In April 2014, Phelps announced he would come out of retirement, and would enter an event later that month. In May 2014, he won the 100-meter butterfly event at the Arena Grand Prix in Charlotte, North Carolina. Phelps was reportedly motivated by the national team's failure to win the men's 4 × 100 m freestyle relay since their Beijing 2008 and Rome 2009 titles. The relationship between Phelps and coach Bob Bowman had deteriorated in the preparations for London 2012, so Phelps convinced a skeptical Bowman that he "wasn't training for history. He wasn't training for the medals. He wasn't even training for all the fans. This time Phelps wanted to swim for himself...and enjoy the journey". Since his returning from retirement in 2014, Phelps "scaled back his calorie intake" and "increased his postswim ice baths". By the 2016 Olympic Trials, despite his age Phelps "felt physically stronger in the water, perhaps because of drills Bowman added to his pool workouts, like multiple repeats of 40 seconds of dolphin kicking while hugging a 10-pound weight to his chest".