As part of the new rules, referees will add the exact time lost in goal celebrations, substitutions or injuries to stoppage time, while in previous seasons, the policy was to aggregate a nominal period of time.
There were eight minutes of added time in the second half of Arsenal's Community Shield win over Manchester City last weekend, while several matches in England's second-tier Championship's first round had 10 or more minutes of added time.
Manchester United defender Raphael Varane (30) had criticised the authorities, saying this week the move increased player workload in an already packed schedule, and PFA chairman Maheta Molango echoed the Frenchman.
"What (Varane) is saying is: 'This is not sustainable'. And it's only the start of the problem because by next year, when we open the new cycle, it's going to be absolutely crazy. We are sleepwalking into a disaster," Molango told the BBC.
"It's getting to a stage where it's not about us telling them to take action. It is that they want to take it themselves. So, what we're saying to the authorities is that you're bringing this to an extreme.
"It's not going to be a question of the union saying: 'Do this or that.' It's players themselves who are saying to us: 'Let's do something.'... It's not manageable and if you don't do something we're going to be in trouble."
Varane retired from international duty in February, ending a 10-year career with France in which he won the World Cup in 2018 and was a runner-up four years later.
"This would never have happened 20 years ago," Molango added.
"Someone who would have been the next captain of the French national team says: 'I'm not going to play.'
"If Varane does that other people will follow suit."
Molango said the packed schedule and long matches also took a mental toll on players.
"People then say: 'Let's talk about the sleeping pills players take,' but this is a result of that," he said.
"If I play an international game on the Thursday in Bolivia and then I play at Birmingham on Saturday, how do I do that? I need to travel for 24 hours, get some sleep somehow and play on Saturday."
Follow all the drama from the new Premier League season on Flashscore.
