Muscle Aches and Pains
Excluding the ego ache suffered when someone much older passes in the homestretch of a race, runners regularly experience three types of pain: muscle pain during or immediately after running; muscle soreness occurring 24-48 hours later, and muscle cramps.
Pain During or Immediately After Exercise
Track work-outs and other training requiring near-maximal to maximal efforts can lead to muscle pain and burning during or immediately after the run. This is thought to stem from disturbances in calcium metabolism and/or the production of substances in the working muscles such as lactic acid (a by-product of anaerobic metabolism), heat shock proteins, and free radicals.
The pain usually subsides with rest, as the substances are rapidly removed or metabolized. Since pain may result from the presence of free radicals that lead to oxidative damage, it's tempting to consume anti-oxidant supplements as a preventative measure. However, these have not been shown to have beneficial effects on performance. Your best bet is consuming a diet rich in anti-oxidants (vitamins C and E). Some runners may opt for a massage immediately after running. However, scientific evidence indicates that massages have little effect on muscle blood flow, strength recovery, or pain sensation.
Delayed Onset Muscle Soreness (DOMS)
If you train on level roads and then race on a hilly course, your muscles will be sore a day or two later. DOMS occurs in response to novel exercise and usually peaks 24-48 hours after the exercise. It's especially pronounced if the activity involves eccentric contractions. These occur when the muscle lengthens as it contracts. For example, as the weight is lowered during a biceps curl, the muscle is actually lengthening as it contracts to support the weight. When running downhill, the quadriceps muscle group in the front of the thigh contracts eccentrically. Thus DOMS is commonly experienced in quads after running hills. Along with soreness, strength loss and a reduced range of motion (the feeling of stiffness) are common.
The exact causes of DOMS aren't entirely clear. Microscopic muscle damage occurs due to mechanical stresses. There is an inflammatory reaction to the muscle damage. The damage and inflammation can both trigger pain receptors. The soreness is not due to the accumulation of metabolites like lactic acid, since these are rapidly removed from the contracting muscles right after the cessation of exercise. Nor is DOMS caused by muscle spasm.
Treatment for DOMS should include gentle stretching to help restore range of motion.
Nonsteroidal anti-inflammatories (NSAIDS) such as Bayer, Advil and Alleve may lessen the pain. Application of balms, creams, and/or ice as well as submersion in warm water might also provide some temporary relief. Some homeopathic remedies, such as arnica, have recently received attention as treatments. However, there's no scientific evidence they are effective. As DOMS is associated with a loss in muscle strength, athletic performance won't be at peak levels for a few days. If you experience soreness, plan a few days of easy exercise to prevent further muscle damage and to reduce the likelihood of injury.
Muscle Cramps
A cramp is an intense, involuntary contraction of a muscle that usually occurs during or immediately after exercise. Cramps were traditionally thought to stem from fluid or electrolyte imbalances, but this is not always the case. Cramps may even occur following chronic muscle use by individuals who are not sweating, such as musicians. Cramps have also been attributed to extreme environmental conditions or metabolic abnormalities, but again there are examples where this doesn't hold.
A current theory suggests muscle cramps result from fatigue that triggers abnormal neural activity. There's an increase in neural input telling the muscle to contract and a decrease in signals telling the muscle to relax (for aficionados, the signals are from the muscle spindles and golgi tendon organs, respectively). The result is a vigorous contraction of part or all of a muscle. Cramps typically occur towards the end of a marathon, with hill running, or with high intensity running such as racing—conditions that cause muscle fatigue. Runners most prone to cramping are older, have been running for a long time, have a family history of cramping and have poor stretching habits. If you get a cramp, hold the muscle in a stretched position until it subsides. To prevent cramps, stretch regularly, stay well hydrated and maintain good conditioning.
Regeneration
Although exercise can damage muscles, this is followed by regeneration. Moderate pain and soreness signal that muscles are undergoing adaptations to become stronger. Essentially it's a survival mechanism; the body senses you had difficulty running away from a predator (or finishing a race) and thus remodels the working muscles. Then hopefully next time you'll easily get away from the predator (or pass the older runner in the homestretch).
Dr. Carol Torgan is an exercise physiologist and fellow of the American College of Sports Medicine. Although she's not prone to muscle cramps, she is intimately familiar with DOMS.