Odds and Ends
One of the quirks of the English language, that makes it a difficult one to learn as an adult, is the fairly large number of words that have the same spelling but different meanings, as well as different pronunciation in some cases.
Take the word eccentric, for example; as an adjective (pronounced ik-‘sen-trik),it is most often used to describe an individual with an unusual or odd personality. (e.g., a word employed by nieces and nephews when talking about their uncle.)
When used in the context of muscle physiology, however, the word eccentric (ee-‘sen-trik) refers to a specific type of contraction of skeletal muscle fibers –specifically, those movements that result in a lengthening of a muscle while it is contracting. An example of this would be if you held a weight in your hand with your elbow bent and then lowered the weight in a controlled manner to a table. As your elbow is straightening, your biceps and other muscles are contracting to control the movement, but they are getting longer at the same time. (The opposite movement – the elbow bending as you lift the weight up – is known as a concentric contraction. If you held the weight in a fixed position, with no movement at the elbow, this would be an isometric contraction.)
As we all know, repetitively exercising a muscle will eventually result in fatigue of that muscle, whether it is done concentrically or eccentrically. The aftereffects of these two types of contractions differ,however. Research has clearly shown that eccentric contractions cause significantly higher levels of microtearing of muscle fibers than either concentric or isometric contractions. Essentially, the muscle is injured to some degree, which results in soreness that is felt within 24 hours, but peaks between 48-72 hours, of the activity. This is known in the exercise physiology world as DOMS (delayed-onset muscle soreness).
Running is one activity that places a certain degree of eccentric stress to the quadriceps muscles in particular. During the initial loading phase on the lower extremity as the foot hits the ground, the knee is flexing approximately 30-40°, before it reverses and straightens before the foot again leaves the ground. While the knee is flexing, the quads are contracting to control that bending movement, but they are lengthening at the same time. As described above, this is an eccentric contraction.
Biking, on the other hand,utilizes the quad muscles in a concentric manner only, so the degree of DOMS is considerably less than after running. I always shake my head every Tour de France when commentators describe that race as being equivalent to running a marathon almost every day for three weeks. I have done a few century (100 mile) bike rides and I can tell you that, while I was plenty tired afterward and my quads felt “dead” the next day, I didn’t have to walk down stairs backwards like I’ve had to after some tough marathons. I could easily have gotten on the bike again the next day without being in pain; I couldn’t say the same for running the day after a marathon.
The degree of injury, and subsequent DOMS, sustained as a result of eccentric exercise is dependent on a couple of factors. First, as expected,would be the intensity and duration of exercise. Anyone who has run a marathon will no doubt have experienced the difference in DOMS of the quadriceps muscles felt after that event compared to a 10k. Moreover,those who have run a hilly marathon – especially a net-downhill marathon such as Boston – will be hurting more a couple of days later than after a flat race such as Marine Corps. A second factor is the protective nature of training; the first experience with DOMS is usually the worst, with training providing an adaptation effect that ensures less soreness and quicker recovery. Such adaptation can last up to six months even if the individual does not exercise at all. Upon return to exercise, the soreness is not as pronounced as the first time.
Millions of dollars are spent every year by athletes seeking a “cure” for DOMS, or at least a quicker recovery. Most popular are the plethora of creams and lotions that purport to eliminate or at least reduce the pain of muscle soreness. These external analgesic substances are known as counter irritants – they produce a heating sensation by chemically irritating the skin, which has the effect of overriding pain signals sent to the brain. While this may lower pain perception, scientific studies of these products have shown that they have no actual heating effect on the muscle tissue and do not actually produce any change in the underlying cause of the soreness, which is the cellular damage from eccentric exercise. The important thing to realize from this information is that you may be causing yourself more harm by using these products if they allow you to exercise by reducing your pain level, in the same way that continuing to run on an injured leg after taking pain medications may be counterproductive.
Massage, on the other hand,may be effective in treating DOMS. I have seen a few studies that produced favorable results indicating that massage can reduce the subjective perception of pain from DOMS, while at the same time not showing any significant change in muscle function or biochemical markers of muscle damage. However, the experimental design of these studies leaves something to be desired, in my opinion, so the jury is still out on whether there really is a benefit from massage. Ultimately though, I don’t think there is a downside to this, so if you feel it helps, by all means go for it.
DOMS is not usually along-term “injury” in the same way tendinitis or a strain/sprain might be, but it should still be respected in the same way when gauging when and at what intensity you should return to running after a hard run or race produces that level of pain. There is no hard and fast rule on when that time might be, but I have always subscribed to the notion that, if you have to walk down stairs backwards, it’s too soon to run.