USADA ruled that the 45-year-old Czech rider who resides in California was exposed to appetite stimulant capromorelin "through no fault of her own" following its investigation.

Nash’s positive urine sample was detected following an out-of-competition test conducted on October 24 last year.

Capromorelin is not specifically listed on the World Anti-Doping Agency’s Prohibited List but is considered a "non-specified substance" in the class of peptide hormones, growth factors, related substances and mimetics, according to USADA.

It is also prohibited under USADA and UCI rules.

Nash, who represented the Czech Republic in cross-country mountain biking at the London 2012 Olympics, faced the possibility of a four-year suspension.

But USADA announced that no sanction would be imposed following its findings.

"She was administering the medication orally to her dog each day during the final weeks of her pet’s life in an effort to maintain weight," a statement from USADA read.

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"Due to the difficulty of administering oral pet medication, Nash would frequently come into contact with the liquid medication via her hands, and the medication bottle did not warn users about the risk of contamination from transdermal exposure.

"USADA, together with laboratory experts, conducted a study of transdermal exposure using the same pet medication containing capromorelin, which established that coming into direct contact with the pet medication would cause a positive test.

"Importantly, these studies demonstrated that the athlete’s exposure scenario with the medication correlated with the trace levels, 0.07 ng/mL (70 parts per trillion), of capromorelin found in her urine sample.

"There is currently no threshold for capromorelin, so any level triggers an adverse analytical finding. USADA therefore concluded that Nash had no fault or negligence with respect to the presence of capromorelin in her sample."

The UCI said it "takes note of the decision" by USADA that Nash "bears no fault or negligence".

Nash competed internationally in cross-country skiing, representing Czech Republic at the Nagano 1998 and Salt Lake City 2002 Winter Olympics.

Since switching to cycling, Nash has earned cyclo-cross world bronze medals in 2011 and 2017 and achieved eight World Cup wins across mountain biking and cyclo-cross.

Nash was elected vice-president of the UCI in September 2021 before being re-elected as head of the organisation’s Athletes’ Commission later that year.

Following USADA's ruling, Nash said she found the "process was emotionally brutal" after finding out about the positive test just a few weeks after her dog's death.

"I can only hope my case can help others and perhaps lead to changes in the anti-doping system," Nash posted on Instagram.

"This story and period of life is painful to repeat but tomorrow is a new day and I promise myself to start moving on."

Travis Tygart, chief executive of USADA, called for a change in the rules following the investigation into Nash’s case.

"If there is no question that an athlete comes into contact with a prohibited substance from a completely innocent source and there is no effect on performance, USADA continues to advocate that there should not be a violation or a public announcement," said Tygart.

"The rules must change and all of us must wake up and demand a more fair and just global anti-doping system that catches and sanctions intentional cheats who rob clean athletes but does not railroad innocent athletes.

"As in this case, we always work as hard to try to exonerate the truly innocent as we do to convict those who intentionally cheat."