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Assess your improvements: how to use Hytro BFR wearables with your fitness tracker

Physiology trackers are now routinely inserted into widely used gadgets such as Apple Watches and FitBits. Discover how to use Hytro wearables with your fitness tracker.

Man adjusting the strap on his Hytro BFR Tee whilst wearing fitness trackers

Every heartbeat tells its own story. With each beat, blood is pumped around the body to carry oxygen and nutrients to organs and muscles. Put simply: our heart keeps us alive. In recent times, there’s been an explosion of interest in measuring heartbeats, boosted by the availability of wearable tech. Physiology trackers are now routinely inserted into widely used gadgets such as Apple Watches and FitBits, along with specialist equipment such as Garmin running watches and Polar monitors.

Heart rate is a core metric used in these gadgets. The fitter you are, the lower your resting heart rate. Most adults have a resting heart rate between 60-100 beats per minute, but athletes often have lower rates of 40-60bpm. However, at Hytro we prefer to use a different measurement to determine physical fitness: heart rate variability (HRV).

Heart Rate Variability

While heart rate measures beats per minute, HRV focuses on the difference in time between those beats. This isn’t a constant figure. For example, someone with a resting heart rate of 60bpm won’t always have one second between beats. Sometimes it might be slightly more, other times slightly less.

The higher your HRV, the fitter you are. That’s because HRV is a measure of your autonomic nervous system, which is influenced by two systems: sympathetic and parasympathetic. The sympathetic system increases your heart rate while the parasympathetic system slows it. When HRV is high, your body is responding well to both of these systems and the nervous system is balanced. If your environment suddenly changes then your body is well prepared to adapt to that change and primed to perform.

Just like heart rate, HRV isn’t fixed. While it increases as cardiovascular health improves, it can also decrease with stress and exercise fatigue. Knowing your HRV is therefore important so that you can determine when to train, what to train, and how much intensity to train with.

Measuring HRV

Most fitness trackers combine HRV with other metrics such as sleep, average heart rate and resting heart rate to give an overall score that determines your physiological state. Garmin, for example, incorporates HRV as part of its ‘body battery’ score, while Apple products benefit from their own HRV section. Some fitness trackers may alert you when your HRV is decreasing, though others require you to look through the data yourself. Scroll to the bottom of this article for detailed instructions on how to access these measurements.

How BFR impacts HRV

BFR is scientifically proven to improve aerobic fitness and cardiovascular health. The increased capillarization of muscle fibres that comes from BFR Training improves the body’s ability to take in and use oxygen in working muscles. Using BFR a few times a week also significantly enhances day-to-day recovery. That’s because BFR Training quite literally takes the stress out of your training schedule. Strapping in to Hytro wearables helps to flush out waste materials and inflammation from the body. Such physiological effect reduces stress and fatigue and ensures a better nervous system balance – along with a positive HRV.

How to use BFR with HRV

Before every training session it’s recommended to check your fitness tracker to see how prepared your body is for performance. If your tracker tells you that your HRV is high, or that you are lightly to moderately stressed, then use Hytro BFR wearables passively or actively. Doing so will support your recovery and improve your readiness to train.

However, if your tracker notes that you are highly stressed and recommends that you rest then BFR is a handy tool to ensure that you do not need to totally stop training. Using BFR passively will focus more on the recovery side of things while also giving further fitness benefits.

No matter which form of BFR Training you choose to use, over the course of your training cycle you will see gradual improvements in HRV that complement the physiological adaptations taking place in your body. Enhanced muscle size and strength, increased muscle protein synthesis, heightened muscular endurance and V02 max: while your heart rate may be varied, BFR will ensure that your results are anything but.

How to Access HRV Data


Launch the Health app on your device.

Tap on the Browse tab at the bottom of your screen.

Scroll to Heart and choose Heart Rate Variability

Assess HRV then choose how to train


Strain is Whoop’s measure of the stress you’re placing on your body and incorporates HRV. It gives the wearer a scale of 0-21.

Light Strain (0-9): Minimal stress is being placed on the body.

Moderate Strain (10-13): Moderate stress is being put on the body, helping to maintain fitness. At this level, use Hytro BFR actively or passively to accelerate recovery.

High Strain (14-17): Increased stress detected. Use Hytro BFR passively or actively to accelerate recovery.

Overreaching Strain (18-21): Training is at all out levels or you’ve experienced a day full of activities that has put significant stress on your body. It may be difficult to recover the following day. That’s why we’d recommend to use Hytro BFR passively to accelerate recovery.


Whoop’s daily recovery feature defines how prepared your body is for performance.

Green (>66%): Your body is well recovered and ready to perform. It can handle a strenuous day.

Yellow (33-66%): Your body is maintaining health. It may not need rest and can still handle a moderately strenuous day.

Red (<33%): Your body is working hard to recover. It could be due to a heavy training phase, illness or stress. Take time to rest and focus on active recovery.


Access HRV data through the Readiness and Trends tabs, located in the menu that can be accessed on the upper left-hand corner of the Home screen. Through Trends, a HRV quadrant is shown at the top of the screen. It shares your average HRV from the last seven days. Directly to the right of this is an arrow which indicates if your average HRV is increasing or decreasing.


Read about Passive BFR Training

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