INTRODUCTION

Heart rate training is one of the most effective ways to monitor and improve athletic performance. By tracking how hard the heart is working during exercise, coaches and athletes can ensure every workout has a purpose — whether that is building endurance, improving fitness, or pushing peak performance. SquadHR and TeamHR bring these insights to life in real time, displaying every athlete's effort on your iPhone, iPad, or the big screen. This guide explains the key concepts behind heart rate training and how our apps put them to work.


WHAT IS HEART RATE TRAINING?

Heart rate training is the method of tracking your heart rate to optimize your workout. Heart rate (HR) is the number of times your heart beats per minute (bpm) as it pumps blood through your body. HR shares a direct relationship with exercise intensity — the more intense the exercise, the higher the heart rate. This makes HR one of the best indicators of how hard your body is working during a workout.

As aerobic fitness develops, your muscles become more efficient at using oxygen, and your heart rate decreases at any given level of effort. In general, a drop in exercise heart rate over time is a good indicator of improving fitness.

HR and physical characteristics such as body weight, age, and gender are also used to estimate energy expenditure, exercise intensity, and aerobic fitness.


TRACKING THE WHOLE TEAM IN REAL TIME

SquadHR and TeamHR let you monitor every athlete at once, removing the guesswork from training. Rather than checking individuals one at a time, you see the entire group's effort on a single screen, making it easy to spot who is working hard, who is coasting, and who may need a rest.

SquadHR is built for fitness classes and indoor training, connecting up to 14 Bluetooth heart rate sensors in real time, or 24 in near real time on a single iPhone.

TeamHR is built for team sports, tracking heart rate and steps for up to 14 sensors in real time, or 28 in near real time. With additional iPhones running the free TeamHub app — each acting as a signal repeater to extend Bluetooth range — you can track up to 50 players in real time across large outdoor fields.

Display the action on a TV, projector, or monitor so your whole squad can see their effort live, turning heart rate into a powerful motivational tool.


THE METRICS YOU CAN TRACK

Both apps go well beyond a simple heart rate reading. Each player tile can display a range of performance metrics, giving you a complete picture of effort and progress:

Heart rate — current, average, high, low, and percentage of maximum
Energy expenditure — active and afterburn energy (Cal/kJ)
Training score — cumulative training load for the session
Time-in-zone — how long each athlete spends in each intensity zone
Cardio recovery — how quickly heart rate returns to normal after effort
Heart rate variability (HRV) — a measure of fitness and recovery readiness

TeamHR adds motion tracking using the Polar H10's built-in accelerometer, calculating running pace, cadence, and distance — without the cost and complexity of traditional GPS systems.


HEART RATE TRAINING ZONES

Heart rate zones are ranges of heart rate that correspond to different exercise intensities and training benefits. There are five zones, each defined as a percentage of your maximum heart rate (MHR) and shown in its own colour. Both apps display each athlete's live zone, so you can guide training intensity at a glance.

Zone 1 — Very Light (Blue, 50–60% MHR)
Used for warm-ups, cool-downs, and active recovery. Helps promote blood flow and prepares the body for more intense work.

Zone 2 — Light (Green, 60–70% MHR)
The endurance zone. Builds aerobic base, improves fat utilisation, and can be sustained for long periods. An essential part of any training program.

Zone 3 — Moderate (Yellow, 70–80% MHR)
Improves cardiovascular efficiency and overall conditioning. Moderate effort — you can speak a few words but not full sentences.

Zone 4 — Hard (Orange, 80–90% MHR)
Improves performance and aerobic capacity. Breathing is laboured and sustained effort is difficult. Used for interval training and threshold sessions.

Zone 5 — Maximum (Red, 90–100% MHR)
Used for short, maximum effort bursts such as sprints or HIIT. Improves speed and power. Cannot be sustained for long periods.

An effective training program includes sessions across multiple zones, with the majority of time spent in the lower zones to build a solid aerobic base.


MAXIMUM HEART RATE

Maximum heart rate (MHR) is the highest number of beats per minute your heart can pump under maximum effort. It is used to calculate your heart rate training zones.

MHR can be estimated using the formula: 220 minus age. However, this formula is not perfectly accurate, particularly for people who have been fit for many years or for older individuals. A more accurate method is to warm up properly and perform a series of high-intensity intervals to maximum effort, such as hill climbs or inclined treadmill running, while wearing a heart rate sensor.

Both SquadHR and TeamHR can automatically update each athlete's maximum heart rate whenever a new peak is reached during a session, keeping training zones accurate as fitness and effort levels change over time.

For safety reasons, people aged over 35, those who are overweight, in poor physical condition, have been sedentary for several years, or have a family history of heart disease, should have their max heart rate clinically measured by a cardiologist or exercise physiologist.


ACTIVE ENERGY

Active energy or energy expenditure (Cal/kJ) is estimated using an equation developed in a study published in the Journal of Sports Sciences in 2005 and funded by Polar Electro Oy. In the study, participants completed multiple steady-state exercises at varying intensities. The researchers demonstrated that energy expenditure can be estimated with good accuracy using heart rate, age, weight, and gender.


AFTERBURN ENERGY

The afterburn effect, also known as Excess Post-exercise Oxygen Consumption (EPOC), occurs when your body continues to burn calories after exercise to replenish oxygen stores during recovery.

Afterburn energy is estimated using an equation derived from a 2011 study published in Medicine and Science in Sports and Exercise. In the study, ten men performed a vigorous 45-minute workout on a stationary bike. The results showed an additional 37% post-exercise energy expenditure to the net energy expended during the session, persisting for up to 14 hours.

Based on these results, the app calculates 37% of the net energy expended above a vigorous training threshold of 70% maximum heart rate to estimate a conservative value for afterburn.


TRAINING SCORE

Training Score (or Training IMPulse, TRIMP) is a measure of cumulative exercise intensity from a single workout, used to quantify training load. The app uses Edwards' summated heart rate zones method.

Training score is calculated as the cumulated duration (in minutes) in each of five heart rate zones, multiplied by a zone coefficient:

90–100% MHR = 5 points per minute
80–90% MHR = 4 points per minute
70–80% MHR = 3 points per minute
60–70% MHR = 2 points per minute
50–60% MHR = 1 point per minute
Below 50% = 0 points

For example, a simple 10-minute workout: 5 minutes in Zone 2 (5 × 2 = 10 points) and 5 minutes in Zone 4 (5 × 4 = 20 points), giving a total training score of 30 points.

The score is then mapped as a percentage of the maximum possible score for that session duration. The maximum score for our 10-minute workout would be 10 minutes entirely in Zone 5 (10 × 5 = 50 points). So a score of 30 out of a possible 50 equals 60% of the maximum, classified as Hard intensity.

Higher training scores are achieved with longer duration and/or more vigorous workouts.


HEART RATE VARIABILITY

Heart rate variability (HRV) is the difference in time between consecutive heartbeats, measured in milliseconds. The app calculates HRV using the standard deviation (SDNN) of beat-to-beat measurements captured by the heart rate sensor.

HRV is useful for evaluating fitness and determining exercise readiness. In general, higher HRV is a sign of better fitness. HRV is a highly personal metric that varies between individuals, and is affected by age, gender, fitness level, lifestyle, environment, and genetics.

HRV can only be calculated with HRV-enabled heart rate sensors, such as the Polar H9 or H10.


CARDIO RECOVERY

Cardio recovery refers to how quickly your heart rate returns to normal after exercise. The fitter you are, the faster your heart rate falls during the first minute after peak exertion.

According to the National Academy of Sports Medicine (NASM), the average recovery rate is a drop of 15 to 25 beats per minute. General guidelines are:

Excellent: more than 25 beats
Good: 18–25 beats
Fair: 12–17 beats
Poor: fewer than 12 beats

A recovery drop of fewer than 12 beats has been linked to an increased risk of cardiac events. Recovery is influenced by age, fitness level, hydration, medications such as beta-blockers, and overall health. Tracking recovery over time can help monitor improvements in cardiovascular fitness.


RECOVERY DROP

Recovery drop is measured by subtracting your heart rate one minute after exercise from your peak heart rate during the session. For example, if your peak heart rate is 160 bpm and it drops to 135 bpm after one minute of rest, your recovery drop is 25 beats.


TURNING DATA INTO INSIGHTS

Tracking is only the beginning. SquadHR and TeamHR help you make sense of the numbers and act on them, with TeamHR offering additional cloud and AI-powered tools:

Workout summaries — send each athlete an automatic email summary of their session, branded with your own logo to reinforce your club or business.

Progress tracking — monitor trends over weeks and months to see fitness improvements, manage training load, and reduce the risk of overtraining.

AI performance summaries — TeamHR uses Claude AI to generate coaching summaries covering team intensity, recovery, and workload, with actionable recommendations after each session.

Cloud dashboards — TeamHR lets you view and share live sessions, player results, 30-day team performance, and 12-week player trends from any web browser. Share a unique URL with assistant coaches, team managers, and talent scouts.


WHY COACHES AND TRAINERS CHOOSE OUR APPS

Affordable — no expensive GPS vests or hardware subscriptions. Use the Bluetooth heart rate sensors your athletes already own.

Easy to set up — pair or reallocate sensors in seconds and display sessions on any TV, projector, or monitor.

Built for any environment — SquadHR is designed for indoor fitness classes and studio training, while TeamHR is built for outdoor team sports, tracking up to 50 players across large fields.

Private and secure — all data is stored on-device by default, with optional cloud features fully under your control.

Motivating — putting live effort on the big screen pushes athletes to work harder and stay engaged.


HEART RATE SENSORS

SquadHR and TeamHR work with all iPhone-compatible Bluetooth heart rate sensors. For best results, a chest strap sensor is recommended, as chest straps measure the electrical signals of the heart directly and are more accurate than wrist-based optical sensors, particularly during high-intensity exercise and activities with significant arm movement.

We recommend Polar heart rate sensors for accuracy and reliability, or the popular COOSPO range for a more affordable option. Learn more about heart rate sensors.


NEED HELP?

Visit our Frequently Asked Questions page or contact us at info@trackteam.net.