Preparedness for Competition in Highly Trained Adolescent Swimmers: Integrated Nutrition and Physiology

Newbury, Josh (2023) Preparedness for Competition in Highly Trained Adolescent Swimmers: Integrated Nutrition and Physiology. Doctoral thesis, Birmingham City University.

Josh Newbury PhD Thesis published_Final version_Submitted Jun 2023_Final Award Sept 2023.pdf - Accepted Version

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Swimmers will undergo large training loads during early adolescence to develop the physical and technical characteristics for elite competition, therefore daily nutrition practices to support health and performance are important at this critical age.

Past research suggested that adolescent swimmers often consumed inadequate energy and carbohydrate intakes to support their training; though, whether this research remains accurate is questionable considering given that studies were mostly based on singular assessment time points prior to the COVID-19 pandemic. As such, Chapter 3 observed the current daily nutrition intakes of highly trained adolescent swimmers in the UK, showing this population adapted, yet achieved the macronutrient recommendations before (carbohydrate [CHO]: 5.4 ± 1.2g·kg BM-1; protein: 2.3 ± 0.4 g·kg BM-1; fat: 1.6 ± 0.4 g·kg BM-1), during (CHO: 3.5 ± 1.1 g·kg BM-1; protein: 1.7 ± 0.4 g·kg BM-1; fat: 1.1 ± 0.3 g·kg BM-1), and after (CHO: 5.4 ± 1.4 g·kg BM-1; protein: 2.1 ± 0.6 g·kg BM-1; fat: 1.5 ± 0.6 g·kg BM-1) a COVID-19 lockdown.

Since adolescent swimmers appeared to appropriately support their daily health and performance through dietary intake, attention was then turned to supplement use. Chapter 4 demonstrated that supplement use was highly prevalent across the swimming talent pathway, with swimmers at the development talent stage utilising approximately four different nutritional supplements (~3 sports foods, ~1 health supplement) that were mostly informed by parents/guardians (74%), whereas national-level swimmers used a wider range of supplements (~3 health, ~3 sports, ~2 ergogenic) following greater access to performance nutrition support (i.e., nutritionists informed 51% of supplement use). Despite the widespread supplement use, however, Chapter 5 showed that adolescent swimmers had low adherence to vitamin D supplement recommendations, resulting in 70% of the population developing an ‘insufficient’ circulating vitamin D (<75 nmol·L-1) status between the autumn and winter training periods.

Indeed, adolescent swimmers were most likely to use supplements for performance (35%) rather than health (12%), even though ergogenic aids currently have unclear performance outcomes for competitive swimmers. Consequently, Chapters 6–8 sought to explore the effects of acute ergogenic aids during practical swimming scenarios, although the outcomes appeared to question their application in the real world.

Firstly, caffeine (3 mg·kg BM-1) provided no benefits towards a simulated 100 m competition performance (59.5 ± 7.8 s vs. 59.9 ± 7.9 s, g = 0.07), nor did it appear to impair a repeated performance the next morning after sleep (59.7 ± 7.7 s vs. 60.2 ± 7.9 s, g = 0.06). The second ergogenic aid under scrutiny was sodium bicarbonate (NaHCO3; 0.3 g·kg BM-1), which was shown to produce highly individual time to peak blood bicarbonate (HCO3-) concentrations in Chapter 7a (between 75–180 min post-ingestion). Yet, when this individualised approach (IND) was compared to a standardised approach (STND; 150 min pre-exercise) in practice, neither NaHCO3 approach improved 6 x 75 m swimming interval swimming (mean interval time: IND: 47.3 ± 5.1 s, STND: 47.8 ± 6.0 s, PLA: 48.0 ± 5.5 s, all g <0.20), nor a follow-up 200 m time-trial after a 30 min recovery period (IND: 2:11.0 ± 8.2 s, STND: 2:11.5 ± 7.1 s, PLA: 2:11.1 ± 7.1 s, all g <0.20). Finally, the ingestion of citrulline malate (15 g) was also unsuccessful at improving 6 x 300 m interval swimming versus a placebo supplement (3:32.0 ± 9.6 vs. 3:32.8 ± 7.7 s, g = 0.09), despite the proposed ergogenic mechanisms appearing to align with whole-body, repeated aerobic efforts.

Collectively, these studies suggest that highly trained adolescent swimmers should place emphasis on achieving the recommended daily energy and nutrient requirements to achieve optimal preparedness for swimming competitions, rather than relying on ergogenic aids. However, it should be noted that this thesis only considered a small proportion of supplements, dosing strategies, and practical scenarios; therefore, further research is required before the potential benefits of ergogenic aids are dismissed in this cohort.

Item Type: Thesis (Doctoral)
26 June 2023Submitted
10 September 2023Accepted
Uncontrolled Keywords: Sport nutrition; swimming; competition nutrition; adolescent athletes; supplements; vitamin D; ergogenic aids; performance
Subjects: CAH03 - biological and sport sciences > CAH03-02 - sport and exercise sciences > CAH03-02-01 - sport and exercise sciences
Divisions: Doctoral Research College > Doctoral Theses Collection
Faculty of Health, Education and Life Sciences > College of Life Sciences
Depositing User: Jaycie Carter
Date Deposited: 20 Dec 2023 14:37
Last Modified: 12 Jun 2024 13:01

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