When it comes to improving your VO₂ max, there’s no shortage of conflicting advice. From high-intensity intervals to Zone 2 cardio and threshold training, we’re constantly being told which approach is best for building aerobic fitness.
While some swear by the efficiency of high-intensity training, others argue that slower, steadier sessions are the key to better endurance.
High- vs Low-Intensity Training: Which Is Best?
The reality is that both have their benefits. High-intensity intervals can improve VO₂ max in less time, but they also place greater demands on recovery, making them difficult to sustain every day. Lower-intensity cardio, on the other hand, allows you to accumulate more training volume with less fatigue.
According to new research published in the European Heart Journal, low-intensity training could be particularly important for your heart.
The 2026 study of 151 male endurance athletes found that time spent training at lower intensities was more strongly associated with heart size than time spent at higher intensities. This suggests easier cardio could play an important role in the cardiovascular adaptations that underpin VO₂ max.
How to Use Low-Intensity Cardio to Improve Your VO₂ Max
According to conditioning coach Joel Jamieson, the key isn’t choosing between high- and low-intensity cardio, but finding the right balance between the two.
‘Yes, hard intervals can get you results in less time in the gym. But the results come from recovering from that work,’ says Jamieson in an Instagram caption. ‘The more stress a session puts on your body, the more recovery it takes, which is why you can’t go hard every day without overtraining.’
High-intensity intervals can improve VO₂ max in relatively little time, but they also place greater stress on the body and require more recovery. Lower-intensity sessions, meanwhile, allow you to accrue more training volume without the same level of fatigue.
Jamieson recommends including one to two high-intensity sessions per week, with the majority of your remaining cardio performed at a lower intensity, such as Zone 2.
For most people, that could look like:
- 1-2 high-intensity sessions per week: Use intervals that challenge your cardiovascular system, with sufficient recovery between sessions.
- 2-4 low-intensity sessions per week: Aim for a comfortable, conversational pace that you can sustain for longer periods, whether you’re running, cycling, rowing or walking briskly.
- Prioritise recovery: Allow enough time between harder sessions, adjusting your training according to fatigue, sleep and overall recovery.
The aim is to build a stronger aerobic base while still including enough high-intensity work to move the needle. Over time, this combination could help improve endurance and cardiovascular fitness without the accumulated fatigue of repeatedly training at maximum intensity.
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Kate is a fitness writer for Men’s Health UK where she contributes regular workouts, training tips and nutrition guides. She has a post graduate diploma in Sports Performance Nutrition and before joining Men’s Health she was a nutritionist, fitness writer and personal trainer with over 5k hours coaching on the gym floor. Kate has a keen interest in volunteering for animal shelters and when she isn’t lifting weights in her garden, she can be found walking her rescue dog.
