Video on April 27, 2013
Bodyweight: 80.5 kg (177 lb.)
Resistance: 36 kg (79.2 lb.) kettle bell + 8 lb. (3.6 kg) weighted vest = 39.6 kg (87.2 lb.)
% of bodyweight used as added resistance for strength training: 49.3%
This is an advanced progression in strength and mental training. Once a solid base of training has been established, training for strength (maximal force production) is the next progression. Do not attempt this training until you have completed a preparatory phase of at least 3 months using added resistance in a 8 to 12 repetition range and you feel very comfortable performing the basic movement including ingress and egress from the glute-ham bench and safely positioning the kettle bell. The risk of a strain to the abdominal wall or lumbar spinal hyperextension is high if you do not have proper preparation.
1. The movement: Focus on a a normal speed concentric and a very controlled, slow eccentric with precaution to avoid the inherent risk of lumbar spinal hyperextension. Fully arrest movement at the point of maximal hip flexion (the top of the movement).
2. Visualization: Feel and picture the hip flexors pulling the trunk to the thighs and develop a mind-body connection with their function: feel their engagement through the full range of motion. View this movement as an inverse squat: in the squat you press against the floor with your soles to facilitate maximal use of the hip extensors' pushing force; this movement is the mirror opposite of the squat--pull the insteps against the glute-ham bench foot pads by dorsiflexing the ankles to facilitate maximal engagement of the hip flexors' pulling force.
Theoretically, the best movement for strength training the hip flexors is an inverted squat with added resistance. You could perform it with gravity (inversion) boots while holding a weight but this a movement that is very hard to get into and out of, is very painful where the gravity boots attach, is difficult to do without a spotter (impossible without a spotter for true strength training), and the risk of blacking out is high due to dangerous cerebral blood pressure and poor oxygenation to the brain from the inversion, exertion, and partial breath holding. The next best movement is this movement. There is no superior training to this for increasing the rigidity (stiffness) of the entire trunk outside of gymnastics and this is the best strength movement for the integrated compound engagement of the hip flexors and the entire trunk complex that exists. Abdominals are just a piece of this whole body movement. Oxygen consumption, like squats, is very high. Breathe!
For safety, it is very important with heavy kettle bells to lift the weight to your chest from the side so as to avoid hitting your face and teeth. The video shows the proper technique for positioning the kettle bell.
Note: 6 repetitions were performed in the video. Ideally for strength training the repetition range is 1-3. Therefore, this was too light, probably by 12 lb. to achieve a maximum of 3 repetitions.