diff --git a/src/app/lib/storage/workoutStorage.ts b/src/app/lib/storage/workoutStorage.ts
new file mode 100644
index 0000000..bfdb2ea
--- /dev/null
+++ b/src/app/lib/storage/workoutStorage.ts
@@ -0,0 +1,309 @@
+/**
+ * Workout and metrics data persistence layer
+ * Handles saving and retrieving workout data from localStorage
+ */
+
+export interface WorkoutSet {
+  reps: number;
+  weight: number;
+  timestamp: number;
+}
+
+export interface WorkoutSession {
+  id: string;
+  exerciseName: string;
+  date: string;
+  sets: WorkoutSet[];
+  duration: number; // in seconds
+  caloriesBurned: number;
+  notes?: string;
+}
+
+export interface CardioSession {
+  id: string;
+  type: 'running' | 'walking' | 'cycling';
+  date: string;
+  distance: number; // in km
+  duration: number; // in seconds
+  caloriesBurned: number;
+  pace: number; // km/h
+  steps?: number;
+  route?: string;
+}
+
+export interface NutritionLog {
+  id: string;
+  date: string;
+  calories: number;
+  protein: number;
+  carbs: number;
+  fats: number;
+  meals: string[];
+}
+
+export interface UserMetrics {
+  totalWorkouts: number;
+  totalCardioDistance: number;
+  totalCaloriesBurned: number;
+  currentStreak: number;
+  personalRecords: Record<string, number>;
+  lastUpdated: number;
+}
+
+const STORAGE_KEYS = {
+  WORKOUT_SESSIONS: 'fitflow_workout_sessions',
+  CARDIO_SESSIONS: 'fitflow_cardio_sessions',
+  NUTRITION_LOGS: 'fitflow_nutrition_logs',
+  USER_METRICS: 'fitflow_user_metrics',
+};
+
+/**
+ * Save a workout session to localStorage
+ */
+export const saveWorkoutSession = (session: WorkoutSession): void => {
+  if (typeof window === 'undefined') return;
+  
+  try {
+    const sessions = getWorkoutSessions();
+    sessions.push(session);
+    localStorage.setItem(STORAGE_KEYS.WORKOUT_SESSIONS, JSON.stringify(sessions));
+    updateUserMetrics();
+  } catch (error) {
+    console.error('Error saving workout session:', error);
+  }
+};
+
+/**
+ * Get all workout sessions from localStorage
+ */
+export const getWorkoutSessions = (): WorkoutSession[] => {
+  if (typeof window === 'undefined') return [];
+  
+  try {
+    const data = localStorage.getItem(STORAGE_KEYS.WORKOUT_SESSIONS);
+    return data ? JSON.parse(data) : [];
+  } catch (error) {
+    console.error('Error retrieving workout sessions:', error);
+    return [];
+  }
+};
+
+/**
+ * Save a cardio session to localStorage
+ */
+export const saveCardioSession = (session: CardioSession): void => {
+  if (typeof window === 'undefined') return;
+  
+  try {
+    const sessions = getCardioSessions();
+    sessions.push(session);
+    localStorage.setItem(STORAGE_KEYS.CARDIO_SESSIONS, JSON.stringify(sessions));
+    updateUserMetrics();
+  } catch (error) {
+    console.error('Error saving cardio session:', error);
+  }
+};
+
+/**
+ * Get all cardio sessions from localStorage
+ */
+export const getCardioSessions = (): CardioSession[] => {
+  if (typeof window === 'undefined') return [];
+  
+  try {
+    const data = localStorage.getItem(STORAGE_KEYS.CARDIO_SESSIONS);
+    return data ? JSON.parse(data) : [];
+  } catch (error) {
+    console.error('Error retrieving cardio sessions:', error);
+    return [];
+  }
+};
+
+/**
+ * Save a nutrition log to localStorage
+ */
+export const saveNutritionLog = (log: NutritionLog): void => {
+  if (typeof window === 'undefined') return;
+  
+  try {
+    const logs = getNutritionLogs();
+    logs.push(log);
+    localStorage.setItem(STORAGE_KEYS.NUTRITION_LOGS, JSON.stringify(logs));
+    updateUserMetrics();
+  } catch (error) {
+    console.error('Error saving nutrition log:', error);
+  }
+};
+
+/**
+ * Get all nutrition logs from localStorage
+ */
+export const getNutritionLogs = (): NutritionLog[] => {
+  if (typeof window === 'undefined') return [];
+  
+  try {
+    const data = localStorage.getItem(STORAGE_KEYS.NUTRITION_LOGS);
+    return data ? JSON.parse(data) : [];
+  } catch (error) {
+    console.error('Error retrieving nutrition logs:', error);
+    return [];
+  }
+};
+
+/**
+ * Get user metrics from localStorage
+ */
+export const getUserMetrics = (): UserMetrics => {
+  if (typeof window === 'undefined') {
+    return {
+      totalWorkouts: 0,
+      totalCardioDistance: 0,
+      totalCaloriesBurned: 0,
+      currentStreak: 0,
+      personalRecords: {},
+      lastUpdated: Date.now(),
+    };
+  }
+  
+  try {
+    const data = localStorage.getItem(STORAGE_KEYS.USER_METRICS);
+    return data
+      ? JSON.parse(data)
+      : {
+          totalWorkouts: 0,
+          totalCardioDistance: 0,
+          totalCaloriesBurned: 0,
+          currentStreak: 0,
+          personalRecords: {},
+          lastUpdated: Date.now(),
+        };
+  } catch (error) {
+    console.error('Error retrieving user metrics:', error);
+    return {
+      totalWorkouts: 0,
+      totalCardioDistance: 0,
+      totalCaloriesBurned: 0,
+      currentStreak: 0,
+      personalRecords: {},
+      lastUpdated: Date.now(),
+    };
+  }
+};
+
+/**
+ * Update user metrics based on saved sessions
+ */
+export const updateUserMetrics = (): void => {
+  if (typeof window === 'undefined') return;
+  
+  try {
+    const workoutSessions = getWorkoutSessions();
+    const cardioSessions = getCardioSessions();
+    const nutritionLogs = getNutritionLogs();
+
+    let totalWorkouts = workoutSessions.length;
+    let totalCardioDistance = cardioSessions.reduce((sum, session) => sum + session.distance, 0);
+    let totalCaloriesBurned = workoutSessions.reduce((sum, session) => sum + session.caloriesBurned, 0)
+      + cardioSessions.reduce((sum, session) => sum + session.caloriesBurned, 0);
+
+    // Calculate streak (consecutive days with activity)
+    const currentStreak = calculateStreak([...workoutSessions, ...cardioSessions]);
+
+    // Extract personal records from workouts
+    const personalRecords: Record<string, number> = {};
+    workoutSessions.forEach((session) => {
+      const maxWeight = Math.max(...session.sets.map((s) => s.weight));
+      const key = `${session.exerciseName}_pr`;
+      if (!personalRecords[key] || maxWeight > personalRecords[key]) {
+        personalRecords[key] = maxWeight;
+      }
+    });
+
+    const metrics: UserMetrics = {
+      totalWorkouts,
+      totalCardioDistance,
+      totalCaloriesBurned,
+      currentStreak,
+      personalRecords,
+      lastUpdated: Date.now(),
+    };
+
+    localStorage.setItem(STORAGE_KEYS.USER_METRICS, JSON.stringify(metrics));
+  } catch (error) {
+    console.error('Error updating user metrics:', error);
+  }
+};
+
+/**
+ * Calculate consecutive days with activity
+ */
+const calculateStreak = (sessions: Array<WorkoutSession | CardioSession>): number => {
+  if (sessions.length === 0) return 0;
+
+  const dates = sessions.map((session) => new Date(session.date).toDateString()).filter((date, index, self) => self.indexOf(date) === index).sort((a, b) => new Date(b).getTime() - new Date(a).getTime());
+
+  let streak = 1;
+  for (let i = 1; i < dates.length; i++) {
+    const currentDate = new Date(dates[i]);
+    const previousDate = new Date(dates[i - 1]);
+    const diffTime = Math.abs(previousDate.getTime() - currentDate.getTime());
+    const diffDays = Math.ceil(diffTime / (1000 * 60 * 60 * 24));
+
+    if (diffDays === 1) {
+      streak++;
+    } else {
+      break;
+    }
+  }
+
+  return streak;
+};
+
+/**
+ * Clear all stored data
+ */
+export const clearAllData = (): void => {
+  if (typeof window === 'undefined') return;
+  
+  try {
+    localStorage.removeItem(STORAGE_KEYS.WORKOUT_SESSIONS);
+    localStorage.removeItem(STORAGE_KEYS.CARDIO_SESSIONS);
+    localStorage.removeItem(STORAGE_KEYS.NUTRITION_LOGS);
+    localStorage.removeItem(STORAGE_KEYS.USER_METRICS);
+  } catch (error) {
+    console.error('Error clearing data:', error);
+  }
+};
+
+/**
+ * Export data as JSON for backup
+ */
+export const exportData = (): string => {
+  const data = {
+    workouts: getWorkoutSessions(),
+    cardio: getCardioSessions(),
+    nutrition: getNutritionLogs(),
+    metrics: getUserMetrics(),
+    exportDate: new Date().toISOString(),
+  };
+  return JSON.stringify(data, null, 2);
+};
+
+/**
+ * Import data from JSON backup
+ */
+export const importData = (jsonData: string): boolean => {
+  if (typeof window === 'undefined') return false;
+  
+  try {
+    const data = JSON.parse(jsonData);
+    if (data.workouts) localStorage.setItem(STORAGE_KEYS.WORKOUT_SESSIONS, JSON.stringify(data.workouts));
+    if (data.cardio) localStorage.setItem(STORAGE_KEYS.CARDIO_SESSIONS, JSON.stringify(data.cardio));
+    if (data.nutrition) localStorage.setItem(STORAGE_KEYS.NUTRITION_LOGS, JSON.stringify(data.nutrition));
+    if (data.metrics) localStorage.setItem(STORAGE_KEYS.USER_METRICS, JSON.stringify(data.metrics));
+    return true;
+  } catch (error) {
+    console.error('Error importing data:', error);
+    return false;
+  }
+};