Always show table headers

Always show table headers

I dynamically fill a reflow table and call "refresh" and "recreate". Once I have a small mobile device display, the content switches to vertical alignment as expected. But the table headers are not visible anymore! How can I make them always visible?
Note: When I manually create a table it works perfect. 

<table data-role="table" id="table" data-mode="reflow" class="ui-responsive table-stroke "> <thead> <tr> <th></th> <th>Tag 1</th> <th>Tag 2</th> <th>Tag 3</th> <th>Tag 4</th> <th>Tag 5</th> <th>Tag 6</th> <th>Tag 7</th> </tr> </thead> <tbody>             //Body content is filled dynamically </tbody> </table>

I dynamically fill a reflow table. Once I have a small mobile device display, the content switches to vertical alignment as expected. But the table headers are not visible anymore! How can I make them always visible?

 <table data-role="table" id="table" data-mode="reflow" class="ui-responsive table-stroke "> <thead> <tr> <th></th> <th>Tag 1</th> <th>Tag 2</th> <th>Tag 3</th> <th>Tag 4</th> <th>Tag 5</th> <th>Tag 6</th> <th>Tag 7</th> </tr> </thead> <tbody> //Body content is filled dynamically </tbody> </table>

 

//Fill table
var headers = ["Ruhe Herzfrequenz", "Schlafqualitaet", "Energielevel", "Selbstverstrauen & Selbstbewusstsein", "Muskelschmerzen",
 "Motivation und Trainingsenthuiasmus", "Einstellung zu Arbeit/Studium/Schule", "Kommunikation mit dem Trainer",
 "Gesundheit"
];
for (var i = 0; i < headers.length; i++) {
 $('tbody', '#table').append("<tr>");
 for (var j = 0; j < 7; j++) {

 if (headers[i] != "Ruhe Herzfrequenz") {
 var str = "";
 var title = "<td>" + headers[i] + "</td>";
 str += "<td><fieldset data-role=\"controlgroup\" data-type=\"horizontal\" id=\"" + headers[i] + j + "\" name=\"" + headers[i] + j + "\" >";
 str += "<input name=\"" + headers[i] + j + "\" id=\"" + headers[i] + j + "-choice-1\" value=\"1\" checked=\"checked\" type=\"radio\">";
 str += "<label for=\"" + headers[i] + j + "-choice-1\">1</label>";
 str += "<input name=\"" + headers[i] + j + "\" id=\"" + headers[i] + j + "-choice-2\" value=\"2\" type=\"radio\">";
 str += "<label for=\"" + headers[i] + j + "-choice-2\">2</label>";
 str += "<input name=\"" + headers[i] + j + "\" id=\"" + headers[i] + j + "-choice-3\" value=\"3\" type=\"radio\">";
 str += "<label for=\"" + headers[i] + j + "-choice-3\">3</label>";
 str += "<input name=\"" + headers[i] + j + "\" id=\"" + headers[i] + j + "-choice-4\" value=\"4\" type=\"radio\">";
 str += "<label for=\"" + headers[i] + j + "-choice-4\">4</label>";
 str += "<input name=\"" + headers[i] + j + "\" id=\"" + headers[i] + j + "-choice-5\" value=\"5\" type=\"radio\">";
 str += "<label for=\"" + headers[i] + j + "-choice-5\">5</label>";
 str += "</fieldset></td>";
 } else {
 var str = "";
 var title = "<td>Ruhe Herzfrequenz<input type=\"number\" id=\"normalHeartRate\" name=\"normalHeartRate\" placeholder=\"Normalwert\" step=\"any\" required\/></td>";
 str += "<td><fieldset data-role=\"controlgroup\" data-type=\"horizontal\" id=\"" + headers[i] + j + "\" name=\"" + headers[i] + j + "\" >";
 str += "<input name=\"" + headers[i] + j + "\" id=\"" + headers[i] + j + "-choice-1\" value=\"1\" checked=\"checked\" type=\"radio\">";
 str += "<label for=\"" + headers[i] + j + "-choice-1\">1</label>";
 str += "<input name=\"" + headers[i] + j + "\" id=\"" + headers[i] + j + "-choice-2\" value=\"2\" type=\"radio\">";
 str += "<label for=\"" + headers[i] + j + "-choice-2\">2</label>";
 str += "<input name=\"" + headers[i] + j + "\" id=\"" + headers[i] + j + "-choice-3\" value=\"3\" type=\"radio\">";
 str += "<label for=\"" + headers[i] + j + "-choice-3\">3</label>";
 str += "<input name=\"" + headers[i] + j + "\" id=\"" + headers[i] + j + "-choice-4\" value=\"4\" type=\"radio\">";
 str += "<label for=\"" + headers[i] + j + "-choice-4\">4</label>";
 str += "</fieldset></td>";
 }

 if (j == 0) {
 $('tbody', '#table').append(title + str);
 } else {
 $('tbody', '#table').append(str);
 }
 }
 $('tbody', '#table').append("</tr>");
}
$("#table").table("refresh");
$("#table").trigger("create");