Yes, you can do both weight training and HIIT on the same day. Most individuals who do so perform two separate training sessions on the same day to allow for recovery between sessions.

When you do a tough workout, particularly when you’re working on building strength, your body needs down time to rest and rebuild. In fact a tough workout, while burning off the hormones of stress, creates other stresses. It can cause the immune system to be down for as long as 72 hours.

Any fitness addict will tell you that combining cardio and strength training is the best way to increase your fat burning potential. Think of strength training and cardio as a classic duo like peanut butter and jelly. While they’re good individually, they’re even better together.

Turning a Strength Workout into a HIIT Workout

1. Shorten rest periods. When you workout for HIIT the goal is to get your heart rate seriously elevated.
2. Add in more compound movements. For your HIIT-strength days, focus on compound movements that work entire large muscle groups.
3. Add cardio.
4. Increase the weights.

How to Combine HIIT and Strength Training Routines

1. Take shorter rests. The goal of HIIT is to elevate your heart rate quickly.
2. Add cardio between sets. If shortening your rests isn’t doing it for you, go a step further and turn those rests into cardio sets.
3. Use movement patterns.
4. Do weighted movements.

Ultimately, this means you are going to lift significantly weaker. If you keep that type of training up, your muscular goals will be harder to achieve – especially since building muscle and burning fat goes hand in hand, you want your weight training to come first.

On the other hand, High-Intensity Interval Training or HIIT workouts focuses less on progressing to heavier weight lifting and bigger muscles and more on performing high-intensity exercises in large volume reps quickly in order to raise a person’s heart rate, cycling between high intensity and resting periods.