New dad Richie McCaw has found it challenging juggling baby duties with the gruelling demands of being a multisport athlete.

The former All Black captain will be competing in the Red Bull Defiance multisport event this weekend alongside teammates Bob McLachlan, Rob Nichol and Sarah Fairmaid. McCaw is also set to compete in the Coast to Coast next month with Nichol.

The 38-year-old said life with a five-week old is "different" but it's "all worth it".

"The broken sleep sort of changed things," McCaw said ahead of the event.

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"Normally when you are training hard, you want to get a good sleep. You get woken up a few times, which is something different to deal with.

"It's all cool. It's all worth it,"

McCaw and former Black Sticks star wife Gemma announced the birth of their first child, Charlotte Rose, early last month.