Is this true dys-
Atlatl designs may include improvements such as thong loops to fit the fingers, the use of flexible shafts, stone balance weights and thinner, highly flexible darts for added power and range. Darts resemble large arrows or thin spears and are typically from 4 to 9 feet in length and 3/8" to 5/8" in diameter.
The design with the finger loops is typical of Basket Maker design, an earlier, but in my opinion, superior design. Instead of being gripped like a hammer, the shaft is held between the first two fingers, and you use the shoulder less, and the arm more.
Who knows? Maybe basket makers had weak shoulders