A recent study compared backstroke start joint extension sequences (Nara, Ikeda, Shimojo, Sato , Ichikawa, Baba & Shimoyama, 2021). Male and female, adult, national caliber swimmers were tested using three different leg extension protocols:
- extend the hips before the knees,
- extend the hips and knees simultaneously, and
- extend the knees before the hips.
Extending the knees before the hips was significantly slower than the other two options, as shown in the graph below. The graph also shows the angles at the hip and knee when the toes left the wall. The data support the value of extending the hips before the knees.
https://youtu.be/hvf86J3Ytkw