|Function:||Leg Ext (Vertical)|
Stand in front of box or platform with feet about shoulder width apart. Raise arms to initiate arm swing.
Swing arms back behind sides while squatting down partially. Rapidly swing arms forward and jump onto platform with knees bent. Immediately jump back down to same position and repeat.
To increase intensity, jump up and down faster or progressively increase platform height. Spinal Flexion will occur when jumping to very high heights. However, Chu & Myer (2014) suggest box heights of only 6' to 12" (15 to 30 cm) with top surface no less than 24" (155 cm) square.