Why The Type Of Cardio You Do Matters More Than How Much You Do

Part 3 of the Strong & Fit For Life series

If there’s one instruction women have been given more consistently than any other in fitness, it’s this: do more cardio.

More steps. Longer runs. Another spin class. More time on the treadmill, the cross-trainer, the elliptical – that machine that looks like you’re cross-country skiing while watching morning television.

And most women have listened. They’ve put in the hours. They’ve shown up in lycra at 6am. They’ve finished a 45-minute session and driven home feeling like they’ve done the right thing. They’ve done everything right – by the playbook they were given.

And a lot of them are still frustrated. Still tired. Still quietly wondering if their body is just broken.

It’s not broken. But the playbook might be.

Because here’s what the research actually says: for women – and especially for women in perimenopause and beyond – the type of cardio you do matters far more than the amount. And the type most of us have been doing? Is probably not giving us the best outcomes (and may even be actively working against us).

The Part Nobody Told You About Cortisol

Here’s where the advice most of us grew up with starts to unravel.

Decades of “do more cardio” guidance wasn’t malicious. Nobody was lying to us. The research just wasn’t there – and when it finally arrived, it told a very different story.

Here’s the part that changes everything: long, moderate-intensity cardio raises cortisol. That’s not a design flaw – it’s a normal physiological response to sustained effort. But for women in perimenopause and beyond, chronically elevated cortisol doesn’t just feel lousy. It actively works against the things you’re trying to achieve.

Cortisol is your body’s primary stress hormone. In the right doses, it’s useful. Chronically elevated, it:

• Promotes fat storage – particularly around the abdomen (hello, that specific kind of frustration)
• Breaks down muscle tissue for fuel – the opposite of what women need for long-term health
• Disrupts sleep quality – which then raises cortisol further, in a cycle that’s as fun as it sounds
• Blunts the hormonal signals that drive strength adaptation
• Can worsen perimenopause symptoms including hot flushes, mood shifts and brain fog

Dr Stacy Sims – exercise physiologist and leading researcher in female-specific training – has been particularly direct on this point: for perimenopausal and postmenopausal women, chronic moderate-intensity cardio can actively worsen the hormonal environment the body is already managing. You’re adding training stress to a system that is already managing significant hormonal load.

The 45-minute moderate-intensity class that felt safe and sensible? For a woman in her 40s or 50s, done repeatedly, it may be doing more harm than good.

This is not comfortable information if you love those sessions. But it is accurate. And knowing it gives you choices.

So What Does Work?

The research on this is clear, consistent, and genuinely exciting – because the answer is not “more.” It’s smarter.

Short, high-intensity interval training – working at 80-90% of your maximum effort for brief intervals, with recovery periods between – produces dramatically better outcomes for women than equivalent or greater volumes of moderate-intensity cardio.

The specific benefits documented in research include:

• Improved cardiovascular fitness and VO2 max. One study showed a 12% average improvement in postmenopausal women after just 8 weeks of sprint interval training. For context, that’s a meaningful shift in your body’s capacity to use oxygen – the engine behind everything from climbing stairs to keeping up in a session.
• Improved body composition – specifically, greater fat loss alongside better lean mass retention compared to moderate-intensity training. Your body responds to the metabolic demand differently when the intensity is genuinely high.
• Better insulin sensitivity and blood sugar regulation – which matters enormously for energy, body composition and long-term metabolic health.
• Stronger mitochondrial function – the energy-producing capacity of your cells that naturally declines with age. High-intensity work is one of the most potent stimuli for mitochondrial biogenesis – essentially building more cellular engines.
• None of the chronic cortisol consequences of sustained moderate-intensity work – because the sessions are short. Hard, yes. But brief.

The key variables are intensity and brevity. You’re not doing this for an hour. You’re doing it for 20-30 minutes at an intensity that makes comfortable conversation genuinely impossible. Then you’re done. And your body spends the next several hours adapting to what just happened.

But What About Walking? I Thought Walking Was Good.

Walking is good. Walking is genuinely, legitimately good – for joint health, mental clarity, stress regulation, blood flow, vitamin D (if you’re doing it outside, in the sun, which in Australia is not exactly a stretch). Nobody is here to tell you to stop walking.

But walking operates at intensities too low to drive meaningful cardiovascular adaptation. It doesn’t challenge your heart and lungs sufficiently to improve VO2 max. It doesn’t produce the metabolic or mitochondrial stimulus your body needs. And it certainly doesn’t replace structured, progressive cardiovascular conditioning.

Think of it this way: walking is maintenance. It keeps the system ticking. High-intensity intervals are the stimulus that actually improves the system. You need both. They are not the same thing.

The same applies to recreational sport – netball, social tennis, golf, swimming laps at a comfortable pace. Movement. Good. Structured cardiovascular training stimulus? Not quite.