If I was forced to choose only one activity with which to complement my swimming, it would unquestionably be yoga. Partly because I enjoy it more than any other. Partly because I feel its combination of mindfulness/awareness and the way it encourages supple strength is ideal for the kind of strength that applies in the water.
Since I'm not currently forced to choose, I also do strength training -- nearly all of it involving instability. E.G. Rather than bench press with a barbell, I do alternate-arm presses with dumbbells (50 lbs each) with my shoulder blades resting on a balance ball. I s-l-o-w-l-y raise right arm while s-l-o-w-l-y lowering left, and vice versa.
I complete this routine in 20 min and do it 2-3x/week immediately after yoga class.
My primary reason for the strength/weight training is its value in countering the effects of aging. And so when the snow starts to fly, I'll be able to shovel for an hour with no ill affects.
Head Coach & Chief Executive Optimist
May your laps be as happy as mine.
My TI Story