Is it necessary to massage and apply hot compress after exercise to clear lactic acid? ! Scott: Quickly subvert your ideas

It is common to hear people complain after strenuous exercise, such as running a marathon or cycling: "My legs are so tight, I need to get rid of the lactic acid quickly." Therefore, it is common to use ice compresses combined with massage, or even hot baths, in an attempt to speed up the excretion of excess lactic acid from the body. Is lactic acid really the culprit that causes soreness after exercise? Is lactic acid really a waste product that must be excreted? Let’s hear what Dr. Scott has to say.

Is lactic acid really a waste product of the body?

Lactic acid has always been considered the natural enemy of athletes, causing our feet to feel sore the day after running a full marathon. Therefore, many people use hot compresses, gentle exercises, massage, compression leg sleeves and other methods after exercise to accelerate the elimination of lactic acid and eliminate muscle soreness. Are these concepts and methods correct?

Wang Siheng (Dr. Scott), a resident physician in the rehabilitation department of Linkou Chang Gung Memorial Hospital, said that for a long time, lactate has been considered a metabolic waste that lowers the pH value of muscle cells (which means it becomes acidic). It is believed that lactic acid is the main cause of muscle fatigue, muscle soreness, and muscle cramps. However, in 2004, American scholar Robergs put forward a different view: he believed that the simultaneous increase in lactic acid and decrease in pH did not mean that there was a causal relationship between the two. Some evidence shows that lactic acid not only does not make muscles acidic, but can neutralize the acidity. The culprit that causes the pH to drop must be someone else. Therefore, the traditional idea that lactic acid will make muscles acidic may be wrong or incomplete.

Is it necessary to accelerate lactic acid elimination after exercise?

In the past, it was believed that lactic acid was a metabolic waste product produced when the body was forced to use anaerobic respiration due to lack of oxygen, but research in recent years has begun to question this statement. It is currently believed that in addition to lack of oxygen, accelerated glycolysis, reduced lactate clearance rate, and the recruitment of fast-twitch muscle groups are all reasons for the increase in lactate concentration.

Because lactic acid is a product of glycolysis (produced quickly), in the early stages of exercise, due to the increased time efficiency of energy demand, muscles have to quickly produce energy through glycolysis to produce lactic acid, and the blood lactate concentration will rise significantly at this time; however, if the intensity of exercise is not high, after a few minutes, the oxidation of the mitochondria in the muscle fibers will be activated. At this time, the requirements for glycolysis are reduced, and the blood lactate will no longer rise, and may even decrease.

The lactic acid in the muscles and blood disappears quickly after exercise. Massage, stretching, hot baths, and compression leg sleeves more than an hour later will not help eliminate lactic acid.

Lactic acid will return to its pre-exercise concentration within 1 hour.

Dr. Scott said that according to a 2010 study of eight endurance athletes, 60 minutes after exercise, lactate levels in the blood returned to pre-exercise levels, regardless of whether they wore compression leg sleeves or not. In addition, research on cross-country skiing has also found that a 10-minute cool-down can help eliminate lactic acid from muscles.

Based on the above research, we know that lactic acid in muscles and blood disappears quickly after exercise. Massage, stretching, hot baths, and compression leg sleeves more than 1 hour later will not help to eliminate lactic acid.

Dr. Scott also said that the above studies were all conducted on aerobic exercise, and I have not yet seen data on lactic acid clearance after weight training. However, it is speculated that the lactate clearance rates of weight training and aerobic exercise should not differ too much.

The heart, muscles, and liver rely on lactic acid for energy

In the past, scientific concepts have always believed that lactic acid is the product of the human body being forced to "drink poison to quench thirst" due to lack of oxygen, but as the times evolve, this concept has been severely challenged.

Scientists now know clearly that lactic acid is not useless garbage. The heart, muscles, liver, and brain can all use lactic acid as a source of energy.

(Photo taken from Dr. Scott's one-minute fitness class)

In an oxygen-deficient environment, the lactic acid produced by anaerobic metabolism can be used as a raw material for aerobic metabolism in other parts of the body, which is a bit like "your trash is my gold." This "one-stop" industrial chain allows organs throughout the body to participate in metabolism during strenuous exercise. Lactic acid is an important intermediate product and is by no means a source of pollution that needs to be eliminated urgently. So, please don’t misunderstand lactic acid anymore.

※For more information, please see "Dr. Scott's One-Minute Fitness Class"