|Utility:||Basic or Auxiliary|
Sit on floor facing suspension trainer loops in low position. Grasp bottom of loops, then lay supine. Raise legs and place heels in loops with soles contacting handles. Extend one leg out straight, keep other leg bent so knee is pointing up. Place arms on floor off to sides. Lift low back and hips off of floor so one leg is straight with back and other leg bent, so foot of bent leg is close to knee of straight leg.
Simultaneously alternate leg positions by straightening bent leg while bending straight knee. Repeat.
This exercise can be performed on TRXⓇ style suspension trainer. See Suspended Supine Feet Mount/Dismount. Keep low back straight, maintaining approximate height from floor throughout movement. On most popular suspension trainers, keep lower body weight equally distributed on each side to prevent slippage. Some makes of suspension trainers do not have this slack in their design, so one leg can relax momentarily in straight position, while bent side bears most of resistance, allowing for a more dynamic contraction in this specific movement.
Hamstrings seemingly acts as a dynamic stabilizer, since it shortens through knee while it lengthens through hip. However, net contraction actually appears to occur, since hip flexes only about 50%, while knee flexes nearly 100%, allowing hamstring to remain in a mechanically strong position throughout movement. Dorsal flexion of ankle reduces active insufficiency of Gastrocnemius, allowing it to assist in knee flexion.
Apart from Sartorius involvement, flexion of hip is largely passive and is accomplished by eccentric contraction of glutes during concentric contraction of hamstrings, even when lying far away from suspension anchor.
Movement can be made easier by lying closer under anchor of suspension trainer.
Movement can be made more challenging by lying further back, away horizontally from anchor of suspension trainer.