The exercise you're avoiding might be what you need most

Last Tuesday, a client came in for her session at Beyond Fitness looking defeated.

“I’ve been avoiding anything too intense,” she explained. “I keep seeing posts on Instagram saying high-intensity exercise raises cortisol, and with everything else going on in my life right now, I can’t afford more stress. So I’ve just been walking.”

She looked exhausted. And stressed.

Here’s what nobody told her: the very thing she was avoiding might have been exactly what would help her handle stress better.

The Cortisol Conversation We Need to Have

Open Instagram and you’ll see it everywhere: “Don’t do HIIT—it spikes your cortisol!” “Chronic stress is killing you!” “Balance your hormones with this supplement!”

The message is clear and scary: cortisol is the enemy, and anything that raises it—especially intense exercise—should be avoided.

There’s just one problem with this narrative: it’s incomplete.

Think about cortisol like your phone’s flashlight. When you need to see in the dark, you turn it on. When you’re done, you turn it off. The flashlight isn’t bad—leaving it on for three weeks straight is bad.

Cortisol works the same way. Your body needs it to wake you up each morning (it peaks about 30 minutes after you open your eyes). It helps you focus during important meetings. It mobilizes energy when you’re exercising. It’s literally essential for life.

The problem isn’t cortisol. The problem is when stress becomes chronic—poor sleep, constant work pressure, never-ending family demands, undereating. That’s when your flashlight gets stuck in the “on” position.

What Actually Happens When You Exercise

Here’s where the cortisol story gets interesting, and where most social media posts stop reading the research.

Yes, all exercise raises cortisol. Your body perceives movement as a stressor (which it is), and cortisol helps fuel your workout, regulate your temperature, and keep your heart pumping blood to working muscles.

But not all exercise affects cortisol the same way.

Long, steady cardio—think hour-long jogs or extended cycling sessions—keeps your cortisol elevated for the entire duration. You’re in that “fight or flight” state for a prolonged period. Studies measuring cortisol in hair samples (which show cumulative exposure over time) have found that endurance athletes and long-distance runners actually have higher overall cortisol levels.

High-intensity interval training works differently.

During HIIT, cortisol does spike—even more dramatically than during steady cardio. But here’s the key: these spikes are short. A 20-minute HIIT session creates a brief, intense cortisol response, and then it’s done. Your body experiences the stress, adapts to it, and moves on.

And here’s what most people miss: your body is incredibly smart. When you regularly expose it to these short, intense bursts of stress, it adapts. It gets better at handling stress. Research shows that regular high-intensity training actually lowers your baseline cortisol levels over time.

It’s like practicing public speaking. The first time is terrifying. The tenth time is manageable. The hundredth time? You barely think about it. Your stress response has adapted.

The Adaptation That Changes Everything

Dr. Stacy Sims, an exercise physiologist who specializes in women’s health, puts it this way: regular moderate-intensity endurance exercise creates an adaptive response that increases circulating cortisol over time, whereas regular high-intensity interval training lowers baseline cortisol concentrations.

For women, this is especially important. Research demonstrates that women have a greater response of growth hormone and insulin to sprint training compared to men. This increased signalling helps build skeletal muscle, supports bone density, and improves metabolic health—all things that become increasingly critical as we age.

The short, intense stress of HIIT teaches your body to become resilient. Each sprint session is like a vaccine—a small, controlled dose of stress that makes you stronger for the real stresses life throws at you.

The Real Villain Isn’t Exercise

Here’s what actually disrupts cortisol regulation: chronic, unrelenting stress with no recovery.

Poor sleep night after night. Constant work anxiety without breaks. Chronic dieting and undereating. Overtraining without adequate rest. Perimenopause and menopause already shift the body into a more sympathetic (fight-or-flight) state due to hormonal changes.

In this context, yes, adding more stress without recovery is a problem. But the solution isn’t to make yourself less fit and less capable of handling stress. The solution is to address the chronic stressors and use short, intense exercise to build resilience.

Imagine you’re trying to improve your ability to carry groceries. The wellness influencer’s advice is: “Don’t lift heavy things—it stresses your muscles.” But that’s exactly how muscles get stronger. You need the right dose of stress, followed by recovery.

What This Means for You

If you’re avoiding high-intensity exercise because someone on the internet said it’s “bad for your cortisol,” you’re missing the full picture.

The real question isn’t “Does this raise cortisol?” Everything raises cortisol—waking up, drinking coffee, watching a tense movie, exercising. The real question is: “Is my body adapting and recovering, or am I in a state of chronic, unrelenting stress?”

If you’re sleeping well, eating enough, managing your overall life stress reasonably well, and allowing recovery time between workouts, then HIIT isn’t adding to your stress—it’s making you more resilient to stress.

Think about it this way: Would you rather be the person who can only handle walking because anything more intense “stresses you out”? Or would you rather be the person who can sprint up stairs, lift heavy things, and handle whatever physical demands life throws at you—because you’ve trained your body to be adaptable and strong?

The Path Forward

High-intensity training isn’t about punishing yourself or proving something. It’s about building a body that can handle life’s demands with energy to spare.

It’s about walking up three flights of stairs without getting winded. Playing with your kids or grandkids without needing a recovery day. Having the strength and stamina to do the activities you actually want to do.

The science is clear: when done properly, with adequate recovery, HIIT makes you stronger, more metabolically healthy, and better equipped to handle stress—both physical and mental.

The question isn’t whether intense exercise is “good” or “bad” for your cortisol. The question is: are you building the resilient, capable body you want to live in?

At Beyond Fitness, we work with you one-on-one (or in small groups of two) to design training programs that challenge you at the right intensity while respecting your body’s need for recovery. True high-intensity work requires personalized attention and coaching—someone who can monitor your effort, push you when you need it, and pull back when you don’t. If you’re ready to build real strength and resilience—or if you’re confused about what your body actually needs—we’re here to help you figure it out.