Heart Rate Variability (HRV): A Practical Guide for the Everyday Athlete - Part 1

Heart rate variability – or HRV – has exploded in popularity thanks to wearables and smart watches. In simple terms it’s just a way of looking at how well your body copes with stress and recovers.

But with all the buzz, it can feel confusing. Is a higher number always “better”? Why does it drop after wine, a hard workout… or for females the week before your period?

For recreational athletes trying to balance training with life, HRV can be a powerful tool — if you understand what it’s telling you.

What Actually Is HRV?

Even if your heart rate is 60 beats per minute, your heart isn’t beating perfectly once every second. One beat might be 0.95 seconds after the last, another 1.05 seconds. HRV measures these tiny differences.

These variations are controlled by your autonomic nervous system (ANS):

• Sympathetic system: “fight or flight”, speeds the heart up

• Parasympathetic system: “rest and digest”, slows the heart down via the vagus nerve

  
  

In general:

• Higher HRV = more adaptability, better recovery, more parasympathetic tone

• Lower HRV = more stress, fatigue, illness, under-recovery or hormonal effects

But remember: HRV is individual due to the number of different factors art play. Your “good” might be someone else’s “low” so its more useful to look at context and trends rather than specific figures.

Smartwatches, HRV and accuracy - what are they really measuring?

Clinical HRV is taken from an ECG, but wearables use photoplethysmography (PPG), a light sensor that estimates the time between beats.

Most devices calculate a parasympathetic-focused metric called RMSSD and then convert it into their own “readiness” score.

Importantly this means:

• You can’t compare your number to someone else’s

• Different brands show different values due to having different algorithms 

• Short-term fluctuations are normal

Why HRV Readings Aren’t Always Accurate

Your HRV can swing wildly because of:

• Poor sensor contact (strap too loose, movement, sweat)

• Dark tattoos or darker skin tones reducing optical accuracy

• Alcohol, caffeine or dehydration

• Stress or poor sleep

Even in research settings, wrist sensors can be up to 20% off for heart rate, and HRV is even more sensitive to small errors. That said some devices (good quality chest straps or finger based wearables like Oura) tend t o be more accurate because they sit closer to arterial blood-flow or record ECG-like signals. 

What Is a “Good” HRV?

This is where social media gets a bit unhelpful as there is no universal healthy number.

Population studies show adult RMSSD (the short term readings your smart watch takes) can range anywhere from under 20 ms to over 70 ms. Highly trained endurance athletes may sit higher.

This range is huge, therefore a more helpful approach is to ask “is my HRV normal for me and heading in the right direction over weeks and months"?

A More Practical Way to Interpret Your Baseline

✔ Establish your personal baseline

Track morning or overnight HRV for 2–4 weeks.

✔ Look for trends, not single readings

• Consistently low for YOU? → Check recovery, stress, sleep

• Sudden drop + high resting HR? → Possible illness or overload

• High and stable? → You’re adapting well

Factors That Increase HRV

Fitness & Training

• Regular aerobic exercise

• Well-programmed strength training

• Good balance between hard sessions and recovery

Lifestyle

• High-quality sleep

• Stress-management (breathing, mindfulness, yoga)

• Adequate fuelling — especially carbs

• Hydration

• Healthy blood pressure, glucose and body composition

Nutrition

• Eating enough overall

• Reducing ultra-processed, high-sugar or alcohol-heavy evenings

Factors That Lower HRV

• Overtraining or sudden spikes in training load

• Poor sleep or broken nights

• Emotional stress & burnout

• Under-fuelling (RED-S — especially common in female athletes)

• Alcohol — even 1–2 drinks can tank overnight HRV

• Illness, infection or inflammation

• Ageing

• Hormonal changes, especially in women (menstrual cycle & menopause)

• Chronic conditions: hypertension, diabetes, heart disease

What can I do to improve HRV?

Focus on the behaviours that reliably support both health and HRV rather than chasing a number alone.

1. Training and fitness

• Build an aerobic base.

  • 2–5 sessions per week of easy–moderate cardio (RPE 5–7/10 where you can talk) can improve HRV and resting HR over time.

• Include some intensity – but not constantly.

  • 1–3 harder sessions per week (intervals, tempo, hills, HYROX-style workouts) are usually plenty for recreational athletes.

• Strength train 2–3 times per week.

  • This supports blood pressure, glucose control and muscular strength, which indirectly benefit HRV.

• Avoid “grey zone” every day.

  • Back-to-back hard days plus life stress is where HRV can flag that recovery isn’t keeping up.

Use your HRV as one piece of feedback: if it’s consistently low for you and you feel run-down, it’s often sensible to reduce intensity, focus on easy movement and sleep, and see if it rebounds.

2. Nutrition

• Eat enough, especially around training.

  Chronic under-fuelling (low energy availability) is linked with hormonal disruption, menstrual disturbance and impaired autonomic function in female athletes. That often shows up as low HRV and high resting HR.

• Balanced plate – lean protein, whole-grains, fruit/veg, healthy fats.

• Carbohydrates are not the enemy for active people – they’re a key fuel for high-intensity training and recovery.

• Limit heavy evening alcohol – many people see a clear drop in overnight HRV after drinking.

• Stay hydrated – dehydration adds to cardiovascular strain and can reduce HRV.

3. Lifestyle & Stress

• Sleep first.

  Aim for 7–9 hours where possible, with a consistent bedtime/wake time.

• Breathing and relaxation techniques.

  Slow, diaphragmatic breathing around 5–6 breaths per minute (inhale for ~4–5 seconds, exhale for ~5–6) is often used in HRV biofeedback and has been shown to reduce anxiety and improve HRV in a range of studies.

• Mind–body practices.

  Yoga, meditation and similar practices generally show small improvements in HRV and stress markers over time.

• Pace life stress where you can.

  During very stressful periods (family illness, big work deadlines), consider slightly reducing training intensity and using HRV as a check-in rather than striving for PBs.

When You Should See Your GP?

HRV can be an early indicator of stress or illness, but it’s NOT a diagnostic tool.

Consult your GP if you experience:

• Palpitations or irregular heartbeat

• Dizziness or fainting

• Unexplained breathlessness

• Chest pain

• A persistent major drop in HRV & rising resting HR, especially with fatigue or swelling

• You’re in peri-menopause/menopause and concerned about cardiovascular symptoms

If you’re a female recreational athelete then please read my 2nd HRV related blog where I deep dive into how hormonal fluctuations across menstrual cycles and menopause affect HRV.