Kettlebell swings have to be one of the weirdest exercises I have ever tried. By a long shot. As soon as I woke up the day after my S&S workout, while not particularly stiff, I felt soreness in my triceps and trapezius muscles. Hamstrings got a severe beating, as expected, and most surprisingly even the insides of my thighs (the adductor group of muscles) got a workout. V complained that the soles of his feet had just died.