Different Muscles...WTF?!

Thought I would go off on a little rant here regarding a topic that has bugged me for years. The final straw was drawn following my one climbing outing this summer. Although I now consider myself a full-time recreational bike racer, it was not long ago that I was a climber, Exum guide, all that stuff. I gave that up to maximize my performance in cycling. However, I have a couple of nephews that are kind of crazy about climbing, enthusiasm I am guilty, at least in part, of fostering. These two teenaged go-getters wanted uncle Brian to take them up the Grand Teton this summer. Timing and scheduling issues lead to a two-day window of opportunity two weeks before LOTOJA. I knew I was going to be seriously wrecked after walking downhill for 7,000 vertical feet but I could not resist the pleasure of getting those two guys up on top of the Grand. I figured I could recover in time for the big race.

This brings me to my rant. For several days following the successful summit with Charlie and Will, I WAS wrecked. My quads were torched and I walked funny for about six days. Onlookers would casually comment, I would explain and then they would pop off with the typical, though quite erroneous explanation that I had, "used different muscles." If I had a dime for every time I've heard that... Time to clear the air.

Look, any human propulsion that involves the feet and legs uses the same damn muscles. Unless you are walking on your hands in the circus or pedaling a hand cycle you are propelling yourself using the same muscles every time. That goes for walking, running, cycling, skating, skiing, etc. It's all flexion and extension at the hip and knee and, viola, we go forward, or backward depending which way you are headed. The gluteals, quadriceps, hamstrings, abductors, adductors, external rotators and the gastroc/soleus are all involved to one degree or another and at various rates of contraction to get the job done.

So, why is it then that I can ride my ass off all summer 15-25 hours a week only to be brought to my knees by a little 4 hour walk downhill? Well, the answer lies in the TYPE of muscle contraction. You see, physiologists describe three general types of contraction: isometric, concentric and eccentric.

Isometric involves muscle contraction without movement of the involved limbs. This is achieved by pushing or pulling against an immovable object. The force of contraction can be either light or strong but the angle of the limbs surrounding the involved joint remains constant.

Concentric movements are defined as muscle contraction with muscle shortening. Depending upon the muscle and the movement, a given joint angle can either increase or decrease. For instance, in the bench press when pushing the weight off the chest, the angle at the elbow increases due to the contraction of the triceps leading to straightening of the arm. But the angle at the shoulder decreases due to the action of the pectoralis on the humerus. Now, that is just in the pushing-the-weight-off-the-chest motion.

That brings us to the final type, eccentric contraction. This is the movement that brings the weight down to the chest in the bench press. Here, the supporting muscles are lengthening as they contract. This could also be described as the type of contraction involved with deceleration.

Cycling and swimming involve almost no deceleration and, thus, little to no eccentric contraction. It is very difficult to experience muscle soreness with either of these activities, particularly in trained individuals. Nearly all of a cyclist's training is spent contracting concentrically and the only eccentric motion is getting off the bike at the end of the ride. Ambulation, on the other hand, has a deceleration phase involving eccentric muscle contraction with every step. And this is where the soreness is created.

When researchers want to investigate the physiologic effects of muscle damage they have their subjects run downhill. From a molecular biologic standpoint, the theory is that as a contracting muscle is lengthened during deceleration, there is a microscopic tearing of certain components of the muscle cell called myosin cross-bridges. For a detailed discussion of muscle contraction theory go here. This damage causes local inflammation and pain. The most common explanation I hear for this pain, something I could file under "sub-rant", is that there is an accumulation of lactic acid in the muscles. WRONG!! There are researchers who have spent their considerable careers studying lactic acid metabolism and they will tell you that lactate is gone from the muscle cell almost as fast as it is created and is certainly NOT the culprit in delayed onset muscle soreness.

Like any soft tissue injury, the soreness resolves over several days but can return with repeated bouts of similar movements. However, after several workouts, certain cellular adaptations occur that lessen the subsequent soreness. Over time, simply walking downhill will no longer elicit the dreaded aftermath of near-disabling quadriceps pain. Change the stimulus, however, such as running downhill or adding a heavy pack, and the pain returns until adaptation takes place for the new challenge.

So, next time you get sore in training and someone tells you you are using different muscles or you have lactic acid accumulation, roll your eyes, sigh heavily, pop them upside the head and set them straight. - Brian