Muscle Soreness

At least one time or another, all of us have experienced muscular soreness, particularly with weight-trianing programs. Generally, two types of muscle soreness are recognized. (1), Acute soreness, and (2) delayed soreness.

Acute Soreness

The reasons for Acute Soreness.

1. Muscular pain is produced during contraction in which the tension generated is great enough to occlude the blood flow to the active muscles (ischemia).

2. Because of the ischemia, metabolic waste products, such as lactic acid and potassium, cannot be removed and thus accumulate to the point of stimulating the pain receptors located in the muscle.

3. The pain continues until either the intensity of the contraction is reduced or the contraction ceases altogether, and blood flow is restored allowing removal of the accumulated waste products.  

Delayed Muscle Soreness

Acute soreness, although often an annoyance, does not pose much of a problem because it is short-lived (acute) and is alleviated when exercise is discontinued. The more serious problem is delayed muscular soreness, which is the pain and soreness that occurs 24 to 48 hours after exercise sessions have stopped.

From experiments designed to induce delayed muscular soreness, it has been found that the degree of soreness is related to the type of muscle contractions performed. What causes delayed muscular soreness and how can it be avoided? The exact cause (or causes) of muscle soreness are not known. However, three different theories have been advanced.

1. The Torn Tissue Theory. The theory proposes that tissue damage, such as the tearing of muscle fibers, could explain muscle soreness. The cellular machinery is temporarily damaged, resulting in poor circulation. Poor circulation forces the metabolities to build up in the cell causing internal pressure. The pressure activates the pain receptor response which signals the nerves to stimulate.

2. The Spasm Theory. In this theory, three stages or action are suggested: (a) exercise causes ischemia within the active muscles; (b) ischemia leads to the accumulation of an unknown “pain substance” (or P substance) that stimulates the pain nerve endings in the muscle; and (c) the pain brings about a reflex muscle-spasm that causes ischemia, and the entire cycle is repeated.

3. The Corrective Tissue Theory. This theory suggest that the connective tissues, including the tendons, are damaged during contraction, thus causing muscular pain.

Studies designed specifically to investigate these theories concluded that delayed muscular soreness is most likely related to disruption of the connective tissue elements in the muscle and tendons. One of the products of breakdown of connective tissue is a substance called hydroxyproline. An increase in the urinary excretion of hydroxproline indicates damage to the connective tissues. Therefore, urinary excretion of hydroxproline was monitored in subjects over several days as follows: on a control day when no exercise was performed, on an exercise day which some of the subjects experienced muscular soreness and some did not, and 24 and 48 hours following exercise. Hydroxproline excretion was higher on the exercise day and after 24 and, particularly 48 hours after exercise in those subjects who had soreness than in those who did not. In addition, a more detailed analysis of the data showed a significant correlation between the day of maximal hydroxproline excretion and the day when the subjects reported their greatest soreness.

The connective tissue theory appears consistent with the findings mentioned of greatest soreness following eccentric contractions. You will recall that during eccentric contractions, the muscle lengthens under tension thus stretching the connective tissue components associated with both the tendon and muscle fibers. In contrast, during concentric contractions (isotonic and isokinetic), the majority of stretch is put on the connective tissues associated with tendons. Furthermore, the tension developed during maximal eccentric contractions is greater than that possible during other types of contractions. This greater tension could possibly cause more damage to the connective tissues.

The following suggestions have been made to prevent muscle soreness.

1. Stretching appears to help not only the prevention of soreness but also the relief of it when present. Stretching exercises should be performed, however, without ballastic bouncing or jerking motions, because this may further damage the connective tissues.

2. A gradual progression in the intensity of exercise usually helps in reducing the possibility of excessive muscular soreness. Such a progression in a weight-training program involves using relatively light weights at the start of the program and then gradually increasing the load as gains in strength are made.

3. It has been proposed that ingestion of 100 milligrams per day of vitamin C (about twice the daily recommended dosage) for a period of 30 days will prevent or at least reduce subsequent muscle soreness. However, the value of consuming such a quantity of vitamin C(asorbic acid) has not been entirely established through scientific experimentation.

Daryl Conant, M.Ed.