Nutritional intakes of highly trained adolescent swimmers before, during, and after a national lockdown in the COVID-19 pandemic.

Strict lockdown measures were introduced in response to the COVID-19 pandemic, which caused mass disruption to adolescent swimmers' daily routines. To measure how lockdown impacted nutritional practices in this cohort, three-day photograph food diaries were analysed at three time points: before (January), during (April), and after (September) the first UK lockdown. Thirteen swimmers (aged 15 ± 1 years) from a high-performance swimming club submitted satisfactory food diaries at all time points. During lockdown, lower amounts of energy (45.3 ± 9.8 vs. 31.1 ± 7.7 kcal∙kg BM∙day-1, p<0.001), carbohydrate (5.4 ± 1.2 vs. 3.5 ± 1.1 g∙kg BM∙day-1, p<0.001), protein (2.3 ± 0.4 vs. 1.7 ± 0.4 g∙kg BM∙day-1, p = 0.002), and fat (1.6 ± 0.4 vs. 1.1 ± 0.3 g∙kg BM∙day-1, p = 0.011) were reported. After lockdown, no nutritional differences were found in comparison compared to before lockdown (energy: 44.0 ± 12.1 kcal∙kg BM∙day-1; carbohydrate: 5.4 ± 1.4 g∙kg BM∙day-1; protein: 2.1 ± 0.6 g∙kg BM∙day-1; fat: 1.5 ± 0.6 g ∙kg BM∙day-1, all p>0.05), despite fewer training hours being completed (15.0 ± 1.4 vs. 19.1 ± 2.2 h∙week-1, p<0.001). These findings highlight the ability of adolescent swimmers to alter their nutrition based on their changing training circumstances when receiving sport nutrition support. However, some individuals displayed signs of suboptimal nutrition during lockdown that were not corrected once training resumed. This warrants future research to develop interactive education workshops that maintain focus and motivation towards optimal nutrition practices in isolated periods away from training.

The time to peak blood bicarbonate (HCO3-), pH, and the strong ion difference (SID) following sodium bicarbonate (NaHCO3) ingestion in highly trained adolescent swimmers.

The timing of sodium bicarbonate (NaHCO3) supplementation has been suggested to be most optimal when coincided with a personal time that bicarbonate (HCO3-) or pH peaks in the blood following ingestion. However, the ergogenic mechanisms supporting this ingestion strategy are strongly contested. It is therefore plausible that NaHCO3 may be ergogenic by causing beneficial shifts in the strong ion difference (SID), though the time course of this blood acid base balance variable is yet to be investigated. Twelve highly trained, adolescent swimmers (age: 15.9 ± 1.0 years, body mass: 65.3 ± 9.6 kg) consumed their typical pre-competition nutrition 1-3 hours before ingesting 0.3 g∙kg BM-1 NaHCO3 in gelatine capsules. Capillary blood samples were then taken during seated rest on nine occasions (0, 60, 75, 90, 105, 120, 135, 150, 165 min post-ingestion) to identify the time course changes in HCO3-, pH, and the SID. No significant differences were found in the time to peak of each blood measure (HCO3-: 130 ± 35 min, pH: 120 ± 38 min, SID: 98 ± 37 min; p = 0.08); however, a large effect size was calculated between time to peak HCO3- and the SID (g = 0.88). Considering that a difference between time to peak blood HCO3- and the SID was identified in adolescents, future research should compare the ergogenic effects of these two individualized NaHCO3 ingestion strategies compared to a traditional, standardized approach.