Purpose: To assess the repeatability of, and measurement agreement between, four sonographic techniques used to quantify biceps femoris long head (BFlh) architecture: (i) static-image with linear extrapolation; extended field-of-view (EFOV) with linear ultrasound probe path (linear-EFOV), using either (ii) straight or (iii) segmented analyses; and (iv) EFOV with nonlinear probe path and segmented analysis (nonlinear-EFOV) to follow the complex fascicle trajectories. Methods: Twenty individuals (24.4 ± 5.7 yr; 175 ± 0.8 cm; 73 ± 9.0 kg) without history of hamstrings strain injury were tested in two sessions separated by 1 h. An ultrasound scanner coupled with 6-cm linear probe was used to assess BFlh architecture in B-mode. Results: The ultrasound probe was positioned at 52.0% ± 5.0% of femur length and 57.0% ± 6.0% of BFlh length. We found an acceptable repeatability when assessing BFlh fascicle length (ICC_3,k = 0.86–0.95; SEM = 1.9–3.2 mm) and angle (ICC_3,k = 0.86–0.97; SEM = 0.8°–1.1^o) using all sonographic techniques. However, the nonlinear-EFOV technique showed the highest repeatability (fascicle length ICC_3,k = 0.95; fascicle angle, ICC_3,k = 0.97). The static-image technique, which estimated 35.4% ± 7.0% of the fascicle length, overestimated fascicle length (8%–11%) and underestimated fascicle angle (8%–9%) compared with EFOV techniques. Also, the rank order of individuals varied by approximately 15% between static-image and nonlinear-EFOV (segmented) when assessing the fascicle length. Conclusions: Although all techniques showed good repeatability, absolute errors were observed using static-image (7.9 ± 6.1 mm for fascicle length) and linear-EFOV (between 3.7 ± 3.0 and 4.2 ± 3.7 mm), probably because the complex fascicle trajectories were not followed. The rank order of individuals for fascicle length and angle were also different between static-image and nonlinear-EFOV, so different muscle function and injury risk estimates could likely be made when using this technique.

High-speed running (HSR) is one of the performance metrics of interest, as the volume of HSR during matches has been increasing over the last decade, which suggests that weekly training loads should be adjusted to align with this trend, enabling players to cope with match demands. However, the use of HSR thresholds lacks a solid rationale for their application and fails to account for individual player capacities, likely not reflecting their actual HSR efforts. As such, this theoretical-discussion provides important implications for training prescription, aiming to optimize performance and minimize fatigue. It emphasizes the significant differences in the conceptualization of HSR and highlights the advantages of adopting a normalized approach that reflects the physiological, mechanical and neuromuscular aspects related to HSR, as well as the intermittent profile of football matches. Practical HSR threshold definitions tailored to the capacities of each athlete are proposed, enabling a more evidence-based approach for the interpretation of training loads and game/player profiling. More specifically, within our proposal, HSR can be subdivided into two types: (1) HSR-1, characterized by an entry threshold based on a normalized critical speed, and (2) HSR-2, defined by an entry threshold corresponding to 75% of the athlete's maximum speed.

The aim of the present study is to compare the effects of a (i) repeated sprint protocol on the sprint performance, hamstrings shear modulus pattern, and neuromuscular parameters between players with and without previous hamstring strain injury (HSI); and (ii) between limbs with HSI and their healthy contralateral limbs on the hamstrings shear modulus pattern and neuromuscular parameters. One-hundred-and-five professional and semiprofessional football field players were invited to participate in this study during the pre-season 2021/2022 (June–July), resulting in a sample size of 210 limbs with 46 sustaining HSI in the previous 2 years. No differences were seen between previously injured and healthy control players regarding their sprint performance, hamstrings shear modulus pattern, and neuromuscular parameters, except for the early rate of torque development (0–50 ms) with previously injured limbs in the biceps femoris long head (BFlh) displaying higher rates than their contralateral muscle (injured: 496.93 ± 234.22 Nm/s; contralateral 422.72 ± 208.29 Nm/s; p = 0.005; η²_p = 0.469). Overall, the present study provides evidence for no differences regarding sprint performance, hamstrings load sharing pattern, and major neuromuscular parameters between players with previous HSI in the last 2 years and healthy control players. Therefore, the results can possibly suggest that the duration between injury and screening could recover the differences between injured-control and injured-contralateral groups.

The purpose of the present study was to examine the acute effects of a maximum repeated sprint protocol on (1) hamstring shear modulus and (2) knee flexor neuromuscular parameters such as peak torque (PT) and rate of torque development (RTD). Muscle shear modulus was assessed in 18 healthy males using shear wave elastography at rest and during 30° isometric knee flexion at 20% of maximal voluntary isometric contraction, before and after a 10 × 30 m repeated sprint protocol. There was a 9% decrease in average speed between the fastest and slowest sprint (p < 0.001; d = 2.27). A pre-post decrease was observed in PT (p = 0.004; η²_p = 0.399) and in the 0–50 ms (p = 0.042; η²_p = 0.222), and 50–100 ms (p = 0.028; η²_p = 0.254) RTD periods. For the active shear modulus, the only significant change after the sprint task was in the biceps femoris long head (BFlh) with an increase of 10% (Pre: 26.29 ± 8.89 kPa; Post: 28.93 ± 8.31 kPa; p = 0.015; d = 0.31). The present study provides evidence that repeated sprinting leads to significant decreases in average speed, PT, early RTD (0–50 ms; 50–100 ms), and to an increase in BFlh active shear modulus without changing the shear modulus of the other hamstrings muscles.

This study examined the effects of ultrasound transducer pressure and examiner experience on the biceps femoris long head and semitendinosus muscle active shear modulus in healthy individuals (n = 28). Active shear modulus was assessed using shear wave elastography at 20% of knee flexor maximal voluntary isometric contraction. Examiners with different experience levels measured the muscles' shear modulus with three pressure levels: mild, moderate, and hard. A main effect of transducer pressure was found for both biceps femoris long head (p < 0.001; η²_p = 0.314) and semitendinosus muscles (p < 0.001; η²_p = 0.280), whereas differences were found between mild-moderate (biceps femoris long head: p = 0.013, d = 0.23; semitendinosus: p = 0.024, d = 0.25), and mild-hard pressures (biceps femoris long head: p = 0.001, d = 0.47; semitendinosus: p = 0.002, d = 0.47). Examiners performed similar shear modulus measurements in the biceps femoris long head (p = 0.299; η²_p = 0.041) and semitendinosus (p = 0.177; η²_p = 0.066), although the experienced examiner showed a higher measurement repeatability (biceps femoris long head: ICC = 0.86-0.95, semitendinosus: ICC = 0.89-0.96; vs. biceps femoris long head: ICC = 0.78-0.87, semitendinosus: ICC = 0.66-0.87). Transducer pressure influences the active shear modulus measurement between mild and moderate or hard pressures. Additionally, examiner experience seems to have no influence on muscle active shear modulus measurement when assessed at the same site (using casts). Future studies assessing active muscle shear modulus should use mild transducer pressure and having experienced examiners in order to improve measurement reliability.

ISHS V International Symposium on New Floricultural Crops EFFECTS OF MATURATION AND SCARIFICATION ON SEED GERMINATION OF SYAGRUS SCHIZOPHYLLA (MART.) GLASS. (ARECACEAE)