Limitations
The inability to perform laboratory-based research due to COVID-19 restrictions did impede our ability to rigidly standardize, control, and supervise the training and testing. Yet, the Cooper 12-minute run test overcame several practical constraints to estimating cardiorespiratory fitness, within a field-based setting, during a period of high COVID-19 restrictions. Therefore, laboratory-based exercise protocols are warranted.We recognize that the control group should have refrained from exercise and adhered to their regular routines. However, due to participants being confined to their residences, uptake of self-directed physical activity was not uncommon during the UK national lockdown. Though, to this studies benefit, this additional uptake in physical activity did not result in any significant improvements in Cooper run test scores in the control group.Finally, a larger sample size for the allele subgroups is necessary and is a limitation of this study. In particular, low sample size meant that allele could not be identified i.e. for 28% of the SNPs alleles with low frequencies were not represented within our cohort and had to be removed, prior to analysis. Consequently, such SNPs should not be disregarded as insignificant as some rare variants could be identified with larger sample sizes. Therefore, greater sample sizes are necessary for genetic studies.