The frog stretch is a great exercise to stretch out the hamstrings, glutes, and adductors in preparation for heavy leg movements!
Start on the ground in all fours
Spread your knees a bit wider than your hips
Rotate your feet outward and try to have your insteps flat on the ground
Place your forearms flat on the ground
Engage hamstrings and push back towards your feet
Relax and repeat the process, pushing back further each time