HIIT

HIIT can affect blood glucose differently depending on when you train, and short all-out intervals can improve fitness.

• Morning versus evening: HIIT may raise blood glucose when done early in the day, while afternoon or evening HIIT may lower it and help move the body toward a fasted state—provided you don’t eat afterward. 1
• Glycogen and metabolism: HIIT and resistance training can direct glucose back into glycogen stores rather than toward fat storage, and can raise basal metabolic rate over time. 2
• Brief all-out work: A target of roughly five to six total minutes of all-out effort, accumulated in short bouts with adequate recovery, is discussed as a useful training dose; one example is 20 seconds hard and 40 seconds rest for six to eight rounds. Training about twice weekly is suggested, while frequent HIIT may create excess fatigue. 3
• Balance training intensities: For endurance development, combine HIIT with steady-state training and work across the intensity spectrum rather than relying on only one approach. 4