The Science of High-Intensity Interval Training (HIIT) for Cardiovascular Health.

High-Intensity Interval Training (HIIT) has revolutionised the fitness world with its efficient, effective approach to improving cardiovascular health and overall fitness. This article delves into the history of HIIT, explores its rise to popularity, outlines considerations for beginners, explains the concept of Excess Post-Exercise Oxygen Consumption (EPOC), provides examples of three different cardio-targeted HIIT workouts, and highlights common pitfalls to avoid.

The History of HIIT

The roots of HIIT can be traced back to the early 20th century. The concept was first popularised by Finnish coach Lauri Pihkala in the 1920s, but it was the work of German coach Woldemar Gerschler in the 1930s that laid the foundation for modern HIIT. Gerschler, along with physiologist Hans Reindell, developed interval training protocols for athletes, emphasising short bursts of high-intensity exercise followed by rest periods.[1]

In the 1970s, Dr. Izumi Tabata’s research further propelled HIIT into the spotlight. Tabata’s studies demonstrated that short, intense bursts of exercise followed by brief recovery periods could yield significant improvements in both aerobic and anaerobic fitness. This 4-minute workout, known as the Tabata protocol, involves 20 seconds of all-out effort followed by 10 seconds of rest, repeated for eight cycles.[2]

The Rise to Popularity

HIIT gained mainstream attention in the late 20th and early 21st centuries as fitness enthusiasts sought efficient ways to maximise their workouts. The allure of achieving significant health benefits in a shorter amount of time compared to traditional steady-state cardio made HIIT appealing. Moreover, the flexibility of HIIT workouts, which can be tailored to fit various fitness levels and can be done with minimal equipment, contributed to its widespread adoption.

The digital age further fueled HIIT’s popularity, with fitness apps, online workout programs, and social media influencers promoting HIIT routines. Its effectiveness in burning calories, improving cardiovascular health, and enhancing metabolic function resonated with a broad audience, from busy professionals to elite athletes.[3]

Considerations for Beginners

While HIIT offers numerous benefits, beginners should approach it with caution to avoid injury and ensure long-term success. Here are key considerations:

1. Consult a Professional: Before starting a HIIT program, it’s advisable to consult with a healthcare provider or fitness professional, especially for those with pre-existing health conditions.
2. Proper Warm-Up and Cool-Down: Warm-up exercises prepare the body for intense activity and reduce the risk of injury. Similarly, a cool-down period helps in gradual recovery.
3. Start Slow: Beginners should start with lower intensity and shorter duration sessions, gradually increasing the intensity and volume as their fitness improves.
4. Form and Technique: Emphasise proper form and technique to prevent injuries. It’s better to perform exercises correctly at a lower intensity than to push too hard with poor form.
5. Listen to Your Body: Pay attention to how your body responds. Rest and recovery are crucial components of any fitness regimen.

Understanding EPOC

Excess Post-Exercise Oxygen Consumption (EPOC) refers to the increased rate of oxygen intake following strenuous activity. It’s commonly known as the “afterburn effect.” During intense exercise, the body consumes more oxygen than it does during rest, leading to an oxygen deficit. Post-exercise, the body continues to consume oxygen at an elevated rate to restore physiological and metabolic functions to pre-exercise levels.

EPOC is significant because it means the body continues to burn calories at a higher rate even after the workout has ended. This afterburn effect contributes to the efficiency of HIIT in improving cardiovascular health and aiding in weight management.[4]

Three HIIT Workouts for Cardiovascular Fitness

1. Classic Tabata Workout

Duration: 4 minutes

Structure: 8 cycles of 20 seconds of high-intensity exercise followed by 10 seconds of rest.

Exercises:

1. Sprinting in place
2. Burpees
3. High knees
4. Mountain climbers

Instructions:

• Warm-up with 5 minutes of light cardio (e.g., jogging, jumping jacks).
• Perform each exercise at maximum effort for 20 seconds.
• Rest for 10 seconds between each exercise.
• Repeat for a total of 4 minutes.
• Cool down with 5 minutes of stretching or light activity.

2. HIIT Circuit Workout

Duration: 20 minutes

Structure: 30 seconds of high-intensity exercise followed by 30 seconds of rest. Complete 4 rounds.

Exercises:

1. Jump rope
2. Squat jumps
3. Push-ups
4. Bicycle crunches
5. Plank jacks

Instructions:

• Warm-up with 5 minutes of dynamic stretching.
• Perform each exercise for 30 seconds at high intensity.
• Rest for 30 seconds between each exercise.
• Complete 4 rounds of the circuit.
• Cool down with 5 minutes of light stretching.

3. Cardio HIIT on the Treadmill

Duration: 30 minutes

Structure: Alternating between 1 minute of high-intensity running and 2 minutes of walking or jogging.

Instructions:

• Warm-up with 5 minutes of walking or light jogging.
• Run at a high intensity (e.g., 85-90% of maximum effort) for 1 minute.
• Walk or jog at a moderate pace for 2 minutes.
• Repeat for a total of 30 minutes.
• Cool down with 5 minutes of walking or light stretching.

Common Pitfalls to Avoid

While HIIT can be highly effective, avoiding common pitfalls is crucial for safety and effectiveness:

1. Skipping Warm-Ups and Cool-Downs: Skipping these can lead to injuries and hinder recovery. Always include proper warm-ups and cool-downs in your routine.
2. Overtraining: HIIT is intense and requires adequate recovery. Overtraining can lead to burnout, injuries, and decreased performance. Limit HIIT sessions to 2-3 times per week, allowing rest days in between.
3. Ignoring Form: Poor form can lead to injuries and reduce the effectiveness of the workout. Focus on performing exercises correctly, even if it means reducing intensity.
4. Neglecting Nutrition and Hydration: Proper nutrition and hydration are essential for optimal performance and recovery. Ensure you are fueling your body appropriately before and after workouts.
5. Inconsistent Effort: The effectiveness of HIIT relies on maintaining high intensity during work intervals. Ensure you are pushing yourself during these periods while also allowing for adequate rest.

Other Cardiovascular Training Styles to Consider

In addition to High-Intensity Interval Training (HIIT), two other effective styles of cardiovascular training are steady-state cardio and circuit training. 

Steady-state cardio, also known as continuous or low-intensity steady-state (LISS) cardio, involves maintaining a consistent, moderate level of exertion over an extended period. Activities such as jogging, cycling, or swimming at a steady pace for 30 to 60 minutes are common examples. This type of training is excellent for building endurance, burning fat, and improving cardiovascular health without placing excessive stress on the body. 

Circuit training, on the other hand, combines aerobic exercises with resistance training in a sequential manner. Participants move quickly from one exercise to the next, incorporating both cardio and strength elements, such as jumping jacks followed by push-ups and then squats. Circuit training provides a comprehensive workout, boosting cardiovascular fitness, muscular endurance, and overall strength, making it a versatile option for those looking to maximise their training efficiency.

Conclusion

High-Intensity Interval Training (HIIT) is a powerful tool for improving cardiovascular health, offering an efficient and effective workout option that fits into busy lifestyles. By understanding its history, following considerations for beginners, grasping the concept of EPOC, and implementing well-structured workouts, individuals can reap the benefits of HIIT while avoiding common pitfalls. Whether you’re a novice or a seasoned fitness enthusiast, HIIT can elevate your fitness routine and enhance your cardiovascular health.

Please Note: The information provided in this article are the opinions and professional experience of the author and not all activities are recommended for the beginner or participants with underlying health conditions. Before following any advice or starting any fitness, health and wellbeing journey please consult with an Allied Health Professional and / or General Practitioner.

REFERENCES

1. Old Interval Training
2. Tabata Training
3. Evidence-Based Effects of High-Intensity Interval Training on Exercise Capacity and Health
4. Exercise After-Burn

• Bio

Steve Irwin

Steve has spent the last 19 years in the Australian Fitness Industry as a Group Fitness Instructor, 1-1 Coach, State Manager, Business Owner and is currently an Educator for the Australian Institute of Fitness. A lifelong fitness enthusiast he started his working life in the Military which guided him into the fitness industry where his passion for helping others on their health and fitness journey has been realised. Steve believes that for anyone thinking about getting fit or healthy they should “just get started” as “doing something is better than doing nothing”.