High-intensity interval training can be a great way to boost fitness – but only if it’s been scheduled well. PT Sarah Campus reveals how to build a smart HIIT plan
Words: Sarah Campus | Images: Shutterstock
High-intensity interval training (HIIT) has earned itself a reputation as one of the most effective ways to burn calories and build fitness. Scroll through social media and you’ll find endless promises that 20 minutes of burpees, squat jumps and mountain climbers will transform your body and leave you fitter than ever. But here’s the problem: most people doing these workouts aren’t actually doing HIIT.
As a personal trainer, women’s wellness expert, run coach, marathon runner and hybrid athlete, I see this situation all the time. Women tell me they’re doing HIIT five or six times a week, yet they’re constantly tired, their progress has stalled, they’re struggling to recover and they don’t feel any fitter.
The reality is they’re stuck in what I call the ‘middle ground’ – working too hard to recover properly, but not hard enough to experience the true benefits of high-intensity interval training. HIIT isn’t just another workout style you throw into your weekly routine whenever you fancy. Done properly, it’s an incredibly effective training tool. Done too often or at the wrong intensity, it can backfire. If you want better fitness, improved body composition and more energy, it’s time to rethink how you’re using HIIT.
Real HIIT feels hard
The clue is in the name: high intensity. A true HIIT session requires you to work at close to your maximum effort during the work intervals. This means that you should struggle to hold a conversation, your breathing should be heavy, and the effort should feel genuinely challenging.
The problem is that most people unknowingly train at around 70-80 per cent effort. It feels tough enough to leave them red and sweaty, but not hard enough to trigger the adaptations HIIT is designed to produce. If you’re chatting comfortably throughout your intervals, it’s probably not HIIT. If you could happily continue for another hour, it’s definitely not HIIT. Quality matters far more than quantity.
More doesn’t mean better
One of the biggest myths in fitness is that if two HIIT sessions are good, six must be even better. Unfortunately, your body doesn’t work like that.
HIIT places significant stress on your muscles, nervous system and cardiovascular system. Those adaptations happen during recovery, not during the workout itself. When you perform high-intensity sessions day after day, fatigue accumulates faster than your body can recover. The result? Plateaued fitness, reduced performance, persistent soreness, poor sleep, low energy, increased injury risk and loss of motivation. Instead of getting fitter, you’re simply getting more tired.
Avoid the ‘grey zone’
Another pattern I see regularly is women who believe they’re doing HIIT every day but are actually training in what’s known as the ‘grey zone’. Every workout feels fairly hard, every workout leaves them sweaty but, most importantly, every workout sits somewhere between moderate and high intensity. The problem here is that nothing is easy enough to support recovery, and nothing is hard enough to maximize performance gains. They are constantly accumulating fatigue without giving their body a strong enough reason to adapt. This is why so many women feel like they’re working incredibly hard but seeing very little progress. Sometimes, doing less actually allows your body to achieve more.
Strength training is the foundation
If your goals include fat loss, muscle definition, healthy ageing, longevity or improving body composition, strength training should form the backbone
of your program. Think of HIIT as a supplement, not the main event. Resistance training builds lean muscle, supports bone health, improves metabolism and develops long-term strength. HIIT is a good way to improve cardiovascular fitness and add a conditioning stimulus, but it shouldn’t replace lifting weights. A balanced week might look like: three strength sessions, one or two HIIT sessions, daily walking, one or two recovery or mobility sessions. This combination allows every type of training to complement the others, rather than compete with them.
Recovery is essential
One of the biggest mistakes people make is believing rest days are unproductive. In reality, recovery is where your body repairs muscle tissue, replenishes energy stores and becomes fitter. If every day is a high-intensity day, recovery never truly happens.
This doesn’t mean sitting still. Active recovery can include walking, gentle cycling, swimming, mobility work, yoga or stretching. These lower-intensity sessions improve circulation, reduce stiffness and help you feel ready for your next hard workout. The goal isn’t to do less overall – it’s to match the right intensity to the right day.
Schedule HIIT with purpose
Treat HIIT as your performance session, not your default workout. For most recreational exercisers, one or two quality HIIT sessions each week are enough to improve cardiovascular fitness and conditioning. Leave at least 48 hours between sessions, particularly if you’re also strength training or running.
On HIIT days, give yourself permission to work properly hard. Then earn the recovery your body needs in order to improve. You’ll gain far more from two outstanding sessions than five average ones.
Train smarter, not harder
Fitness isn’t about seeing how exhausted you can become. It’s about applying the right stimulus at the right time. Every session should have a purpose. Some days are for building strength, some are for improving endurance, some are for pushing intensity, and others are for recovering so your body can adapt.
When every workout becomes HIIT, none of them truly are. Your training becomes a collection of hard sessions rather than a structured programme – and that’s when progress slows.
HIIT is an effective training method, but only when it’s used correctly. Instead of asking yourself, ‘How many HIIT workouts can I squeeze into my week?’, ask a better question: ‘How can I make my HIIT sessions good enough that I don’t need more of them?’.
Train hard when it’s time to train hard. Recover properly when it’s time to recover. Build strength as your foundation, and use HIIT strategically to complement it. The goal isn’t to finish every workout feeling exhausted, it’s to become fitter, stronger and healthier over time.
Sarah Campus is a highly qualified women’s PT and nutrition coach. She is a mum-of-three and founder of LDN MUMS FITNESS. Sarah regularly features on TV and in the media, offering tips and advice to keep the whole family healthy and active. Visit sarahcampus.com and instagram.com/sarahcampus, or listen to her new podcast Showing Up Stronger (available to stream on Apple, YouTube and Spotify).
