Britain's top 400m runner Tim Benjamin says he has been surprised by the severity of his training programme under new coach Colin Jackson.
The Welshman, 24, said: "Colin works me so hard I've been sick on the track.
"He is really tough. What surprises me is the standard that he sets, particularly the time on the track he wants you to hit.
"It's very different to any training I've done before. I do a lot more strength work in the gym."
Benjamin hooked up with Jackson in September after leaving Tony Lester's Berkshire-based training stable to return to south Wales.
"The main aim is to maintain a healthy winter"
Jackson, the former 110m hurdles world record holder, has also recruited Olympic 400m gold medallist Michael Johnson to help Benjamin, although his input has yet been called upon.
Benjamin's injury problems continued last season as a knee problem forced him to miss the Commonwealth Games and severely hindered his preparations for the European Championships, where he finished sixth.
He has decided to miss the entire indoor season to concentrate on getting back to full fitness ahead of next August's World Championships in Osaka.
"The main aim is to maintain a healthy winter and hopefully that will speak volumes on the track when it comes to performances," said Benjamin.
"I'm hoping to race a lot earlier than I'm used to, so I can attack my PB in June, July and August.
"The World Championships in Osaka are quite late in the year. So too are the trials and that's great because it gives me so much more time. I don't have to rush anything."