Possibly. The HIIT cardio does put a lot of strain on your system and therefore you may be quite fatigued as a result. Sleep is a great form of recovery - just ensure that you are not sleeping too much. Studies have shown that a 30 minute power nap after a workout can aid recovery and enhance growth hormone production. A 30 minute power nap during the day has also been shown to boost alertness, efficiency and focus.
Following a high intensity workout, ensure that your nutrition is geared toward recovery - some fast-acting carbohydrates and protein.
If the HIIT workouts are too full-on, you may be better off to reduce the intensity until your level of fitness improves to the point where HIIT is a more viable option.
