“…1 ). Twenty-one observational studies included only survey data [ 1 , 5 , [9] , [10] , [11] , [12] , [13] , [14] , [15] , [16] , [17] , [18] , [19] , [20] , [21] , [22] , [23] , [24] , [25] , [26] ], 10 studies evaluated muscle strain using EMG [ [27] , [28] , [29] , [30] , [31] , [32] , [33] , [34] , [35] , [36] ], three studies incorporated both EMG analysis and survey data [ [37] , [38] , [39] ], and six studies used other tools such as pain scales and strain indices [ 1 , [40] , [41] , [42] , [43] , [44] , [45] ]. Of these only one study was a randomized case control design [ 28 ] while all other studies were non-randomized.…”