diff --git a/app.py b/app.py
index 9696d55..b9f4948 100644
--- a/app.py
+++ b/app.py
@@ -316,8 +316,9 @@ def render_users_and_workouts():
 
             # Calculate the workout counts and duration for the current week
             workout_counts_by_week.append(len(weekly_workouts))
-            duration_by_week.append(
-                int(sum([int(w['duration_minutes']) for w in weekly_workouts]))/len(weekly_workouts))
+            if weekly_workouts:
+                duration_by_week.append(
+                    int(sum([int(w['duration_minutes']) for w in weekly_workouts]))/len(weekly_workouts))
 
         workout_counts_sparkline = sparklines.sparklines(
             workout_counts_by_week)