On really nasty days I go to the gym to get my 25 miles in and I've noticed lately that I spend the same amount of time on the machine at the gym as I do on my bike to cover the same distance, but the machine is a constant uphill grind. I never reach the top of the hill so I never get to coast back down. When I get back on the bike after a couple of days at the gym I seem to fly and never get tired. I feel fortunate that at 73 I might be a little stiff first thing in the morning, but I rarely ever have aches and pains and I attribute my good fortune to many miles on my bikes. Good luck to you,