diff --git a/mpwo_api/mpwo_api/activities/models.py b/mpwo_api/mpwo_api/activities/models.py
index 4e9a0e4a..e12bebd3 100644
--- a/mpwo_api/mpwo_api/activities/models.py
+++ b/mpwo_api/mpwo_api/activities/models.py
@@ -20,7 +20,8 @@ class Sport(db.Model):
     def serialize(self):
         return {
             'id': self.id,
-            'label': self.label
+            'label': self.label,
+            '_can_be_deleted': len(self.activities) == 0
         }
 
 
diff --git a/mpwo_client/src/components/Admin/generic/AdminDetail.jsx b/mpwo_client/src/components/Admin/generic/AdminDetail.jsx
index 77cb9bd8..6950aa8a 100644
--- a/mpwo_client/src/components/Admin/generic/AdminDetail.jsx
+++ b/mpwo_client/src/components/Admin/generic/AdminDetail.jsx
@@ -45,8 +45,9 @@ class AdminDetail extends React.Component {
                   <form onSubmit={event =>
                    event.preventDefault()}
                   >
-                    { results.map(result => (
-                      Object.keys(result).map(key => (
+                    { Object.keys(results[0])
+                        .filter(key => key.charAt(0) !== '_')
+                        .map(key => (
                         <div className="form-group" key={key}>
                           <label>
                             {key}:
@@ -54,12 +55,12 @@ class AdminDetail extends React.Component {
                               className="form-control input-lg"
                               name={key}
                               readOnly={key === 'id' || !isInEdition}
-                              defaultValue={result[key]}
+                              defaultValue={results[0][key]}
                             />
                           </label>
                         </div>
                       ))
-                    ))}
+                    }
                     {isInEdition ? (
                       <div>
                         <input
@@ -93,7 +94,11 @@ class AdminDetail extends React.Component {
                         <input
                           type="submit"
                           className="btn btn-danger btn-lg btn-block"
+                          disabled={!results[0]._can_be_deleted}
                           onClick={event => onDataDelete(event, target)}
+                          title={results[0]._can_be_deleted
+                            ? ''
+                            : 'Can\'t be deleted, associated data exist'}
                           value="Delete"
                         />
                         <input
diff --git a/mpwo_client/src/components/Admin/generic/AdminPage.jsx b/mpwo_client/src/components/Admin/generic/AdminPage.jsx
index 6cfbb1d4..9b18c621 100644
--- a/mpwo_client/src/components/Admin/generic/AdminPage.jsx
+++ b/mpwo_client/src/components/Admin/generic/AdminPage.jsx
@@ -11,7 +11,9 @@ export default function AdminPage(props) {
   const results = data.data
   const tbKeys = []
   if (results.length > 0) {
-    Object.keys(results[0]).map(key => tbKeys.push(key))
+    Object.keys(results[0])
+      .filter(key => key.charAt(0) !== '_')
+      .map(key => tbKeys.push(key))
   }
   const title = target.charAt(0).toUpperCase() + target.slice(1)
 
@@ -43,7 +45,9 @@ export default function AdminPage(props) {
                     { results.map((result, idx) => (
                       // eslint-disable-next-line react/no-array-index-key
                       <tr key={idx}>
-                        { Object.keys(result).map(key => {
+                        { Object.keys(result)
+                          .filter(key => key.charAt(0) !== '_')
+                          .map(key => {
                           if (key === 'id') {
                             return (
                               <th key={key} scope="row">