diff --git a/bodycomposition.go b/bodycomposition.go
index 9f99833..8a02048 100644
--- a/bodycomposition.go
+++ b/bodycomposition.go
@@ -40,8 +40,8 @@ func (bc BodyComposition) writeFitFile(writer io.Writer) error {
 			Weight:            fit.Weight(bc.Weight * 100),
 			PercentFat:        uint16(bc.PercentFat * 100),
 			PercentHydration:  uint16(bc.PercentHydration * 100),
-			BoneMass:          uint16(bc.BoneMass),
-			MuscleMass:        uint16(bc.MuscleMass),
+			BoneMass:          uint16(bc.BoneMass * 100),
+			MuscleMass:        uint16(bc.MuscleMass * 100),
 			VisceralFatRating: uint8(bc.VisceralFatRating),
 			PhysiqueRating:    uint8(bc.PhysiqueRating),
 			MetabolicAge:      uint8(bc.MetabolicAge),
@@ -54,33 +54,19 @@ func (bc BodyComposition) writeFitFile(writer io.Writer) error {
 }
 
 // NewBodyComposition creates a new BodyComposition instance
-func NewBodyComposition(weight, percentFat, percentHydration, percentBone, boneMass, percentMuscle, muscleMass ,visceralFatRating, physiqueRating, metabolicAge, caloriesActiveMet, bmi float64, timestamp int64) BodyComposition {
+func NewBodyComposition(weight, percentFat, percentHydration, boneMass, muscleMass, visceralFatRating, physiqueRating, metabolicAge, caloriesActiveMet, bmi float64, timestamp int64) BodyComposition {
 	ts := time.Now()
 	if timestamp != -1 {
 		ts = time.Unix(timestamp, 0)
 	}
-	var bm float64
-	var mm float64
-
-	if(percentBone != 0 ) {
-		bm = weight * percentBone
-	} else {
-		bm = boneMass * 100
-	}
-
-	if(percentMuscle != 0 ) {
-		mm = weight * percentMuscle
-	} else {
-	    mm = muscleMass * 100
-	}
 
 	return BodyComposition{
 		TimeStamp:         ts,
 		Weight:            weight,
 		PercentFat:        percentFat,
 		PercentHydration:  percentHydration,
-		BoneMass:          bm,
-		MuscleMass:        mm,
+		BoneMass:          boneMass,
+		MuscleMass:        muscleMass,
 		VisceralFatRating: visceralFatRating,
 		PhysiqueRating:    physiqueRating,
 		MetabolicAge:      metabolicAge,
diff --git a/bodycomposition_test.go b/bodycomposition_test.go
index 0b052a0..d489aa6 100644
--- a/bodycomposition_test.go
+++ b/bodycomposition_test.go
@@ -7,7 +7,7 @@ import (
 
 func TestNewBodyCompositionWithDefault(t *testing.T) {
 
-	bc := NewBodyComposition(80, 14.4, 55.2, 37, 2.98, 45.5, 55, 21, 5, 23, 2250, 12.6, -1)
+	bc := NewBodyComposition(80, 14.4, 55.2, 37, 45.5, 21, 5, 23, 2250, 12.6, -1)
 
 	now := time.Now()
 
@@ -26,7 +26,7 @@ func TestNewBodyComposition(t *testing.T) {
 	// set local time to UTC, no matter where executed
 	time.Local = time.UTC
 
-	bc := NewBodyComposition(80, 14.4, 55.2, 37, 2.98, 45.5, 55, 21, 5, 23, 2250, 12.6, timeStamp)
+	bc := NewBodyComposition(80, 14.4, 55.2, 37, 45.5, 21, 5, 23, 2250, 12.6, timeStamp)
 
 	year, month, date := bc.TimeStamp.Date()
 	hour, min, sec := bc.TimeStamp.Clock()
diff --git a/cmd/upload.go b/cmd/upload.go
index 65e56ce..e5abed1 100644
--- a/cmd/upload.go
+++ b/cmd/upload.go
@@ -36,7 +36,32 @@ var uploadCmd = &cobra.Command{
 		calories, _ := flags.GetFloat64("calories")
 		bmi, _ := flags.GetFloat64("bmi")
 
-		bc := bodycomposition.NewBodyComposition(weight, fat, hydration, bone, boneKg, muscle, muscleKg, visceralFat, physiqueRating, metabolicAge, calories, bmi, ts)
+		var boneMass float64
+		var muscleMass float64
+
+		if bone != -1 && boneKg != -1 {
+			cmd.PrintErrf("Cannot provide bone weight in percent and bone mass in kg! Use either of both!")
+			os.Exit(1)
+		}
+
+		if bone != -1 {
+			boneMass = weight * bone / 100
+		} else {
+			boneMass = boneKg
+		}
+
+		if muscle != -1 && muscleKg != -1 {
+			cmd.PrintErrf("Cannot provide muscle weight in percent and muscle mass in kg! Use either of both!")
+			os.Exit(1)
+		}
+
+		if muscle != -1 {
+			muscleMass = weight * muscle / 100
+		} else {
+			muscleMass = muscleKg
+		}
+
+		bc := bodycomposition.NewBodyComposition(weight, fat, hydration, boneMass, muscleMass, visceralFat, physiqueRating, metabolicAge, calories, bmi, ts)
 
 		email, _ := cmd.Flags().GetString("email")
 		password, _ := cmd.Flags().GetString("password")
@@ -71,10 +96,10 @@ func init() {
 	flags.Float64P("weight", "w", -1, "Set your weight in kilograms")
 	flags.Float64P("fat", "f", 0, "Set your fat in percent")
 	flags.Float64("hydration", 0, "Set your hydration in percent")
-	flags.Float64P("bone", "b", 0, "Set your bone mass in percent")
-	flags.Float64("bone-mass", 0, "Set your bone mass in kilograms")
-	flags.Float64P("muscle", "m", 0, "Set your muscle mass in percent")
-	flags.Float64("muscle-mass", 0, "Set your muscle mass in kilograms")
+	flags.Float64P("bone", "b", -1, "Set your bone mass in percent")
+	flags.Float64("bone-mass", -1, "Set your bone mass in kilograms")
+	flags.Float64P("muscle", "m", -1, "Set your muscle mass in percent")
+	flags.Float64("muscle-mass", -1, "Set your muscle mass in kilograms")
 	flags.Float64P("calories", "c", 0, "Set your caloric intake")
 	flags.Float64("visceral-fat", 0, "Set your visceral fat rating (valid values: 1-60)")
 	flags.Float64("metabolic-age", 0, "Set your metabolic age")
diff --git a/uploader_test.go b/uploader_test.go
index 705c8ac..d34b829 100644
--- a/uploader_test.go
+++ b/uploader_test.go
@@ -24,7 +24,7 @@ func TestUploadWeightToGarminIntegration(t *testing.T) {
 		t.Fatalf("Environment variable %s was not set. This is required.", garminPasswordEnvKey)
 	}
 
-	var bc = NewBodyComposition(80, 14.4, 55.2, 37, 2.98, 45.5, 55, 21, 5, 23, 2250, 12.6, -1)
+	bc := NewBodyComposition(80, 14.4, 55.2, 37, 45.5, 21, 5, 23, 2250, 12.6, -1)
 
 	err := Upload(email, passWord, bc)