How to improve endurance over 40 – your precise 5-step formula

Even if 10k runs or 1k rows feature regularly in your fitness routine, your endurance – the ability to exercise at a moderate intensity for an extended period – will naturally begin to dip with age.

That’s largely because several systems in the body gradually lose capacity, even in otherwise healthy people. ‘Maximal heart rate falls as your cardiovascular system becomes less responsive and heart stroke volume – the amount of blood your heart pumps with each beat – can decrease slightly as your heart muscle stiffens,’ explains Sarah Campus, PT, running coach, and founder of LDN MUMS FITNESS.

‘Muscle mass and fast-twitch fibres are lost (known as sarcopenia), and mitochondrial efficiency (where energy stored in nutrients is turned into usable energy for your body) declines, as does the number of mitochondria,’ she continues, ‘and recovery processes slow due to hormonal and cellular changes.’

In simple terms: your engine still works, but it’s not quite as powerful as it once was.

The good news? Your ability to sustain steady efforts doesn’t disappear. The ceiling just lowers slightly.

You do, however, need to train consistently to minimise that drop. ‘If training is lowered, endurance can truly start to feel like it will also decline,’ says Campus.

1. Polarised aerobic training

This approach means keeping roughly 80-90% of your endurance training at a low-intensity, conversational pace. You should be able to speak in full sentences comfortably while exercising.

Ideally, you’re breathing through your nose and keeping your heart rate below your lactate threshold – the point at which lactate (a by-product of hard effort) begins building up faster than your body can clear it.

You then include one – occasionally two in a heavier week – carefully controlled higher-intensity sessions, explains Campus. These are efforts where you’re breathing heavily but can still speak in short sentences.

‘The low intensity preserves and builds mitochondrial density – more mitochondria means more energy produced – capillary networks, and fat-oxidation efficiency with minimal stress cost,’ she says.

‘Meanwhile, the single high-intensity session maintains cardiac output – the volume of blood your heart pumps per minute – and oxygen transport capacity without overwhelming recovery systems,’ Campus continues. ‘The key, though, is restraint, since most athletes go too hard too often.’

How to calculate your maximum heart rate:
207 - 0.7 x (age) = HR maximum

To monitor this during training, PT and wellness coach Rachael Sacerdoti recommends using a wearable device with a built-in heart rate monitor, such as a Fitbit or Garmin.

2. Structured threshold work in small, repeatable doses

‘For many athletes over 40, controlled intervals done at your lactate threshold – roughly a 7-8/10, comfortably hard effort, such as 2-3 sets of 10-15 minutes – with full recovery can improve endurance effectively,’ says Campus.

‘This approach can improve lactate clearance and your sustainable, medium-effort pace without the strain of very high intensities in your muscles or bones.’

Training at this level also increases capillary density, which improves oxygen delivery to muscles and enhances efficiency – allowing you to work longer before fatiguing.

3. Progressive volume

Consistency matters more than sporadic ‘perfect’ weeks.

‘Endurance responds strongly to total weekly time at low intensity. Increasing weekly aerobic volume gradually by small increments of 5-10% and holding that level consistently for months is more powerful than sporadic hard weeks,’ Campus explains.

For example:

Week 1: 60 minutes of running (3 x 20 minutes)
Week 2: 60 + 10% = 66 minutes (3 x 22 minutes)
Week 3: 66 + 10% = 72.6 minutes (3 x 24.2 minutes)

‘Your body adapts well to steady signals, whereas inconsistency speeds up the decline,’ she adds.

4. Strength training

After 40, this becomes non-negotiable.

‘Two brief full-body sessions per week, emphasising compound movements and posterior-chain strength (muscles on the back side of your body, like your glutes and hamstrings), help preserve muscle mass, tendon stiffness, and force production,’ Campus notes.

This improves movement economy – meaning you use less oxygen at a given pace – and directly supports endurance performance.

5. Recovery

At 40 and beyond, recovery is part of the training plan, not separate from it.

‘Sleep duration and quality, protein intake adequate for muscle repair, strategic rest days, and periodic de-load weeks allow higher quality aerobic adaptations,’ Campus says. ‘Many endurance plateaus in top athletes are not from insufficient work but from insufficient recovery to absorb the work.’

Overall, ageing may lower your absolute top-end output, but endurance at sub-maximal intensities remains highly trainable.

‘If you protect your aerobic base (how long you can move at a comfortable, low-to-moderate intensity) with disciplined low-intensity training, touch your top end just enough to maintain it, build strength, and respect recovery, endurance can remain impressively strong well past 40 even if peak numbers don’t look like they did at 25.’

Kate Cheng

Health and Fitness Writer

Kate puts together fitness content that covers functional and strength training, cardio, workout challenges, interviews and news. She's often doing gym laundry or listening to music.

Expert consulted:Sarah Campus

Women's PT

Sarah Campus is a highly qualified women's PT, Nutrition Coach, Running Coach, Distance Runner, mum of 3 and founder of LDN MUMS FITNESS.

She's the host of the Soho House Run Club in Chiswick and a STRAVA and TOMMY's marathon coach and ambassador. She specialises helping non-runners get into competitive distance running.

As a fitness and holistic wellness expert, Sarah regularly features on TV and in Magazines, offering tips and advice to keep the whole family healthy and active.