I Swapped Cardio for HIIT Workouts for 30 Days: The Results Shocked Me

As someone who has been bodybuilding for almost two decades, the treadmill has been my go-to cardio choice. I won’t lie; some of these long, drawn-out sessions made me question the meaning of life. But despite the sweat, I wasn’t happy with my overall progress as I seemed to have hit a plateau.

This is when I decided to swap my steady-state cardio for high-intensity interval training (HIIT) for 30 days.

In this article, I break down the fat loss, cardiovascular fitness, and time efficiency results over this four-week period. I’ll also share tips on how you can adopt this challenge into your own routine. We have a lot to unpack, so sit tight and read on.

Understanding the Fundamentals

Before we get into the nitty-gritty of this 30-day HIIT challenge, let’s go over the basics of steady-state cardio and high-intensity interval training.

Steady-state cardio is what you usually see people doing in gyms. It involves maintaining a consistent, moderate intensity for an extended period. Think cycling or running on a treadmill for 10 to 30 minutes.

Steady-state cardio can help improve your cardiovascular health and endurance and burn calories. It is also a great way to build a solid aerobic base. Although this exercise form has several benefits, it can become monotonous and might not be the best choice for people on a tight schedule.

This is where high-intensity interval training (HIIT) shines.

HIIT involves alternating between short bursts of intense exercise with brief recovery periods. For example, you might sprint for 30 seconds and then follow it up with a minute of walking.

Science shows HIIT workouts can trigger excess post-exercise oxygen consumption (EPOC), which is also known as the “afterburn effect.” This phenomenon ensures that your body continues to burn calories at an elevated rate hours after finishing your workout. (1)

HIIT maximizes calorie expenditure in a very short time and can improve aerobic and anaerobic fitness and metabolism.

Besides all these benefits, I really like HIIT sessions because they are as psychologically challenging as they are physically demanding. They also induce a favorable hormonal response and increase muscle activation, helping you achieve your fitness objectives faster.

Finally, let’s be honest: Who wants to train for an hour if you can get the same results within 20 minutes?

My 30-Day HIIT Plan

Swapping cardio with HIIT for over four weeks is no joke, and you shouldn’t expect yourself to glide through this program if you don’t have a dedicated plan in place.

Since I am an advanced exerciser, I decided to train six days a week. In my opinion, this delivers enough stimulation to spark new growth without causing overexertion. Plus, I ensured enough work and rest time in each workout to promote muscle protein synthesis and fat oxidation.

Progressive Overload Over the Weeks

Progressive overload is the name of the game when it comes to making consistent gains, and it is no different during this 30-day HIIT challenge. Mastering the exercise form and establishing a baseline were my first objectives in the first week.

After I got comfortable, it would be all about increasing the training volume and intensity to get the best bang for my buck. I planned to step it up a notch by incorporating more challenging variations of the exercises.

I push myself to the limit in the last phase of each new training program, and this was the plan for this training program as well.

Sample 6-Day HIIT Routine

This is what my six-day HIIT routine looked like:

Day 1: Full-Body Blast

I always start a new workout with a five to 10-minute warm-up routine using exercises like arm circles, leg swings, or light cardio. This increases blood flow to the target muscles, improving training performance and limiting injury risk.

Similarly, I end a workout with a quick but effective cool down routine to lower my heart rate, flush out the metabolites from the muscle tissues, and promote recovery.

Exercise Name	Sets	Reps/Time	Rest Time
Burpees	3	10-12 reps	45 seconds
Kettlebell Swings	3	15-20 reps	45 seconds
Jump Squats	3	12-15 reps	45 seconds
Mountain Climbers	3	30 seconds work	30 seconds

Day 2: Sprint Intervals

As a personal trainer with over 17 years in the trenches, I can attest that variety is the most important thing when it comes to preventing strength and muscle plateaus. Our bodies are incredibly good at adapting to repetitive stimuli. Changing exercises, interval timings, and workout structures can keep your body guessing and force it to get bigger and stronger.

Exercise Name	Sets	Reps/Time	Rest Time
Sprint	6	30 seconds	60 seconds
Walking Rest	6	60 seconds	N/A
Light Jog	2	2 minutes	1 minute

Day 3: Upper Body Focus

I really enjoy the upper and lower body training split, so I incorporated the same protocol into my 30-day HIIT challenge. In this workout, I did as many push-ups as possible to burn out my chest, interior deltoids, and triceps.

Remember, you must keep your rest durations short. Resting for too long between exercises can lower the training intensity, leading to suboptimal results.

Exercise Name	Sets	Reps/Time	Rest Time
Push-Ups	3	As many as possible	45 seconds
Dumbbell Rows	3	12-15 reps	45 seconds
Plank Shoulder Taps	3	30 seconds work	30 seconds
Tricep Dips	3	10-12 reps	45 seconds

Day 4: Lower Body Domination

Go ahead and swap these exercises if you feel you get better muscle stimulation from different movements. The goal here isn’t to perform these workouts as it is but to maximize muscle fiber recruitment and subsequent adaptations.

Exercise Name	Sets	Reps/Time	Rest Time
Jumping Lunges	3	10-12 reps each leg	45 seconds
Goblet Squats	3	12-15 reps	45 seconds
Glute Bridges	3	15-20 reps	45 seconds
Calf Raises	3	20-25 reps	30 seconds

Day 5: Cardio and Core

If you are doing a HIIT workout, you should try conventional high-intensity exercises like high knees and jumping jacks. These movements are excellent for getting your heart rate up and improving your cardiovascular conditioning, resulting in improved work capacity and overall productivity.

Exercise Name	Sets	Reps/Time	Rest Time
High Knees	3	30 seconds work	30 seconds
Bicycle Crunches	3	30 seconds work	30 seconds
Russian Twists	3	30 seconds work	30 seconds
Jumping Jacks	3	30 seconds work	30 seconds

Day 6: Easy HIIT

I like to finish my weekly workouts with a rather simple session so that I cruise into the active recovery day. Research shows that staying active on your day off from training by indulging in a 20 to 30-minute outdoor walk or hiking session can improve your recovery compared to being idle. (2)

Exercise Name	Sets	Reps/Time	Rest Time
Light Jog	1	15 minutes	N/A
Stretching	1	15 minutes	N/A
Optional HIIT	1	20 minutes	As needed

Consider this just a blueprint and feel free to adapt this training routine according to your current fitness levels and training objectives.

Take an extra day off from training if you feel tired or exhausted. This is your body telling you that it needs more time to recover.

Tracking Progress: Metrics and Measurements

Whenever you are trying something new in your training, diet, or recovery, you shouldn’t leave anything to chance. I employed a multi-faceted tracking approach to ensure I was moving in the right direction. This is what it looked like:

Fitness Tracker

I am an absolute data geek, and I use a fitness tracker to monitor my heart rate during my workouts. This also allows me to track my calorie expenditure during the HIIT sessions, providing a clear picture of the energy burned.

I wear my smart watch throughout the day to track my steps, sleep quality, and resting heart rate. Any changes in these metrics offer valuable insights into my fitness progress.

Manual Measurements

As good as technology has gotten, you cannot outsource everything to computers. I took weekly body circumference measurements to track any changes in my body composition. I also maintained daily logs to record subjective observations, like energy levels and muscle soreness.

The Physical and Mental Transformation: Results and Observations

Now, let’s talk about the results because this is why we put ourselves through so much pain and discomfort.

Fat Loss: A Leaner Me Emerged

I kicked off this experiment at 185 pounds with 18% body fat. Frankly, I was happy with my physique aesthetics but wanted to push myself and achieve sharper cuts. By Day 30, the scale read 179 pounds, and my calipers pegged me at 15%.

These 6 pounds and three percentage points in a month are great results considering the effort I put in.

My clothes started fitting better as my T-shirts got a little looser around the midsection and a little more around the arms and shoulders, which is always a good thing.

Cardio Fitness: My Engine Revved Up

Before starting this challenge, my resting heart rate hovered around 68 beats per minute. However, it settled at 62 BPM when I finished — a sign my ticker grew stronger and more efficient. Now, climbing a flight of stairs does not leave me gasping.

I also noticed an improvement in my endurance as I shaved off 43 seconds from my 1-mile run time. Also, I believe I could have achieved better results if I had focused more on cardio.

Time Efficiency: I Reclaimed My Day

My previous cardio routine took anywhere between 45 minutes to an hour. On the other hand, this new HIIT program never lasted for more than 20 minutes. I slashed my workouts by over half while still achieving my training objectives. This is pure gold for busy folks who are juggling jobs and kids.

With those extra hours, I tackled client plans, wrote articles (like this one), and even enjoyed a coffee without rushing. HIIT didn’t just sculpt my body; it handed me back my schedule.

Muscle Tone and Strength: Definition Dialed In

Contrary to what most people think, HIIT workouts aren’t just for shedding belly fat. These sessions help improve my quad definition, V-taper, and ab conditioning. Most of the exercises in these workouts were compound movements, which contribute to improved functionality and overall productivity.

What’s better? My performance improved by a big margin. While I could only do 35 push-ups on Day 1 of this challenge, I crushed 47 reps on the final day.

I also experienced better energy levels throughout the day, and the mid-afternoon energy slumps were almost nonexistent.

Remember, when you are following a program like this four-week HIIT routine, you must learn to listen to your body. Adjust the training intensity based on how you are feeling. Stop the workout immediately and consult your doctor if you experience a sharp pain that doesn’t go away by the end of the day.

Conclusion

I had no idea what to expect from this 30-day HIIT challenge when I started, but it helped me lose weight and improve my muscle conditioning, cardiovascular fitness, and endurance, all while saving me a ton of time.

Like any other training program, you must be consistent, patient, and persistent to achieve your fitness objectives while following this 30-day HIIT program. Start small and gradually increase the training volume and intensity as you gain more experience.

If you have any questions about swapping cardio for HIIT workouts, post them in the comments below, and I’ll be happy to help!

References:

1. Greer BK, O’Brien J, Hornbuckle LM, Panton LB. EPOC Comparison Between Resistance Training and High-Intensity Interval Training in Aerobically Fit Women. Int J Exerc Sci. 2021 Aug 1;14(2):1027-1035. doi: 10.70252/ODIN6912. PMID: 34567357; PMCID: PMC8439678.
2. Ortiz RO Jr, Sinclair Elder AJ, Elder CL, Dawes JJ. A Systematic Review on the Effectiveness of Active Recovery Interventions on Athletic Performance of Professional-, Collegiate-, and Competitive-Level Adult Athletes. J Strength Cond Res. 2019 Aug;33(8):2275-2287. doi: 10.1519/JSC.0000000000002589. PMID: 29742750.

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