Gastrocnemius muscle architecture in elite basketballers and cyclists: a cross-sectional cohort study - Datasets

A trained sonographer obtained three B-mode ultrasound images from gastrocnemius medialis (GM) and gastrocnemius lateralis (GL) muscles in 44 athletes (25 basketballers and 19 cyclists; 24±5 years of age). The images were digitized and average fascicle length (FL), pennation angle (θ) and muscle thickness were calculated from three images per muscle. The ratio of FL to tibial length (FL/TL) and muscle thickness to tibial length (MT/TL) were also calculated to account for the potential scaling effect of stature.

Body mass was measured to the nearest 0.1 kg using a calibrated analogue floor-scale (Model 762; Seca, Germany), and stretch stature was measured to the nearest 0.1 cm using a portable stadiometer (Model 213; Seca; Germany) according to the procedures described by the International Society for the Advancement of Kinanthropometry. Tibial length was estimated using validated regression equations based on stature. Skeletal muscle architecture of the GL and GM muscles at rest, was measured using 2-dimensional B-mode ultrasound (LOGIQ V2; GE Healthcare, Australia), with a 38 mm wide linear probe and a standardized frequency of 12-13 MHz.

Each participant lay prone on an examination table and an incline foam wedge was used to support their flexed knee up to 30° to ensure the gastrocnemius muscle was relaxed at the knee joint. A custom splint secured the ankle joint close to 90° where the sole of the foot is perpendicular to the tibia. This position was confirmed with a manual goniometer and a position within the range of 85° to 95° was accepted. The sonographer identified the probe site at one-third of the distance from the popliteal crease of the knee to the tip of the medial malleolus for the GM, and the lateral malleolus for the GL. The transducer probe was positioned perpendicular to the long axis of the leg, at the midpoint of the GL and GM muscle bellies, found at the center of each muscle halfway between its medial and lateral borders. Three ultrasound images were captured from each GM and GL at the left and right limb within one session, totaling 12 images per participant. These images were recorded digitally and sent to an external investigator for de-identification and randomization (www.randomizer.org). The de-identified and randomised images were analyzed using novel computer software designed in LabVIEW (version 16; National Instruments, USA). One investigator performed the digitisation of the blinded images, and from each image, three fascicles, three θs and a single measure of muscle thickness were calculated. As three images were taken per muscle, this gave a total of nine FLs, nine θs, and three measures of muscle thickness for each muscle belly. From these, the average was calculated.