If you have spent any time researching fitness, you have come across these two terms. Steady state cardio and HIIT. They sit on opposite ends of the intensity spectrum, they produce different effects in the body, and depending on who you ask, one is always better than the other.
The truth is more nuanced than that, and more useful. Understanding what each method actually does, where each one excels, and how they work together is what separates people who plateau from people who keep progressing.
At Shred415, we have built our entire format around combining both. Here is what the science says, and what it means for you in class.
What Is Steady State Cardio?
Steady state cardio, sometimes called LISS (low-intensity steady state), is any form of cardiovascular exercise performed at a consistent pace and intensity for an extended period. Think of a 40-minute jog at a comfortable, maintainable effort. Your heart rate settles into a moderate zone, your breathing is elevated but controlled, and your body draws on oxygen to fuel the work.
According to Healthline, LISS cardio is most commonly associated with running, cycling, swimming, and brisk walking, typically performed for 45 to 60 minutes at low to moderate intensity. It is well-suited to all fitness levels and particularly effective for building aerobic endurance.
Steady state cardio is aerobic, meaning your body uses oxygen continuously to sustain the effort. That is why you can keep going for a long time. The demand is manageable enough that your energy supply can keep pace.
What Is HIIT?
HIIT stands for high-intensity interval training. It is a method of exercise that alternates short bursts of hard effort with recovery periods. The key word is interval. You push hard, recover, then push again.
HIIT is anaerobic during the push phases, meaning your body is working faster than oxygen can be delivered. That oxygen debt is repaid during recovery, and it is this cycle of demand and recovery that makes HIIT so effective.
The American Heart Association notes that HIIT can deliver cardiovascular and metabolic benefits in significantly less time than moderate-intensity continuous training. Their 2023 scientific statement on resistance and aerobic exercise highlights that combination training, where aerobic intervals meet strength work, produces outcomes that neither modality achieves alone.
At Shred415, every class is built on an interval structure. The treadmill segments are your HIIT engine. The strength work on the decks adds a layer that amplifies results even further.
What Burns More Fat: HIIT or Steady State?
This is the question most people are searching for, and the honest answer is that both burn fat, but they do it differently and the full picture matters.
During steady state cardio, your body burns a higher percentage of calories from fat in real time. Because the intensity is lower, fat is the preferred fuel source. A longer steady state session can accumulate significant calorie burn during the workout itself.
HIIT burns a greater proportion of carbohydrates during the session, but it triggers something called EPOC, or excess post-exercise oxygen consumption. According to Cleveland Clinic, EPOC is the elevated calorie burn that continues after your workout ends, as your body works to restore oxygen levels, repair tissue, and rebalance hormones. HIIT creates a significantly larger EPOC effect than steady state cardio.
Research published in the National Academy of Sports Medicine (NASM) found that HIIT combined with resistance training may be more advantageous than steady state cardio for long-term fat loss, because it supports the development of lean muscle mass, which increases resting metabolic rate.
A 2024 meta-analysis published by ScienceDirect found that HIIT and continuous aerobic training produce similar fat loss results when total energy expenditure is equal. The real-world advantage of HIIT is efficiency: you can achieve comparable outcomes in less time.
Both methods work. The best one is the one you can do consistently. And the most powerful approach combines both in a single structured program.
HIIT vs Steady State: At a Glance
| HIIT | Steady State Cardio | |
| Intensity | High to maximum effort | Low to moderate, consistent |
| Duration | 20 to 45 minutes | 40 to 60 minutes or more |
| Primary fuel | Carbohydrates (with fat burned post-session) | Fat (during session) |
| Afterburn (EPOC) | High, up to 24 hours post-workout | Low to moderate |
| Cardiovascular gains | Strong, improves VO2 max rapidly | Strong, builds aerobic base |
| Recovery needed | More recovery between sessions | Lower recovery demand |
| Best for | Time efficiency, metabolic conditioning | Endurance, active recovery |
Can You Do Cardio and Strength Training Together?
Yes, and the research strongly supports it.
A 2024 study published in the European Heart Journal followed 400 individuals over 35 with high blood pressure. Those who combined 30 minutes of aerobic exercise with 30 minutes of strength training three times a week saw significant reductions in blood pressure, LDL cholesterol, and body fat. The results matched those from 60 minutes of cardio alone, but with the added benefit of strength gains.
A study published in the British Journal of Sports Medicine found that people who completed both cardio and strength work in their training had a lower risk of death compared to those who did only cardio. The combination also strengthens joints, improves insulin sensitivity, and preserves muscle mass as you age.
The long-standing concern that doing cardio and weights together would compromise either modality has not held up under modern research. Structured correctly, the two enhance each other.
What Is the Best Way to Combine Treadmill and Weights?
Structure matters more than people realise. Random combinations of cardio and strength work do not produce the same results as intentional programming.
The most important principles are:
- Alternate between cardiovascular and strength demands rather than doing all cardio first and all lifting second. This keeps intensity high throughout and prevents either system from fully fatiguing before the other begins.
- Use the recovery periods between intense intervals actively. Light movement between blocks keeps your heart rate from dropping too far and maintains the metabolic effect of the session.
- Keep strength work compound and multi-joint. Exercises that use multiple muscle groups simultaneously keep heart rate elevated during the floor segments and build functional strength that carries into everyday life.
- Match session frequency to recovery capacity. Combining cardio and strength in a single session is demanding. Three to four well-structured sessions per week is typically more effective than five or six poorly recovered ones.
This is exactly the architecture of a Shred415 class. Four 15-minute intervals alternating between the treadmill and the decks, with every transition designed to keep the session working across both systems simultaneously. For more on how that structure drives results, see our blog on What Is Hybrid Training // And Is Shred415 a Hybrid Workout?.
Can You Do Cardio and Strength Training on the Same Day?
Yes. And for most people with a normal schedule, the same-session approach is more practical and equally effective than separating them across different days.
The American Heart Association recommends adults complete at least 150 minutes of moderate-intensity aerobic activity and two days of muscle-strengthening activity per week. A Shred415 class completed three to four times per week satisfies both requirements within each session, making compliance significantly easier for anyone with a busy schedule.
There is an important nuance around order. If your primary goal is maximal strength, doing heavy lifting before intense cardio preserves more performance in the weights. If your goal is cardiovascular improvement or general fitness, the order is less critical. At Shred415, the alternating interval format sidesteps this question entirely by interweaving both throughout the session. For a detailed look at how often to attend, see How Often Should You Train to See Real Results with Shred415.
Does Shred415 Use HIIT, Steady State, or Both?
Both, within every single class.
The treadmill segments use an interval format that moves you from moderate Zone 2 and Zone 3 effort up through Zone 4 and Zone 5 push intervals. That progression builds your aerobic base and your anaerobic threshold in the same session.
The strength segments on the decks add resistance work that increases muscle mass, boosts resting metabolism, and creates additional EPOC over and above what the treadmill work alone would produce.
The combination is why Shred415 members do not have to choose between two types of training or figure out how to program them together. It is already built in. You can read more about the specific science behind our interval structure in HIIT vs SIT // What Everyone Should Know About Smarter Interval Training at Shred415.
How to Know Which Approach Is Right for You
The answer depends on what you are training for and how much time you have.
If you are building a long-distance endurance base, dedicated steady state sessions outside of Shred415 classes are a strong complement. Running or cycling at an easy pace on recovery days builds your aerobic engine without adding significant fatigue.
If your goal is fat loss, general fitness, or time efficiency, HIIT-based training with strength work is the most effective use of your training hours. You get the metabolic effect of intervals and the body composition benefit of resistance in one session.
If you are returning from injury or new to exercise, steady state cardio offers a lower-impact entry point that builds fitness without the joint stress or recovery demands of high-intensity work.
For a look at how Shred415 supports all fitness levels, including those starting out, visit Are Shred415 Workouts Suitable for Beginners?.
See the infographic below for a side-by-side comparison of HIIT and steady state cardio, and how both map to the Shred415 class format.
Disclaimer: This blog is intended for informational purposes only and does not constitute medical advice. Before beginning any new exercise program or strenuous physical activity, please consult your doctor or a qualified healthcare professional, particularly if you have any existing health conditions, injuries, or concerns.
Ready to Experience Both in One Class?
Every Shred415 class puts HIIT and strength training together in a format that does the programming for you. You show up, push at your level, and the structure handles the rest.
Find your nearest studio at shred415.com/locations.
