Sore legs from walking. Really???

Question
Dear Nick,

I come to you because I am totally perplexed.

I'm (almost) 40, and have been exercising most of my life.  I play a lot of tennis and I bike a lot.  I also do squats once a weeks for high reps.

Just this week I began taking up walking, mainly as a way to take breaks from sitting at my PC.  I'm talking REALLY short walks, i.e. 20-30 min which translates to just over 1 mile at my pace.  And my legs are KILLING me after.  I can bike up hills, or go pretty hard for 45-60 min (on the bike), do stairs for 20-30 min, do HIIT with sprints, jog 2-4 miles, etc, and I feel nothing in my legs.  But a 20 min leisurely walk is what's making them ache???  You gotta be friggin kidding!  I'm utterly puzzled. They were sorest right after I get back home and sit to watch TV.  After a little while they don't bother me as much, like right now as I write this to you at my PC.

Could this just be a classic case of getting sore after doing something different/new to the muscle?  I mean it seems totally unlikely  as it seems like a similar enough motion to pedaling on a bike or certainly sprinting or jogging (which I also do).  But I don't know I'm just so totally stumped.

Thanks so much,
James

Answer
James, I admit it is a little surprising, but probably nothing to be worried about. If you were only biking and squatting I wouldn't be too surprised. Walking has an eccentric component that biking doesn't and eccentrics induce more soreness than concentrics (biking almost exclusively uses concentrics). However, sprinting or jogging use both concentric and eccentric phases and you normally do 2-4 miles of those.

Thus, the soreness is likely due to a combination of factors. The motion is a little bit different. While it doesn't seem like it's enough to cause this much soreness that does play a role. Other factors include possibly increased activity, different foods eaten, less quality or quantity of sleep, increased life stress, different foot wear, or different surface that you walked on compared to other activities. While any one of these likely wouldn't cause soreness it seems that a possible combination of these has.

If the gets worse for an unknown reason 4-5 days after you've walked then I recommend seeing a physician. In typical cases the soreness will decrease as you continue a walking program.

Good luck with your physical activity and let me know if I can be of further assistance.