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Early specialisation versus early diversification in long-term athlete development remains controversial. Although several parameters of sport specialisation have already been explored, this study investigates within-sport specialisation in the careers of young swimmers. In this cohort study, the number of strokes, events and distance categories during childhood and adolescence, as well as entry age were analysed to find potential correlations with success at age 18. Also, national team members were compared to non-members within this cohort. The number of events, strokes or distance categories at a younger age showed a moderate correlation to the best FINA point score at the age of 18, i.e. the greater the diversification, the greater the performance at age 18. The number of events, strokes or distance categories however, showed a stronger correlation when comparing national team members with the non-members. Most of the observed athletes were more likely to have high FINA points at 18 if they had been listed in the top 100 at 11 years of age. Entry age had a strong negative correlation with the FINA point score at 18, i.e. the younger the athlete when entering the top 100, the higher the FINA point score at 18. When national team members were compared to non-national team members, early age of entry into the top 100 showed a greater impact on the national team members. However, being listed in more than one stroke as a child correlates well with success at age 18.

Relatively older athletes have a greater probability of being selected and subsequently exposed to a higher level of coaching, training and other talent-promoting factors. Grouping by chronological age is, therefore, considered to be one of the weaknesses in talent identification. A large number of studies have confirmed the prevalence of the relative age effect (RAE) across various sports, including swimming. This investigation aims to quantify the prevalence, magnitude and transient pattern of the RAE according to sex and events across German swimmers. The RAE was examined top-100 ranked swimmers (2004–2013) according to birth month, of three cohorts (born 1993–1995; n = 3630) for the age groups 11–18. The Χ2 tests and Cramer’s V estimated effect sizes; odd’s ratios and confidence intervals calculated relative discrepancies between the quartiles. The RAE is significantly present over all events for female swimmers until 13–15 and for males until 16–18 years of age. Effect sizes were moderate until 12/13 years of age for females and 14/15 years of age for males. No inverted effects were visible. Compared to previous reports on Australian as well as Portuguese cohorts, the RAE was prevalent over a longer time period. Therefore, the impact of negative outcomes from RAE appears to be greater among German age group swimmers.

Peak oxygen uptake (VO 2 peak) and speed at first (LT1, minimal lactate equivalent) and second lactate threshold (LT2 = LT1 +1.5 mmol•L −1 ) are crucial swimming performance surrogates. The present randomized controlled study investigated the effects of blood flow restriction (BFR) during low-intensity swimming (LiT) on VO 2 peak, LT1, and LT2. Eighteen male swimmers (22.7 ±3.0 yrs; 69.9 ±8.5 kg; 1.8 ±0.1 m) were either assigned to the BFR or control (noBFR) group. While BFR was applied during LiT, noBFR completed the identical LIT without BFR application. BFR of the upper limb was applied via customized pneumatic cuffs (75% of occlusion pressure: 135 ±10 mmHg; 8 cm cuff width). BFR training took place three times a week over 5 weeks (accumulated weekly net BFR training: 60 min•week −1 ; occlusion per session: 2-times 10 min•session −1 ) and was used exclusively at low intensities. VO 2 peak, LT1, and LT2 diagnostics were employed. Bayesian credible intervals revealed notable VO 2 peak improvements by +0.29 L•min −1 kg −1 (95% credible interval: −0.26 to +0.85 L•min −1 kg −1 ) when comparing BFR vs. noBFR. Speed at LT1 −0.01 m•s −1 (−0.04 to +0.02 m•s −1 ) and LT2 −0.01 m•s −1 (−0.03 to +0.02 m•s −1 ) did not change meaningfully when BFR was employed. Fifteen sessions of LIT swimming (macrocycle of 5 h over 5 weeks) with a weekly volume of 60 min with BFR application adds additional impact on VO 2 peak improvement compared to noBFR LIT swimming. Occasional BFR applications should be considered as a promising means to improve relevant performance surrogates in trained swimmers. Highlights. Low-intensity swimming with blood flow restricted (BFR) induced superior peak oxygen consumption adaptations compared to non-restricted swimming training over a 5-week lasting training period . BFR and non-BFR swimming training-induced similar adaptations regarding swimming speed at first and second lactate threshold . In conclusion, BFR served as a feasible, promising and beneficial complementary training stimuli to traditional swimming training regarding oxygen consumption adaptations.

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