Keepy-uppies
4 reps · intermediate
Juggling with the laces: the right foot rolls the ball back with the sole and flicks it up, then keeps it up with three touches on the laces, toes pointed and ankle locked, the ball rising to about waist height; it drops to the floor and the sole stops it. Then the left foot.
A size 5 football and your own bodyweight: no weights.
Faults grow with knee bend and apply to lifts standing on the floor. The fault check flags a knee caving more than 10° inside the line of the toes and a load split beyond 60/40. Knee cave shows best in the front camera.
Femur changes keep standing height fixed by shortening or lengthening the torso. Longer femurs force more forward lean in any squat.
4 reps (a rep is the whole move as shown): light touches, the ball kept close. Ball mastery is practised for touch, balance and coordination, never to failure, so this does not change with your limits.
Level: intermediate. One round counts like light conditioning work: 50 legs points, 35 core points.
Hip flexors (iliopsoas, rectus femoris), tibialis anterior, calves (stabilising the standing foot), gluteus medius (stabilising).
One 3D skeleton drives both views. Segment lengths and widths are Winter's anthropometric ratios of height; segment masses and centre-of-mass positions follow Dempster's data. For free-standing lifts the whole-body angle is found numerically so the combined centre of mass of lifter and load sits over the middle of the foot. Arms and legs use two-link inverse kinematics with a pole direction. Rep timing follows a minimum-jerk profile.
Balance is quasi-static, so ballistic lifts are shown slowed down. Cable pull and pad support forces are not modelled. The spine is one rigid segment and joints have no range-of-motion limits or muscle forces.