We’ve all heard that we should be “more active,” but what does that actually mean? How much exercise is enough to improve your health, and how hard should you be working?

The good news is that the recommendations from the World Health Organization (WHO) are clear, achievable, and can easily be met through regular fitness classes.

The WHO Guidelines

The World Health Organization recommends that adults aged 18–64 should aim for either:

• 150–300 minutes of moderate-intensity aerobic activity each week, or
• 75–150 minutes of vigorous-intensity aerobic activity each week, or
• An equivalent combination of moderate and vigorous activity.

In addition, adults should perform muscle-strengthening activities involving all major muscle groups on at least two days per week.

These guidelines aren’t just about fitness—they’re designed to reduce the risk of heart disease, stroke, type 2 diabetes, certain cancers, depression, and premature death.

What Does That Look Like in Fitness Classes?

Most group fitness classes last between 45 and 60 minutes, making it surprisingly simple to reach the recommended targets.

If you attend moderate-intensity classes

Examples include:

• Low-impact aerobics
• Dance fitness
• Circuit classes at a steady pace
• Brisk walking groups

You would need approximately:

• 3 x 50-minute classes per week to meet the minimum recommendation.
• 5–6 classes per week to reach the upper end of the recommended range.

If you attend higher-intensity classes

Examples include:

• HIIT
• Spin
• Bootcamp
• High-energy circuits

You would need approximately:

• 2 x 40–45-minute classes per week to achieve the minimum recommendation.
• 3–4 classes per week to comfortably exceed it.

Many people enjoy combining different class styles throughout the week, which is exactly what the WHO recommends.

For example:

• Monday – Strength
• Tuesdays – Circuits
• Wednesday – HIIT

This provides cardiovascular exercise, strength training, and recovery while keeping workouts varied and enjoyable.

How Do You Know If You’re Working Hard Enough?

One of the simplest ways is to monitor your heart rate.

Heart rate provides an objective measure of how hard your cardiovascular system is working.

Step 1: Estimate Your Maximum Heart Rate

A simple estimate is:

220 − your age

For example:

A 40-year-old would have an estimated maximum heart rate of:

220 − 40 = 180 beats per minute (bpm)

Moderate Intensity

Aim to exercise at 64–76% of your maximum heart rate.

For our 40-year-old:

• 64% = 115 bpm
• 76% = 137 bpm

So their target moderate training zone would be approximately 115–137 bpm.

Vigorous Intensity

Aim for 77–93% of your maximum heart rate.

For the same person:

• 77% = 139 bpm
• 93% = 167 bpm

Their vigorous training zone would therefore be approximately 139–167 bpm.

A More Personalised Method: The Karvonen Formula

Not everyone’s resting heart rate is the same. Someone who exercises regularly may have a resting heart rate in the 50s, while another person may naturally sit in the 70s or 80s.

The Karvonen Method takes this into account.

The calculation is:

Target Heart Rate = ((Maximum Heart Rate − Resting Heart Rate) × Intensity) + Resting Heart Rate

For example:

A 40-year-old with a resting heart rate of 65 bpm has:

• Maximum heart rate = 180 bpm
• Heart rate reserve = 180 − 65 = 115 bpm

To work at 70% intensity:

(115 × 0.70) + 65 = 146 bpm

This personalised method gives a more accurate training zone because it reflects your individual fitness level.

Don’t Have a Heart Rate Monitor?

That’s absolutely fine.

You can use the Talk Test.

Moderate intensity

• Your breathing is faster.
• You can still hold a conversation.
• Singing would be difficult.

Vigorous intensity

• Breathing is deep and rapid.
• Speaking more than a few words at a time becomes difficult.
• You definitely wouldn’t want to sing!

For many people, this is surprisingly accurate.

The Bottom Line

The World Health Organization’s recommendations aren’t about becoming an athlete—they’re about giving your body enough movement to stay healthy, strong, and independent throughout life.

For many people, that could be as simple as attending two or three higher-intensity classes each week, or three to five moderate-intensity sessions, alongside at least two strength-based workouts.

Whether you’re tracking your heart rate with a smartwatch, using the Talk Test, or simply enjoying moving more, every session is an investment in your long-term health.

References

Science Insights (n.d.) How to measure physical activity: Methods and tools. Available at: https://scienceinsights.org/how-to-measure-physical-activity-methods-and-tools/ (Accessed: 1 July 2026).

World Health Organization (2020) WHO guidelines on physical activity and sedentary behaviour. Geneva: World Health Organization. Available at: https://www.who.int/publications/i/item/9789240015128 (Accessed: 1 July 2026).