Robots have become common in warehouses across America.Warehouses are centers where products are stored and organized before they are sent to buyers.Manufacturers of robots say the machines can do the most repetitive and difficult jobs.But critics warn that they are also creating new forms of stress and even injuries.Amanda Taillon's job is to enter a robot-only areato fix problems in one of Amazon's warehouses in the state of Connecticut.Sometimes she has to pick up a fallen toy or ease a traffic jam.She uses a belt that works like a superhero's force field.It can command the nearest robots to stop and the others to slow down or change their paths."They weigh a lot," she said of the robots.Critics say that this kind of human-machine cooperation has its problems.They say that keeping up with the pace of the new technologyis hurting human workers' health and morale.Beth Gutelius studies urban economic development at the University of Illinois at Chicago.She has spoken with warehouse operators around the U.S.She said human burnout is a problem in warehouseswhere robotics and artificial intelligence, or AI software are being used.She said that is because the robots add more workand increase the pressure on workers to speed up their performance.Recently, reporters investigated injury rates at Amazon warehouses.They found that robotic warehouses reported more injuries than those without the machines.Reporters with the Center for Investigative Reporting's website Revealstudied records from 28 Amazon warehouses in 16 states.They found that the rate of serious injurieswas more than two times the warehousing industry average.Amazon, however, says that it is misleading to compare its rate with other companies.That is because the company says it has an "aggressive stanceon recording injuries no matter how big or small."The Reveal report also found a connection between robots and safety problems,such as in Tracy, California.There, the serious injury rate nearly quadrupled in the four years after robots were introduced.Amazon has not released information on how its safety recordat robot-powered warehouses compares to those without.But company officials believe that Amazon workers are able to deal with the new technology.Companies say they cannot quickly fulfill buyers' demands for packageswithout fast-moving pods, robots and other forms of automation.The increased use of robots and AI is changing warehouse workin a way that the head of Amazon Robotics says can "extend human capability."The idea is that robots can help people to do what they are best at: problem solving.Tye Brady is Amazon Robotics' chief technologist.He said having people and robots work together permits the company to offer lower prices.Brady said worker safety remains very important.But Gutelius, the University of Illinois researcher,said that the hope for easy human-machine operations is not a reality."It sounds quite lovely, but I rarely hear from a worker's perspectivethat that's what it feels like," she said.Amazon has more than 200,000 "drives," or robotic vehicles,that move goods through its warehouses around the U.S.That is two times the number it had in 2018.Much of the growth in warehouse robotics came in 2012 when Amazon bought Kiva Systems.Afterwards, Kiva Systems became Amazon Robotics.For seven years, the company has been designing and building Amazon's robots.Amazon's move to buy Kiva influenced its competitors, said Jim Liefer.He is chief of the San Francisco company, Kindred AI.It makes an AI robotic arm used by companies such as The Gap clothing store.Melonee Wise is chief of California-based Fetch Robotics.The company sells robotic carts.She credits Amazon with causing the industry to develop new technologies.But she said Amazon's system forces workers to do "un-ergonomic moves"such as reaching up very high or down low."They have robots that live in cages," she said."Our robots are designed to work safely around people."Taillon, the Amazon employee you met at the beginning of this report,said that she has gotten used to working with robots.She described how she felt when first working with them."When you're out there, and you can hear them moving around,but you can't see them, it's like,‘Where are they going to come from?'," she said."It's a little nerve-racking at first."And I'm John Russell.