HarmonyOS Sports Development: Calculating Calories in Outdoor Sports
Foreword
Accurately calculating calorie expenditure is a must for many fitness enthusiasts and sports enthusiasts during outdoor activities. Whether for weight loss, muscle building, or simply recording the effects of exercise, calorie data holds significant reference value. However, outdoor sports scenarios are complex. How can we achieve precise calorie calculation in the HarmonyOS system? This article will delve into the implementation process of outdoor sports calorie calculation, combining practical development experience. From defining sports types to calorie calculation formulas, and then to data collection and updates, we will uncover the mysteries step by step.
I. Sports Types and MET Values: The "Energy Labels" of Exercise
In calorie calculation, the type of exercise is one of the core factors. Different exercises have varying intensities and thus consume different amounts of energy. We quantify the intensity of exercise through MET (Metabolic Equivalent of Task) values. The higher the MET value, the greater the intensity of the exercise and the more calories burned.
- Exercise Type Enumeration
In the project, we defined an ExerciseType class to store the MET values and corresponding sports scenarios for each type of exercise. For example, walking has a MET value of 3.0, running has a MET value of 8.0, and HIIT (High-Intensity Interval Training) has a MET value as high as 12.0. Below is the code for defining some exercise types:
export class ExerciseType {
public readonly met: number;
public readonly sportType: SportType;
constructor(met: number, sportType: SportType) {
this.met = met;
this.sportType = sportType;
}
static readonly WALKING = new ExerciseType(3.0, SportType.OUTDOOR); // Walking (4km/h)
static readonly RUNNING = new ExerciseType(8.0, SportType.OUTDOOR); // Running (base value)
static readonly HIIT = new ExerciseType(12.0, SportType.INDOOR); // HIIT
}
- The Source and Accuracy of MET Values
These MET values are not made up out of thin air but are based on extensive scientific research and experimental data. However, it is important to note that the MET values provided by AI may have some errors, as the actual intensity of exercise can be influenced by various factors, such as personal physical condition and exercise environment. Therefore, in actual development, we also need to fine-tune the MET values based on user feedback and actual test results to improve the accuracy of the calculations.
II. Calorie Calculation Formula: An Accurate Energy Consumption Model
With the exercise type and MET values in place, the next step is to calculate calorie expenditure based on these data. Our CalorieCalculator class implements a calorie calculation formula based on multiple factors, including distance, elevation changes, and heart rate.
- Basic Calorie Calculation
The basic calorie calculation formula is: Calories burned per kilometer = MET × weight × 0.0175. The core of this formula is the MET value, which reflects the intensity of the exercise. For example, a person weighing 70kg engaging in running with a MET value of 8.0 would burn:
[ 8.0 \times 70 \times 0.0175 = 98 \text{ kcal} ]
- Elevation Change Adjustment
In outdoor sports, the impact of elevation changes on calorie expenditure cannot be ignored. For example, climbing a mountain burns more calories than running on flat ground. We obtain elevation change data through a barometric pressure sensor and make adjustments according to the following formulas:
Extra energy consumed when climbing: Elevation change × weight × 0.0005
Less energy consumed when descending: Elevation change × weight × 0.0005 / 3
- Heart Rate Adjustment
Heart rate is an important indicator of exercise intensity. Although mobile phones currently cannot directly measure heart rate, we can reserve an interface to obtain heart rate data from Bluetooth heart rate devices (such as watches, treadmills) in the future. The formula for adjusting calorie expenditure based on heart rate is:
[ \text{Calories} \times (0.8 + \text{intensity} \times 0.4) ]
where intensity = current heart rate / maximum heart rate.
- Age and Gender Adjustment
Users of different ages and genders have different basal metabolic rates, so there will be differences in calorie expenditure. We further adjust calories through age and gender adjustment factors. For example, women generally have a lower basal metabolic rate than men, so the adjustment factor for women is 0.95, and for men, it is 1.05.
III. Data Collection: The Perfect Combination of Barometric Pressure Sensors and GPS
Accurate data collection is essential for calorie calculation in outdoor sports. We obtain elevation change data through barometric pressure sensors and movement trajectory and distance data through GPS.
- Using Barometric Pressure Sensors
Barometric pressure sensors can monitor changes in air pressure in real time and calculate altitude through a formula. We have implemented a PressureDetectionService class to manage data collection and processing from barometric pressure sensors. Below is the key code:
private barometerCallback = (data: sensor.BarometerResponse) => {
const height = (1 - Math.pow(data.pressure / 1013.25, 0.190284)) * 44307.69;
// Smoothing and altitude change judgment logic...
if (heightDiff > 0) {
this.totalAscent += heightDiff;
} else {
this.totalDescent += Math.abs(heightDiff);
}
};
Through smoothing and altitude change judgment, we can accurately obtain cumulative ascent and descent data.
- Updating GPS Data
In outdoor sports, GPS is a key tool for obtaining movement trajectories. We update GPS points in real time through the RunTracker class and calculate the distance between two points. Below is the key code:
addPoint(latitude: number, longitude: number): number {
const point = new RunPoint(latitude, longitude);
// Obtain elevation data
const pressureService = PressureDetectionService.getInstance();
point.altitude = pressureService.getCurrentAltitude();
point.totalAscent = pressureService.getTotalAscent();
point.totalDescent = pressureService.getTotalDescent();
// Calculate distance and calories
const distance = this.calculateDistance(this.previousPoint, point) * 1000;
const newCalories = CalorieCalculator.calculateCalories(
this.exerciseType,
userProfile.getWeight(),
userProfile.getAge(),
userProfile.getGender(),
0, // Heart rate data not used for now
point.totalAscent - this.previousPoint.totalAscent,
point.totalDescent - this.previousPoint.totalDescent,
distance
);
point.calories = this.previousPoint.calories + newCalories;
this.currentPoint = point;
return this.totalDistance;
}
By updating GPS points and collecting data from barometric pressure sensors, we can calculate calorie expenditure in real time and display it on the page.
IV. The Specificity of Calorie Calculation in Outdoor Sports
Why do we particularly emphasize calorie calculation in outdoor sports? This is because outdoor sports can update data in real time through GPS points, while indoor sports cannot obtain GPS data, and the accuracy of calorie calculation will be greatly reduced. For example, when running on an indoor treadmill, although speed and distance data can be obtained through the treadmill's sensors, elevation change data cannot be obtained, nor can the environmental factors of outdoor running (such as wind resistance, ground friction, etc.) be accurately simulated. Therefore, calorie calculation in outdoor sports is more challenging and more meaningful.
V. Summary and Outlook
Through the close cooperation of defining sports types, calorie calculation formulas, and data collection, we have successfully implemented the function of calorie calculation in outdoor sports. However, this is just the beginning. In the future, we can further optimize the algorithm, for example, by introducing more accurate heart rate data and considering the impact of environmental factors (such as temperature, humidity, etc.) on calorie expenditure.
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