As any saver knows, interest rates can go up as well as down. But they normally do so in conjunction with the economic cycle, and not with the physical activity of the account holder.

Now, a Ukrainian bank is offering better rates of interest to customers who prove they are taking 10,000 steps every day, as part of efforts to make its clientele not just richer, but healthier at the same time.

Monobank, a rapidly growing bank which has signed up more than half a million customers in just over a year, has offered the variable rate to about 1,500 savers on its mobile platform.

It works like this: customers use a smartphone health app to monitor their physical activity. Monobank accesses the data on a daily basis. People who manage the 10,000 steps are granted a rate of 21% on their savings. Anyone who fails to walk the walk for three days in a row will see their rate slump to 11%.

“I’m hoping to look fitter pretty soon,” says Alexey Drozdov as he marches through another chilly Kiev evening to clock up the mileage. “They say, ‘I bet you can’t do it every day.’ And I was like, ‘OK, I’ll prove you wrong.’

“Normally, a deposit only makes you happy at the end of a period; with this one, you can enjoy it every day because you get to show yourself that you have the guts to keep on going.”

The concept was devised by Monobank’s three CEOs, Dima Dubilet, Misha Rogalskiy and Oleg Gorokhovsky, in an effort to aid both personal and national economic wellbeing and address obesity-related health problems.

Ukraine has the second highest death rate from coronary heart disease in the world at 395.73 per 100,000; almost 50% of men are predicted to be obese by 2030.

“Everyone knows exercise is important but life often gets in the way,” said Dubilet. “If our sports deposit account gets people exercising more, that can only be a good thing – for our account holders and for Monobank.”

There were some early concerns about customers gaming the system – particularly when some users hit their 10,000 steps more quickly than humanly possible.

Bank officials quickly discovered that products were being sold to help run up the 10,000 steps without human involvement. The offenders were punished with an immediate relegation to the lowest interest rate. Of the broad customer base, more than 50% are managing the step count to qualify for 21% returns on their deposits.

Bank officials did not say whether there were any special terms for disabled people.

Monobank’s approach and rapid success reflects Ukraine’s booming financial technology scene, with 58% of the nation’s fintech companies launching since 2015.

The country’s technology sector is strong generally, and startups based in Ukraine or founded by a Ukrainian raised $265m in 2017.

Amazon bought the video doorbell firm Ring for $1bn in February, while Snapchat bought augmented reality startup Looksery for $150m.

Dubilet argues that the conditions endured by Ukrainians since conflict broke out in 2014 have motivated young entrepreneurs to seek ways to improve day-to-day life. He wants to increase the number of Ukrainians using the “sports deposit” account and is looking to collaborate with both healthcare professionals and the government in Kiev.

Monobank would also like to launch its sports deposit platform in the UK, possibly in early 2019.