Defoe has looked a different player to a year ago when he recovered from an injury and lost his form.
The 28-year-old turned to Ian Wright and the Arsenal legend recommended fitness guru Tiberius Darau in France.
"Jermain was low last year when he was not scoring," said Redknapp. "Ian Wright is good for him. He is very friendly with him, he's bubbly and spends a bit of time with him.
"Wrighty recommended Tiberius Darau, a guy who is about 70. He was with Arsenal for years. He spent a large part of the summer working with him three sessions a day - very early in the morning, afternoon and evening - and came back stronger and fitter."