Both high-intensity interval training (HIIT) and steady, easy cardio raise your aerobic fitness. A meta-analysis of 28 trials found HIIT edged ahead on VO2max, but not by a lot.[1]
Two ways to train
HIIT means short bursts at an effort of 8 to 10 out of 10, with rest between. Low-intensity steady state (LISS) means easier effort, around 2 to 4 out of 10, for 30 to 60 minutes, such as brisk walking or easy cycling. Exercise physiologists quoted by Prevention use a simple talk test: during HIIT you cannot speak in full sentences, and during LISS you can hold a conversation.
What the meta-analysis found
Researchers pooled 28 controlled trials with 723 healthy adults aged 18 to 45, with a mean age of about 25. The outcome was VO2max, the maximum rate at which your body can use oxygen, a standard measure of aerobic fitness.[1]
- Endurance training raised VO2max by about 4.9 mL/kg/min versus no exercise.
- HIIT raised it by about 5.5 mL/kg/min versus no exercise.
- Head to head, HIIT came out about 1.2 mL/kg/min ahead of endurance training, which the authors classed as a possibly small beneficial effect.
The authors concluded that both approaches produced large improvements, with greater gains after HIIT.[1]
Limits to keep in mind
- The adults were healthy and young to middle-aged, so the results may not carry over to people over 50 or with health conditions.
- VO2max is one outcome. The analysis does not cover injury rates, how long people stick with each style, or weight and blood sugar changes.
- HIIT demands more recovery. The experts in the Prevention piece say LISS can be done most days.
How to use this
- Pick the one you will repeat. A small fitness edge does not beat a habit that sticks.
- Mix both. One or two HIIT days with easy cardio on other days gives you the intensity and the recovery.
- Start easier if you are new. Build with LISS first, then add intervals.
- Check in with your clinician first if you have heart disease, chest discomfort, or unusual breathlessness, or if you have been inactive.
For a trial of what one HIIT day a week can do, see Once-Weekly HIIT and Fat Loss: What a 315-Adult Trial Found.
The takeaway
HIIT gives a slightly bigger VO2max bump in healthy younger adults, and easy steady cardio gives you a base you can build on nearly every day. Use both, and let your schedule and recovery decide the ratio.
References
↑︎ Milanović Z, Sporiš G, Weston M. Effectiveness of High-Intensity Interval Training (HIT) and Continuous Endurance Training for VO2max Improvements: A Systematic Review and Meta-Analysis of Controlled Trials. Sports Med. 2015. DOI: https://doi.org/10.1007/s40279-015-0365-0
Kurt Greiner
Kurt is a digital strategist and IT professional blending emerging technology with practical application to help businesses and individuals streamline their digital presence. His current work focuses on the intersection of intentional living and technological resilience, exploring how individuals can leverage modern tools to navigate the second half of life with purpose.
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