Why does my Health Score sometimes drop if I track an activity?

The health benefits of physical activity are determined by sustained activity over time, not by a single workout. This is calculated through a type of averaging procedure (called exponentially weighted moving average) that looks back at your activities over the past 60 days. Because of this, if a workout you do today consumes less energy than your current average, your score will drop. This means that your score may fluctuate before stabilizing once enough data can be analyzed and averaged.