Muscle morphological changes and enhanced sprint running performance: A 1-year observational study of well-trained sprinters.

Numerous cross-sectional studies have attempted to identify the muscle morphology required to achieve high sprint velocity. Our longitudinal study addressed an unanswered question of cross-sectional studies: whether hypertrophy of the individual trunk and thigh muscles induced by daily training (e.g., sprint, jump, and resistance training) is linked to an improvement in sprint performance within well-trained sprinters. Twenty-three collegiate male sprinters (100-m best time of 11.36 ± 0.44 s) completed their daily training for 1 year without our intervention. Before and after the observation period, the sprint velocities at 0-100 m, 0-10 m, and 50-60 m intervals were measured using timing gates. The volumes of 14 trunk and thigh muscles were measured using magnetic resonance imaging. Muscle volumes were normalized to the participants' body mass at each time point. Sprint velocities increased at the 0-100 m (p < 0.001), 0-10 m (p = 0.019), and 50-60 m (p = 0.018) intervals after the observation period. The relative volumes of the tensor fasciae latae, sartorius, biceps femoris long head, biceps femoris short head, semitendinosus, and iliacus were increased (all p < 0.050). Among the hypertrophied muscles, only the change in the relative volume of the semitendinosus was positively correlated with the change in sprint velocity at the 50-60 m interval (p = 0.018 and ρ = 0.591). These findings suggest that semitendinosus hypertrophy seems to be associated with sprint performance improvement within well-trained sprinters during the maximal velocity phase.

Can Eccentric-only Resistance Training Decrease Passive Muscle Stiffness while Increasing Size and Strength of Hamstrings?

PURPOSE: Resistance training may be empirically believed to increase passive muscle stiffness. Meanwhile, a recent study showed that the passive stiffness of a specific hamstring muscle acutely decreased after eccentric-only resistance exercise at long muscle lengths with a long contraction duration (LL). To extend this finding, the present study investigated the chronic effects of eccentric-only resistance training with LL at different weekly frequencies on the passive stiffness of the biarticular hamstring muscles. METHODS: Thirty-six healthy young males were assigned into two training groups with two and three weekly sessions (W2 and W3, n = 12, respectively) and a control group (CON, n = 12). The participants in both training groups performed eccentric-only stiff-leg deadlift at 50-100% of exercise range of motion (0% = upright position) with 5 s per repetition for 10 weeks. Before and after the intervention period, the shear moduli of the biarticular hamstring muscles, maximal voluntary isometric torque of knee flexion, and volumes of the individual hamstring muscles were measured. RESULTS: In W3, the shear modulus of the semimembranosus (-11.4%) significantly decreased, whereas those of the other biarticular muscles did not change. There were no significant changes in the shear moduli of the biarticular hamstring muscles in W2 or CON. The isometric torque (20.3 and 26.2%, respectively) and semimembranosus volume (5.7% and 7.4%, respectively) were significantly increased in W2 and W3. CONCLUSIONS: Passive stiffness of a specific muscle could be chronically decreased when eccentric-only resistance training with LL is performed at a relatively high weekly frequency with a high total training volume. Our training modality may be a promising strategy for decreasing passive muscle stiffness while increasing muscular strength and size.

Texture Features of 18F-Fluorodeoxyglucose Positron Emission Tomography for Predicting Programmed Death-Ligand-1 Levels in Non-Small Cell Lung Cancer.

Background: Identifying programmed death-ligand-1 (PD-L1) expression is crucial for optimizing treatment strategies involving immune checkpoint inhibitors. However, the role of intratumoral metabolic heterogeneity specifically derived from 18F-fluorodeoxyglucose (FDG) positron emission tomography (PET) images in predicting PD-L1 expression in patients with newly diagnosed non-small cell lung cancer (NSCLC) remains unexplored. Here, we investigated the association between FDG PET texture features and PD-L1 expression by retrospectively analyzing the data of patients newly diagnosed with NSCLC who underwent FDG PET/CT scans and PD-L1 immunohistochemical staining before treatment. Methods: Patients were categorized based on their tumor proportion scores (TPSs) into negative-, low-, and high-PD-L1 expression groups. We computed the maximum standardized uptake value and 31 texture features for the primary tumor from PET images and compared differences in parameters among the groups. Results: Of the 83 patients, 12, 45, and 26 were assigned to the negative-, low-, and high-PD-L1 expression groups, respectively. Six specific texture features (low gray-level run emphasis, short-run low gray-level emphasis, long-run high gray-level emphasis, low gray-level zone emphasis, high gray-level zone emphasis, and short-zone low gray-level emphasis) helped distinguish among all possible combinations. Conclusions: Our findings revealed that FDG PET texture features are potential imaging biomarkers for predicting PD-L1 expression in patients newly diagnosed with NSCLC.