I have been taking a hot shower just long enough to soap up and then rinsing and standing in 100% cold water only shower for 3 to 5 minutes, making sure the icy water hits every part of my body for a good 30 seconds or so.
At 50, my body feels like it is not only getting firm and hard, but stronger, a lot stronger.
I do a great deal for my health and understand that all these things have a synergistic action, but I am sold on the cold shower\bath.
Once the weather warms I will transition to cold shower only and try never to use hot water again except in the case of a therapeutic bath.