FrenchFit 

2013, I decided that regular cycling wasn't sufficient for fitness, not a full body workout, so I added running and various gym workouts, and some P90X. I've been fairly committed to the running thing, tracking mileage and pace. (Huge payoff in hill climbing performance.) A few months ago I decided to add a boxing coach, blast that shoulder and core development.

So, before boxing yesterday I decided it was time to get acquainted that the Stepmill machine (rotating stairs), that machine that everyone ignores at the gym. 30 minute work-out and then to boxing, after cleaning up the flop sweat. Of course, the coach decides this session will focus on leg work, so yard ladder work-out between combos. Good fun, surprisingly hard. For a Fredish guy like me, it's entertaining to think of yourself as an 'athlete' at age 61.

This morning I can hardly walk. Totally seizure of the quads and feet. Holy moly, it's going to take 30 minutes of stretching to simply get out the door. I think my point is; just when you think you have reason to be confident about your fitness level you are exposed to something new, and BLAM...you discover all the muscles you haven't been using. Crosstraining rocks; and it keeps you humble.

IBOHUNT

I'll add my 2 cents Canadian...

Running sucks - all 670+ miles with 33,000' of elevation gain of it last year.

YMMV

bigfred 

Last year Mrs. Fred added running to her workouts. As a consequence of my back injury in July I ended up adding swimming. Which, she now, somtimes accompanies me for. She's one regristration form away from being a "multisporter". Then last week we used the community gym for the first time in a couple years. Youch! I'm still sore. I ramped thinks up just a bit too quick by successively picking up heavier weights until I couldn't complete a 10 rep set in each exercise. Probably should have taken it a bit easier than that. I'm just glad that I feel "sore" and not "injured".

HIPCHIP

Muscle training is very specific. What you train for is what the muscles will adapt to, so that is why you cross train. You are using the muscles in a different way than they are used to, so yes, you can easily get sore. Cross training is excellent and will help to reduce injuries when your body is put in a position other than normal, but it sounds like you over did it for the first time, so just back it down a level or two and you'll adapt.

Gonzo Bob

I hear ya. Last year I started curling for the first time and was surprised how strenous the sweeping can be. The cool thing was that after curling for about a month, the nagging ache in my right shoulder that had been limiting my swimming for about a year went away. But the downside was that after about 4 months of curling, I developed some elbow tendonitis. So now I'm back swimming regularly to keep that in check

Carbonfiberboy 

Crosstraining is a very good idea. I use the "stairway to hell" frequently during the winter. My record has been 1.5 hrs in zone 3. That hurt, but that was a few years ago. Now I don't do over an hour at a time. Yesterday I downhill skied fresh "Cascade concrete" in the morning, then did a spin class, then 3 sets of 12 in the weight room. Feel good today. First Winter Training Series SIR ride in the morning. Only 38 miles and 2500', of course in the rain, but a nice warm 45° rain for a change. Our tandem team will attempt to hang with a tandem team that's done PBP twice. We'll see how that goes.

It's doing it regularly that makes the difference. And keeping doing it regularly. I also use exercise for therapy for just about everything. So far, so good.