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Purpose: To compare muscle architecture variables between sport and sex in competitive athletes, and to compare muscle architecture with performance variables in strong versus weak athletes, and good versus poor jumpers. Methods: The vastus lateralis (VL) and lateral gastrocnemius (LG) muscles of 139 collegiate athletes were collected using ultrasonography to determine muscle thickness (MT), pennation angle (PA), fascicle length (FL), and relative fascicle length (FLrel). Absolute and relative peak power, absolute and relative isometric peak force, and jump height were measured in a subset of baseball and soccer athletes. A 5x2 factorial analysis of variance (ANOVA) was used to investigate differences in group means between sex and sport for muscle architecture variables in the larger cohort. A 2x2 factorial ANOVA was used in the in the smaller cohort to investigate differences between strong and weak athletes, and good and poor jumpers. Results: Significant main effects were observed for sex in VL muscle thickness (MT), VL pennation angle (PA), LG MT, and LG fascicle length (FL). Significant main effects were observed for sport in VL MT, VL FL, VL relative fascicle length (FLrel) and LG MT. Significant interaction effects were observed for LG PA and LG FLrel. Muscle architecture profiles were significantly different between strong and weak, and good and poor jumpers in baseball, but not soccer athletes. Soccer athletes had greater PA but smaller FL than baseball athletes. Conclusions: Muscle architecture may play a role in sport selection, undergoes directed adaptation to sport specific training demands, and may differentiate between high and low performers in more anaerobic athletes. Males had greater muscle thickness than females. Patterns of PA and FL values between sport and sex differed between VL and LG. More aerobic athletes such as soccer athletes may have greater VL PA and smaller VL FL than more anaerobic athletes such as baseball athletes.

This study investigates the in-vivo architecture of muscles in the lower leg using 2D ultrasound (US) and 3D diffusion tensor imaging (DTI) techniques. The muscle architecture of the gastrocnemius, posterior soleus and tibialis anterior were compared using US and DTI imaging. DTI and US differed on average by 17% in fascicle length (FL), 20% in muscle thickness (tm), and 36% in pennation angles (PA).The study furthermore examined the muscle morphology after stroke by comparing the muscles of the affected side to the less-affected side of five hemiplegic post-stroke patients. The morphology of eight muscle compartments in both legs of the patients was measured using only DTI. An, on average, 14% smaller muscle volume in the effected side was found, as well as a difference of 15% in FL, 11% PA, and 17% in physiological cross-sectional area (PCSA). However, changes in FL, PA and PCSA were not only observed between sides but also differed among muscle compartments. The parameter values were in general in the range of human subjects but no conclusive differences between sides could be found based on the acquired data. In conclusion, DTI and US both yielded results of muscle architecture parameters within a physiologically range but can differ substantially between methods and cannot be compared directly.

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Muscle function is determined by structure and morphology at the architectural level. In response to resistance training, older adults have demonstrated that the neuromuscular system has a substantial adaptability, which may compensate for muscle size and quality and lead to improved functional capacities and higher quality of life. PURPOSE: The purpose of this study was to examine the effect of six weeks of progressive resistance exercise on muscle morphology and architecture in healthy older adults. METHODS: Twenty- five healthy men and women were randomly assigned to either six weeks of progressive resistance training (RT) (n=13; age = 71.08 ± 6.75, BMI = 28.5 ± 5.22) or to serve as a control (CON) (n = 12; age = 70.17 ± 5.58, BMI = 27.52 ± 5.6). Fat mass (FM), lean mass (LM), and lean thigh mass (LTM) were evaluated using dual x-ray absorptiometry. Lower body strength was estimated by predicting maximal knee extensor strength (1RM). Muscle quality (MQ) was evaluated as strength per unit mass (kg/kg). Cross-sectional area (CSA), muscle thickness (MT), fascicle length (Lf), pennation angle (cosΘ), and echo intensity (EI) of the rectus femoris (RF) and vastus lateralis (VL) were collected using B-mode ultrasound and extended field of view (FOV) ultrasound. EI was quantified using grayscale analysis software. Strength per unit of echo intensity (REI) was determined by dividing 1RM by EI of the thigh. Physiological cross-sectional area (PCSA) was calculated as the ratio of (CSA x cosΘ) / (EI x Lf). A 2x2 (group [exercise vs. control] x time [pre vs. post]) repeated measures ANOVA was used to identify group differences and group x time interactions and stepwise regression was performed to assess variables related to strength. RESULTS: 1RM increased by 31.9% (p ≤ 0.01) in the RT group and was significantly correlated to PCSA of the thigh (r = .579; p = .003) at baseline. MQ increased 31.4% (p ≤ 0.01) in the RT group consistent iv with an REI increase of 33.3% (p ≤ 0.01). There were no significant changes in LTM in either group. VL CSA increased 7.4%, (p ≤ 0.05) and demonstrated a significant interaction (p ≤ 0.05) in the RT group. There were no significant changes in the CON group for 1RM, MQ, REI or VL CSA. PCSA demonstrated a significant (p ≤ 0.05) group x time interaction but did not significantly change in either group. EI did not significantly change in the RT or CON groups. CONCLUSION: Calculated PCSA of the thigh assessed by ultrasound was related to the force producing capacity of muscle and demonstrated a significant interaction following resistance training. Short term resistance exercise training was effective in increasing 1RM, muscle quality as relative strength, muscle quality as relative echo intensity, and muscle morphology, but not EI. In addition, ultrasonography appears to be a safe, feasible, informative and sensitive clinical technique to aid in our understanding of muscle strength, function, and quality.

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<p> A slow concentric contraction of the tibialis anterior muscle was imaged using Brightness-Mode Ultrasonography (BMU) from different probe orientations to determine the effect of probe orientation on the measurement of muscle architecture parameters (MAP). Nine contractions were performed by each of nine subjects. Each contraction was visualized with a different probe orientation on the anterior surface of the muscle. Data was taken from the same four joint angles from all contractions from all subjects and then compared for values of torque, tibialis anterior EMG and measures of MAP which include; fascicle length (FL), pennation angle (PA) and muscle thickness (MT).</p> <p> The results of an analysis of variance found a significant difference between joint angles for measures of FL and PA but not MT. A significant difference was found between probe rotations for the measures of FL and MT but not PA.</p> <p> A reliability study was performed for measures of MAP and found the coefficient of variation for FL and PA to be less than 8% both with and without the use of an image filter. The coefficient of variation for MT was found to be less than 2% which shows this measure to be highly reliable.</p> <p> Equations and Figures were developed, corresponding to the observations and assumptions made by MAP researchers using BMU, to predict the effect of probe orientation on the measures of MAP.</p> <p> The results of this study indicate that ultrasound probe orientation affects measures of MAP but the effect either cannot be predicted from a simple geometric model or the error in the measurement technique does not allow this type of comparison. Specific guidelines are outlined in this paper to determine the proper probe placement and orientation to measure MAP using BMU for the tibialis anterior muscle.</p> / Thesis / Master of Science (MSc)

Rotator cuff pathologies involving supraspinatus are a common cause of musculoskeletal morbidity and can lead to significant disability affecting the overall quality of life. Architectural parameters of the muscle directly influence its functional properties. Therefore, understanding of fiber bundle changes with surgery and different exercises can assist clinicians in planning better surgical and shoulder rehabilitative protocols. The first objective of this thesis was to systematically review human cadaveric studies of the normal supraspinatus architecture and highlight the key aspects that should be considered while performing studies of skeletal muscle architecture. The second objective was to understand the impact of surgical repair on the structural and functional recovery of the supraspinatus. The final objective was to provide a scientific rationale behind choosing an exercise to strengthen supraspinatus by investigating its muscle architecture. Study 1 systematically reviewed human cadaveric studies of the normal supraspinatus architecture. Results showed that the overall quality of majority of included is poor and there was a large range in the reported architectural values of the entire muscle. In conclusion, there were only a few studies providing the level of detail and quality suitable for advancing our understanding of shoulder biomechanics. Study 2 quantified and compared the fiber bundle architecture of the pathologic supraspinatus pre- and post-operatively at multiple time points. Results showed significant lengthening of fiber bundles after one month of surgery which then decreased significantly by 6 months of surgery. In contrast, an initial decrease followed by an increase in pennation angle overtime was found. The results suggest that the stretching applied to the tendon and muscle during repair could affect the length-tension relationship of the muscle, which in turn can compromise its function and may lead to inferior surgical outcomes. Study 3 compared the efficacy of three commonly prescribed supraspinatus strengthening exercises in the rehabilitation setting based on the architectural changes following resistance training. Results showed there was no change in FBL and increased strength after resistance training with prone horizontal abduction exercise. Findings suggest that prone horizontal abduction may be a more suitable exercise to strengthen supraspinatus.

This thesis examined the change in skeletal muscle architecture with contractile force production, the relationship of architecture with muscle strength parameters and if muscle tendinous tissue stiffness determines in vivo explosive strength (i.e. rate of torque development, RTD). Muscle and tendinous tissue adaptations to contrasting strength training regimes, and the potential capacity of these tissues to adapt following chronic strength training were also explored. Quadriceps femoris fascicle length (FL) decreased, while the pennation angle (PA) increased in a curvi-linearly manner from rest to maximal voluntary contraction (MVC) torque. Consequently, effective physiological cross-sectional area (effPCSA) during MVC was 27% greater than at rest, although effPCSA measured at rest and during MVC had similar correlations to maximal strength. In the earliest phase of contraction, FL, but not PA, was negatively related (R2=0.187) to voluntary RTD. Neither FL nor PA was related to maximal isometric or dynamic strength. Muscle-tendon unit (MTU) and patellar tendon (PT) stiffness were unrelated to voluntary and evoked RTD. Relative PT stiffness was also unrelated to relative RTD, although relative MTU stiffness was related to voluntary RTD (25-55%MVT, R2≤0.188) and evoked RTD (5-50%MVT, R2≤0.194). MTU stiffness increased after sustained-contraction (SCT, +21%), though not explosive-contraction strength training (ECT). PT stiffness increased similarly after ECT (+20%) and SCT (+16%), yet neither induced tendon hypertrophy. SCT produced modest muscle (+8%) and aponeurosis (+7%) hypertrophy. Chronic strength trained (CST: >3 years) males had substantially greater muscle and aponeurosis size, but similar tendon size as untrained controls (UNT) and short-term (12 weeks) strength trained (STT) individuals. Between these groups, at the highest common force, MTU stiffness was indifferent, while PT stiffness was similarly greater in STT and CST than UNT. These results suggest FL and PA have little influence on muscle strength and tendon stiffness has no influence on RTD. Maximum strength negated any qualitative influence of MTU stiffness on in vivo RTD. Component MTU tissues (muscle-aponeurosis vs. external tendon) adapt differentially depending on the strength training regime. Specifically, free tendon appeared to adapt to high magnitude loading, while loading duration is also an important stimulus for the muscle-aponeurosis. However, chronic strength training was not concordant with greater higher force MTU stiffness, and does not further increase higher force PT stiffness beyond the adaptations that occur after 12 weeks of strength training. Finally, no evidence was found for tendon hypertrophy in response to strength training.