Carl Frampton has worked especially hard on improving his stamina ahead of Saturday's clash with Nonito Donaire.
The Northern Irishman faded in the later rounds of November's points win over Horacio Garcia, his first fight since losing the WBA world featherweight title on points to Leo Santa Cruz in January 2017, but Frampton (24-1, 14 KOs), 31, is looking to put that right when he fights Filipino Donaire (38-4, 24 KOs), 35, for the WBO interim title at Belfast's SSE Arena.
"It's [stamina] something I've been working on," Frampton told ESPN.
"I went out to Tenerife for altitude training, we were running up Mount Teide. It's a harsher environment and you have to work hard to create more red blood cells. You are supposedly fitter for it and I've been feeling good in sparring.
"Where as before in previous camps a lot of guess work has been involved with fitness, this time everything has been recorded and I'm getting into the red zones.
"It's a wee bit more carefully thought out and it's enable me to work more on getting into the best shape of my life.
"The last camp was a short camp -- seven or eight weeks -- but I'm used to 12 weeks training. I was getting used to a new trainer for my last fight and there was other stuff going on.
"We have brought in American sparring to replicate the style of Donaire and the signs are all good.
"I've been running up Cave Hill in Belfast when I've been back home a fair bit but I've never done anything at altitude before."
Frampton has been trained by Jamie Moore for the second consecutive fight after he replaced Shane McGuigan in September, and they have employed some different methods to prepare for four-weight world champion Donaire.
"I've been doing two altitude sessions a week in Manchester, where I go into a room which assimilates the altitude of anywhere in the world," Frampton said. "We've got it at 3500 metres above sea level, the same as the top of Mount Teide. It's amazing how it works.
"Apparently you lose the positive effect of altitude training after about a week when you come down from altitude, so that's why I've been doing it.
"I feel better than I have ever, recovering quicker and I don't feel I'm tiring as I once was, so it's definitely been very beneficial.
"We've been recording everything and I just feel good. I have had a good amount of sparring and I don't think I have had a bad session from start to finish of camp."