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Rugby union prop Sally Fuesaina has the strength to pack a scrum, break tackles, and run over her opponents to crash over the try line.
But the energy she appears to have on the field is not always a reflection of how her body is coping.
"I could be on the field trying to move around, but there's not enough blood and oxygen flowing in my body for me to perform well," Fuesaina said.
"It does get frustrating because sometimes I'm thinking 'is it my performance, or is it my iron? Which one is it?'"
Fuesaina describes herself as a regular 32-year-old mum with two kids, who works in disability and aged care.
As well as that, she makes multiple five-hour round trips from Sydney to Canberra a week so she can play and train for the Brumbies.
Her stand-out season in this year's Super Rugby Women's competition led to her selection in the Wallaroos squad for the first time.
So feeling tired all the time was something she thought was due to her busy life and many commitments.
Low iron levels explained excessive fatigue
Fuesina grew up in a Samoan household where cultural and financial limitations meant iron-rich food like red meat was off the menu.
"I don't come from a really wealthy family, so it's like 'buy what you can get for your family'," Fuesaina said.
"We pretty much only ate white meat and we didn't really buy red meat because it was more expensive."
Feeling consistently tired was something she thought she just had to live with.
"Sometimes I'd just come from work, and I'd fall asleep straight away … I was really exhausted," she said.
It wasn't until she underwent a routine blood test while pregnant with her first child that doctors were able to provide an answer.
"They told me I had really low iron and if I didn't stay on top of that, I would need an iron infusion," she said.
"[I thought] is that why I've been sleeping all the time after training sessions?"
Iron deficiencies common in female athletes
On average, around one in three female athletes have an iron deficiency, compared to just one in 10 male athletes.
The staggering difference in the way iron deficiency impacts male and female athletes is what Australian Catholic University postdoctoral research fellow, Alannah McKay, has been researching for about eight years.
She said menstruation was the biggest contributing factor.
"We lose iron when we menstruate, so every time we have a period, we have blood loss which is associated with iron loss," Dr McKay said.
"So that's a significant gap in terms of how much more iron women need to eat each month to replace the amount of iron that's lost.
"The other potential cause is fluctuations in hormones like estrogen and progesterone, which may affect our ability to absorb iron in the diet."
How does a lack of iron impact athletic performance?
A lack of iron leads to fewer red blood cells, which affects how much oxygen is carried around the body to the muscles.
Exercise also causes hormonal disruptions that limit the body's ability to absorb iron from the diet for about six hours post-exercise.
Therefore, it impairs an athlete's aerobic capacity and fitness, which means they are often fatigued.
But relying on the symptoms of fatigue to indicate whether someone is iron deficient is particularly difficult for female athletes — like Fuesaina —who juggle so many commitments.
Dr McKay said she often saw athletes confused about the warning signs.
"When I say to somebody 'do you know you have really low iron stores? Are you feeling any symptoms? Are you fatigued?'" she said.
"They say 'oh, but I'm always tired, I have all the burden of working a full-time or part-time job, I have a family at home that I have to look after, and then on top of that I have to train ... I'm just tired whether my iron is healthy or not."
Dr McKay said people's upbringing and access to food could also have an impact on their iron levels.
"If you're talking also in terms of socio-economic status, or regions that are lacking in red meat, that is also going to have a big effect on how much iron you're obtaining from the diet," she said.
Increased screenings could help
Athletes in elite programs are encouraged to have regular screenings for iron deficiency.
In some cases. that could take place up to three times a year.
But Dr McKay said screening shouldn't be limited to just professional athletes.
"Anybody that's exercising regularly may need to have their iron screened a little bit more frequently, particularly females," she explained.
"You could be at risk of an iron deficiency even if you're just training three or four times a week, particularly running."
While iron cannot be produced by the body, Dr McKay said the hundreds of supplements on the market could be confusing, and consulting with a dietitian or GP was the best option to see improvements.
"Many [supplements] aren't going to be effective in treating an iron deficiency [as] there's very few that have enough iron in them," she said.
"So having really good advice around what supplements should be taken is important because you could choose a supplement that's either ineffective or is classed more as a multivitamin which could have a contamination risk from an anti-doping point."