Background: the aim of the study was to develop and validate a specific perception velocity scale for the Back Squat exercise to discriminate the velocity of each repetition during a set. Methods: 31 resistance trained participants completed 3 evaluation sessions, consisting of 3 blinded loads (light, medium, heavy). For each repetition, barbell mean velocity (Vr) was measured with a linear position transducer while perceived velocity (Vp) was reported using the Squat Perception of Velocity (PV) Scale. Results: Pearson correlation coefficients (r) showed very high values for each intensity in the 3 different days (range r = 0.73–0.83) and practically perfect correlation for all loads (range r = 0.97–0.98). The simple linear regression analysis between Vp and Vr revealed values ranging from R2 = 0.53 to R2 = 0.69 in the 3 intensities and values ranging from R2 = 0.95 to R2 = 0.97 considering all loads. The reliability (ICC2.1, SEM) of Vp was tested for light (0.85, 0.03), medium Please do not modify the format of the manuscript (type and size of font, margin size, paragraph spacing, etc.), only what is indicated with comments or highlighted, as it follows the standard style of MDPI. We would appreciate if you could mark all the modifications with the Track Changes tool and thoroughly address all the comments.(0.90, 0.03) and heavy loads (0.86, 0.03) and for all loads (0.99, 0.11). The delta score (ds = Vp − Vr) showed higher accuracy of the PV at heavy loads. Conclusions: these results show that the PV Squat Scale is a valid and reliable tool that can be used to accurately quantify exercise intensity.

Football is a popular sport, but little is known about the youth-to-senior transition rates in elite players, particularly in large and successful countries. This study aims to investigate the youth-to-senior transition rate in the Italian national football team, both prospectively and retrospectively, and to explore if Relative Age Effects (RAEs) affect this transition. Data from 885 players selected in youth and senior Italian national teams between 2000 and 2021 were included in the study. For each player, the birthdate and the number of selection in Under 16, 17, 19, 21 and senior team was considered. The transition rate was determined by the number of youth players competing in the Senior National team (and vice versa), whilst birth quarter (Q) distributions with a chi-square goodness-of-fit test. Prospectively, the transition rate increased as age increased (i.e., from ~20% in U16 to ~50% in U19). Retrospectively, less than 10–20% of youth players were subsequently selected for the senior team. Data revealed a skewed birth date distribution in all age groups, and the RAEs magnitude decreased when age increased (i.e., ORs for Q1 vs Q4 was ~ 9 in U16 and ~ 1.7 in senior teams). Nevertheless, the RAE magnitude was smaller for successfully transitioned players. In conclusion, most players in the senior team were not previously selected for youth teams suggesting that junior international experience may not be a prerequisite for later success. Moreover, while the birthdate strongly influences the selection of youth national teams, its impact is less evident in the youth-to-senior transition.

The perception of bar velocity (PV) is a subjective parameter useful in estimating velocity during resistance training. The aim of this study was to investigate if the PV can be improved through specific training sessions, if it differs between the back squat (SQ) and bench press (BP), and if there are differences in perception accuracy in the different intensity zones. Resistance-trained participants were randomly divided in an experimental (EG, n = 16) or a control group (CG, n = 14). After a familiarization trial, both groups were tested before and after 5 weeks of training. The PV was assessed with five blinded loads covering different intensity domains. During the training period, only the EG group received velocity feedback for each repetition. Prior to training, both groups showed a greater PV accuracy in the SQ than in the BP. Post training, the EG showed a significant reduction (p < 0.05) in the delta score (the difference between the real and perceived velocity) for both exercises, while no significant differences were observed in the CG. Prior to training, the perceived velocity was more accurate at higher loads for both exercises, while no difference between loads was observed after training (EG). The results of this study demonstrate that the PV improves with specific training and that differences in the accuracy between loads and exercise modes seen prior to training are leveled off after training.