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The aims of this study were to compare the influence of transition game (TG) size on the external and internal loads of young professional soccer players and to describe the high-speed profile of these drills in response to pitch dimensions. Eighteen young professional soccer players (age: 16.1 ± 0.3 years; height: 178.3 ± 5.4 cm; weight: 70.1 ± 6.2 kg) performed a 3vs2 TG on pitches measuring 40 × 30 m (TG 30 ), 40 × 50 m (TG 50 ) and 40 × 70 m (TG 70 ) m. Distance covered (DC); accelerations-decelerations above 1.0 m · s -2 and 2.5 m · s -2 ; rate of perceived exertion (RPE); maximal heart rate and time above 90%; DC at 18.0 to 21.0 km · h -1 (DC 18-20.9 km · h -1 ); DC at 21.0 to 23.9 km · h -1 (DC 21-23.9 km · h -1 ); DC above 24.0 km · h -1 (DC > 24 km · h -1 ); and peak speed and sprint profile (duration, distance and maximal speed) were measured. TG 30 achieved lower DC, DC above 18 km · h -1 , peak speed, sprint distance and RPE than TG 50 and TG 70 (p < 0.01 and p < 0.05) and lower sprint duration and maximal speed sprint than TG 70 (p < 0.01). TG 30 and TG 50 achieved higher Acc > 1.0 and > 2.5 m · s -2 respectively than TG 70 (p < 0.05). TG 70 showed greater DC above 21 km · h -1 , peak speed, sprint distance and maximal speed sprint than TG 50 (p < 0.01). Soccer coaches should use larger TGs to overload variables related to high speed and sprint demands during training and smaller TG formats to stimulate the accelerations of the soccer players., Competing Interests: The authors declare no conflict of interest., (Copyright © Biology of Sport 2023.)

The purpose of this study was to compare the fascicle length, angle pennation and mechanical properties of the biceps femoris long head (BFlh) in dominant and non-dominant limbs in previously injured and uninjured professional football players. Fifteen professional football players were recruited to participate in this study. Seven players had suffered a BFlh injury during the previous season. Myotonometry mechanical properties were measured in the proximal, common tendon and distal BFlh using MyotonPRO, and angle pennation and fascicle length were also measured. We observed significantly higher distal BFlh frequency, stiffness, decrement, relaxation and creep than in the common tendon and proximal BFlh. The previously injured players showed significantly higher frequency and stiffness, and lower relaxation and creep in the dominant BFlh than did uninjured players. There were no significant differences between the fascicle length and angle pennation in previously injured and uninjured BFlh. Myotonometric measurement provides a quick and inexpensive way to check the properties of the BFlh in professional football players. Professional football players with previous BFlh injury showed higher intrinsic tension and a poorer capacity to deform than did players with no injury to the BFlh., Competing Interests: The authors declared no conflict of interest., (Copyright © Biology of Sport 2023.)