Your heart is a powerful muscle at the center of your health, improving your fitness. Fitbit’s cardio load is a personalized score to help you understand how hard your heart works during physical activity, empowering you to reach your fitness goals while prioritizing your cardio health. Your target load is a suggested range that can be used to maintain or increase fitness.
Cardio load measures the strain on your cardiovascular system during exercise and daily activities. It considers not only the duration but also the intensity of your efforts, recognizing that higher-intensity exercise places greater demands on your heart. You receive more cardio load for longer and more strenuous activity based on your heart rate.
- Track Your Progress: Track your cardio load over time to check how your fitness is improving and whether you're consistently challenging yourself.
- Optimize Your Training: Use cardio load to guide daily activity levels and intensity, ensuring you're working out at the right intensity to reach your goals, while balancing recovery.
- Avoid Overtraining: Pay attention to trends in your cardio load over time to avoid excessive strain on your body and reduce the risk of overtraining. With target load, Fitbit lets you know if you consistently exceed your recommended limits.
Additional Tips
- Individualized Metric: Remember that cardio load is personalized to you, based on your heart rate during physical activity. This helps ensure your daily target load is challenging enough while still being achievable.
- Varied Activities: Cardio load can be accumulated through a variety of activities that raise your heart rate, including running, cycling, swimming, and even walking.
- Consult with Professionals: If you have concerns about your heart health or training intensity, you should always consult with a healthcare professional or certified trainer.
Cardio load is based on the TRIMP (TRaining IMPulse) model, a well-established method for assessing your training load. This model takes into account your heart rate during activity, as well as factors like your age, resting heart rate, and sex.
Note: Cardio load doesn’t accumulate during swimming exercises because heart rate tracking is disabled.
You start every day with zero cardio load. As your heart rate increases to the light zone and beyond, you'll begin to accumulate cardio load. At midnight, your cardio load resets to zero. There is no practical maximum to the load you can accumulate each day.
The maximum load represented by the end of the cardio load arc in the Fitbit app or on your watch is personalized based on your highest days of cardio load from the past 28 days. As you reach new maximum cardio load levels, you’ll notice this adjust as a result.
- From the Today tab
, tap the Cardio load tile.
- Switch between the tabs at the top of the page to check your load trends over the course of a day, week, month, or year.
- Open the Fitbit Today
- Tap the cardio load tile to check the details on your current cardio load, your target load, a breakdown of what activities have contributed to today’s cardio load, and a graph of your cardio load trend over the week.
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Fitbit Today App |
Fitbit Cardio Load Details |
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What is target load?
Your target load is a suggested cardio load range that you can use to guide your training. Aim to get enough cardio load so that it lands in the target load range each day. It takes into account your fitness level, recent activity, and how recovered your body is, as well as whether you are looking to maintain or improve your cardio fitness level. Think of it as a "sweet spot" for exercise.
Fitbit calculates your target load using several factors:
- Training Target: Your target load is tailored to the fitness target you have set in the Fitbit app to maintain or improve fitness. Selecting “maintain cardio fitness†adjusts your target cardio load to be in line with your average cardio load over the last 4 weeks. Selecting “improve cardio fitness†adjusts your target cardio load to be slightly more than your daily average over the last 4 weeks. Learn more about how this works below.
- Recent activity: Fitbit compares the last week of cardio load with the last month (often called Acute to Chronic Workload Ratio or ACWR) to ensure your target load is appropriate for your current level of training. If you’ve had a lighter last few days of activity, your target load might be higher; while if you’ve taken on more recently, it might be lower to help you maintain balance and prevent overtraining.
- Daily readiness: By looking at how well your body has recovered from previous workouts and the stressors of everyday life, daily readiness plays an important role in determining your target load. If your readiness is low, you’ll receive a lower target load, guiding you to balance rest and recovery. For more information on how daily readiness is calculated, go to What's my daily readiness score in the Fitbit app?
You can achieve your target load by performing physical activities that earn cardio load–these are any activities that raise your heart rate into or above the "light" intensity zone (a personalized zone based on your fitness level and other factors). The more intense your activity, the faster you accrue cardio load and the sooner you reach your target load. Remember that your target load is for the whole day, and not just for a dedicated workout.
- Daily Goal: Aim to accumulate enough cardio load throughout the day to fall within your target load at the end of the day.
- Visual Guide: The Today section in the Fitbit app and watch displays your daily progress toward your target load goal, helping you stay on track.
- Adjustments: Your target load may change over time as your fitness improves or if your activity levels change.
Fitbit measures how active you’ve been over the last 7 days in comparison to how active you have been in the last 4 weeks to determine your training status.
If you take on too much cardio load too quickly, you’re at risk of overtraining. When you're overtrained, your body is constantly fighting to recover. Instead of improving your endurance and stamina, overtraining can lead to a decline in your cardiovascular performance. You might find it harder to maintain your usual pace or distance, and you might feel more easily fatigued.
Conversely, if you stop training for a period of time, you’re at risk of undertraining. While taking breaks is essential, long periods of inactivity can reverse the gains you've made in your cardiovascular fitness. Your heart and lungs become less efficient at delivering oxygen to your muscles. You'll notice that you tire more easily and can't sustain your previous levels of exercise intensity or duration.
The sweet spots between undertraining and overtraining are maintaining or improving. Maintaining means you’re getting a consistent amount of cardio load and regularly reaching your target range. Improving indicates you’re regularly reaching the top of your target range or slightly exceeding it, helping improve your fitness.
Your target load guides you to maintain or improve depending on what goal you select when you onboard. To change your goal:
- From the Today tab in the Fitbit app, tap the Cardio load tile.
- Tap Adjust my target under the Fitness target section.
- Choose Improve cardio fitness or Maintain cardio fitness to select your goal.
- Just-right Training: Your target load takes your current fitness level and recent activity patterns into account. Hitting your target load consistently can help you achieve your fitness goals safely and effectively.
- Injury Prevention: Staying within your target load range can help to prevent overtraining, reducing the risk of injuries and burnout.
- Motivation: Tracking your progress toward your target load can be a great motivator to keep you engaged and excited about your workouts.
Set up cardio load
From the Today tab 
[Optional] To set cardio load as your focus at the top of the Today tab:
- From the Today tab
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- Under Set your focus, swipe through the options and select Build cardio fitness.
- Tap Save.
.Troubleshooting cardio load and target load
- From the Today tab
- Tap the menu icon
Manage data.
- Tap Delete Data
- Select the data range you want to delete.
- Tap Delete.
Your target load guides you to maintain or improve your fitness based on your historic training data (your cardio load accumulated over the last 4 weeks). Training a little more than usual is good for improving fitness, but pushing yourself too hard relative to your 4 week baseline can result in overtraining, which puts excess strain on your system and is counterproductive to your fitness goal. Even if your readiness is high, Fitbit may reduce your target for a day in order to keep you in the training status “sweet spot†(refer to “What is my training status?†above).
Fitbit recommends using readiness and cardio load as tools to help your train smarter, but you should also listen to your body when choosing how much exercise to take on.
- From your watch face, swipe to any tile.
- Long press on the tile to bring up the tile selector menu.
- Tap the + icon to add a tile.
- Scroll vertically to find the Readiness and Load tile and tap to select it.
- Use the arrows to select where the tile should appear among the other tiles on your watch.
- Press the crown to return to your watch face.
- From your watch face, swipe left or right until you reach the Readiness and Load tile.
- Long press on the tile to bring up the tile selector menu.
- Swipe vertically from bottom to top to remove the tile.
- Press the crown to return to your watch face.