Heart rate variability (HRV) is one of the most powerful — and most misunderstood — metrics in sports science. It's not just a number on your wearable. It's your nervous system speaking to you. And once you learn to listen, your training will never be the same.
At SOMA, we've analysed HRV data from over 10,000 users across 14 months of daily tracking. What we found challenges many widely held beliefs about when, how hard, and how often you should train.
What is HRV, exactly?
Your heart doesn't beat at perfectly regular intervals. Even at rest, the time between each heartbeat varies slightly — and that variation is your HRV. A higher HRV generally indicates a well-recovered, adaptable nervous system. A low HRV suggests stress, fatigue, or illness.
HRV is measured in milliseconds (ms) and reflects the balance between your sympathetic nervous system (fight-or-flight) and your parasympathetic nervous system (rest-and-digest). When recovery is optimal, the two systems are in equilibrium — and your HRV climbs.
Why HRV matters more than how you feel
Athletes are notoriously bad at self-assessing their readiness. Studies show that subjective fatigue perception is only weakly correlated with actual physiological readiness. In our dataset, 38% of SOMA users who reported feeling "good" had HRV scores indicating significant suppression — meaning they were training hard on days when their bodies were not ready.
The consequences? Slower adaptation, elevated injury risk, and — if sustained — overtraining syndrome.
HRV gives you an objective window into your body's true state. It doesn't lie. It doesn't have bad days emotionally. It simply reflects biology.
How to read your HRV data
Rather than chasing a single "ideal" number, the key is understanding your personal baseline. HRV is highly individual — a score of 55ms might be excellent for one person and poor for another.
SOMA establishes your rolling 60-day HRV baseline during your first two months of tracking. From there, each morning reading is compared to your personal norm:
The SOMA HRV Protocol: What 10,000 users taught us
After analysing training outcomes correlated with HRV compliance, three findings stood out:
1. Consistency of measurement matters more than the number itself. Users who measured HRV at the same time each morning (ideally upon waking, before getting out of bed) showed 31% more predictive accuracy than those who measured sporadically.
2. Weekly trends are more valuable than daily readings. A single low-HRV morning is noise. Three consecutive low-HRV mornings is a signal worth acting on.
3. HRV-guided periodisation outperforms fixed-plan periodisation. Users who adjusted their training intensity based on SOMA's daily HRV recommendations showed a 22% greater improvement in VO2max after 12 weeks compared to a matched group following a static plan.
How SOMA uses HRV in your coaching brief
Every morning, SOMA's AI synthesises your overnight HRV reading with your sleep data, training load history, and upcoming schedule to generate a personalised coaching brief. This brief tells you:
You don't need to become an HRV expert. SOMA does the interpretation for you.
Common HRV myths — debunked
Myth: Higher HRV is always better. Reality: HRV should be higher than your personal baseline, not higher than someone else's. Absolute values are largely meaningless without context.
Myth: One bad HRV day means you're sick. Reality: HRV fluctuates naturally with alcohol, poor sleep, travel, stress, and even a large meal. Context is everything.
Myth: HRV only matters for endurance athletes. Reality: Strength, power, and team sport athletes benefit equally from HRV monitoring. Recovery quality affects hypertrophy signalling, neuromuscular readiness, and reaction time equally.
Getting started with HRV-based training
You need three things: a compatible wearable (Apple Watch, Garmin, WHOOP, Oura Ring, Polar, or a Bluetooth HRM), the SOMA app, and 60 days of consistent data collection.
The first two months are your calibration period. Don't try to interpret individual readings yet — just collect data. By day 60, SOMA will have built a precise model of your physiology and will begin generating HRV-informed coaching recommendations.
The result? Training that works with your body, not against it.