Cardio kills gains. 

At least, that's what many lifters believe. But is it really true when it comes to building strength? 

When the debate between HIIT (High-Intensity Interval Training) and LISS (Low-Intensity Steady State) cardio flares up, opinions fly, but one thing is clear: 

Not all cardio is created equal. 

Some say HIIT torches fat while keeping muscle intact, while others argue that LISS is the secret weapon for sustainable gains. 

But which one truly helps you build strength? 

This article breaks down the science, shattering myths and giving you the tools to make cardio work for your strength goals. 

Whether you’re after raw power, better endurance, or a lean, sculpted physique, the truth about HIIT vs. LISS might surprise you. 

Let’s dive in and find out which cardio approach can actually boost your strength—and which might be holding you back.

What Is HIIT?

High-Intensity Interval Training (HIIT) involves alternating between short bursts of all-out effort and brief recovery periods. 

Unlike traditional cardio, HIIT pushes you to your limit, skyrocketing your heart rate, and engaging your anaerobic energy systems. 

The intensity of these intervals creates a ripple effect on your metabolism, leading to an elevated calorie burn long after your workout ends—a phenomenon known as the afterburn effect, or Excess Post-Exercise Oxygen Consumption (EPOC). 

This metabolic boost can last for hours, making HIIT a time-efficient way to burn fat while preserving muscle mass.

How HIIT Boosts Muscle Activation

But what really sets HIIT apart when it comes to strength is its ability to activate fast-twitch muscle fibers.

These fibers are responsible for generating explosive power and short bursts of strength, which is why HIIT is favored by athletes aiming to improve both muscle definition and functional strength. 

The high intensity of HIIT sessions mimics the demands of heavy lifting, reinforcing the neuromuscular connections necessary for power and speed. 

The short bursts of high-intensity effort create metabolic stress, which research has shown to stimulate muscle growth and prevent muscle loss. In fact, studies suggest that participants who perform HIIT show notable improvements in muscle strength, particularly in the lower body. 

For those looking to break through strength plateaus or enhance their athletic performance, HIIT can be the thing that changes your workouts—building not just endurance, but the kind of muscle that translates directly into stronger lifts. [1] [2] [3] [4] [5] [6]

Limitations of Relying Solely on HIIT

Despite these benefits, HIIT has its limitations. 

Overdoing it can lead to recovery challenges and overtraining, especially if not balanced with proper rest. 

To fully develop strength, HIIT should be complemented with traditional resistance training, allowing you to target a broader range of muscle groups and prevent burnout.

What Is LISS?

Low-Intensity Steady-State (LISS) cardio is essentially the slow and steady counterpart to the explosive nature of HIIT. 

With LISS, the focus is on maintaining a consistent, moderate pace over a longer duration—think activities like brisk walking, cycling, or steady jogging. 

Unlike HIIT’s quick, intense bursts, LISS is all about sustained effort at a lower intensity, typically performed within your aerobic heart rate zone. 

This means your body primarily relies on oxygen to produce energy, making it a more relaxed, but still effective, cardiovascular workout.

One of LISS’s biggest advantages is its accessibility and minimal impact on the joints, making it suitable for people of all fitness levels. 

While LISS isn’t directly associated with building explosive strength, it serves an important role in a balanced training regimen. 

How LISS Supports Muscle Maintenance and Recovery

While LISS doesn't directly contribute to muscle growth like HIIT, it plays a significant role in maintaining strength. 

For strength-focused athletes, LISS shines as a recovery tool. 

It encourages blood flow to fatigued muscles without adding additional stress, helping to flush out waste products like lactic acid and deliver nutrients essential for repair. 

This enhanced circulation can lead to faster recovery between heavy lifting sessions, allowing you to train more frequently with less risk of burnout or injury.

It’s also beneficial for reducing muscle soreness and fatigue, allowing you to train harder, longer.

Moreover, LISS can be a valuable addition to a strength-building program by improving your aerobic base. 

A stronger aerobic foundation translates to better stamina during high-rep sets and reduced fatigue overall, indirectly supporting your strength gains. [7] [8] [9]

Drawbacks of LISS for Building Strength

LISS, on its own, isn’t designed to stimulate muscle growth. 

If you rely too heavily on LISS without incorporating strength training, it may actually contribute to muscle atrophy. 

However, when used in combination with a well-structured strength program, LISS helps maintain muscle mass while reducing body fat.

 Which Should You Choose? HIIT vs. LISS for Strength Gains

When deciding between HIIT and LISS for strength gains, it’s important to recognize that both have unique benefits that can complement your overall training strategy. 

Recent research shows that each form of cardio can play a distinct role in maximizing your results.

For example, a study by Stavrinou et al. (2016) found that HIIT not only enhances cardiovascular fitness but also boosts muscular endurance, particularly when combined with a strength training program. 

The explosive nature of HIIT activates fast-twitch muscle fibers, which are crucial for power and short bursts of strength. 

This makes HIIT an excellent choice for athletes who want to enhance both their conditioning and strength, all while spending less time on cardio. 

Additionally, the afterburn effect associated with HIIT can help maintain muscle mass by promoting fat loss without the risk of excessive muscle breakdown—a key consideration for anyone focused on strength.

On the other hand, LISS offers benefits that HIIT can’t provide, especially when it comes to preserving muscle during fat-loss phases. 

According to a study by Boutcher (2011), LISS can be particularly effective for maintaining lean mass while shedding body fat—a critical factor for bodybuilders or athletes during cutting cycles. 

The lower intensity of LISS allows for sustained fat oxidation without placing excessive strain on muscles or joints, reducing the risk of overtraining. 

Moreover, LISS serves as an active recovery tool, promoting better blood circulation, reducing muscle soreness, and speeding up recovery between heavy lifting sessions.

Ultimately, the choice between HIIT and LISS depends on your specific goals. 

If you’re focused on improving strength, incorporating HIIT into your routine can amplify power, conditioning, and muscle retention. 

However, if you’re in a fat-loss phase or need to prioritize recovery without sacrificing muscle, LISS is an ideal choice. 

The best strategy for most strength-focused athletes is to integrate both HIIT and LISS strategically within your program—leveraging the explosive benefits of HIIT on high-intensity days and using LISS for active recovery or during cutting phases. 

By understanding the strengths of each, you can tailor your cardio approach to enhance your overall strength and performance.

Real-World Applications: How to Use HIIT and LISS for Strength

Integrating cardio into a strength-focused training regimen can enhance your overall performance, support muscle growth, and improve recovery. Both High-Intensity Interval Training (HIIT) and Low-Intensity Steady State (LISS) cardio offer unique benefits that, when applied strategically, can complement your strength-building goals. Here's how different levels of lifters can effectively incorporate HIIT and LISS into their routines:

1. Beginners Focused on Strength

For those new to strength training, balancing cardio with resistance workouts is essential to build a solid foundation without hindering muscle gains.

• HIIT Integration:
• Frequency: 1-2 times per week.
• Duration: 15-20 minutes per session.
• Exercises: Simple movements like sprint intervals, cycling sprints, or bodyweight circuits.
• Benefits: Activates fast-twitch muscle fibers, boosts metabolism, and enhances cardiovascular health.
• LISS Integration:
• Frequency: 1-2 times per week or on rest days.
• Duration: 30-45 minutes per session.
• Activities: Brisk walking, light jogging, cycling, or swimming.
• Benefits: Promotes active recovery, reduces muscle soreness, and improves overall endurance without excessive strain.
• Sample Weekly Schedule:
• Monday: Strength Training + HIIT
• Tuesday: LISS
• Wednesday: Strength Training
• Thursday: LISS
• Friday: Strength Training + HIIT
• Saturday: Active Rest or Light LISS
• Sunday: Rest

2. Intermediate Lifters

As you advance, your body adapts to training stresses, allowing for more nuanced cardio integration to continue supporting strength gains.

• HIIT Integration:
• Frequency: 1-2 times per week.
• Duration: 20-25 minutes per session.
• Exercises: Incorporate more complex movements like kettlebell swings, battle ropes, or rowing sprints.
• Benefits: Further stimulates fast-twitch fibers and enhances metabolic conditioning.
• LISS Integration:
• Frequency: 2-3 times per week.
• Duration: 40-60 minutes per session.
• Activities: Incline walking, elliptical training, or steady-state cycling.
• Benefits: Improves aerobic capacity, aids in sustained energy levels during lifting, and maintains a lean physique.
• Sample Weekly Schedule:
• Monday: Strength Training + HIIT
• Tuesday: LISS
• Wednesday: Strength Training
• Thursday: LISS + Optional Core Work
• Friday: Strength Training + HIIT
• Saturday: LISS or Active Recovery (e.g., yoga)
• Sunday: Rest

3. Advanced Athletes (Powerlifters, Bodybuilders, etc.)

Advanced lifters often have specific goals such as maximizing strength, achieving peak muscle hypertrophy, or preparing for competitions. Cardio must be carefully integrated to support these objectives without compromising performance.

• HIIT Integration:
• Frequency: Once a week.
• Duration: 15-20 minutes per session.
• Exercises: Sport-specific or compound movements like sled pushes, plyometric jumps, or heavy sled pulls.
• Benefits: Maintains cardiovascular health and promotes fast-twitch fiber responsiveness without significant muscle depletion.
• LISS Integration:
• Frequency: 2-3 times per week, especially during cutting phases.
• Duration: 30-60 minutes per session.
• Activities: Swimming, cycling, or using the elliptical to minimize joint stress.
• Benefits: Facilitates fat loss while preserving muscle mass, enhances recovery by promoting nutrient delivery to muscles.
• Advanced Strategies:
• Periodization: Adjust HIIT and LISS based on training cycles (e.g., hypertrophy, strength, cutting).
• Recovery Protocols: Emphasize sleep, nutrition, and active recovery techniques like foam rolling.
• Nutrition: Ensure adequate protein intake and adjust caloric intake according to training phases.
• Sample Weekly Schedule:
• Monday: Heavy Strength Training (e.g., Squat Focus) + HIIT
• Tuesday: LISS (e.g., 45-minute cycling)
• Wednesday: Heavy Strength Training (e.g., Bench Press Focus)
• Thursday: LISS or Active Recovery (e.g., yoga)
• Friday: Heavy Strength Training (e.g., Deadlift Focus) + HIIT
• Saturday: LISS (e.g., steady-state swimming)
• Sunday: Rest or Light Mobility Work

4. Timing and Integration with Strength Workouts

The timing of cardio relative to strength training can impact performance and recovery:

• Separate Sessions: Performing cardio and strength training at different times of the day (e.g., cardio in the morning, strength in the evening) helps maintain high performance in both.
• Same Session: If combining, prioritize strength training first to ensure maximal energy and performance, followed by a brief cardio session.
• Post-Workout Cardio: Engaging in low-intensity cardio after strength training can aid in cooling down and enhancing recovery without significantly affecting muscle gains.

5. Practical Tips for Success

• Listen to Your Body: Prioritize rest and adjust cardio intensity based on how your body feels to prevent overtraining.
• Stay Consistent: Regularly incorporate both HIIT and LISS to benefit from their distinct advantages.
• Balanced Nutrition: Support your training with a diet rich in protein, complex carbohydrates, and healthy fats to fuel workouts and aid recovery.
• Hydration and Sleep: Maintain adequate hydration and ensure quality sleep to enhance performance and recovery.

Conclusion

Effectively incorporating HIIT and LISS into your strength-building program can optimize your results by enhancing muscle activation, improving recovery, and supporting overall fitness. Whether you're a beginner establishing your routine, an intermediate lifter seeking continued progress, or an advanced athlete aiming for peak performance, strategically blending HIIT and LISS can elevate your strength training outcomes and help you achieve your fitness aspirations.

References:

1. Tabata, I., Nishimura, K., et al. (1996). Effects of moderate-intensity endurance and high-intensity intermittent training on anaerobic capacity and VO2max. Medicine & Science in Sports & Exercise, 28(10), 1327-1330.
2. Zanuso, S., et al. (2010). The role of physical activity for the prevention and treatment of metabolic disorders. Diabetes, Metabolic Syndrome and Obesity: Targets and Therapy, 3, 173-183.
3. Schoenfeld, B. J., et al. (2014). The mechanisms of muscle hypertrophy and their application to resistance training. Journal of Strength and Conditioning Research, 28(3), 802-810.
4. Laursen, P. B., et al. (2005). Training for intense exercise performance: High-intensity or high-volume training? Scandinavian Journal of Medicine & Science in Sports, 15(2), 130-137.
5. Boutcher, S. H. (2011). High-intensity intermittent exercise and fat loss. Journal of Obesity, 2011.
6. Stavrinou, P. S., et al. (2016). The effects of high-intensity interval training on cardiovascular and muscular endurance. Journal of Sports Sciences, 34(4), 372-380.
7. Steele J, Plotkin D, Van Every D, Rosa A, Zambrano H, Mendelovits B, Carrasquillo-Mercado M, Grgic J, Schoenfeld BJ. Slow and Steady, or Hard and Fast? A Systematic Review and Meta-Analysis of Studies Comparing Body Composition Changes between Interval Training and Moderate Intensity Continuous Training. Sports (Basel). 2021 Nov 18;9(11):155. doi: 10.3390/sports9110155. PMID: 34822354; PMCID: PMC8619923.
8. Khanfir MA, Awicha HB, Masmoudi L, Hmadou FB, Dardouri W, Alardan S, Nouira S, Zouch M. Effects of Different Low-Intensity Exercise Types on Duration, Energy Expenditure and Perceived Exertion in Obese Individuals. Int J Environ Res Public Health. 2022 Apr 18;19(8):4893. doi: 10.3390/ijerph19084893. PMID: 35457760; PMCID: PMC9032643.
9. Lee D, Son JY, Ju HM, Won JH, Park SB, Yang WH. Effects of Individualized Low-Intensity Exercise and Its Duration on Recovery Ability in Adults. Healthcare (Basel). 2021 Mar 1;9(3):249. doi: 10.3390/healthcare9030249. PMID: 33804318; PMCID: PMC7999698.