Adding to the present thread it should be noted that although vertical acceleration of the pelvis produces angular acceleration of swinging limbs so does vertical deceleration .

To understand this imagine a person standing on a raised platform with a rucksack on their back and where the shoulder straps of said rucksack are made of elastic . If our imaginary person now jumps from the platform they will accelerate towards the floor . When they land the body will rapidly decelerate but the rucksack will keep going till stopped by the stretching straps . The straps have been put under tension by the rapid deceleration of the pelvis and spine .

Now imagine a runner , mid stride ,with both feet of the ground and with the pelvis at peak vertical displacement . When the runner comes back down , he/she will meet the ground with a pretensioned (stiff ) subject leg causing deceleration of the pelvis and tension in the swinging leg and arms . This will result in their angular acceleration .

With regard to kicking a football /rugby ball after a run up , at least some of angular momentum generated in the kicking leg seems likely to be generated by the vertical deceleration of the pelvis cause by the standing /support foot meeting the ground after the final approach stride .

Gerry