Abstract
Background: Participating in physical activity and exercise for the majority of the population promotes beneficial health outcomes. However, some individuals have an energy intake which is insufficient to replace the energy expended during exercise to such an extent that there is not enough energy for the body to meet all of its physiological functions. This leads to a state of low energy availability (LEA). Recently research has suggested that LEA has effects on areas of health which extend beyond bone health and reproductive function, including an increased risk for cardiovascular and metabolic health. Research investigating this association is limited, with existing literature using a combination of blood lipids, flow-mediated dilation and questionnaire data to examine cardiovascular and metabolic health mostly in females and in individual endurance sports. Studies using these measures show that those at risk for LEA had detrimental changes in blood lipids and flow-mediated dilation compared to those not at risk of LEA. This provides evidence that LEA is associated with unfavourable lipid profiles and endothelial dysfunction and therefore illustrates that LEA may be associated with changes to the cardiovascular system, especially in those involved in endurance sports. Whether this extends to those involved in team sports is unknown.
Objective: The aims of this study were to determine if elite New Zealand female rugby sevens players are at risk of LEA, to describe the lipid and arterial stiffness profiles of elite New Zealand female rugby sevens players, and to compare those at risk and not at risk of LEA.
Design: A sample of 20 elite New Zealand female rugby sevens players participated in the study with measures being collected at two time points, five months apart. LEA status was assessed using the Low Energy Availability in Females Questionnaire (LEAF-Q), resting metabolic rate (RMR), five-day diet record, and dual-energy x-ray absorptiometry (DEXA). Cardiovascular health was assessed by measurement of blood lipids and measures of cardiovascular function and arterial stiffness including pulse wave velocity and blood pressure.
Results: Results from this study found that 55% of participants, when using the LEAF-Q, were classified as being at risk of LEA, and 45% of participants were classified as not being at risk of LEA. When using an RMR cut off of ≤29 kcal.kg-1FFM.d-1 to depict LEA, a similar prevalence was found with 58% of participants being classified as at risk of LEA and 42% of participants being classified as not at risk of LEA. Heart rate for those at risk of LEA showed a pattern towards being higher (68.1 ± 24.0 bpm) compared to those not at risk of LEA (61.3 ± 7.2 bpm), representing a mean difference of 6.8 bpm (95% CI: -10.9, 24.5). No differences for brachial systolic pressure, brachial diastolic pressure, or pulse pressure were evident between those at risk for LEA and those not at risk. At time point two those at risk of LEA showed patterns towards having lower high-density lipoprotein (HDL) and higher triglycerides than those not at risk of LEA. Mean differences between groups were 0.26 mmol/L (0.06, -0.57) and 0.22 mmol/L (0.48, -0.03) for HDL and triglycerides representing a 15% decrease and 31% increase respectively. Pulse wave velocity for those at risk of LEA showed a pattern towards being higher (6.55 ± 1.54 ms-1) compared to those not at risk of LEA (5.69 ± 1.11 ms-1), representing a mean difference of 0.86 ms-1 (95% CI: -0.68, 2.40).
Conclusion: These results show that 55-58% of elite New Zealand female rugby sevens players are at risk of LEA as assessed by LEAF-Q and RMR. This novel finding suggests that further monitoring of these team players is required along with further investigation into the risk of LEA in other female athletes in New Zealand. Assessment of the cardiovascular health of these athletes showed patterns towards small differences existing between those at risk and those not at risk of LEA, suggesting that those at risk may have higher risk of cardiovascular disease in the future. Further investigation is needed into the health consequences of LEA, and whether these athletes may be at increased risk for poorer health outcomes.