simpler to be accurate

src/main.ts

@@ -355,14 +355,10 @@ function renderCharts(activities: Activity[], targetAcwr: number, predictToday:
         }
         endDate.setHours(23, 59, 59, 999);
 
-        // Calculate start date: use longer history for activities with less frequency
-        // Base: 2x chronic period (56 days), extended up to 3x (84 days) for sparse activities
-        const activityFrequency = activities.length / Math.max(1,
-            (endDate.getTime() - activities[0].date.getTime()) / (1000 * 60 * 60 * 24));
-        const multiplier = activityFrequency < 0.2 ? 3 : activityFrequency < 0.5 ? 2.5 : 2;
-
+        // Calculate start date: always go back 56 days (2 x 28 days chronic period)
+        // This ensures we have enough historical data for accurate ACWR calculation
         const startDate = new Date(endDate);
-        startDate.setDate(startDate.getDate() - Math.floor(28 * multiplier));
+        startDate.setDate(startDate.getDate() - 56);
         startDate.setHours(0, 0, 0, 0);
 
         dateRange = {

src/utils/metricAcwr.ts

@@ -334,14 +334,9 @@ export function calculateMetricACWR(
         const chronicAvg = chronicCount > 0 ? chronicSum / 28 : null;
         average28d.push(chronicAvg);
 
-        // Calculate ACWR with smart requirements:
-        // - At the beginning (first 28 days): need at least 8 data points to avoid unrealistic spikes
-        // - After that: calculate whenever both averages are available (minimum 4 data points)
-        // This avoids spikes at the start while ensuring the end is always visible
-        const needsMinimumData = index < 28;
-        const hasEnoughData = needsMinimumData ? chronicCount >= 8 : chronicCount >= 4;
-
-        if (hasEnoughData && acuteAvg !== null && chronicAvg !== null && chronicAvg > 0) {
+        // Calculate ACWR only after we have at least 28 days of data range
+        // This ensures accuracy by having a full chronic period (28 days)
+        if (index >= 27 && acuteAvg !== null && chronicAvg !== null && chronicAvg > 0) {
             acwr.push(acuteAvg / chronicAvg);
         } else {
             acwr.push(null);