diff --git a/garth/data/hrv.go b/garth/data/hrv.go
new file mode 100644
index 0000000..f36adf2
--- /dev/null
+++ b/garth/data/hrv.go
@@ -0,0 +1,68 @@
+package data
+
+import (
+	"sort"
+	"time"
+
+	"garmin-connect/garth/client"
+)
+
+// HRVSummary represents Heart Rate Variability summary data
+type HRVSummary struct {
+	UserProfilePK     int       `json:"userProfilePk"`
+	CalendarDate      time.Time `json:"calendarDate"`
+	StartTimestampGMT time.Time `json:"startTimestampGmt"`
+	EndTimestampGMT   time.Time `json:"endTimestampGmt"`
+	// Add other fields from Python implementation
+}
+
+// HRVReading represents an individual HRV reading
+type HRVReading struct {
+	Timestamp     int     `json:"timestamp"`
+	StressLevel   int     `json:"stressLevel"`
+	HeartRate     int     `json:"heartRate"`
+	RRInterval    int     `json:"rrInterval"`
+	Status        string  `json:"status"`
+	SignalQuality float64 `json:"signalQuality"`
+}
+
+// HRVData represents complete HRV data
+type HRVData struct {
+	UserProfilePK int          `json:"userProfilePk"`
+	HRVSummary    HRVSummary   `json:"hrvSummary"`
+	HRVReadings   []HRVReading `json:"hrvReadings"`
+	BaseData
+}
+
+// ParseHRVReadings converts values array to structured readings
+func ParseHRVReadings(valuesArray [][]any) []HRVReading {
+	readings := make([]HRVReading, 0)
+	for _, values := range valuesArray {
+		if len(values) < 6 {
+			continue
+		}
+
+		// Extract values with type assertions
+		// Add parsing logic based on Python implementation
+
+		readings = append(readings, HRVReading{
+			// Initialize fields
+		})
+	}
+	sort.Slice(readings, func(i, j int) bool {
+		return readings[i].Timestamp < readings[j].Timestamp
+	})
+	return readings
+}
+
+// Get implements the Data interface for HRVData
+func (h *HRVData) Get(day time.Time, client *client.Client) (any, error) {
+	// Implementation to be added
+	return nil, nil
+}
+
+// List implements the Data interface for concurrent fetching
+func (h *HRVData) List(end time.Time, days int, client *client.Client, maxWorkers int) ([]any, error) {
+	// Implementation to be added
+	return []any{}, nil
+}
diff --git a/garth/data/sleep.go b/garth/data/sleep.go
new file mode 100644
index 0000000..89e0836
--- /dev/null
+++ b/garth/data/sleep.go
@@ -0,0 +1,48 @@
+package data
+
+import (
+	"time"
+
+	"garmin-connect/garth/client"
+)
+
+// SleepScores represents sleep scoring data
+type SleepScores struct {
+	TotalSleepSeconds int `json:"totalSleepSeconds"`
+	SleepScores       []struct {
+		StartTimeGMT time.Time `json:"startTimeGmt"`
+		EndTimeGMT   time.Time `json:"endTimeGmt"`
+		SleepScore   int       `json:"sleepScore"`
+	} `json:"sleepScores"`
+	SleepMovement []SleepMovement `json:"sleepMovement"`
+	// Add other fields from Python implementation
+}
+
+// SleepMovement represents movement during sleep
+type SleepMovement struct {
+	StartGMT      time.Time `json:"startGmt"`
+	EndGMT        time.Time `json:"endGmt"`
+	ActivityLevel int       `json:"activityLevel"`
+}
+
+// DailySleepDTO represents daily sleep data
+type DailySleepDTO struct {
+	UserProfilePK          int         `json:"userProfilePk"`
+	CalendarDate           time.Time   `json:"calendarDate"`
+	SleepStartTimestampGMT time.Time   `json:"sleepStartTimestampGmt"`
+	SleepEndTimestampGMT   time.Time   `json:"sleepEndTimestampGmt"`
+	SleepScores            SleepScores `json:"sleepScores"`
+	BaseData
+}
+
+// Get implements the Data interface for DailySleepDTO
+func (d *DailySleepDTO) Get(day time.Time, client *client.Client) (any, error) {
+	// Implementation to be added
+	return nil, nil
+}
+
+// List implements the Data interface for concurrent fetching
+func (d *DailySleepDTO) List(end time.Time, days int, client *client.Client, maxWorkers int) ([]any, error) {
+	// Implementation to be added
+	return []any{}, nil
+}
diff --git a/garth/data/weight.go b/garth/data/weight.go
new file mode 100644
index 0000000..d91fd60
--- /dev/null
+++ b/garth/data/weight.go
@@ -0,0 +1,39 @@
+package data
+
+import (
+	"errors"
+	"time"
+
+	"garmin-connect/garth/client"
+)
+
+// WeightData represents weight measurement data
+type WeightData struct {
+	UserProfilePK     int       `json:"userProfilePk"`
+	CalendarDate      time.Time `json:"calendarDate"`
+	Timestamp         time.Time `json:"timestamp"`
+	Weight            float64   `json:"weight"` // in kilograms
+	BMI               float64   `json:"bmi"`
+	BodyFatPercentage float64   `json:"bodyFatPercentage"`
+	BaseData
+}
+
+// Validate checks if weight data contains valid values
+func (w *WeightData) Validate() error {
+	if w.Weight <= 0 {
+		return errors.New("invalid weight value")
+	}
+	return nil
+}
+
+// Get implements the Data interface for WeightData
+func (w *WeightData) Get(day time.Time, client *client.Client) (any, error) {
+	// Implementation to be added
+	return nil, nil
+}
+
+// List implements the Data interface for concurrent fetching
+func (w *WeightData) List(end time.Time, days int, client *client.Client, maxWorkers int) ([]any, error) {
+	// Implementation to be added
+	return []any{}, nil
+}