The retailer, controlled by Mike Ashley, has reportedly sent an internal document to staff - seen by the PA News agency - setting out a range of lines where it said the increases should apply.
It comes after the chain u-turned and said it will not open its stores "until given the go ahead by the government" after Boris Johnson's toughened measures to fight the coronavirus pandemic.
Sports Direct operates a system of having "ticket" prices, followed by "reduced" stickers, meaning that it can be unclear at what price a product was ever sold.
The pricing documents uncovered by PA News show that an Everlast 4kg kettle bell has gone up from £9.99 to £14.99 - although the sticker will still say the "original" ticket price was £19.99.
The cost of a 12kg kettle bell by Everlast, which is owned by Sports Direct's parent company Frasers Group, is now £39.99, up from £29.99.
Other items include Slazenger, Lonsdale and several other well-known brands which are owned by Frasers.
The retailer was already in the spotlight for its response to the prime minister's announcement of a lockdown in the UK including the closure all shops selling non-essential goods,? clothing and electronic stores among them.
He also made it clear that only key workers should be travelling to work and people should only be going to shops in order to buy food or collect medicines and prescriptions.
But in a letter to staff of Mike Ashley's Frasers Group, which includes Sports Direct and Evans Cycles, finance chief Chris Wootton appeared to suggest the company's outlets are essential in the fight against COVID-19 and that staff were therefore key workers.
"We stock a huge range of sports equipment designed for exercising at home... indeed home fitness is the number one trending topic on social media after coronavirus itself," he wrote.
"Against the backdrop of the closure of gyms the demand for these types of products has increased exponentially as the population looks to maintain a healthy lifestyle.
"Consequently, we are uniquely well placed to help keep the UK as fit and healthy as possible during this crisis and thus our Sports Direct and Evans Cycles stores will remain open where possible to allow us to do this (in accordance with the Government's current social distancing guidance).
"There is no one else that has the range of product and range of stores to make this reasonably accessible for the whole population."
He has since clarified his comments, saying that its stores would not open to the public unless given the green light to do so by the government.
Earlier on Tuesday, Sky's Inzamam Rashid - in Kingston, southwest London - said he saw the manager of a store there arriving for work this morning.
He said: "I asked him if he's really a key worker, and he just shrugged his shoulders.
"I questioned whether this was something he has to do, and he just replied 'we have to do it'."
Pets at Home, the UK's leading pet care business, is among non-grocery and pharmacy chains staying open, in line with guidance that it is an essential service.
In a Tweet, it said "feeding the nation's pets is vital to us".
As high streets shut down, chief executive of the British Retail Consortium Helen Dickinson said: "Retailers understand the need for government to act quickly and decisively to protect public health and combat coronavirus.
"The safety of customers and staff is paramount, which is why retailers have responded swiftly and positively to evolving government guidance on social distancing and other hygiene matters. Indeed, many retailers had gone further and already closed shops temporarily."
Sports Direct rival, JD Sports, said it had closed its stores in the UK, Europe and US.
Its boss, Peter Cowgill, said on Tuesday: "Along with everyone else, the group is experiencing major disruption to our business operations as we seek to protect our colleagues and customers from the effects of COVID-19.
"Their safety remains our number one priority and we continue to take all appropriate action in line with government advice in our various territories."
Commenting on the Sports Direct row, chief markets analyst at markets.com, Neil Wilson, said: "Quite what another pair of discount trainers and jogging bottoms will do (to) make you healthier is hard to fathom.
"Mike Ashley is never one to toe the line. Yesterday, Frasers cancelled the buyback after saying on Friday it would not.
"Management admitted that the prior announcement 'substantially underplayed the effect of the COVID-19 virus on retail'.
"Another u-turn came this morning with a 'clarification' from the CFO (chief financial officer) saying that no shops would be open without a green light from the government."