Get value from an array inside an object, scope issue

I'm working on this codepen. Here is the link. http://codepen.io/sweenj7/pen/RPYrrE

I'm having trouble in this paticular area.

 //This prints the entire array 
        $scope.groups[i].items.push("Set " + j + " " +      exercises[i].weightReps );
      //This gets the following error TypeError: Cannot read property '0' of undefined 
        //$scope.groups[i].items.push("Set " + j + " " + exercises[i].weightReps[i] );

I'm trying to get each value of the array to print in the accordion list in it's indexed spot. For some reason I am getting a TypeError that 0 is undefied, but when I have it print the entire array with weightReps instead of weightReps[i or 1,2 etc] it works and prints the entire array. Not sure what the solution is for this.

  angular.module('ionicApp', ['ionic'])

  .controller('MyCtrl', function($scope) {
 $scope.groups = [];

   var Bench = { name:"Bench", StartingSets:"5", Instructions:"lift up arm press to chest", weightSets: ["125","200","200","245","150"], weightReps: ["8","8","10","10","15"] };
   var Curls = { name:"Curls", StartingSets:"3", Instructions:"lift up arm"};
   var Squat = { name:"Squat", StartingSets:"4", Instructions:"Squat Down"};
var  exercises = new Array(); 
exercises[0] = Bench;
exercises[1] = Curls;
exercises[2] = Squat;

 for (var i=0; i < exercises.length; i++) {
for (var key in exercises[i]) {

$scope.groups[i] = {
  name: exercises[i][Object.keys(exercises[i])[0]] + ' - ' + exercises[i][Object.keys(exercises[i])[1]] + " Sets" ,
  items: []
}
};
$scope.groups[i].items.push(exercises[i].Instructions);
for (var j=1; j-1<exercises[i][Object.keys(exercises[i])[1]]; j++) {
  //for (var key in exercises[i]) {
 //   $scope.groups[i].items.push(JSON.stringify(exercises[i]) + '-' + j);
    //$scope.groups[i].items.push(exercises[i].StartingSets + '-' + j);
   //console.log(exercises[i].weightReps[i]);
  //This prints the entire array 
    $scope.groups[i].items.push("Set " + j + " " + exercises[i].weightReps );
  //This gets the following error TypeError: Cannot read property '0' of undefined 
    //$scope.groups[i].items.push("Set " + j + " " + exercises[i].weightReps[i] );

  //$scope.groups[i].items.push(exercises[i][key] + '-' + j);
}
  }

 /*
   * if given group is the selected group, deselect it
   * else, select the given group
   */
  $scope.toggleGroup = function(group) {
    if ($scope.isGroupShown(group)) {
  $scope.shownGroup = null;
} else {
  $scope.shownGroup = group;
}
  };
 $scope.isGroupShown = function(group) {
         return $scope.shownGroup === group;
  };

});