I am working on a project with a tableView controller and the detail views contains CMMotionManager.When i open 5 or 6 detailViews all goes well,but after a while the app goes slow and finally crashes.On instruments the only leak is on main.m , also i must say that I'm using ARC and i can't dealloc or realese the instances. Here is the code: First the table view: - (void)viewDidLoad { [super viewDidLoad]; // Do any additional setup after loading the view, typically from a nib. self.title = @"Movement";//Master View Controller title bar UIImage *image = [UIImage imageNamed:@"jg_navibar.png"]; [self.navigationController.navigationBar setBackgroundImage:image forBarMetrics:UIBarMetricsDefault]; //Init the array with data bodypartsMutableArray = [NSMutableArray arrayWithCapacity:26]; BodypartData *part1 = [[BodypartData alloc] init]; part1.bodypartname = @"Shoulder"; part1.movementname = @"Flexion"; part1.fullimageStartingPosition=[UIImage imageNamed:@"2_shoulder_flexion_end_position.jpg"]; part1.fullimageEndedPosition=[UIImage imageNamed:@"2_shoulder_flexion_end_position.jpg"]; part1.thumbimage=[UIImage imageNamed:@"1_shoulder_flexion_landmarks_thumb.jpg"]; [bodypartsMutableArray addObject:part1]; ......... } then the cell: - (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath { UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:@"MyBasicCell"]; BodypartData *part = [self.bodypartsMutableArray objectAtIndex:indexPath.row]; cell.textLabel.text =[NSString stringWithFormat:part.movementname]; cell.detailTextLabel.text =[NSString stringWithFormat:part.bodypartname]; cell.imageView.image =part.thumbimage; return cell; } and the the detailViewdid load: - (void)viewDidLoad { [super viewDidLoad]; // Do any additional setup after loading the view, typically from a nib. // Init motionManager object and set the Update Interval _motionManager = [[CMMotionManager alloc]init]; _motionManager.deviceMotionUpdateInterval=1/60; //60 Hz [_motionManager startGyroUpdates]; if (_motionManager.gyroAvailable) { _motionManager.gyroUpdateInterval = 1.0/60.0; [_motionManager startDeviceMotionUpdatesToQueue:[NSOperationQueue currentQueue] withHandler: ^(CMDeviceMotion *motion, NSError *error) { CMAttitude *attitude = motion.attitude; //Calculation with rotationMatrix m11 = [NSString stringWithFormat:@"%.02f", attitude.rotationMatrix.m11]; m12 = [NSString stringWithFormat:@"%.02f", attitude.rotationMatrix.m12]; m13 = [NSString stringWithFormat:@"%.02f", attitude.rotationMatrix.m13]; ......... }