = 0.02) and pressure at the hallux (d=0.50, medium effect size, p = <0.001) and lower force (d=0.54, medium effect size, p = <0.001) and pressure at the lesser toes (d=0.48, small effect size, p = <0.001) compared with controls. SignificanceMidfoot OA appears to be associated with lowering of the medial longitudinal arch, greater lateral push off and less propulsion at toe off. Longitudinal studies are needed to establish causal relationships.

The survey research reported in this paper aimed to show how foreign language teachers’ (N = 69) self-efficacy beliefs and concerns related to implementing inclusive instructional practices with learners with dyslexia, as well as their attitudes to inclusion in foreign language education, change as a result of the teachers’ participation in an intensive face-to-face course on dyslexia and foreign language teaching. The pre-post comparisons identified a statistically significant improvement in self-efficacy beliefs and attitudes, with large and medium effect sizes, respectively, as well as a decrease in concerns, with a small effect size. Moreover, the perceived level of knowledge of dyslexia reported by course participants after the course increased significantly compared to pre-course knowledge, with a large effect size. The perceptions of knowledge were crucially related to pre-course self-efficacy beliefs and concerns, as well as to post-course self-efficacy beliefs. The impact of several background variables on self-efficacy beliefs, concerns and attitudes was investigated. We found no significant effects of general teaching experience, experience in teaching learners with dyslexia, teaching context (country), full-time employment and level of education on self-efficacy beliefs and attitudes both before and after the course. The initial effect of previous training on self-efficacy beliefs disappeared in the post-course questionnaire. No significant effects of previous training were observed for pre-course and post-course concerns and attitudes. The initial effect of level of education and experience in teaching a foreign language to learners with dyslexia on concerns disappeared in the post-course questionnaire. Teaching context (country) and full-time employment differentiated participants with regard to how concerned they were about implementing inclusive teaching before the course, and these differences persisted after the course. Age differentiated participants in the attitudes to inclusion they held before the course, but this difference disappeared after the course. Finally, teacher trainers differed significantly from other course participants regarding pre-course self-efficacy and post-course concerns, with a small to medium effect size.

Skeletal muscles change length and develop force both passively and actively. Gearing allows muscle fiber length changes to be uncoupled from those of the whole muscle-tendon unit. During active contractions this process allows muscles to operate at mechanically favorable conditions for power or economical force production. Here we ask whether gearing is constant in passive muscle; determining the relationship between fascicle and muscle-tendon unit length change in the bi-articular medial gastrocnemius and investigating the influence of whether motion occurs at the knee or ankle joint. Specifically, the same muscle-tendon unit length changes were elicited by rotating either the ankle or knee joint whilst simultaneously measuring fascicle lengths in proximal and distal muscle regions using B-mode ultrasound. In both the proximal and distal muscle region, passive gearing values differed depending on whether ankle or knee motion occurred. Fascicle length changes were greater with ankle motion, likely reflecting anatomical differences in proximal and distal passive tendinous tissues, as well as shape changes of the adjacent mono-articular soleus. This suggests that there is joint-dependent dissociation between the mechanical behavior of muscle fibers and the muscle-tendon unit during passive joint motions that may be important to consider when developing accurate models of bi-articular muscles.

Muscle ultrasound (MUS) has so far not been implemented for sarcopenia assessment in clinical geriatric practice due to allegedly low reproducibility of results in the absence of standardization of procedures. However, rigorous and standardized application of this technique yields highly reproducible results. Its application, especially if integrated with clinical evaluation and comprehensive geriatric assessment, proofs very useful for rapidly obtaining information on muscle mass and architecture. Here, we present a standardized protocol for performing right vastus lateralis (RVL) MUS and measuring parameters of muscle size and architecture. RVL muscle thickness (MT), fascicle length (FL), pennation angle (PA), echo-intensity (EI) and cross-sectional area (CSA) can be assessed with this protocol. A portable instrument equipped with a 5-cm long 3-11mHz linear probe should be used with both B-mode real-time and extended-field-of-view (EFOV) techniques. Longitudinal B-mode and transverse EFOV images should be acquired during each exam, and analyzed with NIH-ImageJ software. This operative protocol represents a good compromise between the feasibility of MUS in clinical settings and the need of obtaining precise measurements of muscle parameters. Future studies should verify the reproducibility of the proposed technique, and its correlation with appendicular lean mass and parameters of muscle function.

Reliability of a new semi-automated algorithm to analyze vastus lateralis muscle architecture using extended field-of-view ultrasound.

It remains unclear whether different training modalities, such as strength training (ST) and cross-training (CT), induce distinct musculoskeletal adaptations. In this cross-sectional study, thirty-seven males with at least 2 years of experience in the respective modality participated (ST = 20; CT = 17). After anthropometric assessment, vastus lateralis (VL) muscle architecture and stiffness were evaluated, determining fascicle length (FL), muscle thickness (MT), pennation angle (PA), and shear-wave velocity. Knee extensor peak torque was measured in an isokinetic dynamometer at 60°/s, 180°/s, and 300°/s and normalized to the maximum voluntary isometric contraction. One-repetition maximum (1RM) in the barbell back squat was estimated within three trials with knee flexion standardized at 120° (0°= full extension) and normalized to body mass. Specific tension was calculated based on MT and peak torque. Statistical significance was set at α = 0.05, and Cohen's D effect size was calculated. The intraclass correlation coefficient (ICC) was used to assess muscle architecture reliability. An independent sample t-test revealed a higher training experience (ES = 1.02) and weekly training volume (ES = 0.88; p < 0.05) in ST, whereas CT group showed higher age (ES = 1.09) and PA (ES = 0.66). No differences between groups were found for FL, MT, stiffness, and specific tension (p > 0.05). The peak torque in all tested velocities and 1RM was higher for CT compared to ST (ES = 1.03-1.38; p < 0.05). Interrater reliability ranged from good to excellent (ICC = 0.841-0.992; p < 0.05). Although the cross-sectional design adopted, the current study provides important insights into musculoskeletal differences between training modalities, in accordance with the principle of specificity.