This is the failsafe formula for how to improve your fitness fast, according to a top trainer

Advice from the pros.

How to improve your fitness fast: A woman stretching her legs
(Image credit: Getty Images)

If you're wondering how to improve your fitness fast, know this - most effective training plans and respectable personal trainers will advise that, to see results, you need to be working out consistently and stick at it for at least three months. That said, there's been some unexpected news this week: some research does show that you might be able to alter your fitness levels much sooner than initially thought.

One study from the Journal of Physiology found that six sessions of HIIT performed over two weeks improved exercise performance, while another NASA study showed that just eight sessions were enough to improve markers of fitness. 

On a smaller scale, every time you move your body, you're working towards better fitness. That's because workouts tear muscles (which, in turn, rebuild stronger) and test your heart and lungs, too. That said, if you're Googling how to improve your fitness fast, you're likely looking for tips to help you achieve the big kind of gains that you can both feel and see. 

"The time it takes to improve overall fitness varies depending on so many factors, including how fit you are to begin with, which element of your fitness you're looking to improve, how frequent your training, is, how intense your workouts are and what your genetic predispositions are," says Lucy Cowan, master trainer at Third Space London. It goes without saying, too, that habits that you build slowly but surely are more likely to stick, plus avoid the risk of overtraining or injury.

However, there are some guidelines you can work from if you are keen to improve your fitness fast. Of course, the best way to improve your fitness is to find a workout you enjoy, whether that's strength training, running, home workouts or Pilates, and stick with it regularly to see yourself progress over time. Exercise is meant to be a fun tool you use to respect and support your body, after all. But if you've left training for a race, competition or event to the last minute, want to give yourself a challenge, or simply prove to yourself that exercise won't be as much of a slog as you think it is, we have tips. Don't miss our guides to the best workout split, how to improve your physical fitness at home, and how to get motivated to workout, while you're here.

Keen to know how to improve your fitness first? Your guide

How fast can beginners get fit? 

You're in luck if you're new to exercise: the newer you are to a sport, the easier it is to improve. In a phenomenon known as "newbie gains," people who are novices to exercise can gain over five times as much strength as regular exercisers over 21 weeks, according to a study from the European Journal of Applied Physiology.

That's because your body can only improve when it's challenged by something it's never done before - a much easier feat for someone new to exercise than someone who's been training for years. 

And more good news: if you were once fitter and stronger than you are now, it won't take as long to rebuild your fitness as it did when you started from scratch. In a 2019 study, men and women trained for 10 weeks and then took a 20-week break. After returning to training for five weeks, they'd already rebuilt more strength and muscle than they did in the initial training phase thanks to something called muscle memory.

How long does it take to improve cardio fitness? 

So you want to improve your running, cycling or other cardio fitness - how long should you expect to see results? "Improvements in cardiovascular fitness can be noticeable within a few weeks to a couple of months of consistent aerobic exercise," says Cowan. "Initially, you may notice improvements in your endurance and stamina, followed by more significant improvements in heart health, lung capacity and overall cardiovascular function over time."

To continue seeing progress, it's essential to gradually increase the intensity, duration, and frequency of your cardio workouts, she adds. "Bodies are great at getting used to and adapting to the levels of cardio we put them through and often the improvements we see plateau and level after time. If someone is brand new to cardio, then improvements in fitness will be noticed relatively quickly, yet if someone is well-conditioned to cardio already, making improvements will be much harder and take more time." Got that?


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How long does it take to improve strength? 

If it's strength and muscle gains you want to see, Cowan says it can be "relatively quick, often within a few weeks of consistent resistance training."

How so? Well, initially you may experience neuromuscular adaptations, where your body becomes more efficient at recruiting muscle fibres to perform exercises, she shares. "As you continue to train, you'll start to see increases in muscle mass, strength, and muscular endurance," she continues. Do note, though: "Significant muscle growth typically takes longer, ranging from a few months to a year or more, depending on factors such as training intensity, nutrition and genetics. Consistency, progressive overload, and proper recovery are essential for continued strength gains." 

How to improve fitness fast: 6 simple tips

Just can't wait that long to see fitness improvements? "To improve general, non-specific fitness quickly, a combination of high-intensity interval training (HIIT), strength training and proper nutrition can be highly effective," says Cowan. She recommends: 

1. Incorporate some high intensity cardio

Cowan's first tip is to incorporate HIIT workouts into your routine two to three times per week. These involve short bursts of intense exercise followed by brief recovery periods. HIIT workouts are efficient and effective for improving cardiovascular fitness, burning calories and boosting metabolism. HIIT sessions can be shorter in duration (15-30 minutes) but are highly effective for improving cardiovascular fitness. On non-HIIT days, consider longer, steady-state cardio sessions (30-60 minutes) to build endurance.

2. Incorporate weekly strength training

Next up: the personal trainer advises aiming for two to three strength training sessions per week, focusing on compound exercises that target multiple muscle groups simultaneously. This could include exercises like squats, deadlifts, lunges, bench presses, rows, and overhead presses. Use challenging weights and aim for eight to 12 repetitions per set to stimulate muscle growth and increase strength.


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3. Incorporate progressive overload

This one's important. Continuously challenge your body by gradually increasing the intensity, volume or load of your workouts over time. This could involve adding more weight, increasing the number of repetitions or sets, or reducing rest periods between exercises. If your goal is to improve fitness fast, you will likely want to increase intensity every week, if not at every workout.

4. Focus on your fuelling, too

Next up: yep, nutrition is important if you're looking to improve your fitness. Why? Well, because fuelling your body with nutrient-dense foods will support your workouts and, in turn, recovery.

Try this: Prioritise lean protein sources, complex carbohydrates, healthy fats, and plenty of fruits and vegetables. It's also important to make sure you're consuming enough calories to support your activity level and goals and stay well hydrated.

5. Prioritise rest and recovery

By this, we mean allowing your body adequate time to rest and recover between workouts to prevent overtraining and injury. Aim for one to two days of rest per week and prioritise quality sleep to support muscle repair and growth. It might feel like a waste of a day if you want to get fit fast but it's actually one of the best things you can do for your output.


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5. And finally, stay consistent

Last but by no means least, the easiest way to improve your fitness is to stay consistent with your training and fuelling your body well, too. Consistency is key for making progress and building fitness over time.

Bottom line? "While this schedule provides a framework for improving fitness quickly, it’s essential to listen to your body and adjust your workout frequency and intensity based on your individual needs and goals. Overtraining can lead to burnout, injury, and stalled progress, so prioritise rest, recovery, and proper nutrition to support your fitness journey," adds Cowan. 

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Chloe Gray
Contributing Health Writer

Chloe Gray is a freelance journalist who writes and talks about health, fitness, and wellbeing through a feminist lens. She was part of the launch team for Stylist magazine's fitness brand, Strong Women, and has written for i news, Women's Health, Red magazine, Good Housekeeping, Refinery29, and more. She's all about building mental and physical strength, eating delicious food that fuels you well, and making the fitness industry more accessible and enjoyable. She's also a qualified fitness trainer and research nerd, so you can be sure everything you read is backed by proper science.